Variation of structural and functional metrics in macrophyte communities within two habitats of eastern Mediterranean coastal lagoons: natural versus human effects

Abstract

1. The variation of structural (multi-dimensional scaling plot of Bray–Curtis similarity, species number, Shannon–Weaver index, percentage coverage) and functional (Ecological State Group (ESG) I percentage coverage, ESG II percentage coverage, Ecological Evaluation Index (EEI)) metrics in benthic macrophyte communities was studied in two different habitats: (a) mud with submerged angiosperms (MA), and (b) mud with macroalgae (MM), in three eastern Mediterranean coastal lagoons. One lagoon was in northern Greece (Agiasma, Nestos Delta, Eastern Macedonia region) and two in south-eastern Italy (Cesine and Margherita of Savoia, Apulian region). 2. The aim was to differentiate metric variation caused by human or natural processes and thereby to (1) select reliable metrics and (2) develop user-friendly protocols for cost-effective monitoring programmes for coastal lagoon water quality. 3. Eight different sites dominated by macrophyte communities characterized by two angiosperms (Ruppia cirrhosa and R. maritima), two opportunistic macroalgae (Ulva sp. and Chaetomorpha linum), and Cyanobacteria colonies were quantitatively and destructively sampled twice. 4. Structural metrics showed highest heterogeneity at a local site-specific scale, while functional metrics showed highest heterogeneity at the scale of habitat. As a result the structural metrics appeared inappropriate as indicators of lagoon water quality changes. By contrast shifts of habitat dominated by angiosperms to opportunistic macroalgae owing to nutrient excess, especially nitrogen, can be identified by functional metrics, especially with EEI. Copyright © 2008 John Wiley & Sons, Ltd.