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Effects of thermal discharge from Neka power plant on macrobenthic diversity and abundance was studied in the southern coast of the Caspian Sea. Samples were collected with Van Veen grab of 0.0250 m 2 surface area from 7 stations in winter and summer. A total of 42 species were identified that belonged to 22 genera, 18 families, 13 orders, six classes and three phyla. Bivalve with a total abundance of 90% in winter and 86% in summer constituted the most abundant group throughout samplings, the highest abundance of which belonged to the family Cardiidae. Gastropods followed bivalve in total abundance (8%) in summer and polychaetes (7%) in winter. Statistical analysis indicated significantly higher macrobenthos density at the thermal discharge stations that also took separate positions in the cluster analysis. Temperature was an important factor on the amount of organic matter. Chlorophyll and phaeopigment at the thermal discharge stations were lower than the other stations because of the increased turbulence. The CCA test indicated that temperature was the most influential among all the studied physicochemical factors. The Spearman rank correlation coefficient also showed that the majority of macrobenthic groups had a positive correlation with the organic matter (r = 0.34, p < 0.05). Macrobenthic species were grouped according to their commonalities relative to these three classes using a Bray-Curtis similarity index and similarity profile (SIMPROF) permutation tests analysis (PRIMER 6). Based on the SIMPER analysis, the cockle Hypanis minima and the polychaete Hypaniola kowalewskii with high abundances played the most important role in making differences among the stations, but won’t be taken as the “thermal indicating species”. The PERMANOVA test showed that the combination of season and stations had a significant effect. The density of macrobenthos was higher in the thermal discharge stations, but diversity in these stations reduced in comparison with the other stations. [ABSTRACT FROM AUTHOR]

While the impact of ocean warming on single species is well described, the impact on marine biofouling communities is not well understood. Effluents of power plants have higher temperatures and can be used as natural large-scale test sites to investigate warming effects on marine ecosystems. In the present study, we evaluated the impact of elevated temperatures in the vicinity of a power plant on macro-biofouling communities in the northern coast of the Persian Gulf. The impact site was on average 2 °C warmer than the control site. Our results demonstrate a significantly different structure and composition of biofouling communities between control and impact sites. Warming led to a 1.5-fold increase in the mean coverage of biofouling communities and slightly decreased functional and species richness. Our results indicated that future warming will likely increase biofouling pressure, while decreasing diversity of communities, particularly in habitats where organisms exist at their upper tolerance limits of temperature. • Structure and composition of biofouling communities were different between control and impact sites. • Warming led to a 1.5-fold increase in the mean coverage of biofouling communities. • Warming slightly decreased functional and species richness of biofouling communities. • Future ocean warming will likely increase biofouling pressure in the northern Persian Gulf. [ABSTRACT FROM AUTHOR]