Why is bacterioplankton growth in coral reef framework cavities enhanced?

Sr Scheffers,Fc Van Duyl,Rpm Bak

doi:10.3354/meps299089

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 299:89-99 (2005) - doi:10.3354/meps299089 Why is bacterioplankton growth in coral reef framework cavities enhanced? S. R. Scheffers1, 2, 3,4,*, R. P. M. Bak1,3, F. C. van Duyl1 1Royal Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, Texel, The Netherlands2CARMABI Foundation, PO Box 2090, Willemstad, Curaçao, Netherlands Antilles3University of Amsterdam, IBED, PO Box 94766, 1090 GT Amsterdam, The Netherlands4Present address: University of Essen, Faculty of Biology and Geography, Universitätsstraße 5, 45141 Essen, Germany *Email: scheffers@t-online.de ABSTRACT: Abundance, growth rates and nutrient limitation of the heterotrophic bacteria present in the reef water column and reef cavity water were measured on a fringing reef at Curaçao (Netherlands Antilles). Bacterial in situ growth rates were measured using dialysis bags. Nutrient limitation was measured using bioassays with different amendments of inorganic nutrients (nitrate, ammonium, phosphate) and dissolved organic carbon (glucose). Cell sizes were measured in the reef water column and over an intra-cavity gradient inside reef cavities, from the cavity center to the wall of the cavity. Bacterial abundance was lower in cavities, while growth rates were on average 3.6 times higher than in open reef water. The bacterial community in open reef water was limited in its growth by all nutrients, in contrast to cavity water, in which bacteria were limited by phosphate. Cell volumes decreased significantly from open reef water towards the cavity wall. Results suggest that conditions in cavities have a positive effect on bacterial growth. Growth limitation by N is alleviated through enhanced mineralization in cavities. Through rapid exchange with the ambient water, cavities enrich the overlying reef water with inorganic N. KEY WORDS: DOC · DIP · DIN · Nutrient limitation · Growth rates · Heterotrophic bacteria ·Cavities · Coral reef Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 299. Online publication date: September 01, 2005 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2005 Inter-Research.

Highlights

Most coral reefs occur in oligotrophic waters with low dissolved nutrient concentrations and low standing stocks of phyto- and bacterioplankton
After 24 h of incubation in dialysis bags, bacterial abundance was significantly higher in cavities than in reef water (t-test for paired comparisons: t = 4.1; p < 0.001), indicating that most experiments with cavity water reached a higher bacterial abundance after 24 h of incubation (Fig. 2b)
We found large differences in bacterial abundance and doubling times between reef and cavity waters over small spatial scales (10 to 100 cm)

Summary

Introduction

Most coral reefs occur in oligotrophic waters with low dissolved nutrient concentrations and low standing stocks of phyto- and bacterioplankton. During passage over the coral reef, water features change and obtain a reef signature often characterized by depleted phytoplankton and bacterioplankton concentrations and enhanced dissolved nutrient concentrations Growth rates of heterotrophic bacterioplankton in coral reef overlying waters are usually enhanced the closer the bacteria get to the reef and the coral bottom (Moriarty et al 1985, Gast et al 1999, van Duyl & Gast 2001). Besides a source of organic matter via benthic primary producers (corals and benthic algae), the reef bottom is a sink for particulate organic matter (e.g. plankton, detritus) and source of inorganic nutrients (Capone et al 1992, Hatcher 1997, Rasheed et al 2002). Hotspots for plankton depletion and mineralization on coral reefs are cryptic habitats, such as crevices

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