On Thursday, we explored how climate change can impact marine ecosystems in a number of ways including temperature and ocean circulation changes. For elasmboranchs and other species which are constrained to specific habitat requirements, dispersal capabilities, or even seasonal and oceanographic events, climate change may pose a huge threat to these populations (Perry, Low, Ellis, & Reynolds, 2005).
A perfect example are the whale sharks (Rhincodon typus) of Ningaloo Reef on the Western coast of Australia. These sharks’ seasonal aggregation has been directly linked to temperature (Wilson, Polovina, Stewart, & Meekan, 2006; Wilson, Taylor, & Pearce, 2001). The whale sharks travel hundreds, sometimes thousands, of miles to Ningaloo Reef to feed on spawning corals (Wilson, et al, 2001). However, as ocean temperatures continue to rise, as do the number of coral bleaching epidemics (Stewart & Wilson, 2005). If these bleaching events continue at their alarming rates, there is evidence to suggest that these seasonal oceanographic events may be significantly altered, which may impact the timing or even the magnitude of the whale sharks’ seasonal migration patterns (Chin, Kyne, Walker, & McAuley, 2010).
Barnwell, C. [National Geographic]. (2016, January 28). Watch: Putting a Camera on a Whale Shark | Expedition Raw . Retrieved April 11, 2017, from https://www.youtube.com/watch?v=Z3CwHFJhdkE&w=560&h=315
As you might expect, corals are not the only source that may be affected by climate change. As I mentioned previously, changes in ocean circulation may change upwellings. Upwellings of nutrient rich waters from the deep is what ultimately allows for primary production in the oceans and that productivity goes all the way up the food-web. If shifts in the currents occur, areas which were once rich in prey availability may become scarce (Chin, et al., 2010). Just as the absence of sharks can cause top-down trophic cascades in an ecosystem, the absence of abiotic nutrients in an ecosystem can cause a bottom-up trophic cascade, where the bottom of the ecosystem pyramid falls away and causes the collapse of the entire ecosystem (Gericke & Stump, 2016).
You have the ability to make change. By making small changes in your daily routine, such as reducing emissions, saving energy, and recycling, you are supporting climate change initiatives.
But it is going to take social and political changes to bring about global changes needed to save species from extinction. The best thing you can do at any time is call your Congress man or woman and tell them that you care about climate change initiatives and keeping sharks in our oceans!
Next time, we will move away from climate change and take a hard look at how our fisheries industry has impacted elasmobranchs in the last century.
The new Ocean For Sharks Shop is open! There’s handmade ocean inspired plush animals, canvas paintings, and of course my children’s book, Winifred the Wondrous Whale Shark, available in print and PDF. Be sure to stop by. Remember proceeds benefit shark research and conservation with a donation to Project AWARE!
I welcome your comments and feedback! Thanks for following my blog series!
Featured Image Source
Whale Sharks Migration [Digital Image] (n.d.) Retrieved from https://www.oceanenterprises.com/data/dive-travel/photos/455.jpg
Chin, A., Kyne, P. M., Walker, T. I., & McAuley, R. B. (2010). An integrated risk assessment for climate change: Analysing the vulnerability of sharks and rays on Australia’s Great Barrier Reef. Global Change Biology, 16(7), 1936–1953.
Gericke, R., & Stump, K. (2016, April 2). Introduction to Ecology. Lecture presented at Marine and Island Ecology in Shedd Aquarium, Chicago. Retrieved from https://drive.google.com/open?id=0B4gsOD5FF7S8a21fZ2JDZy1hY0E
Perry, A. L., Low, P. J., Ellis, J. R., & Reynolds, J. D. (2005). Climate change and distribution shifts in marine fishes. Science, 308(5730), 1912–1915.
Stewart, B., & Wilson, S. (2005). Threatened fishes of the world: Rhincodon typus (Smith 1828)(Rhincodontidae). Environmental Biology of Fishes, 74(74), 184–185.
Wilson, S. G., Polovina, J. J., Stewart, B. S., & Meekan, M. G. (2006). Movements of whale sharks (Rhincodon typus) tagged at Ningaloo Reef, Western Australia. Marine Biology, 148(5), 1157–1166.
Wilson, S. G., Taylor, J. G., & Pearce, A. F. (2001). The seasonal aggregation of whale sharks at Ningaloo Reef, Western Australia: Currents, migrations and the El Niño/ Southern Oscillation. Environmental Biology of Fishes, 61(1), 1–11.