Conservation – Page 16 – Shark Research & Conservation Program (SRC)

A Study of Microplastics in San Francisco Bay

May 19, 2017/0 Comments/in Conservation, Ocean News /by a.anstett

By Lauren Kitayama, SRC intern

Introduction

Microplastics (defined as being < 5mm in size) are small enough to be ingested by filter feeders and planktonic organisms. Studies have shown that the average seafood consumer could be ingesting 11,000 pieces of microplastic annually (Cauwenberghe & Janssen, 2014). The human health impacts are not well understood, but preliminary research suggests that the particles themselves may not be able to pass through the intestinal wall. However, additives and toxins including chemicals that are known carcinogens and hormone disruptors are still a cause for concern (Galloway, 2015) Microplastics come as pre-production beads (often called nurdles), exfoliating beads in personal car products, microfibers that come from washing synthetic clothes, and the breakdown of larger plastics already in the ocean.

Plastic from facial scrub next to a dime. Photo credit: Dave Graff. Source: plasticaware.org

Average measurements of 700,000 microplastic particles/ km² (range: 15,000-2,000,000 particles/km²) makes the waters of San Francisco Bay the most microplastic polluted body of water sampled in North America.

Microplastics in San Francisco Bay

In 2016, researchers sampled eight wastewater treatment facilities that discharged into the San Francisco Bay. These facilities represent about 60% of wastewater discharged into the Bay. They voluntarily allowed researchers to sample their final effluent (the water that would be directly released). The rate of microplastic discharge from the wastewater treatments plants was 0.086 particles per liter, which equates to about 90 million particles a day. There was no difference among discharge rates between facilities that had secondary or tertiary treatment suggesting that waste water treatment plants are ineffectual at capturing and removing microplastics from waste water. Fibers were the most common type of microplastic found.

Samples were collected once from each wastewater facility during peak flow by passing the wastewater through 0.355 mm and 0.125mm sieves for 2 hours. They were then cleaned, and organic material was dissolved. Plastic particles were visually identified, and classified as one of five categories: fragment, pellet, fiber, film or foam.

Microplastics were also sampled at 9 sites inside the bay using a Manta Trawl and standard protocols. These surveys occurred at rising tides. Samples were cleaned, all organic material removed and visually classified just like the wastewater samples. All surface samples contained plastic ranging from 15,000 to 2,000,000 particles/ km². On average, density was higher in SF Bay, than the Great Lakes, Chesapeake Bay and Salish Sea.

Estimated abundance of microplastic particles in surface water at nine sites in San Francisco Bay. Circles are located at trawl midpoints. (Sutten et al, 2016).

High concentrations of microplastic pollution in the San Francisco Bay could be due to a high urban population surrounding a small, closed body of water. However this does not necessarily explain why densities would be higher in San Francisco Bay than in other urban surrounded bodies of water. Possible explanations include water conservation measures taken by the state during a severe drought that concentrates plastic. Other pollution pathways such as runoff and fragmentation may also play a large role. This study was an initial snapshot of microplastic pollution in SF Bay. Its findings indicate the need for more in-depth studies to look at the possible effect of tidal flux, 24-hour water use differences and impacts of storm water runoff. It also makes clear the need to better understand the implications of exposure to wildlife and humans. (Sutton et al, 2016).

The Bigger Picture on Little Plastics

Microplastics are becoming increasingly recognized as a threat to ocean and human health. Global release of primary microplastics is estimated to be 1.5 Mtons/year (Boucher & Friot, 2017). Microbeads in personal care products are often considered to be a large source of these microplastics. In fact in 2015 US passed the Microbead-Free Waters Act, banning the manufacturing and sales of products with microbeads with the intent of decreasing microplastic pollution in the countries waterways (2015). Canada, Ireland, the UK and the Netherlands have similar national legislation. But recent reports show that these exfoliating microbeads represent a small portion of microplastics pollution (2%). Whereas microfibers, released during the laundering of synthetic materials represents 35% of microplastics (Boucher & Friot, 2017).

Breakdown of primary microplastic loss into the ocean. (Boucher & Friot, 2017).

Companies like Patagonia have begun recognizing this threat to the planet, and are investing in solutions like a laundry bag that captures microfibers before they get blown out of the drier vent (O’Connor, 2017).

Work Cited

Sutton et al (2016). Microplastic contamination in the San Francisco Bay, California, USA. Marine Pollution Bulletin 109: 230-235. http://dx.doi.org/10.1016/j.marpolbul.2016.05.077

Microbead-Free Waters Act. (2015). 21 U.S.C. 331. https://www.gpo.gov/fdsys/pkg/BILLS-114hr1321enr/pdf/BILLS-114hr1321enr.pdf

O’Connor, M. (2017). Microfibers are polluting our food chain. This laundry bag can stop that. The Guardian. https://www.theguardian.com/sustainable-business/2017/feb/12/seafood-microfiber-pollution-patagonia-guppy-friend

Cauwenberghe, L. and Janssen, C. (2014). Microplastics in bivalves cultured for human consumption. Environmental Pollution 193: 65-70. http://dx.doi.org/10.1016/j.envpol.2014.06.010

Boucher, J. and Friot D. (2017). Primary Microplastics in the Oceans: A Global Evaluation of Sources. Gland, Switzerland: IUCN. 43pp. https://portals.iucn.org/library/sites/library/files/documents/2017-002.pdf

Galloway, T. (2015). Micro- and Nano-plastics and Human Health. Marine Anthropogenic Litter pp 343-366. http://link.springer.com/chapter/10.1007/978-3-319-16510-3_13

Plastic debris contamination in the Acoupa weakfish (Cynoscion acoupa) in a tropical estuary

May 15, 2017/0 Comments/in Conservation, Ocean News /by a.anstett

By Elana Rusnak, SRC intern

The Acoupa weakfish (Cynoscion acoupa) is an economically important fish that lives along the tropical east coast of the American continents. They tend to live in estuary systems—calm, brackish water habitats—as juveniles and sub-adults, and then move to saltier areas as they age. Tropical estuaries are one of the most productive ecosystems on Earth, and they provide shelter, food, and developmental grounds for many species of fishes and invertebrates. Unfortunately, since estuaries are more sheltered environments, plastic debris tends to accumulate and be ingested by the many species that make the estuary their home. A study by Ferreira et al. in 2016 explored the feeding habits of all life stages of the Acoupa weakfish in the Goiana Estuary in Brazil, and described the plastic debris contamination of the area and how it affects these economically important fish.

In this study, the fish were subdivided into three study groups: juvenile, sub-adult, and adult. They were observed and captured in the upper, middle, and lower parts of the Goiana Estuary, with the lower part being the saltiest. About 470 juveniles, 25 sub-adults, and 33 adults were used in this study. The stomach contents of each fish were removed and examined to determine the ratio of plastic debris to their natural diet (fish, crustaceans, worms, seaweed, plant fragments). The researchers found that in almost every fish, the majority of the stomach contents consisted of plastic debris, followed by crustaceans and fish (64.4% of juveniles, 50% of sub-adults, and 100% of adults were contaminated with plastic). Multicolored plastics were also found in the digestive tract, and a few specimens had nothing in the stomach other than plastic debris.

Plastic debris inside a penaeid shrimp, a primary food source for adult Acoupa weakfish (Ferreira et al., 2016)

Zoomed in image of red plastic debris inside the digestive tract of an Acoupa weakfish specimen (Ferreira et al., 2016)

So what does this all mean?

First, the Goiana Estuary waters are polluted with plastic debris at densities comparable to half the density of the fish larvae that reside in it (Lima et al., 2015). This indicates that this estuary system is very polluted. Moreover, the Acoupa weakfish isn’t the only organism ingesting all this plastic. The direct ingestion of plastic debris might primarily occur during the early stages of the Acoupa weakfish, whereas sub-adults and adults ingest debris through the trophic food chain (their prey ingests the plastic, then it is left behind in the adult fish’s stomach). This occurs through a process called biotransferrence. The presence of plastic in the digestive system is also problematic, as it can lead to digestive injuries and induce starvation. Since the Acoupa weakfish is a top predator in their estuarine habitat, they are more susceptible to food web disturbances.

This fish is not only a primary food source for the locals in the area, but it is also commercially fished. If they are filled with plastic, they are not getting the nutrition they need to become large, healthy fish. Without this growth, both the locals and the commercial industry will suffer. This study really showed the large-scale change that needs to begin now with regards to reducing plastic waste and keeping our environment clean and healthy.

Works cited

Ferreira, G.V.B., Barletta, M., Lima, A.R.A., Dantas, D.V., Justino, A.D.S., Costa, M.F. 2016. Plastic debris contamination in the ife cycle of Acoupa weakfish (Cynoscion acoupa) in a tropical estuary. ICES Journal of Marine Science 73: 2695-2707.

Lima, A. R. A., Barletta, M., and Costa, M. F. 2015. Seasonal distribu- tion and interactions between plankton and microplastics in a tropical estuary. Estuarine, Coastal and Shelf Science, 161: 93–107.

Making a run for it: escaped farmed Atlantic salmon integrating with wild populations

May 12, 2017/0 Comments/in Conservation, Ocean News /by a.anstett

By Robbie Roemer, SRC master’s student

Atlantic salmon (Salmo salar) as their name implies, are primarily found in northern Atlantic waters and are classified as androminous (living in the sea, and returning to freshwater to spawn). Known to be a popular recreational sport fish, this largest species found in the genus Salmo is prized for its table fare and thus, faces heavy commercial fishing pressure. This species is particularly sensitive to habitat alteration and human influence (Staurnes et al. 1995; Kroglund et al. 2007) and coupled with the high commercial demand, has seen significant historical declines over the last half century. These declines have led to substantial increases in aquaculture farming techniques where salmon are raised in pens on the very same waters utilized by native, wild populations to spawn. Breeding and farming programs have greatly altered the genetic makeup of Atlantic salmon as commercial enterprises target specific characteristics such as: larger total size, faster growth rates, efficient food utilization, and meat quality. But what happens to the inevitable large quantity of farm “escapees”?

Atlantic salmon are popular sport fish in Norway and beyond [Image by Vetle Kjærstad]

A recent study by Diserud Karlsson and others investigated and quantified genetic introgression (genetic mixing or “hybridization”) of escaped farmed to wild Atlantic salmon. Extracting genetic material from either scales or fin clips, and using several specific genetic markers representative of both wild and farm raised individuals; the team was able to quantify genetic introgression in 147 salmon rivers in Norway. A study of this magnitude was able to account for and represent three quarters of the total wild spawning population in the entire country. What the team found was an average level of genetic introgression of 6.4%, within a total range of 0.0% to as high as 42.2%. Moreover, significant genetic introgression had occurred in 51 separate wild salmon populations, with significant genetic introgression also occurring in 77 of 147 sampled rivers.

So why is the genetic introgression or “mixing “of farmed salmon to wild salmon ecologically important? The main concerns by the authors regarding genetics are the loss of genetic variation within a population, the loss of genetic variation between populations, and the loss of overall animal ecological fitness. It has long been shown that farmed salmon have much lower genetic variation compared to their wild counterparts ((Mjølnerød et al. 1997; Skaala et al. 2004, 2005; Karlsson et al. 2010). In addition, substantial loss of ecological fitness has been documented in farm-raised salmon. If wild to farmed genetic introgression continues at this rate, it is feared wild salmon populations will too lose genetic attributes, all of which are critical in sustaining healthy, disease-free, wild salmon populations.

Map of Norway showing rivers with farmed genetic introgression (Karlsson et al. 2016).

This research has real-world applications, as many hydropower companies that alter the natural state of rivers, and reduce natural productivity of native salmon compensate this “offset” by releasing farm raised fish into the river system. In the western United States, native cutthroat trout are facing a similar threat, as genetic introgression with rainbow trout is occurring at a rapid rate. It has been proposed to list the few remaining genetically “pure” populations of cutthroat trout under the Endangered Species Act (ESA). Similar proposals have been made to Atlantic salmon, even going so far as to list farm-raised salmon a different species, and treating farm raised “escapees” as an exotic species, to help deter genetic hybridization and introgression with wild populations.

One positive finding within the study was the lowest genetic introgression rates were located within Norwegian nationally protected lands (National Salmon Rivers and National Salmon Fjords), thereby demonstrating the ecological importance of preserved lands to wildlife populations. Indeed, there is no clear, sound solution to this problem, especially as the numbers of salmon farms are increasing globally. However, it is clear that at the present time, near-zero limits are the only viable solution to protect the genetic integrity of wild Atlantic salmon populations.

Works Cited

Karlsson, S., Diserud, O.H., Fiske, P. and Hindar, K., 2016. Widespread genetic introgression of escaped farmed Atlantic salmon in wild salmon populations. ICES Journal of Marine Science: Journal du Conseil, 73(10), pp.2488-2498.

Kroglund, F., Rosseland, B.O., Teien, H.C., Salbu, B., Kristensen, T. and Finstad, B., 2007. Water quality limits for Atlantic salmon (Salmo salar L.) exposed to short term reductions in pH and increased aluminum simulating episodes. Hydrology and Earth System Sciences Discussions, 4(5), pp.3317-3355.

Staurnes, M., Kroglund, F. and Rosseland, B.O., 1995. Water quality requirement of Atlantic salmon (Salmo salar) in water undergoing acidification or liming in Norway. Water, Air, & Soil Pollution, 85(2), pp.347-352.

Caribbean Spiny Lobster Fishery Is Underpinned by Trophic Subsidies from Chemosynthetic Primary Production

May 8, 2017/0 Comments/in Conservation, Ocean News /by a.anstett

By Molly Rickles, SRC intern

Caribbean spiny lobsters are a very commercially important species that brings in millions of dollars in revenue annually. The lobsters are especially important to the Bahamas, which has a large fishery. Recently, artificial reefs were created for the lobsters in areas where they are usually fished. This made it easier for the present study from Higgs and colleagues to take place, which analyzed the Caribbean spiny lobster diet. The main purpose of the study was to show that a significant portion of the lobster’s diet is from chemosynthetic primary production in the form of lucinid clams, which are found on artificial reefs. (Figure 1).

Figure 1: This image shows that the Caribbean spiny lobster trade is very lucrative, especially in the Bahamas. It also shows the food web and how the lobsters obtain their food from chemiosynthetic primary production. The lobsters consume the clams, which obtain nutrients from sulfate that was fixed by sulfate fixing bacteria from detritus. (Higgs, N. D., Newton, J., & Attrill, M. J. (2016). Caribbean Spiny Lobster Fishery Is Underpinned by Trophic Subsidies from Chemosynthetic Primary Production. Current Biology, 26(24), 3393-3398. doi:10.1016/j.cub.2016.10.034)

Researchers sampled 160 lobsters from both natural and artificial reefs. Tissue samples were collected from the tail muscle of the lobsters and dietary tissue samples required the whole lobster. (Figure 2) To study the lobster’s diet, scientists used stable isotope analysis to organize the lobster’s diets into five main food groups. Through this approach, it was found that the phototrophic group, or autotrophs, made up the majority of the lobster’s diet. These results show that chemosynthetic primary productivity plays an important role in commercial fisheries since the lobsters are mainly dependent on phototrophic productivity for food. The results also show that 1/5 of the lobster’s diet is from the chemosynthetic primary productivity of lucinid clams, which are found on artificial reefs in the lobster’s habitat. The clam’s productivity is from the chemoautotroph organisms that live symbiotically with them. In addition to studying the diet, the researchers compared the diets of lobsters living on natural reefs against lobsters that lived on artificial reefs. It was found that lobsters living on natural reefs have higher values of chemosynthetic productivity in their diets. This is mainly due to the fact that natural reefs have denser sea grass, which allows for higher chemosynthetic productivity.

Figure 2: This figure shows how the study was carried out. The top picture is of an artificial lobster shelter, which is where the lobsters used in this study normally were found. Image B is the carapace of a lobster used in the study. Image C is of a lobster dactylus, the last appendage of the lobster’s thorax. Image D shows lucinid clams, which the lobsters mainly feed on. (Higgs, N. D., Newton, J., & Attrill, M. J. (2016). Caribbean Spiny Lobster Fishery Is Underpinned by Trophic Subsidies from Chemosynthetic Primary Production. Current Biology, 26(24), 3393-3398. doi:10.1016/j.cub.2016.10.034)

This study is important because it was the first to determine the diet of the Caribbean spiny lobster. Since this species is heavily fished, this study showed the importance of spiny lobster management to maintain its population. It is also important to maintain chemosynthetic production on the artificial reefs to maintain a food source for the lobsters. This study also outlined the importance of the spiny lobster in marine ecosystems, since it was shown that the lobsters play an important role in transferring chemosynthetically fixed carbon from deep sediment to the organisms in the ecosystem. Since lobsters are both economically and ecologically important species, it is vital to protect and manage their population so that they can continue to contribute to the human diet and marine ecosystem.

Works cited

Higgs, N. D., Newton, J., & Attrill, M. J. (2016). Caribbean Spiny Lobster Fishery Is Underpinned by Trophic Subsidies from Chemosynthetic Primary Production. Current Biology, 26(24), 3393-3398. doi:10.1016/j.cub.2016.10.034

Sneaky Predators

May 1, 2017/0 Comments/in Conservation, Ocean News /by a.anstett

By Arina Favilla, SRC intern

“Everything you see exists together in a delicate balance, ” Mufasa wisely tells Simba in The Lion King right before a pouncing lesson. This is true of any ecosystem on the planet—the sun provides energy for plants to grow, plants are grazed on by herbivores, who are eaten by consumers, who are prey to other predators. Any prey-predator imbalance can have cascading effects on the entire ecosystem, particularly when invasive predators are especially sneaky predators, beating Simba in the element of surprise.

The element of surprise is difficult to accomplish in the aquatic environment because there are several cues (smell, sight, vibrations) that warn prey of a nearby predator and illicit a fast-start response, allowing them to get as far away as quickly as possible. It is debated whether this fast-start response is an autonomic response, similar to a knee-jerk reflex, or whether an individual can optimize their escape response in accordance to the threat.

Image of the red lionfish (Pterois volitans) displaying its characteristic fins and venomous spines. (From Wikimedia Commons)

McCormick and Allan (2016) investigated the red lionfish’s (Pterois volitans) success as a predator by determining the response of prey. The red lionfish, native to the Pacific Ocean, is a threatening invasive species in the Caribbean because of their success as predators easily devouring 8-10% of their body weight each day. They quickly decimate reef fish populations and destroy the delicate balance of a reef ecosystem. Moreover, recent research suggests lionfish are successful, sneaky predators by avoiding associative learning, a survival mechanism that allows prey to associate cues with dangerous predators leading to effective fast-start responses and successful escapes.

The study compared the response of whitetail damselfish to two predators, the red lionfish and the common rockcod, as well as a non-predator fish, the three-lined butterflyfish. First, the damselfish were conditioned to associate potential risk with the sight and odor of the two predator species coupled with chemical alarm cues. Previous studies have shown tropical fish species, including damselfish, can quickly learn to associate cues of a predator as a threat. Damselfish were then exposed to olfactory cues (seawater from the predator or non-predator tank) and/or visual cues (predator or non-predator tank placed adjacent to the damselfish tank) before being startled by a stimulus (release of a metal weight at the water’s surface) to provoke the fast-start response.

Comparison of the different aspects of the damselfish’s fast-start response when forewarned through chemical (white), visual (light grey), or a combination of cues (dark grey) of either one of two predators (red lionfish or rockcod), a non-predator (butterflyfish), or controls. The optimal fast-start response would have a short response latency time, high average response speed and maximum speed, and large distance travelled. Damselfish exposed to controls had the lowest response while those exposed to the rockcod had the highest response. Both the butterflyfish and lionfish elicited similar intermediate responses. (McCormick and Allan 2016)

McCormick and Allan (2016) found that the damselfish had greater fast-start responses when forewarned about the predatory rockcod through olfactory or visual cues, but showed similar ineffective fast-start responses—slow to react and slower speeds—when exposed to the cues for the lionfish as well as the non-predator butterflyfish and controls (Figure 2). In other words, the damselfish misidentify the lionfish as a non-predator, reducing its chance of escape if attacked. These results suggest that lionfish are capable of circumventing associative learning, leading to higher success rates in attacking prey. The findings of this study begin to explain the success of lionfish as predators, but further studies are required to better understand the mechanisms lionfish use to avoid forewarning of prey.

Works cited

McCormick, M. I. and B. J. M. Allan. 2016. Lionfish misidentification circumvents an optimized escape response by prey. Conservation Physiology 4:1–9.

A simple tool to predict bycatch in harbour porpoises

April 28, 2017/0 Comments/in Conservation, Ocean News /by a.anstett

By Emily Nelson, SRC master’s student

Harbour porpoise bycatch has been identified as the biggest threat facing these animals in many areas today, with many incidental catches occurring in large commercial gillnet fisheries. In efforts to minimize negative impacts, harbour porpoises in waters of the European Union have been awarded protection under Habitats Directive (EC 1992) and Council Regulation 812/2004 (EC 2004). Despite differences in specifics, these policies both work towards conservation and would benefit from increased information regarding bycatch of porpoises.

Harbour porpoise in Denmark. Photo by Erik Christensen.

Kindt-Larsen et al. 2016 aims to create a model that can identify areas and seasons where porpoises are at high risk of entanglement in commercial fishing gear. Two main high-resolution datasets were used to develop the model. First, fisheries and bycatch data was obtained from remote electronic monitoring systems aboard 4 commercial gillnet operations in the Danish part of the Skagerrak Sea. Using video footage of gillnet hauls the authors were able to identify time and location of harbour porpoise bycatch events. Fishing effort (defined as the product of gillnet string length and net soak time), fishing target species (cod, plaice, and hake), and season (winter, spring, summer, and autumn) were also used. Second, estimated population density of harbour porpoises was obtained using satellite tag data from 66 individuals in the same area. Data was filtered to remove positions that may be inaccurate, such as locations that required excessively high swim speed to reach. Further, tag data was manipulated according to a grid system. A value was assigned to each 1km grid cell within the study area reflecting the likelihood the particular cell was visited by harbour porpoises.

Density of harbour porpoises, estimated from satellite tagging data using a grid system.

This data was then used to identify the general relationship between expected bycatch and porpoise density. The authors started with the most complex model (involving all variables) and sequentially removed insignificant variables in order to find the best fit. In the end, target species and length of net did not improve the model fit. Additionally, porpoise density estimated using season and area (rather than satellite tag data) did not improve fit. The best model was very simple; harbour porpoise bycatch was best explained using solely soak time of fishing gear and satellite tag estimates of population density.

The success of the model developed by Kindt-Larsen and colleagues relies on a few large assumptions. First, the assumptions that satellite tagged porpoises are representative of the population as a whole. This concern was addressed in a number of ways. 1. Analysis was run showing that the spatial patterns observed were consistent over time. 2. Areas of high density predicted by satellite data were verified because acoustic surveys show similar results. 3.The satellite tagged individuals contained a mixture of juvenile, adult, male and females, thus there is no bias in the data do the demographic differences. The second assumption is that fishing effort estimations are truly representative of the four fisheries. This is verified because fishing effort was calculated the same way throughout all vessels. Lastly, the assumption that recorded porpoise bycatch was representative of the true number of bycaught animals. This assumption was of little concern to the authors because the REM video was of high quality and bycatch was easy to identify. However, if porpoises fell from the net prior to reaching the surface they were not recorded. For this reason it is important to consider bycatch estimates presented here as a minimum. Overall, it seems the assumptions of the model will have minimal impact on results.

The model created by Kindt-Larsen and colleagues follows the simple principle, that bycatch can occur only if the animal and fishery have an overlap in space and time. While the model presented is basic, it can absolutely act as a starting point for investigations of harbour porpoise bycatch. Results will be able to identify regions and/or seasons of high and low risk to porpoises. This will aid in future bycatch monitoring and the development of mitigation strategies.

Works cited

EC (European Commission) (1992) Habitats Directive: Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora. Off J Eur Union L 206: 7−50

EC (2004) Council Regulation (EC) No. 812/2004 of 26 April 2004 laying down measures concerning incidental catches of cetaceans in fisheries and amending Regulation (EC) No. 88/98. Off J Eur Union L 150: 12−31

Kindt-Larsen, L., Berg, C.W., Tougaard, J., Sorenson, T.K., Geitner, K., Northridge, S., Sveegaard, S., & Larsen, F. (2016). Identification of high-risk areas for harbour porpoise Phocoena phocoena bycatch using remote electronic monitoring and satellite telemetry data. Marine Ecology Progress Series, 555, 261-271.

The response of sandy beach meiofauna to nutrients from sea turtle eggs

April 24, 2017/0 Comments/in Conservation, Ocean News /by a.anstett

By Abby Tinari, SRC intern

South African scientists, Diane et. al (2017), studied how organic matter is transferred through the food web and how this influences consumer populations. Specifically, they chose to look at the interaction between sea turtle eggs and meiofauna in sandy beaches where organic matter is limited.

Loggerhead turtle, species who provided the turtle eggs. (Photo from Wikipedia Commons)

Meiofauna are small invertebrates that live in both marine and fresh water environments. The main taxa present in the study were nematodes, insect larvae, collembola, and halacarid. Sandy beaches lack an abundance of organic matter. Diane et. al predicted that the seasonal influx of turtle eggs would generate an increase in meiofauna abundance. To test this, they chose to look at how the meiofauna abundance differs between naturally predated nests and the sand around it as well as how quickly the meiofauna utilized the resource pulse.

The abundance study, looking at the differences in meiofauna population between the preyed upon sea turtle nests and the surrounding sand, sampled 15 nests taking three samples at 5, 20, and 40-centimeter depth from each nest. This was also done for the surrounding sand 2 meters from each of the selected nests to act as the control. These nests were naturally predated on by honey badgers and ghost crabs among other predators. 50 turtle eggs were taken from active nests and placed into 10 pseudo-nests (baskets) for the temporal study. The eggs were cracked to simulate natural predation. Diane et al. took samples at three depths (5, 20 and 40cm) in each the control and the experimental baskets. Samples were taken every day for 20 days. In each experiment the meiofauna was sorted into major taxonomic groups and the density of individuals was counted.

Mean abundances (±SE) of major meiofauna taxonomic groups in the experiment baskets (with turtle eggs: left panel) and control baskets (without turtle eggs: right panel) over the sampling period for the in-situ experiment.(a-b nematodes; c-d halacarid mites; e-f insect larvae; g-h collembolan; i-j unknown 1) (Diane et al. 2017)

Diane et al. found that the meiofaunal and nematode abundances were significantly different between the experimental and control nests for both the abundance and temporal study. Nematodes were the dominant taxa in both studies. In the first experiment, for abundance, the meiofaunal diversity was higher in the naturally predated nests than in the control nests around them. Collembolans were the second most dominant taxa in the predated nests while in the control nests insect larvae was the second most abundant taxa. The abundance of most meiofauna decreased with depth except for the collembolans which had similar abundances at the shallowest and deepest depths. In the temporal study the species richness was higher in the experimental baskets than in the control baskets. Diane et al. also found a significant difference in abundance at the middle and bottom depths. Most meiofauna were in the deepest samples close to the eggs. Abundances and maximums varied with time. Nematodes were the first to arrive and die out, followed by insect larvae, halacarid mites and collembolans.

Studying the interactions between trophic levels is useful to know, even on a macroscopic scale. Some of the meiofauna observed were insect larvae that will become consumers and prey for other taxa. Diane mentions that nematodes feed on bacteria and other macrofauna and this could be linked to higher trophic levels. The sea turtle eggs bring a predictable annual source of nutrients that allow the meiofauna to thrive. Other spawning events may have a similar increase in meiofauna populations and abundances with the pulse of organic matter they bring. Knowing the interactions between trophic levels can help scientists better understand the effects of an abundance shift in one of the levels.

Works cited

Diane Z.M., et Le Gouvello, Ronel Nel, Linda R. Harris, Karien Bezuidenhout. 2017. The response of sandy beach meiofauna to nutrients from sea turtle eggs. Journal of Experimental Marine Biology and Ecology 487:94-105.

Finding Nemo’s Anemone

April 21, 2017/0 Comments/in Conservation, Ocean News /by a.anstett

By Leila AtallahBenson, SRC master’s student

A Nemo lookalike in close proximity to an anemone host. [Wikimedia Commons]

Do you remember in Finding Nemo when the eagle ray professor asks the kids where they live, and nemo replies, with some difficulty, that he lives in an anemone? Have you ever wondered about the relationship between the clownfish and their anemone homes? It is known that these two species interact and have a mutualistic relationship. Anemones house and protect clownfish, but what do clownfish do for the anemone? Well, a group of researchers from Boston University took a deeper look at the association of clownfish and anemones.

They conducted a one-and-a-half-year study, where they placed 0, 1, or 2 clownfish in a tank with an anemone. They watched the fish personalities over the course of the study. Fish personalities were described by how much time a fish spent near their anemone home: were they a shy fish, like Nemo’s dad Marlin, and spent most of their time in or around their anemone? Or were they a more outgoing fish, like Nemo, and adventured away from their anemone? They then recorded what growth effects these different personalities had on the anemones.

Predicted anemone growth given the shyness of a fish over the year-and-a-half study. Maximum shyness of a fish is 1200 sec. [Schmiege et al. 2017]

As it turns out, shyer fish help anemones show more growth. Anemones with fish residents that spent more time near to them grew significantly more than anemones whose fishy friends spent more time adventuring away from their homes. The scientists proposed that this relationship is seen between shy fish and anemone growth because shy fish provide more oxygenation, nutrients, and freedom to stretch the anemone’s tentacles and feed for themselves. Shy fish swim and move around the anemone more frequently, bringing oxygen to the anemone. Given shy fishes’ increased presence, there is also more fish waste for the anemone to absorb nutrients from. Shy fish are also around to defend their hosts more, which allows the anemone to stretch out its tentacles and absorb more nutrients from the water column. Maybe that’s why Nemo and Marlin’s anemone was the same size when they came back from their adventure, it did not have its shy, fishy friends to help it grow.

An anemonefish next to an anemone, Entacmaea quadricolor, the kind used in the study. [Wikimedia Commons]

Works cited
Schmiege, P.F.P., D’Aloia, C.C., Buston, P.M. 2017. Anemonefish personalities influence the strength of mutualistic interactions with host sea anemones. Marine Biology 164:24.

Atypical and Estuarine Habitat of the Maroni River Mouth Altering Green Turtle Behavior in French Guiana

April 17, 2017/0 Comments/in Conservation, Ocean News /by a.anstett

By Casey Dresbach, SRC intern

Green Sea Turtle, Chelonia mydas.
(Your Shot National Geographic, 2013) http://yourshot.nationalgeographic.com/photos/2387735/?source=gallery)

In this experiment, satellite telemetry was used to assess the behavioral adjustments of twenty-six adult female green turtles. Sixteen Argos-linked Fastloc GPS tags were deployed on green turtles from February to June 2012 on both sides of the Maroni River: Awale-Yalimpo and in the Galibi Nature Reserve in Suriname. At the same time, ten other females in the Amana Nature Reserve were equipped with Conductivity-Temperature-Depth-Fluorometer Satellite Relayed Data Loggers, which provided the locations of the turtles via Argos data, and recorded profiles of the dive depth, time at depth, dive duration and post-dive surface interval, and oceanographic data in the form of vertical temperature and salinity profiles taken during the rising phase of these turtles’ dives as seen in Figures 1 and 2. The intent of tagging was to analyze three entities: home range, diving behavior, and environmental conditions.

Figure 1. Extreme temperatures recorded in-situ by the Argos-Linked Fastloc GPS tags on green turtles Chelonia mydas of 2012. (Chambault, et al.)

Temperature-salinity diagram for the green turtles tagged with a CTD-SRDL tag in 2014. (Chambault, et al.)

In relation to home range, the findings show that Chelonia mydas stayed close to both the shore and their nesting beach, exhibiting limited movement. By staying close to shore, the turtles are likely to save energy for oviposition, the act of laying their eggs. Regarding diving behavior, dive data showed that individual female green turtles were spending extended periods at the surface. This may be related to their highly diurnal resting activity, where they are active during the day. The data also shows that these turtles went for short and shallow dives. One of the reasons for this suggests basking at the surface, which can be beneficial for thermoregulation, especially in these warmer waters. Also, this behavior permits the avoidance of aggressive males or potential predators, delay of algal or fungal infestations, and also an enhancement of immune response. Additionally, spending time at the surface is associated with both their lungs’ positive buoyancies (being denser than water surrounding it) as well as foraging activity. In terms of finding food, a green turtle’s preferred choice of sustenance is seagrass. However, the waters of the French Guiana provide an extreme environment for these turtles, where large river outputs generate very warm water (~27 to 29° C) and highly variable salinities (1.2 to 35.5 psu), as shown in Figures 1 and 2. In these waters, the high river outflow lead to low levels of irradiance, probably resulting in the lack of seagrass. The turtles of the French Guiana have adapted to this consequence by seeking alternate food sources and also relying on stored body fat for energy, defining the population as capital breeders. Adaptations are often compromises; each organism must do many different things to compensate for their surroundings (Reece, Urry, Cain, Wasserman, & Minorsky, 2014). We humans owe much of our versatility to our flexible limbs, but they are also prone to sprains, torn ligaments, and dislocations. Hence, structural reinforcement has been compromised for agility. These turtles are compromising their preferred food choice because it is unavailable. Their available alternatives include those befitting the water’s turbid environment such as: crustaceans, polychaete worms, and cnidarians. Jellyfish are fairly abundant on the French Guiana continental shelf, and these female turtles are adapting an appetite for an alternative source of nutrition to enable survival.

This study provides the first data to describe the inter-nesting events, habitat use, dispersal and diving behavior of green sea turtles. The findings show this population of Chelonia mydas has adapted many behaviors in response to the deviant and estuarine habitat of the Maroni river mouth. This is the first study to track this specific population of green turtles during their inter-nesting season. Satellite tracking made it possible to locate and quantify the habitat used by Chelonia mydas during their inter-nesting seasons. Their survival is at risk, both with increasing climate change and the life-threatening illegal fishing along the Guiana coast. By evaluating their home range, it makes it possible to obtain a reliable visual of areas where these turtles nest, to thus identify hotspots that need protection. The endangered species is particularly vulnerable during their inter-nesting periods, especially in the atypical environment they are residing in. Further research should be done to evaluate the interactions between green turtles and fisheries to ultimately seek permission to delineate a Marine Protected Area.

Works cited

Chambault, P., Thoisy, B. d., Kelle, L., Berzins, R., Bonola, M., Delvaux, H., et al. (2016). Inter-nesting behavioural adjustments of green turtles to an estuarine havitat in French Guiana. Marine Ecology Progress Series , 555: 235-248 .

Dunand, A. (2013, October 15). Your Shot National Geographic .

Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., & Minorsky, P. V. (2014). Campbell Biology . Boston: Pearson.

Nocturnal migration reduces exposure to micropredation in a coral reef fish

April 14, 2017/0 Comments/in Conservation, Ocean News /by a.anstett

By Josh Ratay, SRC intern

The French grunt was used as the organism of study, though gnathiid isopods feed on many different species of reef fish. Image from Wikimedia Commons.

Nocturnal migration reduces exposure to micropredation in a coral reef fish is a new study examining daily migrations of French grunt (Haemulon flavolineatum) and the exposure to parasitic isopods. French grunts are known to move off the reefs and into seagrass beds at night. Such behavior in animals is usually attributed to increased availability of prey or decreased exposure to predators. However, this study investigates the idea that the fish’s movements may serve as a method of avoiding isopods, which are far more common on the reefs than in seagrass communities.

The French grunt served as an ideal model organism for this study since it is both extremely common and well-studied on Caribbean reefs. However, many other reef fish are known to undertake similar nightly migrations away from the reef. Gnathiid isopods are tiny parasitic crustaceans which attach to fish and feed on blood. Though they usually hide in reef sediments, the larvae emerge to find a short-term host fish directly before molting and growth. Though far smaller than their hosts, these parasites can have many negative health impacts on fish, including decreased concentrations of red blood cells, tissue damage and infection, and even the death of juvenile fish which are exposed to a high isopod load.

Larval gnathiid isopods (bottom right) feed on the blood of fish before molting. Adult males (left) and females (right) tend to remain in the sediment. Image from Wikimedia Commons.

In this study, several tests were performed at different locations in the Caribbean to test the hypothesis that leaving the reef at night results in fewer numbers of isopods infesting French grunts. Cages containing 5 to 8 fish were deployed overnight at both reefs and nearby seagrass habitats where grunts had been observed. Also, the exact arrival times (around dawn) of the wild grunts to the reefs were observed at different sites, and cages of grunts were subsequently placed at the reefs for both the 30 minutes preceding the arrival time and 30 minutes following the arrival time. The goal of this test was to investigate whether or not the fish’s arrival time coincided with lessened isopod activity. Additional cages were also deployed to test day versus night isopod levels, and the whether or not juvenile grunts were also susceptible to isopod infestation. All fish from the cages were placed in seawater tanks, where the isopods naturally detached and were then counted.

Box and whisker plot showing the decrease in isopods in the time after the fish have returned to the reef vs. immediately before. Figure from Sikkel et al 2017.

Statistical analysis of the data revealed that grunts which spent the night on the reefs contracted 3 to 44 times as many isopods as those which were left in the seagrass bed. Fish which were placed on the reefs during the 30 minutes before the return time of the wild grunts contained twice as many isopods as those which were exposed to the reef after the return time. Nighttime isopod load on the reefs was also much higher than the daytime load, and isopods were detected on juveniles from the reefs but not the seagrass beds. Overall, these results were significant and suggest that moving to seagrass beds at night is an effective method of isopod evasion for both adult and juvenile grunts, and that the fish return in the morning as isopods become less active. The results from this study suggest that further research is needed into the potential for parasites to drive movements of coral reef organisms.

Works cited
Sikkel, P. C., Welicky, R. L., Artim, J. M., McCammon, A. M., Sellers, J. C., Coile, A. M., & Jenkins, W. G. (2016). Nocturnal migration reduces exposure to micropredation in a coral reef fish. Bulletin of Marine Science.