marine ec final
define carrying capacity, limiting factors, intraspecific competition, overlapping generations, age structure, cohort, sex ratio
carrying capacity: maximum population size that can be supported for a particular environment limiting factors: any factor that could inhibit continued growth of a population intraspecific competition: reliance of individuals of the same species on the same limited resource overlapping generations: coexistence of individuals from more than one generation in a population age structure: number of individuals of each age in a population cohort: each age group sex ratio: proportion of individuals of each sex, which can have important effects on population dynamics
describe two major patterns in species richness in the marine environment
1. diversity of coastal species has a latitudinal gradient, with an increase in diversity of coastal organisms from high (the poles) to low (tropics) latitudes. the same pattern is observed at multiple taxonomical placements (genus, family, etc.). the diversity of coastal species, excluding pinnipeds, increases with increasing sea surface temperature, which appears to be the only variable that has significant relationship with diversity. 2. the diversity of oceanic species is highest at mid-latitudes. although the diversity of oceanic species initially increases with increasing SST, it reaches an asymptote at around 15 C
how does the number of trophic levels relate to primary productivity
Areas with limited primary productivity, such as oceanic systems, are temporally stable with little vertical mixing/upwelling (excluding equatorial upwelling). here, the nutrients remain at depths, inhibiting primary productivity. stable environments typically support a greater number of trophic levels, which is why oceanic systems can have 5-7 levels. upwelling systems, on the other hand, are only expected to support 2-3 trophic levels because the water column is unstable due to the vertical movement/mixing. the levels of primary productivity can change seasonally (how long depends on wind/weather patterns). the continental shelves also vary in levels of primary productivity seasonally and spatially (depending on if its temperate or at the poles), making the water column more unstable due to overturn. as a result, these areas only have around 3 trophic levels.
how can sediment grain size impact biota in soft-sediment habitats?
As the grain size of sediment becomes finer, the oxic sediment layer becomes shallower. Well sorted, coarse sand has more spaces in between the grains, so water can flow deeper and provide better oxygen availability. on the other hand, well sorted, fine sand drains more slowly and may not reach as far, limiting oxygen availability. this oxygen availability will dictate which organisms can inhabit the sediment. those with siphons that can stick out of the sediment will have better chances of success in areas of well sorted, fine grains. competition will also be higher in areas right below the surface, as that's where the majority of the oxygen will be.
how can predation increase biodiversity in rocky intertidal communities?
Consumption of competitive dominants by predators can create open spaces for other species, promoting higher species diversity. predation increases diversity of prey, which means that predators with different prey sources can be mutualists via indirect effects. when morula preys on mussels, for example, the emptied space can be taken over by barnacles, which increases the number of acanthia in the habitat.
how do coral reefs have high primary productivity when tropical waters are generally low in primary productivity
Coral reefs are high in primary productivity and serve as the basis of their ecosystem's foodwebs. They do this through their symbiotic relationship with zooxanthellae, where the zooxanthellae allows the corals to undergo photosynthesis and, in turn, the corals provide a protected environment. In addition, corals can also use and recycle nutrients from other habitats, such as seagrass beds.
describe the 4 primary taxa that comprise the phytoplankton
Cyanobacteria (bacteria) -- planktonic cyanobacteria are widespread and are important primary producers in oligotrophic (nutrient-poor) waters. planktonic nitrogen-fixing cyanobacteria fuel the growth of other phytoplankton in oligotrophic regions. photosynthetic and provide oxygen to the water Diatoms (eukaryotes, protista) -- responsible for ~40% of marine and 25% of global primary production. high growth rates relative to other groups of phytoplankton. good competitors for inorganic nutrients. have siliceous frustule with intricate perforations and spines (frustule can sequester carbon and will carry the carbon when it dies and sinks). Coccolithophorids -- nearly spherical and covered with a series of calcium carbonate plates called coccoliths. coccoliths comprise ~1/3 of total calcium carbonate production in the oceans. Will sink like the diatoms/can also be a good carbon sink. if the pH of the ocean decreases, they cannot produce plates and cannot act as carbon sinks. adapted to low-nutrient and high-light conditions. dinoflagellates -- have 2 flagella; one flagellum wraps around a groove along the middle of the cell and the other trails and is used for locomotion. have cell walls have cellulose -- characteristic of macroalgae and land plants. might have gained photosynthetic abilities secondarily. some are able to photosynthesize and ingest prey. some are capable of vertical migration between deeper, nutrient-rich water and shallow waters with ample light (all have different light requirements -- variable)
in the absence of gene flow what are three processes that lead to changes in allele/allele frequencies in a population? describe these three processes
DNA mutations -- these are a change in DNA sequence that results in genetic variance. species with a short life history and rapid reproduction will usually have quick mutation rates, and vice versa for those with long life histories. mutations can either be deleterious (typically fatal-- when an important protein isnt being produced anymore), selectively neutral (no benefit or negative consequence), or beneficial (helpful to the organism in its environment) natural selection & local adaptation -- these processes occur where organisms better adapted for their environment tend to survive and reproduce more successfully than others. In order for natural selection to occur, there must be differential reproduction, variation of traits, and those traits must be inherited. the stickleback, for example, migrated from entirely marine to entirely FW, where it eventually lost most of its plates and invested more energy into swimming faster and becoming more agile. local adaptation occurs when a population of organisms has evolved to become more well-suited to its environment than members of the same species from different environments. pepper moths, for example. genetic drift -- change in the frequency of an allele due to random variation in reproduction among adults. this is very pronounced in small populations, where it can cause a complete loss of alleles. it can also be seen as random fluctuations in allele frequency in different generations, because not all genes are passed on to the next generation in equal proportions as reproduction success differs.
describe 2 largest larval strategies used in estuaries and give examples of each
Estuary retention -- the larvae of some estuarine species remain in the surface waters on incoming tides, being retained in the estuary, where habitat is suitable. mud crabs, for example, will move to the surface during flood tide where they get pushed up the estuary, and then they'll sink during ebb tides Export to continental shelf -- other species want to leave the estuary. blue crabs, for example, spawn in estuaries at high tides and the larvae are transported to neritic waters on an ebbing tide, presumably to avoid estuary predators. these larvae run the chance of returning to the estuary during an incoming tide or being lost to sea
explain, with an example, how diversity changes resource use in competitively structured communities
Griffin et al manipulated the diversity and density of 3 intertidal predatory crabs to examine the effects of predators on the efficiency of resource use. the rates of resource use in multiple species assemblages were greater than that of the best performing single species assemblage regardless of density. the effect of predator diversity was only significant at high predator densities, where competitive interactions were magnified. there was also resource partitioning in polycultures at low and high predator densities. essentially, the loss of predator diversity could decrease efficiency of resource use in the intertidal zones.
explain the ecological roles of herbivores and bioeroders in coral reef communities
Herbivory can prevent macroalgal growth from smothering corals, thereby keeping them healthy. The settlement of macroalgae on corals takes up space and prevents polyps from settling and can also smother other already established corals. A diverse community of herbivores present with complementary foraging patterns is necessary to maintain ecosystem functions on coral reefs. grazers, for example, consume algal turf and macroalgae, preventing the dominance of fast-growing macroalgae. scrapers remove epilithic algae, facilitating the settlement and growth of coralline algae and corals. bioerosion is the removal of calcium carbonate substrate by other organisms, such as fish feeding on hard corals. While this can be destructive, the erosion also provides living and hiding crevices for reef species. bioerosion also produces tons of fine-grained sediments for the ocean floor. Bioeroders, such as urchins and parrotfish, strip what they want off of the sediment and pass coral skeleton in tiny pieces, which can be important in building sandy bottoms.
explain larval dispersal and settlement in general
If larvae are planktonic, they are carried in random directions by wind-driven currents. These currents can either carry them to an optimal environment or can take them to an unsuitable habitat, and it mostly depends on the strength of flow. Their dispersal potential depends on the amount of time spent as plankton. Larvae that are benthic have very little to no dispersal potential, as they settle right where they are fertilized.
why did the loss of sea otters in alaska have a different impact on function than the loss of sea otters in california?
In Alaska, the loss of sea otters caused a shift from kelp beds to urchin barrens, altering the system from high productivity to low productivity. however, the loss of sea otters in california did not cause a shift to urchin barrens. this is because california had a higher diversity of predators with complementary diets that compensated for the decline of otters. this functional diversity allows the ecosystem to sustain itself even with the decline of an important predator, because there were other predators present to fill in the function. the higher diversity of a predator species in californian waters buffers kelp forests from the effects of the loss of an apex predator, preventing barrens and deforestation. a single predatory species can have a disproportionate effect on ecosystem function. higher biodiversity of predators buffers against trophic cascades from a loss of a single species, since relationships are weaker, which confers greater environmental stability. in linear trophic systems, such as with the sea otters in alaska, predator diversity increases the strength of trophic cascades, since there are strong relationships between predator and prey. when predators are generalists, predator diversity doesn't affect herbivory.
give an example of a trophic cascade in a kelp forest in the eastern pacific
In Aleutian Island Kelp Forests, sea urchins are the only ecologically important consumer of kelp and sea otters are the most important predators of sea urchins (aka keystone species). sea otters were hunted by european traders for their pelts in the late 1700s and were on the brink of extinction by the 1800s. the low abundance of sea otters led to an increased abundance of sea urchins, ultimately leading to a collapse of kelp forests and leaving behind barrens. in 1922, the international fur seal treaty provided protection to the sea otters from further commercial harvest. however, the sea urchin barrens persisted to the 1970s. in the 70s, there was an increase in the abundance of otters, leading to a decreased abundance of sea urchins that allowed the kelp forests to return. however, in 1990, the sea otter populations crashed again due to transient orcas prey switching to sea otters.
give one detailed example of a top-down control in a saltmarsh
In Hudson Bay Canada, snow geese bred in saltmarshes where they would graze on saltmarsh grasses. this, initially, had a positive effect on marsh productivity because they would fertilize the sediment. However, in the 80s-90s, wintering snow geese in North America fed in heavily fertilized fields, which led to a tripling in the number of snow geese arriving at the marshes in the summer to breed. The abundance of snow geese overwhelmed the system and destroyed more than 200,000 hectares of marsh habitat, leaving the marsh too small to have its original function and impact.
give an example of how predators can be mutualistic while consuming different prey in rocky intertidal communities
In a given rocky intertidal community, snails could be feeding on mussels, Acanthina feed on barnacles, and limpets feed on macroalgae. mussels, typically, will outcompete barnacles and macroalgae for space. if snails are present and feeding on mussels, then they won't be able to outcompete the other organisms, and the snails could clear up space on the substrate for more barnacles to grow. the more barnacles there are, the more acanthia there will be.
how can abiotic and biotic factors trigger kelp deforestation and cause phase shifts in habitat?
Kelp deforestation can result from physiological stress, disease, or herbivory. Abiotic drivers are common at low latitudes, while herbivory is the most significant trigger at mid latitudes (i.e. temperature, if currents aren't flowing like they're supposed to/weaker water might not reach them, lack of nutrients can cause deforestation and disease). warming waters can also proliferate disease and cause diseases in places they've never been before. Deforestation triggered by sea urchin herbivory often results in a barren community devoid of kelp, and instead, characterized by calcified coralline algae. these barrens are created due to phase shifts, or dramatic changes in habitat
how do abiotic requirements of kelp impact their global distribution?
Kelp forests require a hard substrate that their holdfast can attach to, proper temperature (between 5-20 C), sufficient light, and nutrients to grow. if the temperature becomes too warm, the kelp will become physiologically stressed, which can worsen if nutrients are low. Warm temperatures also tend to inhibit growth. Kelp forests also tend to do well in areas of moderate to high water flow, which can help with gas exchange and nutrient uptake. As a result, kelp forests can be found in temperate and subtropical latitudes. there is some distribution in the tropics due to the surface current directions. Gyres move clockwise in the NH and counterclockwise in the SH, so the cold arctic water gets pulled down in NH in the east, so kelp can be found on eastern sides of the oceans. Same in the SH. they can also be found in areas of upwelling. however, some kelps are well adapted to low light and cold waters in polar latitudes. they can store carbon and nitrogen in their tissues in the winter when they're available, and when the sun comes out in summer they can grow rapidly.
explain the costs and benefits of larval dispersal
Mortality is extremely high during larval phases due to predation and the potential of settling in unsuitable habitats. Gregarious settlers may not be able to find adult species, currents could carry it too far or not far enough, and they could end up in the wrong habitats. The risk is high, so they must have good benefits. Larval dispersal can spread young over a variety of habitats-- decreasing competition/avoiding overcrowding and increasing chance of some young surviving. Or, if something happens to the original habitat, the young that got carried away while be fine. Dispersal also increases the geographic spread, and the range of invertebrates with planktonic dispersal is usually greater than those without
how can "fear" of predators induce trophic cascades? give an example of this in a coral reef community
Prey can choose different (but less risky) habitats, spend more time hiding, or not venture far from shelter. Rasher et al (2017) studied the non-consumptive (fear) effects of large predators in fijian coral reef ecosystem. in this habitat, predators/large fish were inhibited from traveling over the reef top at low tide, and had to wait until high tide to be able to travel across. the abundances of browsers and grazers were high in the lagoons at low tide, but they declined at high tide, suggesting a migration pattern in and out of hiding. The hiding/vacating activity resulted in reduced foraging and grazing during periods of increased predation risk. they also found that these "fear effects" propagate downward, as the macroalgae biomass on the reeftop was 20x greater where predators were virtually absent.
what are the differences and similarities between life in the rocky vs soft intertidal environments?
Rocky and soft intertidal environments face many of the same stressors, such as temperature, desiccation, and oxygen. However, soft-sediment habitats are constantly in motion through eroding and building, while rocky intertidal environments are mostly stable. In terms of organisms, most of the soft sediment organisms are burrowing, while rocky intertidal organisms are epifaunal.
what are the chemical properties of seawater?
Salinity: total amount of salt dissolved in seawater. open ocean ranges from 33 - 37. sea surface salinity varies spatially and temporally D.O. : amount of free, non-compound oxygen in water. varies spatially and seasonally -- tends to be higher in surface waters where gas exchange occurs, deeper waters tend to have lower oxygen
explain why you can find an urchin barren adjacent to a thriving kelp bed
Sea urchins usually can't cope with high flows/wave energy at shallow depths. Kelp beds persist on shallow, wave-impacted waters while barrens are in adjacent, deeper waters (this is especially seen in Maine). in the deeper waters where urchins are present, kelp forest-barren phase shifts result from overgrazing of the urchins (in addition to disease and the abiotic environment).
how does seagrass modify water flow and how does this impact biota? what are seagrass bed "edge effects"?
Seagrass leaves, rhizomes, and roots decrease the water turbulence and modify currents and waves. this can, ultimately, impact the dispersal of larvae being carried by the currents. in areas of moderate density of seagrass, the water flow will be interrupted by blades that will catch some of the larvae and cause it to settle down into the beds. dense seagrass beds will result in a settlement shadow, where larval settlement is higher at seagrass bed edges because of reduced water flow. the settlement of larvae attracts first level consumers, which can benefit from greater recruitment and food availability at the edges. however, predators (such as pipefish) tend to also congregate around the edges.
describe 5 physical types of boundaries in the pelagic environment
Temperature-- differences can be seen spatially and temporally. vertical and horizontal oceanic boundaries are sharpest where strong discontinuities in the physical environment are present, such as with temperature and nutrients. ocean sea surfaces vary with latitude on large spatial scales and can range from -1.6 C to more than 30 C. Temperature has strong influences in larval development, and in determining species ranges (due to thermal thresholds). it can also play roles on smaller spatial scales, such as with metabolic rate, growth, development, duration of incubation and time spent in larvae, and consumption rate (as it gets warmer, organisms will eat more) Stratification-- stratification is a vertical structure in the water column that is a seasonal feature in many temperate pelagic habitats. this typically separates surface waters and deep waters. surface waters are exposed to a lot of light, oxygen, and are usually warm. however, they're typically poor in nutrients, since they're used up by phytoplankton. deeper waters are cold and have limited light and oxygen, but are nutrient rich. stratification creates heterogeneity within pelagic habitats. Fronts-- fronts are narrow zones of strong horizontal gradients in temperature, salinity, nutrients, or primary productivity. usually see that fronts have regions of enhanced primary production and because of this fish will spawn close to fronts so that the larvae are retained by physical features, placing offspring in an ideal position for rapid development (in areas with warm waters and high primary productivity). as a result, predatory species (fish, seabirds, marine mammals, etc.) aggregate, forage, or migrate along these fronts, creating hotspots of high biological activity. Upwelling-- upwelling can be seasonal or permanent. in equatorial upwelling, due to Eckmann transport, water is pushed at a 90 degree angle from what the trade winds are traveling at (which is parallel to the equator). as a result, water is pushed in opposite directions from the equator, and deep water rises to fill the gaps. this brings high levels of nutrients to the surface, and coupled with the exposure to sunlight, creates high areas of primary productivity. as long as the wind is blowing, there will be upwelling (typically is-- trade winds). Mola mola, for example, were found to migrate seasonally between northern California Bight and sites off Baja, California (~800 km). it was revealed that they were following upwelling cold water fronts, which supported primary productivity . the mola mola prey (zooplankton, tunicates, and jellyfish) are abundant at these upwelling fronts Eddies -- typically circular currents of water moving in a direction that is different from that of the main current. eddies create pockets of warm water within cold water currents. this is popular in the eastern US due to the instability of the gulf stream current, creating sharp thermal differences in small spatial scales. these eddies can also create hotspots of organisms and provide enhanced feeding conditions for larvae. however, they can negatively impact recruitment of shelf-spawning species by displacing them to an unsuitable habitat offshore where they could die. phytoplankton are found in the edges of eddies and bring in consumer that attract higher-level predators.
what limits the geographic ranges of marine species?
Temperature-- temperatures beyond the edge of ranges are physiologically stressful, as it affects digestion, respiration, heartrate, development, etc. in addition, temperatures beyond the edge of ranges may interfere with reproduction. for example, there is usually a minimum temperature required for the production of gametes and larval development. some species, such as barramundi, are stenothermal, meaning they are only capable of surviving within a narrow temperature range. dispersal limitations, or if you can get to a suitable habitat and successfully establish (successful establishment depends on what species are there and what is their abundance). Oceanographic conditions
what are the physical properties of seawater?
Temperature: sea surface temperature varies with latitude because of differences in solar input. temp also varies with depth (temp and density have inverse relationship, cold water more dense than warm water). 3 characteristic layers: surface layer (up to 200 m deep, mixed by wind and waves/currents. most influenced by sst), intermediate layer (below the surface layer up to 1.5 km deep, defined by permanent thermocline), deep layer (uniformly cold water, typically <4 C). Light penetration: light intensity decreases with increasing depth. loss of color discrimination at depths of 30 -- 50 m. blue penetrates best. depends on turbidity of water Pressure: increases exponentially with depth; 1 atm for every 10 m in depth. as pressure increases, gasses compress
describe low marsh ecology with examples of plant-plant and plant-animal facilitation
The lower boundaries of species zones are usually set by physical stressors, such as longer exposure to saltwater and anoxic/waterlogged soils. plant-plant and plant-animal positive interactions can be important in reducing these stressors. They do this through plant-plant facilitation, where plant neighbors stabilize the sediment and aerate oxygen-poor sediments with their aerenchyma (spongy tissue in roots that form air channels that fill with oxygen during photosynthesis to diffuse into their roots and oxygenate soils). if plants are established somewhere, its easier for other plants to establish in the same area. there can also be plant-animal facilitation, such as with saltmarsh grasses and bivalves. the bivalves attach to the grasses to help stabilize the sediment. bivalves can also enhance nitrogen availability via filter feeding.
what is the evidence for bottom up and top down control in pelagic communities? how does this differ from benthic communities?
The way pelagic communities are studied is very different from benthic communities in that the empirical data for experiments on benthic communities involves manipulated experiments. this is harder in the pelagic environments, where you can't place things in cages, so the bulk of data for these experiments is correlation data. bottom-up control: areas and time periods with the highest primary production support the highest nekton biomass. here, there is a clear correlation between areas with chlorophyll and the subsequent presence of nekton. in the north sea, for example, cod recruitment is affected by the mean size, seasonal timing, and abundance of their prey (copepods), during their larval phase. if the copepods are high in abundance, cod recruitment will be high. however, if timing of high copepod abundance does not coincide with feeding larval stage of cod, recruitment will decline. top-down control is a new concept in pelagic communities, in contrast to benthic habitats. the evidence for this largely comes from the effects of overfishing of large-bodied predators. in the NW atlantic, the collapse of cod and other large bodied predators influenced abundances at lower trophic levels. the decrease of predatory fish increased planktivorous fish due to predation release, causing a decrease in zooplankton and an increase in phytoplankton blooms. this community restructuring changed the way we thought about pelagic communities, as it was initially believed that marine ecosystems were large enough to buffer the effects of top-down control and prevent cascades. shifts in state from fish to jellyfish dominance is also associated with top-down trophic cascades in pelagic communities. jellyfish dominated states associated with heavy fishing pressures that cause top-down cascades, so the secondary production that was consumed by fish (that are no longer there) cause an increase in blooms.
what is a typical pattern of species zonation in a saltmarsh
Zonation in sandy intertidal habitats are less obvious than rocky intertidal habitats because of the abundance of burrowing organisms. In the upper intertidal habitat, you'll typically find fiddler crabs, isopods, etc. In the lower intertidal, there are more biological interactions (mid and lower intertidal -- more polychaetes and clams). burrowing invertebrates compete for space, resulting in vertical stratification of species within the sediment. S. alterniflora is found closest to the water, as it has the highest salinity tolerance. the upper limits are set by competition, and the lower limits are set by physical stress. the most physiological stressful environment for plant species is the lower intertidal (upper intertidal for marine species).
how does high biodiversity buffer against a variable environment and invasive species?
a more diverse assemblage is more likely to include a species that can be productive under different environmental conditions, making it more likely to maintain function in a variable environment, a concept referred to as the insurance hypothesis. this ensures ecosystems against a decline in function because many species provide a guarantee that some can still fill a certain role even if the environment changes. higher diversity also leads to a more complete use of available niches, which can buffer against invasive species. invasive species can potentially cause major changes in the community that change the trophic ecology, species relationships, and other aspects of marine ecosystems. in order for an invasive species to be successful, it must be able to find food and reproduce very quickly. an invasive species may have a greater chance of success in a habitat with low biodiversity because of increased resource/niche availability (most invasive species are generalists and will eat anything) and the absence of predators. the energy release hypothesis proposes that the abundance and/or impact of invasive/exotic species is related to the absence of natural enemies in the introduced range, compared to the native range. once established, these species can further reduce biodiversity, disrupt food chains, and upset ecosystem but eating juveniles
explain bottom-up and top-down control of phytoplankton
abundant nutrients (with light) create a bloom, resulting in bottom-up control. productivity of all size classes increases, but smaller phytoplankton are controlled by grazers early on, while larger phytoplankton continue to accumulate while their grazers are temporarily rare, since they take longer to reproduce. bloom ceases due to nutrient consumption and a significant proportion of the larger phytoplankton species sink from photic zone grazing can also result in phytoplankton community changes in the absence of variation in resources. phytoplankton often exhibit boom-bust dynamics that result in large blooms, leading to pulses in ecosystem processes (supporting food webs). this was long thought to be due to bottom-up control due to resource limitation, although grazers have strong influence on phytoplankton community. two mechanisms of top-down control: keystone predator, where two competitors can co-exist if the better competitor is more susceptible to predations (i.e. "kill the winner") and specialist enemies -- each species of phytoplankton is regulated by a distinct predator. this can also maintain phytoplankton diversity.
what factors influence zonation in saltmarshes at lower vs higher latitudes
at warmer, lower latitudes, physical stress can set both upper and lower boundaries of marsh plants. high rates of evaporation leaves behind salty soils, and hypersaline soils in the high marsh can limit the growth and survival of plants. at cooler, northern latitudes, upper boundaries of species zones are usually set by competition. competition between plants is higher in the high marsh and plants that are not good competitors are displaced to more physically stressful habitats (i.e. the low marsh). inferior competitors have more tolerance to a more stressful environment where better competitors cannot exist.
what is bergmann's rule and what are the 2 hypothesis for this pattern?
bergmann's rule states that an increase in body size with latitude is a pattern for many pelagic species and communities. the original hypothesis for this rule was correlated with thermoregulation. however, it is also seen in zooplankton, which negates that idea. the two hypotheses for this pattern are: temperature-size rule, which states that ectotherms tend to mature at relatively small body sizes when raised under warm conditions and mature at a larger body size in colder waters. in cold water environments, organisms tend to have a slow metabolism, slow growth, and long life expectancy. their life history traits support larger body sizes food availability -- clines in food availability drive patterns in body size. pelagic areas of higher primary productivity support communities with organisms with larger average body sizes. in the north, there are big blooms of productivity, so larger bodied organisms will be found in northern latitudes. this has substantial implications for nutrient recycling through food webs and the transfer of energy to higher trophic levels in terms of body size with northern vs southern latitudes. while bergmann's rule held true in the past, more recent studies (from 1991-1994) reveal that the rule no longer applies. as you increase in latitude, body size no longer increases. this could be due to an ecosystem shift since there are fewer larger predators present due to overfishing. this altered the food web and trophic structures with the higher abundances of small-bodied individuals.
describe bottom-up and top-down trophic systems
bottom-up control: ecosystems in which the environment and availability of primary producers (plants and phytoplankton) regulate species at higher trophic levels. where a decrease in nutrients leads to the decline of phytoplankton which, in turn, causes a decline in zooplankton --> planktivores decline --> carnivores decline top-down control: ecosystems in which higher trophic levels regulate species at a lower trophic level. here, the planktivores decline as the carnivores increase. the decline in planktivores also leads to an increase in zooplankton, which declines the phytoplankton. this type of control has not been studied as extensively as bottom-up control, as it is difficult to study due to human influences (take out top predators - interfere with natural trophic systems)
define and give examples of commensalism and mutualism
commensalism is the interaction in which one individual benefits while the other is neither helped nor harmed. this usually occurs when you have a big host and a tiny host, such as the barnacles on whales. this is subject to change (i.e. if barnacle density becomes too high on whales or sea turtles) mutualism is the symbiotic interaction where both or all individuals benefit from the relationship. the degree of dependency can be facultative or obligate. obligate-obligate mutualism is when both need it to survive. facultative-facultative is when both benefit but can live without it. obligate-facultative is when one needs it, the other benefits but can do without it (coral and zooxanthellae)
describe two processes by which diversity can influence ecosystem function via increased resource use
complementarity effects: resource partitioning (in competitive communities) leads to increased total resource use. more diverse assemblages use a defined set of resources more completely or use a broader set of resources. there are positive relationships between diversity of a species and of total resource use based on competition and carrying capacity. selection effects: dominance by species with particular traits affect ecosystem processes. as the number of species increases, the probability of including a more productive species increases. more diverse assemblage is more likely to include a species that is more productive. can also produce negative effect if dominant species is less productive. complementarity and positive selection effects enhance the magnitude of resource capture, regardless of trophic level, which makes more effective use of resources and therefore, energy
describe major marine topographic features
continental shelf: very shallow (up to 400 m). makes up 8% of the ocean, but they it is the biologically richest part of the ocean. estuaries, mangroves, all found here continental slope: edge of the continent, often surrounded by canyons deep sea floor : aka abyssal plain -- nearly flat and has trenches up to 11 km deep
what is the match-mismatch hypothesis?
degree of temporal overlap between spring phytoplankton blooms and the production of the feeding larval stages of fish species determines the numerical strength of a cohort and its influence on higher trophic levels. this can be observed with the puffins in northern norway. a match occurs when the timing of availability of nutrients/sunlight cause a phytoplankton bloom, which causes a zooplankton bloom. here, the timing of max production of zooplankton strongly overlaps with peak recruitment of herring larvae. the larvae that are present will survive due to the abundance of nutrients and grow into adult fish, which makes the predatory birds (puffins) also successful. the opposite occurs with a mismatch. here, there are no larvae present to feed on large amounts of zooplankton. or, if the larvae are present in an environment where the prey is not, then many larvae will die, and there will be decreased success in puffins. the puffin breeding success depends on ample supply of fish at time of chick rearing, and the success of fish depends on supply of their food at critical times (e.g. larvae and juveniles)
what are density-dependent and density-independent factors? give an example of how each can limit population growth
density-dependent factor -- these factors intensify as the population increases in size. they reduce the growth rate by increasing death rate or decreasing reproduction, such as predation, competition, and disease. increases in the population density result in an increase in intraspecific competition. gannets, for example, must compete for suitable nesting sites on rocky cliffs to increase success of their offspring survivorship. density-independent factor -- density-independent factors are unrelated to population size, and they affect the same percentage of individuals regardless of population density. These include anthropogenic activities, and weather/storms. the red tide in Florida, for example, impacts the central nervous system of fishes and kills species regardless of population size.
what is ecosystem function and what is the relationship between biodiversity and function?
ecosystem functions are the biological, geochemical, and physical processes and components that occur in an ecosystem. the loss of biodiversity will reduce the ecosystem function and stability of the system, which can allow disturbances to negatively impact biodiversity and function even more. although it known that the functioning of marine ecosystems is related to biodiversity, the effects of biodiversity loss on function in these systems are not completely understood. the diversity should increase ecosystem function (1) in competitive communities where niche partitioning influences co-existence and (2) when competitively dominant species make the strongest positive contribution to productivity. there are two processes by which diversity can influence ecosystem: complementarity effects and selection effects
describe 4 ecosystem services of the marine environment
ecosystem services are the direct or indirect contributions that ecosystems make to the well-being of humans 1. primary production - provides oxygen (phytoplankton), supporting biomass, higher trophic levels, using carbon. 2. habitats that support biota, some of which are harvested - dissipate waves and stabilize sediment, preventing erosion (saltmarsh grass, mangroves). 3. recreation, tourism 4. carbon sequestration - ocean is a big carbon sink. coccolithophorids and diatoms act as carbon sink. trap it and remove it from system. 5. climate regulation - global currents. warm water moving to poles, cold waters moving to tropics. conveyor belt regulates temperature, lots of concern its breaking down (known that it is slowing)
explain how environmental heterogeneity, planktonic dispersal, and plasticity/local adaptation in the marine environment violate the assumptions of the abundant-center hypothesis
environmental heterogeneity: one of the assumptions of the hypothesis is that environmental factors driving fitness vary along gradual gradients. however, in marine environments, the gradient are not gradual (especially around coastlines). there are often sharp changes in temperature and a very sharp gradient in productivity. if there is a pocket of upwelling, there will be an increase of productivity in that area that will attract other species. so, in the area of upwelling, there will be a center of high abundance with nothing 100 kilometers away. the same can apply to spatial changes. planktonic dispersal: the hypothesis makes the assumption that habitat favorability is correlated with abundance due to reproductive success of adults. essentially, suggests that high reproductive output leads to higher recruitment in a good habitat. however, many marine species have planktonic larvae. this leads their planktonic dispersal to decouple habitat favorability, reproductive output, and abundance. so, even if the species is in their favored habitat, the larvae is being pushed out. local abundance will not always be directly linked to reproductive output. in most cases, the larvae ends in an unsuitable habitat and dies. plasticity and local adaptation: the final assumption of the hypothesis is that populations of a species respond in a similar way to a given set of environmental conditions. however, isolated marine populations can respond differently to environmental conditions (such as investing into growth and maturing later). organisms may exhibit phenotypical plasticity, which is the ability of one genotype to produce more than one phenotype in different environments. for example, species at cooler temperatures near the poleward edge of their range may grow more slowly and have lower reproductive output. tide pool copepods from the northern california coast show less heat tolerance than species in mexico.
explain why not all species will change their distribution successfully as climate changes
even if species have the (genetic) capacity to adapt to environmental changes, can they do it fast enough to keep up with abiotic conditions? this process usually takes a long time, longer than the rate that climate change is occurring. corals, for example, display variation in thermal tolerance, suggesting some capacity to cope with warming temps. however, the generation times of many corals are on the order of decades, requiring many centuries for populations to recover. communities would cease to exist if their foundation species fails to adapt or shift their distributions, such as corals and seagrasses. as climate change progresses, there will be new winners and losers. if an appropriate habitat doesn't exist, establishment is unlikely to happen, especially if there is a lag. it's inevitable that some species will fail to adapt or shift their distribution and will go extinct. in fact, more than 100 species are predicted to be lost in the next few decades
what is fitness? how can organisms increase fitness?
fitness is the measure of an organism's ability to survive and reproduce. organisms have finite resources that allow for growth, survival, and reproduction, and ideal fitness is species-specific. they can increase their fitness by undergoing trade-offs between these categories in a way that optimizes their chances for success. if they have low fecundity, for example, they can invest in high levels of parental care to ensure young survival.
how can genetic diversity impact ecosystem function
genetic diversity can mediate community and ecosystem-level functions and may allow a population to adapt/cope with fluctuating conditions and disturbances. the portfolio effect proposes that diversification stabilizes ecosystem function. genetic diversity produces different responses to environments/disturbances and stabilizes/preserves ecosystem function. this, ultimately, minimizes the risk involved with environmental variation. the seagrass Zostera marina, for example, is a foundation species in shallow marine habitats in the northern hemisphere. z. marina plots with more genotypes produce more shoots, including after an intense grazing event by geese. genotypic diversity in seagrass buffers against biomass loss during disturbances such as heat waves or intense grazing events. genetic diversity enhances resistance and resilience, allowing species to better recover from a loss.
describe overyielding and nontransgressive overyielding
greater ecosystem function by a mixed species assemblage than by the average of a single-species assemblage is called overyielding. essentially, an ecosystem with lots of species will have a greater function. if ecosystem function of a mixed species assemblage does not exceed that of the best single-species assemblage, then it is called nontransgressive overyielding. Some species will do better than others, so here, a monoculture's function would exceed that of a polyculture with 10 species, for example.
what are 2 ways herbivores can influence biodiversity
herbivory can increase biodiversity in coral reefs. one of the biggest threats to corals is being smothered by macroalgae. reefs in the caribbean are especially susceptible to this, as they are in decline due to stressors and bleaching events (both of which make space available for macroalgae to come in). the reef can't sustain the fish and biodiversity will decrease. the belize barrier reef, however, is the healthiest coral reef with high biodiversity due to the herbivorous sea urchins. there are 2-4 sea urchins per square meters on this reef. the high nutrient load going into the water, which cause huge blooms of primary productivity, are taken in by the sea urchins to keep the coral healthy and clean on the other hand, herbivory can also lead to overgrazing in some habitats, which decreases biodiversity. in kelp forests, sea urchins consume macroalgae, which takes away structural components of the habitat and can leave the environment barren. so, it must be kept under control to prevent the loss of the habitat.
how can biodiversity determine how energy and nutrients flow through food webs
horizontal diversity (within a trophic level) can enhance or reduce energy transfer across trophic levels. sea otters in alaska vs california example
what are deep sea hydrothermal vents and what is the basis of life in such an extreme habitat?
hydrothermal vents are fissures in the Earth's surface where tectonic plates are moving. here, the molten rock heats seawater in cracks and "smoking chimneys" expel super-heated water up to 400 C, rich in various melts and dissolved sulfides. this creates a gradient of environments in the otherwise flat deep-sea and serves as a biodiversity hotspot. the food webs in hydrothermal vents are supported primarily by chemosynthesis. bacteria and archaea derive energy from the oxidation of sulfide and make it into usable products able to be used by other organisms. these microbes can live on the surface of sediments, in the water column, or in the tissues of other organisms (symbiotically), such as with the tube worms. large tube worms have no mouth, digestive tract, or anus. they do have symbiotic bacteria living in their trophosome that provide it with nutrients (organic carbon). in turn, the worm provides the bacteria with a protected environment.
why does an increase in nutrients benefit large-celled phytoplankton over small-celled phytoplankton
increased nutrients benefit large-celled phytoplankton due to size structured grazing. phytoplankton of different sizes are consumed by different grazers. phytoplankton of different sizes are consumed by grazers with different population dynamic time scales. small phytoplankton are grazed by small zooplankton that reproduce very quickly, allowing for tight coupling between production and consumption. 75% of primary production is grazed by microzooplankton (e.g. ciliates) in oligotrophic tropical and subtropical waters. larger phytoplankton are grazed by mesozooplankton (e.g. copepods) that have longer generation times (lag between availability of phytoplankton and consumption). low supply of nutrients initially support small sized phytoplankton (too low to support grazers). as nutrient supply increases, biomass of small phytoplankton begins to increase, increase in nutrients allows grazers to come in. eventually phytoplankton levels off, biomass begins to get controlled by top-down control (getting eaten)
what is the relationship between increasing sea temperature and metabolism and growth?
increasing temperatures affect enzymatic function, metabolism, growth, photosynthesis, feeding, development, and life span of organisms. with warmer temperatures, you can expect to see an increase in metabolic rates and growth. this can cause an increase in the rate of larval development, causing earlier development and therefore settlement, which could disrupt connectivity between populations. metabolism increases with increasing water temperature, but only to a point, which beyond it declines, and it can be impacted by very small changes in temperature.
what are potential outcomes of range shifts and changes in seasonal timing?
increasing water temperatures will place a proportion of the global population of a species outside of its tolerance limits, so part of a population of every species will find itself in conditions it will not do well in, and areas previously outside of its tolerance limits could become suitable. as a result, we would see changes in the geographic ranges of species. shifts in species ranges will result in novel combinations of species are the next 100+ years. prey will be introduced to new predators, there will be changes in competitive dominants, altered roles of mutualisms and facilitations, and changes in strengths of species interactions. changes are also occurring in the seasonal patterns of temperature, which affects timing of seasonal events, known as phenology. warming temperatures of spring are arriving earlier in the year, so there has been an expected increase in phytoplankton at the poles since they'll have a longer growth period. this change in bloom periods could result in more mismatches with peak recruitment of their predators, decreasing the success of some species, an effect that could be propagated up the food chain.
what are 3 types of competition, with examples.
interferences competition occurs where there is an individual directly altering the resource-attaining behavior of other individuals. this can occur where an organism is trying to defend its territory or access to its mate exploitative competition is when individuals interact indirectly as they compete for common resources. in this competition, the two organisms are not fighting each other as in interference competition. this can be seen in areas where fish and urchins are trying to eat the same kelp. apparent competition: two individuals that do not directly compete for resources affect each other indirectly by being prey of the same predator. if predator eats one prey, the other prey in safe.
define: locus, allele, allele frequency, panmictic population, population structure, natural selection, local adaptation, genetic drift
locus: fixed position on a chromosome allele: one or more alternative forms of a gene that arise by mutation and are found at the same locus on a chromosome allele frequency: relative frequency of an allele at a particular locus in a population; used to describe amount of variation at a particular locus panmictic population: all individuals are equally likely to mate with another randomly chosen individual as any other in the population population structure: presence of differences in allele frequencies between populations; populations are genetically distinct natural selection: process where organisms better adapted to their environment tend to survive and produce more offspring local adaptation: when a population of organisms has evolved to become more well-suited to its environment than members of the same species from different environments genetic drift: change in the frequency of an allele due to random variation in reproduction among adults
define metapopulation, residency, and philopatry
metapopulation: group of spatially separated populations that are connected at some level residency: when organisms remain in their natal sites their whole lives philopatry: when organisms return to their natal sites to reproduce
what are the different zones of the marine environment?
neritic waters: above the continental shelf oceanic waters: beyond continental shelf epipelagic: 0-200 m; photic zone as light can penetrate down this layer mesopelagic: 200 -- 1000 m bathypelagic: down to 4 km abyssopelagic: down to 6 km
explain and provide an example of non-consumptive effects of predators in rocky intertidal communities
non-consumptive effects occur when the presence of a predator alters the behavior, physiology, or life history of its surviving prey. this can be done through inducible defenses, which are a type of phenotypic plasticity where organisms modify their morphology, behavior, chemical composition in response to risk of predation. barnacles, for example, exhibit different morphs depending on if a predator is present. if predatory snails are around, barnacles will be in their bent morph because it makes it harder to eat. the morph requires stimulus from the predator, so if peak barnacle recruitment occurs at the time of year when the predator is not present, then the bent morph will not occur.
how can ocean acidification and increasing sea temperatures impact predator-prey or herbivore-producer interactions?
ocean acidification will affect predator-prey relationships involving species with calcified structures used in defense. mussels, for example, will have reduced growth and lower survival in low pH environments, while echinoderms do better in some regard. the pisaster sea star, which responds well to ocean acidification, can more easily feed on mussels that have thinner shells due to low pH. kelp and sea urchins: kelps (photosynthetic) are expected to do well in low pH and ore CO2, so they could potentially expand. sea urchins are also expected to do better. however, an increase in water temps could proliferate disease and stress the kelp. increased temps: can lead to more intense predator-prey and herbivore-producer interactions as consumption needs increase. it can strengthen consumer control of resources, so things that are bottom-up control could switch to top-down control. the interactions also become very intense and strong, so the herbivores could potentially overgraze and the trophic structure of the community/population dynamics would be altered. increasing the water temperature from 14 C to 28 C increases oxygen demand and metabolism of the green sea urchin, causing a 4X increase in grazing.
what are pelagic mobile links and what ecological purpose do they serve?
pelagic mobile links are species with high motility that connect disparate habitats via long-distance migrations for feeding and reproduction. these migrations can be driven by oceanic processes, thermal tolerance, and shifts in prey distribution. many species, for example, will get triggered into northward migration during seasonal warming of waters. the changes in temperature could be related to thermal tolerance and that where there's a change in temp, there's likely to also be a change in prey distribution. other predatory species following chlorophyll A density, which is related to primary productivity. understanding mobile links can allow scientists to predict when and where individual species are likely to be, which can be used to preserve biodiversity of hotspots and conservation.
what are the dominant primary producers in the marine environment and what limits primary production?
phytoplankton are the dominant primary producers in the environment and make up more than 95% of photosynthesis in the oceans. they serve as the basis of food webs (which differs from terrestrial systems). the intensity/penetration of light and availability of nutrients limits primary production.
describe the relationship between gene flow and population structure
populations that interbreed with each other will have significant gene flow and share the same alleles/allele frequencies. there will be no genetic distinction between the two populations and therefore, they have no population structure. however, populations that do no interbreed with each other will have no gene flow and be genetically distinct, so they will have high levels of population structure.
how do predators impact their prey, with examples
predators can over-exploit their prey. for example, nudibranchs and sponge cover. the sponges will decrease with a high number of nudibranchs. shortly after there is a decline in the sponges, the nudibranch population will also begin to decrease (as they no longer have their food source). predatory-prey relationships can also be complex and adaptations on both sides result in an "evolutionary arms race". for example, sea lilies developed to ability to move due to stressors such as overcrowding, physical disturbance, and predation. in a 2005 video that depicted sea lilies moving, there were always sea urchins behind them-- which could suggest that they were running away from predators. to support this, fragments of sea lily stalks that pass undigested through sea urchins often have bite marks that match the size and shape of an urchin's "mouth". the frequency of bite marks on motile crinoids were lower than those on sessile crinoids, a pattern that also supports that motility was a predator escape strategy. examination of 5000+ crinoid stalk fossils show that urchins preyed on crinoids 225 mya.
how does the extinction of rare species and higher trophic level species impact function
rare species are only going to be present in systems with high biodiversity. when rare species are more likely to go extinct, the effects of biodiversity loss on ecosystem function are different from the effects of random diversity loss. in non-random macroalgae assemblages, for example, function is greater in diverse assemblages that include rare species, compared to a random assemblage. there are increases in diversity and function when you had nonrandom assemblages that included rare species. so, there is a difference in function depending on whether or not your assemblage included rare species. if rare species are extinct, there is low diversity, since they're the first to go. there is a disproportionate loss of species at higher trophic levels due to overharvest. these larger bodied species going extinct have larger habitat requirements and life history characteristics that support slow reproduction and therefore, slow response to disturbances, making them more likely to face extinction. loss of higher trophic levels reduces the diversity of strongly interacting predators, changing the topology of food webs via trophic skew. when you lose consumers, you get incomplete resource use. when you lose predators, you get species invasions, or tons of first level consumers, skewing trophic proportions.
how do seagrass communities influence other communities
seagrass beds can strongly influence and be influenced by adjacent marine and terrestrial habitats through trophic transfer. around 15% net primary productivity (can be up to 50%) is exported through detritus. this can be important in communities that lack their own primary producers and rely on seagrass to support their foodwebs. dead seagrass that has washed ashore can also provide nutrients for intertidal communities and enhance coastal vegetation. mobile organisms that use the seagrasses at some point of their life can transfer seagrass production through active export of seagrass-derived biomass. this is seen in habitats such as saltmarshes, mangroves, coral and oysters reefs, etc. in fact, fish abundance and richness is higher on coral reefs with adjacent seagrass meadows (often bc fish use beds as nursery areas). one experiment revealed that 32 of 36 fish species in the indo-pacific used seagrass beds as nurseries. 70% of these species, including the humphead wrasse, were absent or in low abundance on coral reefs without adjacent seagrass beds
explain why seagrasses are considered foundation species
seagrasses are considered foundation species because they provide structural habitat and refuge to organisms. The beds of seagrasses are known to host higher animal densities than other soft-sediment communities. these seagrasses allow the abundance and growth/survival of many species to be higher than in a structurally simple habitat. clams, for example, tend to grow larger and faster in seagrass beds.
describe the environmental (abiotic) requirements for seagrass beds
seagrasses require soft sediments in sheltered, shallow and tropical/temperate waters with good light penetration. fast currents could create stress and damage leaves and also cause erosion, which the soft sediment is susceptible to. seagrasses grow along the continental shelf in the photic zone, and the distribution in terms of depth is light limited.
how do primary producers tolerate or deter herbivores
some macroalgae tolerate herbivory by quick growth or by having spores/vegetative parts that survive gut passage. kelp, for example, can grow up to 14 cm per day. other macroalgae can deter herbivores through physical/chemical defenses. calcareous green algae produce deposits of calcium carbonate that is inedible to vast majority of herbivores. these organisms produce new tissue at night when most fish are not out feeding. some brown algae is able to make large amounts of sulfuric acid (18-20% dry body weight is just this acid). macroalgae can also use chemical cues to detect when certain herbivore is around and they can upregulate the right chemical defense depending on which herbivore is present. despite these defenses, fish can evolve/adapt to certain chemicals.
describe 3 types of measures of biodiversity
species diversity -- can be measured by species richness, which is the number of species in an area, although that is difficult to quantify. species diversity is highest in the tropics, since species usually originate and accumulate in the tropics (high speciation rate). biodiversity is significantly correlated with temperature, and warmer temps result in organisms having higher metabolic rates, which promote speciation. there is also environmental stability (able to survive and reproduce under environmental conditions that are stable year-round) and habitat diversity (mangroves, seagrasses, and coral reefs are all found in the tropics). genetic diversity -- genetic diversity is genetic variability within a species. this genetic variation can lead to variation in phenotypes, which can be advantageous, disadvantageous, or neutral. variation is the underlying mechanism for evolution within a species, as low genetic diversity results in a limited ability to adapt to changes. high genetic diversity allows a species to adapt a changing environment by some individuals being better suited to local conditions, such as corals that are more heat resistant and can withstand warming sea temperatures. functional diversity -- the diversity of trait values of a species including habitat preference, feeding mode, morphology, trophic position, feeding mechanism. redundant traits of different species can exist within an ecosystem, and several different mesopredators can be playing same functional role. species-rich ecosystems tend to have high functional diversity. there is an emphasis placed on the role of species, rather than taxonomic identity, in ecosystems by explaining how traits are influenced by biotic and abiotic factors (less on how many species there are)
why is species diversity highest in the tropics?
species diversity is highest in the tropics, since species usually originate and accumulate in the tropics (high speciation rate). biodiversity is significantly correlated with temperature, and warmer temps result in organisms having higher metabolic rates, which promote speciation. there is also environmental stability (able to survive and reproduce under environmental conditions that are stable year-round) and habitat diversity (mangroves, seagrasses, and coral reefs are all found in the tropics).
explain the ecological impacts of ocean acidification
species have differences in their ability to tolerate/buffer against changes in pH, with both negative and positive responses. seagrasses are expected to benefit from increases in water column CO2, since they otherwise could be limited in carbon in terms of their growth. Seagrasses can also use dissolved carbon and help buffer against pH changes. however, ocean acidification can have a negative impact on the survival, calcification, growth, development, and abundance of marine organisms. lower pH impacts species with shells, or skeletons made of calcium carbonate because lower pH dissolves calcium carbonate. the bicarbonate ions present will more eagerly interact with other ions and prevent growth in organisms, such as coral. bivalve larvae are also showing decreased survival growth, and metamorphosis.
how do species interactions vary in intensity depending on environmental stress, differences in population densities, and recruitment?
species interactions vary in intensity depending on environmental stress by exhibiting higher competition in intermediate conditions in which multiple species can survive. C. fragilis and S. balanoides, for example. C. fragilis prefer warm waters, and are found in habitats as far north as cape cod. S. balanoides prefer cooler water and are found as far south as north carolina. s. balanoides are very good competitors, and there are areas along the atlantic coast that show overlap of their ranges, which would result in higher interaction/competition. species interactions can also vary in intensity depending on differences in population densities, such as predator and prey densities. keystone species, such as the Pisaster ochraceus sea star, are imperative in populations. these sea stars feed on the california mussel, which would normally be a competitive dominant species. in one experiment, where the sea stars were taken out of the habitat, the mussels outcompeted other species and the lower edge of the mussel zone extended. thus, the presence/absence of a certain predator could decrease the competition between other species. finally, species interactions vary depending on recruitment. the diet of dog whelks, for example, changes depending where they are geographically. in southern california, they prey on california mussels by drilling through their thick shells. in northern california, they prey on acorn barnacles and blue mussels, both of which have thinner shells. these separate populations of dog whelks have different drilling capacities. the ability to drill into thicker shells allows the dog whelks to succeed in a region where recruitment of alternative prey (i.e. barnacles and blue mussels) is low.
describe the types and patterns of tides
spring tide: when the sun, moon, and earth are aligned with each other. greatest tidal range. neap tide: minimal tide range, occurs in 1st and 3rd quarter moons. full lunar cycle is 24 hours and 50 minutes. the extent of the tide is determined by the difference in gravitation attraction on either side of the earth, relative to the moon and the sun
why do environments support different numbers of trophic levels
temporal stability of the environment: continental shelves of temperate latitudes, poles, and upwelling systems have high, but seasonably variable (unstable) levels of primary productivity. as a result, these unstable systems support fewer trophic levels stability of the water column: stable water column systems (open ocean) have low, but steady levels of primary productivity, supporting complex food webs with more trophic levels (at least 5). phytoplankton -> herbivorous zooplankton --> carnivorous zooplankton --> small fish --> large fish --> birds, sharks, marine mammals
what is the abundant center hypothesis and how applicable is it to marine species? why?
the abundant center hypothesis states that species are most abundant at the center of their range and less abundant at the edges. this hypothesis came about from studying terrestrial plants and birds, and although it is true for some marine organisms as well, it only occurs in about 1/3 of species. this is because marine environments are under the influence of environmental heterogeneity, planktonic dispersal, and plasticity/local adaptation. the range of most marine species are likely to contain cool spots where a species is relatively rare, interspersed with hot spots of favorable conditions
describe the advantage/disadvantage of being an herbivore
the advantage of being an herbivore is that food can be relatively easy to find and cannot escape, so there is no catch and handle of prey (which is ultimately energy saving). the disadvantage is that primary producers tend to be difficult to digest (which could require specialized gut microbes) and more may be needed to provide adequate energy. large marine herbivores must invest considerable amount of time feeding
explain the concept of a carrying capacity
the carrying capacity, represented by K, is the maximum population size that can be supported by a particular environment. This is a property of the environment and varies spatially and temporally with the abundance of limiting resources.
provide an example of resource partitioning
the diets of 20 butterfly fish on the great barrier reef were studied to determine how they were able to coexist. the butterfly fish had divided into around four clusters that were separated based on what their dominant dietary item was. 3-7 species in each cluster were further divided. some fed on hard corals, some soft corals, some fed on anything, and others did not feed on coral at all. there was also a divide in the different size ranges of prey.
why is the distribution of pelagic organisms patchy?
the distribution of organisms in the pelagic is patchy and depends on physical processes such as temperature, light, and nutrients (all of which vary spatially, temporally, and seasonally). light and nutrients influence primary production and phytoplankton, which form the basis of food webs. distribution can also depend on structures, which is typically something floating in the pelagic. these structures create microhabitats and can be made of debris, trees, kelp, or anything that can float and support life. biological interactions also influence the distribution of organisms.
explain reciprocal facilitation between seagrasses and bivalves
the seagrass bed will provide shelter for the bivalve. this bivalve, in turn, will provide the sediment with nutrients through their deposition, as well as improving the water clarity through filter feeding on phytoplankton (which increases light penetration/intensity and promotes photosynthesis). seagrass beds allow for the abundance and growth/survival of many species to be greater than in structurally simple habitats. clams, for example, tend to grow larger and faster in seagrass beds.
describe type II and type III functional responses. what determines the type of response?
type II functional response occurs when the rate of prey consumption by predator increases as prey density increases, and eventually levels off to some plateau. the search rate is fairly constant regardless of prey density. type III occurs in a similar fashion as type II in that it eventually flattens and prey density will not cause increase of prey consumed. but, predators increase their search activity as prey density increases. the proportion of prey actually consumed in this type is lower at low prey densities in comparison to type II. the type of function response depends on the encounter rate (ability of a predator to find prey) and the handling time (ability of the predator to kill, eat, and digest its prey once it has found it)
how, and by what mechanisms, are vents connected
vents are connected via larval supply. larvae supply is thought to come from nearby vents, and therefore, is a function of currents, extinction/birth of vents (if a vent goes out, its no longer supplying larvae), and larval duration/requirements. larval biology of hydrothermal vent species differs between taxa, but most are non-feeding. the thermal tolerance studies indicate larvae for some species require temperates < 7 C for development, so they must disperse away from vent. based on laboratory experiments, giant tube worm larvae survive for 38+ days without feeding. the slow metabolic rate of larvae allows them to have long-non-feeding larval phases, and they could potentially disperse via currents 100km+ in a non-feeding stages. larvae may respond to species-specific chemical, physical, acoustic, or biological cues and settle, but not well understood the dispersal potential, topography, and environmental conditions determines extent of connectivity between vent communities. species have potential to disperse to intermediate, non-vent habitats (i.e. whale falls and cold seeps), which can ultimately increase connectivity between vents via metapopulations.
explain how phytoplankton communities are affected by temporal changes in nutrients and water column turbulence (stratified vs well mixed)
vertical gradients in the relative availability of light vs nutrients. light decreases with depth, and the nutrient availability depends on water turbulence (can be limiting in a stratified water column or plentiful in a turbulent/mixed column). in seasonal seas, nutrients can be limiting in summer due to a stratified water column and be plentiful in winters when waters are mixed/more turbulent. phytoplankton communities vary with depth and depend on nutrients and water turbulence; community composition is based on the strategies of the phytoplankton to utilize available resources. a stratified water column creates vertical differences in species distributions (high vs low light clade of phytoplankton). niche differentiation along environmental gradients is important in the maintenance of diversity in phytoplankton communities. in a well-mixed water column, turbulence erases vertical differences in phytoplankton communities -- nutrients available everywhere, less strict gradients
describe the physical stressors organisms face while living in the intertidal zone and how they cope with each stressor
water loss -- when exposed at low tide, organisms risk desiccation (especially if low tide is during the day and/or in summer). coping mechanisms include hiding (mobile organisms move to tide pools, such as periwinkle snails), closing up (i.e. bivalves, such as limpets), and tolerance (chitons can tolerate 75% of water loss). temperature -- organisms must adapt to heat in the summer and cold in the winter. coping mechanisms include moving into crevices and light shell colors in snails. other organisms can simply cope with extreme temperatures (the periwinkle snail can survive up to 100 F in a lab setting) salinity -- the salinity of tide pools could vary depending on temperature and precipitation. coping mechanisms include tolerance to a variety of salinities, burrowing, or reducing activity. wave action -- depends on environment -- large waves and rocky shores, or soft sediment with small wave action? some organisms undergo a more compact shape to endure wave action. anemones, for example, grow taller in sheltered areas and shorter in areas of higher wave action. space -- competition for space can be very high (specifically for sessile organisms). organisms must adapt to be a good colonizer (first to settle in an open space), must be good at keeping a space, quick to reproduce to fill other spaces with offspring, and/or be able to take over an already-occupied space (such as limpets, which can grow over competitors) oxygen -- organisms might be exposed to air or confined to tide pools at low tide. some species (i.e. mudskippers) have evolved the ability to exchange gas in both air and water. others can reduce their metabolic rate to conserve oxygen.
