Nutrient recycling - a strategy of a grazer community to overcome nutrient limitation

We examined in situ the fate of N in the epilithon and a grazer community in the N-limited rocky littoral of Lake Erken, Sweden. The grazer community consisted of the sessile caddisfly larva Tinodes waeneri (L.) plus its gallery. The gallery consisted of a web that is spun by the larva plus the microorganisms (mostly algae) closely associated with the web. We applied N-15 in the field and recorded N-15 uptake and retention time. The galleries took up N-15 faster from the overlying water and retained N-15 1 wk longer than the surrounding epilithon. These results supported our hypothesis that effective N use through the Tinodes community by recycling may alleviate N limitation and enhance biomass production of the gallery algae.