Βenthic hydrozoan assemblages as potential indicators of environmental health in a Μediterranean Μarine protected area

The comparative study of marine benthic hydrozoan assemblages can improve our understanding of environmental and ecological conditions in marine protected areas (MPAs) such as the large Mediterranean MPA of Datça-Bozburun, where important prospects for future intensive tourism development exist. The analysis of such assemblages may help managers detect changes in important parameters of ecosystem health within this MPA. In this study we compared the hydrozoan assemblages occurring on hard (rocky) and soft (Posidonia meadows) bottoms from stations belonging to three different conditions: i) small marinas (medium anthropogenic impact), ii) yacht stopovers (low impact), and iii) unspoiled sites (no impact) in the southern part of the Datça Peninsula during summer and winter 2015 and 2016. Significant differences in the structure, species composition and richness of benthic hydrozoans among the sampling sites were detected. In both seasons, hydroid assemblages in medium-impact sites significantly differed from little-impact and no-impact sites in terms of qualitative composition. Large structural species were widely represented in all hard-bottomed sampling sites, but small inconspicuous taxa with diverse life histories were much less abundant at the medium impacted sites. Species richness and diversity in Posidonia meadows was much higher in little- and no-impact sites, where highly specific hydroid epibionts were abundant

Benthic Hydrozoans as Potential Indicators of Water Masses and Anthropogenic Impact in the Sea of Marmara

Changes in the abundance and distribution of marine benthic hydrozoan species are indicative of variations in environmental conditions in the marine realm. The comparative analysis of such assemblages can improve our understanding of environmental and ecological conditions in the Sea of Marmara, a strongly stratified and heavily populated inland sea connecting the Aegean and Black seas, on route of national and international maritime traffic. We compared the hydrozoan assemblages occurring in harbours with those developed at natural sites, as well as the assemblages associated with the Black Sea water mass versus the Mediterranean water mass in the vicinities of the Prince Islands, the north-easternmost section of the Sea of Marmara. Sampling took place at 12 stations, once in March 2015 and once in August 2015 in order to cover species with both warm and cold water affinities. Multivariate analyses showed that benthic hydroid assemblages with both affinities differed significantly between the heavily trafficked harbours of the Prince Islands (connected to the metropolis of Istanbul) and areas without human settlements and maritime traffic. In addition, highly distinct hydroid assemblages were found characterizing both areas with water of Mediterranean origin and areas with water from Black Sea origin. Based on our results, we discuss the potential for the use of these organisms as indicators of water masses and anthropogenic impact at the regional level

Collapse of zooplankton stocks during Liriope tetraphylla (Hydromedusa) blooms and dense mucilaginous aggregations in a thermohaline stratified basin

A growing number of studies report an increase in jellyfish populations worldwide that may have consequences for marine planktonic food web dynamics. The principal objective of this study was to understand the changes in a zooplankton community during blooms of Liriope tetraphylla and subsequent mucilage events in the Sea of Marmara, a small highly stratified transitional basin between the Black and Aegean Seas. Liriope blooms observed in 2006 and 2007 reached a maximum abundance of 2978 ind.m(-3), following the species' first observation in 2005. Jellyfish species are known to play a key guild role by restructuring plankton communities and in the Sea of Marmara Liriope caused a temporal regime shift from a crustacean- to a jellyfish-controlled system. A rapid decline in abundance of most important zooplankton species followed the Liriope increase, together with a drastic shift in community structure. The dominant summer-autumn species Penilia avirostris (Cladocera) vanished in the autumn of 2006 and was diminished similar to 30-fold in 2007 when compared with years without Liriope. The decline in zooplankton and the devastating effects of mucilage on pelagic ecosystem and socio-economics through restricting commercial fisheries implied sensitivity of the already perturbed Marmara ecosystem to changes in predator densities and environmental stability