Pollutants ride ocean food chain to the top

Okay, one more pulse of news about pollutants. A batch of recent studies find “persistent organic pollutants” (including the previously blogged PCBs, or polychlorinated biphenyls) in tissues of a startlingly wide array of seabirds. And if seabirds sound comfortably esoteric to you, remember that you’re probably eating higher up on the seafood chain than they are.

First, there’s this report of PCBs and pesticide byproducts in glaucous gulls in the Norwegian Arctic. Contamination was strong enough to have an apparent effect on levels of the sex hormone progesterone – but only in male glaucous gulls. The difference, the authors say, may come down to metabolic pathways that differ between the sexes.

But another possibility is that females pass along some of the contaminants to their eggs – as northern fulmars appear to do in a recent Canadian study (and as women do in breast milk).

Most of these persistent organic pollutants don’t occur naturally, so it’s hard for us humans to avoid the finger of blame. The connection between pollution and contamination is made even more interesting in another Norwegian study, this time of lesser black-backed gulls. These authors compared one subspecies that is endangered with another subspecies that is increasing its range. The endangered subspecies had higher blood levels of PCBs and DDE than the thriving one.

If DDE has a familiar ring to it, that’s because it’s one of the most common breakdown products of the infamous pesticide DDT. What’s amazing to me is that even though DDT was banned in most of Europe in the 1970s, here it is still showing up in animals a good quarter-century later. Kind of makes you want to get tested yourself.

Switching to good old-fashioned lead, and to a rather more direct way of putting pollutants into animals, there’s a Greenland study of buckshot in common and king eiders, two of the world’s fluffiest ducks. It seems that eider hunters in Greenland shoot with a decidedly Dick Cheney-like accuracy. Scientists X-rayed about a thousand of these ducks and found that about 1 in 5 is carrying around embedded shot. King eiders seemed harder to hit, with only about 13% carrying pellets.

Searching, perhaps, for similar clues about lead levels, Alaskan biologists worried about falling duck numbers have started studying contamination in the field. They carry portable analyzers that measure lead in the blood of Steller’s eiders and black scoters. So far, I’m pleased to report, lead doesn’t seem to be a problem in these species.

(image: paulnoll.com. Thanks to SeaWeb for their free research compilations)