Natural dimictic and polymictic lakes: Similarities and differences in relationships among chlorophyll, nutrients, Secchi depth, and aquatic macrophytes

Abstract

Fourteen lakes, situated in the Borecka Forest, Poland and including 8 dimictic and 6 polymictic lakes, were investigated over a period of 10 years. The water bodies were at low risk from eutrophication. A positive and statistically significant correlation between total phosphorus (TP) and total nitrogen (TN) concentrations and chlorophyll levels was reported in all of the studied lakes. The results of the study validate the hypothesis that aquatic vegetation in lakes may have a delayed response to nutrient supply because the phosphorus delivered to and present in lakes may be partially unavailable for producers. Redundancy analysis (RDA) results revealed a significant correlation between relative plant abundance and chlorophyll concentrations and a weaker relationship with the remaining lake parameters (TP, Secchi depth, TN). The positive correlation between chlorophyll and seston concentrations was significant only in dimictic lakes (r = 0.62, p = 0.001). In polymictic water bodies, chlorophyll levels decreased with Secchi depth, whereas chlorophyll concentrations in dimictic lakes varied irregularly with an increase in water transparency. The correlation between seston and Secchi depth was significant in all lakes. Seston distribution in response to a drop in water transparency did not differ significantly between the lake types. The analyzed parameters supported the identification of two groups of lakes which correspond to habitat types of the Natura 2000 network. © 2013 © 2013 Taylor & Francis.