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Spatial distribution and seasonal variation of subtidal polychaete populations in the Mondego Estuary (western Portugal)
Pardal, M.A.; Marques, J.C.; Bellan, G. (1993). Spatial distribution and seasonal variation of subtidal polychaete populations in the Mondego Estuary (western Portugal). Cah. Biol. Mar. 34(4): 497-512
In: Cahiers de Biologie Marine. Station Biologique de Roscoff: Paris. ISSN 0007-9723, more
Peer reviewed article  

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Keyword
    Brackish water

Authors  Top 
  • Pardal, M.A.
  • Marques, J.C.
  • Bellan, G., more

Abstract
    The Mondego Estuary consists of two arms, north and south. Environmental stress is severe, essentially due to harbour activities, salt-works, aquaculture farms, and nutrients and chemicals discharged from agricultural areas of the lower Mondego river valley. Polychaetes were found to be the most abundant macrofaunal group of the Mondego estuary subtidal community, representing about 34.5% of the species and 63% of the individuals sampled. Both biological and physicochemical data were analysed by principal components analysis (PCA), and data on the Polychaete fauna was also analysed with regard to spatial and temporal variations of total abundance. The Mondego Estuary seems to present an impoverished subtidal Polychaete fauna with regard to the number of species, although the south arm presents enhanced populations. In the inner areas of the south arm, the Polychaete fauna is characterized by abundant populations of Amage adspersa, followed by more sparse populations of Capitella capitata, Heteromastus filiformis, Polydora ciliata, and Streblospio shrubsolii. The north arm exhibited an extremely impoverished Polychaete fauna, both in number of species and total abundance, as compared to the south arm. In the downstream area of the south arm and near the mouth of the estuary the Polychaete fauna was characterized by the occurrence of a mixture of uncommon species e.g. Eulalia sp., Eteone picta, Glycera convoluta, Lagis koreni, Nephthys spp., and Spio decoratus, reflecting a stronger marine influence. The subtidal Polychaete fauna appears to be controlled primarily by physicochemical factors, especially sediments type and salinity. Biologically, the two arms of the estuary constitute distinct sub-systems, with dissimilar physicochemical characteristics.

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