Authors: E Maggi A C Jackson T Tolhurst A J Underwood M G Chapman
Publish Date: 2012/08/31
Volume: 701, Issue: 1, Pages: 301-312
Abstract
Intertidal microphytobenthos MPB are important primary producers and provide food for herbivores in soft sediments and on rocky shores Methods of measuring MPB biomass that do not depend on the time of collection relative to the time of day or tidal conditions are important in any studies that need to compare temporal or spatial variation effects of abiotic factors or activity of grazers Pulse amplitude modulated PAM fluorometry is often used to estimate biomass of MPB because it is a rapid nondestructive method but it is not known how measures of fluorescence are altered by changing conditions during a period of low tide We investigated this experimentally using in situ changes in minimal fluorescence F o 15 on a rocky shore and on an estuarine mudflat around Sydney Australia during low tides On rocky shores the time when samples are taken during low tide had little direct influence on measures of fluorescence as long as the substratum is dry Wetness from wavesplash seepage from rock pools runoff rainfall etc had large consequences for any comparisons On soft sediments fluorescence was decreased if the sediment dried out as happens during lowspring tides on particularly hot and dry days Surface water affected the response of PAM and therefore measurements used to estimate MPB emphasising the need for care to ensure that representative sampling is done during low tideEM was supported by an Italian fellowship from CoNISMa the entire study was supported by funds from the Australian Research Council through the Centre for Research on Ecological Impacts of Coastal Cities and ARC Discovery Projects to AJU and to MGC and TT We thank Paul Devlin and Mark Ellis for assistance in the field and Richard Murphy for information on the MPB communities
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