Agrupaciones de larvas de peces en aguas costeras de la zona central de Grecia: reflejo de la heterogeneidad en la topografía y la oceanografía

Patterns in the mesoscale distribution of larval fish in the coastal waters of central Greece, an area of high topographic and bathymetric complexity, were analysed using samples collected during two ichthyoplankton surveys in July 1998 and June 1999. Salinities were lower in the eastern (Aegean) part of the study area due to the influence of waters originating from the Black Sea. In this region, larvae of many epipelagic and benthopelagic (typically summer spawning) species were less abundant in June 1999, when waters were significantly cooler, compared to July 1998. Multivariate analyses identified ‘neritic’ and ‘pelagic’ groups of stations dominated by larvae of epipelagic/bethopelagic (typically shelf dwelling) and mesopelagic species. In the west (Ionian Sea), a prominent third group of stations located in the deep and highly enclosed Korinthiakos Gulf was also defined with very high abundances of mesopelagic fish larvae. However, the genera Cyclothone and Vinciguerria that dominated the neighbouring offshore assemblage of the Ionian Sea were absent from this gulf. In the study area, Korinthiakós Gulf ( > 900 m) and North Evoikos ( > 400 m) Gulf comprise unique ‘fjord-like’ ecosystems in the Mediterranean with increased productivity and significantly cooler deep waters compared to adjacent open sea basins.Se analizaron los patrones de distribución de mesoescala de larvas de peces en aguas costeras de Grecia central (un área de alta complejidad topográfica y batimétrica) mediante el estudio de muestras recogidas en el transcurso de dos muestreos de ictioplancton (julio de 1998 y junio de 1999). En la zona este del área de estudio (mar Egeo), las salinidades fueron menores debido a la influencia de aguas procedentes del mar Negro. En esta región, las larvas de muchas especies epipelágicas y bentopelágicas (normalmente de desove en verano) fueron menos abundantes en junio de 1999, cuando las aguas eran significativamente más frías, en comparación con julio de 1998. Un análisis multivariante identificó los grupos ‘nerítico’ y ‘pelágico’ en las estaciones dominadas por larvas de especies epipelágicas/betopelágicas (típicas de plataforma) y mesopelágicas. En el oeste (mar Jónico) se definió un tercer grupo de estaciones con altas abundancias de larvas de peces mesopelágicos ubicadas en el Golfo Korinthiakós, zona muy profunda y cerrada. Sin embargo, los géneros Cyclothone y Vinciguerria, que dominaban en la comunidad de aguas abiertas del Mar Jónico, estaban ausentes en este golfo. Dentro del área de estudio, los golfos de Korinthiakós ( > 900 m de profundidad) y el del Norte de Evoikos ( > 400 m) comprenden ecosistemas únicos en el Mediterráneo, semejantes a fiordos, con una productividad elevada y aguas profundas significativamente más frías que las de cuencas adyacentes del mar abierto

Copepod performance under CO2-induced acidification: the case of Acartia grani and Oithona davisae

11th Panhellenic Symposium on Oceanography and Fisheries, Aquatic Horizons : Challenges & Perspectives, 13-17 May 2015, Mytilene, Lesvos island, Greece.-- 11ο Πανελλήνιο Συμπόσιο Ωκεανογραφίας & Αλιείας, Μυτιλήνη, Λέσβος, Ελλάδα.-- 4 pagesThis experimental study aimed to evaluate the direct impact of two distinct pH levels, one “Control” (pHNBS: 8.17) and one “Low pH” (pHNBS: 7.75) on the feeding, respiration and reproductive output of two marine copepods: the calanoid Acartia graniand the cyclopoid Oithonadavisae. Adult copepods collected from laboratory cultures were preconditioned for 4 consecutive days at a dinoflagellate suspension (Akashiwo sanguinea) prepared with filtered sea water preadjusted at the targeted pH values via CO2 bubbling. Water acidification had no direct effect on the examined vital rates for any of the two copepod species. Our results lend support to the generally observed lack of direct influence of the seawater pH decrease projected at the end of the century on the group of copepodsThis work was supported by the project CROA (LS8-1893), implemented within the framework of the «Supporting Postdoctoral Researchers» Action of the >Education and Lifelong Learning> Operational Program (Action’s Beneficiary: General Secretariat for Research and Technology), and was cofinanced by the European Social Fund (ESF) and the Greek StatePeer Reviewe

Variabilidad de la biomasa del zooplankton y de su tamaño individual en un transecto costa-alta mar en el ar Catalán: relaciones con la clorofila a y las estructuras hidrográficas

The temporal and spatial changes of zooplankton and chlorophyll a concentration were studied during the warm stratification period (early June) at three stations whose traits corresponded to the coastal, frontal, and offshore-dome water conditions described for the Catalan Sea. We sampled the stations for 12 days at a frequency ranging from less than 10 to 102 h, with a spatial resolution ranging from 10 to 104 m. The objective was to determine the variability of mesozooplankton and phytoplankton (chlorophyll a) biomass, and average individual size (mass) across a coast-offshore transect in relation to the stratification conditions prevailing in the NW Mediterranean during summer. The vertical distribution of phytoplankton biomass displayed a clear deep maximum at 60 m depth except at the coastal station. This maximum exists during most of the year and is especially important during the density stratification period. It was accompanied during daylight hours by a coherent zooplankton maximum. At sunset mesozooplankton ascended and dispersed, with larger organisms from deeper layers joining the migrating community and increasing the average individual mass. The highest variability of mesozooplankton biomass, individual mass and chlorophyll a concentration occurred at the front station due to the coupling between the vertical migration of zooplankton and the particular characteristics of the front. According to the data shown, the highest variability was observed at the lowest scales.Durante el periodo de estratificación térmica (principios de junio) se estudiaron los cambios temporales y espaciales de concentración de zooplancton y clorofila a en tres estaciones cuyos rasgos corresponden a las condiciones de aguas costeras, frontal y domo central descritas para el Mar Catalán. Muestreamos las estaciones a lo largo de 12 días con una frecuencia que varió entre 10 h y 102 h, y con una resolución espacial entre 10 y 104 m. El objetivo fue determinar la variabilidad de la biomasa del fitoplancton (clorofila a) y del mesozooplancton, así como de su tamaño individual promedio a lo largo de un transecto costa-mar abierto en relación con las condiciones de estratificación térmica típicas del Mediterráneo del Noroccidental desde finales de primavera a finales de verano. La distribución vertical de la biomasa de fitoplancton mostró la existencia de un máximo profundo a 60 m de profundidad, excepto en la estación costera. Aunque cierta heterogeneidad vertical en la biomasa de fitoplancton suele observarse durante la mayor parte del año, es especialmente importante durante el período de estratificación de densidad. El máximo de fitoplancton estuvo acompañado durante las horas de luz por un máximo de zooplancton, que en la crepúsculo ascendía y se dispersaba, y al que se unían organismos de mayor tamaño procedentes de zonas más profundas, contribuyendo a aumentar la masa individual promedio. La mayor variabilidad de biomasa mesozooplanctónica, de la masa individual y de la concentración de clorofila a se observó en la estación frontal debido al acoplamiento entre la migración vertical del zooplancton y las características particulares del frente. Según los datos presentados la mayor variabilidad fue observada en las escalas espaciales y temporales más bajas

Asynchronized spawning responses of small pelaigic fish to a short-term enviromental change

We provide substantial evidence on how short-term changes in environmental conditions activate and deactivate spawning activities in small pelagic fishes. An ichthyoplankton survey was conducted along the southernmost part of the Canary Current upwelling ecosystem in May 2013, covering the area twice within 20 d. This period coincided with a strong environmental change from a cold productive upwelling regime to a warmer and less productive upwelling relaxation event. This change triggered a shift in spawning activity from European anchovy Engraulis encrasicolus to round/flat sardinella Sardinella spp. We used zero-altered negative binomial regression models with a generalized additive structure based on integrated nested Laplace approximations to link early larval distribution patterns to the 2 different regimes. The models confirmed 2 species-specific temperature spawning windows, suggesting a spawning pause of anchovy during upwelling relaxation while simultaneously activating spawning in sardinella. Observing immediate spawning responses to the 2 environmental regimes underlines the assumption that windows of spawning opportunity are the main drivers of small pelagic fish fluctuations in upwelling regions. The duration of a specific environmental condition can, therefore, increase or decrease the chances for reproductive success. The observations of this study may explain why certain small pelagic fish species can dominate over others during a particular period and might also apply to other upwelling regions of the world oceans where upwelling and relaxation events alternate.publishedVersio

Mapping of Fish Spawning in the North Sea; Report of the “KINO-2” Project for 2019

Increased and updated knowledge of reproductive strategies of fish is crucial to optimize the temporal and spatial planning for conducting seismic surveys; in order to reduce its potential negative ecosystems impacts. The overall goal of this study is to improve our general knowledge about spawning areas of major North Sea fish stocks, including their spawning behavior and spawning period. This report describes the methodology, preliminary results and experiences gained during the data sampling period August 2017 to December 2019. Molecular barcode and traditional visual taxonomic analyses were performed on eggs and larvae, systematically collected with plankton nets along a south to north axis in the North Sea. In total, 201 samples have been analysed from which 35 different fish taxa are identified. Based on historic data and previously published literature, our results agree with the expected number of the most prevalent fish species breeding in the North Sea. Both the taxonomic and molecular methods used, demonstrate robust and similar results in the identification of taxonomic groups. The results further demonstrate that the molecular taxonomic approach is more appropriate for identification to species levels for most taxonomic groups, whilst the identification of egg and larvae developmental stages can only be performed using the visual taxonomic method. The two techniques have the potential of complementing each other to provide a detailed description of the annual fish spawning cycle for the main North Sea species. Our results demonstrate that the fish species diversity increase northwards, but here the spawning season is more concentrated. We have also identified new species spawning in the area, traditionally found more to the south or west of our study area. To improve the spatial and temporal statistical data resolution required for achieving sufficient scientific evidence as basis for producing robust advice in timing of seismic surveys, modifications to the sampling protocol and equipment was made during 2019. Expectantly, this potential proves to work over the coming annual reproduction cycle. Our study also confirms that the study area represents a highly dynamic environment, thus we strongly recommend considering extending the time period for data collection, beyond what is planned so far (due out August 2020) and an expansion of the geographical coverage to include regions also further north and west.publishedVersio

Ageing and Caloric Restriction in a Marine Planktonic Copepod

10 pages, 5 figures, 2 tables, supplementary information http://dx.doi.org/10.1038/srep14962.--This study is a contribution of the Marine Zooplankton Ecology Group (2014SGR-498) at the Institut de Ciències del Mar-CSICPlanktonic copepods are a key group in the marine pelagic ecosystem, linking primary production with upper trophic levels. Their abundance and population dynamics are constrained by the life history tradeoffs associated with resource availability, reproduction and predation pressure. The tradeoffs associated with the ageing process and its underlying biological mechanisms are, however, poorly known. Our study shows that ageing in copepods involves a deterioration of their vital rates and a rise in mortality associated with an increase in oxidative damage (lipid peroxidation); the activity of the cell-repair enzymatic machinery also increases with age. This increase in oxidative damage is associated with an increase in the relative content of the fatty acid 22:6(n-3), an essential component of cell membranes that increases their susceptibility to peroxidation. Moreover, we show that caloric (food) restriction in marine copepods reduces their age-specific mortality rates, and extends the lifespan of females and their reproductive period. Given the overall low production of the oceans, this can be a strategy, at least in certain copepod species, to enhance their chances to reproduce in a nutritionally dilute, temporally and spatially patchy environmentThis research was funded by projects CTM2011-23480 and CGL2014-59227-R of the Spanish Ministry of Economy and Competitiveness (cofinanced with FEDER funds, EU)Peer Reviewe

Mapping of fish spawning in the North Sea — Report of the KINO-2 project for 2018

Increased and updated knowledge of reproductive strategies of fish is crucial to optimize the temporal and spatial planning for conducting seismic surveys; in order to reduce its potential negative ecosystems impacts. The overarching goal of this study is to investigate the current spawning times and locations for the North Sea fish stocks. Molecular barcode and traditional visual taxonomic analyses were performed on eggs and larvae, systematically collected with plankton nets along a south to north axis in the North Sea. This report describes the establishments of methodology employed and preliminary results based on samples collected during August 2017 to September 2018. In total, 129 samples have been analysed from which 22 different fish taxa are identified. Based on historic data and published literature, our results agree with the expected number of the most prevalent fish species breeding in the North Sea. Both the taxonomic and molecular methods used, demonstrate similar results in the identification of taxonomic groups. The results further demonstrate that the molecular taxonomic approach is more appropriate for identification to species levels for some taxonomic groups, whilst the identification of egg and larvae developmental stages can only be performed using the visual taxonomic method. The two techniques complement each other to provide a detailed description of the annual fish spawning cycle for the main North Sea species. There are already emerging patterns evident in the results on the timing for breeding in some species at certain areas. However, improvements of the sampling methodology are still required, and an increased number of samples collected systematically over an extended time-period must be accomplished in order to provide appropriate data as basis for advice in timing of seismic surveys.publishedVersio

Copepod Foraging on the Basis of Food Nutritional Quality: Can Copepods Really Choose?

12 pages, 5 figures, 1 table, supporting information in https://doi.org/10.1371/journal.pone.0084742Copepods have been considered capable of selective feeding based on several factors (i.e., prey size, toxicity, and motility). However, their selective feeding behaviour as a function of food quality remains poorly understood, despite the potential impact of such a process on copepod fitness and trophodynamics. In this study, we aimed to evaluate the ability of copepods to feed selectively according to the nutritional value of the prey. We investigated the feeding performance of the calanoid copepod Acartia grani under nutritionally distinct diets of the dinoflagellate Heterocapsa sp. (nutrient-replete, N-depleted and P-depleted) using unialgal suspensions and mixtures of prey (nutrient-replete vs. nutrient-depleted). Despite the distinct cell elemental composition among algal treatments (e.g., C:N:P molar ratios) and the clear dietary impact on egg production rates (generally higher number of eggs under a nutrient-replete diet), no impact on copepod feeding rates was observed. All unialgal suspensions were cleared at similar rates, and this pattern was independent of food concentration. When the prey were offered as mixtures, we did not detect selective behaviour in either the N-limitation (nutrient-replete vs. N-depleted Heterocapsa cells) or P-limitation (nutrient-replete vs. P-depleted Heterocapsa cells) experiments. The lack of selectivity observed in the current study contrasts with previous observations, in which stronger nutritional differences were tested. Under normal natural circumstances, nutritional differences in natural prey assemblages might not be sufficiently strong to trigger a selective response in copepods based on that factor alone. In addition, our results suggest that nutritional quality might depend not only on the growing conditions but also on the inherent taxonomical properties of the prey. © 2013 Isari et al.This is a contribution from the Marine Zooplankton Ecology Group (2009SGR-1283) at the Institut de Ciències del MarPeer Reviewe