Monday, April 22, 2013

US Geological Survey study helps inform rigs-to-reef plans

The idea of turning old offshore drilling rigs into artificial reefs has been floating around for a while, and US Geological Survey scientists recently reported that there’s no sign that fish living near the rigs are contaminated by oil from the drilling operations.

To help provide some baseline data for “rigs-to-reef” proposals in California, the agency compared contaminant levels in fish living around oil platforms with fish from nearby natural sites off the coast of California in the Santa Barbara Channel and the San Pedro Basin. The new and recent USGS reports are available online.

“As part of this study, we developed methods capable of detecting the extremely low levels of contaminants that we anticipated in these ocean fishes, especially since they avoid natural oil seeps,” said USGS scientist Robert Gale. “These results will assist decision-makers in helping to protect the environment off the coast of California.”

Some of the most important contaminants related to oil operations are polycyclic aromatic hydrocarbons (PAHs). Several PAHs are probable human carcinogens and many are toxic to fish and other aquatic life. Scientists were able to develop a new, more accurate method of sampling small traces of PAHs that may have been ingested and broken down within the fish. Samples were taken from species thought to be most sensitive to PAH contamination.

The tested species included Pacific sanddab, kelp rockfish and kelp bass, all targeted by fishermen. PAH concentrations were either very low or undetectable in all fish sampled for this study.

The underwater portion of many offshore oil and gas platforms often provides habitat to a large number of fish and invertebrates. Under the rigs-to-reef management option, resource managers would maintain some of the submerged structure to function as an artificial reef after oil and gas production has ended.

“These important results suggest two things,” said marine biologist Donna Schroeder, with the Bureau of Ocean Management. “First, existing offshore oil platforms provide food and shelter to local fishes without increasing their background contaminant loads. Second, since there is no detectable PAH signal from ongoing operations, we would expect that if the State of California wanted to implement a rigs-to-reefs program, there would likely be no change, pollution-wise, in the quality of the offshore environment, which appears to be pretty good.”

Scientists also looked at industrial chemicals in the Pacific sanddab species, including polychlorinated biphenyls (PCBs), flame retardants (polybrominated diphenylethers, PBDEs), and pesticides (OCPs). These contaminants were also found at low levels in all fish sampled, with no observed pattern between natural and platform habitats.

Source: Summit County Voice. Author: Bob Berwyn

Image courtesy of jkbrooks85 via Flickr (CC BY 2.0)