Tuna Carbon Ratios Reveal Shift in Food Web
Link to article: https://www.sciencedaily.com/releases/2019/11/191113153033.htm
The article, Tuna Carbon Ratios Reveal Shift in Food Web, discusses how the ratio of carbon isotopes in tuna has caused the species to change substantially since 2000. These changes indicated that major shifts have also been taking place in the phytoplankton populations: which are the populations that form the underlying structure of the ocean’s food web. According the study cited in the article, the changes occurring may be driven by increased ocean stratification, which is an impact of climate change.
The study cited in the article analyzed almost 4,500 samples of muscle tissue from 3 species of tuna in the Atlantic, Pacific, and Indian Oceans between 2000 and 2015. The team conducting the study led by Nicolas Cassar of Duke University discovered that the fishes’ carbon stable isotope composition values (the ratio of Carbon 13 to Carbon 12 or delta C-13) declined by between 0.08% and 0.25% during the period of the study.
The study was conducted by analyzing carbon and nitrogen stable isotope ratios in yellowfin, bigeye, and albacore tuna which were caught in tropical, subtropical, and temperate waters.
The large delta C-13 values for phytoplankton such as diatoms may be outflanked by phytoplankton cells, which have a natural competitive advantage in lean times; according to the analyses of the scientists. While the long term impacts are not yet fully understood, the distances that tuna fish travel means that they could integrate changes in the food web structure over very large spatial scales.
The effects on tuna fish are an application of a concept that we learned in class called the 6 degrees of separation. The idea of 6 degrees of separation says that there are a maximum of 6 connections (or edges) between 2 different people in a network. Global warming effects the temperature of the oceans, which effects the carbon stable isotope composition values in tuna fish, which causes changes in the food web structure on a vast scale due to their travels in the ocean. The fact that temperature increases in the ocean could effect such a variety of nodes in the food web is fascinating, and part of what this article explores.