by Freitas, Ubiratan de

Abstract (Summary)
Shrimp farms activities tend to increase the organic matter sedimentation rate, by extreme inputs of excreta products and shrimp food (commercial shrimp diet) into the environment. In certain environmental conditions, the auto depuration system can be surpassed, generating a great production of nutrients at the sedimentary layer, as resultsof benthic metabolism intensification and, consequently the system can be induced to a eutrofication processes and anoxia. In the present study, in situ incubations withtransparent and opaque chambers had been used to evaluate the benthic metabolism in shrimp farm areas in the Patos Lagoon estuary (pen enclosures and ponds). In the penenclosures, it was evident that it has a clear interference of the culture in the processes of benthic regeneration of nutrients, resulting in increasing of phosphate and nitrogenfluxes (in the ammonium specie). The registered average flux in the opaque chamber, at the end of the period of culture, was 52,8 mg.L-1 of N-ammonium and 5,41 mg.L-1 of Pphosphate. In the pond shrimp farm, the fluxes of nutrients and the consumption of oxygen by the sediment were generally higher than the pen enclosures. However, theculture of ponds farm has a commercial scale, compared to the pen enclosures that is experimental (scientific research). In function of this, close to the shrimp harvest periodthe values of N-ammonium in the effluent had been 3 orders of magnitude higher than the pen enclosure. Besides that, the effluent values registered didn?t disrespect the values established by Brazilian environmental legislation. Even considering that this activity have a local and temporary distribution (only 4 to 5 months of the year), it is important to call attention to the sediment oxygen consumption and the input of nutrients deriving from the regeneration of organic matter which it?s enhanced in shallow waters and restricted circulation areas (as small bays), locations where shrimp culture is developed in the Patos Lagoon estuary. It?s important to study the environmental zoning and support capacity (assimilation capacity), to determine areas for expansion of the activity, also quantifying the maximum number of units supported by the environment, in order to prevent or to minimize the potential negative environmental impacts.
This document abstract is also available in Portuguese.
Bibliographical Information:

Advisor:Alexandre Matthiensen; Eunice da Costa Machado; Luis Henrique da Silva Poersch; Luiz Felipe Hax Niencheski

School:Fundação Universidade Federal do Rio Grande

School Location:Brazil

Source Type:Master's Thesis

Keywords:Shrimp farms benthic metabolism chambers mineralization nutrients flux


Date of Publication:03/02/2006

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