Archives: Bibliographies

Title

Effects of simulated benthic fluxes on phytoplankton dynamic and photosynthetic parameters in a mesocosm experiment (Bay of Brest, France)

Publication Type

Journal Article

Year of Publication

2010

Authors

Claquin P, Longphuirt SN, Fouillaron P, Huonnic P, Ragueneau O, Klein C, Leynaert A

Journal

Estuarine Coastal and Shelf Science

Volume

86

Pagination

93-101

ISBN Number

Keywords

mesocosm, Nutrient inputs, Photosynthesis, Diatoms, Pseudo-nitzschia, Crepidula fornicata, Brest, France, 5.5 m3

Abstract

Benthic faunal activity and density play an important role in determining the rates of benthic nutrientfluxes, which enrich the water column and contribute to phytoplankton growth. The intensity of nutrientfluxes in the Bay of Brest depends on the density of the invasive gastropod, Crepidula fornicata. In order tostudy the impact of benthic fluxes on phytoplankton dynamics, realistic daily nutrient inputs simulatingvarious densities of C. fornicata were added to six enclosures during three weeks. The increase infertilization intensity influenced the phytoplankton biomass. A succession from Chaetoceros spp. toPseudo-nitzschia spp. and Leptocylindrus danicus was observed in all enclosures, but the dynamics ofsuccessions were different. Pseudo-nitzschia spp. was favored in the three more fertilized enclosures,while Chaetoceros spp. persisted longer in less enriched enclosures. Despite an apparent nitrogen limitation,the quantum efficiency of PSII (Fv/Fm) was high (>0.5) and stable in all enclosures. The maximalphotosynthetic capacity (PBmax) was also invariable and oscillated around an average value of 2.23 mg C(mg Chl a) 1 h 1. The stability of Fv/Fm and PBmax observed at different nutrient input intensitiesdemonstrates that the daily inputs maintained the physiological balance of the microalgae. The maximallight utilization efficiency (a) and the light saturation parameter (Ek) were also quite stable after day 8,which reveals that photosynthetic parameters were driven by growth constraints due to nutrientavailability and not by incident light or species successions. We suggest that our results correspond to an‘‘Ek independent variation’’ regulation. We propose that such regulation of photosynthetic parametersappears when there are frequent nutrient additions which do not allow replete nutrient conditions to bereached but lead to physiological equilibrium.Thanks to our results we can understand how even low benthic fluxes, by supporting their cellularphysiological status, allowed diatoms to dominate the phytoplankton community in the six enclosures.These results confirm the importance of daily benthic inputs as much as the amount of nutrient inputs.However, we suggest that high benthic fluxes have a buffering effect on nutrient availability, therebylimiting the consequences of short-term events which can entail a sudden increase of nutrient input, andare known to promote Dinophyta bloom formation

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Title

Ocean acidification affects iron speciation during a coastal seawater mesocosm experiment

Publication Type

Journal Article

Year of Publication

2010

Authors

Breitbarth E, Bellerby RGJ, Neill CC, Ardelan MV, Meyerhofer M, Zollner E, Croot PL, Riebesell U

Journal

Biogeosciences

Volume

7

Pagination

1065-1073

ISBN Number

Keywords

CO2 enrichment, mesocosm, Iron speciation, Bloom, Primary production, Raunefjord, Bergen, Norway, PEECE, 30 m3

Abstract

Rising atmospheric CO2 is acidifying the surface ocean, a process which is expected to greatly influence the chemistry and biology of the future ocean. Following the development of iron-replete phytoplankton blooms in a coastal mesocosm experiment at 350, 700, and 1050 ?atm pCO2,we observed significant increases in dissolved iron concentrations,Fe(II) concentrations, and Fe(II) half-life times duringand after the peak of blooms in response to CO2 enrichmentand concomitant lowering of pH, suggesting increasediron bioavailability. If applicable to the open ocean this mayprovide a negative feedback mechanism to the rising atmosphericCO2 by stimulating marine primary production.

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Title

Water temperature and stratification depth independently shift cardinal events during plankton spring succession

Publication Type

Journal Article

Year of Publication

2010

Authors

Berger SA, Diehl S, Stibor H, Trommer G, Ruhenstroth M

Journal

Global Change Biology

Volume

16

Pagination

1954-1965

ISBN Number

Keywords

ciliates, clearwater phase, Daphnia, enclosure, mesocosm, phytoplankton, spring bloom, freshwater, 7 m3, Seeon, Germany

Abstract

In deep temperate lakes, the beginning of the growing season is triggered by thermal stratification, which alleviates light limitation of planktonic producers in the surface layer and prevents heat loss to deeper strata. The sequence of subsequent phenological events (phytoplankton spring bloom, grazer peak, clearwater phase) results in part from coupled phytoplankton–grazer interactions. Disentangling the separate, direct effects of correlated climatic drivers (stratificationdependent underwater light climate vs. water temperature) from their indirect effects mediated through trophic feedbacks is impossible using observational field data, which challenges our understanding of global warming effects on seasonal plankton dynamics. We therefore manipulated water temperature and stratification depth independently in experimental field mesocosms containing ambient microplankton and inocula of the resident grazer Daphnia hyalina. Higher light availability in shallower surface layers accelerated primary production, warming accelerated consumption and growth of Daphnia, and both factors speeded up successional dynamics driven by trophic feedbacks. Specifically, phytoplankton peaked and decreased earlier and Daphnia populations increased and peaked earlier at both shallower stratification and higher temperature. The timing of ciliate dynamics was unrelated to both factors. Volumetric peak densities of phytoplankton, ciliates and Daphnia in the surface layer were also unaffected by temperature but declined with stratification depth in parallel with light availability. The latter relationship vanished, however, when population sizes were integrated over the entire water column. Overall our results suggest that, integrated over the entire water column of a deep lake,surface warming and shallower stratification independently speed up spring successional events, whereas the magnitudes of phytoplankton and zooplankton spring peaks are less sensitive to these factors. Therefore, accelerated dynamics under warming need not lead to a trophic mismatch (given similar grazer inocula at the time of stratification). We emphasize that entire water column dynamics must be studied to estimate global warming effects on lake ecosystems

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Growth phase of the diatom Skeletonema marinoi influences the metabolic profile of the cells and the selective feeding of the copepod Calanus spp.

Publication Type

Journal Article

Year of Publication

2010

Authors

Barofsky A, Simonelli P, Vidouez C, Troedsson C, Nejstgaard JC, Jacobsen HH, Pohnert G

Journal

Journal of Plankton Research

Volume

32

Pagination

263-272

ISBN Number

Keywords

Copepod diet, prey selectivity, PCR, Sceletonema, Calanus, mesocosm, Espegrend, Bergen, Norway

Abstract

Copepods dominate the biomass of marine zooplankton and through their prey selectionthey act as top-down regulators of planktonic communities. We investigatedfeeding preference of copepods in the presence of the diatom Skeletonema marinoi atdifferent time points throughout the development of a bloom and a culture.Quantitative PCR gut content assessment revealed that the food uptake of thecopepod Calanus spp. on mixed diets and on artificially induced mesocosm bloomswas selective. Uptake of S. marinoi was highest during the post-bloom phase in themesocosms even if the abundance of this alga was already low. In laboratory assays,copepods showed a greater preference for S. marinoi in the late stationary phase thanfor cultures of the same strain under exponentially growing culture conditions. Thecopepods thus discriminate between different growth phases of a single algal speciesin both laboratory and field settings. In parallel, we monitored cellular metabolites ofthe diatom using a metabolomic approach. Complex changes in the metabolic profileoccur during development of a culture. Since no obvious effect of nutrient qualityand cell size was involved, we suggest that changes in (info)chemicals within orsurrounding S. marinoi regulate selective feeding by zooplankton.

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Title

Dust deposition: iron source or sink?A case study

Publication Type

Journal Article

Year of Publication

2011

Authors

Ye Y, Wagener T, Volker C, Guieu C, Wolf-Gladrow DA

Journal

Biogeosciences

Volume

7

Pagination

9219-9272

ISBN Number

Keywords

Dust deposition, Iron, mesocosm, Corsica, 52 m3, France

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Title

Effects of experimental warming and increased ultraviolet B radiation on the Mediterranean plankton food web

Publication Type

Journal Article

Year of Publication

2011

Authors

Vidussi F, Mostajir B, Fouilland E, Floch LE, Nouguier J, Roques C, Got P, Thibault-Botha D, Bouvier T, Troussellier M

Journal

Limnology & Oceanography

Volume

56

Pagination

206-218

ISBN Number

Keywords

Ultraviolet radiation, UVB, Food web, temperature, light manipulation, mesocosm, MEDIMEER, Montpellier, France, 1.8 m3

Abstract

The responses of the plankton food web to increases in temperature and ultraviolet B radiation (UVBR, 280–320 nm) were experimentally investigated at a coastal Mediterranean site during spring. Eight moored mesocosmswere used to compare natural plankton food web responses (control mesocosms) with three treatments simulatingexpected future local temperature and UVBR increases, as follows: (1) 3uC increase in water temperature, (2) 20%increase in incident UVBR, and (3) simultaneous 3uC increase in water temperature and 20% increase in incidentUVBR. The plankton food web was resistant to elevated UVBR, having only moderate effects on planktonabundances and structure. In contrast, warming induced significant shifts in the plankton food web structure andfunction. Specifically, the abundance of protozooplankton (ciliates and flagellates) increased and the developmenttime of copepods from nauplii to adults decreased. In the warm mesocosms, the emergence of copepod adultstages midway through the experiment resulted in a decrease in ciliates and consequently in an increase inheterotrophic flagellates. One unexpected result was that warming reduced the abundance of heterotrophicbacteria midway through the experiment. These results indicate a trophic-cascade effect under warming. Theincrease in adult copepods diminishes ciliates and in turn favors heterotrophic flagellates that consume bacteria.Warming also induced an increase in net oxygen production, indicating an increase in net primary production

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Title

Dynamics of Dissolved and Particulate Polyunsaturated Aldehydes in Mesocosms Inoculated with Different Densities of the Diatom Skeletonema marinoi

Publication Type

Journal Article

Year of Publication

2011

Authors

Vidoudez C, Nejstgaard JC, Jakobsen HH, Pohnert G

Journal

Marine Drugs

Volume

9

Pagination

345-358

ISBN Number

Keywords

Chemical defence, plankton blooms, Programmed cell death, oxylipins, heptadienal, Skeletonema, Phaeocystis, PUA, mesocosm, Raunefjord, Bergen, Norway, 10 m3

Abstract

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Title

The combined effect of ultraviolet B radiation and temperature increase on phytoplankton dynamics and cell cycle using pulse shape recording flow cytometry

Publication Type

Journal Article

Year of Publication

2011

Authors

Thyssen M, Ferreyra G, Moreau S, Schloss I, Denis M, Demers S

Journal

Journal of Experimental Marine Biology and Ecology

Volume

406

Pagination

95-107

ISBN Number

Keywords

Flow cytometry, global warming, mesocosm, phytoplankton dynamics, temperature, Ultraviolet radiation, UVB, 2 m3, Rimouski, Quebec, Canada

Abstract

Temperature and ultraviolet radiation B (UVB) are expected to increase in the next few decades and will mostlyaffect mid and high latitudes. In order to study the combined effect of temperature and UVB increase, on thephytoplankton community in the Saint Lawrence Estuary, duplicates of four different treatmentswere applied to2m3 mesocosms to simulate an overall 3 °C and a 77.8% UVB increase, and combined. Samples were collectedevery 6 h over 10 days and the phytoplankton community was then analysed using a conventional flowcytometer and a Cytosense flow cytometer. Flow cytometry distinguished 9 clusters (Pico, Nano I, C3, C4,CHAINS, C6, C7 and C8) of cells sharing similar optical properties with average sizes varying from 1.3 ?m up to101 ?m for chain forming cells. Compared to untreated enclosures, the high UVB treatment induced lower cellabundances (up to ?40%) for clusters Pico, Nano I, C4, CHAINS and C7, followed by an unexpected cellabundance increase in all the clusters during the last 3 days of the experiment (up to 46%). This increase wassustained by faster calculated periodicities of the cell optical characteristics and abundances, linked to a shortercell cycle. In the samples fromthe high temperature treatmentmesocosms, a positive delaywas observed for thecell abundance increase in clusters CHAINS, C6 and C8, combined with higher average abundance values (up to67% with respect to untreated mesocosms). During the last 3 days of the experiment, abundances decreasedcompared to the values observed in the high UVB mesocosms, with a slower trend in the periodicities,suggesting that high temperature inhibits the cell cycle. The combined temperature and UVB treatmentemphasized the effects observed under high temperature treatments, maintaining temperature positive effects(i.e. higher abundances) on clusters C3, CHAINS, C6 and C8 suggesting a compensation from the positivetemperature effects over the negative (i.e. lower abundances) UVB effects. Increasing temperature induced anegative effect on the abundance of clusters C4 and C7. In this case, trends in C6 and C8 cell periodicities werefaster than under normal conditions while Nano I, C4 and C7 cycles were slower. Cellsb3 ?m were negativelyaffected by the combined exposure (up to ?55% compared to untreated mesocosms) while most of the largercells were positively affected (up to 75% compared to untreated mesocosms), suggesting a shift to anherbivorous food web (sensu Legendre and Rassoulzadegan, 1995). Results suggest that changes in cell cyclesdue to increases in temperature or UVB exposure may play an important role in controlling abundance.

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Title

Moving on up: can results from simple aquatic mesocosm experiments be applied across broad spatial scales?

Publication Type

Journal Article

Year of Publication

2011

Authors

Spivak AC, Vanni MJ, Mette EM

Journal

Freshwater biology

Volume

56

Pagination

279-291

ISBN Number

Keywords

chlorophyll, experimental design, mesocosm, Nutrients, scaling, 0.004 m3, 0.02 m3, 1 m3, 5 m3, 500 m3, USA

Abstract

1. Aquatic ecologists use mesocosm experiments to understand mechanisms drivingecological processes. Comparisons across experiments, and extrapolations to larger scales,are complicated by the use of mesocosms with varying dimensions. We conducted amesocosm experiment over a volumetric scale spanning five orders of magnitude (from4 L to whole ponds) to determine the generality of algal responses to nutrient enrichment.Recognising that mesocosm dimensions may affect algal growth, we also manipulated theratio of mesocosm surface area to volume (SA : V) over two levels (high versus low). Weused mesocosm tanks of similar size and construction to those commonly used in aquaticexperiments to increase the generality of our results.2. Volume was generally a stronger determinant of algal responses than mesocosm shape(i.e. SA : V). However, the effects of both volume and shape on algae were weak andexplained a small portion of the variance in response variables. In addition, there was noconsistent, directional relationship (positive or neutral) between mesocosm volume andalgal abundance (estimated by chlorophyll concentration). Combined, our findings suggestthat results from small-scale experiments, examining the direct response of algae tonutrient enrichment, can probably be ‘moved on up’ and applied to larger, more naturalaquatic systems.3. Algal response to nutrient enrichment (e.g. nutrient use efficiency and effect size) variedstrongly with time. This underscores the importance of choosing an experimentaltimescale appropriate to the biological and? or ecological process of interest.4. We compared our results to those from a recent meta-analysis of nutrient-limitationstudies that included 359 freshwater pelagic experiments, spanning a wide range ofvolumetric and temporal scales. Similar findings between this experiment and the metaanalysisindicate that algal response to nutrient enrichment varies little across spatialscales. Therefore, it is probable that results from small-scale pelagic algal nutrientlimitationexperiments are relevant to large-scale processes, such as eutrophication.

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Title

Climate change and the phytoplankton spring bloom: warming and overwintering zooplankton have similar effects on phytoplankton

Publication Type

Journal Article

Year of Publication

2011

Authors

Sommer U, Lewandowska A

Journal

Global Change Biology

Volume

17

Pagination

154-162

ISBN Number

Keywords

climate change, mesocosm, phytoplankton, spring bloom, Zooplankton, Kiel, 1.4 m3, Germany

Abstract

Indoor mesocosms were used to study the combined effect of warming and of different densities of overwinteringmesozooplankton (mainly copepods) on the spring development of phytoplankton in shallow, coastal waters. Similarto previous studies, warming accelerated the spring phytoplankton peak by ca. 1 day 1C 1 whereas zooplankton didnot significantly influence timing. Phytoplankton biomass during the experimental period decreased with warmingand with higher densities of overwintering zooplankton. Similarly, average cell size and average effective particle size(here: colony size) decreased both with zooplankton density and warming. A decrease in phytoplankton particle sizeis generally considered at typical footprint of copepod grazing. We conclude that warming induced changes in themagnitude and structure of the phytoplankton spring bloom cannot be understood without considering grazing byoverwintering zooplankton.

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