Archives: Bibliographies

Title

Effects of sea surface warming on the production and composition of dissolved organic matter during phytoplankton blooms: results from a mesocosm study

Publication Type

Journal Article

Year of Publication

2011

Authors

Engel A, Handel N, Wohlers J, Lunau M, Grossart HP, Sommer U, Riebesell U

Journal

Journal of Plankton Research

Volume

33

Pagination

357-372

ISBN Number

Keywords

sea surface warming, DOM, nutrient addition, C:N ratio, mesocosm, Kiel, Germany, 1.4 m3, Polysaccharides, Amino acids, Microbial loop

Abstract

An experimental study was conducted to test the effects of projected sea surfacewarming (according to the IPPC scenarios) on the accumulation and composition ofdissolved organic matter (DOM) during marine phytoplankton blooms in cold seas(,48C). Eight mesocosms ( 1400 L) were filled with natural seawater, and two replicatemesocosms each were incubated by raising temperature by þ0, þ2, þ4 andþ68C, respectively. The enclosed water was initially fertilized with inorganic nutrientsto induce the development of phytoplankton blooms, which were then dominated bydiatoms. Over a 4-week period, dissolved combined carbohydrates (DCCHO) anddissolved amino acids (DAA) were determined as major components of freshly produced, labile to semi-labile DOM. In all mesocosms, the increase in DCCHO concentration occurred sharply after the peak of chlorophyll a concentration, whennutrients became depleted. Rising temperature resulted in an earlier, faster andhigher accumulation of DCCHO and of combined glucose predominantly. DCCHOyielded a maximum percentage of 35, 40, 49 and 59% of total combined carbohydratesin the þ0, þ2, þ4 and þ68C treatments, respectively. Accumulation ofDAA occurred more continuously and at an average rate of 0.79+0.20 nmol L21 h21, but was not affected by rising temperature. Owing to the higheraccumulation of DCCHO, the C:N ratio of DOM increased strongly during thecourse of the bloom, with higher ratios in the warmer treatments. Our study suggeststhat warming increases the extracellular release of carbohydrates from phytoplanktonand, therefore, may affect the bottom-up control of the microbial loop in cold seas inthe future.

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Title

Warming increases the proportion of primary production emitted as methane from freshwater mesocosms

Publication Type

Journal Article

Year of Publication

2011

Authors

Durocher GY, Montoya JM, Woodward G

Journal

Global Change Biology

Volume

17

Pagination

1228-1234

ISBN Number

Keywords

carbon cycle, ecosystem respiration, global warming, metabolic theory, methane, Primary production, mesocosm, freshwater, 1 m3, UK, Dorset

Abstract

Methane (CH4) and carbon dioxide (CO2) are the dominant gaseous end products of the remineralization of organic carbon and also the two largest contributors to the anthropogenic greenhouse effect. We investigated whether warming altered the balance of CH4 efflux relative to gross primary production (GPP) and ecosystem respiration (ER) in a freshwater mesocosm experiment. Whole ecosystem CH4 efflux was strongly related to temperature with an apparent activation energy of 0.85 eV. Furthermore, CH4 efflux increased faster than ER or GPP with temperature, with all three processes having sequentially lower activation energies. Warming of 4 1C increased the fraction of GPP effluxing as CH4 by 20% and the fraction of ER as CH4 by 9%, in line with the offset in their respective activationenergies. Because CH4 is 21 times more potent as a greenhouse gas, relative to CO2, these results suggest freshwater ecosystems could drive a previously unknown positive feedback between warming and the carbon cycle.

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Title

Dynamics of extracellular enzyme activities in seawater under changed atmospheric pCO2: a mesocosm investigation

Publication Type

Journal Article

Year of Publication

2011

Authors

Arnosti C, Grossart HP, Mühling M, Joint I, Passow U

Journal

Aquatic Microbial Ecology

Volume

64

Pagination

285-298

ISBN Number

Keywords

Enzyme, carbon cycle, pCO2 changes, Microbial loop, mesocosm, PEECE, 20m3, Bergen, Norway, Espegrend

Abstract

As part of the PeECE II mesocosm project, we investigated the effects of pCO2 levels onthe initial step of heterotrophic carbon cycling in the surface ocean. The activities of microbial extracellularenzymes hydrolyzing 4 polysaccharides were measured during the development of a naturalphytoplankton bloom under pCO2 conditions representing glacial (190 ?atm) and future (750 ?atm)atmospheric pCO2. We observed that (1) chondroitin hydrolysis was variable throughout the pre-,early- and late-bloom phases, (2) fucoidanase activity was measurable only in the glacial mesocosmas the bloom developed, (3) laminarinase activity was low and constant, and (4) xylanase activitydeclined as the bloom progressed. Concurrent measurements of microbial community composition,using denaturing-gradient gel electrophoresis (DGGE), showed that the 2 mesocosms diverged temporally,and from one another, especially in the late-bloom phase. Enzyme activities correlated withbloom phase and pCO2, suggesting functional as well as compositional changes in microbial communitiesin the different pCO2 environments. These changes, however, may be a response to temporalchanges in the development of phytoplankton communities that differed with the pCO2 environment.We hypothesize that the phytoplankton communities produced dissolved organic carbon(DOC) differing in composition, a hypothesis supported by changing amino acid composition of theDOC, and that enzyme activities responded to changes in substrates. Enzyme activities observedunder different pCO2 conditions likely reflect both genetic and

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Title

Influence of food web structure on the biochemical composition of seston, zooplankton and recently deposited sediment in experimental freshwater mesocosms

Publication Type

Journal Article

Year of Publication

2011

Authors

Allard B, Danger M, Ten-Hage L, Lacroix G

Journal

Aquatic Sciences

Volume

73

Pagination

113-126

ISBN Number

Keywords

Biomanipulation, Biotic compartments, fatty acids, Sterols, trophic cascade, mesocosm, freshwater, 40 m3, Lake Creteil, France

Abstract

The effects of food web structure on the quantity and biochemical composition of seston, zooplankton and recently deposited sediment in experimental freshwatermesocosms were examined. Food web structure was manipulated by addition of zooplanktivorous fish. Biochemical characterisations were carried out using lipidbiomarkers (sterols, fatty acids, chlorophyll-derived compounds and long-chain alkanediols). Fish addition decreased zooplankton biomass and increased seston biomass and deposited sediment through a trophic cascade. Fish presencestrongly influenced the biochemical characteristics of seston and sediment. In contrast, food web structure had a minor impact on the lipid biomarker composition of zooplankton. Although the relative abundance of sterols in the differentcompartments did not differ strongly between treatments, sterol profiles in seston and sediment depended on food web structure. The predominance of D7-sterols in seston and sediment in the fish treatment indicated a major contribution of Chlorophyceae. In contrast, the distribution of sterols in seston and sediment in the fishless treatment, dominated by cholesterol, indicated a major zooplanktonic input. The distribution of fatty acids and the relative abundance of chlorophyll-derived compounds and long-chain alkanediols agreed with the predominant contribution of phytoplankton or zooplankton to seston and sediment in the two treatments. The relative abundance of bacterial biomarkers suggested that the contribution of bacteria was rather low. The high relative abundance of polyunsaturated fatty acids (PUFAs) and the absence of stanols in sediments suggested low microbial reworking of organic matter in the recently accumulated sediments. The trophic cascade, generated by the addition of fish, increased the relative abundance of PUFAs in deposited organic matter, thus enhancing sediment quality and potential degradability.

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Title

Effects of rising temperature on pelagic biogeochemistry in mesocosm systems: a comparative analysis of the AQUASHIFT Kiel experiments

Publication Type

Journal Article

Year of Publication

2012

Authors

Wohlers-Zollner J, Biermann A, Engel A, Dorge P, Lewandowska AM, vonScheibner M, Riebesell U

Journal

Marine Biology

Volume

Pagination

ISBN Number

Keywords

mesocosm, Kiel indoor, Kiel, Germany, 1.4 m3, AQUASHIFT

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Type of Article

Alternate Journal

Title

Spring phenological responses of marine and freshwater plankton to changing temperature and light conditions

Publication Type

Journal Article

Year of Publication

2012

Authors

Winder M, Berger SA, Lewandowska A, Aberle N, Lengfellner K, Sommer U, Diehl S

Journal

Marine Biology

Volume

Online

Pagination

1-11

ISBN Number

0025-3162

Keywords

1.4 m3, mesocosm, Kiel indoor, Kiel, Germany

Abstract

Shifts in the timing and magnitude of the spring plankton bloom in response to climate change have been observed across a wide range of aquatic systems. We used meta-analysis to investigate phenological responses of marine and freshwater plankton communities in mesocosms subjected to experimental manipulations of temperature and light intensity. Systems differed with respect to the dominant mesozooplankton (copepods in seawater and daphnids in freshwater). Higher water temperatures advanced the bloom timing of most functional plankton groups in both marine and freshwater systems. In contrast to timing, responses of bloom magnitudes were more variable among taxa and systems and were influenced by light intensity and trophic interactions. Increased light levels increased the magnitude of the spring peaks of most phytoplankton taxa and of total phytoplankton biomass. Intensified size-selective grazing of copepods in warming scenarios affected phytoplankton size structure and lowered intermediate (20–200 ?m)-sized phytoplankton in marine systems. In contrast, plankton peak magnitudes in freshwater systems were unaffected by temperature, but decreased at lower light intensities, suggesting that filter feeding daphnids are sensitive to changes in algal carrying capacity as mediated by light supply. Our analysis confirms the general shift toward earlier blooms at increased temperature in both marine and freshwater systems and supports predictions that effects of climate change on plankton production will vary among sites, depending on resource limitation and species composition.

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Title

Carbon, nitrogen and phosphorus resource supply and utilisation for coastal planktonic heterotrophic bacteria in a gradient of nutrient loading

Publication Type

Journal Article

Year of Publication

2012

Authors

Vadstein O, Andersen T, Reinertsen HR, Olsen Y

Journal

Marine Ecology Progress Series

Volume

447

Pagination

55-75

ISBN Number

Keywords

DOM production, DOM utilisation, Heterotrophic bacteria, Community interactions, DOC accumulation, Re-mineralisation, Inverse modelling, mesocosm, Norway, Hopavagen, 38 m3

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Title

Zooplankton-mediated nutrient limitation patterns in marine phytoplankton: an experimental approach with natural communities

Publication Type

Journal Article

Year of Publication

2012

Authors

Trommer G, Pondaven P, Siccha M, Stibor H

Journal

Marine Ecology-Progress Series

Volume

449

Pagination

83-94

ISBN Number

0171-8630

Keywords

Nutrient limitation, marine plankton, Zooplankton-driven nutrient, recycling, stoichiometry, pacific subtropical gyre, to-phosphorus stoichiometry, n-p ratios, fresh-water, growth-rate, baltic sea, atlantic-ocean, elemental, crustacean zooplankton, particulate matter

Abstract

Zooplankton nutrient recycling has been shown to substantially affect nutrient availability for phytoplankton. However, investigations are required to determine whether zooplankton also influence nutrient limitation in marine phytoplankton communities, and whether grazing by different zooplankton groups results in different patterns of phytoplankton nutrient limitation. We performed laboratory experiments under different nutrient supply conditions on a variety of phytoplankton communities with natural densities of copepods and rotifers, and tested phytoplankton nutrient limitation in bioassays for nitrogen, phosphorus, and the combination of the two. After 5 d incubation with zooplankton, we observed a significant increase in phytoplankton biomass in the zooplankton treatments. We relate this largely to nutrient recycling effects, which are amplified through possible trophic cascade effects. In copepod treatments, the highest phytoplankton biomass was reached under Redfield and nitrogen excess nutrient supply conditions, while the highest biomass in rotifer treatments was registered under phosphorus excess conditions. In most cases, nutrient limitation assays revealed a co-limitation of phytoplankton by nitrogen and phosphorus. With increasing nitrogen supply, we observed an increase in phosphorus limitation in the copepod treatments and a decrease in nitrogen limitation in the rotifer treatments. The phytoplankton community was driven into phosphorus limitation under nitrogen excess conditions in copepod treatments. Our results indicate that natural densities of zooplankton are able to promote nitrogen and phosphorus co-limitation in phytoplankton communities.

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WOS:000301231500007

Type of Article

Article

Alternate Journal

Mar. Ecol.-Prog. Ser.

Title

Enhanced carbon overconsumption in response to increasing temperatures during a mesocosm experiment

Publication Type

Journal Article

Year of Publication

2012

Authors

Taucher J, Schulz KG, Dittmar T, Sommer U, Oschlies A, Riebesell U

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Keywords

acidification, temperature increase, DOC, DIC, POC, mesocosm, Kiel indoor, Kiel, Germany, 1.4 m3

Abstract

Increasing concentrations of atmospheric carbondioxide are projected to lead to an increase in sea surfacetemperatures, potentially impacting marine ecosystems andbiogeochemical cycling. Here we conducted an indoor mesocosmexperiment with a natural plankton community takenfrom the Baltic Sea in summer.We induced a plankton bloomvia nutrient addition and followed the dynamics of the differentcarbon and nitrogen pools for a period of one month attemperatures ranging from 9.5 C to 17.5 C, representing arange of ±4 C relative to ambient temperature. The uptakeof dissolved inorganic carbon (DIC) and the net build-up ofboth particulate (POC) and dissolved organic carbon (DOC)were all enhanced at higher temperatures and almost doubledover a temperature gradient of 8 C. Furthermore, elementalratios of carbon and nitrogen (C : N) in both particulateand dissolved organic matter increased in response tohigher temperatures, both reaching very high C :N ratios of>30 at +4 C. Altogether, these observations suggest a pronouncedincrease in excess carbon fixation in response to elevatedtemperatures. Most of these findings are contrary to resultsfrom similar experiments conducted with plankton populationssampled in spring, revealing large uncertainties inour knowledge of temperature sensitivities of key processesin marine carbon cycling. Since a major difference to previousmesocosm experiments was the dominant phytoplanktonspecies, we hypothesize that species composition might playan important role in the response of biogeochemical cyclingto increasing temperatures.

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Title

Experimental induction of a coastal spring bloom early in the year by intermittent high-light episodes

Publication Type

Journal Article

Year of Publication

2012

Authors

Sommer U, Lengfellner K, Lewandowska A

Journal

Marine Ecology Progress Series

Volume

446

Pagination

61-71

ISBN Number

Keywords

Plankton, spring bloom, irradiance, mesocosm, Kiel indoor, Kiel, Germany, 1.4 m3

Abstract

Through the use of mesocosm experiments, we show that an unusually early springphytoplankton bloom can be induced by intermittent high-light periods. We performed mesocosmexperiments where plankton assemblages from Kiel Bight (Western Baltic Sea) received a lightregime based on the natural seasonal irradiance dimmed to 43% of surface irradiance of cloudlessdays, starting with irradiance levels of mid-January (6 mesocosms) and mid-February (6 mesocosms).After 6 d, half of the mesocosms received a ca. 2-fold increase in irradiance. In the Januarymesocosms, a phytoplankton bloom developed only in the treatments with the high-light episode,whereas in the February mesocosms a phytoplankton bloom also developed in the controls. Phytoplanktonnet growth rates, pro duction:biomass ratios and biomass at the end of the high irradianceepisodes were positively correlated to the daily light dose. The relative biomass of diatomsincreased with increasing light, whereas the relative biomass of cryptophytes decreased. A bottom-up transmission to mesozooplankton (mainly copepods of the genera Acartia and Oithona)was evident by increased densities of copepod nauplii and egg production under higher light conditions,whereas copepodids and adults showed no responses during the experimental period. Thetaxonomic composition of the nauplii was shifted to the advantage of Acartia/Centropages (notdistinguished at the naupliar stage) under higher light conditions.

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