Climate Change and Marine Benthic and Epibenthic fouling communities

by Marina de Castro Deus

The biological interactions between species that live in close relationship with the seabed strongly depend on competition for space. These fouling organisms have different population and individual growth rates depending on local environmental conditions, and temperature increases due to climate change can influence the distribution range and the competitive ability of these species causing different abundance patterns in the community. Due to the difficulty of measuring interactions of these species experimentally, studies often use the latitudinal temperature gradient in order to gather information on individual species populations growth rates in response to the variation of temperature. These results can be used as a good resource for information on species-specific thermal responses, but do not provide information on the possible changes that temperature shifts can have on competitive interactions between marine species. Continue reading

Addressing Climate Change in Australian Marine Ecosystems

by Weronika Konwent

Australia’s diverse marine environment is under threat from varied effects of climate change such as marine heat waves, ocean acidification, floods, and tropical cyclones. Various organisms spanning many habitats are affected, including fish, seabirds, marine turtles, coral, and marine invertebrates, many of which are keystone species that influence the structure of a particular community. It is important to study and understand the impact of ecological changes on the habitat and its inhabitants in order to preserve them as effectively as possible. Continue reading

Do Marine Protected Areas Save Seychelles Sea Cucumbers?

by Neha Vaingankar

Marine protected areas are a major cause of dispute especially in coastal and island regions like Seychelles, off the western coast of Africa. In recent times, tropical regions all over the world have experienced a huge boom in fishing of holothurians (sea cucumbers). Almost all of the holothurian fisheries are considered fully exploited, in decline, or entirely collapsed. The reason for the high demand is for the holothurian’s medicinal purposes as well as its supposed aphrodisiac qualities. In many tropical coral reef regions, locals rely on these invertebrates for their livelihoods. However, due to the density-dependent reproduction patterns and late maturing of these organisms, holothurians are very vulnerable to over-exploitation. Many MPAs were established in Seychelles 20 years ago that pre-date the wave of heavy exploitation in current times. Cariglia et al. (2013) aims to understand the effectiveness of these MPAs and measure the economic value of these holothurians. Continue reading

High and Distinct Range-Edge Genetic Diversity despite local Bottlenecks

 

by Cameron Lukos

The genetic consequences of being at the edge of species ranges has been the subject of much debate. Populations that occur at low latitude ranges are expected to retain high unique genetic diversity. Less favorable environments that limit population size at the range edges may have caused genetic erosion that has a stronger effect than past events. This study by Assis et al. (2013) provided a test of whether the population declines at the peripheral range might be shown in decreasing diversity and increasing population isolation and differentiation. The authors compared population genetic differentiation and diversity with trends in abundance along a latitudinal gradient to the furthest extents of the range of a sea kelp, Saccorhiza polyschides. Assis et al. also looked at recent bottleneck events to determine whether the recent recoded distributional shifts had a negative impact on the population size. They found that there was decreasing population density and increasing spatial fragmentation and local extinction at the southern edge. The genetic data revealed two distinct groups and a central mixed group. As the authors had predicted there was higher differentiation and evidence of bottleneck at the southern edge but instead of a decrease there was an increase in genetic diversity suggesting that extinction and recolonization had not reduced diversity and that this may be evidence of a process of shifting genetic baselines. Continue reading

Elevated Temperatures Increase Toxicity of Copper but Decrease that of Oxytetracycline in a Marine Protozoan

by Emil Morhardt

One aspect of increased ocean temperatures is that they may alter the resistance of marine organisms to pollutants. In a paper just published, such was found to be case for the marine protozoan, Euplotes crassus, that lives on the ocean floor where particulate pollutants get deposited. The protozoans were exposed to two common pollutants—the organic antibiotic oxytetracycline, and the potentially toxic metal, copper—over a range of temperatures. The scientists looked at their effects on survival rate, replication rate, feeding rate (endocytosis) and general of toxic stress (measured as lysosomal membrane stability) all interrelated. Increasing the concentrations of both these toxicants decreased all four measures of protozoan well-being, but in almost all cases Continue reading

Mathematical Modeling of Sea-Ice Extent and Primary Production Shows Changes in Pelagic-Benthic Coupling

Pelagic benthic coupling is one of the most important processes in the Arctic Ocean and relatively little has been done to investigate the effects of climate variability on it.  Pelagic-benthic coupling depends on vertical flux and is influenced by sea ice thickness, extent, and patterns of formation and melting.  Vertical flux is the distribution and transportation of nutrients throughout the water column.  It is determined by primary production, zooplankton feeding, and physical oceanography processes.  Three conceptual biogeochemical models were used to investigate future ecosystem scenarios in the European Arctic Corridor, a region crucial for carbon cycling in the Arctic.  The first looked at climate changes effects on the timing of sea ice formation and melting and the corresponding phytoplankton blooms taking into account water stratification.  The second looked at the same thing but factored in vertical export of the bloom.  The third took into account the three areas of Arctic Ocean: open ocean (alpha ocean), seasonal ice zone (beta ocean), and multiyear ice zone.  Climate change will affect the beta ocean the most, and some areas may even turn into alpha ocean.  There will a longer period with no sea ice overall, which will extend ice algae and phytoplankton blooms.  Primary production will decrease, and this will decrease the yields of fisheries because of less vertical flux. Smaller phytoplankton will flourish.  The remaining vertical flux will be less seasonal in nature because of the dissolution of traditional sea-ice cycles. —Katherine Recinos         
Wassmann, P., and M. Reigstad, 2011. Future Arctic Ocean seasonal ice zones and implications for pelagic-benthic coupling. Oceanography 24, 220–231.

Wassmann and Reigstad state that there has been an ongoing lack of research on the Arctic, especially about pelagic-benthic coupling.  This is because the Arctic is hard to access and pelagic-benthic coupling differs from region to region in the Arctic Ocean and is thus hard to accurately measure in one study.  However, mathematical models have been developed which take biological, physical, and chemical data and create an overall picture for environmental scenarios in the Arctic Ocean.  Wassmann and Reigstad advocate the use of these models, and use three in this paper.  These are either adapted from other studies, or created by the authors specifically for this study.
Climate change will affect the extent of sea-ice in the Arctic which is intrinsically linked to the growth of sea-ice algae.  The importance of this algae depends on the area of ocean in consideration, but it plays a role in vertical flux and as a food for benthic organisms.  If the amount of sea-ice decreases, the blooms of ice algae will shift, leading the water to become more stratified, subsequently decreasing primary production.  This may happen in the Barents Sea.
A lengthening of the season with no sea-ice will lead to earlier phytoplankton blooms as well as ice algae blooms.  This will shift traditional patterns of nutrient consumption by zooplankton and trigger earlier vertical flux.  The vertical flux will be stretched out over a greater time frame which will lead to less pulsed pelagic-benthic coupling but more steady overall levels.  There will not be an increase in nutrients.  
Wassmann and Reigstad discuss alpha, beta, and multiyear ice oceans in terms of a warming climate.  Beta oceans will undergo the greatest changes and possibly adopt the characteristics of alpha oceans.  Vertical flux and productivity will decrease due to stratification.  The authors give examples of further studies to be done including collecting remotely sensed data on phytoplankton distribution and temperature-dependant respiration in areas with slowly increasing temperature.     

Changes in Sea Ice and Advective Flow will affect the Productivity of the Arctic Ocean

The effects of climate change on marine ecosystems in the Arctic have rarely been studied collectively.  As part of the 4th International Polar Year, Paul Wassmann gathered together the results of years of studies to investigate the major effects that climate change is having on arctic marine ecosystems and to postulate what studies could be done to further advance our scientific knowledge of the region.  The basic processes and features of arctic marine ecosystems that will be affected are the seasonal ice zone (SIZ), advective flow and regulation, the relationship between the blooming of primary producers and their consumption by secondary producers, pelagic-benthic coupling, and diversity and distribution of species. Conceptual and coupled physical-biological ecosystem models were used to determine that primary production will increase in certain areas but will remain stable overall, fisheries production will not increase, and that the stratification of arctic waters may actually decrease Arctic Ocean productiveness in the longer term.  Additionally, ice and phytoplankton algae may experience longer blooms which will decrease vertical export of nutrients and change food webs.  Although freshwater advection will facilitate the ability of fish to survive arctic winters, as the ecosystem decreases in salinity, plankton and smaller organisms will prosper. (Wassmann 2011)  To monitor these effects, further research needs to take place in the Fram Strait, the Siberian shelf, and the Central Arctic Ocean.  Studies need to encompass all seasons, and the time series analysis framework is recommended. (Wassmann 2011)—Katherine Recinos  
Wassmann, P., 2011. Arctic marine ecosystems in an era of rapid climate change. Progress in Oceanography. 90, 1-17.

Wassmann begins with an overview of where studies have been done in the Arctic Ocean region.  Most of the major regions, such as the Barents Sea and the Canadian Arctic Archipelago have data available from between two to eleven studies.  However, there is a dearth of knowledge from the Eastern Siberian Sea and accompanying shelf caused in part by the withholding of information by Russia and the general disorganization of studies that have been carried out there.  Of the Arctic Ocean studies that research is available from, the abovementioned processes and features are being effect by climate change: seasonal ice zone (SIZ), advective flow and regulation, the relationship between the blooming of primary producers and their consumption by secondary producers, pelagic-benthic coupling, and diversity and distribution of species.  Many of these processes are intrinsically linked; regional and time variation studies have determined that the SIZ will be affected by global warming, which will change blooming patterns among primary producers, which will then change nutrient distribution among water strata.  This would subsequently affect pelagic-benthic coupling and species biodiversity.  Wassmann gives an example from a study involving Calanus glacialis, a copepod.  C. glacialis depends on the ice algal and pelagic algal blooms for food, and its life cycle is timed according to traditional seasonal patterns.  Pelagic algal bloom is “governed to a larger degree by ice thinning and less predictable ice breakup.”  As the timing of the bloom changed, C. glacialis biomass decreased.  This effect of autotroph blooming on secondary producers is highly variable and can be seen across a number of species. 
Wassmann then describes the effects of advection on the Arctic Ocean.  Water is predicted to enter the Arctic Ocean from two main sources: the warmer ocean further south, and freshwater rivers.  This has the dual effect of increasing water temperature and decreasing salinity.  Marine ecosystem biomes and stratification of water by salinity will change in response.  Tests for carbon in sediment and nutrients such as nitrogen in the water show that ecosystem productivity is already being affected in some regions as a result.  A warmer Arctic Ocean could also attract species originally native to further south and facilitate the breeding of those that already live there (ex. the Arctic Cod).  It also limits the amount that primary production can increase because although there will be an increase in light, there will be an increase in secondary producers. 
Climate change effects on arctic marine ecosystems are usually modeled one of two ways, conceptually or numerically.  The numerical model described in this paper is a type of coupled physical-biological ecosystem model.  It looks at how chemical and oceanographic variables could affect biological processes and species dynamics.  Data from a number of studies using these models was collected and summarized by Wassmann.  The major trends and expectations extrapolated are those in the introduction paragraph. 
Wassmann concludes with a discussion of what further research should be done.  The Fram Straight, the central Arctic Ocean, and the Siberian ice shelf are areas where little to no research has been conducted.  More data is also needed on Arctic weather, SIZ, and “large-scale regulation of ecosystem function.” (Wassmann 2011)  Time series analysis would be beneficial as they allow scientists to see trends over time, but it is often difficult and expensive to do annual studies in one of the world’s harshest environments.  Wassmann advocates for the continued application of the physical-biological coupled 3D SINMOD and remote sensing models and the implementation of comparative studies.  International cooperation paired with these techniques will help scientists continue to observe the exact effects of climate change on the Arctic Ocean.  

Marine Ecosystem’s Response to Climate Change

The impact of climate change on marine ecosystems is still poorly understood. The distribution of marine populations in response to climate change could be a key clue to the future of marine ecosystems in our changing world. Sorte et al. (2011) studied the population-level variation of temperature tolerance in several populations of marine invertebrates. There were three separate case studies, all designed to better understand the lethality of rising water temperature. The authors identified the western Atlantic as a target zone for populations right at the edge of their temperature tolerance. They found both mussel and subtidal epibenthic (organisms living on the sea bed) species showed the highest susceptibility to temperature change. By compiling experimental data with current thermotolerance data and climate predictions the authors concluded that most populations of the intertidal Littorina snail were able to overcome geographic differences in temperature tolerance via acclamation. The authors concluded that particular species’ life history strategy and dispersal ability may determine their temperature adaptation abilities more than their overall geographical location.—Connor O’Boyle

Sorte, C., Jones, S., Miller, L., 2011. Geographic variation in temperature tolerance as an indicator of potential population responses to climate change. Journal of Experimental Marine Biology and Ecology 400, 209-217.

The relationship between ocean temperature changes and marine ecosystems is an important and relevant issue in the current changing climate. Sorte et al. studied multiple marine species and their physical and biological patterns to address how tolerances vary geographically and whether certain species have better ability to acclimate. They hoped to provide a starting point on which broader questions on the future of marine ecosystems could be based.

In their study they did three main experiments, the first was a trans-continental comparison using species that were geographically isolated, to test the impact of geographic location on a species survival. They collected four epibenthic species that grow on both the East and West coast of the United States and looked at their responses to their geographical independent temperature fluctuations. In their second experiment the authors compared mussel populations from France and the USA, in their abilities to cope with lab controlled marine temperature changes. The third experiment tested the long-term temperature acclimatization of Littorine snails from the same region of the western Atlantic.

The results of these experiments showed that the East Coast populations of epibenthic species were living closer to their tolerance levels than the West Coast ones, and that the higher temperature fluctuations on the East Coast of the United States create a greater risk for these species going forward. The authors concluded that if acclimatization is similar within species, individuals on the East Coast could experience dramatic population declines because of the current proximity of water temperatures to lethal levels. The authors found the mussels from France had a higher temperature tolerance than the US population, but both decreased in tolerance after multiple temperature exposures. These findings led the authors to believe that finding temperature history of a population’s habitat is essential in predicting the survivability of that population. The findings of the last experiment showed that temperature tolerance increased with lab acclamation but the response in geographic temperature tolerance differed between the species of snail. They concluded that in populations with low tolerance, survivability would depend on dispersal distance and the specific environmental behaviors (such as using tall eel grass to buffer temperature change).

The authors concluded that additional studies need to be made to analyze coping behaviors for species experiencing wide temperature changes in order to accurately predict population change. They found that in tunicates and bryozoans the temperature tolerance was related to habitat temperatures. The differences in tidal habitat zone could play a large part in a species’ ability to adapt and the authors established that populations with limited dispersal distances could be negatively impacted because of their inability to find suitable water conditions to recolonize. The organisms living in the western Atlantic could experience more drastic population change due to the heightened water temperature levels with species living in water very close to their lethal temperature.

The Use of Eocene Fossil Records to Predict Effects of Climate Change on Antarctic Bottom Fauna

Aronson et al. (2009) used the Eocene fossil record in the La Meseta Formation at Seymore Island, Antarctic Peninsula, to track the response of suspension feeding echinoderms and brachiopods that lived off the Antarctic coastal shelf at the time of the Eocene cooling event. The patterns of decline in predation on these organisms within the pre-cooling Eocene ecosystem were then used to predict how the current warming of Antarctic coastal water would affect the current organisms living along the shelf. It is predicted that increasing predation by invasive shell breaking species will reduce current populations of suspension feeding echinoderms possibly into extinction. It is also predicted that climate change will not affect the colonies of brachiopods or the current amount of shell drilling predation on modern populations of bivalves. –Rosemary Kulp
Aronson RB, Moody RM, Ivany LC, Blake DB, Werner JE, Linda C. Ivany4, Daniel B. Blake5, John E. Werner5¤a,
Alexander Glass5 (2009) Climate Change and Trophic Response of the Antarctic Bottom Fauna. PLoS ONE 4(2):e4385. doi:10.1371/journal.pone.0004385

The morphology of the Antarctic fauna is a product of climatic cooling that began in the Eocene 33.5 million years ago. At the beginning of the Eocene the Antarctic climate was considered temperate and contained predators like bony fish (telosts), crustaceans, and sharks (neoslachian elasmobranchs). With the cooling of coastal sea temperatures of up to 10°C by the end of the Eocene period, most of the durophageous (boney fish, ray, shark, and crustacean) predators became extinct. Along with the extinction of these predators, crinoids and ophiuroid (suspension feeders that prey on zooplankton) populations were able to increase. In today’s Antarctic coastal waters, the top predators are slow moving invertebrates that cannot break hard-shelled prey. 
Current increases in polar water temperatures allow predators like anomuran crabs to reinvade the western arctic peninsula in deep water only 1–2 degrees warmer than water on the coastal shelf. In order to predict how the current populations will be affected by the possible invasions of shell breaking, shell drilling, and durophageous predators, the Eocene fossil record from Seymore Island, Antarctic Peninsula was used to track the effects of a cooling period on the populations of modern organisms living on the Antarctic shelf and soft substrata.
After comparing the fossil record to modern day data it was found that populations of ophiuroids and crinoids increased after the cooling event but not before. Since both ophiuroids and crinoids are susceptible to predation and unintentional damage by durphageous organisms, their abundance is evidence of low predation after the post cooling Eocene period.
In order to determine whether there was any change in predation by shell breakers on brachiopods across the 41 million year Eocene cooling event, the shell morphologies of Bouchardia antarctica from two different sites in the pre cooling period and two sites in the post cooling period were compared using principle component analysis in order to determine the variance in shell morphology across sites and between the two time intervals. After comparing four shell metrics (i.e. length of brachial valve, and width of brachial valve) that could be measured precisely, it was determined that there was no consistent change in shell shape or size associated with a decrease in temperature or with the decline of predators.
A second examination was done on predation from shell drilling gastropods using a similar method, comparing evidence of shell drilling predation (boreholes) between nests of B. antarctica and between species of bivalve also susceptible to shell drilling predation before and after the cooling event. The data showed that declining temperatures in the Eocene did not significantly affect the frequency of shell drilling predation on the bivalve species while B. antarctica were not affected either before or after the cooling by shell drilling predation.
When running the Eocene cooling event in reverse, it was predicted that increasing predation associated with reinvasion of shell breaking predators would reduce drastically the populations of suspension feeders like epifaunal ophiuroids and crinoids that currently inhabit the area. It was concluded that the epifaunal brachiopods would not decline with the increase of boney fish (durophage) predators. Lastly, it was determined that the intensity of shell drilling predation on infaunal bivalves would not change appreciably.