“Ornithological eutrophication” as a source of allochthonous nutrient enrichment in Anavilundawa reservoir, Sri Lanka

Abstract

Mass aggregation of waterfowls for breeding, results in allochthonous nutrient inputs intoaquatic systems. This study evaluated accumulation of bird droppings as allochthonusnutrient input and its fluctuations in Anavilundawa International Ramsar Sanctuary in SriLanka where Asian openbill (Anastomus oscitans) mass breeding occurs annually. Reservoirwas divided into four strata: Inlet, breeding ground, reservoir centre and outlet. The highestnutrients levels (NO3,PO43,NH4þ, alkalinity) and the lowest dissolved oxygen and pHlevels were recorded in breeding grounds for both surface and bottom water. The highestturbidity was recorded in inlet surface and centre bottom water. Canonical Variate Analysis ofwater quality parameters indicated the significantly distinct influence of ornithologicaleutrophication on surface water of four strata whilst, showing similarities in water quality ofbottom layers in inlet and outlet. In the breeding ground, surface water was covered with thickmats of aquatic flora consisting of Water hyacinth, Salvinia, duckweed and Polygonum.Therefore, it is concluded that in addition to dilution, amelioration of water quality could alsobe happening due to absorption by plants. Due to interactions between invasive plants andwaterfowls, restoration with native aquatic flora is needed to be considered to regain reservoirresilience and self-sustenance.