Saronikos Gulf S11 Aegean Sea Latitude:   37.8726     Longitude:   23.6383 Associated Investigators: Soultana Zervoudaki , Georgia Asimakopoulou (chlorophyll) ,   Epaminondas Christou ,   Ioanna Siokou-Frangou   Saronikos Station 11 (Saronikos S11) is located in the Saronikos Gulf at 37 52.36'N 23 38.30'E, with a bottom depth of 78 m. Zooplankton were sampled with a WP-2 net (56 cm diameter, 200 µm mesh) from a depth of 75 m to the surface. Monitoring of zooplankton and abiotic parameters started in 1987, with variable (monthly or seasonal) sampling frequency and periodic gaps. Zooplankton biomass (total dry mass) was highest during the well-mixed winter period, with maxima in April, followed by a general decline accompanying increasing water temperatures and stratification. Saronikos S11 surface temperature peaks in August and has a minimum in February-March. Salinity ranges between 38 and 39 psu, depending on the variable inflow of Aegean water (Kontoyiannis et al., 2005). Saronkis S11 is located 7 km from the Athens domestic sewage outfall. Prior to 1994, untreated wastewater was disposed at the sea surface. In 2004, primary-treated wastewater was disposed at a depth of 60 m, below the seasonal thermocline. Since 2004, this wastewater has been further treated in order to eliminate its organic load and to greatly reduce its nutrient content. In spite of additional treatment, nutrient concentrations increased during the period 1987-2004, related to an increase in sewage volume. During this period, phytoplankton biomass decreased until 2002, probably because of the availability of nutrients at depth after 1994 and the competition with bacteria (Siokou-Frangou et al., 2007; Zeri et al., 2009). In contrast, zooplankton biomass revealed a clear increasing trend from 1987 to 2003, followed by a slight decrease. Despite an apparent covariability of seawater temperature and zooplankton biomass anomalies, no correlation was found between climate indices and zooplankton groups (Berline et al., In press). Nevertheless, investigation at the species level could provide more information for the study area. The combination of several driving forces affecting the area and the lack of data makes the investigation of zooplankton variability quite difficult. Continuation of the monitoring without gaps and greater stability obtained in anthropogenic factors could permit a better understanding of zooplankton dynamics in future.