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Titolo:
Interactions between sediment-feeders and microalgae on coral reefs: grazing losses versus production enhancement
Autore:
Uthicke, S;
Indirizzi:
Inst Hydrobiol & Fischereiwissensch, D-22959 Hamburg, Germany Inst Hydrobiol & Fischereiwissensch Hamburg Germany D-22959 urg, Germany
Titolo Testata:
MARINE ECOLOGY-PROGRESS SERIES
, volume: 210, anno: 2001,
pagine: 125 - 138
SICI:
0171-8630(2001)210:<125:IBSAMO>2.0.ZU;2-6
Fonte:
ISI
Lingua:
ENG
Soggetto:
GREAT-BARRIER-REEF; STICHOPUS-CHLORONOTUS; LIMITED PRODUCTIVITY; COMMUNITY STRUCTURE; HYDROBIA-TOTTENI; MARINE-SEDIMENTS; ALGAL COMMUNITY; ORGANIC-MATTER; NITROGEN; GROWTH;
Keywords:
productivity; sediment-feeders; microalgae; holothurians; grazing; recycling; close coupling;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Agriculture,Biology & Environmental Sciences
Citazioni:
75
Recensione:
Indirizzi per estratti:
Indirizzo: Uthicke, S Australian Inst Marine Sci, PMB 3, Townsville, Qld 4810, Australia Australian Inst Marine Sci PMB 3 Townsville Qld Australia 4810
Citazione:
S. Uthicke, "Interactions between sediment-feeders and microalgae on coral reefs: grazing losses versus production enhancement", MAR ECOL-PR, 210, 2001, pp. 125-138

Abstract

The close coupling between producers and consumers of inorganic nutrients is generally assumed to be important to maintaining high productivity on coral reefs. I examined whether a tight cycling of nutrients exists between benthic microalgae and sediment-feeding holothurians (Stichopus chloronotus and Holothuria atra). Benthic microalgae had an increased production (measured as O-2 evolution) after exposure for more than 3 h to effluent water from tanks containing holothurians. Direct addition of phosphate and ammoniumsuggested that this increase was mainly caused by the excretion of ammonium. In experiments in which a part of the sediment area was inaccessible to the holothurians, microalgae production significantly increased in aquaria containing holothurians, irrespective of whether microalgae were grazed or protected from grazing. Thus, it could be inferred that production enhancement is solely a nutrient effect and not due to other effects described for other grazers (e.g. removal of senescent cells or reduction of self-shading). The effects on the microalgal biomass (measured as chlorophyll a and phaeophytin) depended on the actual grazing intensity. When a high grazing pressure was simulated (e.g. 2 H. atra on 0.116 m(2)), microalgal biomass was reduced significantly after 7 d compared to control aquaria. At lower grazing intensities (e.g. 1 S. chloronotus on 0.232 m(2)), the microalgal biomass increased significantly. A significant negative correlation was found between the amount of sediment consumed in each single aquarium (measured as the weight of the faeces produced) and the increase in chlorophyll a and phaeophytin concentrations in the sediment. A comparison with in situ sediment-consumption rates suggested that holothurians in natural densities have anoverall beneficial effect on the benthic microalgal community. I propose that holothurians and other sediment-feeders are important components of a benthic recycling system that may have some similarity to the planktonic microbial loop.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 04/12/20 alle ore 08:30:14