A view of Portland, Me.'s inner harbor, on a pier steps away from the office of Friends of Casco Bay. Credit: Emily J. Gertz

Gazing last week at a geological map of Maine's island-strewn Casco Bay, it was easy to imagine that a continent-sized creature had dug a claw deep into the land, scraped it back at an angle (in the general direction of the North Atlantic), and let the ocean run back in around the ridges and bumps that remained.

The map was hanging on a wall at the South Portland headquarters of Friends of Casco Bay, one of the organizations I visited during my field trip to the Maine coast. My sci-fi-esque idea turned out to be somewhat aligned with reality; the enormous bay, its inlets, and its islands were created when (if I understand the geological history correctly) the Laurentide Ice Sheet scoured the contiment as it receded from terminal point on Long Island, New York, between 21,000 and 16,000 years ago.

FCB was doing citizen science before the concept had a name. The group has enlisted around 600 "citizen stewards" over 19 years to measure the bay's temperature, salinity, dissolved oxygen levels and more indicators of marine health, from points all around the region. The longevity of the data allows the group to establish baselines for the bay's condition, as well as using the findings to guide its efforts with policymakers, agencies, groups, and Maine communities to conserve and improve Casco Bay's condition. Volunteer coordinator Peter Milholland believes that it may be the largest and longest-term sampling program run by any group in the nation.

Lately FCB's focus has been on nitrogen pollution. Excess nitrogen flows down the Saco River and into the bay from both inland sources -- like agricultural runoff -- and on-water sources like big cruise ships dumping sewage .

One consequence of excess nitrogen can be "red tides" -- massive algal blooms fed by the nitrogen. As the algae die, their decomposition uses up the oxygen in the water, a disastrous outcome for marine life along all sections of the food web.

Red tide organisms also release a substance that's lethal to mammals, and may have factored into a mass die-off of seals in the northeast in 2004. 

Mike Doan, the group's research associate, told me he recently added measurements of pH to FCB's roster of data points. Relatively broad shifts in acidity near shore might indicate pollution problems. But overall ocean acidification -- a consequence of the ocean absorbing excess carbon dioxide from the atmosphere -- is happening on a much finer scale.  He wants several years of steady measurements in order to begin drawing conclusions about ocean acidification off the Maine coast. 

Gathering this data, he says, will require testing materials much more sensitive than the pool-testing kits he and FCB's citizen stewards are currently using.