Climate Change: Seasonal Changes Impacting Migration

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).

Manta Ray
Cieslak, B. (Photographer) (2008, January 13). Manta Ray [Digital Image] Retrieved from https://upload.wikimedia.org/wikipedia/commons/0/06/Manta_ray_from_Yap.jpg

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).

bottom up
Gericke, R., & Stump, K. (2016, April 2). Bottom-Up Regulation [Digital Image]. Retrieved from https://drive.google.com/open?id=0B4gsOD5FF7S8a21fZ2JDZy1hY0E

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.

Climate Change
Sustainability for All [Digital Image] (n.d.) retrieved from http://www.activesustainability.com/climate-change/6-actions-to-fight-climate-change/

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.

I welcome your comments and feedback! Thanks for following my blog series!

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Featured Image Source

Whale Sharks Migration [Digital Image] (n.d.) Retrieved from https://www.oceanenterprises.com/data/dive-travel/photos/455.jpg

Literature Cited

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.

 

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9 thoughts on “Climate Change: Seasonal Changes Impacting Migration

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    1. Linda that’s an incredible difficult question to answer. If upwellings are disrupted by shifts in ocean currents, it could lead to complete collapse of primary production which would cause bottom-up trophic collapse of ecosystems. So could they potentially learn and find new food sources, yes if there are new food sources to find. Could they adapt to change? K-species like shakes and rays are slower to adapt to change, than r-species like bony fishes. However they have survived 5 mass extinctions in the past. They are capable of surviving natural events. What we are causing is not a natural event and these are highly complex issues.

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      1. Totally, and totally agree. My mind is sort of going … well if their environment – the seas are changing, that would have an ongoing effect of every sea / seas in the world!? For instance, I wonder if the seas around England let’s say would warm up enough to harbour some of the species you are talking about!? What I have are thoughts and questions mulling over in my mind – I love to look at what maybe the unknown at present and pose questions. I see the world, climates and different environments changing – which isn’t ideal by any measure at all. I believe we need to look, be aware and take care of this planet. But also I ponder over the changes and wonder about what chain reactions we may see happening … hope you get what I mean? Love your blog and learning about things btw 😊👍

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