The Effects of Bird Droppings on Chemical and Biological Dynamics in Brackish Water Rockpools

In the Baltic, some brackish water rockpools, heavily polluted by bird droppings, were investigated in order to study some of the general patterns of biochemical cycling of the nutrients. The seasonal variations of the following parameters were studied: salinity, temperature, rainfall, pH, algal biomass, detrital content, NH4-N, N02-N, N03-N, P04-P, suspended and soluble organic nitrogen and phosphorus. The diurnal variations of pH, P04-P and oxygen were measured. The faunal composition is discussed. The bird feces provided nutrients well beyond the needs of the algal biomass throughout the vegetation period. High concentrations of phosphate were always found, and this resulted in extremely low N/P ratios reflecting the chemical composition of the bird feces. Ammonia was always the dominating inorganic nitrogen compound and only during the period of maximum algal growth in the spring were considerable amounts of nitrate found. A possible inhibition of the nitrification processes resulting in an accumulation of ammonia is discussed. The high concentrations of ammonia might have a toxic effect on the algae, especially at the prevailing high pH-values. Most of the algal biomass was decomposed in the beginning of July. The diurnal variation of inorganic phosphate was found to be very large even in the absence of algae. This is mainly attributed to the activity of both autotrophic and heterotrophic bacteria. The difficulties in relating these fluctuations to productivity measurements are discussed. The nutritive value of the detrital layer, which consists mostly of fecal pellets, is discussed. Pe3IoMe