Aerobic and anaerobic metabolism of Paraprionospio pinnata (Polychaeta: Spionidae) in central Chile

The aerobic and anaerobic metabolism of Paraprionospio pinnata were estimated under laboratory conditions. Paraprionospio pinnata is a widely distributed, often dominant polychaete inhabiting sublittoral sediments on the continental shelf off central Chile, where there is a pronounced oxygen minimum zone (OMZ). The aerobic respiration rates ranged from 0.25 to 1.28 ml O ₂ h^-1 g^-1 dry weight. Paraprionospio pinnata displayed oxyconformity between 30 mm Hg (4 kPa) and 104 mm Hg (14 kPa) of oxygen tension levels (pO₂) under laboratory conditions. We found that P. pinnata is an aerobic oxygen conformer and is able to endure very low oxygen conditions. High anaerobic activity of alanopine dehydrogenase (5.74 ±1.20 μmol NADH min^-1 g^-1 wet weight) and strombine dehydrogenase (8.82 ±4.04 μmol NADH min^-1 g ^-1 wet weight) were observed. The ratio between the calculated aerobic respiration rates and the electron transfer system activity were 0.28 and 0.12 for normoxic and hypoxic conditions, respectively. Based on the observed respiration rates and the average densities of P. pinnata in the study site, we estimated the population carbon flux via aerobic respiration to be about 32 mg C m^-2 d^-1 in spring and 80 mg C m^-2 d^-1 in winter. Paraprionospio pinnata would be using, then, about 8.6% of the total downward flux of organic carbon to the seabed and contributing between 18 and 44% of the total sediment community oxygen consumption.