Impacts of Fishing: Sediment Plumes from Bottom Trawling
Satellite images showing one of the impacts of bottom trawling, a type of commercial fishing that drags weighted nets across the seafloor. In shallow, coastal areas with a muddy seafloor, trawling raises clearly visible plumes of sediment that persist for hours. The effects of this constant resuspension of sediment are poorly understood, but potentially severe: toxic substances buried in the mud, from industrial pollution and agricultural runoff throughout the Gulf of Mexico and Mississippi River watershed, are continually being reinjected into the water and the foodchain, with as-yet unknown implications for public and environmental health.

Most of these images are showing sediment plumes raised by trawling for shrimp in the northern Gulf of Mexico, off the coasts of Texas and Louisiana. But other fishing methods can stir up the ocean bottom as well -- we've included a couple of images from the Yangtze River delta in China that show sediment plumes emanating from nets that are fixed in place. In this case, a strong current causes turbulence around the nets and churns up the muddy plumes.

Thanks go to our partners in this work at the Marine Conservation Biology Institute (http://mcbi.org/), and to Dr. Kyle Van Houtan at Emory University who first made us aware of these plumes in satellite images (http://webdrive.service.emory.edu/users/kvanhou/public_html/index.html).
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