Spatial and temporal patterns of microphytobenthic taxa of estuarine tidal flats in the Tagus Estuary (Portugal) using pigment analysis by HPLC

Abstract

ABSTRACT. Measurements of natural estuarine microphytobenthos communities were carried out in samples of intertidal sedlrnents of the Tagus Estuary (Portugal) by means of pigment analysis by HPLC in order to identify microphytobenthos composition. The relative abundance of taxa was determined by microscopic observations. During spring 16 sites were sampled and 3 of them, differing in sediment grain size and tidal level, were, \ isited fortnightly for 1 yr. At all sites throughout the year, diatoms were the dominant algal group, evidenced by the. relatively high concentrations of chlorophylls cI+c2, fucoxanthin, neofucoxanthin, diadinoxanthin, diatoxanthin and 0-carotene. Chl b and diatoxanthin were related with observed euglenophyte populations, zeaxanthin with cyanobacteria, lutein with macrophyte debris and alloxanthin with falling phytoplanktonic cells of cryptophytes. The spatial study allowed a distinction between sites regarding the presence of macrophyte debris, euglenophytes or only diatolns. The temporal survey showed the seasonal trends of diatoms and cyanobacteria and the main periods of plant debris deposition. Pheophytin a and chlorophyllide a concentrations were quite low. Degraded chloropigments were constituted mainly of pheophorbides a, 9 of which were quantified. The most abundant among them indicated intensive grazing by ~nacrozoobenthos at the muddy stations.

Carbon and nitrogen cycling on intertidal mudflats of a temperate Australian estuary. III. Sources of organic matter

“…2). The presence of chlorophytes and cyanobacteria has also been recorded in other MPB communities (Cahoon 1999), including intertidal sediments (Barranguet et al 1997, Brotas & Plante-Cuny 1998. During spring at Site CF, the xanthophyte Vaucheria sp.…”

“…Most studies of MPB on estuarine mudflats report a predominance of diatoms (Cariou-Le Gall & Blanchard 1995, Barranguet et al 1997, Brotas & Plante-Cuny 1998, Lucas & Holligan 1999, Cahoon & Safi 2002. In these studies, relatively high concentrations of fucoxanthin have revealed a dominance of diatoms with fuc:chl a ratios of between 0.35 and 1.6 being observed.…”

“…Simple visual methods have commonly been used, but they are laborious, and microscopic cells are difficult to identify and count on a large scale (Brotas & Plante-Cuny 1998, Cabrita & Brotas 2000. The presence of sediment often interferes with a range of measurements including cell-counting, algal C:N ratios and stable-isotope measurements, so it can be advantageous to separate the MPB from the sediment for these measurements (Couch 1989, Cabrita & Brotas 2000.…”

“…Most studies to date have shown that the MPB on mudflats is dominated by diatoms (Cariou-Le Gall & Blanchard 1995, Barranguet et al 1997, Brotas & Plante-Cuny 1998, Lucas & Holligan 1999, Cahoon & Safi 2002, but this may shift seasonally to chlorophytes and cyanobacteria (Barranguet et al 1997). In some areas, intertidal sediments may be dominated by cyanobacteria where high rates of nitrogen fixation may supply a significant amount of nitrogen to the benthic community (Stal et al 1984, Bautista & Paerl 1985, Stal 1995.…”

A multiple biomarker approach to tracking the fate of an ice algal bloom to the sea floor

“…3). Although phaeophorbides were used to trace grazing processes in both the water column (JeVrey 1974;Carpenter et al 1986;Spooner et al 1994) and the sediment (Brotas and Plante-Cuny 1998;Riaux-Gobin et al 2000), it has recently been argued that they may not always be a relevant indicator of herbivorous activities (Villanueva and Hastings 2000;Ford and Honeywill 2002). The chl a:phaephorbide a ratio by itself does not allow to conclude to a relative enhancement of the macrofauna activities.…”