Development of a lake pollution monitoring system using periphyton in the littoral zone of Lough Gill

Periphyton is a complex mat, predominantly made up of algae, found attached to submerged\ud surfaces in the photic zone of a waterbody. In the early 1990's this brown substance was\ud observed to cover plants, stones and most submerged surfaces around the shoreline of Lough\ud Gill in NW Ireland. Analysis of the water indicated a mesotrophic system, however such a\ud substantial growth of periphyton warranted further investigation. A monitoring programme was\ud established with six sample sites spread around the littoral zone. Three artificial substrates were\ud used to measure periphyton; glass slides, trays of washed stone and a plastic substrate (to\ud simulate the macrophyte Littorella uniflora). Substrates were submerged for periods of 1 month\ud from February 1997 to May 1998. Phytoplankton samples were also collected.\ud Diatoms always dominated the biomass on slides, with peaks during spring and autumn. Green\ud and blue/green algae became prominent in the summer and autumn. Diatom genera included\ud Cymbella, Gomphonema, Nitzschia and Synedra. Chlorophyta included Chaetophora,\ud Stigeodonium and Utothrix, and the main Cyanophyta were Anabaena and Aphanocapsa. During\ud 1997 periphyton biomass from glass slides ranged from 25 g/m2 (May) to <1 g/m2 (November),\ud in the same period AFDW ranged between 14 g/m2 and