Rates of oxygen consumption (R) and ammonia excretion (E) of a total of 22 species of zooplankton and
hyperbenthos, which weighed 0.0012 to 26.7mg dry mass (DM), from inshore and slope waters of the Great Barrier
Reef were determined at in situ temperatures (23 to 30°C). Rs ranged from 0.0048 to 118.3μL O2 ind.
-1 h-1 and Es
from 0.00051 to 15.9 μg NH4-N ind.
-1 h-1
. Stepwise regression analyses in which the differences in body mass are
taken into account revealed that zooplankton and hyperbenthos exhibited comparable R, but the latter showed lower
E than the former. As a result, the atomic ratio of R to E (O:N) of hyperbenthos (geometric mean: 53.1) was greater
than that (16.4) of zooplankton. No appreciable differences were evident in C and N composition of the bodies between
zooplankton-hyperbenthos; total carbon (C) ranged from 18.0 to 47.2% of DM and total nitrogen (N) from 2.4
to 12.7% of DM, with C:N ratios of 3.1–7.5. Judging from C and N composition, protein was the major component of
body organic matter of both zooplankton and hyperbenthos. In terms of N-specific R and N, the present zooplankton
data are comparable to those published on tropical zooplankton and small fishes with similar body N. Compared with
zooplankton, lower specific Es and higher O:N ratios of hyperbenthos were interpreted to reflect their partial or entire
dependence on diets characterized by lower N composition (detritus).