Author: blattner.5

“Hey! Turn that light off!” – Sea Turtles and Light Pollution

Sea turtles (Cheloniidae and Dermochelyidae families) are beloved by many, featured in animated kids movies like Finding Nemo as well in many viral videos showing newly-hatched babies scurrying into the ocean. Many people who live near them know they are endangered and care about them. What they don’t know is that their back porch light to their beach house is causing trouble. Artificial light pollution is a relatively new threat for sea turtles, disrupting many of their physiological functions.

Florida’s beaches are where many sea turtle species call home, nesting under the sand in the dunes. As beach tourism in the state continues to grow, more and more artificial light is spreading along the coastline, threatening these nesting sites. The artificial light disrupts the turtle’s circadian rhythm, confusing them if it is nighttime or daytime, making them more vulnerable to nocturnal predators who catch them unaware (Hu et al., 2018). In addition, when baby turtles are hatching, light pollution can disorient them during their dash to the ocean (Long et al., 2022). Geo-spacial collected data shows, however, that sea turtles are already avoiding areas of high light pollution (figure 1). Therefore, continued expansion of lights along Florida’s beaches could continue to reduce usable habitat for sea turtle nesting activities.

Figure 1. Geo-spacial map of artificial light on the Florida coast vs. density of Loggerhead turtle nests (Hu et al., 2018)

Luckily, the people of Florida have the sea turtles backs. Legislation exists that prohibits certain wavelengths of light to be visible from the beach, requiring shielding of exterior light bulbs (Mascovich et al., 2018). Education programs are also conducted to inform tourists who may be staying at a place close to the beach, informing them to turn off their exterior lights at night to protect nests. These programs are conducted with mixed success, however, with guests often still leaving their lights on throughout the night (Mascovich et al., 2018).

New lighting technology has also recently become an idea of preventing further and reducing current light pollution. For example studies show that Loggerhead sea turtles (Caretta caretta) are generally more sensitive to shorter wavelengths of light at less than 560 nanometers (Long et al., 2022). Thus, the state of Florida has been testing a new 624 nanometer lamp to use along coastal highways, to try and reduce light pollution that highways create. A study conducted by Long et al. showed that these new lamps DO work, with hatching turtles finding their way to the ocean just fine (2022).

Overall, while these solutions do work, they are not strictly enforced. There must be more legislative action and encouragement to use higher frequency light near the nesting locations to reduce light pollution.

References:

Hu, Z., Hu, H., & Huang, Y. (2018). Association between nighttime artificial light pollution and sea turtle nest density along Florida coast: A geospatial study using Viirs Remote Sensing Data. Environmental Pollution, 239, 30–42. https://doi.org/10.1016/j.envpol.2018.04.021

Long, T. M., Eldridge, J., Hancock, J., Hirama, S., Kiltie, R., Koperski, M., & Trindell, R. N. (2022). Balancing human and sea turtle safety: Evaluating long-wavelength streetlights as a coastal roadway management tool. Coastal Management, 50(2), 184–196. https://doi.org/10.1080/08920753.2022.2022974

Mascovich, K. A., Larson, L. R., & Andrews, K. M. (2018). Lights on, or lights off? hotel guests’ response to nonpersonal educational outreach designed to protect nesting sea turtles. Chelonian Conservation and Biology, 17(2), 206. https://doi.org/10.2744/ccb-1299.1

Mercury in the Arctic: An Invisible Threat to Polar Bears

Mercury is the famous metal that is liquid at room temperature that was commonly found in old fashioned thermometers. While it is cool to look at in chemistry class, mercury is very toxic to humans as well as animals causing damage to your brain and nervous system. Mercury pollution in the environment is mostly as a result of industrial activity such as burning coal, releasing into the air, and then depositing in aquatic ecosystems in the form of methylmercury (Dietz et al. 2013). Methylmercury eventually finds itself in fatty tissues of aquatic species and builds up as it is consumed over its lifetime, which is described as bioaccumulation (Branco et al. 2021). This is why you often hear warnings from doctors to watch your intake of ocean fish in order to avoid excessive mercury intake.

While the melting of ice caps due to global warming is the primary concern for the conservation of polar bears (Ursus maritimus), accumulation of contaminants in its body are a close second. Polar bears are a top predator in the Artic region of the planet, their diets mostly consisting of fatty seals and fish. This diet rich in fat causes them to be exposed to extremely high concentrations of contaminants of chemicals such as mercury as it travels up the food chain (Routti et al. 2013). Studies suggest that this accumulation of contaminants will cause polar bears to have weakened immune systems, making them vulnerable to disease (Routtie et al. 2013).

Mother and cubs on a small ice floe, taken near Svalbard. Image courtesy of Russel Millner and National Geographic Your Shot (2021).

High levels of mercury, in particular, can have many negative effects on polar bears. The primary danger of mercury is the risk of neurotoxicity, which is when the nervous system is damaged by toxins in the brain and brain stem (Branco et al. 2021). This can result in an impairment of many brain functions, which can impact the success of hunting. Prolonged high levels of mercury toxicity can impair mobility and the senses and can even result in the death of the polar bear (Branco et al. 2021). Studies show that developing mammals’ growth is also impaired when exposed to high levels of mercury (Branco et al. 2021).

Data shows that mercury concentrations in Arctic animals have increased over the last 150 years, showing that human activity is likely to blame (Dietz et al. 2013). This shows how our carbon emissions are continually discovered to have additional negative effects on our planet. Polar bears are amazing animals and as this blog shows, our damage to the environment is hurting and will continue to hurt them if we do not take action.

References:

Branco, V., Aschner, M., & Carvalho, C. (2021). Neurotoxicity of Mercury: An old issue with contemporary significance. Neurotoxicity of Metals: Old Issues and New Developments, 239–262. https://doi.org/10.1016/bs.ant.2021.01.001

Dietz, R., Sonne, C., Basu, N., Braune, B., O’Hara, T., Letcher, R. J., Scheuhammer, T., Andersen, M., Andreasen, C., Andriashek, D., Asmund, G., Aubail, A., Baagøe, H., Born, E. W., Chan, H. M., Derocher, A. E., Grandjean, P., Knott, K., Kirkegaard, M., … Aars, J. (2013). What are the toxicological effects of mercury in Arctic biota? Science of The Total Environment, 443, 775–790. https://doi.org/10.1016/j.scitotenv.2012.11.046

Millner, R. (2021). Will There Be Ice When We Grow Up? National Geographic Your Shot. National Geographic. Retrieved March 7, 2022, from http://yourshot.nationalgeographic.com/photos/2348856/.

Routti, H., Atwood, T. C., Bechshoft, T., Boltunov, A., Ciesielski, T. M., Desforges, J.-P., Dietz, R., Gabrielsen, G. W., Jenssen, B. M., Letcher, R. J., McKinney, M. A., Morris, A. D., Rigét, F. F., Sonne, C., Styrishave, B., & Tartu, S. (2019). State of knowledge on current exposure, fate and potential health effects of contaminants in polar bears from the Circumpolar Arctic. Science of The Total Environment, 664, 1063–1083. https://doi.org/10.1016/j.scitotenv.2019.02.030