Ecological quality boundary-setting procedures: the Gulf of Riga case study |
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Authors: | Juris Aigars Bärbel Müller-Karulis Georg Martin Vadims Jermakovs |
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Institution: | (1) Latvian Institute of Aquatic Ecology, Daugavgrivas 8, 1048 Riga, Latvia;(2) Estonian Marine Institute, Viljandi Rd. 18b, 11216 Tallinn, Estonia |
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Abstract: | Two approaches for setting ecological class boundaries, response curves and a simplified mathematical boundary-setting protocol,
were tested for coastal, transitional and open waters in the Gulf of Riga, Baltic Sea. The simplified mathematical boundary-setting
protocol defines acceptable ecological status based on expert judgment by a uniform relative deviation from reference conditions.
In contrast, response curves derive class boundary definitions from observed changes in biological quality elements along
environmental pressure gradients for class boundary definitions. Identification of relevant environmental pressures for the
construction of response curves was based on a conceptual model of eutrophication in the Gulf of Riga. Response curves were
successfully established for summer chlorophyll a and transparency, as well as for macrozoobenthos abundance in the Central
Gulf, macrozoobenthos biotic coefficient in the Southern Gulf, and maximum depth of phytobenthos in the Northern Gulf. In
the Gulf of Riga response curves almost always permitted a larger deviation from reference conditions than the 50% deviation
applied for the simplified mathematical boundary-setting protocol. The case study clearly demonstrated that class boundary
definitions should take into account the sensitivity of the target water body. Also, the class boundaries for different ecological
quality elements were internally more consistent than those derived by the simplified mathematical boundary-setting protocol. |
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Keywords: | Ecological quality Quality boundaries Assessment methods |
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