Knowing the determinants of the geographic ranges of parasites is important for understanding their evolutionary ecology, epidemiology and their potential to expand their range. Here we explore the determinants of geographic range in the peculiar case of a parasite species – the microsporidian Hamiltosporidium tvaerminnensis – that has a limited geographic distribution in a wide-spread host – Daphnia magna. We conducted a quantitative trait loci (QTLs) analysis with monoclonal F2D. magna populations originating from a cross between a susceptible northern European genotype and a resistant central European genotype. Contrary to our expectations, long-term persistence turned out to be a quantitative trait across the F2 offspring. Evidence for two QTLs, one epistatic interaction and for further minor QTL was found. This finding contrasts markedly with the previously described bimodal pattern for long-term parasite persistence in natural host genotypes across Europe and leaves open the question of how a quantitative genetic trait could determine the disjunct geographic distribution of the parasite across Europe.

Although Parthenopidae is a brachyuran decapod family comprising almost 140 species, there is little knowledge about its larval morphology. There are only two complete larval developments reared in the laboratory and some larval stages described for seven species. In the present work these data are compared and analysed. A summary is made of the larval features that characterize parthenopids that can be used to distinguish them from other brachyuran larvae. In addition, the megalopa stage of Derilambrus angulifrons and Parthenopoides massena was collected from plankton and identified by DNA barcodes. The morphology of the megalopa of D. angulifrons is described for the first time, and that of P. massena is compared with a previous description.

Hyperiid amphipods are holoplanktonic marine crustaceans that are known as temporary symbionts of different groups of gelatinous zooplankton. The nature and dynamics of these associations are still poorly understood, particularly in deep waters. The mesopelagic and deep-living planktonic fauna off Monterey Bay, California (down to 4000 m) was surveyed using a remotely operated submersible (ROV) and blue-water diving (BWD) between September 2005 and January 2008. In this work we report our observations on a total of 51 symbiotic associations observed in situ (not from zooplankton samples), between hyperiid amphipods and various taxa of gelatinous zooplankton. We present the first information on the symbiotic relations of the hyperiid Vibilia caeca, and we provide data of 34 previously unknown symbiotic associations. The host range was expanded for several widely distributed hyperiid species. These findings suggest that the symbiotic associations between hyperiid amphipods and gelatinous zooplankton in deep waters deserve further study worldwide.

Meroplankton community studies in the Antarctic have primarily focused on the coastal waters of both the Antarctic Peninsula and the Ross Sea. The New Zealand International Polar Year - Census of Antarctic Marine Life (IPY-CAML) voyage to the Ross Sea during the late summer (February–March) 2008 provided the first meroplankton samples from three regions in the deep, oceanic waters of the Ross Sea (shelf, slope and adjacent offshore Antarctic waters of Admiralty Seamount and Scott Island). We used a combined morphological and molecular approach to identify 36 larval operational taxonomic units based on sequences from three loci (16S, 18S, COI), and exclude early developmental stages of holoplankton. Overall, larval abundance was lower than previous Antarctic studies (5.19 specimens per 100 m3), with larvae most abundant in the first 200 m of the water column and most diverse in the shelf region. Multivariate analysis revealed significant differences in the meroplankton community between regions and depth ranges, but with low similarity within these groupings; differences between water masses were undetectable due to the confounding effect with both region and depth. The influence of nearby benthic populations (e.g. the acorn barnacle Bathylasma corolliforme) and/or locally abundant taxa (e.g. the nudibranch Tergipes antarcticus) was evident in the meroplankton community.

Graptoloid evolutionary dynamics show a marked contrast from the Ordovician to the Silurian. Subdued extinction and origination rates during the Ordovician give way, during the late Katian, to rates that were highly volatile and of higher mean value through the Silurian, reflecting the significantly shorter lifespan of Silurian species. These patterns are revealed in high-resolution rate curves derived from the CONOP (constrained optimization) scaled and calibrated global composite sequence of 2094 graptoloid species. The end-Ordovician mass depletion was driven primarily by an elevated extinction rate which lasted for c. 1.2 Ma with two main spikes during the Hirnantian. The early Silurian recovery, although initiated by a peak in origination rate, was maintained by a complex interplay of origination and extinction rates, with both rates rising and falling sharply. The global δ13C curve echoes the graptoloid evolutionary rates pattern; the prominent and well-known positive isotope excursions during the Late Ordovician and Silurian lie on or close to times of sharp decline in graptoloid species richness, commonly associated with extinction rate spikes. The graptoloid and isotope data point to a relatively steady marine environment in the Ordovician with mainly background extinction rates, changing during the Katian to a more volatile climatic regime that prevailed through the Silurian, with several sharp extinction episodes triggered by environmental crises. The correlation of graptoloid species diversity with isotopic ratios was positive in the Ordovician and negative in the Silurian, suggesting different causal linkages. Throughout the history of the graptoloid clade all major depletions in species richness except for one were caused by elevated extinction rate rather than decreased origination rate.

In French Polynesia, the black-lip pearl oyster Pinctada margaritifera has been farmed to produce pearls since the 1980s, forming the basis of a major industry. The sustainability of this activity relies on spat collection in the lagoons. However, pearl oyster spat can be difficult to identify for the evaluation of stock variations. It is especially hard to distinguish Pinctada spp. larvae at a very early stage of development. In the present study, a whole-mount in situ hybridisation (ISH) technique was developed to allow the discrimination of larvae of closely-related pearl oyster species found in the French Polynesian atolls. Using specific ribosomal 16S-DNA sequence data, we were able to successfully differentiate between Pinctada margaritifera and Pinctada maculata larvae from 5 to 13 days old. This is the first description of a non-destructive method allowing bivalve larvae discrimination between species within this genus. The method allowed us to successfully identify P. margaritifera larvae in natural plankton samples. This result is a key step needed to develop monitoring of P. margaritifera larval distribution in French Polynesian lagoons, a procedure which will increase spat collection efficiency and ensure sustainable development of pearl oyster farming.

We found viable non-culturable (VNC) Vibrio cholerae O1 attached to the cell envelope of the dinoflagellate Noctiluca scintillans. The significance of this find lies in the fact that N. scintillans could be a reservoir organism of VNC forms of V. cholerae in inter-epidemic periods, particularly when the extensive geographical distribution and the frequently high abundance of this dinoflagellate in marine environments is taken into account.

The lobate ctenophore Mnemiopsis leidyi is a periodically abundant and voracious plankton predator in coastal waters along the east coast of the United States. In the 1980s it was accidentally introduced to the Black Sea where it caused a dramatic reduction in fisheries. We investigated how M. leidyi is affected by infestation with parasitic larvae of the sea anemone Edwardsia lineata. Infested M. leidyi contained 1–30 (median 7) E. lineata larvae. Within M. leidyi most larvae had their mouth in the gastrovascular system near the aboral end of the pharynx. Parasitic E. lineata ingested all food previously ingested and pre-digested by M. leidyi. Non-infested M. leidyi had higher growth rates than infested individuals, which had zero or negative growth rates. Egg production was similar for infested and non-infested M. leidyi of similar size. Simulation based on the empirical data suggests that growing, non-infested, M. leidyi are expected to have a larger life-time egg production than infested shrinking individuals. E. lineata could be at least partially responsible for the sharp decline of M. leidyi populations in fall in US coastal waters. Advantages and disadvantages of E. lineata as a potential candidate for the control of the artificially introduced M. leidyi population in the Black Sea are discussed.

Sampling was carried out in the Celtic Sea in May 1987 over Great Sole and Cockburn Banks, and in June 1991 over Little Sole Bank, to study relationships between bank topography, hydrography and plankton distribution.

Over Great Sole and Cockburn Banks, there were various patterns in the hydrography and plankton which could be related to the banks, although there were no significant correlations with water depth. Away from the shelf-edge, stratification was lower over the banks. Higher water temperatures (at 5 m and 100 m depth) and increased concentrations of copepod nauplii and adults occurred on either side of Cockburn Bank. Abundance of mackerel (Scomber scombrus) eggs and larvae increased towards the shelf-edge, with lower numbers over Cockburn Bank.

Over Little Sole Bank, water column stratification was negatively correlated with water depth. However, this was strongly influenced by shelf-edge mixing, which was reflected in reduced stratification towards the shelf-edge. Background levels of chlorophyll-a also increased from on-shelf towards the shelf-edge. Copepod adults and nauplii, as well as mackerel eggs and larvae were more abundant with distance onto the shelf.

There was partial retention of four Argos tracked drift buoys on the south-east flank of Little Sole Bank. The mean displacement rate of the buoys was 1.35 km day−1 over 10 days, with a mean dispersion of 1.2 km day−1. A simple one-dimensional coupled physical–biological model showed the potential influence of banks resulting in earlier stratification and resultant spring bloom. Considerations of the delay in transfer of production from primary to secondary production and the effects of drift and diffusion, suggested it was unlikely that any influence of the banks on production would be directly related to bank topography, but there might be some regional enhancement of production.

A dichotomous identification key for brachyuran zoeal stages from Peter the Great Bay (Russian waters of the Sea of Japan) is provided for the first time. The key covers 16 taxa identified to species level and uses only the most conspicuous external characters of larvae that are easy to observe under a stereomicroscope without specimens dissection. The key is based on the accounts by various authors and new original descriptions of larvae obtained both from plankton samples and from laboratory culture. Brief descriptions of larvae of 16 brachyuran species are also included.

This contribution reviews the nonlinearstochastic properties of turbulent velocity and passive scalarintermittent fluctuations in Eulerian and Lagrangian turbulence.These properties are illustrated with original data sets of (i)velocity fluctuations collected in the field and in thelaboratory, and (ii) temperature, salinity and in vivofluorescence (a proxy of phytoplankton biomass, i.e. unicelledvegetals passively advected by turbulence) sampled from highlyturbulent coastal waters. The strength of three of the mostpopular models describing intermittent fluctuations (thelognormal, log-Lévy and log-Poisson models) to fit thedistribution of in vivo fluorescence has subsequently beencritically assessed. A theoretical formulation for the stochasticproperties of biologically active scalars is also provided andvalidated. Finally, the potential effect of the intermittentproperties of turbulent velocity fluctuations on processesrelevant to the life of plankton organisms are theoreticallyinvestigated. It is shown that the intermittent nature ofmicroscale turbulence may result in (i) a decrease in the rate ofnutrient fluxes towards non-motile phytoplankton cells (6-62 %),(ii) a decrease in the physical coagulation of phytoplankton cells(25-48 %) and in the subsequent phytoplankton aggregate volumes(22-41 %), and (iii) a decrease of the turbulence contribution topredator-prey encounter rates (25-50 %).

Limited sampling has so far been conducted of the meroplankton community of the high Antarctic, with most research being conducted using vertical hauls in waters > 50 m, and little focused research on the meroplankton community directly under the sea ice (cryopelagic). Here we report the composition of the early summer cryopelagic meroplankton community of the shallow waters of Gerlache Inlet, Terra Nova Bay. A fixed-frame stationary plankton net was deployed c. 1 m below the annual sea ice and sampled at c. 24 hour intervals over a period of 19 days from mid-November to early December 2006. A total of 173 larvae from the phyla Annelida (n = 66), Mollusca (n = 30), Nemertea (n = 4), Echinodermata (n = 8), several Pleuragramma antarcticum (n = 4) and numerous planulae (n = 61) were collected, as well as 265 egg/embryo stages. A mean of 9.1 larvae (SD = 7.3, n = 19) and 13.9 eggs/embryos (SD = 20.5, n = 19) were found directly below the sea ice in each 24 hour period, and these early life history stages may be subject to the hazards of extensive platelet ice and penetrating ultraviolet radiation. The cryopelagic meroplankton community of shallow water is also compositionally similar to that of deeper waters, suggesting that the 50–0 m plankton tows used in previous research are providing a reliable assessment of the biodiversity of coastal Antarctic meroplankton.

The diets of larvae and juveniles (cut-off size: 20 mm) of Limnothrissa miodon (Boulenger) were studied at 2-h intervals during four 24-h cycles (two during the rainy and two during the dry season) in the Bukavu Basin, Lake Kivu. Larvae and juveniles are both diurnal feeders, and they both feed essentially on copepods, which are the most abundant prey in littoral areas, but they show a marked preference for larger organisms (cladocerans), when available. This indicates a rather intense resource sharing, and probable competition between life stages, which is partly solved through spatial behaviour and segregation. During the dry season, when food resources are scarcer, larvae and juveniles make slightly offset inshore migrations during the day, so that they feed at different places, on copepods of different sizes. Because diel migrations are size-structured, it is suggested that cannibalistic pressure (by adults over juveniles, and by juveniles over larvae) may also be a driving factor for these migrations. Plankton samples revealed that there were few cladocerans, while copepods were abundant and their size was similar to that prior to the introduction of L. miodon in Lake Kivu, thereby suggesting that some form of dynamic equilibrium has been reached in the food web.

Seasonal samples of zooplankton were taken during 1997-1999 at fifteen stations in the Salado River basin, and analysed inorder to study the rotifer fauna. Spatio-temporal changes in the rotifer plankton composition were examined in the main channeland its tributaries. The majority of species found are tolerant of a wide range of pH, whereas others prefer neutral to alkalinevalues. The total rotifer plankton density increased downstream from the headwaters to the middle sector of the river. Theassociated shallow lakes and tributaries were an important source of species. Variations in density and number of species wereshown to be associated with conductivity, and species tolerant of high conductivity conditions were especially prevalent (upper7,000 µS cm-1). Rotifer density was influenced by hydrological conditions, which promoted maximum values during low waterperiods and in the high water condition promoted the incorporation of species from shallow lakes connected with the river duringflood events. The species associations found are related to such water parameters as conductivity and nutrient availability andto the presence of ponds and shallow, waterlogged depressions connected in varying extent to the main channel.

Data concerning the planktonic food web and the farmed pearl oysters of the lagoon of Takapoto Atoll were assembled into a steady state model of carbon flows. A method of optimisation, using constraints from the literature, called ‘inverse analysis’ was chosen as the numerical tool for estimating the missing flow values. The resulting food web is characterised by: 1) high primary production, achieved by low phytoplankton biomass, 2) high production of non-living matter, especially as dissolved organic carbon, 3) low bacterial production, 4) zooplankton dominated by protozoa (biomass and processes) and mesozooplankton (processes), and 5) very low consumption of plankton by farmed bivalves compared to planktonic fluxes. When considering the whole lagoon, the farmed oysters (Pinctada margaritifera) and associated bivalves (Pinctada maculata) consume 0.24% of the planktonic gross primary production. In addition, the consumption by natural populations of the main benthic bivalves in this lagoon (Chama iostoma, Arca ventricosa, Pinctada margaritifera and Pinctada maculata) is also low compared to the high planktonic primary production (4.1%). The oyster farming in this lagoon is thus very far from being food-limited.

Empirical models were established, which link the biomasses or productions of the successive planktonic trophic levels in lakes of different depth and trophic status. Published data on 56 lakes were analysed, using both least-square and reduced-major-axis regressions. Reduced-major-axes regression technique was used in order to take into account variability due to both bottom-up and top-down forces. In shallow lakes, the energy transfer efficiency between phytoplankton and zooplankton decreases with increasing trophy. An inverse tendency appears in deep lakes. However, when considering only the oligo- and mesotrophic temperate lakes, the mean primary and secondary productivities per unit of area are about the same in shallow and in deep sites. On the other hand, shallow water bodies are characterized by a smaller mean size of the crustacean species, a lower mean biomass of zooplankton and a higher P zoo/B zoo ratio than deep lakes, probably as a response to the predation by fish. While the consumers seem to have a strong influence on the size structure and biomass of plankton, the energy flows between the trophic levels could be largely controlled by bottom-up forces.

Dans cette note, nous décrivons une méthode simple, permettant l'ultracentrifugation de particules virales planctoniques et leur observation en microscopie électronique à transmission. Une description de différents morphotypes de particules assimilables à des virus est faite à partir d'échantillons prélevés dans la couche euphotique d'un lac eutrophe (Aydat), au cours des périodes printanière et estivale. Ces particules présentent chacune une capside icosaédrique régulière à 6 faces et une queue, dont les dimensions sont similaires à celles des phages décrits en milieu marin. La diversité des formes et le nombre de virions (10 fois supérieur à celui des bactéries), permettent d'émettre l'hypothèse selon laquelle les virus interviennent de façon significative dans le contrôle des abondances des communautés bactériennes en milieu lacustre.

Observations of acoustic images made along a transect perpendicular to the Coast, off Villefranche-sur-Mer, allow one to recognize the hydrological zone corresponding to a surface density gradient characterizing the Ligurian Sea front (Mediterranean Sea). Combinations of statistical and geometrical parameters from the digitized echoes enable discrimination between different classes of patches in relation to the frontal structure during one transect recorded on December 20, 1990. Patch recognition is based on the extraction of the general trend of each column and each row of the digitized data matrix by Eigenvector filtering. Multivariate analysis (principal component analysis and discriminant analysis) run on a 650 patches × 19 variables matrix shows a high negative relation between statistic and geometric parameters of the patches. The two main discriminant parameters are shape and echo strength of patches. From the convergence of our results in the Ligurian front with those of previous works made in other frontal region, it is suggested that this method could be generalized for quantifying and standardizing studies of the patchiness of plankton.

En el presente trabajo se da a conocer la composición específica y la dinámica poblacional de las bacilario fitas halladas en el plancton limnético del Embalse Río III durante tres años y medio de muestreos. De los 32 taxones identificados las poblaciones más numerosas correspondieron a : Aulacoseira granulata, Aulacoseira granulata var. angustissima, Aulacoseira granulata var. angustissima f. spiralis, Aulacoseira lirata var. alpigena, Actinocyclus normanii f. subsalsa y Cymbella affinis. La flora diatomológica hallada en la represa resultó ser alcalófila, eutrófica y oligohalobia. Este grupo algal en reiteradas oportunidades dominó el fitoplancton del embalse generalmente en períodos otoñales y o invernales. La mezcla isotermal es uno de los principales condicionantes del incremento de las poblaciones de diatomeas en el embalse. Sin embargo A. granulata, que fue la bacilariofita más importante por su numerosidad, biomasa y persistencia en el tiempo, mostró desarrollos masivos durante dos períodos de est ratificaciín térmica.