A long-term study on Coolia monotis distribution from the south-east Mediterranean Sea

摘要

The potentially toxic species Coolia monotis is widespread along the Mediterranean coasts. The Gulf of Gabe`s is one of the affected areas in the south-eastern part of the Mediterranean Sea. Distribution patterns of C. monotis in relation to temperature and salinity were investigated at 24 monitoring sites along the Gulf of Gabe`s coasts during 22 years (1997-2018). The analysis of C. monotis occurrence in the water column revealed a seasonal trend with high abundances (>= 10(5) cells l(-1)) recorded during winter. C. monotis was widely distributed in Gabe`s Gulf, it was most abundant in the southern part, particularly at the Cotusal Channel site, which is surrounded by marine solar salterns, where the highest concentration (2.54 x 106 cells l(-1)), the maximum mean abundance (3.74 +/- 51.87 x 10(4) cells l(-1)) and the highest number of observations (75) were recorded over the study period. C. monotis was observed within a wide range of temperature (9-31.6 degrees C) and salinity (31-59) with high abun-dances (>10(5) cells l(-1)) occurring at water salinity and temperature of 41.9-45 and 15-17.3 degrees C, respectively. A positive correlation was found between the abundance of C. monotis and salinity (p < 0.05), whereas no correlation was found as regards temperature. Culture experiments were conducted under varying salinity regimes (10-50) with C. monotis strain (Com.10) isolated from the Cotusal Channel. Growth occurred at salinities between 20 and 50 and the maximum growth rate of 0.23 day1was recorded at a salinity of 40. Results suggest that seawater salinity plays a central role in the C. monotis blooms development.