80
Luis Felipe Niencheski . Maria da Gra~a Baumgarten· Gilberto Fillmann . Herbert L. Windom
4.4
Conclusions
Nutrients concentrations in the Patos Lagoon Estuary exhibit small seasonal variability.
From previous data (Kantin 1983; Niencheski et al. 1986; Vilas Boas 1990) annual nutrient patterns appear to vary somewhat from year to year. The complicated geography of the estuary results in complex hydrographic conditions. Also, in this environment there are several sources of nutrients, including surface freshwater drainage from
land, direct waste discharge, fallout of particulates from the atmosphere and release
during dredging. There are yearly variations in the rainfall and soil leaching, that cause
variation in river input, which may propagate through the nutrient cycles.
Nutrient inputs to the estuarine region of Patos Lagoon from continental runoff is
relatively small since the major 5 rivers that supply this system empty into the Northern region and the nutrients contained in the freshwater input are mostly consumed
during transit, a 250 km path, to the estuarine zone.
Results of this study suggest that short term variability in nutrients and TSM in
the main navigation channel of Patos Lagoon Estuary is primarily caused by res uspension of sediment and by the penetration of adjacent coastal waters along the bottom. In semi-enclosed bays of the estuary, winds play an important role in sediment
resuspension. Nutrient input from Rio Grande's urban, industrial and harbour activities is observed primarily in adjacent bays. However, atmospheric fallout near the industrial park, not studied as a part of this research, may explain some high surface
water concentrations. The results also suggest that, at least on some occasion (i.e., in
the fall) nutrients may in fact be limiting.
Acknowledgements
The authors would like to thank the CNPq/Brazil for a grant (202062/91) to Luis Felipe
Niencheski during the study period and the Skidaway Institute of Oceanography,
University System of Georgia, for all facilities provided.
References
Abreu PC (1992) Phytoplankton production and the microbial food web of the Patos Lagoon Estuary,
southern Brazil. PhD thesis, Universitat Bremen, Germany
Aminot A, Chaussepied M (1983) Manuel des analyses chimiques en milieu marin. Centre National
Exploitation des Oceans, Brest
Almeida MT, Baumgarten MGB, Rodrigues RMO (1993) Identifica~ao das possiveis fontes de
contamina~ao das aguas que margeiam a cidade do Rio Grande. Serie "Documentos TecnicosOceanografia 06", FURG, Rio Grande, 34 p
Aston SR (1980) Nutrients, dissolved gases and general biogeochemistry in estuaries. In: Olausson E,
Cato I (eds) Chemistry and biogeochemistry of estuaries. Wiley, pp 233-262
Baumgarten MG, Niencheski LF (1990) 0 estuario da Laguna dos Patos: varia~6es de alguns parametros fisico-quimicos da agua e metais associados ao material em suspensao. Ciencia e Cultura
42:390-396
Baumgarten MG, Niencheski LF, Kuroshima KN (1995) Qualidade das aguas estuarinas que margeiam
o municipio do Rio Grande (RS): Nutrientes e detergente dissolvidos. Rev Atlantica 17:19-36
Brockmann U (1990) Nutrients and suspended material in Shannon and Elbe estuaries. In: Kausch H,
Wilson jG, Barth H (eds) Biogeochemical cycles in two major european estuaries: the Shanelbe Project. Commission of the European Communities Water Pollution Research Report NOI5, pp 24-43
Luis Felipe Niencheski . Maria da Gra~a Baumgarten· Gilberto Fillmann . Herbert L. Windom
4.4
Conclusions
Nutrients concentrations in the Patos Lagoon Estuary exhibit small seasonal variability.
From previous data (Kantin 1983; Niencheski et al. 1986; Vilas Boas 1990) annual nutrient patterns appear to vary somewhat from year to year. The complicated geography of the estuary results in complex hydrographic conditions. Also, in this environment there are several sources of nutrients, including surface freshwater drainage from
land, direct waste discharge, fallout of particulates from the atmosphere and release
during dredging. There are yearly variations in the rainfall and soil leaching, that cause
variation in river input, which may propagate through the nutrient cycles.
Nutrient inputs to the estuarine region of Patos Lagoon from continental runoff is
relatively small since the major 5 rivers that supply this system empty into the Northern region and the nutrients contained in the freshwater input are mostly consumed
during transit, a 250 km path, to the estuarine zone.
Results of this study suggest that short term variability in nutrients and TSM in
the main navigation channel of Patos Lagoon Estuary is primarily caused by res uspension of sediment and by the penetration of adjacent coastal waters along the bottom. In semi-enclosed bays of the estuary, winds play an important role in sediment
resuspension. Nutrient input from Rio Grande's urban, industrial and harbour activities is observed primarily in adjacent bays. However, atmospheric fallout near the industrial park, not studied as a part of this research, may explain some high surface
water concentrations. The results also suggest that, at least on some occasion (i.e., in
the fall) nutrients may in fact be limiting.
Acknowledgements
The authors would like to thank the CNPq/Brazil for a grant (202062/91) to Luis Felipe
Niencheski during the study period and the Skidaway Institute of Oceanography,
University System of Georgia, for all facilities provided.
References
Abreu PC (1992) Phytoplankton production and the microbial food web of the Patos Lagoon Estuary,
southern Brazil. PhD thesis, Universitat Bremen, Germany
Aminot A, Chaussepied M (1983) Manuel des analyses chimiques en milieu marin. Centre National
Exploitation des Oceans, Brest
Almeida MT, Baumgarten MGB, Rodrigues RMO (1993) Identifica~ao das possiveis fontes de
contamina~ao das aguas que margeiam a cidade do Rio Grande. Serie "Documentos TecnicosOceanografia 06", FURG, Rio Grande, 34 p
Aston SR (1980) Nutrients, dissolved gases and general biogeochemistry in estuaries. In: Olausson E,
Cato I (eds) Chemistry and biogeochemistry of estuaries. Wiley, pp 233-262
Baumgarten MG, Niencheski LF (1990) 0 estuario da Laguna dos Patos: varia~6es de alguns parametros fisico-quimicos da agua e metais associados ao material em suspensao. Ciencia e Cultura
42:390-396
Baumgarten MG, Niencheski LF, Kuroshima KN (1995) Qualidade das aguas estuarinas que margeiam
o municipio do Rio Grande (RS): Nutrientes e detergente dissolvidos. Rev Atlantica 17:19-36
Brockmann U (1990) Nutrients and suspended material in Shannon and Elbe estuaries. In: Kausch H,
Wilson jG, Barth H (eds) Biogeochemical cycles in two major european estuaries: the Shanelbe Project. Commission of the European Communities Water Pollution Research Report NOI5, pp 24-43