MEPS 257:13-23 (2003)  -  doi:10.3354/meps257013

Particle removal by coral reef communities: picoplankton is a major source of nitrogen

M. Ribes1,3,*, R. Coma2, M. J. Atkinson1, R. A. Kinzie III1

1Hawaii Institute of Marine Biology, University of Hawaii, PO Box 1346, Coconut Island, Kaneohe 96744, Hawaii, USA
2Centre d¹Estudis Avançats de Blanes (CEAB-CSIC), Accés Cala Sant Francesc 14, PO Box 118, 17300 Blanes, Girona, Spain
3Present address: Institut de Ciències del Mar (CMIMA-CSIC), Pg. Marítim 37-49, 08003 Barcelona, Spain

ABSTRACT: Removal and uptake of planktonic particulate organic matter by coral reef benthos is widely recognized as an important pathway for carbon and nutrients. We placed 3 natural assemblages of coral reef benthos, including 3 species of corals with associated sponges, ascidians, actinians, and bryozoans, in a long flume (24 x 0.4 x 0.3 m). Water was re-circulated at various speeds (5, 13, 22, and 32 cm s-1) over 6 h, and the disappearance of particles (pico-, nano-, microplankton and detrital particles) were measured using flow cytometry and microscopy. Control communities consisted of dead coral skeletons. Rates of removal of all particles were proportional to their concentrations. The first-order rate constant for the decrease in particle concentration ranged from 36 to 97 x 10-6 m s-1 (mean ± SD = 63 ± 16 x 10-6 m s-1), with 71% of this variation explained by particle type. Water velocity had no significant effect on these rate constants. Living particles contributed 96% of the total nitrogen removal, with picoplankton (cells 0.2 to 2 µm) accounting for 92%. Overall, nitrogen removal from particles (8.8 to 10.3 mmol N m-2 d-1) appears to be similar in magnitude to that of dissolved inorganic nitrogen; thus, picoplankton is a major source of nitrogen for these coral reef assemblages.

KEY WORDS: Benthos · Coral reef communities · Nutrients · Particle removal

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