Climate change and agricultural pollution effects on the trophic status of a Mediterranean lake

Abstract

Trichonis Lake is the largest natural freshwater body in Greece with a surface area of 97 km2. It receives pollutants from numerous anthropogenic activities, especially from intensive agricultural practices, urban sewages, stock grazing land and small industries. In this study, hydrologic and chemical parameters are assessed during two periods (1990–1991) and (2001–2002) to evaluate the effects of the climatic changes on phosphorous trends and consequently on the trophic status of Trichonis Lake. Even though large quantities of fertilizers are applied in the lake's catchment, phosphorus loads are still in the permissible level as estimated according to Vollenweider's relationship based on total phosphorus concentration. Due to relatively higher rainfall precipitation during the last years, an increased amount of the phosphorus entering into the lake system is flushed out, thus keeping the trophic status of the lake in oligotrophic levels. In contrast, lower rainfall rates during the first period (1990–1991) have led to the decrease in phosphorus flush out and its detainment into the lake water and sediment resulting to mesotrophic conditions. As the trophic status of the lake is mainly hydrologically dependent and thus unpredictable, effective management plans targeting the elimination of nutrient pollution loadings are necessary.

Potential impacts of global climate change on freshwater fisheries

“…The natural trophic state of an aquatic system is a function of volume, water residence time, and nutrient input from the surrounding watershed (Kalff 2000). However, human activity can also alter the trophic status of aquatic systems through anthropogenic enrichment or nutrient depletion (Klapper 1991), and climate change (Mulholland et al 1997;Bertahas et al 2006). Most cases of eutrophication result from the input of excess nutrients from urban and agricultural runoff and from sewage discharge (Lammens 1990;Klapper 1991;Karabin et al 1997;Nicholls 1998).…”

“…Although the complex relationship between climate change and eutrophication makes prediction difficult, increased temperatures will likely result in a general increase in lake trophic status (Allan et al 2005). Lower stream flows could increase water residence times and reduce flushing of nutrients from lake systems, thereby increasing trophic status (Bertahas et al 2006). When coupled with the input of anthropogenic pollutants, climate change can accelerate the eutrophication process (Klapper 1991;Adrian et al 1995) or delay recovery from anthropogenic eutrophication (Nicholls 1998;Jankowski et al 2006).…”

Impacts of climate and land-use changes on the migration of non-point source nitrogen and phosphorus during rainfall-runoff in the Jialing River Watershed, China

“…In addition, agricultural activities are considered as a major provider of nutrients in water bodies, especially in the Jialing River Watershed, where agricultural sector comprises an important economic factor. Simultaneously, intensive farming practices can increase nutrient fluxes to freshwater and their roles to eutrophication (Bertahas et al, 2006;Shen et al, 2011), while nitrogen and phosphorus have been recognized as principal pollutants in rivers and lakes (Carpenter et al, 1998). Therefore, the change percentages of rural residential area during the future period are also estimated according to the population growth rate and the livestock and poultry growth rate, and then the results are shown in Table 2.…”

Local endemic and threatened freshwater hydrobiids of Western Greece: elucidation of anatomy and new records

“…There is a distinct interaction between pollutants and trematode parasitism in freshwater gastropods; pollution can modulate levels of parasitic infections by suppressing host immunity (hoCK & PoulIn 2012). Lake Trichonis receives pollutants from various sources, especially from intensive agricultural practices, urban sewage, stock grazing and small industries (BeRtahas et al 2006).…”

“…Being mainly hydrology-dependent, the trophic status of Trichonis is unpredictable. Consequently, effective management targeting both elimination of nutrient pollution loads and controlled water extraction is necessary (alBReCht et al 2006, BeRtahas et al 2006) in order to protect the lake's biodiversity.…”