Effects of Nutrient Limitations and Watershed Inputs on Community Respiration in a Deep, Tropical Lake: Comparison of Pelagic and Littoral Habitats

Abstract

AbstractCommunity respiration and nutrient limitation are frequently studied in pelagic habitats; however, comparisons of these processes between littoral and pelagic habitats are less common and do not exist from mountain lake ecosystems in the tropics. Community respiration was measured in the littoral benthic and pelagic habitats of a deep, endorheic mountain lake in Guatemala. Community respiration rates were quantified using biochemical oxygen demand within a temperature controlled, dark, laboratory incubation. Community respiration was measured in the pelagic habitat in response to inorganic nitrogen, phosphorus, nitrogen and phosphorus, glucose, five different soils, and sewage additions and in the littoral habitat in response to inorganic nitrogen, phosphorus, nitrogen and phosphorus, and sewage additions. During all periods, community respiration was higher and more variable in the littoral habitat than in the pelagic habitat. The additions of nitrogen, phosphorus, and nitrogen and phosphorus had no effect on community respiration, in either habitat. Glucose and four of the five soil additions from various watershed vegetation types significantly stimulated community respiration in the pelagic habitat. Sewage additions elicited the highest response in both pelagic and littoral habitats. We demonstrate that community respiration in a tropical montane lake is not limited by inorganic nitrogen or phosphorus and is not colimited by both nutrients combined. Treatments containing organic carbon and organic nutrients were significant stimulators of community respiration; therefore, organic carbon is likely limiting community respiration in Lake Atitlán.