Oxygen consumption and ammonium excretion of mega-sized benthic invertebrates in a tropical seagrass bed

Abstract

In a Papua New Guinean seagrass bed community, oxygen consumption rates and ammonium excretion rates of various size classes of six dominant species of megafauna, Tripneustes gratilla (Linnaeus), Axius acanthus A. Milne-Edwards, Conomurex luchuanus (Linnaeus), Malleus malleus (Linnaeus), Holothuria atra Jaeger and H. scabra Jaeger, were measured using a differential gas-volumeter method and an oxygen bottle method. The metabolism/weight exponent “b” (R = aWb) for the six species ranged from 0.11 to 0.64 and was thus lower than the general value of “b” in poikilotherms. O/N ratios for the six species ranged from 19.3 to 44.2. The O/N values were discussed in relation to the various species' feeding habits. The abundance and size-frequency distributions of six species were estimated. Oxygen consumption and ammonium excretion rates could thus be calculated for the populations of the six species from metabolism/ weight relationships and the abundance and size-frequency distribution data. The total energy demand for respiration of the six megafaunal species in the seagrass bed of 6.56 ha was 12285 kcal·day−1. The importance of the megafauna to overall energy budgets for tropical seagrass bed communities was emphasized.