As sea surface temperatures continue to rise, sharks may exhibit phenotypic plasticity (non-genetic, physiological or behavioral responses to changing environmental cues) in an attempt to maintain their current ecological role in the environment. Being able to better cope with changing conditions would allow sharks to maintain function and continue to play their current roles in the ecosystem. However, phenotypic plasticity can only allow for relatively small amounts of compensation compared to compensation available through prolonged periods of evolution in novel environments. It is also important to note that phenotypic plasticity is not reliable due to being innate and organismal capability varying. That is to say some sharks may be better able to demonstrate this ability while some sharks may have much reduced ability for alteration in accordance to change. The factors listed above help demonstrate that while phenotypic plasticity can help, it is probably not a long term answer for sharks around the world.
Another option for sharks is to adjust their diet as it becomes harder to cue migration in accordance with seal breedings. Switching to another prey base would allow for changes in migration times and routes, while alleviating the loss of food source from the mistiming with seal breeding. While in theory prey switching could help solve the problem of food source loss with white sharks, there may not a viable option to switch to. White sharks in South Africa feed almost exclusively upon marine mammals (mostly seals) once they reach maturity. Seals are the only reliable and attainable candidate for marine mammals in this ecosystem for sharks to feed on. Unfortunately, as climate warming stresses the trophic relationship between white sharks and cape fur seals in southern Africa, prey switching seems to not be a viable option for white sharks.
White shark disappearance
One more negative possible outcome in the near future is the possibility of white sharks disappearing from the region. If waters in False Bay, Mossel Bay, and other areas throughout the South African coastline warm to levels outside the thermal optimum for white sharks, they may no longer return. As stated previously in this blog, financial and ecological ramifications will echo throughout southern Africa if this apex predator is removed from the environment. Further studies to better understand when this disappearance may occur, as well as what humans can do to help prevent this from occurring, need to be encouraged.
This blog has only covered the tip of the iceberg on the topic of climate change affecting the marine ecosystems in southern Africa. I really hope it can help to raise some awareness and concern to the problems tomorrow's world faces due to increasing rates of climate change.