In the afternoon, Dr. Michael Johnson, recently retired Director of the Aquatic Ecosystems Analysis Laboratory at UC Davis, gave a presentation on “Contaminants in the Delta and their Potential Role in Shaping Biological Communities.”
He said that there was insufficient data to conclude that contaminants were partially or wholly responsible for the pelagic organism decline (POD) from 2000-2008. Effects must be from the trophic structure (which relates to energy in levels in the food chain).
Dr. Johnson found that there were major fish kills even before the POD. In a list of contaminants, it was interesting to see that from 1986-2008, by far the highest contaminant count was for selenium, with boron in second place. Selenium, though, is not a pelagic issue, according to Dr. Johnson.
Dr. Johnson identified 900 different chemical contaminants, including pesticides and antibiotics. There is lots of copper (perhaps from old mining operations) and lots of Prozac. But there is no consistent data for fish exposure. And some species are thriving.
An interesting side note: Dr. Johnson showed bar graphs with spikes in early- to mid-summer for a spray used to prevent hull split in almonds. If the hulls split, insects can get in and aflatoxin can grow. Europe won’t accept almonds with split hulls, and Europe is where a lot of California almonds go.
So we’re putting toxins in our water so that we can export our almonds to Europe.
Dr. James Cloern, Senior Research Scientist with the USGS, presented a “Historical Perspective on Human Disturbance in the Sacramento-San Joaquin Delta Ecosystem.” The species decline, he said, is decades long and not the result of a single factor. Humans have been transforming the landscape since the 19th century, turning complex, shallow habitat into a simplified canal system with deep, turbid water that doesn’t let sunlight in to grow food for aquatic organisms.
Dr. Cloern noted that all large rivers are now dammed, allowing us to manipulate salinity in ways that favor non-indigenous species. He mentioned increases in exports, introduction of non-native species, bacterial blooms, and toxic contaminants as all contributing to ecosystem decline. He cautioned against focusing on just one stressor, and announced that he disagreed with the conclusions of his colleague Dr. Patricia Glibert, of Horn Point Laboratory at the University of Maryland, who has focused her attention on ammonia in wastewater effluent.
Professor Glibert herself spoke next. She was formerly on the NAS committee, but resigned this spring after releasing her research, which was funded by water exporters. (Her PowerPoint presentation acknowledged David Fullerton of Metropolitan Water District.) Her presentation examined the ratio of nitrogen to phosphorus and its effect on algae changes in the Delta. Her argument was that as nutrients in the water changed over time, so did dominant species. But in response to questions from her colleagues, she agreed that the issue of nutrients needed to be viewed in the context of the system’s overall complexity.
The committee also heard from Dr. Donald Weston of UC Berkeley on the subject of pyrethroids and other pesticides.
Two themes emerged: There isn’t enough data about the interaction of stressors; and there’s hardly enough time to get this whole thing right.