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1 December 2004 Evaluation and Emergy Analysis of the Cobscook Bay Ecosystem
Daniel E. Campbell
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A naturally eutrophic, estuarine ecosystem with many unique features has developed in Cobscook Bay over the past 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 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 this ecosystem network were analyzed in terms of the solar emjoules (emergy) required to support primary and secondary production. In Cobscook Bay there is an extraordinary convergence of emergy, 7.4E 12 sej m −2, from renewable sources. This level of emergy is one of the highest natural empower densities that we have found. Eighty-four percent of this emergy is from the tides and wave action. Transformities calculated in this analysis show 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 subtidal zone along the shore. Phytoplankton production is less efficient apparently due to light limitation, but phytoplankton and resuspended benthic microalgae support highly productive beds of filter feeders. Empower density in Cobscook Bay is similar to that required elsewhere for intensive fish culture; therefore, aquaculture may be a good human use of the rich convergence of natural emergy found there. The nitrogen entering Cobscook Bay from salmon culture is 19% of the net annual flux of new nitrogen entering from the coastal waters. The Bay's great resource wealth supports economic activities such as salmon culture and commercial dragging for scallops and urchins that, in turn, alter the concentrations of nutrients and suspended sediments locally in the Bay and may cause increased sedimentation and changing benthic communities in the Bay as a whole.

Daniel E. Campbell "Evaluation and Emergy Analysis of the Cobscook Bay Ecosystem," Northeastern Naturalist 11(sp2), 355-424, (1 December 2004).[355:EAEAOT]2.0.CO;2
Published: 1 December 2004
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