Trophic dynamics of a mud snail [ Ilyanassa obsoleta (Say)] population on an intertidal mudflat

Abstract

Carbon, nitrogen and phosphorus cycling and energy transfer by a field population of the mud snail, Ilyanassa obsoleta (Say), were measured throughout a year at Branford Harbor, Connecticut. The elements and energy returned by Ilyanassa to the mudflat system were 95% particulate organic matter (894 g C m−2 year−1+66 g N m−2 year−1 in mucus plus feces; 9541 kcal m−2 year−1) 4% dissolved organic matter (26 g DOC m−2 year−1+1.7g DON m−2 year−1+0.3g DOP m−2 year−1 in excretory products plus fecal DOM; 307 kcal m−2 year−1) and 1% dissolved inorganic matter (2.8g CO2−C m−2 year−1+8.13g NH4++NO4−−N m−2 year−1+1.9g PO43−−P m−2 year −1) for use by sympatric primary and secondary consumers. The gross trophic efficiencies clearly show that most of consumption was not assimilated and was defecated (UF: I was 0.63, 0.58, 0.91 and 0.62 for carbon, nitrogen, phosphorus and energy, respectively). Mucus production (fecal envelope and trail) was estimated to be 80% of total assimilation (Pm:A) for carbon, nitrogen and energy, while estimated tissue production (somatic, reproductive and shell periostracum) was 2–3% for each element and for energy. The net respiration efficiency (R: I) was 16% for carbon and for energy assimilation. The net excretion efficiency (Ex: A) was 1% for carbon, 2% for energy, 23% for nitrogen and 98% for phosphorus.