INVESTIGADORES
GOMEZ Nora
artículos
Título:
Effects of dredging on benthic diatom assemblages in a lowland stream
Autor/es:
LICURSI M.; GOMEZ N,
Revista:
JOURNAL OF ENVIRONMENTAL MANAGEMENT
Editorial:
Elsevier
Referencias:
Lugar: Netherlands; Año: 2009 p. 973 - 982
ISSN:
0301-4797
Resumen:
The objective of this study was to assess the effects of dredging on the structure and composition of
diatom assemblages from a lowland stream and to investigate whether the response of diatom assemblages
to the dredging is also influenced by different water quality. Three sampling sites were established
in Rodrý´guez Stream (Argentina); physico-chemical variables and benthic diatom assemblages were
sampled weekly in spring 2001. Species composition, cell density, diversity and evenness were estimated.
Diatom tolerance to organic pollution and eutrophication were also analyzed. Differences in
physico-chemical variables and changes in benthic diatom assemblages were compared between the
pre- and post-dredging periods using a t-test. Data were analyzed using Principal Components Analysis
(PCA), non-metric multidimensional scaling (MDS) ordination and cluster analysis. The effects of
dredging in the stream involve two types of disturbances: (i) in the stream bed, by the removal and
destabilization of the substrate and (ii) in the water column, by generating chemical changes and an
alteration of the light environment of the stream. Suspended solids, soluble reactive phosphorus and
dissolved inorganic nitrogen were significantly higher in post-dredging periods. Physical and chemical
modifications in the habitat of benthic diatoms produced changes in the assemblage; diversity and
species numbers showed an immediate increase after dredging, decreasing at the end of the study
period. Changes in the tolerance of the diatom assemblage to organic pollution and eutrophication were
also observed as a consequence of dredging; in the post-dredging period sensitive species were replaced
by either tolerant or most tolerant species. These changes were particularly noticeable in site 1 (characterized by its lower amount of nutrients and organic matter previous to dredging), which showed an increase in the amount of nutrients and oxygen demand as a consequence of sediment removal. However, these changes were not so conspicuous in sites 2 and 3, which already presented a marked water quality deterioration before the execution of the dredging works.