Response of food organisms to inorganic nitrogen availability

Abstract

Influence of inorganic N₂ forms on pond food organisms was investigated. Seven identified plankton taxa comprising four phytoplankton: Desmidiaceae (desmids), Bacillariophyceae (diatoms), Cyanophyceae (blue-green algae) and Chlorophyceae (green algae) and three zooplankton: Protozoa, Cladocera and Rotifera fluctuated in response to nutrient inputs. All recorded significant F-value across treatments. With exception of blue-green algae, other phytoplankton groups had comparable relative abundances in treatment with higher concentration of readily utilized Nitrate-Nitrogen (NO₃-N) compared with control that recorded higher concentration of Ammonia-Nitrogen (NH₃-N) and increased relative abundance of blue-green algae. Zooplankton exhibited same dominance pattern of Protozoa, Rotifera and Cladocera respectively, with treatment recording higher abundance in response to edible phytoplankton. N₂ from zooplankton excretion influenced phytoplankton responses in the control. Ammonia-Nitrogen (NH₃--N), Nitrate-Nitrogen (NO₃-N) and Nitrite-Nitrogen (NO₂-N) were observed to fluctuate along nutrient enrichment profile depending mostly on the concentrations of intermediate Nitrite-Nitrogen (NO₂-N). All nutrient parameters except NH₃-N recorded significant t and F statistic between and across treatments. Water quality parameter of pH and dissolved oxygen were favourable for most period of the experiment.


KEY WORDS: Nutrient, Plankton, Ammonia-Nitrogen, Nitrate-Nitrogen, Nitrite-Nitrogen.


Global Jnl Pure & Applied Sciences Vol.10(2) 2004: 243-248