The deep-sea meiofauna of the porcupine seabight and abyssal-plain (ne atlantic) - population-structure, distribution, standing stocks

The metazoan meiofauna has been studied in multiple corer samples collected in the \nPorcupine Seabight and on the Porcupine Abyssal Plain (NE Atlantic, 49.3°-52.3°N). \nCores were taken at 500 rn intervals between depths of 500 rn and 4 850 m. With \nincreasing depth the total meiofaunal abundance declined from 2 604 to 315 individuals \nper 10 cm-2 and the biomass from 1.16 to 0.35 mg per 10 cm- 2 (ash-free dry weight). \nThis depth-related decrease in standing stock was significantly correlated with the \namounts of sediment-bound chloroplastic pigments (chlorophyll a, pheopigments) in \na parallel set of samples. These pigments provide a measure to estimate the flux of \nprimary organic matter to the seafloor. The depth transect in the Porcupine Seabight \nis compared with similar transects off Portugal and north Morocco. AU three transects \nrevealed major decreases in meiofaunal density and biomass between 500 rn and \n1 500 rn, roughly equivalent to the archibenthic zone, and also between the continental \nrise and the abyssal plain. Between 2 000 rn and 4 000 rn, however, the standing stock \ndecreased only slightly. The metazoan meiofauna in the Porcupine Seabight samples \nconsisted mainly of nematodes (80.0-91.5%) with harpacticoids and nauplii generally \nsecond in abundance (3.3-6.8%). Between 500 rn and 2 000 rn, polychaetes and bivalves \ncontributed substantially to the meiofauna.