Grazing On Benthic Primary Producers

The importance of herbivores as controls of nutrient storage as producer biomass depends to a great extent on the percentage of primary production they consume. This is so because the quantity of primary production that remains stored as producer biomass decreases as consumption by herbivores increases. Hence, herbivores may keep low levels of producer biomass through intense consumption (Carpenter 1986, Valentine & Heck 1991, Cebrian & Duarte 1994). Similarly, the contribution of herbivores to producer-bound nutrient recycling through faeces excretion and exudation also increases with the percentage of primary production consumed. Herbivore excreta are usually nutrient-rich in relation to producer detritus and thus are quickly decomposed by detritivorous organisms. Thus, large percentages of primary production consumed can significantly increase the rate of nutrient recycling in the system (Elser & Urabe 1999, Sterner & Elser 2002).