Effect of temperature on carbon, nitrogen and phosphorus turnover by the solitary ascidian Herdmania momus (Savigny)

Abstract

Abstract The relationship between the C to N to P composition ratio (C:N:P) of three diets and metabolic C:N:P turnover of a solitary ascidian, Herdmania momus (Savigny), was examined after a retention period of 89 days in two temperature regimes. The three diets (particles derived from fresh kelp, aged kelp particles, and phytoplankton) caused significant variation in respiration rates, C and P content of faeces and N stored in tissues. Temperature regime ( ambient= 16.6−19.5°C; heated= 21°C) caused significant variation in phosphate excretion rate, N content of faeces and internal organs, the RQ, and P stored in tissues. There was no interaction between diet and temperature. The individuals which were retained in heated water had significantly higher N turnover with increased temperature was substantiated by a preliminary comparison of metabolic characteristics of H. momus from two latitudes on the Western Australian coast. Environmental temperature can change the turnover of N with respect to P, and thus the relative requirements for these two elements by this marine heterotroph. The metabolic demands for N and P by H. momus are predicted to vary with local climate, with a lower N and higher P demand as latitude increases.