GORGONIANS AS INDICATORS OF MASS MORTALITY: THE CASE OF Spinimuricea klavereni IN THE SEA OF MARMARA (TURKEY)
A recent event of mass mortality affected macrobenthic suspension feeders in Prince Islands (PI) coasts, the northeast Sea of Marmara (Fig. 1), in summer 2015. The mortality was mainly due to very high deposition of suspended particulate matter. In this region, Spinimuricea klavereni is one of the two most abundant gorgonians on substrates characterized by a mixture of pebbles, shells and small rocks on muddy bottom but also on rocky bottoms.
After the event, between August - November 2015, 9 stations in the south of PI coasts were monitored in order to assess the impact of the event. S. klavereni colonies were enumerated in 20 transects (1 m2) placed on either side of a 20-m-long transect tape laid on the substrate. The number of (i) healthy colonies, (ii) colonies showing more than 10 % tissue necrosis of its surface and (iii) completely dead colonies were noted. In case of tissue necrosis, the % of necrosis on colony surface as well as the presence of epibionts were also noted.
The % of dead and damaged colonies are much higher than those in previous years (Fig. 2) despite the numbers before mortality were also high, in comparison to values in other gorgonian populations in the Mediterranean Sea. Most of the damaged areas on colonies were covered by pioneer epibionts (mainly biofilm, algae and hydroids), showing that the necrosis were recent. S. klavereni is a species with higher growth rates than other gorgonians and is able to cover a large scale of bottom types in the Sea of Marmara. The recovery of the population in PI region will be monitored in following years. However due to slow dynamics of gorgonians and several stress sources in the natural environment, under captivity culture of the species and later, enhancement of the natural population is also considered. Previous studies showed that the species is able to survive in captivity conditions.