Climate Variation and Marine Food Chains

by mmccalli on November 10, 2017 - 2:01pm


Over the past century, our marine ecosystems have been rapidly changing. This has altered the population dynamics of various species and had critical ecological consequences. A new study in the journal, Science Advances has found chemical clues in the skin cells of dolphins that suggest changes in  the length of the marine food chain. Because dolphins occupy the upper level of the food chain, they accumulate chemical information about the species that occupy the rest of the food chain.

Intense climate disturbances like El Nino Southern Oscillations have led to unusual warming in the pacific coast of North America and the shortening of food chains in places like the California Current. This shortening of the food chain corresponded with a sharp decline in the marine productivity in the area. There was a decrease in plankton, fish, and birds. Some other species like jumbo squid had to expand in range to find food sources and more favourable conditions and temperatures. By increasing the range of predators, these impacts were compounded. When predators become more desperate for food, they reduce the length and the diversity of the food chain even further. Other, less nutrient rich species such as jellyfish and tunicates might grow in population as these vacant spaces in the food web grow. Still, most predators will not pursue these abundant species as food and this will almost certainly not create an equally diverse food chain. Global warming is known to increase the intensity of El Nino events and other disturbances. As these events intensify, they will pose a greater risk to marine biodiversity.

How this Changes Our Understanding of Marine Ecosystems

Until recently, marine food chains were considered by most scientists to be relatively stable long-term. This study challenges this belief that the same species will continue to feed on each other under changing conditions. This new understanding of marine food chains will help scientists understand the health and resilience of the ecosystem. A longer food chain is reflective of a relatively more diverse ecosystem and a transition to a shorter food chain signals extreme environmental conditions and declining biodiversity. This was the first study to document marked changes in the pelagic food web length in response to various natural and anthropogenic stressors. It emphasises the dynamic and fragile nature of marine ecosystems.

Why this is important

As the climate continues to change, variations in nitrogen cycling, productivity, dissolved oxygen concentrations, and extreme weather events will create unexpected repercussions. It is important to recognize the range and complexities of the ways in which global warming is impacting ecosystems. This study demonstrates how little we know about the unexpected ramifications of global warming. For this and many of reasons, I am hesitant to accept things like the 2 degrees of warming target of the Paris agreement. This target creates a boundary point at which climate change will create “catastrophic” impacts. But who decides what is catastrophic and what is acceptable? There could be so many missing pieces in climate models that we rely on for cost-benefit analysis. I think that regardless of whether or not we will meet our climate targets, we need to recognize the possibility of unknown feedback loops and interconnected systems.


NOAA Fisheries West Coast Region. "Climate shifts shorten marine food chain off California: Research counters earlier thinking that food chains remain constant through time." ScienceDaily. 19 October 2017. Retrieved from:


Rocio I. Ruiz-Cooley, Tim Gerrodette, Paul C. Fiedler, Susan J. Chivers, Kerri Danil, Lisa T. Ballance. “Temporal variation in pelagic food chain length in response to environmental change”. Science Advances, 2017; 3 (10): e1701140 DOI: 10.1126/sciadv.1701140