Migration Dynamic of Juvenile Southern Bluefin Tuna

By: Julia Saltzman, SRC Intern

Large-scale migrations are crucial to many different marine species. In southern bluefin tuna, this life history trait is critical for sustaining their valuable fisheries, and as such there are many scientific research programs designed to monitor the management of the species. Telemetry technology (remote tracking of spatial locations and movements) has made cycles more generally observable, however quantifying variability and plasticity of migration schedules still remains a challenge. In this study from Patterson et al. (2018), movements from 110 individual juvenile southern bluefin tuna were estimated from the period of 1998-2011. The authors found that individuals demonstrated considerable variability in migratory patterns between the years. Patterns observed that juvenile southern bluefin tuna progressively spent less time in shelf waters, and the moved east, rather than west into the Tasman Sea for a higher period then heading west into the India Ocean. In addition, it was found that the further southern bluefin tuna move from the Great Australian Bight (GAB), the more time they spend migrating. This study also determined three areas associated with the residency of juvenile southern bluefin tuna. These areas of residence were far different from the known areas of residence in the past. The productivity in these residency regions displayed a seasonal cycle.

This study asserted that much like other large marine animals who use temperate latitudes, juvenile southern bluefin tuna also undertake long distance and large-scale migrations. In addition, while fish were observed to migrate to key areas, their patterns, especially in the winter months, varied both on an individual and yearly basis. Researchers suggested that for fast growing, immature, large, predators, such as those studied here their migration may be related to environmentally availability, rather than cues which are fixed such as day length. Other environmental factors also impact the migrations; for example, because the fish is a visual predator, they prefer to hunt in clear waters away from areas of high turbidity and high primary productivity. In addition, it is likely that seasonal populations of small pelagic fish in the GAB coincide with the migration of the southern bluefin tuna.

Through the use of tag deployment and geolocation of juvenile southern bluefin tuna, and Hidden Markov Models to estimate when individuals were migrating, important insights were obtained on the individuals within the same period and within individuals across multiple years. The complexity of migration routes appears to be related to sea surface temperature, productivity, and the physiology of the individual southern bluefin tuna. This report provides scientists and fisheries managers with the information to effectively manage southern bluefin tuna. This species, which has faced massive declines in the past due to poor management strategies, is now much better managed due to an understanding of their varying migratory patterns, especially those of juveniles.

Work Cited:

Patterson, T. A., Eveson, J. P., Hartog, J. R., Evans, K., Cooper, S., Lansdell, M., … & Davies, C. R. (2018). Migration dynamics of juvenile southern bluefin tuna. Scientific reports8(1), 14553.

Climate Change Induced Trophic Amplification Declines Planktonic Biomass

By: Delaney Reynolds, SRC Intern

Figure 1: A collage of different planktonic organisms (Source: http://planktonchronicles.org/en/episode/plankton/)

Plankton, including phytoplankton and zooplankton, make up 99% of all marine life and form the base of the food web. Phytoplankton undergo photosynthesis, much like plants do, and thus their growth and population size are dependent on availability of nutrients and levels of light. Zooplankton feed upon phytoplankton and thus their population size is partly dependent on phytoplankton populations.

The effects of anthropogenic climate change on phytoplankton and zooplankton populations is widely unknown, but scientists are taking steps to determine what those effects may be.

In a study by the Dynamic Meteorology Laboratory in France, Dr. Lester Kwiatowski took a look at how the trophic amplification of plankton biomass changes based on different models of future climate change, as well as how an amplification of this response may trickle through the food web.

Two different modeling techniques were used in this study: the Coupled Model Intercomparison Project Phase 5 (CMIP5) Earth System Models and the Pelagic Interactions Scheme for Carbon and Ecosystem Studies Quota (PISCES-QUOTA) model. The CMIP5 models modeled the trophic interactions between zooplankton and phytoplankton biomass under twenty-first century climate change projections. The PISCES-QUOTA model was used to explore what the mechanisms controlling zooplankton and phytoplankton trophic interactions might be under different climatic conditions.

Figure 2: This figure displays the projected percentage of plankton biomass anomaly by year from 1850 to 2100, as well as according to latitude. All three populations of plankton (phytoplankton, microzooplankton, and mesozooplankton) decrease in biomass; however, it can be concluded that the zooplankton will be much more negatively affected than the phytoplankton. It can also be deduced that in the lower latitudes, where it is warmer, zooplankton will also be more negatively affected than phytoplankton (Lester et al. 2018).

Kwiatowski found that both models projected a decline in both in zooplankton biomass and phytoplankton biomass as a result of climate change, with a moderately larger decrease in zooplankton biomass than phytoplankton biomass. According to the CMIP5 models, phytoplankton biomass is expected to decline by 6.1 ± 2.5% and zooplankton biomass is expected to decline by 13.6 ± 3.0%. The PISCES-QUOTA model split up zooplankton into two groups: microzooplankton and mesozooplankton. This model found that phytoplankton biomass is expected to decline by 8.5%, microzooplankton biomass by 15.4%, and mesozooplankton biomass by 20.6%. Here again, a slightly greater decrease in zooplankton biomass can be found than phytoplankton biomass. The PISCES-QUOTA model also determined that the driving factor affecting the biomass levels was primarily the fact that “primary production decreases in equatorial and subtropical biomes due to stratification-driven reductions in nutrient availability” (Kwiatowski et al., 2018).

Looking at comparisons between carbon, nitrogen, and phosphorous stoichiometry, the discrepancy between phytoplankton and zooplankton can be explained. As a result of climate change, the PISCES-QUOTA model also predicted a decrease in the phytoplankton nitrogen content by 1.1% and phosphorous content by 6.4%, just in the twenty-first century. As zooplankton consume phytoplankton, this decrease of nitrogen and phosphorous in phytoplankton will ultimately lead to a decline in the growth efficiency of zooplankton and a decrease in the overall zooplankton population.

Phytoplankton and zooplankton comprise of the base of the marine food web and also produce about 50% of the earth’s oxygen. Without them, many larger organisms would be heavily impacted. Studies just like this one can help us better understand the future that our delicate food web may face under the threats of climate change and give us insight into how we might be able to combat the probable effects.

Works Cited

Kwiatkowski, L., Aumont, O., & Bopp, L. (2019). Consistent trophic amplification of marine biomass declines under climate change. Global change biology25(1), 218-229.

The Utility of Combining Stable Isotope and Hormone Analyses for Marine Megafauna Research

By: Olivia Wigon, SRC Intern

Marine megafauna face many threats such as ship strikes, climate change, ocean noise and habitat destruction, which have caused many populations to decline. Typically, conservation takes a reactive approach instead of a proactive one which makes it hard to maintain healthy populations of marine megafauna. Alyson H. Fleming and her team are working with stable isotope and hormone analysis to understand in a more in-depth way how megafauna, specifically cetaceans, pinnipeds and sea turtles, are responding to their ever-changing environments (Fleming et al. 2018). The team is looking at physiological biomarkers that can help explain an animal’s movements, nutrition, stress, health and reproductive information. This data can give scientists and conservationist enough time to react proactively to the issues marine megafauna are facing. For example, looking at the ratios of stable carbon and nitrogen in bulk tissues Fleming and her team can determine not only the animal’s habitat but also its trophic level. This is made possible because the carbon and nitrogen isotopes found in bulk tissue indicate the biogeochemistry in the base of the food web. In addition to looking at stable isotopes the team looked at hormone levels. Hormones connected to reproduction can reveal an animal’s maturity, sex, whether or not the animal is pregnant, birth rates, sex ratios and more. Along with reproductive hormones there are stress hormones which can show predator exposure and areas of nutritional deficits. There are also thyroid hormones that will show an animal’s nutritive levels.

Some of the challenges with this research is that different tissues and different isotopes have different half-lives. The half-life rate varies based on the rates of protein metabolism. It is important to note that a tissue type can have different half-life rates based on the species and individual. Hormone analysis on the other hand is typically similar across vertebrate species however, the physiological roles of each hormone can have a different role in each species. Despite these challenges this is a growing and developing field of study. Integrating the results of stable isotope analysis with hormone analysis can answer many questions among many biological levels. When trying to solve a conservation issue it is best to have several lines of evidence which this process creates. Since this is a new and emerging field, there is still work to be done in regards to establishing methodology.

Work Cited:

Fleming, A. H., Kellar, N. M., Allen, C. D., & Kurle, C. M. (2018). The Utility of Combining Stable Isotope and Hormone Analyses for Marine Megafauna Research. Frontiers in Marine Science, 5, 1-15.

 

“Boo! Did we scare you?”: behavioral responses of reef-associated fish, prawn gobies (Amblyeleotris steinitzi and Amblyeleotris sungami) to anthropogenic diver disturbance 

By: Allison Banas, SRC Intern

There are many factors that can affect the health of coral reef communities, SCUBA diving being one of them. Studies have shown that divers’ activities can have significant detrimental effects on the ecosystem, and this paper from Valerio et al. (2018) looks at the effect divers can have on the behavior of two species of gobies.

The paper’s hypothesis is that divers in heavily dived areas have a habituating influence, along with causing a decreased latency period and a lower flight initiation distance (FID) on the gobies. This study took place at five sites along the Israeli coast of the Gulf of Eilat/Aqaba with differing levels of disturbance (Figure 1) Divers floated at least 3 m above the goby, and photographed the fish with a chosen scale object, and those gobies being disturbed were disturbed with a small weight attached to a nylon string wrapped around a pencil and lowered to land on the substrate approximately 15 cm in front of the goby. A timer was used to measure the latency period (time from disappearance to first reappearance), as soon as the goby retreated into its burrow. A seven-minute maximum time was pre-set.

Gobies in areas of high diver disturbance were found to no longer react to disturbances by having shorter latency periods, as well as shorter FID when compared to gobies at un-dived sites. Anthropogenic disturbance therefore is potentially leading to habituation of the gobies. The two different species of gobies were found to also have an effect on the data collecting, with A. sungami members having a significantly longer latency period than A. steinitzi, but this difference was found to be not significant. External factors including body size, circadian rhythm, depth and diving season were analyzed for significance, but none were found to have an effect on the latency periods.

This study opens the door for other studies to look at the potential effect of diver disturbance on the predation of gobies, since the gobies are spending less time in their burrows after a disturbance and have a shorter FID. If the same level of diver disturbance continues without rapidly habituating, the gobies could potentially spend a larger proportion of daylight hours in their burrows. Various statistical tests were completed in order to calculate potential diver effect, correlation between variables, average latency periods, and FID distances. In conclusion, diver disturbance has an effect on the behavior of gobies, and therefore the gobies have adapted their behavior.

Figure 1: A map showing the study sites along the coast of Eilat, Israel in the Gulf of Aqaba. (filled circle) Heavily dived (HD) and regularly dived (D); (light grey triangle) undived (UD); and relatively undived (RUD); and (light grey square) naturally disturbed (ND) [Dr. Gil Koplovitz]

Figure 2: Proportion of gobies that emerged over the 7-min time limit at each of the five sites. (Valerio et al. 2018)

Works cited

Valerio, M., Mann, O., & Shashar, N. (2019). “Boo! Did we scare you?”: behavioral responses of reef-associated fish, prawn gobies (Amblyeleotris steinitzi and Amblyeleotris sungami) to anthropogenic diver disturbance. Marine Biology166(1), 1.

 

Investigating the vulnerability of European Seafood Production to Climate Warming

By: Gaitlyn Malone, SRC Intern

As the world’s climate continues to change, economic, social, and environmental changes will undoubtedly occur along with it. One sector that is expected to be economically affected by climate warming is seafood production (Breitburg et al., 2018). Seafood production, which includes both farmed and captured fish, shellfish, and seaweed in marine and freshwater, will experience changes since the warming of an environment has the ability to change both a species’ distribution and life history characteristics (Pecl et al., 2017; Cochrane et al., 2009). Therefore, it is crucial to work towards being able to predict and understand the extent of these changes in order to prepare for the future.

A recent study (Blanchet et al., 2019) examined the effects of climate change on seafood production within each European country in order to identify potential challenges and opportunities within the sectors of marine fisheries, marine aquaculture, and freshwater production. To do so, the researchers combined information on the target species’ temperature preferences, life history characteristics, and production volume to determine their biological sensitivity (BS) and the maximum temperature (Tmax) that they were experiencing. They then determined the adaptive ability of seafood production in each country or sector by determining the number of species that the country/sector exploits and those species’ temperature ranges. A country or sector that exploits a higher number of species will be more likely to adapt in response to climate change. A species with a wide temperature range would also potentially be more adaptable since they are able to withstand a variety of temperatures.

Figure 1: Biological sensitivity index versus the temperature range of each species within the sectors of a) marine fisheries, b) marine aquaculture, and c) freshwater production. The size of the bubbles relates to the total volume produced for each particular species in that sector (Blanchet et al., 2019).

Figure 2: Ranking of each European country’s vulnerability to warming based on their weighted temperature sensitivity and weighted biological sensitivity for each of the three production sectors. The size of the bubbles represents the relative contribution of each country to the total European production volume within that sector (Blanchet et al., 2019).

Overall, seafood production was found to generally be more vulnerable within the marine fisheries and aquaculture sectors. The freshwater sector varied greatly based on country. Within the marine sector, northern countries tended to be more sensitive to warming than southern countries since seafood production in these areas are more dependent on cold-water species with a high BS. Southern countries tended to rely on warmer water species that had a lower BS. The main challenge facing these marine fisheries is due to changes in species distribution. In response to warming, there has been a northward expansion of the range of several species, which in some cases has included a contraction of their southern range. This change in distribution has the ability to affect local fisheries and management, who in southern areas may lose access to their resources, while northern areas may benefit. Aquaculture taking place in temperate zones was also predicted to be at risk from warming conditions, since increasing temperatures have the ability to reduce oxygen levels in the water and increase the metabolic costs for organisms. Disease is also likely to increase in these systems since pathogens may spread more readily. The low amount of species diversity in aquaculture also makes it particularly susceptible to rising temperatures.

Under warming conditions is not impossible to continue producing sustainable seafood, however efforts must be made to adapt to climate change. Therefore, the authors suggest that there must be communication between stakeholders, diversification of exploited species, and transnational cooperation in order to meet these goals.

Work Cited

Blanchet, M.-A., Primicerio, R., Smalas, A., Arias-Hansen, J., Aschan, M. 2019. How vulnerable is the European seafood production to climate warming?. Fisheries Research 209, 251-258.

Breitburg, D., Levin, L.A., Oschlies, A., Gr.goire, M., Chavez, F.P., Conley, D.J., Gar.on, V., et al., 2018. Declining oxygen in the Global Ocean and coastal waters. Science 359 (6371).

Cochrane, K., Young, D.C., Soto, D., Bahri, T., 2009. Climate change implications for fisheries and aquaculture: overview of current scientific knowledge. FAO Fisheries and Aquaculture Technical Paper 530, 212.

 Pecl, G.T., Ara.jo, M.B., Bell, J.D., Blanchard, J., Bonebrake, T.C., Chen, I.-C., Clark, T.D., et al., 2017. Biodiversity redistribution under climate change: impacts on ecosystems and human well-being. Science 355.

 

 

Effectiveness of MPA’s

By: Peter Aronson, SRC Intern

One might think that setting aside marine protected areas (MPA’s) – areas of the ocean where human activity is more heavily restricted – would reduce fishing pressure and overexploitation of marine species. However, that is not always the case. A group of researchers sought to determine if MPA’s experience intense human pressure, and if that pressure was undermining the goal of conserving biodiversity. They focused on European waters, where a substantial amount of industrial fishing occurs (Kroodsma et al., 2018), and an ample network of MPA’s covers about 29% of the sea (European Union, 2016).

Trawling is the most common method of industrial fishing in Europe (Kroodsma et al., 2018). It often has high bycatch rates and is a threat to many endangered species, including many elasmobranchs, as well as entire seafloor habitats. Researchers used satellite data to track fishing vessels and quantify commercial trawling effort. All 727 MPA’s in the study were considered 100% marine, designated prior to 2017, and listed on the World Database on Protected Areas.

Figure 1. Miramare Marine Reserve, Italy. (Sebastian Lake, September 29, 2015. Wiki Commons)

In 2017, combined trawling effort exceeded 1 million hours with over 225,000 occurring inside MPA’s. Trawling intensity, measured in hours per square kilometer, was 38% greater inside MPA’s compared to unprotected areas, and 46% more intense inside MPA’s when only looking at the areas that were trawled. This suggests that under current management, there is no reduction of fishing pressure inside MPA’s. Higher trawling rates typically occurred in larger MPA’s. Of all 727 MPA’s, trawling occurred in 489, of which 58% were located within territorial waters. Interestingly, only 40% of untrawled MPA’s had management plans whilst 60% of commercially trawled MPA’s did.

The relative abundance of 20 elasmobranch species was estimated from data collected on scientific trawl surveys between 1997 and 2016. Elasmobranchs were generally rare, with the main concentrations located west and south of the British Isles. Elasmobranchs were caught in 79% of the 178 MPA’s that were surveyed (only 13% of these had no commercial trawling). Total elasmobranch catch per research haul was 2.3 times higher outside MPA’s than inside, and a normalizing for species showed 24% more elasmobranchs outside the MPA’s.

Figure 2. Salmon shark caught in a trawl net. (Kathy Hough, http://www.moc.noaa.gov/od/visitor/Photo%20Gallery/Life%20at%20Sea/photos-d/photos-d.html Wiki Commons.)

Multiple factors are thought to drive conservation outcomes inside MPA’s, however, under present fishing pressure, only MPA size correlated positively with relative elasmobranch abundance. Untrawled MPA’s had a larger average elasmobranch abundance than trawled MPA’s. Overall, elasmobranch abundance negatively correlated with commercial trawling intensity both inside and outside MPA’s. It was found that commercial trawling was the strongest predictor of relative elasmobranch abundance across the study sites with an average decrease of 69% across the observed gradient of trawling intensity. This provides further evidence that increased trawling effort in MPA’s negatively impacts sensitive species and reduces ecological value.

This study shows designating MPA’s does little value for at-risk species. The issue of declining biodiversity due to high trawling intensity in European MPA’s has been highlighted here. The lack of international MPA standards may play a role in the lack of effectiveness, and better standardization of MPA’s should occur to avoid this. Allowing industrial fishing in MPA’s provides a false sense of security about marine conservation in Europe, and much work needs to be done to make MPA regulations stronger and management more transparent.

Work Cited:

A. Kroodsma et al., Science 359, 904-908 (2018). European Union, The EU in the World 2016 Edition (European Union, 2016).

Are Polar Bears on Thin Ice?

By: Kaylie Anne Costa, SRC Intern

When you think of polar bears what comes to mind? Is it a mama bear and a cub struggling to swim miles to find a piece of sea ice? Because that is exactly what is beginning to occur in the Arctic. With the rise of the sea surface temperatures, more and more sea ice is thawing causing the polar bears breeding and hunting grounds as well as means for transportation to disappear.

Figure 1: Polar bears using sea ice for transportation (By NOAA Photo Library – anim0115, Public Domain, https://commons.wikimedia.org/w/index.php?curid=17942736)

Polar bears have a varied diet consisting of seals, birds, fish, whales, and other marine resources. They also utilize a mixture of hunting methods. For example, polar bears may stalk seals in the open ocean or sneak up on seals that are drifting on sea ice. When there is not sea ice, polar bears must rely much more heavily on their swimming skills for transportation and hunting.

In a recent study, Lone et. al (2018) studied the time that female polar bears spend in the water to gain understanding as to how polar bears might react to future decreases in Arctic sea ice. 57 adult polar bears were tagged with devices to gather data on their locations, the amount of time spent swimming, and the diving depths. This study showed that polar bears’ choice of hunting strategies, and therefore amount of swimming, greatly depends on the individual. In addition, environmental factors and if the females had cubs also impacts the time a polar bear spends swimming. Polar bear cubs lack the thick layer of fat that insulates their bodies leaving them more susceptible to hypothermia. As a whole, the main variable that influence the swimming behaviors of the polar bears was the seasonal variation in sea ice. The most swimming occurred in summer and fall with less swimming occurred during the winter and spring. Modeling techniques were also used to correlate increased swimming with decreased levels of sea ice.

Figure 2: Polar bear swimming (https://commons.wikimedia.org/wiki/File:Polar_bear_arctic.JPG)

Overall the polar bears appeared well adapted to arctic marine environments and were able to complete long distance swims and dive greater than 10 meters. As sea ice continues to disappear, more polar bears will be required to alter their choices of hunting strategies to adapt to the new environment. This study shows promise in polar bears’ ability to adapt to reduced sea ice, at least to a certain extent. Further studies will need to be completed to analyze the impacts that additional swimming behavior will have on the polar bears health overall.

Works Cited

Lone, K., Kovacs, K. M., Lydersen, C., Fedak, M., Andersen, M., Lovell, P., & Aars, J. (2018). Aquatic behaviour of polar bears (Ursus maritimus) in an increasingly ice-free Arctic. Scientific reports8(1), 9677.

The Importance of Horizon Scans for Finding Emerging Conservation Issues

By: Molly Rickles, SRC Intern

Often times, there are many conservation issues that go unnoticed because the general public and government are focusing on larger, more easily accessible issues. However, this doesn’t mean that the smaller, more localized conservation issues aren’t important. Horizon scans of emerging issues brings to light some of these other equally important situations. To determine the most pressing issues that aren’t receiving enough attention, the authors of this study first identified possible topics, which resulted in an original search of 91 topics. Then, they circulated the list to participants who ranked the topics based on their awareness of the topic. This narrowed down the list to 15 topics that are presented in this paper. All of the topics presented are assumed to be low knowledge areas of study, and topics that need attention due to their urgency or potential magnitude (Figure 1). While the topics range from Antarctic ice loss to the use of salt tolerant rice, some general similarities and observations can be drawn. While many of the issues focus on finding sustainable solutions, it is highlighted that even these ‘better’ alternatives can still have negative environmental effects. This shows the need for more research and environmental impact assessments before implementing alternative solutions to common problems, because the effects can be negative even if the solution is perceived to be more sustainable.

Figure 1: This image shows the Qinghai-Tibet Plateau in China, which is where China is building new irrigation canals that could have devastating environmental impacts (source: https://www.panoramio.com/photo/56563318.)

Another general observation is that powerful governments, such as the US and China, have the ability to implement policy that has global environmental impacts. For example, one of the highlighted topics was the use of new irrigation canals in China for farming that would destroy multiple ecosystems without the use of an environmental impact assessment. This could have far reaching effects for the health of the river system that travels beyond China’s boundaries (Figure 2). This fact is also highlighted by the US government’s decision to withdraw from the Paris Climate Agreement. Since the US will not be following the set emission standards, the health of the global environment will be affected.

Figure 2: This image shows the methodology used by the authors. The authors started with a large sample size and narrowed it down by surveys and in person meetings to determine the most relevant topics to be used in the horizon scan.

A reoccurring theme throughout the topics was new agricultural technology. The authors suggested that this might hint at the urgency among scientists of meeting food demands, which is becoming an important issue. While such new technology would be advantageous if it improved food availability, new technology is not always monitored or regulated. This can cause detrimental environmental impacts.

These horizon scans of environmental issues are important for bringing light to less well-known conservation problems. All of the topics are considered to be low awareness, but with enough research involved to show it can be plausible. Bringing these issues to the public’s attention is extremely important to raise awareness and make sure that the best solutions are being implemented to create a more environmentally conscious global community.

Work Cited:

Sutherland, W. J., Broad, S., Butchart, S. H., Clark, S. J., Collins, A. M., Dicks, L. V., . . . Gaston, K. J. (2019). A Horizon Scan of Emerging Issues for Global Conservation in 2019. Trends in Ecology and Evolution.

Impact of Multiple Stressors on Sea Bed Fauna in a Warming Arctic

By: Brenna Bales, SRC Intern

The Arctic Ocean has been a heavily monitored area in recent years as climate change continues to affect the planet. This area is at high risk due to the fact that is has warmed at almost twice the rate as the rest of the planet in recent decades causing a decrease in sea-ice cover, glacial volume, and increases in temperature and precipitation (Hassol and Corell 2006). The Barents Sea is particularly vulnerable to climate change as it is experiencing the greatest temperature increases throughout the Arctic and may soon become an Atlantic-dominated climate region with warm and well-mixed waters, further preventing sea ice formation (Lind et al. 2018). Jørgensen et al. (2019) examined the Barents Sea benthic (seafloor) composition and how it has been affected by several stressors relating to climate change. Ecological impacts among the benthic environment were examined as a result of seawater warming, bottom trawling, and predation from a new, invasive predator: the snow crab (Figure 1).

Figure 1: Two snow crabs along the seafloor, a larger male above and a smaller female below. Image Credit: Derek Keats, Johannesburg, South Africa

The study characterized the vulnerability of different invertebrate groups when affected by these three variables across a predefined grid consisting of 36 x 36 nautical mile cells in the Barents Sea (Figure 2). Firstly, sensitivity to seawater warming between 2009-2011 (colder period) versus 2012-2015 (warmer period) was investigated. Both species temperature indices (a measure of the average temperature experienced by individuals across a species’ range) and community temperature indices were calculated by combining temperature values with information about the seafloor organism distribution. Secondly, species vulnerability to bottom trawling (Figure 3) was characterized by a species’ morphology, mobility, and body size. Slower, larger, and taller animals were categorized as having a larger susceptibility to trawling effects, whereas quicker, smaller animals would be more resilient. Lastly, the predatory effects of the invasive snow crab were quantified by number of prey items and annual biomass (amount of prey) consumed.

Figure 2: Geographic location of the Barents Sea with the 2280 sampling locations from the present study (Jørgensen et al. 2019).

Figure 3: Depiction of the practice of bottom trawling (Source: NOAA.gov).

From the initial, colder period (2009-2011) to the latter, warmer period (2012-2015), there was an increase in organisms with warm-water affinities and a reduction in those with cold-water affinities. While the overall sensitivity to temperature of the communities decreased with time, areas that were further north into the Arctic showed a higher vulnerability to temperature changes than more southern areas continuously experiencing warming waters. The sensitivity to trawling was lowest in the center region of the Barents Sea and increased toward outer regions. Lastly, the sensitivity to snow crab predation was highest along the northwestern border connecting to the southeastern border of the study area. Overall, the northwestern area of the Barents Sea was found to be the most vulnerable area when all three variables were combined. In conclusion, the combination of multiple stressors in any particular area can have severe consequences on the resilience of a local community to change. Management in the form of closed areas or gear modification is thus highly recommended by researchers from this paper to lessen the threats that these communities, especially those of the northwestern Barents Sea, are facing.

Work Cited:

Hassol, S.J. and Corell, R.W., 2006. Arctic climate impact assessment. Avoiding dangerous climate change, p.205.

Jørgensen, L.L., Primicerio, R., Ingvaldsen, R.B., Fossheim, M., Strelkova, N., Thangstad, T.H., Manushin, I. and Zakharov, D., 2019. Impact of multiple stressors on sea bed fauna in a warming Arctic. Marine Ecology Progress Series608, pp.1-12.

Lind, S., Ingvaldsen, R.B. and Furevik, T., 2018. Arctic warming hotspot in the northern Barents Sea linked to declining sea-ice import. Nature Climate Change8(7), p.634.

Functional Group Analysis Provides Insight in to Changes in Ecological Communities

By: Carolyn Hamman, SRC Intern

The interaction and impact humans have with and on oceanic environments are difficult to measure yet of vital importance to understand. The increasing global demand for fish as a food source has led to fishing pressures with potentially detrimental effects on the fished communities. By understanding the changes that are occurring within these ecological communities, conservation measures can be proposed to protect the habitat from becoming irreversibly changed. The caveat is the many environmental factors and interactions within and among certain communities which makes it hard to accurately predict impacts from fishing pressure.

Prior methods have included looking at measurements, such as species richness, as a proxy for community changes (Bremner, 2008). However, this ideology might not be as applicable within environmentally variant communities. Instead, there is a new approach that groups populations with certain like traits together. These groups, called functional groups, share response and effect traits. These traits capture how well the groups will survive based on different environmental conditions as well as the effect the same group has on other organisms and the overall ecosystem (Lundquist et al., 2018). This method of analyzing ecosystem impacts is advantageous as it standardizes responses certain individuals might have as well as looking at responses that are actually relevant to the ecosystem (Lundquist et al., 2018).

An example of this approach in action occurred in a study looking at the approach of bottom fishing disturbance on benthic communities in New Zealand (Figure 1). Here, researchers split the species in the area in to eight functional groups based on the way said species interact and modify their environment, and hypotheses were made on how fishing would disturb each functional group based on their characteristics (Lundquist et al., 2018).

Figure 1: An image of the New Zealand exclusive economic zone (EEZ) (Source: http://www.mfe.govt.nz/publications/marine/offshore-options-jun05/html/figure-1.html).

The scientists looked at the abundance of each functional group as a function of different categories of certain parameters including depth, seabed roughness, sediment, seabed slope, tidal current, primary productivity, and fishing effort. The results from the analysis showed how effective using functional groups was as a proxy for predicting the impact seafloor trawling has on disturbing the benthic communities in New Zealand (Lundquist et al., 2018). Each functional group had different responses to each variable based on how the group interacts with their environment. Even with increased fishing effort, some functional groups had an increase in abundance, which would allow them to radiate as other functional groups decreased in abundance.

Figure 2: Abundance of each functional group for the Ocean Survey 20/20 offshore dataset for different fishing effort classes. Abundance values for groups 4 and 6 are plotted on the secondary y axis. Error bars represent one standard error. (Lundquish et al., 2018)

Using functional groups as a method to analyze changes in ecological communities provides a more holistic and accurate way to look at how ecosystems change as a result of different parameters, including fishing effort. Having a more accurate picture of the changes allows scientists to be able to implement more robust protocol that will protect the ecosystem for the future.

Works cited:

Bremner, J. (2008). Species’ traits and ecological functioning in marine conservation and management. J. Exp. Mar. Biol. Ecol. 366, 37–47.

Lundquist, C. J., Bowden, D., Cartner, K., Stephenson, F., Tuck, I. & Judi E. H. (2018). Assessing Benthic Responses to Fishing Disturbance Over Broad Spatial Scales That Incorporate High Environmental Variation. Frontiers in Marine Science, 5(405), 1-14. Doi: 10.3389/fmars.2018.00405