MCCLOSKEY, K/L*; NESTLER, J/R; Walla Walla College; Walla Walla College: DIEL CYCLES OF ACTIVITY, METABOLISM, AND NUTRIENT EXCRETION IN THE TEMPERATE SEA CUCUMBER PARASTICHOPUS CALIFORNICUS

Sea cucumbers (Holothuroidea) influence ocean communities by affecting physical and chemical characteristics of water and sediment through their deposit feeding and excretion activities. Diel cycles of in situ movement, metabolism, and concentrations of ammonium and phosphate excretion were examined in Parastichopus californicus, a temperate sea cucumber inhabiting the coastal waters of the north Pacific. Data were collected during day and night (June-August 2005) at depths of 5-20 m using scuba. Oxygen consumption by P. californicus was higher at night (0.0161 mgO₂/g/h) than during the day (0.0265 mgO₂/g/h; P <0.001), as were phosphate concentrations from fecal material (2.850 µmolar and 3.792 µmolar, respectively; P <0.05). Concentration of animal ammonium excretion did not differ between day and night (P = 0.997). Concentrations of both ammonium and phosphate from cucumbers, however, were higher than for their corresponding backgrounds for both day (P <0.05) and night (P <0.001). No difference in cucumber movement was observed for P. californicus individuals during day (27.1 cm/h) and night (25.5 cm/h; P = 0.450). These data suggest that some physiological process of P. californicus may occur over a diel cycle, while others do not. Further research is needed to examine the presence of seasonal cycles of activity, metabolism, and nutrient excretion in P. californicus.