Spatial and temporal patterns of benthic macrofauna in Gorgan Bay, south Caspian Sea, Iran

We quantified the distribution, abundance and assemblage structure of macrofauna at ۲۲ stations in Gorgan bay, seasonally in ۲۰۱۲-۲۰۱۳. Also, depth, temperature, salinity, DO, TOM and sediment particle size were measured in each station. The highest concentration of TOM was measured near the western littoral zone (۱۰.۲۲) while the mouth part and north-eastern area was characterized by the lowest values (۲.۶۵ % and ۴.۶۹). A total of ۳۱۶۵۸ individuals belonging to ۱۲ families and ۱۴ species were identified. Polychaeta with ۳ species was the most dominant group in terms of abundance. The four most abundant taxa making up ۸۵% of all specimens were Streblospio gynobranchiata, Tubificidae, Hediste diversicolor and Abra segmentum. The maximum density (۷,۸۹۳ ind/m۲) was obtained at station ۱ while the minimum (۱,۷۷۷ ind/m۲) was observed at station ۱۶. The western area was characterized by the highest species diversity (H', ۱.۹۴) and the stations ۱۰, ۸ and ۷ were characterized by the lowest diversity indices (H', ۰.۷۲, ۰.۷۷ and ۰.۸۷, respectively). The PCA showed that water parameters with more temporary variations had a greater significance in explaining the system variability, and a not marked but evident difference between the two parts of Gorgan Bay was observed and supported by nmMDS test. So Gorgan Bay presents transitional macrobenthic assemblages that are spatially distributed along substrate gradients but it seems that the coastal ecosystem of the south Caspian Sea and mouth-eastern part of Gorgan Bay is very dynamic and some species are forming a metapopulation toward western sites.

Keywords:

Spatial , Temporal , Benthic macrofauna , Metapopulation , Gorgan Bay