TRACKING THE MAIN WATER QUALITY THREATS IN LAKE PRESPA SYSTEM (GREEK PART)

Maliaka Valentini, Wageningen University, The Netherlands

Abstract

The present study is taking place in the region of Lake Prespa which is shared among Greece, Albania & FYR of Macedonia and it is internationally recognized as a ‘shelter’ for endemic biodiversity and migratory birds. The conservation of their habitats dictates among others the evaluation of the potential threats which may pose a risk for the aquatic system and originate primarily by anthropogenic influence.
The Greek part of Lake Prespa has been chosen to be investigated: it includes the shallow lake Micro Prespa (47 km2) and the deep lake Macro Prespa (253.6 km2) which are inter-connected through an artificial canal. The purpose of the study is to detect the potential water quality deterioration in both lakes and its sources. The focus is on the major nutrient, sulfate and metal ions in order to evaluate the eutrophication occurrence and other aspects of water pollution.
An extensive preliminary sampling scheme during March 2012 includes the assortment of 24 in-lake samples and 15 watershed-samples. The last one refers to critical surface inflows, adjusted wetlands and cultivated fields since long distance transfer and dispersion mechanisms of pollutants are under consideration. The parameters measured originate from the sediments, pore water, surface and hypolimnetic lake waters. Taking into account the biogeochemical processes within a lake system and the prevailed environmental conditions, the abundance of a series of elements in these media are setting a comprehensive outline for the evaluation of the eutrophication insights in the study lakes. Internal phosphorus loading from sediments -which may trigger rapid algae growth- is reflected on pore-water phosphate concentrations, phosphorus pool in sediments, Fe:P and Fe:S ratio while soil density and phosphorus status indicate external increased nutrient leaching from surface or underground inflows. Additional cyanotoxin analysis (microcystins) will reveal the prospective co-occurrence of harmful cyanobacteria species during warm periods and their toxicity levels. Since the implementation of a representative water-quality monitoring network is among the priorities of the lake management of Prespa area nowadays, the current study is providing an up-to dated streamline of information for the factors that may trigger a risk for this valuable aquatic ecosystem and the sites which indicate the highest risk.

Keywords: Lake Prespa, eutrophication, phosphorus internal loading, biochemical processes, metals, cyanotoxins