Marine Ecology Exam 1
Define the three types of succession. Which one typifies salt marsh succession and systems represented by alternative stable states?
(1) Facilitative: Where species A has a positive effect on species B and then species B has a negative effect on species A and out competes it. Ex: Spartina stabilize and make salt marsh more habitable, and then sea lavender comes in as secondary species and then outcompetes spartina. (2) Tolerance: When species A gets there, changes the environment, and, while having a negative effect on species B, has a greater negative effect on itself. Ex: Pine creates a lot of shade, and neither oak nor pine trees grow better in shade, however oaks are more tolerant of shade than pines are. (3) Inhibition: Inhibition is where whoever gets there first wins. Ex: In areas where bryozoans are established first, tunicates and sponges cannot grow there. Facilitative succession typifies salt marsh succession.
What are three important stressors that impact seagrasses and what mechanisms do plants use to deal with these stressors?
(1) Waves - Seagrasses typically grow behind wave attenuating structures such as coral reefs to prevent uprooting. (2) Algae - Epiphytic algae grow on seagrasses and if the water is eutrophic, algae have the potential of out competing seagrass for light, effectively shading them out. Seagrasses help mitigate the impact of algae by providing a habitat for mesograzers who eat the algae. This represents a trophic cascade where seagrasses facilitate mesograzers to eat the algae which in turn helps the seagrass. (3) Nutrient loading - In nutrient limited situations seagrasses will preferably maximize root growth over shoot growth in order to uptake the most nitrogen. Seagrasses have also developed relationships with other organisms to help them deal with eutrophic environments. We see that when seagrasses are in areas with mesograzers they are able to tolerate nitrogen levels that are 10x higher than in areas without mesograzers.
Describe three examples of how animals positively impact Spartina growth? What types of interactions are these?
(1) ribbed mussels enhance nitrogen availability to the plant by capturing nutrients from the water column through filter feeding and depositing feces or pseudofeces on the sediment surface. They can also limit sediment erosion and disturbance. (2) burrowing crabs are able to aerate the marsh soil and indirectly enhance plant growth by facilitating colonization of fine roots by nitrogen-fixing bacteria, which would die without oxygen. (3) Nearshore oyster reefs have been shown to reduce wave energy that would normally result in shoreline erosion and in doing so, benefits emergent shoreline vegetation such as Spartina. These types of interactions are known as facultative mutualisms as both interactive species receive benefits from one another.
A) How does disturbance from predators or other physical agents generally affect competition? B) What impact does this effect typically have on the number of species that can coexist in a community? C) Using increasing intensity of disturbance as your independent variable, draw a conceptual diagram show how biodiversity should change with increasing predation or physical disturbance in a community.
(A) Competition generally decreases as disturbance increases. (B) The number of species that can coexist in a community increases because disturbance does not allow dominant species to outcompete all other species.
(A) What is the range of food chain links typically found in natural food webs? (B) List three factors that can limit the total number of food chain links in a food web AND discuss why they can limit food chain link? (C) Construct a biomass pyramid reflecting relative biomass at each trophic level for the food web of the Serengeti Plains. The opposite/inverse pattern of that Serengeti Plain biomass pyramid is true for open ocean systems. Draw this open ocean biomass pyramid as well. Formulate a hypothesis as to why these biomass pyramids are the inverse of each other?
(A) Primary producers -> Primary Consumers -> Secondary Consumers -> Tertiary consumers -> Quaternary Consumers (top predators who as an adult are not eaten by other animals in the system) (B) 1. Infectious disease: 2. Overharvesting: 3. Species Diversity: (C) The biomass pyramid of the ocean is inverted because plankton make up less biomass than animals higher up the food chain. However, they have shorter life spans and reproduce quickly.
(While driving 4 hours from Phoenix to Flagstaff to go skiing for a weekend, you notice and enthusiastically point out to your friends in the car that as elevation increases, the native plant community switches from cactus-dominated in Phoenix, to shrub- dominated at mid elevations, to pine-dominated in Flagstaff (This actually occurs!!!!). A) Generate a hypothesis as to what types of physical gradients (e.g. gradient in wave action) could be present and prominent along this elevation gradient and state whether these physical factors are decreasing or increasing with elevation. B) Choose the one that you think is most important in influencing the species distribution patterns you see. Justify your choice. C) Design an experiment to test the relative importance of this physical factor and plant competition in determining the plant zonation patterns you observe.
(a) Hypothesis: If the following gradients change with increased elevation, then the plant species more adept to such conditions will dominate. (i) Rainfall/water source - increasing with elevation; (ii) Direct sunlight - decreasing with elevation; (iii) Oxygen - decreasing with elevation; (iv) Temperature - decreasing with elevation. (b) Being Arizona has variable rainfall across the state, which is heavily influenced by the change in elevation, I imagine that is the most important in distributing plant species. Consider the cactus in Phoenix, with very minimal rainfall events, cacti are capable of withstanding the harsh heat and little water--as they manage to store water for long-term use with any rainfall event. At mid-elevation, the shrub face more rainfall, but in unreliable frequencies as the climate is very temperate. Plants that require frequent rainfall (pine) are not equipped to handle such landscapes, alternatively plants that are not equipped for too much rainfall (cacti) cannot withstand this landscape too. In Flagstaff, the rainfall frequencies are a lot more reliable, allowing for tall and wide trees like pines to grow and out-compete to survive. (c) In all three elevation areas, introduce cacti, shrub and pine in same plots (with control plot nextdoor). Observe how plant species survive and compete over 1 year. (i) Independent Variable: species introduced (ii) Dependent Variable: elevation and rainfall
a) What is the Coriolis effect? b) How is it generated? c) And how would it impact a giant swarm of krill floating in body of oceanic water moving 500 miles from East to West vs. one moving 500 miles South to North in the Northern Hemisphere? d) how does it affect the way that wind in hurricanes flow in the Northern Hemisphere?
(a) The Coriolis effect refers to the air mass curves relative to the earth's surface due to Earth's rotation. In the Northern Hemisphere this effect causes the air to deflect to the right of the direction of the air movement, and in the Southern Hemisphere the deflection of the air is to the left of the direction of air movement. (b) The Coriolis effect is generated by the rotation and spherical geometry of the earth. A point at the equator must travel farther, and therefore faster, than a point at higher latitudes. Air that begins to travel north from the equator, for example, will have a greater eastward velocity than the air mass it's moving into, and will have an apparent deflection to the right. (c) A swarm of krill moving South to North in the Northern Hemisphere would tend to float to the East, whereas krill moving East to West would float to the North. (d) The Coriolis effect causes all hurricanes in the Northern Hemisphere to rotate in a counterclockwise direction. As the low pressure system of a hurricane forms, it attracts high pressure air from the outside. As that high pressure air flows in, it is deflected to the right, resulting in the counterclockwise rotation.
Compare and contrast how acidification, increased nutrient loading, and over fishing might impact oyster reefs and seagrasses.
(i) Acidification hurts both oyster reefs and seagrasses. For oysters increased acidification can lead to dissolving of their calcium shells which leads to them having a decreased survival. However both seagrasses and oyster reefs seem to be able to mitigate the impact of ocean acidification for other species in their area. When oyster shells dissolve they decrease the acidity of the water around them. ""As ocean water becomes more acidic, oyster shells begin to dissolve into the water, slowly releasing their calcium carbonate—an alkaline salt that buffers against acidity. An oyster reef is a reservoir of alkalinity waiting to happen." Seagrasses through their absorption of carbon are able lower the amount that can react with water reducing the amount of carbonic acid produced. (ii) Increased nutrient loading can be detrimental for seagrasses. Extra nutrients in the water increases the amount of algae which can outcompete seagrasses for light. It is also a detriment for oyster reefs. As nutrient levels increase so do algae and bacteria who can use up available oxygen creating a hypoxic environment that oysters can not compete in. (iii) Overfishing is detrimental for seagrasses as it creates a trophic cascade. As the big fish are removed from the habitat, small fish populations increase which eat more of the mesograzers who can not longer keep algae blooms at bay. Overfishing can cause declines in spat survival. Blue crabs and toadfish scare mudcrabs and keep them from openly hunting in oyster habitat. By keeping them in cracks and crevices oyster spat have an increased survival.
Functional relationship
**Trophic or structural complexity. A functional response is the change in predator's rate of prey consumption with change in prey density. **double check
Name three marine ecologists whose work has generated major advances in ecological theory. Explain those advances and its impact on the field of ecology.
-Joe Connell, who manipulated barnacle neighbours to test the hypothesis that interspecific competition was an important determinant of zonation patterns, and Bob Paine, who removed starfish apex predators from rocky shores to demonstrate that consumer control affects interspecific distribution, were both instrumental to shifting the focus of marine ecology from the widely held view that physical conditions determined the distribution and abundance of marine organisms. This physical forcing paradigm thrived among ecologists until the mid 1950's, until these experiments by Paine and Connell suggested that biota, or the animals themselves, could regulate organism distribution and abundance, changing ecology for decades to come. As an aside, Connell would go on to propose the intermediate disturbance hypothesis in the late 1970's. -Raymond Lindeman's work on trophic levels revolutionized the way scientists perceived energy transfer. He argued that energy was transferred from one part of an ecosystem to another. He suggested that net production at one trophic level is generally only 10% of the net production at the preceding trophic level (the 10% rule Lindeman hypothesis). 90% of the transfer is lost to metabolic maintenance. Lindeman's work was further developed by H.T. Odum who developed the idea of 'bottom up' resource control over ecosystem structure and function.
Emergent Property
Properties of an organism, community, or ecosystem that are seen through the interactions of smaller parts. If the parts were acting alone they would not exhibit that particular property.
What is a foundation species? Name 4 invert taxa that can act as foundation species? Name at least 3 characteristics these taxa have in common that allow them to rise to such prominence in marine systems?
A foundation species is a species that generates an ecosystem by creating habitats and modifying the environment with positive effects on the diversity, distribution, and abundance of associated organisms. Four invert taxa that can act as foundation species include sponges, mussels, corals, and oysters. All of these taxa have the ability to improve stressful physical conditions, they provide structures that plants and animals can live in, and are strong facilitators.
Functional vs. Energy Food Web
A functional food web looks at the roles of organisms in a system and how interactions between predators and prey can impact populations. However, an energy food web looks at the way that energy moves through a system based on who is eating whom. For example, consider lions and wildebeests vs. wolves and elk. Lions prey on wildebeests, but lions are not the controlling factor of wildebeest population levels. Lions would not be connected to wildebeests on a functional food web, but would be connected on an energetic food web. Wolves, however, have been shown to be a significant predatory controlling factor on elk populations, so wolves and elk would be connected through both a functional and energetic food web. Energetic food webs often show the magnitude of the flow as well, indicating which species are most important in the diet of its consumer.
Bipartite life cycle
A life cycle that has two parts which include a larval stage and an adult stage. This includes about 70-80% of marine fish and invertebrates and nearly all algae. Adults reproduce to generate pelagic larvae that have a pelagic larval duration before entering a second life phase as an adult.
Numerical relationship
A numerical response in ecology is the change in predator density as a function of change in prey density.
Disturbance
A relative change in an ecosystem, or environment, caused by some force (biological / physical / anthropogenic).
Foundation species
A species that generates an ecosystem by creating habitats and modifying the environment with positive effects on the diversity, distribution, and abundance of associated organisms. They can act as buffers for both biotic and abiotic stress.
Keystone species
A species that has a disportionate effect on its environment relative to its abundance. Sea otters are a classic example in which their predation on sea urchin prevents overgrazing of sea kelp.
Spartina
Also called cordgrass, xxxxxx is a genus of grasses often dominant in the lower intertidal zone of salt marshes. Dense xxxxxx vegetation aerates often anoxic soils, enhances sedimentation, and reduces desiccation and soil salinity, making xxxxxxx a foundation species of salt marsh ecosystems on the east coast of the US.
Using graphs and words describe alternative stable states and define hysteresis. Draw and describe a graph of urchin density (ind. variable) and kelp abundance showing hysteresis.
Alternative stable states occur when the trajectory of a declining ecosystem is asymmetrical with the trajectory of recovery. This theory predicts that ecosystems can exist in multiple states, but that transition from one state to another occurs only after a high enough level of disturbance. Alternative stable states only occur under the following combination of conditions: 1) there is inhibition succession; 2) the ecosystem features a positive feedback in which species A replaces species A every time; and 3) the ecosystem experiences hysteresis, which occurs when the rate of recovery is not equal to the rate of decline. Hysteresis can be taken as a measurement of the resistance of the system to return to its previous state. In the chart below, each stable state follows a trajectory of the solid lines, hitting a point of hysteresis when an extreme enough environmental variable leads to a transition to the alternate state. Hysteresis is reflected in the fact that the system will not follow the dotted line for a continuous, symmetrical recovery, but will instead require greater time and environmental change to return to its previous state (as indicated by the solid lines). The following chart demonstrates this process in kelp beds, where increasing density of urchins can initiate sudden transition to a stable urchin barren state. In effect, fewer urchins are required to maintain a barrens than to create one. It is therefore difficult to restore the kelp bed after transition, reflecting a hysteresis effect.
Indirect effect
An ecological process in which one species impacts another through a chain of direct interactions mediated by one or more 'intermediate' species. Ex: Trophic cascades - in which a predator may impact a primary producer by controlling the population of that primary producer's consumer. Such is the case in rocky intertidal ecosystems where sea otters, by eating large quantities of sea urchins that predate seagrass, indirectly support the growth and survival of seagrass.
Why do you think that asexual reproduction is such a successful strategy for wetland plants? Draw a graph of salt marsh plant decline and recovery along a drought intensity gradient with two different scenarios: when marsh plants can grow clonally and when they cannot.
Asexual reproduction is a successful strategy for wetland plants because it allows the plants to reproduce when there is limited resources, zonation pressures or from physical stress. Wetland plants are found within a zonation gradient along the shoreline. Plants that can tolerate higher levels of stress are found in higher salinity zones, but have their upper boundaries in their zone defined by competition pressures. During times have higher physical stress (like anoxia or high salinity), wetlands plants can asexually reproduce by clonal growth.
Compare and contrast alternation of generation in polymorphism in Cnidaria and Algae.
Cnidaria have an alternation of generation that occurs seasonally, while algae alternation of generation may also occur as seasonally or be influenced by extreme temperature, predation or other stressful effects (need to clarify when algae undergoes this alternation. I was unclear based on the video lectures). Jellies, and some other cnidaria, alternate between two main life forms- a medusa ("adult" free-swimming stage of Kimia jelly) and a polyp (the sessile stage of a jelly). The adult jellies release gametes and the eggs are fertilized through external fertilization. This develops into a larva that settles onto a substrate and metaphorizes into a polyp through the winter (each polyp is very small). When the water temperature increases again in the warmer months, the polyp undergoes strobilation which produces multiple small jellies that are then released in the medusa form. Algae also alternates between two forms in their alternation of generation; diploid and haploid. A diploid "adult" algae releases gametes into the water, but instead of fertilizing each other right away, each gamete undergoes mitosis and becomes a haploid algae that settles onto a substrate (and can withstand grazing and wintering) and continues to grow to be bigger than a single haploid cell (not clear about how big a haploid algae is). These haploid algaes will then produce haploid gametes that can then fertilize each other and form a diploid cell that can grow into a diploid algae.
Define bipartite life cycle? Describe the bipartite life cycle in 3 different species each occurring in a different phylum. Describe 3 advantages species might gain from a bipartite life cycle? Describe 2 advantages of having crawl-away larvae?
Definition: A bipartite life cycle has two parts which include a larval stage and an adult stage. Usually one stage is very sedentary while the other is open ocean and moving around a lot. || 3 examples w/ links of life cycle: (1) Blue crabs: blue crabs reproduce through internal fertilization. After the male inseminates the female, the female holds the eggs in her apron and broods them, eventually migrating from the rivering estuary to the open ocean, where she release her larvae by swimming to the surface and shaking her body to release zoea (first larval stage of blue crab). Blue crab larvae stays in the pelagic zone, going through several stages of development, before migrating (vertically) with the currents back into estuary, where the blue crab will now carry out the rest of its life in the benthic zone. (2) Oysters: oysters reproduce by external fertilization (eggs and sperm are released into the water to be fertilized). Once the eggs are fertilized in the water, the developing larvae float around (~ 2 weeks) until they are ready to attach to a resting spot (e.g. rocks). These young oysters, also known as spat, will now need ample food and time to develop their hard shells for protection as they grow in size. (3) Red sea urchin: Sea urchins gather in large groups that contain both males and females. The females expel hundreds of millions of orange eggs, which prompts the males to release their clouds of white sperm. Urchin eggs float in the warm sea water for up to eight weeks. They then hatch into larvae and drop to the floor of the ocean where they attach to a rock with a sucker foot while they mature. (4 additional) Cannonball jellyfish: description (kind of long) of life cycle can be found in this paper. || 3 advantages of bipartite life cycle: Larvae in pelagic zone experience decreased predation, decreased competition, and increased opportunity to colonize better habitats (so increased dispersal). || 2 advantages of crawl away larvae: Increased parental care (jawfish for example), increased genetic structure because young are not dispersing as far.
What is a competitive dominant? Describe 3 forces that can maintain species co-existence in the presence of a competitive dominant? Why do these forces have such effects on increasing diversity?
Definition: A competitive dominant is the species that is the best at acquiring the most limited resource. || Gradients in physical stress (disturbance), gradients in predation stress, and gradients in temperature stress (tolerance) are 3 forces that can help maintain species coexistence in the presence of a competitive dominant. || Tradeoffs and the intermediate-disturbance hypothesis can help explain why these forces have such affects on increasing diversity. Essentially, species cannot specialize in everything, so tradeoffs explain why some species are better than others at surviving under certain conditions. Competitive dominants (generally bigger in size, slower in growth, and better at acquiring resources) will lose out to the more stress tolerant inferior dominants (generally have proteins to handle heat shock, higher dispersal capacity, faster growth rates, and shorter life spans) when there's an increases in disturbance, or temperature. So this [increase in disturbance] leads to competitive inferiors being able to co-exist because there are some, but significantly fewer, competitive dominants (i.e. the intermediate disturbance hypothesis).
Compare and contrast the reproductive cycles of the eastern oysters and Spartina plants?
Eastern oysters are bipartite (having two distinct forms in their life cycle). Adult oysters release gametes into the water column and create a trochophore (planktonic oyster) through external fertilization. The trochophore develops into a veliger, and then a pediveliger (all planktonic stages -double check pediveliger). It then grows into a juvenile, settled oyster known as a spat (early and late stages here), which continues to grown into an oyster. Spartina plants can undergo either sexual or asexual reproduction. In times of physical stress, Spartina will use asexual reproduction (clonal growth or vegetative propagation). Clonal growth is when a parent plant sends out a rhizome underground to a space near it. This rhizome can then start growing another shoot (or a ramet) of Spartina that is a genetically identical copy of the parent Spartina. Spartina can reproduce sexually by seed dispersal. (need to double check that this is the only means of sexual reproduction for Spartina).
Compare and contrast the terms ecosystem services and functions. Describe 3 ecosystem functions that oyster reefs, seagrasses and salt marshes have in common. For each function you mentioned, list a corresponding service.
Ecosystem functions are natural process or characteristic exchanges of energy that take place in the various animal and plant communities of the different biomes of the world. Primarily, these are exchanges of energy and nutrients in the food chain which are vital to the sustenance of plant and animal life on the planet as well as the decomposition of organic matter and production of biomass made possible by photosynthesis.On the other hand, ecosystem services are the set of ecosystem functions that are useful to humans and animals. 1) One ecosystem function oyster reefs, seagrasses, and salt marshes have in common is their habitat for fish animals. By acting as a habitat for coastal organisms it creates a food web for fish consumption for human use. 2) They also regulate water composition and act as filters, improving water quality in the area. 3) These habitats also act as carbon sinks which reduces carbon dioxide in the atmosphere, an important service for combating climate change.
What is El Nino and why does it lead to decreased body health index in sea lions?
El Niño is the warm phase of the El Niño Southern Oscillation (commonly called ENSO) affecting the equatorial Pacific region and beyond every few years, characterized by the appearance of unusually warm, nutrient-poor water. Warming ocean temperature decreased food supply of sea lions because of the decrease in nutrient supply from El Nino. During the El Nino of 2015, mothers of seal pups born on California's channel islands, found west of Los Angeles, are finding it difficult to find their usual prey of sardines and anchovies, which moved to cooler areas further north to escape sea temperatures that were 2-4 degrees Celsius warmer than average. This meant that pups, initially reliant on their mother for nutritious milk, were underweight and understrength when they have to find their own food.
Green vs. brown food webs
Food webs based on primary production are XXX food webs. Food webs based on detritus, or dead particulate organic material, are XXX food webs.
Why for salt marsh plants and mangroves are the upper elevation range limits of plants most often set by competition and their lower elevation range limits set by physical forces, while the opposite pattern occurs for rocky intertidal organisms?
In salt marshes and mangroves, nutrient limited systems restrict the ability for plants to move up. Other plants are able to outcompete them for nutrients because those plants that dominate at higher levels have not made sacrifices that allow them to survive at lower elevation limits. For example, Spartina is able to survive under the extreme physical stress of frequent inundation and hypoxia through the use of aerenchyma to transport oxygen efficiently down to its roots. However, this trade off make it less efficient at taking up and transporting nutrients like nitrogen. For this reason, other plants like Juncus are able to outcompete Spartina for the limited nutrients, preventing them from moving upwards. However in the rocky intertidal, the upper zone is more exposed to physical forces like desiccation, temperature, and gas exchange since the organisms in this zone will be exposed to air a larger percentage of the time than in lower areas. This limits the organisms in this zone to only those that are most capable of handling exposure to air and sun. However, the organisms in the lower intertidal zone grow faster and larger and will outcompete organisms from the upper intertidal for space. Additionally, predation becomes more of a factor in the lower intertidal with organisms like seastars preying on mussels and other organisms. However, these predators are less able to move up due to risk of desiccation.
Trophic cascade
Indirect effects of carnivores on plant populations or the progression of indirect effects by predators across successively lower trophic levels (Food webs lecture - slide 29). For example, sea otters have positive effect on kelp, because they control sea urchins which feed on kelp. Conversely, killer whales have negative effect on kelp, because killer whales prey on sea otters.
Describe and draw the life cycle of blue crabs? Based on this understanding, should the states of VA or NC work together to coordinate their efforts in regulating blue crab fisheries? What other information might be helpful to see if this coordination is necessary?
Male crabs cradle soft-shelled female in their legs and finds a protected area for her to molt. The crabs mate after she molts then protects her until she hardens. She develops an egg apron that she fans as the inseminated eggs develop. Female crabs will swim to saline waters with the egg apron and shake the eggs off. Inseminated eggs hatch and zoea are transported by currents in the open ocean, where they will go through 13 to 15 molts before becoming a benthic crab. Zoea metamorphose into megalops during their last larval molt. Megalops will migrate back into the estuary by migrating vertically to avoid outgoing tidal currents and to catch incoming tidal currents. Megalops settle in seagrass beds and submerged aquatic vegetation which serve as nursery habitat. North Carolina and Virginia should coordinate their efforts in regulating blue crab fisheries if a majority of larvae do not return to the parental estuary. Physical variables such as currents and winds along with genetic information on blue crabs and larvae from both regions will be helpful to see if this coordination is necessary. Regardless, North Carolina should not be allowed to harvest sponge crabs and the female population and nursery habitats in both states should be protected.
Lacuna
Marine snail in the family littorinidae; commonly occurs in the marsh and intertidal.
Why was Bob Paine's study so important to ecology? Since this seminal work, we have recently found that the mussel beds he studied actually housed a more diverse assembly of animals (because of so many infauna) than areas without mussel beds. Does this change the importance of his original study? If yes, how so?
Note: Referring to the 1966 American Naturalist paper discussed in the rocky shore lecture. This study tested (and supported) the hypothesis that: "Local species diversity is directly related to the efficiency with which predators prevent the monopolization of the major environmental requisites by one species." One case study from the paper involved the removal of a starfish (Pisaster) from a rocky shore. What followed was a "process of successive replacement by more efficient occupiers of space." Barnacles first expanded but were then overrun by mussels. Thus, Paine decided, "the removal of Pisaster has resulted in a pronounced decrease in diversity... the systems converge toward simplicity... and becomes less diverse." If the mussel beds studied were actually higher in diversity than areas without mussels beds then it is possible that the importance of the original study was changed. If Pisaster predation removed mussels and thus then infaunal communities supported by the mussel beds, then the removal of a top predator might actually INCREASE the diversity of the system and support "Margalef's (1958) generalization... with higher successional status towards 'an ecosystem of more complex structure.'" There could be confounding factors but at its simplest interpretation, it would reverse Paine's conclusions from the original study.
Ecology (Population; Community; Ecosystem)
Population - amount: density of species (Nitrogen); rate: dN/dt — competition, predation, acidification, food availability Community - amount: # of species (richness); relative abundance (evenness) Ecosystem - amount: elements, function, integrated across trophic levels; rate: rate of productivity change within entire ecosystem
Why do salt marshes dominate the intertidal zone on the East Coast of the US, while rocky shores dominate the West Coast? How does this impact the distribution of fiddler crabs and the amount of carbon sequestration on the East vs West Coast US shorelines?
Salt marshes succeed in intertidal zones on the East Coast because there is minimal wave action due to the shallow depths and very far-reaching continental shelf. Since the continental shelf is much closer on the West Coast, wave action is stronger (and sediment is not able to accumulate with this extremity of wave action), therefore rocky shores are best equipped to withstand it. The lack of salt marshes on the west coast thus limits the geographic range of fiddler crabs compared to their east coast range stretching all the way to Massachusetts. This also means east coast areas can sink considerably more carbon than their west coast rocky shore equivalents.
Aerenchyma
Spongy tissue that forms channels between the roots, stems, and leaves of some plants to allow for increased gas exchange; this is particularly advantageous in hypoxic conditions (salt marshes) and prevents the plant from incurring the metabolic costs of anaerobic respiration.
Intermediate disturbance hypothesis
Suggests that species diversity is maximized when disturbances are neither rare or frequent. Too frequent or large of a disturbance can risk species extinction, however too rare or small of a disturbance allows for increased interspecific competition that results in one species dominating an ecosystem.
Resilience
The ability of an ecosystem, population, species, or individual to recover from disturbance, resist perturbation, or acclimate to changing conditions.
Coriolis effect
The air mass curves relative to the earth's surface due to Earth's rotation. In the Northern Hemisphere this effect causes the air to deflect to the right of the direction of the air movement, this is because the air at the equator is moving faster than the air further north. In the Southern Hemisphere the deflection of the air is to the left of the direction of air movement.
Ekman spiral
The displacement of current direction by the Coriolis effect and wind. When surface water moves by the force of wind, they drag deeper water below them (through friction). Each deeper layer moves more slowly from the one above. Each layer is deflected by the Coriolis effect (45º right at surface in N. Hemisphere), so each successively deeper layer moves more slowly to the right (N. Hemisphere), creating a spiral effect. At 70 meters down, the water is flowing at the opposite direction of the wind. The xxxxxxx influences vertical migration of larvae, generates circulation cells, and causes upwelling (and gyres).
Trade-off
The idea that a singular organism cannot specialize in everything. In other words, an organism, like a wetland plant, can be function well in lower oxygen environments, but does not do as well in nutrient efficiency. There are 3 types; colonization-dominance, physical stress tolerant- dominance and predation tolerance- dominance.
Lindeman's Rule of Food Webs
The idea that only 10% of the energy from organic material transferred from one trophic level to the next is retained and the rest is lost (when transferred, broken down in respiration or due to incomplete digestion from a higher trophic level).
Scientific method
The primary way that scientists develop knowledge, through systematic observation, experimentation, and measurement. At the core of this method is the formulation, testing, and adjustment of reasoned and informed hypotheses.
Recruitment
The process by which new individuals find a population or are added to an existing population. For example for fish, the number of fish surviving to enter the fishery or to some life history stage such as settlement or maturity.
Settlement
The process by which the pelagic larval stage selects a site to recruit and become their adult stage. They can use chemical, visual, auditory, or environmental cues to site select.
Self-recruitment
The proportion of larvae returning to and settling in their natal population.
Connectivity
The relative ability of populations to move between environments and/or interact with one another due to the physical or ecological conditions of their environment. From Merriam et al, "the degree to which the landscape impedes or facilitates movement among resource patches." Determines dispersal rates, which sets gene flow, extinction risk, etc.
Describe 2 adaptations salt marsh plants have for living in wet environments and 2 for living in salty ones.
To adapt to living in wet environments where oxygen can be limited, salt marsh plants have special air or pore spaces in their roots and stems called aerenchyma through which oxygen can enter the plant and be transported to its roots. Salt marshes, to combat anoxia, also have evolved to have larger roots to store oxygen. To adapt to the physical stress of high salinity salt marshes can exclude salt by closing off root transporters. They are becoming regulators when they make this change. Salt marshes can also become iso-osmotic in which they become just as salty as the water. They are becoming conformers in this scenario.
Define trophic cascade and food chain length. How can changes in FCL affect the outcome of a trophic cascade? Compare and contrast the mechanisms and end results of the trophic cascade in rocky shores as described by Bob Paine and in salt marshes as described by Silliman and Bertness.
Trophic cascades are indirect interactions between species starting with predators and cascading to lower levels. Often the presence of predators is beneficial to plant populations by controlling grazer populations. Longer trophic cascades can occur in systems where a top trophic level predator controls the population of a mesopredator which controls grazer populations. In this situation, the decline of the top predator can lead to mesopredator release, resulting in overpredation of the grazers by the mesopredators. Food chain length is the number of links from the bottom of the foodweb to the top of the food web. In longer food chains, the trophic interactions and cascades can be quite complex. Generally food chains with odd numbers of trophic levels lead to higher levels of primary producer biomass with larger populations of top predators (Otters -> Urchins -> kelp) while food chains with even numbers of trophic levels lead to lower levels of primary producer biomass with larger top predator biomass (Sharks -> grouper -> reef grazers -> algae). Paine removed Pisaster (a keystone, predatory sea star) from a section of the rocky intertidal. Pisaster normally preys on mussels and barnacles, but with Pisaster removed, the mussels were able to flourish and out compete the overwhelming majority of other organisms for space, which is one of the key limiting factors in the rocky intertidal. As a result, species diversity without Pisaster declined from 15 to 8. Benthic algae, chiton, and limpets were unable to exist in areas without Pisaster due to lack of appropriate food and lack of space. Removing Pisaster also decreased anemone density and messed up the sponge-nudibranch food chain, demonstrating indirect effects of Pisaster removal. Similarly Silliman and Bertness conducted predator exclusion experiments and also tethered snails by gluing a small piece of fine nylon line to adult Littoraria, allowing them to graze normally, but preventing them from moving up the cordgrass to escape predators in the water. These experiments showed that in the absence of predators (blue crabs in particular), Littoraria can have massive impacts on Spartina by overgrazing and can turn salt marsh to mudflats. In both studies, a trophic cascade is demonstrated when a top predator is removed from the system. In the saltmarsh, the cascade is simple. Crabs eat snails which graze on Spartina. Less crabs leads to more snails which leads to less Spartina. In the rocky shore study, the food web is more complicated. Basically, starfish prey on mussels which do not prey on other organisms, but instead are effective at competing for space. As a result, removing starfish increases the competitive dominant mussels which decreases the barnacles, algae, chiton, anemones, and limpets that can exist in the space. In both cases diversity is decreased with the removal of the top predator, but in Paine, the impacts affect more species. Also, in the salt marsh, the trophic cascade results in turning the salt marsh to mudflat, leaving large areas of basically uninhabited sections. On the rocky shoreline, the overall biomass or inhabited area remains the same or may actually increase, but the diversity is lost.
Discuss how variation in flow rates and wave exposure can impact growth and distribution of oyster reefs and seagrasses both directly and indirectly.
Variation in flow rates and wave exposure directly impact growth and distribution of seagrasses through stress exposure and sediment availability. Wave stress impacts the consolidation of sediment, and seagrasses can only grow in unconsolidated sediment (i.e sandy bottom) vs. rocky bottom. Additionally, seagrasses are unable to grow in high wave stress environments as high constant wave stress will rip out the seagrass roots from the sediment. Thus, seagrasses usually grow behind something like coral reefs, that dissipate the wave stress. Seagrasses must be constantly submerged in salt water, or else they will dry out and die (desiccation). Wave exposure can indirectly impact growth and distribution of seagrasses through disturbance, which will allow for facilitative succession. Halodule can colonize first after a disturbance and stabilize the sediment for other (more competitively dominant) seagrasses. Flow directly influences oysters through larval recruitment. High larval recruitment occurs in high flow, narrow areas because there is a greater flux of larvae, such as in Narragansett bay. In a low flow, non-constricted area, there is less larvae. Flow indirectly effects oysters through salinity, with oysters unable to survive in low salinities (and in higher salinities, predation occurs). Wave stress can indirectly effects oyster distribution through substrate. As waves influence the substrate available, oysters can only colonize on harder substrates (i.e not mud). Additionally, oysters live between mangroves/marshes and sandy beaches (in terms of wave stress tolerance from low to high).
Trait-mediated indirect effect:
When the impacts of one species on another are influenced by one or more intermediate species. "For example, the presence of species A causes modification of a trait in species B, which in turn modifies the interaction of species B with species C. The trait modification in species B by species A is a non-consumptive effect (NCE), and the indirect effect of species A on species C as dictated by the NCE of A on B is termed a trait-mediated indirect effect or interaction (TMII)."
Warming seas are killing kelp in Japan and leading to range contraction, yet within the last decade it was discovered that kelps live in the tropics. Explain this apparent paradox.
Whereas kelp is unable to thrive in warm waters, the cold water refugia hypothesis allows us to explain this paradox. Depth and cold currents play a pivotal role in determining where kelp can thrive, as illustrated by the discovery of kelp in tropical waters off the Galapagos in areas of cold water upwelling. Species of kelp that have become endangered in cold Pacific waters were found 5m below the surface of the ocean on the cold-current side of the Galapagos islands. These pockets of depth and cold water upwelling have allowed kelp to thrive in environments that would typically be too hostile for kelp to colonize, suggesting that marine biodiversity may be more tolerant to climate change than we had previously believed.
Crassostrea
a genus of true oysters belonging to the family Ostreidae, which are particularly important for economic purposes/human consumption
Zostera
genus of seagrasses known as eelgrass, typically found on the east coast of NC. This seagrass offers many different ecosystem services such as creating fish nurseries, wave attenuation (though not as much as reefs) sedimentation, and carbon sequestration.
Science (Silliman; textbook)
the study of cause/effect using the scientific method; Textbook: experimental, hypothesis driven investigation of phenomena to elucidate 1. patterns in nature and 2. processes governing the formation, maintenance and changing of those patterns