Category Archives: RSMAS

Dry Tortugas Shark Expedition

image003love sharks and am deeply proud to have just completed my first year as an intern in Dr. Hammerschlag’s Shark Research & Conservation (SRC) Lab here at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science.

As summer begins and my Freshman year at RSMAS comes to an end, I am excited to share that I am about to cast off with some of my SRC lab partners and people from the Field School for a shark research expedition in the magnificent waters of the Dry Tortugas in the Gulf of Mexico. I’ll be traveling and living aboard the 55’ R/V Garvin’s research vessel with 13 other crew members and we will be performing all sorts of cool research on shark populations in the Gulf.

68 miles West of Key West, the Dry Tortugas are an untouched natural environment filled with incredible marine life and beauty. With the exception of Fort Jefferson, which maintains a small staff of National Park Service personnel, the islands are uninhabited and were named by Ponce de Leon in the early 1500’s after sailing by them and believing they were shaped like turtles (tortugas in his native Spanish language).

I visited the Dry Tortugas about three years ago on a family fishing and diving trip and fell in love with them. The waters are pristine, the beaches soft and bright white and the sea and marine bird life is abundant everywhere you look or swim. It’s simply an amazing place and I am very exited about conducting research there and enjoying another adventure in a place I love.

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While I am offshore on the expedition, please know that I will not have any cell, email or internet service but I hope to return will all sorts of stories and pictures to share with you. Enjoy the end of your school year and the start of summer and you can be sure I will be enjoying my time with the sharks and other awesome marine life in the Gulf of Mexico.

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The Effect of Hurricane Hermine on Black Sea Bass

The following article first appeared on the Research Blog for Dr. Neil Hammerschlag’s Shark Research and Conservation (SRC) Lab website at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science. To learn more about SRC, visit here: http://sharkresearch.rsmas.miami.edu/, or to learn more about the University’s marine science school, please click here: http://rsmas.miami.edu/.

 By Delaney Reynolds, SRC intern

Best Track Positions for Hurricane Hermine

Figure 1: Best Track Positions for Hurricane Hermine. This map is a composite of the best predicted tracks of Hurricane Hermine between August 28th and September 3rd, 2016. Offshore of western Florida, it transformed from a tropical storm to a hurricane, making landfall as a category one hurricane, and then transitioning back into a tropical storm as it made its way across the state into the eastern waters off Maryland. (Source: Berg 2017).

In September of 2016, Hurricane Hermine struck Florida as a category one hurricane and then migrated through Georgia, South Carolina, North Carolina, and then to offshore Maryland. According to the National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental Information (NCEI), Hermine’s damage “totaled around $550 million, with a 90% confidence interval of +/- $150 million” and demolished 1,600 homes and businesses (Berg 2017). But how did it affect offshore fish populations? Researchers from the University of Maryland designed an experiment to find out.

Four months before Hermine hit Florida, 45 black sea bass were acoustically tagged and acoustic receivers were moored in the shelf waters of three different sites off Maryland; a northern, middle, and southern site. Rash winds of Hurricane Hermine caused destratification, “a process in which the air or water is mixed in order to eliminate stratified layers of temperature, plant, or animal life,” in the water column of the Mid-Atlantic Bight.  Due to this disarrangement, temperatures of northern and middle experimental sites rose 10 degrees Celsius in just ten hours creating an unsuitable environment for living organisms and, thus, either migration or death of the black sea bass was expected.

Black Sea Bass Population Size, Summer 2016

Figure 2: Black Sea Bass Population Size, Summer 2016. This graph exhibits the decay in population size of black sea bass between the three experimental sites. The two vertical, black, hash-marked lines indicate September 2nd – 6th. All three experimental sites showed a decline in black sea bass populations and by January of 2017, all three populations had diminished completely. (Source: Secor et al. 2017).

Researchers discovered that 40% of the sea bass populations had evacuated the experimental sites in search of a more suitable habitat and any that stayed behind exhibited decreased activity levels showing that there were large behavioral changes due to the increased temperatures. Evacuation was found to be highest in the northern and southern sites and lower in the middle site and in most cases, migration was permanent. Although some recovery was indicated in the two weeks following Hermine, water column stratification and black sea bass population sizes did not return to normal (Secor et al. 2017).

Although hurricanes are just one of the factors contributing to the emigration of fish species, as our planet continues to warm, hurricanes are predicted to become more intense and more frequent potentially leading to even larger emigration phenomena which would ostensibly take a large toll on the fishing industry. According to the Fisheries Economics of the U.S. 2011 report, recreational fishing in the South Atlantic generates 52,000 jobs and adds $3 billion to the United States’ GDP (Back in Black). Due to their importance to our economy and the threats that they face, it will be imperative to monitor black sea bass and fisheries to ensure that measures are being taken to stabilize the economy when their performances decline.

Works cited

Berg, Robbie. “Hurricane Hermine.” National Hurricane Center Tropical Cyclone Report, 30 Jan. 2017.

Secor, D. H., Zhang, F., O’Brien, M. H., & Li, M. (2018). Ocean destratification and fish evacuation caused by a Mid-Atlantic tropical storm. ICES Journal of Marine Science.

USA Department of Commerce, 27 Sept. 2013. “Back in Black: Black Sea Bass Stock Is Rebuilt.” Accessed from: www.commerce.gov/news/blog/2013/09/back-black-black-sea-bass-stock-rebuilt.

Coral Bleaching of the Great Barrier Reef

The following article first appeared on the Research Blog for Dr. Neil Hammerschlag’s Shark Research and Conservation (SRC) Lab website at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science. To learn more about SRC, visit here: http://sharkresearch.rsmas.miami.edu/, or to learn more about the University’s marine science school, please click here: http://rsmas.miami.edu/.

By Delaney Reynolds, SRC intern

Coral reefs are some of planet earth’s most spectacular, diverse and important ecosystems. Our planet’s coral reefs provide important shelter, habitats, and a source of food for many different species of marine organisms. They also act as a critical food source to humans, as well a natural barrier to help protect our coastlines from hurricanes and associated storm surges. Sadly, coral reefs face growing risks including the possibility of extinction from a variety of stresses that leads to coral bleaching.

Coral Bleaching

Figure 1: Coral from which the zooxanthellae has been expelled, causing it to turn white (Image Source: http://en.wikipedia.org/wiki/File:Keppelbleaching.jpg)

Coral bleaching is the process in which zooxanthellae, algae living symbiotically within the coral, are expelled from coral colonies due to a number of factors including an increase in temperature, decrease in pH, exposure to UV radiation, reduced salinity, and bacterial infections. Zooxanthellae provide the coral 30% of its nitrogen and 91% of its carbon needs to the coral host in exchange for a shelter, as well as waste produced by the coral from nitrogen, phosphorus, and carbon dioxide that is required for the algae’s growth (Baird, 2002).

When corals bleach, it effects entire marine communities due to their immense diversity. Fish populations that reside around coral reefs “are the most species dense vertebrate communities on earth, contributing critical ecosystem functions and providing crucial ecosystem services to human societies in tropical countries” (Graham, 2008). Researchers have found that when an ecosystem endures physical coral loss, fish species richness is extremely likely to decline due to their heavy reliance on the coral colony itself (Graham, 2008).

Perhaps the most famous current example of coral bleaching is Australia’s Great Barrier Reef. Scientists have determined that the main cause of Great Barrier Reef coral bleaching is induced thermal stress and that about 90% of the reef has been bleached since 1998 (Baird, 2002). As the corals bleach and temperatures increase, researchers have determined that shark and ray species that live in the area may be vulnerable to these climactic changes.

Exposure of Ecological Groups of GBR Sharks and Rays to Climate Change Factors

Figure 2: Exposure of Ecological Groups of GBR Sharks and Rays to Climate Change Factors. This figure displays the vulnerability different elasmobranch species face due to climate change, as well as the specific effects of climate change that they are vulnerable to, in the specific zones of the Great Barrier Reef. (Image Source: Chin et al. 2010)

Most of the Great Barrier Reef is located on the mid-shelf of the ocean floor, the approximate mid-point between the shallower coast of Australia and the continental shelf where the ocean bottom significantly drops in depth. Researchers found that the mid-shelf is the area where most of the shark species studied reside, while most rays dwell in coastal waters or closer to the continental shelf. It was also found that both areas are the susceptible to rising temperature, increased storm frequency and intensity, increasing acidity, current alterations, and freshwater runoff, all being caused by climate change (Chin, 2010). Based on these findings, researchers have concluded that the areas these elasmobranchs live in should be protected and preserved. Species in these highly vulnerable areas should also be monitored and considered for future conservation actions, as many of the shark species are already experiencing the effects of climate change from some of the aforementioned factors.

Typically, sharks are considered some of the strongest animals on earth, and while they have lived on earth for at least 420 million years, they are slow to adapt. This slowness has impeded their ability to survive in our rapidly changing climate. In the near future it will be common to see some species of marine organisms demonstrate plasticity, the ability to adapt to their changing environment, but other species, such as elasmobranchs, are expected to simply distribute to other habitats in search of cooler waters. Even though sharks are a highly vulnerable species to climate change, they sit at the top of the trophic level in many different niches and, thus, wherever they migrate to, it will be easier for them to find food than it would be for other species such as fish or rays. However, this is most likely only the case for adult sharks as embryos and juvenile sharks may be more vulnerable to increased temperatures. For instance, researchers found that the survival of bamboo shark embryos decreased from 100% at current temperatures to 80% under future ocean temperature scenarios and that the embryonic period was also shortened, not allowing the embryo enough time to develop fully (Rosa, 2014).

To decrease the effects of climate change on coral bleaching, corrective and mitigation measures can be taken. By utilizing green energy sources such as implementing solar power or wind power, walking or biking, and driving electric cars, we can reduce our use of fossil fuels and carbon footprint, thus decreasing the amount of carbon dioxide polluting and warming our atmosphere and oceans. While underwater and not always visible, coral reefs are truly a vital part of our ecosystem and need to be cherished and protected for generations to come.

References

Baird, A. H., & Marshall, P. A. (2002, July 18). Mortality, growth and reproduction in scleractinian corals following bleaching on the Great Barrier Reef. Retrieved from https://researchonline.jcu.edu.au/1521/1/Baird_and_Marshall_2002.pdf

Chin, A., Kyne, P. M., Walker, T. I. and McAuley, R. B. (2010), An integrated risk assessment for climate change: analyzing the vulnerability of sharks and rays on Australia’s Great Barrier Reef. Global Change Biology, 16: 1936–1953. doi:10.1111/j.1365-2486.2009.02128.x

Graham, N. A., McClanahan, T. R., MacNeil, M. A., Wilson, S. K., Polunin, N. V., Jennings, S., . . . Sheppard, C. R. (2008, August 27). Climate Warming, Marine Protected Areas and the Ocean-Scale Integrity of Coral Reef Ecosystems. Retrieved from http://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0003039

Rosa, R., Baptista, M., Lopes, V. M., Pegado, M. R., Paula, J. R., Trubenbach, K., . . . Repolho, T. (2014, August 13). Early-life exposure to climate change impairs tropical shark survival. Retrieved November 2, 2017, from http://rspb.royalsocietypublishing.org/content/royprsb/281/1793/20141738.full.pdf

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