Morphological types and seasonal variation in eggs of zooplankton species from bottom sediments in Bahia Blanca Estuary, Argentina

Resting egg production is a survival mechanism in zooplankton species against adverse environmental conditions. Egg accumulation in the upper layer of the bottom sediments is fundamental to the resurgence of the populations of these species when conditions become more favourable. Rotifers, such as Synchaeta sp. and planktonic copepods such as Acartia tonsa and Eurytemora americana are commonly found in Bahía Blanca Estuary and they produce resting eggs. We studied eggs isolated from samples of bottom sediments obtained from two sites located within the inner part of Bahía Blanca Estuary (Cuatreros Port and Ing. White Port). The aims of our work were to describe the morphological types of eggs found in bottom sediments; to try to identify to which species they belong; to corroborate the identity of some of them by means of incubations; and to determine either the spatial or seasonal presence of morphological types according to the sampling site. Sediment samples were collected from Cuatreros Port on a monthly basis from January to December 2003 and samples from Ing. White Port were collected from the area close to the industrial zone only in April 2004. All samples were treated following the sugar flotation method of Onbé. The eggs were observed under stereomicroscope and light microscope. Besides, incubation experiments with eggs were sometimes carried out. Five morphological types of eggs (type A, B, C, D and E) were found in the sediments from Cuatreros Port whereas three types of eggs were found at Ing. White Port (F, G and H). Of the 8 morphological types of eggs found in this study, only those of the rotifer Synchaeta sp. in Cuatreros Port and the copepod A. tonsa in the two sampling sites were confirmed to be respectively diapausal and “delayed -hatching”. As regards the seasonal variation of the eggs found in the sediments from Cuatreros Port and the active forms of the populations of Synchaeta sp. and A. tonsa, our study confirms the presence of eggs in the sediment either in periods of time during which no active forms have been previously reported in the plankton or in periods of time during which only some active forms have been reported at very low densities. Concerning the spatial variation at Ing.White Port, the differences in the presence of eggs across the sampling areas may be due to sediment modifications produced by anthropic impact, where industrial effluents are discharged.Fil: Diodato, Soledad Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Berasategui, Anabela Anhi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Hoffmeyer, Monica Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Tecnológica Nacional; Argentin

Composition, Spatial Distribution, and Trophic Structure of the Zooplankton Community in San Jorge Gulf, Southwestern Atlantic Ocean

The goal of this study was to understand the zooplankton community composition and food web structure in San Jorge Gulf (45°–47°S, 65°30'W), a highly productive marine ecosystem in southern Argentina. A spatial grid of 14 stations was sampled in 2014. The sampled zooplankton community was composed of 30 taxa, with copepods accounting for 83% of the total abundance. Community composition was strongly related to surface temperature and water column stratification. Two distinct zooplankton assemblages were present. The zones designated North and Center were dominated by Ctenocalanus vanus; copepodite stages of C. vanus, Clausocalanus brevipes, and Paracalanus parvus; appendicularians; and Oithona helgolandica. The South zone was dominated by P. parvus, copepodites, Acartia tonsa, and Drepanopus forcipatus. The plankton food webs were increasingly enriched in carbon and nitrogen stable isotopes from the North to the South. Depleted δ 13 C signatures in the North may be explained by terrigenous inputs derived from strong westerly winds. The zooplankton taxa displayed a wide feeding range in the North, whereas the narrow trophic space of the South food web suggested similar feeding strategies among the taxa. Appendicularians were positioned at the base of the food webs, copepods were in the middle, and chaetognaths occupied high trophic positions.Fil: Giménez, Eloísa Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Institut des Sciences de la Mer de Rimouski; CanadáFil: Winkler, Glescher. Institut des Sciences de la Mer de Rimouski; Canadá. Université du Québec à Rimouski; CanadáFil: Hoffmeyer, Monica Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Ferreyra, Gustavo Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Institut des Sciences de la Mer de Rimouski; Canadá. Université du Québec à Rimouski; Canad

Tidal effects on short-term mesozooplankton distribution in small channels of a temperate-turbid estuary, Southwestern Atlantic

The short-term variability of mesozooplanktondistribution and physicochemical variables wasexamined in two different channels of the BahíaBlanca Estuary, Argentina, during two tidalcycles. All the physicochemical measurementsand mesozooplankton sampling were performedat a fixed site during approximately 22-23 h at3-h intervals. Pumps were used to obtain surfaceand bottom mesozooplankton samples and thewater speed of each stratum was measured withan Acoustic Doppler Current Profiler (ADCP). Inall, 23 mesozooplanktonic taxa belonging to fourphyla (Arthropoda, Annelida, Echinodermata andChordata) were identified. The most abundant taxaduring the two tidal cycles were Balanus glandulalarvae, Eurytemora americana and Acartia tonsa.A discernible variability in the water conditionsand vertical mesozooplankton distribution (VMD)different from that known for the estuary´s mainchannel, was found in the other two selectedchannels. VMD varied during the tidal cycle inboth channels in accordance with the channel?sgeomorphology and water dynamic characteristicsof each of them. The variation of the abundance ofthe different taxa during ebb and flood currents mightindicate the existence of a tidal vertical migrationof the mesozooplankton as a response to particulardynamic water conditions.A variação de curto prazo da distribuição do mesozooplâncton e das variáveis físico-químicas foi examinada em dois diferentes canais do Estuário de Bahia Blanca, Argentina, durante dois ciclos de maré. As medidas físico-químicas e a amostragem do zooplâncton foram realizadas em dois locais fixos durante aproximadamente 22-23 horas, com intervalos de 3 horas. Bombas foram utilizadas para obter amostras de zooplâncton na superfície e no fundo e a velocidade da água em cada estrato foi medida com o Perfilador Acústico de Corrente (ADCP). Ao todo, foram identificados 23 taxa mesozooplanctônicos pertencentes a 4 filos (Arthropoda, Annelida, Echinodermata e Chordata). Os grupos mais abundantes durante os dois ciclos de maré foram larvas de Balanus glandula, além de Eurytemora americana e Acartia tonsa. Nos dois canais selecionados foi identificada uma variação nas condições da água e na distribuição vertical do mesozooplâncton (DVZ) diferente daquela conhecida para o canal principal do estuário. DVZ variou durante o ciclo de maré em ambos os canais de acordo com a geomorfologia e características da dinâmica das águas existente em cada um deles. A variação na abundância dos diferentes taxa durante as marés vazante e enchente poderia estar indicando a existência de migração vertical do mesozooplâncton em resposta a uma determinada condição dinâmica da água.Fil: Chazarretta, Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto Argentino de Oceanografía (i); ArgentinaFil: Hoffmeyer, Monica Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto Argentino de Oceanografía (i); ArgentinaFil: Cuadrado, Diana Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto Argentino de Oceanografía (i); ArgentinaFil: Berasategui, Anabela Anhi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto Argentino de Oceanografía (i); Argentin

Medusae and ctenophores from the Bahia Blanca Estuary and neighboring inner shelf (Southwest Atlantic Ocean, Argentina)

An updated checklist of medusae and ctenophores is presented for the first time for the area comprised by the Bahía Blanca Estuary, the adjacent shelf El Rincón and Monte Hermoso beach, on the southwest coast of Buenos Aires province (Argentina). The area is highly productive and provides several ecosystem services including fishing and tourism. Updated information on the biodiversity of medusae and ctenophores species is essential for the study area, given that these species can affect ecosystem services. The list includes 23 hydromedusae, 3 scyphomedusae, and 3 ctenophores. Five hydromedusae (Halitiara formosa, Amphinema dinema, Aequorea forskalea, Clytia lomae and Halopsis ocellata) were firstly observed in this area. Three species of medusae, 2 hydromedusae (Olindias sambaquiensis and Liriope tetraphylla) and 1 scyphomedusae (Chrysaora lactea) pose a potential health risk, due to their toxicity to humans. Considering the size of the study area, the Bahía Blanca region has a comparatively high species richness of hydromedusae, higher than larger zones previously studied along the temperate SW Atlantic Ocean. The present report provides the baseline knowledge of gelatinous species for the Bahía Blanca region.Fil: Dutto, María Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Genzano, Gabriel Nestor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Schiariti, Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: Lecanda, Maria Julieta. Museo Municipal de Ciencias Naturales de Monte Hermoso; Argentina. Universidad Nacional del Sur; ArgentinaFil: Hoffmeyer, Monica Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Tecnológica Nacional; ArgentinaFil: Pratolongo, Paula Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; Argentin

The planktonic ciliate community and its relationship with the environmental conditions and water quality in two bays of the Beagle Channel, Argentina

The relationship between the ciliate community and the environmental variables in Ushuaia and Golondrina bays (54º79′S 68º22′W and 54º85′S 68º36′W, respectively) in the Beagle Channel, Argentina was investigated. The study was performed inthree zones within the bays, previously delimited on the basis of their water quality. The most perturbed sites were located inshore. In order to analyse the contribution of each species to the similarity or dissimilarity between zones, similarity percentages analysis was undertaken using the Bray-Curtis similarity index. The variations in species composition and dominance in the selected zones were examined by the abundance–biomass comparison plot. We also studied the relationship between environmental and ciliates variability. The ciliate community comprised a total of 43 species belonging to 15 genera. Ciliate abundance and biomass varied temporally and spatially. A more diverse community dominated by small and opportunistic species tolerant to environmental changes was found in the most perturbed zone, while in the less stressed zone the community comprised bigger species, probably adapted to more stable environmental conditions. A community comprising species from both zones was found in a transitional area. We conclude that the structure of the community varied closely with environmental conditions.Fil: Barria, Maria Sonia. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto Argentino de Oceanografía (i); ArgentinaFil: López Abbate, María Celeste. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahia Blanca. Instituto Argentino de Oceanografia (i); ArgentinaFil: Pettigrosso, R. E. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; ArgentinaFil: Hoffmeyer, Monica Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto Argentino de Oceanografía (i); Argentina. Universidad Tecnológica Nacional. Facultad Regional Bahía Blanca; Argentin

Micro- and mesozooplankton successions in an Antarctic coastal environment during a warm year

The rapid increase in atmospheric temperature detected in the last decades in the Western Antarctic Peninsula was accompanied by a strong glacier retreat and an increase in production of melting water, as well as changes in the sea-ice dynamic. The objective of this study was to analyze the succession of micro- and mesozooplankton during a warm annual cycle (December 2010-December 2011) in an Antarctic coastal environment (Potter Cove). The biomass of zooplankton body size classes was used to predict predator-prey size relationships (i.e., to test bottom-up/top-down control effects) using a Multiple Linear Regression Analysis. The micro- and mesozooplanktonic successions were graphically analyzed to detect the influence of environmental periods (defined by the degree of glacial melting, sea-ice freezing and sea-ice melting) on coupling/uncoupling planktonic biomass curves associated to possible predator-prey size relationship scenarios. At the beginning of the glacial melting, medium and large mesozooplankton (calanoid copepods, Euphausia superba, and Salpa thompsoni) exert a top-down control on Chl-a and microzooplankton. Stratification of the water column benefitted the availability of adequate food-size (Chl-a <20) for large microzooplankton (tintinnids) development observed during fall. High abundance of omnivores mesozooplankton (Oithona similis and furcilia of E. superba) during sea-ice freezing periods would be due to the presence of available heterotrophic food under or within the sea ice. Finally, the increase in microzooplankton abundance in the middle of spring, when sea-ice melting starts, corresponded to small and medium dinoflagellates and ciliates species, which were possibly part of the biota of sea ice. If glacier retreat continues and the duration and thickness of the sea ice layer fluctuates as predicted by climate models, our results predict a future scenario regarding the zooplankton succession in Antarctic coastal environments.Fil: Garcia, Maximiliano Darío. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Dutto, María Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Chazarreta, Carlo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Berasategui, Anabela Anhi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Schloss, Irene Ruth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Ministerio de Relaciones Exteriores y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino. Departamento de Biología Costera; Argentina. Universidad Nacional de Tierra del Fuego; ArgentinaFil: Hoffmeyer, Monica Susana. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina. Universidad Tecnológica Nacional. Facultad Regional Bahía Blanca; Argentin

¿El Mesozooplancton controla al fitoplancton y cianobacterias en el Embalse Paso de las Piedras?

Resulta relevante investigar ecológicamente el embalse Paso de las Piedras no sólo por su valor como reservorio de agua para consumo humano sino también para analizar estrategias que resuelvan/aminoren las proliferaciones de cianobacterias que alteran la calidad del agua. En este estudio se evaluó la interacción trófica entre el mesozooplancton y el fitoplancton - cianobacterias en términos de biomasa, con datos de 8 muestreos de un ciclo anual. Se realizaron correlaciones entre variables ambientales y bióticas. Estos primeros resultados sugieren que el mesozooplancton controla al fitoplancton y cianobacterias a través de su presión de pastoreo desde la primavera hasta fines del verano. Sin embargo, se requieren más estudios para corroborar estos resultados y además para estudiar el efecto del pastoreo de distintos grupos de edad de Odontesthes bonariensis sobre las especies del mesozooplancton presentes en el lago.Fil: Fritz, Laura Jesica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Estrada, Vanina Gisela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Di Maggio, Jimena Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Díaz, María Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Hoffmeyer, Monica Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaX Congreso de Ecología y Manejo de Ecosistemas Acuáticos PampeanosAzulArgentinaUniversidad Nacional del Centro de la Provincia de Buenos Aires Facultad de Ciencias Exacta

Decadal change in zooplankton seasonal succession in the Bahía Blanca estuary, Argentina, following introduction of two zooplankton species

Seasonal zooplankton succession (mainly of the mesozooplankton) in the inner zone of Bahı ́a Blanca estuary during the period 1990–1991 was compared to that from the period 1979–1980 in order to detect changes having taken place in 10 years. Taxonomic composition, zooplankton abundance, species occurrence and temperature–salinity conditions were studied within the two annual cycles. This estuarine ecosystem has been deeply affected by a population increase and by the rapid growth of industrial activity and maritime traffic over the last two decades. Several changes in the zooplankton assemblage composition and structure were detected, probably due to temperature– salinity gradient patterns, which showed discernible differences. Dominance, during winter–spring, of two new invading species, namely, the cirriped Balanus glandula and the copepod Eurytemora americana, causing a decrease in the autochthonous key copepod Acartia tonsa, was one of the principal features of the period 1990–1991. Seasonal changes in diversity and species richness, as well as differences in the multivariate general pattern of the zooplankton community structure with a consequent decrease in the community stability during the second period, were also observed.Fil: Hoffmeyer, Monica Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentin

Water quality and zooplankton monitoring at the seawater circuit of a mollusk hatchery

Seawater quality in mollusc hatcheries has been identified as one topic of high concern because of its implications in larval performance. This aspect, however, has received little or no attention from the scientific point of view. The only literature about this topic is a general compilation about water quality for aquaculture systems (Anonymous 1977). This gap in the available information may be mainly that periodic adjustments performed in hatcheries are routine protocols, the results of which are filed as internal reports and seldom reach the scientific literature. Research done on this subject has dealt primarily with water quality and the composition of effluents from hatcheries and other aquaculture systems and their potential reuse for other purposes, such as agriculture and he culture of secondary aquatic organisms (Van Rijn 1996, Lin et al. 2002) There have also been studies associated with the effects of different treatments of seawater aimed at improving the quality of bivalve larvae (Utting et al. 1983, Chen 1984, Jaeckle and Manahan 1989). Our study was triggered by the occasional finding of different types of plankton, mainly copepod microcrustaens, in the water used for larval culture in a mollusc hatchery. The assessment of water quality and biota throughout the entire water circuit was undertaken to improve the intake system and the treatment methods employed in conjunction with the water that circulates within the hatchery. This study is the first of its kind performed in Argentina. We present here the results of a survey performed during a year in the hatchery during which water quality was monitored with regard to its physical and chemical properties, including temperature, salinity, pigments, organic matter. Planktonic species richness and total abundance, species abundance and the presence of non-planktonic organisms were also assessedFil: Hoffmeyer, Monica Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Pascual, Marcela. Universidad Nacional del Comahue. Instituto de Biologia Marina y Pesquera Almirante Storni; Argentin