Physical and Chemical Characteristics of a Mediterranean Coastal Microenvironment: The "Salty Lake" of Aghios Nikolaos (Crete, Greece)

The present paper examines a small and deep (53 m) salty lake, as well as the adjacent harbor of Aghios
Nikolaos (Crete). The survey was carried out in 1996. Physicochemical parameters indicated that the
main characteristics of the system are the inflow of karstic water from underwater springs inside the
lake and the permanent anoxic conditions prevailing in its deeper part, below the thermocline. Nutrient
concentrations are very high throughout the water column of the lake. Ammonia is the main source of
nitrogen in the summer, particularly below the thermocline, whereas nitrates have high concentrations
during spring and autumn. The high levels of these nutrients in the adjacent to the lake harbor and
coastal waters indicate clearly the impact of the lake to the marine ecosystem. Anthropogenic pollutants,
such as aromatic hydrocarbons, show high concentrations above thermocline, at 5-10 m depths
during all samplings. However no particular point source was identified. The presence of hydrocarbons
contributes to ineffective oxygenation of the lake waters and facilitates the development of anoxia and
the production of ammonia. The PAH concentrations at the sampling stations outside the lake are typical
of marine environments, with relatively small oil-derived inputs, indicating the complex role of the
system as a source and/or as a trap of PAHs.