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Journal of Plankton Research

Michael Blackett, Cathy H Lucas, Katherine Cook, Priscilla Licandro
We applied the concept of source-sink dynamics to investigate a recent (1999-2013) increase in the occurrence of the siphonophore Muggiaea atlantica in Scottish coastal waters. Our aim was to determine whether this change represented the establishment of resident populations (i.e. "sources"), or transient populations reliant on immigration (i.e. "sinks"). First, we show that local production was not always sufficient to account for recruitment (a "source" prerequisite), suggesting reliance on immigration (a "sink" prerequisite)...
January 2017: Journal of Plankton Research
J Paczkowska, O F Rowe, L Schlüter, C Legrand, B Karlson, A Andersson
It is well-known that nutrients shape phytoplankton communities in marine systems, but in coastal waters allochthonous dissolved organic matter (ADOM) may also be of central importance. We studied how humic substances (proxy of ADOM) and other variables influenced the nutritional strategies, size structure and pigment content of the phytoplankton community along a south-north gradient in the Baltic Sea. During the summer, the proportion of mixotrophs increased gradually from the phosphorus-rich south to the ADOM-rich north, probably due to ADOM-fueled microbes...
January 2017: Journal of Plankton Research
Andrew P Rees, Karen Tait, Claire E Widdicombe, Graham D Quartly, Andrea J McEvoy, Lisa Al-Moosawi
Trichodesmium, a colonial cyanobacterium typically associated with tropical waters, was observed between January and April 2014 in the western English Channel. Sequencing of the heterocyst differentiation (hetR) and 16S rRNA genes placed this community within the Clade IV Trichodesmium, an understudied clade previously found only in low numbers in warmer waters. Nitrogen fixation was not detected although measurable rates of nitrate uptake and carbon fixation were observed. Trichodesmium RuBisCO transcript abundance relative to gene abundance suggests the potential for viable and potentially active Trichodesmium carbon fixation...
May 2016: Journal of Plankton Research
Jennifer Marie Questel, Leocadio Blanco-Bercial, Russell R Hopcroft, Ann Bucklin
The genus Pseudocalanus (Copepoda, Calanoida) is among the most numerically dominant copepods in eastern North Pacific and Pacific-Arctic waters. We compared population connectivity and phylogeography based on DNA sequence variation for a portion of the mitochondrial cytochrome oxidase I gene for four Pseudocalanus species with differing biogeographical ranges within these ocean regions. Genetic analyses were linked to characterization of biological and physical environmental variables for each sampled region...
May 2016: Journal of Plankton Research
Boris Espinasse, Sünnje L Basedow, Vigdis Tverberg, Tore Hattermann, Ketil Eiane
High Calanus finmarchicus abundances were recorded in wintertime in Vestfjorden, close to the main cod breeding grounds off Lofoten and Vesterålen, northern Norway. The mean abundance for locations with water depth >500 m was ∼37000 ind. m(-2) (range: 26700-49000 ind. m(-2)). To our knowledge, this is the first report of massive overwintering of C. finmarchicus on the Norwegian shelf. Because of the observed size and location of this population, we argue that local overwintering on the northern Norwegian shelf can contribute significantly to sustain a C...
May 2016: Journal of Plankton Research
Shunyan Cheung, Xiaomin Xia, Cui Guo, Hongbin Liu
Oxygen minimum zones (OMZs), characterized by depleted dissolved oxygen concentration in the intermediate depth of the water column, are predicted to expand under the influence of global warming. Recent studies in the Eastern Tropical South Pacific Ocean and Arabian Sea have reported that heterotrophic nitrogen fixation is active in the OMZs. In this study, we investigated the community structure of diazotrophs in the OMZ of the Costa Rica Dome (CRD) upwelling region in the Eastern Tropical North Pacific Ocean, using 454-pyrosequencing of nifH gene amplicons...
March 2016: Journal of Plankton Research
Michael R Landry, Karen E Selph, Moira Décima, Andrés Gutiérrez-Rodríguez, Michael R Stukel, Andrew G Taylor, Alexis L Pasulka
We investigated phytoplankton production rates and grazing fates in the Costa Rica Dome (CRD) during summer 2010 based on dilution depth profiles analyzed by flow cytometry and pigments and mesozooplankton grazing assessed by gut fluorescence. Three community production estimates, from (14)C uptake (1025 ± 113 mg C m(-2) day(-1)) and from dilution experiments analyzed for total Chla (990 ± 106 mg C m(-2) day(-1)) and flow cytometry populations (862 ± 71 mg C m(-2) day(-1)), exceeded regional ship-based values by 2-3-fold...
March 2016: Journal of Plankton Research
Michael R Stukel, Claudia R Benitez-Nelson, Moira Décima, Andrew G Taylor, Carolyn Buchwald, Michael R Landry
The Costa Rica Dome is a picophytoplankton-dominated, open-ocean upwelling system in the Eastern Tropical Pacific that overlies the ocean's largest oxygen minimum zone. To investigate the efficiency of the biological pump in this unique area, we used shallow (90-150 m) drifting sediment traps and (234)Th:(238)U deficiency measurements to determine export fluxes of carbon, nitrogen and phosphorus in sinking particles. Simultaneous measurements of nitrate uptake and shallow water nitrification allowed us to assess the equilibrium balance of new and export production over a monthly timescale...
March 2016: Journal of Plankton Research
Stephen B Baines, Xi Chen, Benjamin S Twining, Nicholas S Fisher, Michael R Landry
Mineral limitation of mesozooplankton production is possible in waters with low trace metal availability. As a step toward estimating mesozooplankton Fe and Zn requirements under such conditions, we measured tissue concentrations of major and trace nutrient elements within size-fractioned zooplankton samples collected in and around the Costa Rica Upwelling Dome, a region where phytoplankton growth may be co-limited by Zn and Fe. The geometric mean C, N, P contents were 27, 5.6 and 0.21 mmol gdw(-1), respectively...
March 2016: Journal of Plankton Research
Moira Décima, Michael R Landry, Michael R Stukel, Lucia Lopez-Lopez, Jeffrey W Krause
We investigated standing stocks and grazing rates of mesozooplankton assemblages in the Costa Rica Dome (CRD), an open-ocean upwelling ecosystem in the eastern tropical Pacific. While phytoplankton biomass in the CRD is dominated by picophytoplankton (<2-µm cells) with especially high concentrations of Synechococcus spp., we found high mesozooplankton biomass (∼5 g dry weight m(-2)) and grazing impact (12-50% integrated water column chlorophyll a), indicative of efficient food web transfer from primary producers to higher levels...
March 2016: Journal of Plankton Research
Melanie L Jackson, Sharon L Smith
A variety of ecological strategies for tolerance of low-oxygen conditions within the Costa Rica Dome (CRD) area of the Eastern Tropical Pacific are documented for the copepod family Eucalanidae. During the summer of 2010, we compared the ecological strategies used by the Eucalanidae inside and outside the central CRD region. We compared the vertical and horizontal distributions of five species, Eucalanus inermis, Subeucalanus subtenuis, Subeucalanus subcrassus, Subeucalanus pileatus and Pareucalanus attenuatus together with Rhincalanus species, in the epipelagic (upper 200 m) among four locations, which we grouped into a section roughly crossing the core CRD area (inside-outside core CRD)...
March 2016: Journal of Plankton Research
Joaquim I Goes, Helga do Rosario Gomes, Karen E Selph, Michael R Landry
The Costa Rica Dome (CRD) is a unique open-ocean upwelling system, with picophytoplankton dominance of phytoplankton biomass and suppressed diatoms, yet paradoxically high export of biogenic silica. As a part of Flux and Zinc Experiments cruise in summer (June-July 2010), we conducted shipboard incubation experiments in the CRD to examine the potential roles of Si, Zn, Fe and light as regulating factors of phytoplankton biomass and community structure. Estimates of photosynthetic quantum yields revealed an extremely stressed phytoplankton population that responded positively to additions of silicic acid, iron and zinc and higher light conditions...
March 2016: Journal of Plankton Research
Andrés Gutiérrez-Rodríguez, Karen E Selph, Michael R Landry
The Costa Rica Dome (CRD) represents a classic case of the bloom-forming capacity of small phytoplankton. Unlike other upwelling systems, autotrophic biomass in the CRD is dominated by picocyanobacteria and small eukaryotes that outcompete larger diatoms and reach extremely high biomass levels. We investigated responses of the subsurface phytoplankton community of the CRD to changes associated with vertical displacement of water masses, coupling in situ transplanted dilution experiments with flow cytometry and epifluorescence microscopy to assess group-specific dynamics...
March 2016: Journal of Plankton Research
Stephen B Baines, Xi Chen, Stefan Vogt, Nicholas S Fisher, Benjamin S Twining, Michael R Landry
Mesozooplankton production in high-nutrient low-chlorophyll regions of the ocean may be reduced if the trace element concentrations in their food are insufficient to meet growth and metabolic demands. We used elemental microanalysis (SXRF) of single-celled plankton to determine their trace metal contents during a series of semi-Lagrangian drift studies in an HNLC upwelling region, the Costa Rica Dome (CRD). Cells from the surface mixed layer had lower Fe:S but higher Zn:S and Ni:S than those from the subsurface chlorophyll maximum at 22-30 m...
March 2016: Journal of Plankton Research
P Dreux Chappell, Jagruti Vedmati, Karen E Selph, Heather A Cyr, Bethany D Jenkins, Michael R Landry, James W Moffett
The Costa Rica Dome (CRD) is a wind-driven feature characterized by high primary production and an unusual cyanobacterial bloom in surface waters. It is not clear whether this bloom arises from top-down or bottom-up processes. Several studies have argued that trace metal geochemistry within the CRD contributes to the composition of the phytoplankton assemblages, since cyanobacteria and eukaryotic phytoplankton have different transition metal requirements. Here, we report that total dissolved zinc (Zn) is significantly depleted relative to phosphate (P) and silicate (Si) within the upper water column of the CRD compared with other oceanic systems, and this may create conditions favorable for cyanobacteria, which have lower Zn requirements than their eukaryotic competitors...
March 2016: Journal of Plankton Research
Alexandra Freibott, Andrew G Taylor, Karen E Selph, Hongbin Liu, Wuchang Zhang, Michael R Landry
We investigated biomass and composition of heterotrophic microbes in the Costa Rica Dome during June-July 2010 as part of a broader study of plankton trophic dynamics. Because picophytoplankton (<2 μm) are known to dominate in this unique upwelling region, we hypothesized tight biomass relationships between size-determined predator-prey pairs (i.e. picoplankton-nano-grazers, nanoplankton-micro-grazers) within the microbial community. Integrated biomass of heterotrophic bacteria ranged from 180 to 487 mg C m(-2) and was significantly correlated with total autotrophic carbon...
March 2016: Journal of Plankton Research
Jeffrey W Krause, Michael R Stukel, Andrew G Taylor, Darcy A A Taniguchi, Alain De Verneil, Michael R Landry
We determined the net rate of biogenic silica (bSiO2) production and estimated the diatom contribution to new production and organic matter export in the Costa Rica Dome during summer 2010. The shallow thermocline significantly reduces bSiO2 dissolution rates below the mixed layer, leading to significant enhancement of bSiO2 relative to organic matter (silicate-pump condition). This may explain why deep export of bSiO2 in this region is elevated by an order of magnitude relative to comparable systems. Diatom carbon, relative to autotrophic carbon, was low (<3%); however, the contribution of diatoms to new production averaged 3 and 13% using independent approaches...
March 2016: Journal of Plankton Research
Karen E Selph, Michael R Landry, Andrew G Taylor, Andrés Gutiérrez-Rodríguez, Michael R Stukel, John Wokuluk, Alexis Pasulka
During summer 2010, we investigated phytoplankton production and growth rates at 19 stations in the eastern tropical Pacific, where winds and strong opposing currents generate the Costa Rica Dome (CRD), an open-ocean upwelling feature. Primary production ((14)C-incorporation) and group-specific growth and net growth rates (two-treatment seawater dilution method) were estimated from samples incubated in situ at eight depths. Our cruise coincided with a mild El Niño event, and only weak upwelling was observed in the CRD...
March 2016: Journal of Plankton Research
Andrew G Taylor, Michael R Landry, Alexandra Freibott, Karen E Selph, Andrés Gutiérrez-Rodríguez
We investigated biomass, size-structure, composition, depth distributions and spatial variability of the phytoplankton community in the Costa Rica Dome (CRD) in June-July 2010. Euphotic zone profiles were sampled daily during Lagrangian experiments in and out of the dome region, and the community was analyzed using a combination of digital epifluorescence microscopy, flow cytometry and HPLC pigments. The mean depth-integrated biomass of phytoplankton ranged 2-fold, from 1089 to 1858 mg C m(-2) (mean ± SE = 1378 ± 112 mg C m(-2)), among 4 water parcels tracked for 4 days...
March 2016: Journal of Plankton Research
Michael R Landry, Alain De Verneil, Joaquim I Goes, James W Moffett
The Costa Rica Dome (CRD) is an open-ocean upwelling system in the Eastern Tropical Pacific that overlies the ocean's largest oxygen minimum zone (OMZ). The region has unique characteristics, biomass dominance by picophytoplankton, suppressed diatoms, high biomass of higher consumers and presumptive trace metal limitation, but is poorly understood in terms of pelagic stock and process relationships, including productivity and production controls. Here, we describe the goals, project design, physical context and major findings of the Flux and Zinc Experiments cruise conducted in June-July 2010 to assess trophic flux relationships and elemental controls on phytoplankton in the CRD...
March 2016: Journal of Plankton Research
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