Effects of food concentration on egg production and feeding rates of the cyclopoid copepod Oithona davisae

12 pages, 7 figures, 3 tablesExperiments to determine egg production and feeding rates of Oithona davisae were carried out under controlled laboratory conditions. From copepodite IV stage on, the animals were fed the heterotrophic dinoflagellate Oxyrrhis marina in a wide range of concentrations (from 10 µg C L−1to 286 µg C L−1), and adult females were daily monitored to study different aspects of their fecundity. Both clutch and egg-production rate increased with food concentration, with values from 8 to 20 eggs for the clutch size, and from 1.8 eggs to 6.3 eggs female−1 d−1 for the egg production. In addition, to assess the efficiency of conversion of food intake into egg mass, two feeding experiments were conducted. Maximum weight-specific ingestion rates (≈ 80% body C d−1) and the egg-production efficiency (16%) were lower than those reported for free-spawning calanoid copepods. The fact that satiating food concentrations for feeding and egg production of adult females of Oithona davisae were rather low suggests an adaptation to exploit oligotrophic environments, and might explain the ecological success of the genus in situations when food becomes limiting for other groups of copepodsThis work was funded by the Spanish Ministry of Education and Science (current Ministry of Economy and Competitiveness) through a Ph.D. fellowship (BES-2008-004231) to S. Z. and the research project CTM2007-60052 and CTM2011-23480 to E.S. This is a contribution of the Marine Zooplankton Ecology Group (2009SGR-1283) at the Institut de Ciències del Mar. We thank M. Antó and P. Jiménez for taking care of the stock cultures of algae and copepods. We also thank R. Almeda, A. Calbet, and M. Alcaraz for their advice. We finally thank M. R. Landry and two anonymous reviewers for their constructive comments on the manuscriptPeer reviewe

Copepod feeding in the ocean: Scaling patterns, composition of their diet and the bias of estimates due to microzooplankton grazing during incubations

16 pages, 9 figures, 1 table, electronic supplementary material in https://doi.org/10.1007/s10750-010-0421-6Here, we report insights from the compilation and analysis of data on marine calanoid copepod feeding rates in the ocean. Our study shows that food availability and body weight are major factors shaping copepod feeding rates in the field, with a relatively minor role of temperature. Although the maximal feeding rates of copepods that are observed in the field agree with the well-known 3/4 of body size scaling rule for animals, copepod feeding in the oceans is typically limited and departs from this rule. Ciliates and dinoflagellates appear to be highly relevant in the composition of copepod diets, and this represents an indirect increase in the flux of primary production that is likely to reach the upper trophic levels; this contribution is higher in the less productive systems and may help to explain accounts of proportionally higher standing stocks of copepods supported per unit of primary producer biomass in oligotrophic environments. Contrary to common belief, diatoms emerge from our dataset as small contributors to the diet of copepods, except in some very productive ecosystems. We have also evaluated the bias in the estimation of copepod grazing rates due to within-bottle trophic cascade effects caused by the removal of microheterotrophs by copepods. This release of microzooplankton grazing pressure accounts for a relevant, but moderate, increase in copepod grazing estimates (ca. 20-30%); this bias has an effect on both the carbon flux budgets through copepods and on our view of their diet composition. However, caution is recommended against the indiscriminate use of corrections because they may turn out to be overestimates of the bias. We advise that both uncorrected and corrected grazing rates should be provided in future studies, as they probably correspond to the lower and upper boundaries of the true grazing rates. © 2010 Springer Science+Business Media B.V.This study was supported by project OITHONA (CTM2007-60052) from the Spanish Ministry of Education and SciencePeer Reviewe

External energy and plankton: New insights on the role of small-scale turbulence on zooplankton ecology

Some of the already known effects of small scale turbulence on zooplankton populations maintained in laboratory rnicrocosms (higher development rates, changes in the demographic composition of populations, higher ammonia concentration) seemed to be a cons.equence of increased energy expenditure driven by behavioural changes. Higher frequency of escape reactions and fast swimming in copepods could be the main reasons for it, although direct measurements of metabolic rates under turbulence were not available. Here we discuss the effects of small scale turbulence on two parameters directly related to metabolic activity: heart-beat rate on pond cladocerans, and NH4-N and P04-P excretion rates on marine copepods

Feeding behaviour of the nauplii of the marine calanoid copepod Paracartia grani Sars : Functional response, prey size spectrum, and effects of the presence of alternative prey

Laboratory feeding experiments were conducted to study the functional response and prey size spectrum of the young naupliar stages of the calanoid copepod Paracartia grani Sars. Experiments were conducted on a range of microalgal prey of varying sizes and motility patterns. Significant feeding was found in all prey of a size range of 4.5-19.8 mu m, with Holling type III functional responses observed for most prey types. The highest clearance rates occurred when nauplii fed on the dinoflagellate Heterocapsa sp. and the diatom Thalassiosira weissflogii (respectively, 0.61 and 0.70 mL ind(-1) d(-1)), suggesting an optimal prey: predator ratio of 0.09. Additional experiments were conducted to examine the effects of the presence of alternative prey (either Heterocapsa sp. or Gymnodinium litoralis) on the functional response to the haptophyte Isochrysis galbana. In the bialgal mixtures, clearance and ingestion rates of I. galbana along the range of the functional response were significantly reduced as a result of selectivity towards the larger, alternative prey. Paradoxically, relatively large prey trigger a perception response in the nauplii, but most likely such prey cannot be completely ingested and a certain degree of sloppy feeding may occur. Our results are further evidence of the complex prey-specific feeding interactions that are likely to occur in natural assemblages with several available prey types.Peer reviewe

Sensory capabilities and food capture of two small copepods, Paracalanus parvus and Pseudocalanus sp.

10 pages, 7 figuraes, 3 tablesDetection, handling, and selection of prey are key features of suspension-feeding copepods. Using high-speed video, we determined detection distances and durations of all elements of the food gathering process in two small calanoid copepods, Paracalanus parvus and Pseudocalanus sp. Animals were freely swimming and presented with various phytoplankton species with equivalent spherical diameters ranging from 7 µm to 33 µm. Prey detection occurred very close—within a few cell radii—to the second antennae (53% of the cases) or the maxilliped (42%). There was no effect of prey size on detection distance, but larger prey caused a significantly longer handling time. Post-detection processing of the cells was exceedingly fast. The time from detection to the cell being placed at the mouth lasted 35 ± 19 ms and rejection of unwanted cells 61 ± 21 ms. Grooming of antennules and carapace occurred intermittently and lasted 215–227 ms. The weak feeding current and fast response of the copepods allowed ample time for detection of cells entrained in the feeding current and no distant olfaction was observed. Modeled effect of cell size on cell surface concentration of cue chemicals show that only cells with a radius larger than ∼ 15 µm may be detected chemically and that only very much larger and/or very leaky cells can be detected at distance. Copepods have elaborate and exceedingly fast handling techniques that allow effective prey detection and capture, but there is no evidence of remote chemically mediated sensing when feeding on algal cells up to a size of 35 µmThis is a contribution to the Baltic Zooplankton Cascades (BAZOOCA) project funded by the Baltic Organizations Network for funding Science (BONUS), the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS; project 210-2008-1882 to PT), the Danish Council for Independent Research (10-085278 to TK), and the Spanish Ministry of Economy and Competitiveness (CTM2011-23480 to ES)Peer reviewe

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

The effect of short-term temperature exposure on vital physiological processes of mixoplankton and protozooplankton

Sudden environmental changes like marine heatwaves will become more intense and frequent in the future. Understanding the physiological responses of mixoplankton and protozooplankton, key members of marine food webs, to temperature is crucial. Here, we studied two dinoflagellates (one protozoo- and one mixoplanktonic), two ciliates (one protozoo- and one mixoplanktonic), and two cryptophytes. We report the acute (24 h) responses on growth and grazing to a range of temperatures (5–34 °C). We also determined respiration and photosynthetic rates for the four grazers within 6 °C of warming. The thermal performance curves showed that, in general, ciliates have higher optimal temperatures than dinoflagellates and that protozooplankton is better adapted to warming than mixoplankton. Our results confirmed that warmer temperatures decrease the cellular volumes of all species. Q10 coefficients suggest that grazing is the rate that increases the most in response to temperature in protozooplankton. Yet, in mixoplankton, grazing decreased in warmer temperatures, whereas photosynthesis increased. Therefore, we suggest that the Metabolic Theory of Ecology should reassess mixoplankton's position for the correct parameterisation of future climate change models. Future studies should also address the multigenerational response to temperature changes, to confirm whether mixoplankton become more phototrophic than phagotrophic in a warming scenario after adaptation

Non-lethal effects of the predator Meganyctiphanes norvegica and influence of seasonal photoperiod and food availability on the diel feeding behaviour of the copepod Centropages typicus

Predators can induce changes in the diel activity patterns of marine copepods. Besides vertical migration, diel feeding rhythms have been suggested as an antipredator phenotypic response. We conducted experiments to assess the non-lethal direct effects of the predator Meganyctiphanes norvegica (northern krill) on the diel feeding patterns of the calanoid copepod Centropages typicus. We also analysed the influence of seasonal photoperiod and prey availability on the intensity of copepod feeding rhythms. We did not detect any large effect of krill presence on the diel feeding behaviour of copepods, either in day-night differences or total daily ingestions. Seasonal photoperiod and prey availability, however, significantly affected the magnitude of copepod feeding cycles, with larger diel differences in shorter days and at lower prey concentrations. Therefore, the role of non-lethal direct effects of predators on the diel feeding activity of marine copepods remain debatable and might not be as relevant as in freshwater zooplankton

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