María C. Menéndez

Sewage pollution effects on mesozooplankton structure in a shallow temperate estuary

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.

Planktonic food and foraging of Eubalaena australis, on Peninsula Valdés (Argentina) nursery ground

Se reportan observaciones sobre alimentacion de la ballena franca austral y zooplancton disponible, realizadas en Bahia Piramides (Golfo Nuevo). Se compararon datos de plancton, comportamiento trofico de las ballenas y temperaturasalinidad y clorofila-a registrados los dias 10 y 19 de octubre de 2005. El 19/10 la biomasa zooplanctonica fue significativamente mayor, observandose un numero alto de ballenas filtrando en superficie. Esta conducta se observo 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 composicion y alta densidad, en primavera.

Mesozooplankton composition and spatial distribution, Nuevo Gulf, Patagonia, Argentina

The composition and spatial distribution of mesozooplankton of Nuevo Gulf, Argentina, were analyzed from surface samples taken on July, 1997. A total of 32 taxa were recorded. The highest abundances were found close to Nueva Bay, which is located nearby a growing urban population, whereas the lowest values were detected in the center of the gulf. Holoplankton dominated at all stations and evidenced a homogeneous spatial distribution. Meroplankton showed a more heterogeneous pattern. Ctenocalanus vanus was the most abundant taxon followed by Paracalanus parvus . Gastropoda veligers dominated the meroplanktonic fraction. Our results showed that the spatial distribution of the mesozooplankton seemed to be mainly influenced by the dominant hydrological circulation pattern of the region. This research establishes the first scientific basis for further studies in zooplankton communities of this important gulf, closely related to a natural protected worldwide known area declared a world heritage site by UNESCO.

Estuarine mesozooplankton dynamics on a short-term time scale: role of semidiurnal tidal cycle

Wageningen University Hydrology and Quantitative Water Management, Environmental Sciences Group (Atlas, Droevendaalsesteeg 4, 6708 PB, Wageningen, The Netherlands) Descriptors: Mesozooplankton, Acartia tonsa , Tidal variability, Estuaries, Argentina. Descritores: Mesozooplancton, Acartia tonsa , Ciclo de marea, Estuario, Argentina. In estuaries and coastal areas, planktonic organisms are subject to tidal, diurnal and seasonal environmental changes (MARQUES et al., 2009). Knowledge of the variability of zooplankton communities on different spatial and temporal scales is a prerequisite for the understanding of ecosystem dynamics. Tidal currents and estuarine circulation are well known phenomena that contribute to both vertical and horizontal redistribution of planktonic organisms (MORGADO et al., 2003. Moreover, biological mechanisms may also account for a significant part of the temporal variation in zooplankton community structure (MARQUES et al., 2009). Planktonic communities have presumably developed adaptations in order to compensate for or resist dispersive losses (LAM-HOAI et al., 2006), thus resulting in recurrent patterns of zooplankton distribution. The Bahia Blanca Estuary constitutes a mesotidal system with a semidiurnal tidal cycle, the tides being one of the most important sources of energy (PERILLO; PICCOLO, 1991). The temporal and spatial dynamics of the mesozooplankton in this estuary have been extensively investigated (e.g. HOFFMEYER 2004; HOFFMEYER et al., 2008) but none of these studies has considered the short-term variability associated with tidal cycles. The objectives of the present study were to describe the influence of the tidal cycle on mesozooplankton variability and to compare the mesozooplankton distribution of two zones in the main channel of the estuary: its northern margin and the deeper central zone. The Bahia Blanca Estuary is a coastal plain system (38°45´S; 62°22´W) on the Atlantic coast of Argentina (Fig. 1). It is formed by several NW to SE tidal channels separated by extensive intertidal flats, low marshes and islands (PICCOLO; PERILLO, 1990). The tides and winds have been considered the main factors controlling the water turbulence processes (PICCOLO; PERILLO, 1990), especially in the inner zone where the tidal height is maximal (tidal range of up to 3.6 m). Tidal currents are reversible with maximum surface velocities of about 1.3 m s

Seasonal and Tidal Dynamics of Water Temperature, Salinity, Chlorophyll-a, Suspended Particulate Matter, Particulate Organic Matter, and Zooplankton Abundance in a Shallow, Mixed Estuary (Bahía Blanca, Argentina)

ABSTRACT Menéndez, M.C.; Delgado, A.L.; Berasategui, A.A.; Piccolo, M.C., and Hoffmeyer, M.S., 2016. Seasonal and tidal dynamics of water temperature, salinity, chlorophyll-a, suspended particulate matter, particulate organic matter, and zooplankton abundance in a shallow, mixed estuary (Bahía Blanca, Argentina). Estuaries are characterized by a variety of interrelated, abiotic and biotic, structural components and intensive physical, chemical, and biological processes. The aim of this study was to investigate the seasonal- and tidal-mediated variability in water temperature, salinity, suspended particulate matter (SPM), particulate organic matter (POM), chlorophyll-a (Chl-a), and zooplankton abundance in the Bahía Blanca estuary, Argentina. The underlying mechanisms responsible for the observed variability are also discussed. Sampling was carried out every two months (December 2004–April 2006) during 14-h tidal cycles in a fixed station located in the inner zone of the estuary. Vertical profiles of temperature and salinity and water samples were obtained at the surface and the bottom to determine SPM, POM, Chl-a, and zooplankton. SPM (97.3 ± 6.9 mg L−1) showed a strong seasonality, mainly attributed to biological activity. POM concentration (1539 ± 107.6 mgC m−1) was high, possibly derived from vascular plants and benthic microalgae. Chl-a (6.91 ± 0.73 mg m−3) and zooplankton (2024.23 ± 9.16 individuals m−3) also showed a seasonal pattern, with higher concentrations in the summer. During the tidal cycle, the highest amounts of the measured variables were observed during the ebb tide. The results highlight the strong variability in the physicochemical and biological variables at different time scales in mesotidal, temperate estuaries. It is essential to take into account this variability in any monitoring program performed in a temperate system dominated by such a tidal regime.

Hydrography of the Inner Continental Shelf along the Southwest Buenos Aires Province, Argentina: Influence of an Estuarine Plume on Coastal Waters

ABSTRACT Delgado, A.L.; Menéndez, M.C.; Piccolo, M.C., and Perillo, G.M.E., 2017. Hydrography of the inner continental shelf along the southwest Buenos Aires Province, Argentina: Influence of an estuarine plume on coastal waters. Estuarine plumes have a significant influence on the characteristics and biology of the adjacent inner shelf. In the sector occupied by the plume, several transformations occur to the sediment and nutrients exported from the continent to the oceans. The coastal zone of Pehuén Co (PC) and Monte Hermoso (MH) is located in a highly complex oceanographic and ecological regional system, which creates the basis of one of the most valuable Argentinean habitats for fishing of commercial species. In this work, the physical oceanographic characteristics of the inner shelf of the southwest Buenos Aires Province and the influence of the Bahia Blanca estuarine (BBE) waters are introduced. The in situ data obtained from oceanographic cruises included vertical profiles of water temperature, salinity, and turbidity. The spatial variability of the parameters was studied with a multivariate statistical analysis. Temperature and salinity presented high seasonal variability (6.1–22.9°C; 33.5–36, respectively). Maximum turbidity occurred throughout the summer (64 nephelometric turbidity units [NTU]) and showed a minimum during spring (24 NTU). The study area was characterized by a significant spatial variability, especially in terms of salinity and turbidity, while water temperature showed a more homogeneous pattern. Salinity and turbidity values decreased from PC (closer to BBE) to MH (further from BBE) stations, with the highest values located near the mouth of the BBE. The PC and MH (to a lesser extent) inner shelves are transitional environments between the estuary and the open beaches of Buenos Aires Province, creating a habitat where benthic and zooplankton estuarine and marine species are found.

Heavy Metal Concentrations Found in Seston and Microplankton from an Impacted Temperate Shallow Estuary along the Southwestern Atlantic Ocean

ABSTRACT Fernández Severini, M.D.; Villagran, D.M.; Biancalana, F.; Berasategui, A.A.; Spetter, C.V.; Tartara, M.N.; Menéndez, M.C.; Guinder, V.A., and Marcovecchio, J.E., 2017. Heavy metal concentrations found in seston and microplankton from an impacted temperate shallow estuary along the southwestern Atlantic Ocean. Heavy metal concentrations (Cd, Cu, Cr, Fe, Mn, Ni, Pb, and Zn) were studied in the Bahía Blanca Estuary (BBE), one of the most anthropogenically disturbed estuaries in the SW Atlantic Ocean. This study evaluated metal concentrations in the microplankton and seston for the first time, as well as their role in the transport of contaminants in a disturbed coastal environment of the SW Atlantic. Spatial patterns of metals in suspended particulate matter (SPM; seston > 0.45 μm) and microplankton (20–200 μm) were analyzed at sampling sites located at sewage or industrial discharges and, also far from this area, during warm months in 2012 and 2013. Dissolved inorganic nutrients, particulate organic matter (POM), and chlorophyll a (Chl-a) were also analyzed. The POM and Chl-a concentrations were higher near to the sewage discharges; however, metals showed different concentrations between sampling site stations. Those located far from human disturbances showed similar levels to the sites at the sewage or industrial discharges in some cases. In general, the SPM had higher concentrations of metals than the microplankton. In particular, Cr presented important levels in this fraction, which was potentially associated with industrial discharges. On the other hand, a contrasting partition was found for Pb, Zn, and Cu that exhibited higher levels in the microplankton-net material. The high levels of Pb in the microplankton of the BBE may indicate a high availability of this metal in the environment and high uptake rates, with potential health risks to humans and marine life attributable to its toxic effects.