From the Raleigh "paper":
Hans Paerl, a professor at the UNC Institute of Marine Science, is leading an effort to learn the value of the Pamlico Sound and other coastal waters in absorbing greenhouse gases. Data gathered about the Pamlico will be stored for scientists worldwide who want to see how the sound responds.
In the Pamlico, life thrives in the mix of saltwater and freshwater. The sound is rich in tiny plants that soak up carbon dioxide, a gas that in excess contributes to warming of Earth's atmosphere, scientists say. Waterborne plants release greenhouse gases when they decompose.
In addition to loving, just loving, North Carolina ferry rides, I know that the social cost of carbon (SCC*) is about $21 (rising to $45 by 2050 ... just ask Frank Ackerman). Once those folks at UNC add up the carbon dioxide (CO2) stored by the Pamlico Sound, I could then be brought in to find the economic value (EV). I'd use this formula: EV = SCC x CO2/ton (with MS Excel, of course). And I'd only use point estimates.
*The present value of avoiding the damages of climate change per ton of carbon dioxide.