Seasonal and spatial variability in condition of age-0+ Argentine hake Merluccius hubbsi Marini, 1933, in the San Jorge Gulf (Argentina): A bottom-up perspective

In the north Patagonian region of the Argentinean Continental Shelf, the San Jorge Gulf (SJG; 45°‐47°S, 65°30ʹ‐67°30ʹW) is the main nursery ground of age‐0+ Argentine hake Merluccius hubbsi Marini, 1933, one of the most important fishery resources in Argentina. The gulf exhibits strong seasonal and spatial fluctuations in environmental features, which might affect survival of age‐0+ individuals and recruitment to the adult population. Our main goal was to evaluate the seasonal and spatial dynamics of their nutritional status within the SJG in winter 2016, spring 2016 and summer 2017. Condition indices (relative condition factor Kn, hepatosomatic index HSI and liver lipid content %L) and diet information (feeding incidence and relative importance of prey) were combined with physical (temperature and salinity) and biological (satellite chlorophyll‐a concentration; chl‐a) data. Age‐0+ condition indices and prey intake showed significant seasonal variations, with minimum values in winter, intermediate in summer and maximum in spring, strongly coupled to the mean chl‐a concentration in each season. Herbivorous euphausiids Euphausia spp. were the preferred prey along the study period. A bottom‐up effect on condition of age‐0+ hake is suggested, manifested as lower condition values in winter, the less productive season. Spatially, better conditioned individuals matched sectors of the gulf where chl‐a concentrations were higher, coupled to the presence of frontal systems. Monitoring age‐0+ hake nutritional status is relevant in the current global change scenario, which might modify phytoplankton biomass and composition and, consequently, the herbivorous zooplankton abundances.Fil: Temperoni, Brenda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Subsede Instituto Nacional de Investigación y Desarrollo Pesquero; Argentina. 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 Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Massa, Agueda Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Subsede Instituto Nacional de Investigación y Desarrollo Pesquero; Argentina. 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 Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Martos, Patricia. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Marinas; ArgentinaFil: Marrari, Marina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Perspectives of marine biodiversity studies in Argentina

This paper provides an overview of the research being carried out at the moment by a group of Argentinean scientists working on the subjects of marine biodiversity and oceanography. When the idea of the Census of Marine Life (CoML)was proposed following the Symposium held during the IAPSO-IABO conference in Mar del Plata in October 2001, there was a wide response from the marine scientific community. Information about current research projects, as well as plans for future work in the context of the CoML, were then obtained from about 70 scientists (Appendix I) belonging to 12 institutions located along the Argentinean coast (Appendix II, Figure 1). This has been used to illustrate what is currently being pursued in marine biodiversity in Argentina and which subjects are considered as priority for future research in the area. This paper is, thus, not an historical update of the knowledge of marine biodiversity, but it attempts to give an idea of the current situation and what is planned for the future. The development of an extensive database of what is known on marine biodiversity in the region is considered to be a necessity, but it constitutes a complete project on its own; as such it is included in the proposals for future work (see Future Work in this paper). It is emphasised that this synthesis is not exhaustive in the content of the topics being studied or in the number of researchers working in marine biodiversity in the country. It is, though, considered to be a representative sample of the knowledge in marine science in Argentina today. This is a starting point for the CoML project in South America and it is hoped that, as it develops, it will be improved by the active participation, advice and experience of many other scientists in the region

HAB-MAPS of toxic marine microalgae in the `Cono Sur¿ of South America

Geo-referenced distributions of potentially toxic microalgal species in coastal and shelf waters of South America have been created as part of the HAB-MAP project of the International Society for the Study of Harmful Algae (ISSHA). A total of 40 potentially toxic species - 9 diatoms, 23 dinoflagellates, 3 haptophytes and 5 raphidophytes - were recorded. The total number of toxic species could be greater than the apparent one because of dubious taxonomic identifications of some taxa, and low frequency of sampling in large areas of South AmericaVersión del edito

Pigment profile and toxin composition during a red tide of Gymnodinium catenatum Graham and Myrionecta rubra (Lohman) Jankowski in coastal waters off Mar del Plata, Argentina

Microscope observations of samples, collected in autumn 2003 during a red tide in the coastal waters of Mar del Plata, Argentina, suggest that the phytoplankton community consisted mainly of the chain-formingdinoflagellate Gymnodinium catenatum (89 000 cells l.1). However, the unusually high concentration of chlorophyll a (171ƒÊg l.1) and the relative abundance of alloxanthin (73%) among the carotenoid pigments measured by high-performance liquid chromatography (HPLC)indicated that cryptophyceans predominated in these samples. Re-examination of Lugolfs preserved plankton samples under high magnification revealed the presence of a low number of recognisable individuals of the ciliate Myrionecta rubra, together with a high abundanceof cytoplasmic contents of their broken cells. Analysis of toxin composition of these samples by HPLC with fluorescence detection showed that, as in most of the G. catenatum strains reported from different geographicalorigins, the toxin profile was dominated (82%) by the less potent N-sulfocarbamoyl toxins. However, the toxin profile of the studied G. catenatum population exhibited certain atypical aspects: it contained the toxins C1,2, GTX4, GTX2,3 and dcGTX2,3, while lacking GTX5, GTX6, C3, C4 and the recently described hydroxybenzoate saxitoxin analogues GC1.3. The toxin profile of this population differed from thosereported for Uruguayan strains, despite their geographic proximity. These results suggest that the observed G. catenatum bloom was a local event, which was not directly related to the transport of an establishedpopulation from the estuarine region of the Rio de la Plata. No harmful effects attributable to this red tide were observed on the Mar del Plata coast

Phytoplankton types and primary production in the Argentine Sea

Several satellite models classify phytoplankton functional types (PFT) based on cell size. In this study we used field data from the Argentine Sea on both the photosynthetic and the bio-optical properties of phytoplankton to distinguish photosynthetic and bio-optical phytoplankton types (PBPT). Cluster analyses were run using data from 70 stations sampled during 3 periods to distinguish different PBPT, and principal component analysis was used to describe them. We examined the main taxonomic composition and percentage of chl a in the <5 μm size fraction found within the PBPT. The distribution of PBPT in relation to hourly primary production and environmental conditions was also investigated. The results showed a high degree of variability in biooptical and photosynthetic properties, e.g. the specific absorption coefficient of phytoplankton, aB ph(440), varied between 0.015 and 0.067 m2 (mg chl a)-1, and the maximum production at light saturation, PB m, varied between 0.68 and 10.05 mg C (mg chl a)-1 h-1. This resulted in the discrimination of 11 PBPT. Some had similar average cell sizes but differed in their bio-optical or photosynthetic characteristics, e.g. PBPT1 (with diatoms <5 μm and Emiliania huxleyi 2-5 μm) and PBPT6 (with diatoms <5 μm and coccal cells ∼2 μm) had markedly different PB m values (PBPT1: 1.20 mg C (mg chl a)-1 h-1 and PBPT6: 6.71 mg C (mg chl a)-1 h-1). This variability in the bio-optical and physiological properties is most likely the result of adaptation by phytoplankton communities to the high heterogeneity in environmental conditions in this region. These results indicate that satellite models describing the distribution of PFT based on cell size alone will not provide a realistic representation of the phytoplankton composition in this highly productive and heterogeneous area. © 2013 The authors.Fil:Dogliotti, A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Akselman, R. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

FEEDING AND REPRODUCTIVE ACTIVITY OF THE COPEPODS Drepanopus forcipatus AND Calanus australis DURING LATE SUMMER ON THE SOUTHERN PATAGONIAN SHELF (ARGENTINA, 47&#176;-55&#176;S)

Drepanopus forcipatus and Calanus australis are key planktonic copepods on the southern Patagonian shelf. Their feeding and reproductive patterns and population status were investigated during late summer, when environmental conditions may be critical. The presence of food in the gut and food-pellet length were recorded in adult females and the most abundant copepodite stages. Diet composition was also studied in adult females. Female reproductive status was evaluated by gonad staging. Despite generally low feeding conditions and decreasing seasonal temperature, both copepods fed to some degree. The most numerous copepodites and adult females of both species showed similarly low feeding activity. About half of the adult females of the two species and C5s of C. australis contained food in their guts, but the proportion of fed C4-females of D. forcipatus was much lower. All copepods were generally feeding at low or intermediate levels. Gonad stage distribution and population structure showed low but still ongoing reproduction in both species. Gut content findings suggest a preference for smaller nanoplanktonic particles, especially dinoflagellates by D. forcipatus, and for autotrophic prey, particularly large diatoms by C. australis. The feeding and reproduction patterns of the two copepods were likely influenced by the distributions of potential food resources and temperature

Phytoplankton and protozooplankton on the southern Patagonian shelf (Argentina, 47°–55°S) in late summer: Potentially toxic species and community assemblage structure linked to environmental features

On the southern Patagonian shelf (Argentina, 47°–55°S) phyto- and protozooplankton are key structural and functional components of a complex trophic web that sustains commercially important species. During late summer 2004, spatial structure, assemblage species and their association with environmental characteristics of water masses were studied for the 2–200 μm phyto- and protozooplankton communities. Ultraplankton 2–5 μm was the most abundant size-fraction (90%), followed by the lower nanoplankton 5–10 μm (7.5%), the larger nanoplankton 10–20 μm (1.5%), and microplankton 20–200 μm (1%). Several of the 319 morpho-species found are potentially toxic taxa (the dinoflagellates Alexandrium tamarense, Protoceratium reticulatum, Dinophysis acuminata, Prorocentrum cordatum, Karenia and amphidomataceans and the diatom genus Pseudo-nitzschia), and this is important since the area sustains significant fisheries. A ultraphytoeukaryotic coccal cell (probably chlorophyte/prasinophyte) (3 μm), P. cordatum, and a microplankton naked ciliate were the morpho-species with the highest abundance and occurrence. Abundance and biodiversity patterns indicated that the plankton community structure was heterogeneous vertically, cross-shelf, and along-shelf, suggesting shifts in community structure over the region. Five areas with dissimilar plankton assemblages were defined, each corresponding to different environments. Depth, bathymetry, latitude and temperature were the most explanatory variables for the assemblage distribution patterns observed. This south Patagonian region possesses important fisheries and, considering expected environmental changes, our results help to understand the spatial structure of plankton communities over a broad size spectrum.Fil: Antacli, Julieta Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Silva, Ricardo L. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: Jaureguizar, Andrés 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: Hernández, Daniel R. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: Mendiolar, Manuela. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: Sabatini, Marina Elena. 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 Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Akselman, Rut. Instituto Nacional de Investigaciones y Desarrollo Pesquero; Argentin