Effects of temperature and red tides on sea urchin abundance and species richness over 45 years in southern Japan

By Nicole Suren, SRC intern

Between 1963 and 2014, scientists in Japan have conducted 45 years of near continuous monitoring of the abundance (number of individuals), species richness (number of species), and developmental abnormalities of the sea urchins around Hatakejima Island. Hatakejima Island has been a marine protected area since 1968, meaning that humans are forbidden from harvesting sea urchins in the area. Removing fishing pressure makes this area the ideal study site to examine the effect of abiotic factors such as sea surface temperature and red tide events on sea urchin population dynamics, which is important since echinoderms (the family containing sea urchins) are often keystone or dominant species in an ecosystem.

Figure 1. Location of Hatakejima Island within Tanabe Bay, Japan. (Source: Ohgaki et al., 2018)

Urchin populations near Hatakejima Island were monitored using three complementary methods. The first was a quadrat study, where the urchins in a permanent underwater quadrat were counted once every year. The second was a coastal survey, where a more general sea urchin count was conducted all along the coast of Hatakejima Island six times total. The third was a developmental assay, where eggs and sperm were collected, fertilized in vitro, and the resulting embryos were monitored for early developmental abnormalities. Overall, the scientists found that the sea surface temperature increased over thirty years, and that developmental abnormalities coincided with the occurrences of red tides.

Figure 2. Population trends of the three most common species of urchin from the study over time. (Source: Ohgaki et al., 2018)

Red tide events, temperature, and ocean currents were found to be closely related to the abundance of the three most common species of urchin: H. crassispina, E. moralis, and Echinometra spp. Exact effects varied depending on species, but red tide events were found to decrease abundance (likely due to the developmental disruption of urchin larvae), while warmer temperatures and proximity to the Kuroshiro current had positive effects on abundance and species richness.

Although this population of sea urchins is not subject to fishing pressure, it is far from unaffected by humans. An increased incidence of red tide events in the area may be attributable to an increase in aquaculture nearby. Furthermore, chemicals like tributyltin (TBT) and other organotin compounds used in fish nets and ships are being introduced to the water, which may also have negative developmental effects that decrease population size. In addition to the other human effects, anthropogenic climate changes also affect urchin abundance and species richness in this area because of their dependence on a particular temperature range. Studies like this one are essential to determining the full extent of human impacts on ecosystems, and should continue to be employed so we can decide how best to mitigate those impacts (Ohgaki et al., 2018).

Work Cited

Ohgaki, S. I., Kato, T., Kobayashi, N., Tanase, H., Kumagai, N. H., Ishida, S., … Yusa, Y. (2018). Effects of temperature and red tides on sea urchin abundance and species richness over 45 years in southern Japan. Ecological Indicators, (January), 0–1. https://doi.org/10.1016/j.ecolind.2018.03.040

Albatross-born loggers show feeding on deep-sea squids: implications for the study of squid distributions

By Gaitlyn Malone, SRC intern

Deep-sea squids are considered to be an important prey source for many top marine predators including fish, marine mammals, and seabirds (Clarke, 1996). However, despite their importance in marine food web structures, there is relatively little known about the biology and ecology of these squids, due to lack of observations, as well as limited knowledge of when, where, and how top predators prey on them (Nishizawa et al., 2018). Albatrosses are just one seabird species that feed mainly on squid, including those deep-sea dwelling species. Since albatrosses feed by capturing prey on the surface of the water, how they are able to obtain deep-sea squid has long been a mystery.

Figure 1. Laysan albatross (Phoebastria immutabilis) near Kauai, Hawaii (Dick Daniels, Wikimedia)

Multiple methods for accessing these squid have been hypothesized including feeding on squid that are dead and floating after spawning, those discarded from fishing vessels and longliners, those regurgitated by cetaceans, those that are living and come to the surface at night, or those that are alive and aggregate at the surface near productive ocean fronts (Rodhouse et al., 1987; Thompson, 1992; Clarke et al. 1981; Imber, 1992; Xavier et al., 2004). A recent study examined the post-spawning floater, fishery-related, and oceanic front hypotheses using Laysan albatrosses that were breeding on Oahu, Hawaii (Nishizawa et al., 2018). Laysan albatrosses were determined to be a suitable species to test these hypotheses due to the fact that they feed on both on deep-sea dwelling squid species and Argentine squids (Illex argentines), which are often used as bait in the swordfish longline fishery in Hawaii. In order to perform this analysis, 38 birds that were raising chicks were fitted with GPS-loggers and camera-loggers during the early chick-rearing period in February and March of 2015. The GPS-loggers were positioned on the backs of the birds, while the camera-loggers were placed on either the back or the belly depending on whether the bird was brooding chicks. Images were only collected by the cameras during daylight hours and were used to identify any squid species the birds preyed on, whether those squid were alive or dead, and whether they were whole or fragmented. Camera images were also used to reveal if fishing vessels or cetaceans were present in the area.

Figure 2. Images of squids recorded by the camera-loggers attached to Laysan albatrosses (Nishizawa et al., 2018)

In total, 26,068 images were obtained from 26 trips of 20 birds. Of those images, squids were visible in 23 images which corresponded to 16 predation events from 7 trips of 7 birds. Fishing vessels were found to be present in 69 images. All of the squids observed from the camera-loggers were dead and floating at the surface of the water, with ten of the squids being found in fragments while the other six were whole. Since many deep-sea dwelling squid species spawn and then die, it is possible that some of the squids present in the recorded predation events were the result of spawning mortalities. Although fishing vessels were observed, none were present in the images obtained during feeding events and the squids that were preyed upon were much larger than bait species. Therefore, these predation events are most likely not related to fishing occurring within the area. Overall, it was determined that Laysan albatrosses tend to feed opportunistically and do not tend to concentrate their efforts to a particular area. Through the use of GPS and camera-loggers, this study demonstrates how beneficial these devices can be in collecting information on the distribution of deep-sea squid and the significant role they play in the diet of marine predators.

Works Cited

Clarke, M.R. 1996. Cephalopods as prey. III. Cetaceans. Philosophical Transactions of the Royal Society B 351: 1053-1065.

Clarke, M.R., J.P. Croxall, P.A. Prince. 1981. Cephalopod remains in the regurgitations of the wandering albatross Diomedea exulas L at South Georgia. British Antarctic Survey Bulletin 54: 9-21.

Imber, M.J. 1992. Cephalopods eaten by wandering albatrosses (Diomedea exulans L.) breeding at six circumpolar localities. Journal of the Royal Society of New Zealand 22(4): 243-263.

Nishizawa, B., T. Sugawara, L.C. Young, E.A. Vanderwerf, K. Yoda, Y. Watanuki. 2018. Albatross-born loggers show feeding on deep-sea squids: implications for the study of squid distributions. Marine Ecology Progress Series 592: 257-265.

Rodhouse, P.G., M.R. Clarke, A.W.A. Murray. 1987. Cephalopod prey of the wandering albatross Diomedea exulans.Marine Biology 96(1): 1-10.

Thompson, K.R. 1992. Quantitative analysis of the use of discards from squid trawlers by black-browed albatrosses Diomedea melanophris in the vicinity of the Falkland Islands. Ibis 134: 11-21.

Xavier, J.C., P.N. Trathan, J.P. Croxall, A.G. Wood, G. Podesta, P. Rodhouse. 2004. Foraging ecology and interactions with fisheries of wandering albatrosses (Diomedea exulans) breeding at South Georgia. Fisheries Oceanography 13(5): 324-344.

Shifted Baselines Reduce Willingness to Pay for Conservation

By Molly Rickles, SRC intern

With climate change causing negative consequences for almost every ecosystem on earth, now it is more important than ever to fund conservation efforts to restore these extremely important environments. However, many people are unaware about the current state of these critical environments, which may affect their willingness to contribute to these important causes.

In this article, McClenachan et al. (2018) studied whether an individual’s willingness to pay for conservation efforts was affected by their perception of the current health of the environment, which is generally an understudied topic. The researchers used the concept of shifted baselines, or a reduction in expectations of the natural environment over time, to determine if people’s perception of the state of the environment was flawed. It has been previously stated that the public does not understand the baseline for coral reef health, which means that they have no comparison to today’s reefs. This is important to understand for conservation efforts, so that researchers can understand how the public gets engaged in these issues.

To answer their questions, the researchers conducted a survey of residents in Okinawa, Japan, to determine how they viewed change in coral reef ecosystems. It was found that respondents understood that there was a decline in coral reef health, but that the reasons for this decline were unknown. 67% of respondents were able to identify at least one component of decreased health of coral reefs. It was also found that respondents were more willing to pay for the creation of an MPA to solve these problems rather than donating to other conservation efforts, with the average donation being $142.22 annually. (Image 1) The researchers concluded that shifted baselines for reef health did affect willingness to pay for conservation, and that respondents that perceived a decline in reef health were willing to pay more than double than someone who did not understand this decline in health. This research shows the importance of documenting long-term change in ecosystem health, so that the results can be communicated to engage the public in these issues. With a stronger public engagement, people will be more willing to contribute to conservation efforts, which will help raise awareness and funds for these extremely important issues.

Image 1. This table shows how willingness to pay varies for different problems associated with declining reef health. Respondents had the highest willingness to pay for the creation of an MPA (Source: McClenachan et al. 2018)

Image 2. This graph shows the difference between willingness to pay when respondents understand that there are declines in ecosystem health versus when they believe the current state of the ecosystem is normal (Source: McClenachan et al. 2018).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Works Cited

McClenachan, L., Matsuura, R., Shah, P., & Dissanayake, S. T. (2018). Shifted Baselines Reduce Willingness to Pay for Conservation. Frontiers in Marine Science , 5. doi:10.3389/fmars.2018.00048

Gravity of human impacts mediates coral reef conservation gains

By Brenna Bales, SRC intern

Communities around the world depend on coral reefs for their livelihood, for tourism, and for protection against coastal degradation. With an increasing human population comes increasing human impact on these coral reefs and a decrease in the ability of a reef to provide the benefits listed above. Direct human impacts include overfishing, polluting the reef with trash or chemicals, and dredging; however, there are indirect human impacts such as anthropogenic climate change. Greenhouse warming affects ocean temperature which can stress corals (Jokiel 2004), and ocean acidification from carbon uptake can decrease the ability of corals to build limestone foundations (Langdon et al, 2000).

In Cinner et al’s analysis, the magnitude of human impact on of 1,798 tropical reefs in 41 nations/states/territories was described and quantified. In order to quantify this impact, the authors used a social science metric termed “gravity”, which has been used from economics to geography. For the adaptation to an ecological analysis, the gravity of human impact was measured as a function of how large and how far away a population of humans was to a certain coral reef (Figure 1). In each location, the status of reef management ranged from openly fished (little to no management), to highly protected marine reserves where fishing is completely prohibited.

Figure 1. The authors’ interpretation of “gravity” as a function of the population of an area
divided by the time it takes to travel to the reefs squared. (Cinner et al, 2018)

Two expected “conservation gains” (differences in the progress of a coral reef ecosystem when protected versus unprotected) in all regions were analyzed as to how they are influenced by human activity. The first was targeted reef fish biomass (species usually caught in fisheries) and the second was the presence of top predators within the ecosystem. Conservation gains can be beneficial to both people and ecosystems; When the health of a protected coral reef improves, it might drive new recruits and help re-establish other nearby reefs that are fished more. The authors hypothesized that the target conservation gains would decline with increasing gravity in areas where fishing was allowed, but that marine reserves would be less susceptible to these gravity influences.

Analysis of visual fish count data collected from 2004-2013 showed that gravity strongly predicted the outcomes for fish biomass in a reef ecosystem. Biomass in marine reserves showed a less steep decline with increasing impact as compared to openly fished and restricted areas (Figure 2). This was due to an unforeseen relationship between gravity and the age of a marine reserve. In high-gravity areas, older reserves contributed more to fish biomass when compared to low-gravity areas. These older reserves have had more time to recover after periods of high fishing stress. Even in the highest-gravity reserves, fish biomass was about 5 times higher than in openly fished areas. Top predators were only encountered in 28% of the reef sites, and as gravity increased, the chance of encountering a top predator dropped to almost zero. Overall, highly regulated marine reserves in low-gravity situations showed the highest biomass levels, and the greatest chance of encountering a top predator.

Figure 2. Modeled relationships showing reef fish biomass declines with gravity increases by
regulation type. Openly fished (red), restricted (green), and high-compliance marine reserves
(blue). (Cinner et al, 2018)

Four explanations for the decrease of fish biomass and top predator encounters were (i) human impact in the surrounding area of a marine reserve affecting the interior, (ii) poaching effects, (iii) life history traits of top predators making them susceptible to even minimal fishing stress, and (iv) high-gravity reserves being too young or too small for drastic improvement. The fourth explanation was further analyzed, where large versus small reserves were compared. Not surprisingly, larger reserves had higher biomass levels and top predator encounter probabilities. Lastly, the ages of the reserves were examined. The average reserve age was 15.5 years compared to older reserves (29 +/- years), and older reserves had a 66% predicted increase in biomass levels. Analysis of the likelihood of encountering a top predator was less definitive, suggesting high-density areas, no matter the age, reduce this probability greatly.

Ecological trade-offs such as high-gravity reserves being beneficial for conservation gains like reef fish biomass, but not so much for top predators, are important to consider. Top predators can face more fishing stress even in remote areas due to their high price in international markets, such as sharks for their fins, explaining the observed difference in low-gravity fished areas versus low-gravity marine reserves. Overall, when aiming to create an effective marine reserve or even regulations that aid in conservation gains, it is imperative to consider the gravity of human impact in the surrounding areas. How the impacts of gravity can be reduced is critical as populations grow along coastlines and climate change stressors increase as well. Multiple forms of management will most likely provide the most benefit to stakeholders (Figure 3) and the ecosystem.

Figure 3. A fisherman in the town of Paje, Tanzania takes his boat out behind the reef barrier to
catch a meal. Stakeholders are an important part in considering reef management decisions, as
millions of people rely on the reefs for their meals just as this fisherman.
(http://commons.wikimedia.org/wiki/File:Fisherman_in_Paje.jpg)

Works Cited

Langdon, C., Takahashi, T., Sweeney, C., Chipman, D., Goddard, J., Marubini, F., Aceves, H., Barnett, H. and Atkinson, M.J., 2000. Effect of calcium carbonate saturation state on the calcification rate of an experimental coral reef. Global Biogeochemical Cycles, 14(2), pp.639-654.

Jokiel, P.L., 2004. Temperature stress and coral bleaching. In Coral health and disease (pp. 401-425). Springer, Berlin, Heidelberg.

Adaptation of Sirenians: Changing Behavior to Allow for Better Thermoregulation

By Sam Aronwald, SRC intern

Through scientific investigation of dugongs in Australia, there is evidence of behavioral thermoregulation in the Sirenia order. A study on two Amazonian manatees (Trichechus inunguis) determined that the average body temperature of all four species that fall under the Sirenia order is regulated between 35.6*C and 36.1 *C (Gallivan, 1983). Out of the four members within the Sirenia order three of the species are types of manatee, while the fourth is the dugong (Dugong Dugon); the last of its family Dugongidae since the 18th century (Wikipedia, 2018). Both the manatees and dugongs have similar morphological and physiological limits on how they maintain a proper internal temperature, despite their varied habitats around the globe. A behavior which dugongs will exhibit to consciously demonstrate thermoregulation is to take a small migration to find warmer waters in the winter (Preen 2004). Even though the waters that they migrate to are low or even empty of any seagrass to support themselves on, they still remain for the majority of winter. This is most likely due to the necessity to escape colder waters for the sake of retaining their body temperatures to a status quo (Preen, 1992).

Figure 1. West Indian Manatee (Source: Unsplash. “Manatee Pictures.” Manatee Pictures, https://unsplash.com/photos/UDdt74azlig.)

Both the dugong and the manatee will travel from one warm area that is abundant with food to another regularly. A prime example is in Central Florida, West Indian Manatees will actually take advantage of human-produced warm water and warm water springs, like the waters that stream from boating canals for the sake of warmer habitats (Edwards, 2016). Thanks to their lower metabolic rates, they are able to feed in colder waters for a short time and contently return to their warmer waters for the majority of the day (Lanyon, 2006). However, Dugongs in Queensland will employ tactics that are the exact opposite. Unlike the West Indian Manatee, they will prioritize waters abundant with food over warmer areas, like the Gladstone power plant local to Queensland (Marsh, 2011). According to these varying behavioral trends between the manatee and the dugong, it can be surmised that despite sharing a majority of the same traits, the difference in habitats is causing a shift between both respective species-types in their conscious thermoregulation via daily migration.

Figure 2. Dugong (Source: http://commons.wikimedia.org/wiki/File:Dugong_Marsa_Alam.jpg)

Works Cited

Gallivan, G.J., Best, R.C., Kanwisher, J.W., 1983. Temperature regulation in the Amazonian manatee Trichechus inunguis. Physiol. Zool. 56, 255–262.

Wikipedia. “Dugong.” Wikipedia, Wikimedia Foundation, 26 Oct. 2018, en.wikipedia.org/wiki/Dugong.

Preen, A., 2004. Distribution, abundance and conservation status of dugongs and dolphins in the southern and western Arabian Gulf. Biol. Conserv. 118, 205–218.

Preen, A., 1992. Interactions between dugongs and seagrasses in a subtropical Environment. PhD Thesis. James Cook University, Townsville.

Edwards, H.H., Martin, J., Deutsch, C.J., Muller, R.G., Koslovsky, S.M., Smith, A.J., Barlas, M.E., 2016. Influence of manatees’ diving on their risk of collision with wa- tercraft. PLoS One 11, e0151450.

Lanyon, J.M., Newgrain, K., Alli, T.S.S., 2006. Estimation of water turnover rate in cap- tive dugongs (Dugong dugon). Aquat. Mamm. 32, 103–108.

Marsh, H., O’Shea, T.J., Reynolds III, J.E., 2011. Ecology and Conservation of the Sirena: Dugongs and Manatees. Cambridge University Press, New York.

Ups and Downs of habitat use: Horizontal and vertical movement behaviour of flatback turtles and spatial overlap with industrial development

By Sydney Steel, SRC intern

The most effective species conservation strategies extend beyond protection of key breeding grounds and nesting sites, and instead considers geographic range over the species’ entire life cycle. Many conservation efforts for endangered species are focused on these key sites due to the locations’ prospect of containing a condensed amount of individuals at one time, however most of the animal’s life is spent elsewhere in lesser-protected zones – presenting a need for increased studies about the overlap of habitat and potential anthropogenic threats.

Shipping ports pose as threats to marine life inhabiting nearby areas due to increased boat traffic, acoustic pollution, and risk of oil spills. (https://commons.wikimedia.org/wiki/File:Shipping_Port_of_Melbourne_Aust._(27465632031).jpg)

A 2018 study conducted by Michele Thums and colleagues focuses on a species relatively deficient in data: the flatback turtle (Natator depressus). Flatback turtles are unique because they live their entire lives on the unprotected continental shelf, where their habitat overlaps with industrial hazards including offshore gas fields, ship-loading facilities, and increased vessel traffic.

Flatback Turtle Hatchling (http://commons.wikimedia.org/wiki/File:Flatback_hatchling.jpg)

Thums, et al. harnessed satellite transmitters to 35 adult female turtles in the Australian marine areas of Bells Beach (nesting) and Delambre Island (breeding) near the Cape Lambert port and shipping channel over three winter nesting seasons between 2010 and 2013. The objective was to gain understanding of the traveled distances, general locations, and time frames associated with turtle behavioral modes. Three varieties of satellite transmitters regularly relayed spatial and temporal data to the ARGOs network, and the CTD-SRDL tag additionally reported conductivity, water temperature, pressure, and dive depth.

Position estimates of all flatback sea turtles tracked near the Cape Lambert port between 2010 and 2013 (Thums, et al 2018).

After completion of satellite recordings, the team analyzed data to account for position errors, and to provide an estimation of the turtle’s behavioral mode at each location. Behavioral modes included resident (inter-nesting and foraging) and transient (outward and other) modes and 50-95% utilization zones were determined for each mode.

On average, the flatback turtles spent 75% of their time in foraging mode, 12% inter-nesting, 8% outward transit, and 5% in other transit. The median range of these turtles (with all behavioral modes combined) was 295 km2, suggesting that the turtles traveled far distances between nesting sites and foraging areas. After overlaying each behavior’s geographic zone with the Cape Lambert Shipping Channel, it was found that turtles who migrated farthest had ranges that overlapped with the port and shipping channel – including an area that has been marked for construction of a wharf. 94% of turtles in inter-nesting and 26% of turtles in outward transit passed through the channel, highlighting that turtles in these modes may be more threatened by anthropogenic activity than turtles who are breeding at Delambre Island or nesting at Bells Beach. Conclusions of this study hint that flatback turtle conservation efforts should be established in migratory zones found to overlap with anthropogenic threats, rather than simply focusing on high-density areas like nesting and breeding grounds.

References

Thums, M., Rossendell, J., Guinea, M., & Ferreira, L. C. (2018). Horizontal and vertical movement behaviour of flatback turtles and spatial overlap with industrial development. Marine Ecology Progress Series602, 237-253.

Mapping nearly a century and a half of global marine fishing: 1869-2015

By Peter Aronson, SRC intern

Industrial fisheries are necessary for food security and public health worldwide.  They are expected to become even more important as the human population grows and the climate changes.  The global industrial fishing fleet has expanded to cover most of the world’s oceans, however there aren’t modern global overviews of the industrial fishing fleet. In this study, Watson and Tidd (2018) mapped global fishing patterns, demonstrating the value of mapping’s impact on fisheries management.  Reliable data is available from as old as 1869 and has been compiled with recent data to better understand global fisheries patterns (Watson 2017).

 

Figure 1: Fishermen drying codfish in Saint John’s, Newfoundland, Canada, circa 1900.  Cod were once very abundant off Newfoundland, but the fishery collapsed due to overfishing and a moratorium was placed on cod in Newfoundland in 1992.  Image source: McCord Museum, Wiki Commons.

 

Data was sourced from publicly available websites and used to compile a map of reported catches, which also contained estimates of illegal, unreported, and unregulated (IUU) fishing.  Data from the United Nations Food and Agriculture Organization (UNFAO) was compiled from 1950-2015, and the most location-specific data was used.  Data was adjusted to account for certain factors such as fishing gear, tuna fisheries, and satellite inaccuracies.  Additionally, it was separated based on whether the fishery was industrial or non-industrial to determine each sector’s impact on fisheries and how to manage each on its own.

 

The only nations that reported their catch before 1900 were the United States, Canada, and Japan.  More countries began reporting between 1900 and 1950, but fisheries weren’t as extensive because of a lack of technology for preserving fish once caught, causing fisheries to remain primarily coastal.  Right before WWII, fleets expanded greatly.  Reported catch declined again during the war, but after it rose right back to pre-war levels, and continued to increase greatly.  By 2000, fisheries were very expansive, and the effectiveness of management and policies varied greatly.  Despite more intense efforts, catch hasn’t increased in recent years.  Mapping fishing efforts creates data which can track which countries are catching the most fish over time.  Countries that have dominated fisheries at various times since 1869 include the United States, Canada, Japan, the United Kingdom, China, Peru, India, and the USSR.  Fish caught prior to 1900 usually lived near the seafloor, but since target species have spread to fish living in the water column.  Now, many types of species such as shrimp, squid, and tuna living in many ocean habitats are targeted.  Although extrapolation of fishing gear to reported catch prior to 1950 wasn’t feasible, some technologies that had major impacts on industrial fishing had already arisen, such as steam engines, diesel propulsion, and freezers.  Overall since 1950, practices involving seining have decreased and bottom and midwater trawling have increased.

 

Figure 2: Many sharks are caught accidentally in fisheries when they aren’t targeted by fishermen.  In this image, a bigeye thresher shark (Alopius superciliosus) was caught as bycatch.  Bigeye thresher sharks are listed as vulnerable by the International Union for Conservation of Nature (IUCN).

 

Today, the fishing industry has become so advanced that it can capture fish almost anywhere on earth.  Mapping is important because fish are a finite resource if used unsustainably, and fisheries could collapse.  Fish not only feed, but nourish billions of people around the world, providing important nutrients that many people, especially in impoverished regions, can’t obtain elsewhere.  Mapping allows for an accurate, easily communicable overview of the most heavily fished regions of the ocean, and where management is most needed.  In the future, mapping fisheries may be even more important.  Climate change threatens to change the distribution and productivity of stocks worldwide.  As technologies improve, mapping will become more accurate.  Fisheries have changed greatly since the 1860’s.  Viewing patterns in fisheries since then can help inform and make better decisions about maintaining marine resources into the future.

Works Cited

Watson, R. A. 2017. A global database of marine commercial, small-scale, illegal and unreported fisheries catch 1950-2014.  Scientific data 4: Article number 170039.

Watson, R. A., and Tidd, A. 2018.  Mapping nearly a century and a half of global marine fishing: 1869-2015.  Marine policy 93: 171-177.

“Climate-driven range shifts of the king penguin in a fragmented ecosystem”: a summary of the effects of anthropogenic climate change on habitat fragmentation through genomic analysis in the king penguin community

By Julia Saltzman, SRC intern

Climate change is a hot topic today, not only in the world of science, but also in the world of politics and policy (Figure 1). Despite this fact, it has not been until recently that scientists have started to study the impacts of climate change on specific species. Because anthropogenic climate change is known to have important consequence across biologic communities, having and understanding of the nature and extent of species’ responses is crucial in modeling policy for effective environmental change (Cristofori Et. Al., 245). In the article, Climate-driven range shifts of the king penguin in a fragmented ecosystem, research is discussed which focuses on the upper-level predator, the king penguin, in one of the most rapidly changing ecosystems on the planet: the sub-Ant-arctic region.

 

Figure 1: global surface temperature in 2017 compared to the 1981-2010 average. High latitudes of the Northern Hemisphere were especially warm, though temperatures across most of the planet were warmer than average (red colors). (Source: NOAA Climate.gov map, based on data from NOAA NCEI.)

 

The king penguin exhibits high levels of dispersal, and fragmented distribution. It has been suggested that the remarkably high migration rate among colonies can explain this. In order to test this hypothesis, researchers produced a genome-wide data set (Cristofori Et. Al., 246). including about 35,000 independent polymorphic loci genotyped in 163 individuals from 13 different locations covering most of the king penguin (Figure 2). Following the data collection, it was verified that the long-term relationship between paleohabitat reconstruction and the species’ past demography can be inferred from genomic data. Based upon this paleogenetic reconstruction, which allowed or analysis of location specific genomes, found that heterogeneous environmental changes lead to uncoupled effects on different crucial areas of the king penguins’ habitat.

 

Figure 2: the king penguin, Aptenodytes patagonicus, at first glance appears to be very similar to the emperor penguin, however, it is smaller and completely different genetically. (Source: Wikipedia commons).

 

Although this data gives highly complex insight into the genomic of the king penguin community across boundaries of fragmentation, it can tell scientists and policy makers really good information about the near-future scenarios which can project changes in these penguins’ range and population size. Although some scientists may suggest that the species can evolve overtime to adapt to anthropogenic climate change (figure 3), species fragmentation, and changes in resource partitioning, past data has found that due to the king penguins’ low genetic diversity and long generation time, the species is not expected to undergo any rapid adaptive evolution to new conditions in its range. Because species fragmentation and climate change go hand in hand, not only in the king penguins’ population, but in the overall ecosystem of the earth, this data collection methodology and results can give insight into the effect of habitat fragmentation on species’ niche and genetic diversity. This data can be used collaboratively to help mitigate the effect of anthropogenic fragmentation which happens so frequently in a plethora of ecological niches.

 

Figure 3: From a study of detailed analysis of a recently published Antarctic temperature reconstruction, which combined satellite and ground information using a regularized expectation–maximization algorithm (O’Donnell et al. 2009).

 

Works Cited:

O’Donnell, R., Lewis, N., Mcintyre, S., & Condon, J. (2011). Improved methods for PCA-based reconstructions: Case study using the Steig et al. (2009) antarctic temperature reconstruction. Journal of Climate. doi:10.1175/2010JCLI3656.1

Climate Change: Global Temperature | NOAA Climate.gov, 1 Aug. 2018, www.climate.gov/news-features/understanding-climate/climate-change-global-temperature

Weintraub, Karen. “Largest King Penguin Colony in the World Drops by 90%.” The New York Times, The New York Times, 31 July 2018, www.nytimes.com/2018/07/31/science/king-penguin-decline-antarctica.html.

Cristofari, R., Liu, X., Bonadonna, F., Cherel, Y., Pistorius, P., Le Maho, Y., … Trucchi, E. (2018). Climate-driven range shifts of the king penguin in a fragmented ecosystem. Nature Climate Change. doi:10.1038/s41558-018-0084-2

Using Fish DNA in Threatened Albatross Diets as a Marine Conservation and Management Tool

By Elana Rusnak, SRC Master’s Student

There is an unavoidable interaction between seabirds and the fishing industry, which impacts them through feeding supplementation, resource competition, and incidental mortalities (McInnes et al., 2017).  However, resolving these problems is often difficult and requires many resources.  Sea-faring birds are attracted to the fish scraps that are discarded from fishing vessels, which oftentimes come from species that are not naturally a part of their diet.  Gaining access to this food source may cause an imbalance in food-web structure, allowing gull populations to inflate, or causing albatrosses to prioritize nutritionally-poor food due to its ease of capture (Foster et al., 2017).  Moreover, these fisheries may be targeting an important food source for these birds and decreasing their access to it.  Understanding the interactions between seabirds and fisheries is necessary for effective ecosystem management.

 

Figure 1:  A trawling boat fishing for bottom-dwelling fish to which birds would not normally have access. (Source: NOAA – en:Image:Trawling_Drawing.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=1232501)

 

In the past, the two main ways to assess seabird diet were looking at their stomach contents, and stable isotope analysis.  Unfortunately, neither of these methods yield species-specific results when it comes to what kinds of fish are in these birds’ diets.  Recently, a non-invasive process called DNA metabarcoding has been useful in providing high-level specificity in seabird diets when analyzing their waste products.  It is also a broad-scale technique, which increases the number of birds and populations that scientists can sample while decreasing the amount of work and time required to do so.

 

Figure 2: The black-browed albatross (Source: Ed Dunens – Black-browed Albatross, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=64498778)t

 

The black-browed albatross is found in the southern hemisphere, where its population has been significantly impacted by longline and trawl fisheries.  A group of researchers used DNA metabarcoding to assess 6 sites across their breeding range to determine their prey diversity over space and time, identify if any of their prey comes from areas in which there are known fisheries operations, and evaluate potential resource competition or food supplementation by fisheries.  Albatross waste was collected, and DNA was extracted from each sample, then cross-referenced with known fish DNA.  The researchers found that 91% of their diet consisted of bony fish, with a diversity of 51 species, but the overwhelming majority of birds mostly ate 4 primary species of fish.  Samples collected from the 6 breeding sites showed differences in bird diet between sites.  A few species of fish identified from the DNA barcoding only live in the northern hemisphere, indicating that these birds are sourcing this prey from fisheries that use those kinds of fish as bait.  Depending on the site, between 0-60% of the birds were consuming fishery discards.  A few breeding sites were negatively impacted by resource competition, where the fishery was targeting their food source and they therefore did not have access to their normal diets.  This study shows that DNA barcoding has provided a means for scientists to prove that improvements in discard management to reduce the number of birds that feed from these vessels would reduce incidental mortality and have major implications for some albatross populations (McInnes et al., 2017).

Works cited

Foster, S., Swann, R. L., & Furness, R. W. (2017). Can changes in fishery landings explain long-term population trends in gulls?. Bird Study64(1), 90-97.

McInnes, J. C., Jarman, S. N., Lea, M. A., Raymond, B., Deagle, B. E., Phillips, R. A., … & Gras, M. (2017). DNA metabarcoding as a marine conservation and management tool: a circumpolar examination of fishery discards in the diet of threatened albatrosses. Frontiers in Marine Science4, 277.

How do cetaceans and other marine vertebrates avoid decompression sickness? A new explanation for beating the bends.

By Nick Martinez, SRC intern

The challenge of decompression sickness (DCS) and Nitrogen Narcosis, have always proved a threat to the deep diving vertebrates of the marine world. For years, scientists have debated over how cetaceans and other marine vertebrates are able to avoid DCS. In a recent paper from Daniel Parraga and colleagues, Pulmonary ventilation – perfusion mismatch: a novel hypothesis for how diving vertebrates may avoid the bends, the authors introduce a new hypothesis attempting to explain how this feat is actually performed.

To counter the challenges of DCS and nitrogen narcosis, cetaceans have developed a variety of adaptations that allow them to avoid catastrophic effects while diving. Many of the large deep diving cetaceans share a smaller mass-specific total lung capacity than that of shallower divers (Parraga et al. 2018). What this means is that larger whales have a comparatively smaller lung to body size ratio than that of dolphins, for example. Having a smaller mass-specific total lung capacity allows these cetaceans to have a smaller portion of their thoracic volume to be taken up and are able to have a larger vascular network. This vascular network comprises of multiple layers of alveoli, allowing there to be more oxygen storage when taking air at the surface. Smaller lungs prove more advantageous because a larger lung size would allow for more N2 absorption, increasing the risk of DCS (2018). Cetaceans also have a network of cartilaginous reinforcements that maintain the patency of airways during dives (2018). This system of cartilage allows for cetaceans to have high respiratory flow when taking breaths at the surface. The most important feature of the cartilage involves the facilitation of alveolar collapse at specific depths. Facilitating alveolar collapse prevents any excess N2 absorption into the bloodstream and thus reduces the risks of DCS (Figure 1). Finally, cetaceans have a series of vascular plexus that aid in oxygen storage and the redirection of air volume to the sound producing areas of the organism. This system of vascular control is the framework for complete DCS and nitrogen narcosis prevention. However, to understand exactly how cetaceans use their adapted bodies to prevent DCS and nitrogen narcosis, it is important to understand how they regulate gas exchange at depth various depths.

In Parraga’s paper, the author introduces the importance of gas exchange in marine vertebrates by first introducing two variables: VA and Q. VA equates to the rate of alveolar ventilation (air reaching the alveoli) while Q tells how much blood is perfusing the alveoli. These two variables are important for understanding how cetaceans are able to manage the rate of gas exchange within their body. If, for example, there were no management of gas exchange while diving, any air breathing organism would immediately fall to the effects of DCS because of the amount of nitrogen gas that is being dissolved into the blood stream. Originally, scientists believed that cetaceans controlled gas exchange by performing passive compression of alveoli and airways at specific depths. However, Parraga et al. note that this passive compression at significant depths does not explain how cetaceans prevent nitrogen related catastrophes at shallower depths. For example, many dolphins and small whales who get caught in gill nets have been found dead with signs of unregulated gas exchange, proving that regulated gas exchange is crucial at any depth. In fact, Parraga notes that between different species, alveolar collapse depth is completely variable between species.

The authors propose a new hypothesis attempting to explain how cetaceans are able to avoid DCS and nitrogen intake at any depth. This new hypothesis describes how cetaceans are able perform alterations in alveolar ventilation (VA) and perfusion (Q) that allows selective gas exchange during natural (dives not at alveolar collapse depth) and deep dives (at collapse depth). The way cetaceans perform this unique adaptation is they alter the VA/Q ratio to reduce inert gas uptake while simultaneously exchanging some O2 and CO2 (Figure 2) (Farhi et al. 1967). Altering the gas exchange ratio requires these organisms to force pulmonary gas into higher and lower parts of the lung. In doing so, a manual shut off of specific air ways occurs and it prevents blood from accessing air that would otherwise contaminate it. While unique, this process is very susceptible to failure provided that the right environmental and/or behavioral stressors are introduced to the organism.

Like all research, this information allows scientists to analyze exactly how these fragile organisms fall susceptible to anthropogenic factors. For example, beaked whales near areas of Naval sonar testing have been found stranded on beaches with gas bubbles in their blood stream (Jepson PD et al. 2003), proving that even in shallow waters, the sonars were able to disrupt the whales’ ability to manage gas exchange. The research conducted by Parraga and colleagues, and by other scientists, therefore proves vital in protecting these delicate species around the world. By understanding how cetaceans operate at various depths, scientists can turn research into policy that would help protect these organisms from population decline.

 

Figure 1: This figure displays a cross sectioned X-ray image of a pig (a), a grey seal (b) and a common dolphin (c) in a pressurized hyperbolic chamber. It is clear to see that the gas distribution of each organism at the same depths is different. In the pig, gas distribution stays uniform throughout but in the dolphin and seal, the air is transferred to the upper parts of the lung.

 

Figure 2: this figure displays the variations in the gas exchange ratios for each gas. The equation  shows how much gas exchange is going on with 0. As gas exchange ratios increase, the amount of gas that is actually being exchanged, decreases.

 

References

Garcia Parraga, Daniel, Moore, Michael J., Fahlman, Andreas, Pulmonary ventilation perfusion-mismatch: a novel hypothesis for how diving vertebrates may avoid the bends, proceedings of the Royal Society B: Biological Sciences 285 (2018)

Farhi LE, Yokoyama T. 1967 Effects of ventilation-perfusion inequality on elimination of inert gases. Resp. Physiol. 3, 12 – 20. (doi:10.1016/0034-5687(67)90019-9)

Jepson PD et al. 2003 Gas-bubble lesions in stranded cetaceans. Nature 425, 575 – 576. (doi:10.1038/nature 02528, 2004)