Citation:

Campbell, D E. EMERGY ANALYSIS OF THE COBSCOOK BAY ECOSYSTEM. Presented at 6th Bay of Fundy Workshop-Bay of Fundy Ecosystem Partnership, Cornwallis Park, NS Canada, September 29 - October 2, 2004.

Description:

A naturally eutrophic, estuarine ecosystem has developed in Cobscook Bay over the past three to four thousand years under the influence of six meter tides and rich flows of nitrogen from the deep waters of the Gulf of Maine. In this paper, measurements of primary production and water column properties that were made in the Bay from 1995 to 1996 and information from past studies are used to construct an energy systems model of the Bay's ecosystem and to evaluate the annual flows of energy and matter coursing through this network. The properties of the ecosystem network were analyzed in terms of the solar emergy required to support primary and secondary production. In Cobscook Bay, there is an extraordinary convergence of renewable emergy, 7.4 E12 sej m -2; one of the highest empower densities that we have found in natural ecosystems. This analysis shows that emergy is being used most effectively to support populations of large brown alga (i.e., Ascophyllum nodosum, Fucus vesiculosus, and Laminaria longicruris) and the diverse community of benthic organisms that thrive in the intertidal and shallow sub-tidal zone along the shore. Phytoplankton production is less efficient, but suspended microalgae support highly productive beds of filter feeders. Empower density occurring naturally in Cobscook Bay is similar to that required elsewhere for intensive fish culture. Aquaculture, therefore, may be a good human use of the rich convergence of natural emergy found in the bay. The nitrogen entering Cobscook Bay from salmon culture was estimated to be about 19% of the net flux of nitrogen entering from the coastal waters as nitrate. Cobscook Bay's great wealth of marine resources supports economic activities, such as, salmon culture and commercial dredging for scallops and urchins that, in turn, have altered the concentrations of nutrients and suspended sediments in the water apparently causing increased sedimentation and changing benthic communities.

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