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A B S T R A C TA worldwide modeling effort has been proposed by the LOICZ (Land-Ocean Interactions in the Coastal Zone) Program to foster the acquisition of intercomparable data on land-ocean fluxes in estuaries and continental shelf ecosystems from all continental margins. As part of the South American component of this initiative, we present flux estimates of water, salt, dissolved inorganic phosphorus (DIP), dissolved inorganic nitrogen (DIN) and plankton for the estuarine system of Paranaguá Bay, southern Brazil, based on the LOICZ modeling approach and local data obtained during the 1990's. This system is strongly influenced by a seasonal meteorological cycle, represented by the rainy/summer and dry/winter periods. Semi-diurnal tides of up to the 2.7-m range are responsible for the short time-scale dynamics. The model indicated a potential water export to the adjacent coast of up to 7 x 10 6 m 3 d -1 in the dry season, and 28 x 10 6 m 3 d -1 during the rainy season. The system exhibits seasonal and spatial variations in DIP and DIN fluxes. ∆DIP amounted to +2.3 x 10 6 mol P yr -1 and ∆DIN to -2.7 x 10 6 mol N yr -1 , suggesting that net production of phosphate and consumption of inorganic nitrogen predominate throughout in the system. Fluxes and therefore export of DIN and eespecially of DIP are higher in the rainy season. Stoichiometric estimates based on the C:N:P ratios of the reacting particulate organic matter (mangrove and plankton detritus) suggest that net denitrification predominates all over the bay, with values between -24.3 and -10.6 x 10 6 mol N year -1 . Estimated seaward outflows had little effect upon the fate of the phyto-and zooplankton biomass in different sectors of the bay. This is exemplified by the low net export of algal production from the upper to the middle sectors of the estuary. R E S U M OUm esforço global de modelagem foi proposto pelo Programa LOICZ (Land-Ocean Interactions in the Coastal Zone) para promover a aquisição de dados comparáveis sobre fluxos continente-oceano em ecossistemas estuarinos e de plataforma em todos os continentes. Como parte do componente sulamericano desta iniciativa, apresentamos neste trabalho estimativas de fluxo de água, sal, fósforo inorgânico dissolvido (DIP), nitrogênio inorgânico dissolvido (DIN) e plâncton para o sistema estuarino da Baía de Paranaguá, obtidas a partir da aplicação de modelos sugeridos pelo programa LOICZ. Este sistema é fortemente influenciado por um ciclo meteorológico sazonal, representado pelos períodos chuvosos de verão e secos de inverno. As marés semidiurnas, com variação de até 2,7 m, são responsáveis pela dinâmica estuarina de curta escala temporal. Nossos resultados indicam uma exportação potencial de água para a área costeira adjacente de até 7 x 10 6 m 3 d -1 no período seco e mais de 28 x 10 6 m 3 d -1 no período chuvoso. O sistema exibe variações sazonais e espaciais nos fluxos de DIP e DIN. O ∆DIP atingiu +2.3 x 10 6 mol P ano -1 e o ∆DIN to -2.7 x 10 6 mol N ano -1 , sugerindo que a produção líquida de fosfato...

In the Central South Brazil Bight, a multispecific demersal trawl fishery is conducted by trawlers licensed for the industrial pink shrimp (Penaeus paulensis and Penaeus brasiliensis) fishery. In addition to the pink shrimp, many by‐catch species have become increasingly valued in the last two decades. In spite of the importance of this multispecific fishery, the oceanographic characteristics of the inner continental shelf, onshore the 100 m isobath, are poorly known. In this paper we present, for the fist time, monthly oceanographic records taken from December 1995 to May 1997 with the R/V ‘Diadorim’ at two of the main fishing grounds of this region. Water temperature data showed the formation of a strong thermocline during summer, from November to April. This thermal gradient, due to the South Atlantic central water (SACW) intrusion that reaches these shallow waters, disappeared with the homogenization of the water column during autumn and winter, from May to September. This cold and low salinity water does not originate from local river discharges, but also represents an advection of sub‐Antartic water mass. After this and during spring, a new thermocline develops, reaching its maximal expression from February to March. A maximal gradient was registered in February 1997, when the temperature dropped from 26°C at 7 m to 16°C at 14 m depth. This result shows that the SACW intrusion is a large‐scale phenomenon that regularly influences the whole inner continental shelf up to 20 m. Demersal fishing grounds located in this area were covered during summer by a cold and nutrient‐rich mass of water that resulted in an unusual maximum of chlorophyll a values near the bottom (30 m). The homogenization of the water column and the presence of another cold water mass during winter resulted in a strong semi‐annual thermal cycle on the bottom. The role of this important oceanographic process in fishery production and dynamics deserves further investigation, but the data presented here show evidence for the importance of this phenomenon.

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