Oxygen consumption rates of fecal pellets produced by three coastal copepod species fed with a diatom Thalassiosira pseudonana

Fecal pellet production rate and oxygen consumption rate of copepod fecal pellets egested by Paracalanus sp., Acartia spinicauda and Centropages orsinii feeding on a diatom Thalassiosira pseudonana were measured. Fecal pellet production rates varied between 3.6 and 80.6 pellets ind⁻¹ d⁻¹ among three species, with fecal pellet production of Paracalanus sp. significantly higher than the other two copepod species. Average pellet size varied between 2.82 × 10⁵ μm³ for Paracalanus sp. and 5.36 × 10⁵ μm³ for A. spinicauda. Average volumetric oxygen consumption rates were 27.32, 5.84 and 45 fmol O₂ μm⁻³ d⁻¹ for fecal pellets produced by Paracalanus sp., A. spinicauda and C. orsinii, respectively. The potential oxygen consumption of fecal pellets egested from Paracalanus sp. was the highest due to its high fecal pellet production rate and high population abundance throughout the year. Overall, the approximate in situ oxygen consumption due to copepod fecal pellet degradation was significant in estuarine and coastal waters of Hong Kong. Results of this study give insight of the role of zooplankton in potential occurrence of hypoxia in coastal waters during summer.