Abstract

Coastal lagoons are considered naturally stressed systems that experience frequent environmental variations. Benthic macrophyte and macroinvertebrate species were studied seasonally in two coastal lagoons (Kotychi and Prokopos) in Western Greece to investigate spatial and temporal biodiversity patterns. <em>Ruppia cirrhosa, Potamogeton pectinatus</em> and Chironomidae were dominant in both lagoons, while Kotychi was also dominated by <em>Lekanesphaera monodi</em> and <em>Monocorophium insidiosum</em>, and Prokopos by Ostracoda and Lekanesphaera monodi. Species richness, diversity, and abundance of benthic macroinvertebrates were strongly related to aquatic macrophytes and to the degree of communication with the marine environment. Moreover, species richness and abundance of both macrophytes and macroinvertebrates were mainly dependent on depth, temperature, pH and total suspended materials (TSM). Based on the preliminary results of this study, it appears that the ISD index, based on the biomass size structure of the macroinvertebrate communities, is an appropriate tool for ecological quality assessment.