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Spatio-temporal distribution of the microphytobenthic biomass in intertidal flats of Tagus Estuary (Portugal)

  • Vanda Brotas
  • Teresa Cabrita
  • Ana Portugal
  • João Serôdio
  • Fernando Catarino
Conference paper
Part of the Developments in Hydrobiology book series (DIHY, volume 104)

Abstract

A study on spatio-temporal distribution of microphytobenthos in intertidal zones of Tagus Estuary was carried out from 1990 to 1992. Near Lisbon, Portugal, Tagus Estuary is a shallow mesotidal estuary, covering an area of 320 km2. The intertidal area ranges from 20 to 40% of the total area and it is constituted mainly by mudflats. Intertidal flats are richly populated by microalgae, diatoms being the most important and ubiquitous group.

Spatial variation of microphytobenthos was studied in spring 1990, 21 different sites were sampled. Microphy- tobenthos biomass was evaluated as chlorophyll a content of the surface centimeter, ranging from 10 to 240 mg m-2. A Principal Component Analysis showed that 62% of the total variability found in intertidal flats of Tagus estuary could be attributed to two major factors: sediment type and tidal height. A hierarchical grouping defined 3 major groups of similar stations, each one representing a different strata of the ecosystem.

One station from each group was chosen for the study of the temporal variation. A sampling program took place from April 1991 to April 1992, with fortnightly sampling, the Chl a ranged from 20–300 mg m-2. No clear seasonal variation was found, and our results indicated that tidal height of sampled site played an essential role in temporal biomass evolution, thus upper littoral sites were influenced by climatic parameters, whereas in lower sites action of tides mainly controlled microphytic biomass.

Key words

benthic microalgae spatial heterogeneity seasonal variation intertidal zones 

Résumé

Une étude sur l’hétérogénéité spatio-temporelle du microphytobenthos dans les sédiments intertidaux de l’Estuaire du Tage a été accompli de 1990 à 1992.

L’Estuaire du Tage, prés de Lisbonne (Portugal) est un estuaire peu profond, mesotidal, avec une aire total de 320 km2. L’aire intertidale est comprise entre 20 et 40% du total, et constituée surtout par des vasières. Ces slikkes sont peuplées par une communauté assez riche de microalgues, ou les diatomées sont les plus abundantes.

La variation spatialle du microphytobenthos était évalué au Printemps 1990, ou 21 différentes stations étaient échantillonnées. La biomasse était évalué par la concentration en chlorophylle a du premier centimètre de sédiment, qui a varié de 10 à 240 mg Chl a m-2. Une Analyse en Composants Principales a montré que 62% de la variabilité de la biomasse était lié à deux facteurs: le sédiment et l’hauteur vis-à-vis la marée. Une classification hiérarchique des stations par similitude a établi 3 groupes principaux, représantant les différents strates de l’écosystème.

Une station de chaque groupement a été choisie pour l’étude de la variation temporelle, qui s’est déroulé d’avril 1991 à avril 1992, avec des prélèvements deux fois par mois. Les valeurs de Chl a obtenus vont de 20 à 300 mg m-2. Les variations saisonnières observées ne sont pas claires: nos résultats indiquent que l’hauteur de la station (m) joue un rôle essentiel dans l’évolution temporel de la biomasse, c’est a dire, la biomasse microalgal des sites du supra-littoral est influencié par les paramètres climatiques, tandis que dans l’infra-littoral c’est faction des marées le facteur principal.

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Copyright information

© Springer Science+Business Media Dordrecht 1995

Authors and Affiliations

  • Vanda Brotas
    • 1
  • Teresa Cabrita
    • 1
  • Ana Portugal
    • 1
  • João Serôdio
    • 1
  • Fernando Catarino
    • 1
  1. 1.Departamento de Biologia VegetalFaculdade de Ciências da Universidade de LisboaLisboaPortugal

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