Factors and criteria to quantify coastal area sensitivity/vulnerability to eutrophication: Presentation of a sensitivity index based on morphometrical parameters

摘要

There are major differences in sensitivity or vulnerability to anthropogenic loading of nutrients (eutrophication) among different coastal areas. The aim of this work is to discuss criteria for coastal area sensitivity and to present a sensitivity index (SI). This index is based on two morphometric parameters, which can be determined from simple bathymetric maps. (1) The topographical openness (or exposure) and (2) the dynamic ratio of the coastal area. The exposure is defined by the ratio between the section area of the coast and the enclosed coastal area. The boundaries of the coastal area should not be defined in an arbitrary manner but according to the topographical bottleneck method so that the exposure attains a minimum value. The exposure regulates the theoretical water retention time, which, in turn, regulates the effects of a given nutrient loading. The dynamic ratio is defined by the ratio between the square root of the coastal area and the mean depth. The dynamic ratio influences many fundamental internal transport processes. Coastal management should focus remedial actions on critical coastal areas which are at hand if the nutrient loading is high and/or the sensitivity is high. Testing the sensitivity index using a comprehensive data set including 478 coastal areas from the Baltic Sea. There were 2 (0.4%) extremely sensitive coastal areas (SI > 50), 50 (10.5%) very sensitive coastal areas (10 < SI < 50), 121 (25.3%) sensitive coastal areas (5 < SI < 10), 301 (63.0%) low sensitive coastal areas (1 < SI < 5) and 4 (0.8%) not sensitive coastal areas (SI < 1).