Marine Ecology Final

Provide a thorough explanation for Hypothesis 1 from the previous question.

17-60% of juveniles and adults COT have been observed with missing and regenerating arms, indicating strong predation pressure. Small COT are nocturnal emerging only when visually orienting fish are inactive. The adults feed during the day, suggesting that structural defenses are more effective for larger COT. On the GBR four fish are known to prey on juvenile COT, and they are now rare, only the humphead Maori wrasse (now protected) has been fished. The giant Triton, a COT predator, was reduced by shell collectors and remains rare, even though it is now protected. There may be other targeted species of fish that aid in COT suppression, though their roles as potentially important COT predators has yet to be demonstrated.

What is a dispersal kernel?

A dispersal kernel is the modeled statistical probability distribution of dispersal distance, the probability that larvae dispersed at one location will disperse to another.

Define autogenic and allogenic ecosystem engineers and give an example of each.

A) Autogenic ecosystem engineers change the environment by their own physical structures (living or dead tissues). These are often foundation species such as coral reefs and kelp forests that create physical structure. B) Allogenic ecosystem engineers change the environment by transforming living or non-living materials from one state to another. For example zooplankton who through their feeding activity remove organic and inorganic particles from the water column and package them in fecal pellets, impacting both delivery of food to deeper waters and ocean water column biogeochemistry.

To what degree did Witman find that local species richness was a function of regional species richness?

About 75% of variation in local species richness was explained by variation in regional species richness.

Grazing rate is an ecosystem function provided by herbivores on coral reefs, and a certain high grazing rate is needed to prevent algal overgrowth of coral. Using the conclusions of Fox and Bellwood (2013) from their study of surgeon-, parrot-, and rabbit-fishes on the reefs of Lizard Island, explain how the complementarity or selection model best explains enhancement of function by the presence of a diverse herbivorous reef fish assemblage.

All three families have some overlap in the species of algae consumed, but the rabbitfish is capable of consuming algae in crevices that the other families cannot reach. This results in niche partitioning, with the fish polyculture consuming more algae than could any dominant algal consumer if present as a monoculture. With the polyculture a broader set of resources is consumed, supporting the complementarity model. The selection effect is unlikely to function here as morphological and behavioral differences between the fishes would leave at least some algae, be that species or algae in certain locations, less vulnerable to herbivory such that the best monoculture would have lower ecosystem functioning than the polyculture indicating transgressive overyielding. The system is transgressive because the polyculture has superior ecosystem functioning than the best monoculture. Overyielding results from the polyculture having superior ecosystem functioning than the average of all of the monocultures of the species present.

How did cordgrass act as a foundation species in the Altieri et al. (2007) study of cobble intertidal habitats?

Altieri et al. (2007) substrate stabilization and protection from solar stress. Some species benefitted from shading as evidenced from higher abundance when the grass or artificial shading was provided relative to shade free conditions. The importance of stabilization was clear when species benefitted from the presence of the grass, which stabilized the substrate, but not artificial shading, which provided no stabilization.

The adjusted R2 value for the effect of the Bakun Index on mussel recruitment is 0.571, what does this mean?

Approximately 57% of the variation in mussel recruitment, at the sites and times studied, can be explained by variation in the Bakun Index Values.

Where would you most likely find azooxanthellate hermatypic corals dominating coral reefs?

At depths where net photosynthesis does not occur, for example Lophelia pertusa forms extensive reefs, mostly from 200 to 1000 m depths, mostly known in the Atlantic, but has also been recorded in the Pacific and Indian oceans.

Discuss how intertidal organisms can avoid desiccation during low tides.

Bivalue can tightly close their impermeable shells, others mollusks, such as Littorina, can seal their aperture to rock using mucus, and some limpets create a home scar on the rock allowing a tight fit for the broad aperture and limiting water loss. Crabs can also retreat to the relatively cool and humid features in rocks. Anemones and coral secrete protective layers of mucus, which is effective for short time period. Many organisms limit loss by clustering together or seeking out microclimates associated with algae that are able to retain water, often through capillary action between numerous fine branches.

Different community structure was observed in the rocky intertidal zone between the two rocky outcrops in the Bay of Blazing Sun. One of the sites sits fully exposed to the sun and the other is protected from strong sunlight by the BBSCW Resort Building. What are some differences in interspecies interactions you might expect to find when you go out to compare these sites?

At the exposed site temperature stress may provide some species from surviving on fully exposed surfaces in the mid and upper intertidal zone, which may lower the strength of interspecific competition. This is assuming that recruitment is sufficient, such that nearly all the available space should otherwise be occupied. Some of the species that can survive on their own at the shaded site, may require a commensal relationship with another species to survive in the exposed site (for example at the exposed site a barnacle may only be able to survive in association with a canopy forming algae that facilitates survival of the barnacle by providing shade and a moist microclimate, helping to prevent desiccation).

Different community structure was observed in the rocky intertidal zone between the southern headland of the Bay Crushing Waves and a rocky outcrop just inside of the Bay which is protected from waves by the nearby headland. What are some differences in interspecies interactions you might expect to find when you go out to compare these sites? At which site might you expect more of the surface of the rock to be covered by sessile animals? Deep thinking is required here, as I have not really helped you out with this question yet.

At the exposed site the crashing waves could prevent activity by predatory crabs and seas stars, and perhaps even welks, allowing sessile and sedentary, such as muscles, barnacles and limpits to thrive in the absence of predation. Animals and plants may the occupy all of the space on the rock and intense competition, potentially leading to competitive exclusion may result.

The seastar Pisaster ochraceus is often described as a keystone species in the Pacific Northwest because it is able enhance biodiversity by keeping the mussel Mytilus californianus from monopolizing space in the lower portion of the middle intertidal zone. You hear that in some sites in Southern California predation by similar densities of the long-lived Pisaster lowers rather than enhances diversity, explain how this might occur given what has just been presented.

Because of lower rates of exclusion, competitive exclusion by Mytilus may not occur at some sites in southern California. With fewer prey and equivalent densities of predators, some species may be severally reduced or even locally excluded by Pisaster. Post-recruitment processes such as predation and physical disturbance can only enhance diversity if they act to keep a lower trophic level species, such as Mytilus, from competitively eliminating other species.

Describe and name Behrenfeld's (2010) challenge to Sverdrup's model of primary production in detail.

Behrenfeld's Dilution-Recoupling hypothesis focuses more on top-down control on the phytoplankton growth rate (r). He observed positive growth rates throughout the winter and negative r values during the summer when phytoplankton were subject to strong grazing pressure. As the WMD moved deeper into the euphotic zone in the late summer and early winter predator-prey encounter rates were not initially impacted and r remained negative. The transition from negative to positive growth rates of phytoplankton occurred when the wind-mixed depth had descended below the euphotic zone in the late fall to early winter incorporating a large volume of nutrient rich but relatively grazer free water resulting in the dilution effect. This initiated the positive growth phase for phytoplankton. The reduction in predator-prey encounter rates due to dilution reduced phytoplankton losses from predation more the reduction of phytoplankton growth rates in response to lower light levels (the death rates decreased more than the birth rate shifting r (b - d) from negative to positive). As the WMD shoals in the spring, decoupling of grazing pressure by dilution ends (recoupling), but r remains positive well into the spring because of light-driven increases in phytoplankton production. Maximal phytoplankton biomass per cubic meter occurs in the late spring and is followed by the termination of the bloom by surface nutrient depletion or overgrazing.

Explain Trait-Mediated Indirect Effect or Interaction (TMII) in the context of the green crab Carcinus, the herbivorous snail Littorina, and green algae in New England.

Chemical cues from Carcinus inform Littorina of the crab's presence, and at least some of the Littorina either move away from that region of the intertidal or reduce their foraging activity. These non-consumptive effects of Carcinus on Littorina relives top down pressure on algae snd in response the algal cover increases.

Under what conditions might disease either delay or accelerate competitive exclusion?

Competitive exclusion might be delayed if the superior competitor is the sole host or is more susceptible to the disease. If however, the superior competitor is more tolerant to the disease, then sympatric competitors exclusion may be accelerated. The top-down control must impact the superior competitor more than the inferior competitor or competitors.

What is meant by psueudosaturation?

Concluding inappropriately due to undersampling on small scales that there is an asymptotic or curvilinear relationship in the regional to local species comparison. Falsely suggesting that small scale species interactions were capping local species richness.

Black abalone populations impacted by the withering syndrome so not appear to be benefiting from recruitment of larvae from populations only 10s of km away. Provide three possible explanations. (one needs more explanation than the others)

Continuing presence of the disease, they are outside of the effective dispersal kernel, and lack of appropriate habitat for settlement as intertidal community structure has shifted from bare rock and crustose coralline algae (which is good for abalone) to one dominated by sessile animals and sea urchins.

Explain how zooxanthellae and corals are mutualists in terms of energy production. How does each benefit?

Coral metabolism provides ammonium and carbon dioxide to the zooxanthellae. Other nutrient needed by the dinoflagellate are obtained by seawater in the coelenteron, or external sea water. The algal populations within the host coral grow until they reach a certain density, after which the zooxanthellae provide their host with a variety of compounds including glucose, glycerol, and amino acids, which are products of photosynthesis.

Describe how Dayton (1975) demonstrated the effects of herbivory and competition on the macroalgal community at Amchitka Islands in the Aleutian Archipelago.

Daton observed a decrease in the percent cover of the kelp Laminaria at Amchitka Island from 100% at a depth of 10 m to 0 at 20 m. Though the kelps can grow in the absence of herbivory down to 30 m, the observed kelp distribution was attributed to the 20 m maximum foraging depth of sea otters and an increase in urchin densities from depths of about 16-22 m. These datas suggest strong top down pressure on sea urchins in relatively shallow waters, and strong top down pressure on Laminaria at the deeper end of its distribution. When Laminaria was experimentally removed, Agorham increased to 100% cover from depths of 8-19 m after which it declined off rapidly to 0% coverage at 23m. This suggests that Laminaria was the superior competitor and that Agorham a relatively deep water refuge from competition with Laminaria where otters were not able to effectively control urchins, and also that the urchins strongly preferred feeding on Laminaria over Agorham.

How much of a problem for Southern sea otters are parasitic pathogens such as the apicomplexan Toxoplasma gondii, how might the pathogen get inside of the otters, and how might the disease lead to indirect mortality?

Disease may be directly or indirectly responsible for 40% of southern sea otter deaths, impeding population recovery. Apicomplexan pathogens in the genus Toxoplasma and Sarcocystis are the primary cause of death for about 23% of otter losses to disease. Otters may be consuming infected snails that ingest the oocyts trapped in biofilms on kelp when grazing. Sick otters with moderate to severe encephalitis were 3.7 times more likely to be attacked by sharks than healthy otters and are more vulnerable to other direct causes of mortality.

For estimating the FST resulting from drift and dispersal using the island model FST = 1/(4Nem + 1). What does Ne refer to? m? What is the range of values for FST? What do high FST values suggest?

Effective population size (number of breeding adults). 0 to 1. High FST suggests small population size and/or migration rates, this corresponds with high genetic differentiation between populations. Opposite for low values.

Transgressive overyielding for biomass consumed per unit time was observed with a diverse assemblage (5 species) of generalist predators preying on snails, chitons, and barnacles in an intertidal zone. Two of the predators were co-dominants at that trophic level. Given that the resource was not partitioned, how can we explain the finding of transgressive instead of nontransgressive overyielding?

Even though there is complete dietary overlap, there can still be complementarity if one predator is, for example, better at opening barnacles and the other is better at handling chitons. Selective focus on a prey species a predator is most efficient at consuming, allows the more diverse assemblage to consume more prey biomass per unit time than the average monoculture (overyielding) and also better than the best monoculture (transgressive overyielding).

Why is a thin wake better than a thick wake?

Fewer eddies are created, resulting in a smaller volume of relatively low pressure, reducing pressure drag.

What did Mass et al. (2010) determine regarding flow and production in a species of coral, seagrass, and macroalgae?

Flow enhances the transfer of oxygen from the organism to the water, decreasing the likelihood of photorespiration, which is oxygen binding with Rubisco rather than carbon binding with Rubisco. Photosynthesis at least doubled in flow relative to no flow treatments for the coral, algae, and seagrass. Similarly respiration decreased by nearly fifty percent or more in the presence of flow relative to stagnant conditions. They concluded that flow is a key factor, determining production in benthic marine communities.

How are virioplankton dynamics related to annual cycles of their physical and biological environment in the North Atlantic subtropical gyre?

Following the onset of the water column stratification in the spring Prochlorococcus experience a bloom below the mixed layer depth. The virioplankton populations appear to increase in response to their host Prochlorococcus population in a manner suggestive of bottom-up control.

What are foundation species?

Foundation species are those that create habitats and modify the environment with positive effects on the diversity, distribution, and/or abundance of associated organisms.

What latitudinal trend in species richness did Witman and friends observe for rock wall communities?

Greater regional diversity at lower latitudes with warm water. The Galapagos fauna was an outlier for the expected pattern, with a lower regional diversity than for example Poloa, which is also near the equator.

Under what conditions may kelp deforestation occur?

Herbivory often attributed to sea urchins that may have been released from top down control through the overexploitation of their predators. Diseases which might be facilitated by physiological stress brought on by high temps and/or low nutrient anomalies. Nutrient stress that may occur along with el nino associated high temperatures, depressed thermocline, and strong storms.

Discuss the role of heterotrophic dinoflagellates as phytoplankton grazers relative to copepods and other metazoans. Describe the ability of some to feed on chain forming diatoms that are larger than themselves.

Heterotrophic dinoflagellates are considered to be typically more important grazers of phytoplankton biomass than copepods and other metazoan grazers. Some are capable of consuming chains of diatoms larger than themselves by using the elastic properties of their bodies to extend over diatom chains more than twice the length of the un-distended dinoflagellate. Others employ a pallium, a highly plastic membranous organ that extends out of the dinoflagellate and can accommodate relatively large chains of diatoms whose protoplasm is liquefied and transported into the dinoflagellate.

De Wit and Palumbi (2013): What might some marine populations require to survive the continuing global change our planet is experiencing? What types of organisms may be particularly vulnerable to changes to ocean water? (short paragraph)

High levels of genetic variability may provide some protection in the face of global change. Encouragingly at least some abalone have genes increasing fitness in low pH water, even though their populations may not have experienced such conditions for a very long time. Calcifying organisms are likely to be particularly vulnerable to acidification due to increased metabolic costs in shell creation and in extreme cases shell erosion.

Name and describe the function of the 5 kelp anatomical features discussed in class.

Holdfast-anchors the algae to the substrate Stipe- the stock of the alga arising from the whole fast Blades- structures analogous to leaves primarily functioning for photosynthesis Sporophyllus- specialized reproductive blades at the base of some species Pneumatocyst- gas filled float from which the blades arise and of course everything coming up from the hold fast can be referred to as the frond

What were the conditions needed to effect the forward shift from stable kelp forests to urchin barrens in Tasmania? What conditions were then needed to effect the reverse shift resulting in the reestablishment of kelp forests? What term do we use to describe the relatively large magnitude difference between these tipping points?

In Tasmania kelp forest urchin densities of 2 per m2 were sufficient to effect a forward shift from a stable kelp dominated to a stable urchin barren state. To effect the reverse shift back to a stable kelp forest state, urchin densities needed to be reduced by an order of mag to 0.2 per m2. This large difference in the environmental conditions resulting in the forward and backward shifts called a hysteresis, over which each of the alternative state can exist in nature.

What relationships between flow and species richness did Palardy and Witman (2011) observe?

In both Maine and Alaska they found significantly greater species richness on settlement panels in enhanced flow relative to control panels. In both Alaska and Paloa, species richness of subtidal benthic invertebrates increased as flow increased in natural communities.

What two physical changes associated with global change made it possible for the urchin Centrostephanus rodgersii to colonize the coast of eastern Tasmania from populations in New South Wales, Australia?

Increased sea surface temperatures and current flow in the Eastern Australian current. The waters off Tasmania are recognized as a global hotspot, where temperatures have increased at a rate four times the global average. Sea surface temperatures have risen above 12 degrees celsius threshold for larval development of C. Rodgersia off eastern Tasmania. Increased southernly flow facilitated the movement of larva across the Bass Strait to Tasmania.

What are two hypothesized benefits of multi species mass spawning events for corals?

Individual species can benefit through maximum fertilization success and the coral community can benefit from greater propagule survival by overwhelming their egg predators with more than they can possibly consume.

The King of the atoll archipelago of Coral Paradise decided to diversify the nation's economy by allowing commercial fishing and saw little impact on the environment. So he then allowed collecting reef animals for the aquarium trade and still saw little impact. Then came shrimp farming and increased nutrient pollution from the resorts that lined the coasts. His chief of environment (his niece) advised that the reef systems showed signs of stress with more coral disease, less coral cover, more algae, and dramatically fewer fishes and invertebrates that are good for crafting and salt water aquariums. The good King assembles his trusted advisors (relatives and rich owners of fishing boats, shrimp farms, and golf courses) who smiled and said, "let's not be hasty here, there is still plenty of coral for the tourists to see." Six months later a wasting disease devastated the large herbivorous sea urchin populations and a year after that coral cover decreased by 40% and was still declining. Explain what happened using a theory based on a mathematical model; include some good jargon and a graph with well-labeled axes.

Initially the reef had high functional redundancy, such that reduction in some grazer populations could be made up by increases in others. Here the system could be represented by a Michaelis-Menten or power function, with high functional diversity of macroalgal grazers. As conditions deteriorate the preexisting functional redundancy of the system continuous to buffer the community against loss in ecosystem function. Eventually loss in habitat, nutrient enrichment, and fisheries pressure begins to have obvious affects on invertebrate and fishes, though coral cover remains robust with urchins everywhere. Finally the near elimination of the last important macrograzer results in a rapid phase shift from coral to algal reefs. Loss of functional redundancy lowered the resilience of the system, preconditioning the reef for the phase shift.

Why would the rocky intertidal zone be a good system to use for studying community ecology, and what types of data would you likely gather?

It has steep vertical gradients in environmental conditions, and is largely inhabited by organisms that are small, sessile, or sedentary, often reach high density and are easily to manipulated. Species diversity, richness, composition, abundance, distributions, size, biomass, recruitment and tropic interactions.

How does high wave action benefit corals?

It helps keep the water well oxygenated, reduces sediment accumulation on the corals and increases the flux of nutrients and zooplankton prey.

Karenia brevis produces toxins because of natural selection, not due to some all-consuming hatred of metazoans. Why might it produce the toxins and what evidence has been provided to support this hypothesis? (be sure to use define and name the ecological principle).

Karenia brevis is a photosynthetic planktonic dinoflagellate who's toxins suppress growth or cause death of four of the five co-occurring phytoplankton species tested. These finding support the hypothesis that Karenia braves is engaging in allelopathy, chemical suppression of competitors.

Some are concerned that marine reserves will enhance predators at the expense of herbivores. Which herbivores are likely to be among the most important for suppressing macro algae and why may their numbers be either diminished or enhanced in effective marine protected area?

Large bodied parrotfish are thought to be the most important grazing fish on some reef systems. They can achieve a refuge in size from many predators, diminishing top down control on them. Losses from predation are unlikely to become more than compensated for by protection from fishing.

Provide a thorough explanation for Hypothesis 2 from the previous question.

Large female COT are highly fecund, so a small increase in larval survival and settlement could lead to huge population increases. If river flood coincide with the COT spawning season, the dramatic nutrient spike associated with the floods could lead to a sixty fold increase in COT recruitment. Further evidence for this hypothesis is that outbreaks tend to spread downstream from large rivers. Such bottom up explanations may be needed to initiate outbreaks, but the persistence of some outbreaks might be better explained by top down effects, such as human caused reductions of fish and invertebrate predators of juvenile COT starfish.

What was responsible for the greater genetic differentiation of the anemone fish Amphiprion clarkia on Leyte island relative to Cebu island?

Larger populations sizes on Cebu increased the size of the dispersal kernel, which corresponds to a relatively lower slope with the relationship FST divided by 1-FST and the distance between populations. It was concluded that more effective dispersal resulting from larger population sizes, resulted in less genetic change with distance, less isolation by distance.

What caused the nearly complete loss of kelp and macroalgae in the Gulf of Maine, and what allowed those foundation species to eventually recover?

Loss of cod in the gulf of Maine reduced top down control of urchins resulting in increased urchin abundance and top down pressure on macro algae. The kelp forests largely vanished until the development of an urchin fishery that drove the urchins to very low abundance. As herbivory declined the percent cover of fleshy algae increased from less than 5% to about 80%.

Explain the alternation of kelp forests and urchin barrens off the coast of Nova Scotia since 1965.

Loss of cod off Nova Scotia reduced the top down control of urchins resulting in increased abundance of urchins, and the near disappearance of kelp forests. Currently warm water events are associated with outbreaks of disease that eliminates urchins to a depth of 30 meters, allowing reestablishment of the kelp forest. The kelp subsequently declines as urchins present in deep water refuge from the pathogen re-established shallow water populations, once again causing severe declines in kelp. Two such urchin disease cycles have been observed.

How did Ling et al. (2009) demonstrate alternate stable states between kelp forests and urchin barrens?

Macroagal cover versus Centrostephanus rodgersii density in Eastern Tasmania indicates only kelp forests in the absence of the urchin and only barrens with urchin densities above 5.5 urchins per m2. At intermediate urchin densities either community can exist indefinitely. If the reef system occurs in the kelp state, but close to upper threshold value, a slight increase in sea urchin density may induce a catastrophic forward shift to the alternative and stable sea urchin barren state. Once barrens have formed, reverting back to the kelp state is difficult, because the system demonstrates hysteresis and the reverse shift occurs only if sea urchin densities reduced below another threshold at a much lower urchin density than was required to effect the forward shift.

Watson et al. 2011: The potential connectivity matrix for kelp bass predicts strong dispersal from the mainland to the southern Channel Islands, but the realized connectivity matrix predicts much weaker dispersal. Why?

Mainland source populations are relatively small do there are fewer dispersing larvae, which combined with mortality during the larval period, decreases realized connectivity.

Why is it so difficult to get a good estimate of the total metazoan species richness on coral reefs?

Many animals hide, are very small, and reside in cracks and crevices on the reef. Species of coral reef cryptofauna are often represented by only a single individual in samples, suggesting that many other species remain undetected, resulting in underestimation of species richness.

How might trophic relationships link coral reefs with algal and seagrass beds (all foundation species) growing in the sands between the reefs? How might the relationships differ in and out of effective marine protected areas?

Many herbivorous fishes and invertebrates shelter from predators on the reef and limit predation risk by foraging close to the refuge. Effective MPAs with healthy upper level predator populations are likely to provide the stimulus for risk sensitive foraging, restricting foraging to relatively close to the reefs, resulting in foraging halos. Heavily fished reefs with depleted predator populations may result in grazers foraging farther from the reefs, resulting in great reductions in algal or seagrass cover and absence of distinct vegetation free halos around refugia.

What is the whale pump? Where does it operate, and how is it hypothesized to affect primary production by phytoplankton and secondary production by krill?

Many whales feed at depth, effectively transporting large amounts of potentially limiting nutrients, such as nitrogen and iron, back into the euphotic zone in the form of feces and urine. Some think that this can effectively fertilize hotspots of production where whales feed, stimulating further phytoplankton growth that can feed krill populations compensating for some of the consumption of krill by whales in the southern ocean.

Explain why Reed et al. 2008 reported lower seasonal variation in net kelp forest primary production than in seasonal foliar standing crop of kelp. Explain the difference.

Net kelp forest primary production was generally greater in summer months primarily due to the greater fully or standing crop, the kelp biomass minus holdfast and sporophyllus. Despite a large decrease in full year standing crop in the winter net primary production decreased only modestly, in spite of lower winter irradiants due to higher specific growth rate, the mass specific growth rate, which was due to less self-shading associated with decreased fully or standing crop.

You study several other systems in which Nucella is the only important predator and a similar species of Chthamalus is the prey. No development (or evolution) of bent morphs is seen, provide an explanatory hypothesis for this apparent failure of evolution.

Nucella uses a different mechanism, a ragular drill to open the shell, so the bent morph offers little protection.

As a youth in Pacific Grove California back in 1930 your great uncle Fester liked nothing better to take random transects in the intertidal zone and record data on species abundance. At a family reunion in 1990 he takes you back to his old sites and is stunned to find the relative abundance of many species has changed. Describe the change he observed and how it may have come about by describing changes in mean and critical values of environmental parameters.

Over the 60 year period, species with more southernly distributions were likely to experience significant increases in abundance, while those with more northerly distributions were likely to decrease in abundance. Over this period the mean coastal sea water temperatures increased significantly, as did the maximum values, increases in the minimum value were minor. The increase in mean temperatures shifted the probability distribution of temperature to warmer values, decreasing the likelihood that organism will experience critical low temperatures, and increasing the likelihood they will experience critical high temperatures. The maximum temperatures organisms may experience, at Fester sites, will increase to values not previously experienced at that location. The increased likelihood of extreme high temperature events is a likely cause for the observed change in distributions. Species with more southernly distributions would be more likely to survive such extreme events than those with more northerly distributions, who are less well adapted to warmer temperatures now occurring at Fester sites.

Aside from climate change how have humans facilitated the negative impact of Centrostephanus rodgersii off eastern Tasmania?

Overfishing of the lobster Jasus edwardsii has effectively eliminated top down pressure on the invasive urchin, reducing ecosystem resilience to the climate driven threat of sea urchins. Together these anthropogenic stressors increased the risk of a catastrophic shift to widespread urchin barrens.

Name the two most likely hypotheses for explaining how Acanthaster planci outbreaks come about.

Overfishing- The predator removal hypothesis and Enhancing larval recruitment contributes to outbreaks. Eutrophication or terrestrial runoff hypothesis.

Is Macrocystis pyrifera best described as annual or perennial? Explain.

Perennial- the fronds may be torn off during winter storms, but it is regenerated in the following spring and summer The stipes typically live for 4-6 months, and the holdfast for up to 5 years.

Along the Pacific coast of Chile upwelling-favorable winds are generally weaker, but more persistent throughout the year north of 32°S, yet recruitment of mussels and barnacles and % cover of those species is greater in the South as are interspecific interactions. How can this be explained?

Persistent upwelling can result in the offshore loss of larva and phytoplankton, reducing recruitment in food supply to the intertidal zone. In the south high recruitment and higher concentrations of phytoplankton appear to be associated with the relaxation of upwelling. High recruitment coupled with abundant food may enhance larval production through increased adult density and fecundity. High density can make competition and top down effects more common in the south.

Complete the sentence: The ability of eurythermal coral species to exist over broad geographic ranges may be a result of adaptations linked to ...

Phenotypic and genetic diversity of both coral and their endosymbiotic zooxanthellae.

Describe the phycosphere and the relationships between organisms interacting in the phycosphere.

Phytoplankton release organic compounds resulting in a region of enhanced solute concentration, called the phycosphere around their bodies. This nutrient depleted mucus may adsorb nutrients from the surrounding bulk fluid resulting in the development of a rich gel medium. Bacteria use chemotaxis to swim towards and inhabit the phycosphere, and it's thought that the phytoplankton may be able to release compounds that attract beneficial bacteria and deter or even kill harmful bacteria. Beneficial bacteria benefit from dissolved organic matter, and perhaps other compounds released from the alga. These bacteria benefit the alga by increasing the availability of vitamins and bioavailable forms of nitrogen and iron. Parasitic bacteria may be most effective when the alga is nutrient stressed and less capable of producing compounds that deter or kill them.

How do planktotrophic and lecithotrophic development differ?

Planktotrophic larvae need to feed to complete development, lecithotrophic larvae do not.

Watson et al. 2011: All habitats are apparently not created equally. Discuss the relationship between fraction of the coastline in the Southern California Bight and successful recruitment of the fishes and invertebrates studied. What are the implications of this?

Populations with higher reproductive output are more likely to disperse larvae to other populations. For 7 different species studies they found on animals that about 10-20% of the coastline were responsible for 50% of successful recruits in the Southern California Bight. The maintenance of viable metapopulations may require protecting some source populations with are probably those same populations fishers want most to exploit.

How does the Bakun Index relate to upwelling?

Pressure gradient fields are used to derive wind patterns, which are then superimposed on oceanographic features, and used to predict the likelihood of upwelling and/or downwelling events.

Gerlach et al. 2007: The cardinal fish Ostorhinchus and the damselfish Pomocentrus both had pelagic larvae but the FST value for Ostorhinchus was about 0.02 and the FST value for Pomocentrus was zero. Why? What types of cues could the late-larval fish use to locate and move to reefs? How could they effect movement towards reefs?

Promocentrus demonstrated no preference for recruiting on their natal reef, but such a preference was observed for Ostorhinchus. Smell and sound are likely cues used to move toward reefs. Use of down current retention eddies behind reefs, onto genetic vertical migration in stratified current and micronekton swimming towards the currents, may have helped with retention and recruitment of Ostorhinchus.

What are two major localized rather than global threats to shallow coral reefs that were discussed today and one major localized that was discussed in a previous lecture.

Sedimentation from agriculture and clear cutting of forests. Eutrophication from agricultural fertilizers and sewage as discussed previously reduction of herbivores by overfishing and disease.

Thoroughly explain the concept of "sleeping functional groups" using Platax pinnatus as an example.

Sleeping functional groups refer to species or groups of species that can fill a particular functional role, but do so only under exceptional circumstances. For example in a study of the GBR thick strands of large macroalgae developed in herbivore exclusion cages. When the cages were removed, exposing the macroalgae to reef herbivores, the batfish Platax pinnatus, a species not known to be herbivorous, was primarily responsible for reversing the phase shift in the cages where the algae outcompeted coral. The parrotfish that were largely responsible for preventing such phase shifts on the reef, played a minor role in the phase shift reversal. This observation highlights how little we know about the potential value that species may have in terms of ecosystem services and provides additional evidence for the value of the preservation of biodiversity in general.

Contrast the social structure and population connectivity between the spinner dolphins in the far NWHIs and those off Kona. Provide a possible explanation for the differences.

Spinner dolphins found off Kuri and Midway form long-term stable groups, in contrast those off Kona that frequently change from one day resting social group to another. FST values indicate frequent gene flow between Kuri and Midway, while the Kona population is genetically distinct from all islands and atolls that were studied within the archipelago. Limitation of resting and food places on the small atolls on the far NWHIs results in small populations and higher rates of migration due to resource competition and to lessen inbreeding.

Describe the Sverdrup model of primary production (made specifically for the North Atlantic Ocean).

Sverdrup's model of primary production involves periods of limitation either by light or nutrients, separated by periods of high production with ample light and nutrients. The key physical components in the model are the wind-mixed layer depth and the critical depth, the depth at which the total water column gross photosynthesis and respiration are equal when averaged over 24 hours. Assuming that all cells are well circulated throughout the wind-mixed layer, gross photosynthesis will exceed respiration (over 24 hours) when the critical depth is below the wind-mixed layer. During the winter strong winds drive the wind-mixed layer below the critical depth mixing nutrients into the surface waters and ushering in a period of light limitation. As the sun moves higher in the sky photoperiod increases in the spring and the critical depth moves deeper in the water column. At the same time decreased winds result in a shoaling of the wind-mixed layer such that it rises above the critical depth ending the period of light limitation. This along with winter mixing which delivered abundant nutrients to the surface waters results in the spring bloom. With the onset of summer conditions, the water column is further stabilized, and a period of nutrient limitation begins. Increasing winds associated with fall storms results in the wind-mixed layer moving deeper which mixes higher nutrient water into the surface layer resulting in a pulse of high productivity that is smaller and of shorter duration than the spring bloom. The fall bloom ends when increased mixing forces the mixed layer below the critical depth causing a winter associated period of light limitation.

Explain the results of Konar and Estes (2003) in terms of alternate stable states.

The Aleutian Islands from depths of 8-13 meters, there Konar & Estes observed abrupt transitions from encrusting coral and algal communities to kelp beds. The coraline algae dominated habitats supported high densities of urchins and very few algal stipes. Only 25 cm in the kelp bed, urchins were much less abundant, folios red algae covered from about 5-15% of the substratum and the mean density of brown algal stipes exceeded 20 per m2. The differences were attributed to the inability of upright algae to avoid consumption in the urchin dense coarline zone and within folios algal zone, turbulence induced algal abrasion prevented urchins from entering the kelp bed.

What unique ability is only found among the canopy forming species of brown algae?

The ability to translocate photosynthate using specialized cells called trumpet hyphae.

What happens when whales die and sink to the bottom of the oceans. What organisms/communities to their bodies support? How are these systems potentially affected by whaling? How might climate change be affected by whaling?

The carcass goes through several stages of exploitation beginning with the mobile scavenger stage in which large fish and invertebrates consume the soft tissues from the skeleton over many months, sometimes taking nearly a year. This is followed by an enrichment opportunistic phase in which locally enriched settlements are exploited by a small number of species that occur in high densities. This is followed by the species rich sulfophilic stage in which chemosynthetic organisms utilize the hydrogen sulfide produced by anaerobic bacteria exploiting the lipid rich contents of the bones. This stage lasts several decades, after which the remains enter their final stage as a hard substrate reef habitat. Severe reduction of great whales by commercial whaling has also dramatically reduced the number of whale falls to deep sea, potentially leading to extinction of obligate whale fall species. Species occupying relatively small numbers of whale carcasses pre-exploitation are particularly vulnerable to the loss due to the loss of some effective metapopulation functioning.

What is arguably the most important region in the world for coral reefs and associated organisms in terms of species richness and diversity? Name three of the six countries found there.

The coral triangle. The six coral triangle countries, known as the CT six, are Indonesia, Malaysia, Papua New Guinea, the Philippines, Solomon Islands, and Timor-Leste.

Coral Bleaching Hotspots highlight regions where the SST is currently warmer than the ...

The highest climatological monthly mean SST for that location.

DHWs show how much heat stress has accumulated in an area over the past 12 weeks (3 months). The units for DHW are "degree C-weeks", combine...

The intensity and duration of thermal stress into one single number.

In the early 1980s a wasting disease dramatically reduced population of the herbivorous sea urchin Diadema antillarum in the Caribbean leading to increases of algal cover on reefs at the expense of coral. How can this have happened, how is it that this humble urchin was the linchpin holding the whole ecosystem together?

The loss of Diadema left the system without any major macro-herbivores, there was no functional redundancy. Prior to the disease outbreak many regions of the Caribbean had suffered from overfishing of herbivorous fish and nutrient enrichment. These precursor events lowered the resilience of the systems, preconditioning them for a phase shift from coral to algal dominance. The hurricane may have accelerated this process by providing additional substrate for algal growth.

Cornell et al. concluded that a previous study that found a curvilinear relationship between local and regional richness was wrong because (two reasons).

The other study failed to sample most of the species-rich region in the west-central Pacific hot-spot and it under sampled richness on small scales.

As a marine biologist working for the Nature Conservancy you are asked to provide a succinct, one paragraph cost/benefit analysis of leaving a mangrove system intact vs. conversion to coastal shrimp aquaculture facilities. Produce such a paragraph including a variety of benefits from intact mangals as well as costs associated with such aquaculture. Consider also how the local population my benefit and suffer from the conversion.

The replacement of mangrove systems with shrimp farms provides easily quantifiable income streams in coastal communities, but comes with costs, many of which are less easily quantified. Mangals provide nursery grounds for a variety of exploited fish and invertebrates that recruit to offshore populations. The biomass of these animals and those caught directly in mangals is substantial, so pond creation results in a loss of nutrition and income to local villagers. Shrimp ponds pollute the local environment, while mangals act as biofilters, helping to keep coastal waters clean. These systems also help prevent coastal erosion and broad mangrove swamps have provided significant protection to villages from tsunamis and cyclones. In addition to food, mangals also provide timber, fuel, carbon sequestration, and economic value from tourism and recreation.

How did Gaylord et al. (2013) explain enhanced urchin recruitment in conditions of high turbulent shear?

The turbulent shear associated with the rocky intertidal habitat of the adult urchins stimulated an acceleration in the change from precompetent larvae to competent larvae. Which then responded positively to chemical settlement inducers.

A 90% reduction of the black abalone populations in Southern California may render those populations functionally extinct even if the disease were to magically disappear. Why would this be so? After all other populations such as the Northern Elephant Seal have gone through very severe population bottleneck and recovered?

These animals are broadcast spawners and will likely suffer from an allele effect following such a a severe decline. Males and females will be present, but often not close enough for effective fertilization.

Total production of Macrocystis within a kelp forest is dependent on what to factors?

Total kelp biomass in terms of fully or standing crop, which is the mass minus hold fast and sporophyllus, and specific growth rate, the rate at which new kelp tissue is produced per unit of existing kelp tissue, the mass specific growth rate.

In the late 1970's and 1980's two major hurricanes and a wasting disease dramatically reduced population of the herbivorous sea urchin Diadema antillarum on Caribbean reefs resulting in substantial coral loss and a subsequent increase in algal cover. Explain how variation in grazing intensity following such disturbances could lead to alternate stable states, one dominated by coral and the other macroalgae. Explain the hysteresis.

Two major hurricanes in the Caribbean occurred at a time when grazing fishes had been severely reduced on many reefs and at a time of a population crash of herbivorous urchins due to disease. The physical disturbance caused by the hurricanes made more substrate available for coral and/or algal growth when herbivorous fish were depleted by overfishing, but urchins were still numerous. Following the near elimination of urchins by disease, the few grazers remaining were unable to prevent a phase shift from coral to algal dominance. What occurred was a fold catastrophe, in which the system shifted from one stable state to another. Effecting the shift back to a coral dominating state would require larger populations of grazers than were present prior to the phase shift, to effectively graze the much increased mass of macroalgae. This demonstrates the hysteresis characteristic of such phase shifts, where returning to the pre-disturbance grazing rate in the absence of physical disturbance alone is insufficient to reverse the phase shift.

Russell and pals suggest that studies indicating that the most important driver of local species richness is regional species richness are sometimes wrong because....

Two many of the included species are non-interactive and thus competitive elimination, or suppress by predation or other types of interspecific interactions do not influence the outcome.

How are recruitment and ecological rate processes (such as top-down and bottom-up effects related), and how are they influenced by upwelling intermittency?

Upwelling intermittency appears to promote primary production by providing nutrients, while limiting offshore loss of both phytoplankton and larva. The result is enhanced recruitment and growth at high intermittency values, both bottom up effects. Competition and predation will only be factors when prey populations reach sizes in which they begin to interact (compete), and provide food for large predator populations (also potentially recruitment limited), which can in turn regulate prey populations by for example, applying top down control on potential competitive dominance, potentially enhancing biodiversity.

What three methods are used by various species of coral for suspension feeding?

Use of nematocyst laden tentacles, Tentacular grabbing, Ciliary mucus feeding

How might phages both enhance primary production in the surface waters and increase the efficiency of the biological pumps sequestering of carbon in the deep ocean?

Viral lysis of both heterotrophs and phytoplankton cells create dissolved organic matter, that is relatively enriched in nitrogen and phosphorus, and particulate organic matter, that is relatively enriched in carbon. The dissolved nutrients are rapidly cycled in the euphoric zone, while much of the particulate carbon rich material sinks to the sea floor, contributing to the biological pump.

How do proximity of mangroves swamps and seagrass beds to coral reefs enhance fish abundance (and perhaps diversity) of nearby coral reefs above what might be seen if the mangals are absent?

With both nursery habitats, some juvenile fish may initially use seagrass beds and then move to mangroves to continue development. Without the mangroves the juveniles recruit to coral habitats at a smaller size and lower density, leaving them more vulnerable to predation, possibly resulting in reduced fish biodiversity. Species requiring mangroves for nurseries are likely to be absent or rare.

A temperate lake is partitioned and on one side the richness of phytoplankton is reduced from 40 to 10 species. The other side retains all of the initial species richness (40). Primary production is then measured monthly on each side of the partition over a ten-year period during which the lake experiences gradual warming and variable nutrient input from the stream that feeds both sides of the partition. Describe the relative difference in the level and variability in ecosystem function on each side of the partition. At some point work in the terms insurance hypothesis, and either complementarity or selection. As always, be thorough.

With changing environmental conditions it is likely that the dominant species of phytoplankton will change over time. Given the simplicity of the system, with considerable overlap and resource use, the production of the polyculture is likely to be similar to that of the dominant monoculture indicating the selection model. The species rich side of the lake is more likely to have species present that thrive in all conditions, as predicted by the insurance hypothesis. So the overall rate of ecosystem function, here measured as primary production, should have less temporal variation. A higher overall average rate of primary production, on the species rich side, could result from continuous presence of well adapted species due to high functional diversity or some degree of complementarity, perhaps due to differences in nutrient requirements.

Under what conditions would post-settlement processes be important in determining rocky intertidal community structure?

With saturated larval recruitment nearly all the potentially limiting resource space is occupied. This leads to close contact between individuals in competition for space, which may result in competitive exclusion, unless some other factor such as predation or physical disturbance prevents exclusion, and in so doing enhances biodiversity.

Scheffer et al. (2005) assert that the collapse cod population off Nova Scotia in the early 1900s led to a cascading effect on the food web all the way down to nutrients. Describe the cascade (and give it it's full name).

Without the cod and other large demersal fish their prey, small fishes, crabs and shrimp, increased. Those relatively large populations of small predators had an increased top down influence on their prey, leading to a reduction of large bodied zooplankton. With fewer large bodied zooplankton the phytoplankton standing stock became larger and as a result there was draw down in nutrients. If this analysis is correct this is a far reaching topic cascade.

How do zooxanthellate hermatypic corals differ from azooxanthellate hermatypic corals?

Zooxanthellate hermatypic corals are those that contribute significantly to the framework of the reef and live in a mutualistic relationship with zooxanthellae. Azooxanthellate hermatypic corals do not have endosymbiotic dinoflagellates, though they also contribute to the framework of the reef.