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.

Just as doctors move quickly to detect and treat infectious diseases before they can spread, botanists and habitat managers are teaming up to use the same approach against invasive weeds in the Bay Area.

California Invasive Weeds Awareness Week (CIWAW)is July 20-26, 2009. This  an annual event that brings attention to the problems caused by invasive plants in California (such as the yellow star thistle, shown in flower at right), and to the work of local groups that work to protect our natural areas and rangelands. In 2004, the state legislature signed a proclamation declaring California Invasive Weeds Awareness Week to begin the third Monday of July each year.

Arundo dorax, above, spreading rapidly in the middle reach of the Russian River, and threatening to become established downstream as well.

Dan Gluesenkamp, is Director of Habitat Protection and Restoration for the multiple preserves owned and managed by Audubon Canyon Ranch, explains that the basis methods employed by the BAEDN are those used by his and other, like-minded organizations, but scaled up to work on a regional basis.

Additionally, says Gluesenkamp, the new parternship is dedicated to operating in accordance with two key core principles.

Goals of the Bay Area Early Detection Network include:

• Have effective detection efforts covering the nine counties.
• Ensure that detections are supported with sufficient response funds to eradicate priority invaders while still cost-effective.
• Increase effectiveness and strategic nature of invasive plant work in the region.
• Involve and train citizen detection partners.
• Realize a coordinated system of regional Early Detection networks across all California.

In Sonoma County, ludwigia is one of the most conspicuous invasive plants, growing agressively in the Laguna de Santa Rosa and in slow-moving portions of the Russian River, as seen in the foreground below.

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.