|
Vol. 46 No. 1, 2007
Composition of the Trophic Structure of Zooplankton in a
Shallow Temperate Estuary (Mondego Estuary, Western Portugal)
Fernando
Morgado1,*, Carla Quintaneiro1, Elisa Rodrigues1, Manuel Ramiro
Pastorinho1, Paula Bacelar-Nicolau2, Luis Vieira1, and Ulisses Manuel
Azeiteiro2,3
1Department
of Biology, University of Aveiro, 3810-193 Aveiro, Portugal
2Department of Exact Sciences and Technologies, Open
University, 1269-001 Lisboa, Portugal
3IMAR-CIC, University of Coimbra, 3004-517 Coimbra,
Portugal
Fernando
Morgado, Carla Quintaneiro, Elisa Rodrigues, Manuel Ramiro Pastorinho,
Paula BacelarNicolau, Luis Vieira, and Ulisses Manuel Azeiteiro (2007) The
south arm of Mondego Estuary, western Portugal is characterized by
shallow depths and marked longitudinal spatial gradients, namely the
tidally induced salinity gradient and an eutrophication gradient. The
aims of this work were to study the zooplankton composition and trophic
structure of the 335 µm taxocenosis in 2 different locations of the
salinity and eutrophication gradients in the south arm. The 2 sampling
stations displayed significantly different patterns of temporal
variations in environmental variables. The total zooplankton density at
each station showed significant spatial and temporal variabilities.
However, the number of taxa did not show significant differences among
months or between sites. The densities of the most abundant taxa
significantly differed between the sampling stations and throughout the
study period. The zooplankton assemblages were dominated by omnivores,
representing 43.9% of the total zooplankton (with herbivores and
carnivores representing 4.4% and 0.5%, respectively). Omnivores were
significantly more abundant during autumn, winter, and spring,
particularly in Oct., Mar., and May, at station 2, and during Jan.,
Mar., and Apr., at station 1. Herbivores were significantly more
abundant during autumn, late winter, and spring particularly at station
1. Carnivores showed low densities throughout the year, being more
abundant in summer and autumn. Despite the detected similarities to
other temperate estuaries, the results of this work may indicate
environmental stresses in this ecosystem: the spatial structure
dominates seasonal patterns; and there are low diversities and high
numbers of resident populations. This kind of ecological pattern has
been previously reported for other biological communities. The
prevailing conditions in Mondego Estuary, namely eutrophication, should
result in the development of opportunistic adaptive strategies among
invertebrates.
Key words: Zooplankton distribution,
Zooplankton structure, Eutrophication, Mondego Estuary.
*Correspondence: Tel:351-234370786 Fax:351-234426408
E-mail:fmorgado@bio.ua.pt
|
