Periphyton growth as an indicator of eutrophication; an experimental approach |
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Authors: | Johanna Mattila Reetta Räisänen |
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Abstract: | Growth of periphyton was studied in the Archipelago Sea (Finland) during summer 1994 as a part of the annual monitoring control
of fish farms. Experimental growth plates (Whatman GF/C filters) were incubated (two weeks) at 213 sites in different parts
of the Archipelago Sea and in the coastal area north of the Archipelago Sea. At each site incubations were repeated two or
three times during the summer (July 4- -September 1). The growth of periphyton was measured as the amount of chlorophyll a
(mg m-2) extracted from the incubation plates.
The growth varied significantly among different parts of the study area. The strongest growth was observed in the inner archipelago
and in areas with high fish production and relatively slow water exchange. In the outer archipelago, rapid water exchange
ensured good mixing of nutrients from fish farms and other sources into relatively large water volumes. The local impacts
of nutrient loading thus remained too low to be detected by measuring nutrient concentrations or periphyton growth.
Periphyton growth was positively correlated with concentrations of total nitrogen, total phosphorus and chlorophyll a in the
productivity layer (approximately 2 × Secchi depth). A significant inverse correlation was also shown between periphyton growth
and Secchi depth.
Archipelago areas with different levels of eutrophication could satisfactorily be distinguished in this study. The results
were consequent with previous classifications of the eutrophication levels in the Archipelago Sea. Periphyton studies thus
are a useful addition to conventional monitoring programs.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | eutrophication monitoring periphyton the Archipelago Sea Baltic |
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