There is little difference in heavy metal pollution levels between fish living around oil and gas production platforms and those around natural sites, a new study reports.
Published in the Bulletin of Marine Science, the findings show all but four elements were relatively consistent at both locations.
For the study, scientists collected a total of 196 fish—18 kelp bass (Paralabrax clathratus), 80 kelp rockfish (Sebastes atrovirens), and 98 Pacific sanddab (Citharichthys sordidus)—from five offshore oil platforms and 10 natural areas during 2005 and 2006.
Samples were taken at 19 sites between the Santa Barbara Channel in the north and Long Beach in the south. Three of the offshore islands—Santa Cruz, Anacapa, and Catalina—provided some of the natural sites.
Of 63 elements, 42 were excluded from statistical comparisons because they were not detected during analysis, were detected at concentrations too low to yield reliable quantitative measurements, or were deemed unlikely to accumulate to potentially toxic concentrations. None of the remaining 21 elements consistently exhibited higher concentrations at oil platforms than at natural areas.
For one species of fish, the Pacific sanddab, small fish around oil platforms had lower levels of three elements, selenium, titanium, and vanadium, whereas larger platform fish tended to have higher levels of these three elements. In addition, larger fish tended to have more tin at natural areas but more copper at platforms.
“We are mystified and have no explanation for that,” says Milton Love, research biologist at University of California, Santa Barbara’s Marine Science Institute. “It may have to do with different feeding habits between juveniles and adults, but we just don’t know.”
Twenty-seven active and seven decommissioned offshore platforms are located within the study area.
There is great debate about what to do with decommissioned platforms. While decommissioned oil platforms in Southern California have historically undergone complete removal, “recent ecological studies indicate that platforms provide artificial structure for marine life, including many fish species of recreational and commercial importance, and may contribute to rebuilding overfished stocks.”
The federal government, which oversees most of the platforms off California, is looking down the road to the time when these platforms become uneconomical to operate, Love says. “No one knows when that will be. It is a purely economic decision, much of it driven by the price of oil.
“The state of California has a law that says that complete removal may not be necessary,” he explains. “It’s possible that the state will require owners to cut the platforms below the waterline and leave the rest as reefs. In that process, there are questions that have arisen over and over again: Are these fish polluted in some way? Are we leaving a structure filled with polluted fish?”
This study begins to answer that question. The findings do not support the hypothesis that oil platforms off California are major sources of trace element contamination in resident marine fish.
“In science, nothing answers anything definitively,” Love says. “Because you can never know the truth; all you can do is approach the truth.
“All we can say is that based on this one study, heavy metal pollution does not seem to be an issue around the platforms we sampled.”
Source: UC Santa Barbara