SPATIAL AND TEMPORAL TRENDS OF WATER QUALITY AT SARANDA BAY, ALBANIA

摘要

Differences in space and time of important physical, chemical and biological parameters were examined in the Saranda Bay, Ionian Sea. The samples were taken fourrntimes each year during 2007 and 2008 at seven sampling stations. Values of nutrients vary during seasons and sampling points. Values of total mineral N (N-NH_4~+, NO_3~- and NO_2 included) were on average similar to those found in other Mediterranean coastal countries, except sampling station 6 in August (430.5 mmol m~(-3)). The orthophosphate (PO4~(-3)) concentrations were high especially at stations 3, 4 and 6. During August, PO_4~(-3) reached ≥ 20 mmol m~(-3) at stations 3, 4 and 6, and decreased <15 mmol m~(-3) at the remaining stations during the same period. In Saranda Bay the atomic ratio N:P was generally lower than 16, making N the limiting factor. The same ratio values were higher than 20 at stations 2, 3 and 7 especially during the hot season, making P the limiting nutrient. The average value for chlorophyll a is comparable with oligotrophic water systems. Those values were significantly higher in May (0.59 μgL~(-1)) as compared to November (0.34 μgL~(-1)), August (0.32 μgL~(-1)), and March (0.48 μgL~(-1)). Heavy metals were on average present in lower levels (Pb <5.5 μgL~(-1), Cr <1.8 μgL~(-1)) or similar levels (Cu <23 μgL~(-1) and Cd <3.5 μgL~(-1)) when compared with values found in other coastal countries. Statistical results (PCA) indicate that temperature, pH and nutrients (especially N) affected other variables. Correlative links also indicate influence in water quality by wastewater and agricultural activity in the watershed of the Bistrica River. Results of this study indicate that the environmental qualities of the Saranda Bay remain of an oligotrophic nature, despite the current pressure from contaminants.