Many different things, both unnatural and natural, affect the marine food web and ecosystems, but recently, scientists at the National Oceanic and Atmospheric Administration (NOAA) decided to study the Gulf of Mexico and determine how both natural and human activities affect such systems there.
The group of scientists studied data on topics such as economics, fishing, the environment, ocean temperature, currents, atmospheric patterns, harvesting and revenues. After three years of collecting a wealth of information, they discovered that the Gulf of Mexico saw a major shift in its ecosystem around 1995, which is when there was a natural change in climate.
This climate change, the Atlantic Multidecadal Oscillation (AMO), occurs every 20 to 40 years when the climate of this part of the ocean switches between cool and warm phases. From 1965 through 1995, the Gulf of Mexico was in a warm phase, but in 1995, it shifted to cool. These phase changes affect everything in the area, including number of droughts and the intensity of hurricane activity.
Unfortunately, though, scientists rarely research the AMO, and this new study is one of the first to look at how the AMO affects the Gulf of Mexico.
"These major ecosystem shifts have probably gone unrecognized to date because they are not apparent when considering single species or individual components of the ecosystem," says Dr. Mandy Karnauskas of NOAA's Southeast Fisheries Science Center. "Only when we put a lot of things together — including currents, hypoxia, fish abundances, fishing effort and more — does a strong climate signal emerge."
Not only did scientists find a shift in ecosystems in 1995, they found another previously in the 1970s, shortly after the passing of the U.S. Magnuson-Stevens Fishery Conservation and Management Act, which established new laws for fishing in U.S. waters.
Other human activities also affect the ecosystem, such as oil spills and agricultural run-off, as well as natural occurring storms and hurricanes.
Scientists hope their research helps others in maintaining the Gulf of Mexico's food web and ecosystems by helping them understand exactly what affects those systems.
"The hypotheses presented here should provide focus for further targeted studies, particularly in regard to whether and how management should adjust to different climate regimes or states of nature," write the authors of the study. "Our study highlights the challenges in understanding the effects of climatic drivers against a background of multiple anthropogenic pressures, particularly in a system where these forces interact in complex and nonlinear ways."
Photo: NOAA | Flickr
