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You thought you knew all there was to climate change – until now. Researchers have uncovered yet another factor that is contributing to the rate of climate change. Could removal of top predators from our oceans really be affecting our earth’s climate? The answer may surprise you.

The Makeup Of Our Ocean Contents Could Be Shifting

The fisheries industry has long since exhibited unsustainable practices to catch their prize. It is no surprise that because of this, numerous commercial fisheries are suffering. Fish typically captured by fisheries aren’t the only fish feeling these pressures. Shark populations are dwindling, as the demand for shark fins to make soup in the Far East is still a force. If these trends continue, the makeup of our oceans could look very different in fifty years. In fact, several studies predict that jellyfish and plastic waste will makeup the bulk of the ocean’s contents.

Ocean Food Chain Dynamics

A diagram of an ocean food chain.

A diagram of an ocean food chain.

Although it is no new news that the changing climate is taking a toll on some of our most cherished ecological communities, there is little known on the reverse effect. A recently released study (Spiers, K.A. et al, 2016) shows how removing top-chain predators can result in large-scale ecosystem effects, including increased oceanic carbon dioxide production. Since a majority of the fish captured by the fisheries industry are top predators, these practices along with shark finning decreases the total number of top predators available. The study hypothesized that “this removal of predators is likely to lead to an increase in ocean ecosystems’ CO2 production, and ultimately that fishing and shark finning are contributing to climate change” (Rick Stafford, The Conversation).

Energy and Biomass Transfer Within Food Chains

To understand the impact that removing predators will have on the remaining organisms in the ecosystem, its important to gain an understanding of energy and biomass transfer within a food chain. When a predator consumes a prey species at the next level down, the predator only gains 10% of the biomass of the prey it consumes. This is because energy transfer within food chains is very inefficient. For example, if a shark consumes a smaller fish, only 10% of the biomass of the fish is available to the shark.

This diagram shows how removing top predators would increase the numbers of lower-level populations, in turn increasing carbon dioxide production.

This diagram shows how removing top predators would increase the numbers of lower-level populations, in turn increasing carbon dioxide production.

If we remove top predators, it will upset the balance of the populations in the food chain. Removing top predators would result in an increase in abundance in the lower level populations. Not only are the low level populations increasing, the biomass increase of these lower levels could be up to 90% more than the actual weight of the predators removed. With this shift, more respiration would occur, creating a greater production of carbon dioxide. Although the researchers note that their study is only based on a theoretical model, there have been studies on the role that top predators play in carbon production.

“Green” Whales

Saving whale populations could slow the speed of climate change.

Saving whale populations could slow the speed of climate change.

In addition to the role that sharks and other large-fish predators play in climate change, studies show that whales may also play a role. They have been termed “green whales.” Whales reduce the carbon dioxide levels in the sea by providing nutrients for the phytoplankton, or microscopic marine plants. When thriving and healthy, these marine plants absorb carbon dioxide. The whales are able to transport essential nutrients found in lower layers of water that normally would not make it to the phytoplankton at the upper levels. They do this by feeding deep down and defecating close to the surface where phytoplankton live. The healthier the phytoplankton are, the less carbon dioxide present in the ocean. Therefore, by removing large whales, we risk increasing the oceanic carbon dioxide levels as well.

Summary

It is key to keep in mind that organisms are part of a larger ecosystem that functions at its best when balanced. Abusing ocean ecosystems means much more than simply running out of fish to eat. The need for shark fins for soup continues in many areas of the world, and is taking a toll on shark populations. By creating sustainable practices for fisheries and decreasing shark finning, we can create a two-fold positive effect by increasing these beloved, enigmatic fish, while decreasing levels of oceanic carbon dioxide at the same time.

Sources:

https://theconversation.com/how-overfishing-and-shark-finning-could-increase-the-pace-of-climate-change-67664

http://www.sciencedirect.com/science/article/pii/S1574954116301820

http://www.bbc.co.uk/education/guides/z2m39j6/revision/6

http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/greenworld/energyflowrev1.shtml

 

Image Sources:

Shark swimming with fish: https://myoceannews.wordpress.com/2011/07/15/decline-world-top-predators/

Food Chain: https://www.pinterest.com/pin/42221315230352565/visual-search/?x=0&y=9&w=564&h=400

Top predators and CO2 production: https://theconversation.com/how-overfishing-and-shark-finning-could-increase-the-pace-of-climate-change-67664

Blue Whale: http://www.bayschools.com/pkes/LibraryMediaCenter/StudentSites/BlueWhale.aspx