Excretory products of mobile epifauna as a nitrogen source for seaweeds

Abstract

The potential for excretory product of mobile epifauna to be source of nitrogen for seaweeds was investegated for the fucalean alga Carpophyllum plumosum var. capillifolium at Matheson Bay, northeastern New Zealand.The epifauna excreted an average of 1.5–2.1 times as much nitrogen as the plants were using. A comparison of rates at which the plants took up ammonium with turnover rates of water in the bed indicated that the plants could derive, on average, up to 79% of the nitrogen they required for growth from ammonium excreted by epifauna. This value was estimated under the assumption that ammonium excreted was instantaneously diluted into the water mass surrounding the entire bed. In nature, the availability of ammonium to the individual host seaweed should be greater owing to hydrological processes that restrict water flow around the plant.