Yıldırım Fidanoğlu, P.; Cebe, K., and Balas, L., 2024. Exploring coastal ecosystem biodiversity in a Mediterranean hotspot: Marmaris Bay, Türkiye. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 896-900. Charlotte (North Carolina), ISSN 0749-0208.

The health of coastal ecosystems is intricately tied to water quality, making it imperative to understand the impact of anthropogenic and climate change factors on the maintenance and biodiversity of these environments. This study focused on Yalancı Boğaz, Marmaris (36° 48′ 35″ N-28° 18′ 52″E) along Turkey's western Mediterranean coast. The study meticulously explores a spectrum of parameters encompassing water quality, phytoplankton, zooplankton communities, seagrasses, fish species, sponges, and other marine organisms. The seasonal changes in the average seawater salinity and temperature in the Bay have been analyzed over the last 37 years. The investigations involved water temperature, salinity, pH, Dissolved Oxygen (DO), and turbidity measurements. Secchi disk depth was measured, and the suspended solid amount was determined. Additionally, plankton samples were collected, and scuba divers conducted underwater observations to assess the diversity of marine life. Phytoplankton and zooplankton species were identified using microscopic examination, revealing 19 phytoplankton species and 11 zooplankton species, and their average densities were identified. The planktonic diatom genus Bacteriastrum, ubiquitous in tropical and temperate marine environments, was dominant. Bacteriastrum was commonly observed in conjunction with the diatom Chaetoceros. A limited number of individuals belonging to the dinoflagellate class were found. Copepods, nauplii, and a small amount of rotifer and gastropod larvae dominated zooplankton species. The study extended to seagrass meadows, specifically Posidonia oceanica meadows, where morphometric descriptors such as leaf lengths, leaf widths, and the number of leaves per shoot were examined. Dentex dentex is listed in the International Union for Conservation of Nature's Red List as vulnerable and Epinephelus costae as data deficient among the nine fish species identified in the study area. The invasive species were the silver-cheeked toadfish (Lagocephalus sceleratus) and Lionfish (Pterois volitans). Laboratory analyses also revealed the presence of sponge species, tube wolf species (Vermetus triquetrus sp, Pinna nobilis sp., Lobatus costatus sp.), tube anemone (Cerianthus membranaceus sp.), and various Echinodermata (Phylum). In summary, the findings of this study underscore the stressors imposed by anthropogenic activities and climate change on the Marmaris coastal waters.