AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS Aquatic Conserv: Mar. Freshw. Ecosyst. 18: S16–S26 (2008) Published online in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/aqc.955 Environmental factors affecting Phragmites australis litt decomposition in Mediterranean and Black Sea transitional F. SANGIORGIO a, *, A. BASSET a , M. PINNA a , L. SABETTA a , M. ABBIATI b , M. PONTI b , M. MINOCCI c , S. ORFANIDIS d , A. NICOLAIDOU e , S. MONCHEVA f , A. TRAYANOVA f , L. GEORGESCU g , S. DRAGAN g , S. BEQIRAJ h , D. KOUTSOUBAS i , A. EVAGELOPOULOS i and S. REIZOPOULOU l a Department of Biological and Environmental Sciences and Technologies, University of Salento, Lecce, Italy b Interdepartmental Centre of Research for Environmental Sciences, University of Bologna, Bologna, Italy c Department of Biology, University of Trieste, Trieste, Italy d National Agricultural Research Foundation, Kavala, Greece e Department of Zoology and Marine Biology, University of Athens, Athens, Greece f Institute of Oceanology, BAS, Varna, Bulgaria g European Excellence Centre for the Environment, University ‘Dunarea De Jos’, Galati, Romania h Faculty of Sciences, University of Tirana, Tirana, Albania i Department of Marine Sciences, University of the Aegean, Mytilini, Greece l Institute of Oceanography, Hellenic Centre for Marine Research, Anavyssos, Greece ABSTRACT 1. Leaf litter decomposition rates in aquatic ecosystems are known to be related to many abiotic and biotic factors. 2. Field experiments were carried out during spring 2005 in 16 ecosystems, each with four sampling sites, u the litter bag technique to investigate the influence of abiotic factors on patterns of reed litter breakdown in different physiographic, hydrological and physico-chemical gradients occurring in transitional water ecosystem in the Eastern Mediterranean and Black Sea. 3. Significantdifferences in leaf litter decomposition were observed among the studied ecosystems along univariate gradients of tidal range, water temperature, salinity and sinuosity index. 4. Overall, 71% of variance in the litter breakdown rate was explained by the hydrological, physico-chemical and physiographic components. Specifically, tidal range, salinity and sinuosity index are among the key factor the mostcommonly used typological schemes for classifying transitional water ecosystems (i.e. Confinement Concept and Venice System), due to their influence on abundance and distribution of benthic macroinvertebra and other guilds. 5. The patterns observed at the regional scale of the study suggest that certain key abiotic factors are likely play a major role as drivers of plant detritus decomposition processes, through their influence on the overall metabolism of microorganisms and benthic macroinvertebrates. *Correspondence to: Franca Sangiorgio,Laboratory of Ecology,Departmentof Biologicaland Environmental Sciencesand Technologies (DiSTeBA), University of Salento, SP Lecce-Monteroni, 73100 Lecce, Italy. E-mail: franca.sangiorgio@unile.it Copyright # 2008 John Wiley & Sons, Ltd.