The Marin Municipal Water District has taken another significant step toward building a saltwater desalination facility to stabilize their water supplies, but critics remain adamantly opposed to the project.

Paul Heliker (right), General Manager of the MMWD, believes that the desalination facility is needed to protect Marin residents from possible future droughts and the economic havoc they could cause.

Sharp questions about the safety and purity of the desalinated water were raised again at this week’s water district meeting, but Heliker says those concerns should have been settled by the results of the district’s own tests of the reverse osmosis technology with the same water that the larger plant would use.

Adam Scow, California Deputy Director for water programs for the national consumer advocacy group, Food and Water Watch, is among the vocal skeptics who question the need and cost of the proposed desalination plant. He points to a report commissioned by his organization that disputes the underlying assumptions the district uses to make its case for the project. You can read that report here.

For its part, the district has prepared a 9-page slide show on their desalination project, which is much easier to digest than the full Environmental Impact Report, which is posted here. At left is a map showing where the proposed plant would be situated.

A complex interaction between native crabs and oysters and invasive Atlantic snails (seen at left)  is playing out beneath the waters of Tomales Bay.

 Dr. David Kimbro has studied the predatory effects of invasive Atlantic snails on native Olympia oysters in Tomales Bay. He explains how they arrived there more than a century ago.

There also native Pacific snails in Tomales Bay, but unlike their invasive (or as scientists say "introduced") Atlantic cousins (right), the local snails have learned how to safely coexist with the snail-eating red rock crabs (below). UC Davis biologist Ted Grosholtz explains.

The smaller, green European crab, another introduced species in Tomales Bay, can handle the less salty water in the shallow portions of the bay, but because they will eat a wider variety of foods, these crabs have not developed the same skills for preying on snails that the red rock crabs display.

The long-running debate over an historic oyster farm in Drakes Estero, within the  the Point Reyes National Seashore,  has jumped from western Marin County to Washington D.C., and shows few signs of cooling off.

Fredrick Smith, Executive Director of the Environmental Action Coalition of West Marin says that, Senator Feinstein's statements to the contrary, he fears that her legislative intervention on behalf of the Drakes Bay Oyster Company will set a bad precedent that could have wide implications.

The fate and future of the Drakes Bay Oyster Company and the Estero has been a long-running and hotly debated issue in the Point Reyes area for years. Recent developments have been chronicled by the Point Reyes Light.

The gorgeous airborne view of the estuary below was taken by Sonoma-based pilot and photographer Robert Campbell . See more of his work here .

The most harmful form of mercury is being washed into coastal waters through subsurface groundwater, a new study has found, and at rates far higher than from the air. That research was conducted at two Northern California sites, including Stinson Beach (right) in Marin County.

When we hear about mercury levels in fish, the actual compound is a form called mono-methyl mercury. U.C. Santa Cruz biochemist Dr. Adina Paytan (left) explains the difference, and what is known about how it gets converted.

Mercury washes out of the atmosphere more of less uniformly, but levels of bacteria in groundwater tend to vary widely. Dr. Paytan points to coastal areas with failing septic systems as likely sources for higher concentrations of subsurface methyl mercury.

While the biochemical conversion process can occur anywhere that mercury exists alongside the active bacteria, researcher Frank Black (standing, right) says the degree to which the methylated mercury is then carried into the ocean water depends a lot on the subsurface geology of a particular area.

Here's a source for background reading on Mercury in the Environment.