Se reportan observaciones sobre alimentación de la ballena franca austral y zooplancton disponible, realizadas en Bahía Pirámides (Golfo Nuevo). Se compararon datos de plancton, comportamiento trófico de las ballenas y temperaturasalinidad y clorofila-a registrados los días 10 y 19 de octubre de 2005. El 19/10 la biomasa zooplanctónica fue significativamente mayor, observándose un número alto de ballenas filtrando en superficie. Esta conducta se observó desde el 17 al 21/10. El evento de forrajeo descrito, confirma que la ballena franca se alimenta en este zona reproductiva de parches de zooplancton con una adecuada composición y alta densidad, en primavera. Palabras clave: Ballena franca austral, biomasa zooplanctónica, Calanoides cf. carinaus, Calanus australis, eufáusidos 1 Rowntree VJ, LO Valenzuela, P Franco-Fraguas & J Seger. 2008. Foraging behaviour of southern right whales (Eubalaena australis) inferred from variation of carbon stable isotope ratios in their baleen. Paper SC/60/BRG23 presented to the IWC Scientific Committee,

Studies based on continuous monitoring of diel changes in dissolved oxygen concentration allow the estimation of ecosystem metabolism and provide a measure of the overall trophic processes of an ecosystem. In this study, net ecosystem production (NEP), community/ecosystem respiration (R), and gross primary production (GPP) rates were estimated in relation to physicochemical and climatic variables for 18 months in La Salada, a saline shallow lake. Net autotrophic conditions prevailed during the study period (NEP: 64.05 ± 44.22 mmol O 2 m -2 day -1 ). GPP and R were positively correlated and were synchronized on a daily timescale, with GPP typically greater than R. Principal component analysis revealed that monthly rates of GPP, R, and NEP responded, as expected, to temperature and light seasonal patterns. Water level and conductivity fluctuations, because of evapoconcentration and water management, were relevant as a driver of the physicochemical and biological characteristics of the lake. In saline lakes as La Salada, an adequate management of water resources will be relevant to maintain the ecosystem equilibrium and the quality of its resources.

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Surf zones of sandy beaches are poorly studied in comparison to estuarine and continental shelf waters, specifically because of the difficulties experienced in sampling in high-energy environments. The zooplankton of these areas, therefore, has received less

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Menéndez, M. C., Dutto, M. S., Piccolo, M. C., and Hoffmeyer, M. S. 2012. The role of the seasonal and semi-diurnal tidal cycle on mesozooplankton variability in a shallow mixed estuary (Bahía Blanca, Argentina). – ICES Journal of Marine Science, 69: 389–398. The role of the seasonal and semi-diurnal tidal cycle on mesozooplankton dynamics was investigated in the inner zone of the Bahía Blanca Estuary (BBE), Argentina. Hydrological data and mesozooplankton samples were obtained bimonthly from December 2004 to April 2006, during 14 h tidal cycles. The mesozooplankton community was represented by 33 taxa. Taxa richness was greater near the bottom, where the contribution of benthic forms was notable. Abundances were greatest during summer (>5500 ind. m−3) and lowest during winter (<70 ind. m−3). The mesozooplankton community was dominated by Acartia tonsa and Eurytemora americana. Multivariate analyses revealed significant seasonal differences in community structure, especially in terms of density. Seasonal differences in community structure are well explained by the natural change of abiotic and biotic conditions, but temperature played a key role in structuring the mesozooplankton community. The zooplankton was significantly more abundant during the ebb, suggesting that local hydrological conditions are responsible for the spatial variations. The results demonstrate how variable the mesozooplankton community structure can be over different time-scales and provide a better understanding of zooplankton variability in the BBE and other temperate, turbid, mixed systems.

The effects of a sewage effluent with no treatment on the mesozooplankton structure and the environmental quality were evaluated in the Bahía Blanca Estuary, during June to November 1995. The highest values of particulate organic matter, nutrients and specially phosphate, were observed in the effluent discharge zone. In addition, taxa richness, mesozooplankton abundance and Shannon diversity values were lower in the sewage discharge area compared with the less polluted area. Eurytemora americana and Acartia tonsa as well as larvae of Balanus glandula, Neohelice granulata and Spionidae were found in the discharge area with lower densities. These results highlight the importance of sewage effluent effects on mesozooplankton community providing background data to use in other monitoring programmes.