Feeding behavior of Tigriopus californicus fed urchin feces vs fresh algae

Abstract

Primary productivity does not occur in deeper waters due to limiting light availability, and thus deep subtidal organisms receive energy in the form of detritus. Urchins in the San Juan Archipelago catch and consume large quantities of kelp detritus, and due to inefficient digestive systems their feces have high caloric value and are readily available to benthic organisms. The nutritional value of fresh Nereocystis luetkeana and Saccharina latissima were compared to that of feces from urchins fed the same algal species in a set of population growth and dietary preference experiments using the copepod species Tigriopus californicus. Population growth rates were not recorded due to massive mortalities; however, significant copepod preference for urchin feces over both algal species was observed. This suggests urchins may provide a substantial link between shallow habitats of high algal productivity and deeper subtidal environments of low productivity by providing detritus in the form of high nutrient fecal matter.