Investigação

Início / Investigação / Artigos / The issue of outwelling in the Guadiana River estuary, Portugal. Some findings and research suggestions in the context of recent evidence.

The issue of outwelling in the Guadiana River estuary, Portugal. Some findings and research suggestions in the context of recent evidence.

Ano
2007
Abstract

The “Outwelling Theory” states that salt marshes play a major role exporting production to adjacent estuarine and coastal ecosystems. However, it has been found that some marshes act as net importers instead of net exporters of organic matter and nutrients. Once we include mangroves and refine the analysis to comprehend bacterioplankton, organic and stable isotope tracers, the picture became, once more, more complex, making room for a revival of the idea. The exchanges between the Castro Marim salt marsh and the main estuary were tentatively established determining periodically in a selected cross-section TSS, FSS, VSS, NH4, NO2, NO3, NKjeldhal, SiO4, PO4, TDP, Chlorophyll a and Pheopigments, measuring their fluxes along tidal cycles and computing the corresponding budgets. Apparently the sedimentary behavior of the marsh will be close to equilibrium, in the period studied. However, it will import mainly inert matter and export mainly organic matter, in the same period. Moreover, extrapolating these results to the entire Guadiana salt marshes, the exchanges of sediment does not seem to be significant. Particularly, the marshes will not significantly trap sediment transported by the main river (0.5%). It seems to follow also, that in a general way, the Guadiana salt-marshes might have a more significant role than it was anticipated, in the system economy of OM and nutrients, and their outwelling to coastal waters, assuring ouputs that could amount to something like 6 % of the river load of N, 1.2% of the river load of P, and 20-57% of the river load of TOC, in an average year, and 42% of the river load of N and 35% of the river load of P in a dry year. These findings suggest that a more refined investigation, over an extended period of time, is certainly worthwhile.

Keywords

Salt marsh; Estuary; Outwelling; Nutrients

Tipo de Artigo
Investigação
Tipo de Revisão
Internacional
Âmbito Geográfico
Internacional
Situação
Publicado
Área de Trabalho
Referência

Bettencourt, A; Quaresma, L; Lança, M (2007). The issue of outwelling in the Guadiana River estuary (Portugal): some findings and research suggestions in the context of recent evidence. Hydrobiologia, 578: 157‑168