Interactions between sediment-feeders and microalgae on coral reefs: grazing losses versus production enhancement

Abstract

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 an overall 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.KEY WORDS: Productivity · Sediment-feeders · Microalgae · Holothurians · Grazing · Recycling · Close coupling Resale or republication not permitted without written consent of the publisher

Restricted gene flow between Holothuria scabra (Echinodermata: Holothuroidea) populations along the north-east coast of Australia and the Solomon Islands

“…The latter finding is consistent with the view that juveniles settle in shallow seagrass beds and then migrate to deeper areas during their life span (Vail 1989, James et al 1994. Although their function in seagrass ecosystems has not been studied, holothurians have important functions in bioturbation and nutrient recycling in coral reef ecosystems (Uthicke 1999(Uthicke , 2001). Therefore, one may assume that apart from direct effects of fishing on population densities, a reduction in holothurian densities will have secondary ecological effects.…”

Photosynthetic efficiency and rapid light curves of sediment-biofilms along a water quality gradient in the Great Barrier Reef, Australia

“…This assumption was based on a variety of experimental studies that all found distinct productivity enhancement of tropical marine microphytobenthos under nutrient (especially N) addition. Uthicke & Klumpp (1997 and Uthicke (2001) demonstrated production enhancement in situ and in aquaria within 12 h, and biomass enhancement after several days of ammonium enhancement (either added directly or as an excretion product from benthic invertebrates) of only 1 to 2 µM above background level. Similarly, several other studies (Dizon & Yap 2003, Heil et al 2004, Gottschalk 2005) demonstrated rapid production enhancement or biomass increases of coral reef microphytobenthos upon N addition, for both inshore sediments similar in carbonate content to the inner zones investigated here and also for sediments with carbonate content as high as on midshelf reefs.…”

“…However, the use of these communities as indicators for changing water quality on coral reefs has not been investigated, despite fulfilling several important pre-requisites as ideal indicators: (1) these communities are ubiquitous and easily accessible, because up to 40% of individual reefs can be sediment covered and is therefore suitable habitat (Uthicke & Klumpp 1998); (2) several studies have indicated that these communities are N-limited and respond rapidly to increased nutrient levels with increases in biomass and production (Uthicke & Klumpp 1998, Uthicke 2001, Dizon & Yap 2003; (3) microphytobenthos also rapidly responds to changes in light condition with adaptations in photo-physiology (Uthicke & Klumpp 1998).…”

Feeding regime of sea cucumber Stichopus herrmanni on coral reefs of southeast of the Qeshm Island, Persian Gulf

“…In addition, the absorption coefficient is calculated at 46.9% for consumed diatoms (Yingst, 1976). Also in other studies of benthic microalgae mentioned that microalgae as food for this animals witch they are so important for nutrients recycling in coral reefs habitats (Uthicke, 2001).…”