Climate Change effects on sea turtles

By Molly Rickles, SRC intern

Climate change has become an increasing threat to species across the planet. With hotter average temperatures and less predictable weather patterns, humans have undeniably influenced the global climate. The effects of a changing climate are translated to the ocean, where warmer sea surface temperature and rising sea level can alter the marine ecosystem on many levels. These changes can decrease biodiversity and alter the balance of marine ecosystems (Fuentes et al. 2010). These far-reaching effects have extreme consequences for marine life, but some species are impacted more than others. Sea turtles are heavily affected by climate change because of their wide range of habitats (Butt et al. 2016). Since sea turtles lay eggs on beaches but spend their lives in the ocean, they are affected by climate change on both fronts. In addition, climate change may affect survival of juvenile sea turtles, decreasing adult population numbers. Since sea turtles can be widely affected by the far-reaching effects of climate change, it is necessary to implement measures of protection for them. There are ongoing research projects to determine how climate change directly impacts sea turtles and what the best policy options are to combat these effects. This is important because there is little information on how to protect these species from the effects of climate change.

In A, the mean air temperature is shown (black points) against the mean sand temperature (white points) to show how the temperature fluctuates throughout the year. In B, the proportion of nesting by loggerhead turtles for 2005, 2007, 2008, 2009. (Source: Perez, E. A., Marco, A., Martins, S., & Hawkes, L. (2016). Is this what a climate change-resilient population of marine turtles looks like? Biological Conservation, 193, 124-132. doi:10.1016/j.biocon.2015.11.023)

Over the past forty years, sea level has risen at an average of 2mm each year (Butt et al. 2010). This is an alarming statistic especially for low-lying and coastal areas. This is also bad news for sea turtles, which lay their eggs on beaches, which have already been affected by rising sea levels. Beaches are at a high risk for flooding from sea level rise, and when this does occur, the sea turtle eggs are washed away or swamped (Perez et al. 2016). This is especially devastating for endangered species of turtles such as the Hawksbill Turtle or the Australian Loggerhead Turtle, whose numbers are already low and cannot afford a sharp decrease in reproductive output (Butt et al. 2016).

Another major threat to sea turtles is rising sea surface temperature. One of the major effects of climate change is an increase in air temperature, which correlates to an increase in sea surface temperature. This excess thermal stress has especially hard consequences for reptiles, who are exothermic animals that rely on outside temperature to regulate their internal temperature (Perez et al. 2016). An increased sea surface temperature creates a more stressful environment for the sea turtles, but the increased sand temperature has proven to be even more harmful. Since sea turtles lay eggs on beaches, the hotter sand leads to less ideal conditions for laying eggs, which leads to decreased reproductive output. In addition, the sex of the embryos is partially determined by the outside temperature. In this case, a warmer environment leads to a higher percentage of females. It has been estimated that a 2°C increase will lead to a 99.86% female hatching rate (Butt et al. 2016). This, of course, will lead to a very lopsided sex ratio within sea turtle populations, further decreasing the reproductive output and population size.

The image shows all of the nesting sites identified in Australia. This shows that sea turtles have a wide range of habitats. This is beneficial because it allows policy makers to protect certain beaches where sea turtles are known to use for nesting. (Source: Butt, N., Whiting, S., & Dethmers, K. (2016). Identifying future sea turtle conservation areas under climate change. Biological Conservation, 204, 189-196. doi:10.1016/j.biocon.2016.10.012)

All of these threats to sea turtles could have devastating effects on their populations. Decreases in sea turtle populations have already been observed, and most sea turtle species are already on the endangered species list. Due to the fact that sea turtles are dealing with a multitude of threats, it becomes increasingly difficult to find management techniques to combat these issues (Fuentes et al. 2010). Some of the more straightforward strategies deal with the sea turtle’s habitat on land, since it is easier to manage beaches than the open ocean. Since sea turtles rely on certain beaches for nesting, it is possible to protect these areas to preserve the nesting habitat (Fuentes et al. 2010). This has already been implemented in many coastal areas, where nesting sites are blocked off from public use. In addition, many coastal areas have regulations to control nighttime lighting near nesting beaches so the sea turtle hatchlings have a better chance of making it to the ocean. By protecting these important nesting areas, sea turtles will continue to be able to lay eggs safely, and more hatchlings will survive to adulthood. This will lead to an increase in sea turtle population, thus preventing their numbers from decreasing even more rapidly.

In addition to managing habitat on land, it is also important to protect sea turtles in the ocean. One way to do this is to implement marine protected areas in important habitats for the turtles, such as areas where their young mature. However, the main issue affecting sea turtles is climate change, and this must be dealt with at a larger scale. To reduce the overall impact of climate change not only on sea turtles, but every other species, it is necessary to reduce the emissions of greenhouse gases and create a more sustainable way of life. There have already been steps made towards this goal, including the Paris Climate Accord, along with numerous clean air emission standards, but it is not enough. Stricter environmental regulations and environmental conservation education will help reach a more sustainable life, as well as protect sea turtles along with a multitude of other species


Fuentes, M., & Cinner, J. (2010). Using expert opinion to prioritize impacts of climate change on sea turtles’ nesting grounds. Journal of Environmental Management, 91(12), 2511-2518. doi:10.1016/j.jenvman.2010.07.013

Butt, N., Whiting, S., & Dethmers, K. (2016). Identifying future sea turtle conservation areas under climate change. Biological Conservation, 204, 189-196. doi:10.1016/j.biocon.2016.10.012

Perez, E. A., Marco, A., Martins, S., & Hawkes, L. (2016). Is this what a climate change-resilient population of marine turtles looks like? Biological Conservation, 193, 124-132. doi:10.1016/j.biocon.2015.11.023

Coral Bleaching of the Great Barrier Reef

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.

Figure 1: Coral from which the zooxanthellae has been expelled, causing it to turn white (Image Source:

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.

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.


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

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

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

Hawaiian Monk Seal Conservation

By Abby Tinari, SRC intern

Monk seals are warm water species historically residing in the Caribbean, Mediterranean and Hawaii. Now only Mediterranean and Hawaiian populations remain, both of which are critically endangered according to the International Union of Conservation of Nature (ICUN). Hawaiian monk seals have an estimated 1300 wild individuals living around the Hawaiian archipelago.

Figure 1: A juvenile Hawaiian monk seal at French Frigate Shoals. (MarkSullivan, Wikimedia)

In the early 1800s thousands of these seals were hunted for their meat, skin and oil. At the end of the 19th century and early into the 20th, the species was thought to be close to extinction. In 1958, the first beach count of the species was conducted, and surveyors concluded that the Hawaiian monk seal had made a partial recovery (Schultz, Baker et al. 2011). This was short lived. The population has since declined and is declining 4% per year on some Hawaiian Islands. These declines are due to a low juvenile survival rate because of starvation, shark predation, marine debris entanglement, by catch, sea-level rise and intra-specific male seal aggression (Schultz, Baker et al. (2011) & Norris, Littnan et al. (2017)). These seals have been consistently monitored since the 1980s when they were placed on the endangered species list. Scientists started going to pupping grounds to tag, sample and identify individuals (Baker and Thompson 2007). The Baker and Thompson (2007) study observed that the Hawaiian monk seal population is senescing, or growing older and less reproductive. Females give birth to a single pup after a 10-11 month gestation period. She then nurses the pup for 5-6 weeks. So, reproduction rates are relatively low to begin with, plus a low survival rate in the first 2 years of life is hurting the populations long term growth rate (Baker and Thompson 2007). Norris, Littnan et al. (2017) indicated that one of the main threats to young seals, less than 2 years old, is the lack of available prey.

Figure 2: The Hawaiian Archipelago, with demarcations showing the extent of the Northwestern and main Hawaiian Islands. Place names of most islands and atolls where Hawaiian monk seals (Neomonachus schauinslandi) occur are noted. (Baker, Harting et al. 2017)

With now almost 40 years on the ICUN’s endangered and critically endangered list there have been attempts at conservation. Two of these methods include translocation and vaccination. Translocation was used in the past with mixed results, some seals survived while others unfortunately did not. Schultz, Baker et al 2011 write about using genetics among other factors to see if a population is more likely to have long term success with translocation. If subpopulations have a wide genetic diversity and many genetic differences between them, then translocation may not be the best solution and could potentially produce unfit individuals. On the other hand, less genetically diverse subpopulations would have a higher success rate with fit individuals through translocation. Hawaiian monk seals were thought to have had separate subpopulations throughout the archipelago, due to the spatial distance between the islands. After genetic analysis of over 1800 individuals over 13 years Schultz, Baker et al 2011 found that the subpopulations are genetically not statistically different, they in fact, comprise of a single population. This is good news for translocation, it could be an effective means of conservation if the new location is suitable. Norris, Littnan et al. (2017) supports Schultz’s findings. Weanling seals just learning how to hunt on their own were translocated to a new island that had an abundant amount of food and few seals. The habitat was also ideal, providing adequate depth, and bottom type for both young and adult seals to hunt successfully. There was a small difference between the resident and translocated seal survival into adulthood. This survival rate is an essential marker for a translocation program. Translocation is a great way to increase numbers and repopulate suitable locations, but other conservation methods may be equally, if not more, important to a population’s survival.

Figure 3: Stacie Robinson, a biologist with the National Oceanic and Atmospheric Administration in Honolulu, vaccinates a Hawaiian monk seal basking on the island of Oahu. (Malakoff 2016)

For the first time ever, a wild population of marine mammals is receiving a vaccine to prevent disease (Malakoff 2016). This has previously occurred in the terrestrial environment mainly to prevent the spreading of rabies in racoons and fox, but never in free-living marine mammals. The lack of genetic diversity, low population, and isolation the Hawaiian monk seal experiences makes it extremely susceptible to infection. But, these factors also make the seals a prime candidate for this vaccine. Scientists are wary of the spread of viruses in the Morbillivirus family. This genus of viruses has killed tens of thousands of seals and porpoises in the Atlantic Ocean. These viruses are easily spread and are possibly carried to the Hawaiian Islands by whales, stray seals and dogs. An outbreak among the monk seals could prove deadly and cause devastating decreases in an already struggling population. The vaccine is targeting the phocine distemper virus (PDV), which needs two shots, a first dose and then a booster 4-6 weeks later. The seals habits of “hauling out”, lying on the beach and rocks, their numbered tags, small population size and unique markings help with the recapture needed to complete the vaccine. Before the vaccines were implemented, model simulations of different scenarios were run to see if preventative vaccination would be worthwhile. Baker, Harting et al. (2017) along with Malakoff (2016) determined that preventative vaccination is the most effective way of protecting these seals from an Morbillivirus outbreak. In 2016, scientists started to vaccinate individuals at the Oahu “haul out”, as this is a midpoint between the subpopulations. 60% of the overall population would need to be vaccinated in order to prevent a local outbreak of PDV. Malakoff (2016) and Baker, Harting et al. (2017) provide some limitations to the vaccines. For future seals to be immune the vaccine will need to be continued and new pups will need to be vaccinated. These vaccines are not always available and are limited in quantity. To get to the seals, scientists must walk through tide pools and over lava rock which can be dangerous especially when dealing with wild animals. The vaccine takes over a month to provide protection which leaves the seals vulnerable. Also, the vaccines currently being used are for a different strain of PDV so this effort could be futile. Either way, this is a milestone for conservation and could be the protection the Hawaiian monk seals need to build a successful future.

Works Cited

Baker, J. D., A. L. Harting, M. M. Barbieri, S. J. Robinson, F. M. D. Gulland and C. L. Littnan (2017). “Modeling a Morbillivirus Outbreak in Hawaiian Monk Seals (Neomonachus Schauinslandi) to Aid in the Design of Mitigation Programs.” J Wildl Dis 53(4): 736-748.
Baker, J. D. and P. M. Thompson (2007). “Temporal and spatial variation in age-specific survival rates of a long-lived mammal, the Hawaiian monk seal.” Proc Biol Sci 274(1608): 407-415.
Malakoff, D. (2016). “CONSERVATION BIOLOGY. A race to vaccinate rare seals.” Science 352(6291): 1265.
Norris, T. A., C. L. Littnan, F. M. D. Gulland, J. D. Baker and J. T. Harvey (2017). “An integrated approach for assessing translocation as an effective conservation tool for Hawaiian monk seals.” Endangered Species Research 32: 103-115.
Schultz, J. K., J. D. Baker, R. J. Toonen, A. L. Harting and B. W. Bowen (2011). “Range-wide genetic connectivity of the Hawaiian monk seal and implications for translocation.” Conserv Biol 25(1): 124-132.

2017 SRC Highlights

SRC had a productive 2017. Here are some of the highlights we are proud to share with you.

  1. We published 17 research papers in scientific journals, more than any other year for SRC. These papers ranged in scientific topics from evaluating levels of mercury toxicity in sharks to understanding the physiological capture stress responses of sharks to fishing.
  2. Two of our research papers were featured on the covers of scientific journals, viewed below.
  3. We conducted over 99 research field trips out of Miami supporting our ongoing research projects.
  4. Our team brought over 1250 Citizen Scientists, mostly school kids, on our research vessels to participate in our hands-on shark science.
  5. Setting another SRC research record for 2017, this past year our team tagged and sampled 466 sharks of 11 different species, the largest being a 400 cm Great Hammerhead.
  6. Our SRC team spoke to over 2500 people in over 18 outreach events, including Tortuga Music Festival, Sandoway SharkFest, and much more.
  7. SRC hosted 3 successful public social events, sharing some of our adventures with the public while also enjoying time outside of the field and the lab.
  8. Our team presented scientific talks at several national and international conferences, including the American Elasmobranch Society. Lab Director Dr. Neil Hammerschlag presented a keynote address at the European Elasmobranch Association’s annual meeting in Amsterdam.
  9. Our research was featured in several prominent media outlets, including Discovery Channel’s Shark Week (Phelps vs. Shark) and Discovery Family (Shark Days of Summer), and Yahoo news.
  10. For the first time ever, we conducted a Summer Research Program, where college students from across the US spent several intense weeks with us in the field and laboratory conducting research.
  11. Neil Hammerschlag and PhD student Rachel Skubel traveled to the Galapagos to conduct collaborative research that will also be featured in a 2018 T.V. documentary on Discovery Channel’s Shark Week.
  12. Several SRC Masters students defended their thesis, including Leila Atallahbenson, Emily Rose Nelson, and Cameron Perry, as well as former SRC lab manager & intern coordinator, Catherine Macdonald, who defended her PhD.
  13. We launched our “Name A Shark” platform, where people from the public can make a small donation to name a tagged sharks and receive a special ID card with all the biological information of their named sharks.
  14. Our social media platforms connected new audiences, with our Twitter reaching 4,700 followers, our Facebook page reaching over 11,000 likes, and our Instagram with over 17,000 followers.
  15. We welcomed our largest class of SRC interns, 40 people made up of undergrads, graduate students, faculty, staff and dedicated volunteers.
  16. We launched several new research projects, while continuing ongoing research programs, such as our White Shark Research in South Africa, Tiger Shark Research in Tiger Beach, Bahamas, and ourUrban Shark Project aimed at investigating how urban environments may be effecting the behavior and health of coastal sharks.

  17. Directed by Dr. Neil Hammerschlag, the Shark Research & Conservation Program (SRC) is a joint initiative of the Abess Center for Ecosystem Science & Policy and Rosenstiel School of Marine & Atmospheric Science at the University of Miami. Based at UM’s Rosenstiel School, SRC conducts research primarily focused on the ecology, movement and conservation of sharks. A core component of our work is to foster scientific literacy and environmental ethic in youth and the public by providing exciting hands-on field research experiences in marine conservation biology. To learn more, visit

    Thanks to the SRC team, collaborators, and supporters for another incredible year, and lets make 2018 even better.

Dispersants: A Modern Method For Cleaning Up Oil Spills: Advantages and Disadvantages

By Nicole Suren, SRC intern

In 2010, the Deepwater Horizon oil rig in the depths of the Gulf of Mexico exploded, causing the release of approximately 500 thousand tons of crude oil into the ocean in the second largest oil spill in global history, commonly known as the BP oil spill (Fingas, 2013). This spurred constant media coverage of the spill itself, as well as the cleanup. Oil spill cleanup generally includes several main steps: first the spill is contained using booms, then oil is absorbed on a large scale and skimmed off the ocean surface using boats and large amounts of absorbent materials (often more booms), and finally materials called sorbents are added to the water to remove trace amounts of oil not visible to the naked eye. What was unique about the cleanup of the Deepwater Horizon spill was the incredibly high amount of compounds called dispersants used before and during the official cleanup. Dispersion is when fine droplets of oil are transferred into the water column by wave action or turbulence (Fingas, 2013), removing oil from large slicks at the surface and allowing it to diffuse into deeper parts of the ocean. Dispersants are compounds usually sprayed on oil slicks that promote the formation of small droplets of oil, making dispersion much easier when waves stir up the oil. BP’s heavy use of dispersants was very controversial because dispersants had never been used on such a large scale before. Scientists were uncertain about two main things: 1) the effectiveness of dispersion as a cleanup method, and 2) the potential toxicity of dispersants on their own and/or mixed with oil. Since 2010, a significant amount of progress has been made in determining the effectiveness and toxicity of dispersants.

An airplane spraying dispersants over an oil slick in the Gulf of Mexico (Source: Wikimedia Commons)

An airplane spraying dispersants over an oil slick in the Gulf of Mexico (Source: Wikimedia Commons)

The petroleum industry is confident that dispersants are helpful in cleaning up oil spills (Schrope, 2013). Independent scientists, however, have not found data on the subject to be quite as conclusive. The effectiveness of dispersants depends on a variety of factors, including the type of oil, wave energy, and the amount of dispersant added. Dispersants are never 100% effective, meaning they never cause 100% of the oil from an oil slick to disperse, and even after the initial dispersal has occurred oil can often resurface within a day or so to reform the slick (Fingas, 2013). A study funded by Exxon Mobil describes a very optimistic outlook on the effectiveness of dispersants, saying that oil degrades faster when dispersed than when on shore (degradation by bacteria can occur within a matter of weeks when dispersed, according to the study) and that despite the fact that the dispersants have been shown to remove close to 50% of the oil from an oil slick in EPA-approved lab tests, they remove closer to 95% of oil in large wave tank experiments, leading Exxon’s scientists to believe that EPA estimations of effectiveness greatly underestimate effectiveness in the field (Prince, 2015). Biodegradation is a term that describes the degradation of a material by bacteria, and it is an important concept in relation to the effectiveness of dispersants. Petroleum companies argue that the increased surface area of the oil provided by dispersants allows bacteria greater access to the oil, and therefore biodegradation can occur more quickly (Prince, 2015). However, this assessment does not take into account other materials like tar that are not so easily degraded by bacteria or dispersed. Furthermore, each species of bacteria that can use oil as a food source “can utilize only a few related compounds at most, [so] broad-spectrum degradation does not occur.” (Fingas, 2013) Since degradation is not complete, dispersed oil can then be sequestered at the bottom of the ocean in association with marine snow (organic materials that rain down to the deepest parts of the ocean from the surface). In the presence of dispersants, the amount of marine snow increases dramatically and includes droplets of oil, creating an oily sludge along the ocean floor that is not being degraded by bacteria (Justine S. van Eeenennaam, 2016).

An oil slick untreated by dispersants being cleaned up by skimmer boats. The oil appears very dark and dense from the surface. (Source: Wikimedia Commons)

An oil slick untreated by dispersants being cleaned up by skimmer boats. The oil appears very dark and dense from the surface. (Source: Wikimedia Commons)

An oil slick treated by dispersants. The color of the oil slick appears much lighter from the surface, as a lighter or coffee-colored oil slick is typical of the appearance of dispersed oil. Shown here May 6, 2010, is an aerial view of the Deepwater Horizon oil spill off the coast of Mobile, Ala., taken from a U.S. Coast Guard HC-144 Ocean Sentry aircraft. (U.S. Navy photo by Mass Communication Specialist 1st Class Michael B. Watkins/Released)

An oil slick treated by dispersants. The color of the oil slick appears much lighter from the surface, as a lighter or coffee-colored oil slick is typical of the appearance of dispersed oil. May 6, 2010, is an aerial view of the Deepwater Horizon oil spill off the coast of Mobile, Ala., taken from a U.S. Coast Guard HC-144 Ocean Sentry aircraft. (U.S. Navy photo by Mass Communication Specialist 1st Class Michael B. Watkins/Released)

Not only is this sludge problematic because it is stopping the biodegradation of the oil touted by Exxon’s study, but it is toxic to the organisms that become buried below it (Justine S. van Eeenennaam, 2016). Toxicity of dispersants is a major concern, and several studies have shown that dispersants can compound a toxic situation created by the initial oil spill. First, increased biodegradation is promoted as an ideal solution for oil cleanup facilitated by dispersants, but “the aquatic toxicity of the biodegradation products is sometimes greater than that of the parent compounds,” (Fingas, 2013) so while the dispersants themselves are less toxic than oils by a magnitude of ten (Fingas, 2013), (Prince, 2015), they facilitate the production of more toxic compounds. The Exxon study also claims that dispersants show neither androgen nor estrogen receptor activity (Prince, 2015), meaning that they do not have any effect on regular endocrine function of organisms that consume or come in contact with them. While this is true for the dispersants used in the Deepwater Horizon spill, it is certainly not true for all dispersants (Richard S. Judson, 2010). Many dispersants have also been shown to be lethal to cells in culture, suggesting that they are toxic to larger animals as well (Richard S. Judson, 2010), and they can persist in the water column for years, rather than break down quickly as predicted (Helen K. White, 2014). In short, dispersants are not innocuous tools for cleanup, but have significant environmental effects that cannot be ignored.

The main benefit of dispersants is that their use can prevent large slicks of oil from contaminating coastal ecosystems and adversely affecting sensitive species like sea birds. However, “the use of dispersants remains a trade-off between toxicity to aquatic life and saving birds and shoreline species.” (Fingas, 2013) No matter what, introducing oil to an ecosystem will adversely affect that ecosystem. Because biodegradation is a questionably effective method of oil removal from marine ecosystems, the use of dispersants is essentially humans choosing which ecosystems should be more or less adversely affected, and since we see and interact with coastal ecosystems far more than deep ocean systems it is no surprise that dispersants are used to protect coastlines. However, the ecological impact of degrading deep water ecosystems should not be underestimated, and the effect of dispersants should be monitored long-term to determine whether they should be used again.

Works cited

Fingas, M. (2013). The Basics of Oil Spill Cleanup (3 ed.): CRC Press.

Helen K. White, S. L. L., Sarah J. Harrison, David M. Findley, Yina Liu, Elizabeth B. Kujawinski. (2014). Long-Term Persistance of Dispersants following the Deepwater Horizon Oil Spill. Environmental Science and Technology Letters, 1(7), 295-299.

Justine S. van Eeenennaam, Y. W., Katja C.F. Grolle, Edwin M. Foekema, AlberTinka J. Murk. (2016). Oil spill dispersants induce formation of marine snow by phytoplankton-associated bacteria. Elsevier, 104, 294-302.

Prince, R. C. (2015). Oil Spill Dispersants: Boon or Bane? Environmental Science and Technology, 49(11), 6376-6384.

Richard S. Judson, M. T. M., David M. Reif, Keith A. Houck, Thomas B. Knudsen, Daniel M. Rotroff, Menghand Xia, Srilatha Sakamuru, Ruili Huang, Paul Shinn, Christopher P. Austin, Robert J. Kavlock, David J. Dix. (2010). Analysis of Eight Oil Spill Dispersants Using Rapid, In Vitro Tests for Endocrine and Other Biological Activity. Environmental Science and Technology, 44(15), 5979-5985.

Schrope, M. (2013). Researchers debate oil-spill remedy: oil industry maintains that dispersants should be part of routine response to deep-water blowouts. Nature, 461.

How the geographic range characteristics of a species can affect its conservation

By Elana Rusnak, SRC intern

For many of us scientists, our end goal is conservation of our target species. But what does this mean, and how do we reach these goals? Unfortunately, the answer to this question is not cookie-cutter and requires the input of multiple factors that are not so easily or frequently studied.

At the largest scale, the two broad measurements of geographic range can either provide too much or too little area to be taken into account with regards to protecting a certain species: the extent of occurrence (EOO) and the area of occupancy (AOO). The area of occupancy is all the local area in which a species has been recorded, but only accounts for those localized areas. It may not take into consideration the other hospitable habitat in which individuals simply haven’t been recorded yet. The extent of occurrence is generally larger; as it encompasses all of the area a species could possibly live in, including the space between the recorded individuals (Gaston, 1991). The debate between area of occupancy and extent of occurrence may yield different results, which could cause complications especially with policymakers. While it may seem ideal to cover as much habitat as possible in order to protect a species, it is expensive and requires a lot of enforcement, therefore making it difficult for policymakers to go only on extent of occurrence, since it might include habitat in which the species does not ever reside. However, it also might include area in which a species is migrating, but only during a small part of the year. Why would they want to spend valuable resources to protect an area that does not need to be protected? For example, the White Ibis has year-round populations along the coast of the southern United States and Mexico, as well as a population in northern South America. They are migratory birds, and spend part of the year more inland in the United States, yet it is only a few months of the year (The Cornell Lab of Ornithology, n.d.). If these birds were to become endangered, it is likely that there would be conflicts in determining how much of the yearly range should be protected and why.

The area of occupancy of the White Ibis (Eudocimus albus) (

The area of occupancy of the White Ibis (Eudocimus albus) (

The extent of occurrence of the White Ibis (Endocimus albus) (

The extent of occurrence of the White Ibis (Endocimus albus) (

Another factor determining the geographic range is it’s shape. The shape of the geographic range generally constrained from the North and South, or from the East and West. North-South constraints are frequently controlled by the macroclimate (ex. temperature and precipitation), whereas East-West constraints are controlled by topography and availability of suitable habitat (Brown et al., 1996).

Habitat controlled by macroclimate, creating North-South constraints

Habitat controlled by macroclimate, creating North-South constraints

Habitat controlled by topography, creating East-West constraints

Habitat controlled by topography, creating East-West constraints

A problem in present times stems from climate change, which may alter the range shape due to rising temperatures. If a northern bird’s climate suddenly becomes too warm to endure, they may move north in order to compensate. If they were protected in their original habitat, however, the protected area may not cover their new habitat, which may result in population losses. A study done by Møller et al. in 2002 indicates just that: rapid climate changes are associated with dramatic population loss of migratory birds in the Northern Hemisphere. This can be a difficult situation for policymakers, especially if the population is both moving and declining at rapid rates.

Brown et al. further describes the issues of range size and boundary by commenting on the fact that the range edge is never defined. The internal populations of a geographic range tend to be steadier, with larger, constant populations. However, the outer edges of the range are mercurial, which makes it very difficult to determine. This brings us back to the extent of occurrence vs. area of occupancy issue. While individuals are seen at the borders of ranges, or in an excluded area, it does not necessarily mean that they are within the “geographic range” of their species. Since the edges change constantly, policymakers generally need to decide if they want to protect the bulk of the population, or the entire area that they cover.

At the smallest of scales, genetics also plays a role in conservation. While species can change and evolve into different species over very long periods of time, the genetic analysis tools we have today can show that what we thought was one species is actually two. For example, the California newt (Taricha torosa) was divided into two species in 2007. The newts living on the coast keep their Latin name, while the separate species living in the sierra has been named Taricha sierrae. (Kutcha, 2007). Modern speciation events like this can also have an effect on policy. If both species are endangered, policymakers would need to protect both species instead of just the one beforehand, which leads to more money spent and another proposal to be passed.

It is no wonder, now, that policymakers take so long to get a species protected. The factors discussed above are only a few of the considerations they must take into account in order to pass a proposal supporting protecting part of, or the entire geographic range of a species. With all that being said, every bit of science contributing to conservation is important science, which is why we do it.

Literature cited

Brown, J. H., Stevens, G. C., & Kaufman, D. M. (1996). The geographic range: size, shape, boundaries, and internal structure. Annual review of ecology and systematics, 27(1), 597-623.
Gaston, K. J. (1991). How large is a species’ geographic range?. Oikos, 434-438.
Møller, A. P., Rubolini, D., & Lehikoinen, E. (2008). Populations of migratory bird species that did not show a phenological response to climate change are declining. Proceedings of the National Academy of Sciences, 105(42), 16195-16200.
Shawn R. Kuchta (2007). “Contact zones and species limits: hybridization between lineages of the California Newt, Taricha torosa, in the southern Sierra Nevada”. Herpetologica. The Herpetologists’ League. 63 (3): 332–350. doi:10.1655/0018-0831(2007)63[332:CZASLH]2.0.CO;2.
The Cornell Lab of Ornithology. (n.d.). White Ibis. Retrieved March 25, 2017, from