Appendicularians and marine snow in situ vertical distribution in Argentinean Patagonia

Detailed in situ vertical and temporal distribution of appendicularians, marine snow, fecal pellets, nano- and microplankton were recorded simultaneously with environmental data in the San Jorge Gulf, Argentinean Patagonia (45°-47°S). Data were taken at a fixed station over 36 h in February 2014 with an autonomous Video Plankton Recorder and a FlowCAM®. The water column was thermally stratified with a pycnocline at ~ 40 m. Appendicularians dominated in the upper 65 m with a condensed pattern above the pycnocline at high chlorophyll a concentrations, matching the subsurface chlorophyll maximum layer at ~ 20 m. Our results suggest the absence of vertical migration of appendicularians. Marine snow, strongly correlated with appendicularians, showed high concentrations above the pycnocline, whereas fecal pellets from krill were distributed throughout the water column. Discarded houses of appendicularians or their mucus fragments were the main components of marine snow aggregates, with phytoplankton, detritus and krill pellets also contributing. Nanoplankton dominated over microplankton, with vertical distribution patterns that might depend on local grazing pressure and advective processes. Our study, the first one in the region using underwater imagery, emphasizes the leading contribution of appendicularians to marine snow aggregates in the San Jorge Gulf and their potential implications in the bentho-pelagic coupling.Fil: Giménez, Eloísa Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Nocera, Ariadna Celina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: 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. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: Winkler, Gesche. Institut des Sciences de la Mer de Rimouski; Canad

Contemporary Diet of Bowhead Whales (Balaena mysticetus) from the Eastern Canadian Arctic Inferred from Fatty Acid Biomarkers

The diet and feeding ecology of Eastern Canada – West Greenland bowhead whales were examined using fatty acid (FA) composition of the outer blubber layer of 50 individuals sampled during the summers of 2008 and 2009. Bowhead blubber was rich in the following FAs: 14:0, 16:0, 16:1n – 7, 18:0, 18:1n – 11, 18:1n – 9, 18:1n – 7, 20:1n – 11, 20:1n – 9, 20:1n – 7, 20:5n – 3, 22:1n – 11, 22:1n – 9, 22:5n – 3, and 22:6n – 3, which together accounted for 91% of total FAs identified. Four groups of bowhead whales were identified from their FA signatures using multivariate analysis. Long-chain monounsaturated fatty acids (MUFAs) (20:1n – 9, 20:1n – 11, 22:1n – 9 and 22:1n – 11) and polyunsaturated fatty acids (PUFAs) (20:5n – 3, 22:5n – 3, 22:6n – 3) accounted for most of the variance among groups. Whales from a single sampling site segregated into different groups, some of which included whales from other sampling sites, suggesting summer mixing of whales from different wintering areas and prey assemblages, or alternatively, selective feeding. FA composition was similar in males and females and among whales of different age classes, which suggests that these different groups shared foraging areas and had similar diets. The blubber of bowhead whales from the eastern Canadian Arctic was composed of high proportions of calanoid copepod markers (20:1n – 9 and 22:1n – 11), especially compared to the adipose tissue of western Arctic bowhead whales. This finding suggests that Calanus spp. were likely a major prey item. Given the expected change in Arctic zooplankton assemblages with climate warming, bowhead whales, through their FA biomarkers, may serve as sentinels of change in Arctic ecosystems.Afin d’approfondir les connaissances sur la diète et l’écologie alimentaire de la baleine boréale de la population EC-WG, nous avons examiné la composition en acides gras de la couche de graisse sous-cutanée de 50 animaux échantil­lonnés durant les étés 2008 et 2009. Les baleines boréales étaient riches en certains acides gras (AG) notamment 14:0, 16:0, 16:1n-7, 18:0, 18:1n-11, 18:1n-9, 18:1n-7, 20:1n-11, 20:1n-9, 20:1n-7, 20:5n-3, 22:1n-11, 22:1n-9, 22:5n-3 et 22:6n-3. Ces 15 acides gras constituaient 91 % de tous les acides gras identifiés. Nous avons identifié quatre groupes de baleines à l’aide d’une analyse composée principale dans une analyse de fonction discriminante. Les acides gras monoinsaturés à longue chaîne (MUFAs) (20:1n-9, 20:1n-11, 22:1n-9 et 22:1n-11) et les acides gras Oméga-3 polyinsaturés (PUFAs) (20:5n-3, 22:5n-3 et 22:6n3) étaient responsables de la majorité de la variance entre les groupes de baleines. Chacun des quatre groupes de baleines était constitué d’animaux provenant d’une même région ainsi que de régions différentes. Ces résultats suggèrent que des baleines boréales avec des sites d’hivernage différents partagent un même site d’alimentation estival et/ou que les baleines boréales ont une alimentation sélective. La composition en acide gras du tissu adipeux était semblable chez les mâles et les femelles ainsi qu’entre les individus de différentes classes de tailles, ce qui suggère une diète similaire ou des aires d’alimentation communes. Le tissu adipeux des baleines boréales de l’Arctique de l’Est canadien était constitué d’une plus grande proportion de marqueurs spécifiques de copépodes calanoides (20:1n – 9 et 22:1n – 11) comparativement aux baleines boréales de l’Arctique de l’Ouest. Les résultats de notre étude suggèrent que Calanus spp. est une proie importante de la diète des baleines boréales de la population de l’est du Canada et de l’ouest du Groenland. Compte tenu de l’évolution attendue dans les assemblages de zooplancton de l’Arctique en raison du réchauffement climatique, les baleines boréales, par leurs biomarqueurs AG, peuvent servir de sentinelles des changements dans les écosystèmes.

Anthropogenic boat noise reduces feeding success in winter flounder larvae (Pseudopleuronectes americanus)

The aim of this study was to explore an emerging discipline addressing the impact of anthropogenic noise on larval stages of marine organisms. We assessed the influence of boat noise on the feeding behaviour of the pelagic larvae of winter flounder (Pseudopleuronectes americanus, Walbaum, 1792). The hypothesis was that boat noise influences the feeding behaviour of P. americanus flounder larvae independently of prey density. Aquaria containing P. americanus larvae were placed in water baths in which boat noise was diffused for the “noise” treatment and compared to control aquaria with no sound emissions. Larvae were filmed using cameras placed above the aquaria and their behaviour was recorded. Larvae exposed to anthropogenic noise displayed significantly fewer hunting events than controls, and their stomach volumes were significantly smaller. This noise effect was the same at all prey densities used, suggesting that larval feeding behaviour is negatively impaired by anthropogenic noise. Keywords : Feeding behaviour ; Winter flounder ; Larvae ; Anthropogenic noise ; Vessel noise

La diversité, la répartition et l’écologie du complexe d’espèces cryptiques Euytemora affinis, dans la zone d’alevinage de l’estuaire moyen du Saint-Laurent

Le copépode calanoïde Eurytemora affinis est un complexe d’espèces clés des réseaux trophiques estuariens. En dominant les communautés planctoniques dans la plupart des estuaires de l’hémisphère nord, E. affinis permet un transfert d’énergies vers les niveaux trophiques supérieurs. Il influence directement le recrutement des espèces de poissons et constitue une espèce clé des zones d’alevinage. E. affinis est en réalité un complexe d’espèces cryptiques composé de 6 clades morphologiquement similaires, mais possédant des histoires évolutives distinctes. Dans la zone de transition estuarienne du Saint-Laurent, 2 clades (Atlantique et Nord-Atlantique) sympatriques, spatialement ségrégués, dominent la communauté zooplanctonique. Chacun des 2 clades semble exploiter différents types d’habitats en fonction de sa tolérance physiologique à la salinité et à la disponibilité de nourriture. Nous discuterons des études récentes en mettant l’accent sur la répartition, la différenciation génétique, mais aussi l’écologique de ces espèces du complexe d’E. affinis afin de mieux comprendre leurs influences respectives sur le fonctionnement et la productivité de l’écosystème unique que représente la zone d’alevinage de l’estuaire du Saint-Laurent.The calanoid copepod Eurytemora affinis is a cryptic species complex composed of 6 genetically distinct but morphologically similar clades. These dominate planktonic communities, and are considered the keystone species of many estuarine food webs in the northern hemisphere, channeling carbon and energy to higher trophic levels. In doing so, they directly influence the recruitment of many fish species. The Atlantic and the North-Atlantic clades co-occur in the St. Lawrence estuarine transition zone (Québec, Canada), but their distribution is spatially segregated. Both clades exploit various habitats depending on their physiological tolerance to salinity and resource availability favouring niche partitioning. In this review, we discuss recent studies on E. affinis, focussing on distribution patterns, and the ecological and genetic differentiation of co-occurring clades. The aim is to provide a clearer understanding of the influence of this species complex on productivity and ecosystem functioning in the St. Lawrence estuarine transition zone, which is an important fish nursery

Effects of salinity, temperature and individual variability on the reproduction of Eurytemora affinis (Copepoda; Calanoida) from the Seine estuary: A laboratory study

International audienc

La comunidad zooplanctónica del Golfo San Jorge (Patagonia Argentina): composición, distribución espacial y estructura trófica

El objetivo del presente estudio fue investigar la composición, la distribución espacial en relación con los factores ambientales y las relaciones tróficas de la comunidad zooplanctónica (mediante la técnica de isótopos estables) en el Golfo San Jorge (GSJ) durante el verano austral. EL GSJ representa una zona de gran importancia económica debido a la presencia de especies zooplanctófagas de interés comercial. Además, es una zona propicia para la explotación petrolera, de importancia turística y contiene en el sector norte al Parque Interjurisdiccional Marino Costero Patagonia Austral. Esta investigación forma parte del proyecto multidisciplinario MARES (MArine ecosystem health of the San Jorge Gulf: Present status and RESilience capacity), enmarcado dentro de "Pampa Azul". El muestreo se realizó en Febrero de 2014 en 14 estaciones distribuidas en toda la extensión del GSJ. La estructura de la comunidad zooplanctónica estuvo fuertemente relacionada con la temperatura de superficie y la estratificación de la columna de agua. Dos ensambles zooplanctónicos, coincidentes con las características físico-químicas de la columna de agua, fueron definidos en el GSJ: 1) zona norte/centro, dominado por Ctenocalanus vanus, copepoditos de C. vanus, Clausocalanus brevipes y Paracalanus parvus, Oikopleura sp. y Oithona helgolandica; y 2) zona sur, dominado por P. parvus, copepoditos, Acartia tonsa y Drepanopus forcipatus. La estructura trófica mostró un enriquecimiento en 13C del zooplancton y un incremento de los niveles tróficos de norte a sur. Las grandes variaciones en los valores de d13C del zooplancton encontrados dentro de cada zona del GSJ refleja la utilización de una amplia variedad de recursos alimenticios entre los taxa. En el norte y centro, las apendicularias estuvieron en la base de la red trófica y los quetognatos ocuparon la posición más alta. En el sur, esa posición fue ocupada por A. tonsa.Fil: Ferreyra, Gustavo Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Giménez, Eloísa Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Winkler, Gesche. Institut des Sciences de la Mer de 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; ArgentinaX Jornadas Nacionales de Ciencias del MarCiudad Autónoma de Buenos AiresArgentinaUniversidad de Buenos Aires. Facultad de Ciencias Exactas y Naturale

Life Cycle Traits of Two Transatlantic Populations of Eurytemora affinis (Copepoda: Calanoida): Salinity effects.

International audienceWhile the populations of the copepod Eurytemora affinis are often morphologically (i.e. taxonomy) indistinguishable, the species complex is composed of genetically distinct clades, representing divergent evolutionary histories. The most distant clades, genetically and morphologically (i.e. phylogeny), are transatlantic clades: North American and European (Lee, 2000). The study of the life cycle strategies of two populations from St. Lawrence salt-marshes (Canada) and from the Seine estuary (France) at three salinities (5, 15 and 25) revealed differences in their salinity tolerance. Individuals from the Seine exhibited high mortality under the highest salinity suggesting that the St. Lawrence population tolerated a wider salinity range. At the lowest salinity, the development time of St. Lawrence individuals was longer than that of individuals from the Seine suggesting that the Seine population was more adapted to low salinity. The clutch size and the longevity of St. Lawrence adults were on average two times higher compared to Seine adults. Thus, the St. Lawrence population exhibited a higher fitness relative to the Seine population. Such differences could be due to genetic differences resulting from divergent evolutionary history, to phenotypic plasticity and/or to the acclimation to culture conditions. We confirmed that a gamma density function is an appropriate fitting function for copepod development time, based on a large data set on development time. It can therefore be integrated into individual-based models of copepod population dynamics

A first glimpse of larval ecology of halibut species in the Gulf of St. Lawrence, Canada

Knowledge of the larval ecology of winter-spawning fish from the Estuary and Gulf of St. Lawrence, Canada, remains scarce due to the seasonal ice cover that prevents ichthyoplankton sampling using conventional methods. Two winter-spawning species, Atlantic halibut (AH, Hippoglossus hippoglossus) and Greenland halibut (GH, Reinhardtius hippoglossoides), support the most important groundfish fisheries of this area. In March 2020, the authors captured 10 halibut larvae ranging in size from 5 to 14 mm during an opportunistic survey in the GSL onboard an icebreaking vessel. Of these, eight were AH and two GH. Judging by their very small size, the larvae were only a few days old, suggesting that the spawning grounds are close to the capture sites. This effort constitutes a first step in validating the putative spawning areas for these two important GSL stocks. This knowledge is important for the conservation and sustainable management of these fisheries. -- Keywords : Atlantic halibut ; Greenland halibut ; larval distribution ; larval ecology ; spawning ground ; winter ecology