Posts Tagged 'mesocosms'

Ocean acidification-induced restructuring of the plankton food web can influence the degradation of sinking particles

Ocean acidification (OA) is expected to alter plankton community structure in the future ocean. This, in turn, could change the composition of sinking organic matter and the efficiency of the biological carbon pump. So far, most OA experiments involving entire plankton communities have been conducted in meso- to eutrophic environments. However, recent studies suggest that OA effects may be more pronounced during prolonged periods of nutrient limitation. In this study, we investigated how OA-induced changes in low-nutrient adapted plankton communities of the subtropical North Atlantic Ocean may affect particulate organic matter (POM) standing stocks, POM fluxes, and POM stoichiometry. More specifically, we compared the elemental composition of POM suspended in the water column to the corresponding sinking material collected in sediment traps. Three weeks into the experiment, we simulated a natural upwelling event by adding nutrient-rich deep-water to all mesocosms, which induced a diatom-dominated phytoplankton bloom. Our results show that POM was more efficiently retained in the water column in the highest CO2 treatment levels (>800 μatm pCO2) subsequent to this bloom. We further observed significantly lower C:N and C:P ratios in post-bloom sedimented POM in the highest CO2 treatments, suggesting that degradation processes were less pronounced. This trend is most likely explained by differences in micro- and mesozooplankton abundance during the bloom and post-bloom phase. Overall, this study shows that OA can indirectly alter POM fluxes and stoichiometry in subtropical environments through changes in plankton community structure.

Continue reading ‘Ocean acidification-induced restructuring of the plankton food web can influence the degradation of sinking particles’

Metabolic responses to elevated pCO2 in the gills of the Pacific Oyster (Magallana gigas) using a GC-TOF-MS-based metabolomics approach

Rising atmospheric carbon dioxide (CO2), primarily from human fossil fuel combustion and cement production, are resulting in increasing absorption of CO2 by the oceans, which has led to a decline in ocean pH in a process known as ocean acidification (OA). There is a growing body of evidence demonstrating the potential effect of OA on life-history traits of marine organisms. Consequently, gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) based metabolic profiling approach was applied to examine the metabolic responses of Magallana gigas to elevated pCO2 levels, under otherwise natural field conditions. CO2. Oysters were exposed natural environmental pCO2 (~625.40 μatm) and elevated pCO2 (~1432.94 μatm) levels for 30 days. Results indicated that 36 differential metabolites with variable importance in the projection (VIP) value greater than 1 and Student’s t-test lower than 0.05 were identified. Differential metabolites were mapped in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database to search for the related metabolic pathways. Pathway enrichment analysis indicates that alanine, aspartate and glutamate metabolism and glycine, serine and threonine metabolism were the most statistically enriched pathways. Further analysis suggested that elevated pCO2 disturb the TCA cycle via succinate accumulation and Magallana gigas most likely adjust their energy metabolic via alanine and GABA accumulation accordingly to cope with elevated pCO2. These findings provide an understanding of the molecular mechanisms involved in modulating metabolism under elevated pCO2 levels associated with predicted OA.

Continue reading ‘Metabolic responses to elevated pCO2 in the gills of the Pacific Oyster (Magallana gigas) using a GC-TOF-MS-based metabolomics approach’

Étude en mésocosmes des impacts de l’acidification et du réchauffement sur la composition élémentaire de la biomasse planctonique et le cycle de l’azote dans l’estuaire maritime du Saint-Laurent (in French)

Les changements globaux ont le potentiel d’altérer les cycles biogéochimiques entraînant des répercussions pour tout le réseau alimentaire. Puisque l’azote est généralement l’élément limitant en milieu estuarien, une altération de son cycle pourrait influencer l’ampleur et le type de production primaire ainsi que la composition de la communauté phytoplanctonique qui l’effectue. Il en va de même pour la composition de la matière organique qui peut affecter la valeur nutritive des algues pour les consommateurs de même que l’efficacité de la pompe biologique. Actuellement, aucune étude portant sur les impacts combinés de l’acidification et du réchauffement des eaux de l’estuaire maritime du Saint-Laurent n’a été réalisée. L’objectif de ce projet de maîtrise fut d’évaluer expérimentalement, à l’aide de mésocosme, les impacts cumulés que ces changements pourraient avoir sur la dynamique des nutriments et de l’azote en particulier ainsi que sur la composition élémentaire de la matière organique. Une combinaison factorielle de six pH (7,2; 7,4; 7,6; 7,8; 8,0 et un pH sans contrôle) et de deux températures (10 et 15°C) fut employée. Les résultats de l’expérience suggèrent que les organismes responsables des processus à l’étude sont tolérants à une diminution considérable du pH. Ceux-ci furent toutefois affectés par la hausse de température, qui entraîna une diminution du ratio N:P de consommation des nutriments, accéléra le développement de la floraison phytoplanctonique et l’épuisement des nutriments, puis mena à un changement taxonomique en fin d’expérience. Ce changement est possiblement responsable des différences observées dans la composition de la matière organique particulaire (POM) lors du déclin de la floraison planctonique (diminution des ratios POC:PON, POC:POP,POC:BSi et hausse du ratio BSi:PON). Ces résultats suggèrent que pour l’estuaire maritime du Saint-Laurent, le réchauffement pourrait entraîner des changements stœchiométriques au sein de la POM avec des conséquences probables pour les niveaux trophiques supérieurs et la pompe biologique.

Continue reading ‘Étude en mésocosmes des impacts de l’acidification et du réchauffement sur la composition élémentaire de la biomasse planctonique et le cycle de l’azote dans l’estuaire maritime du Saint-Laurent (in French)’

Elevated temperature drives kelp microbiome dysbiosis, while elevated carbon dioxide induces water microbiome disruption

Global climate change includes rising temperatures and increased pCO2 concentrations in the ocean, with potential deleterious impacts on marine organisms. In this case study we conducted a four-week climate change incubation experiment, and tested the independent and combined effects of increased temperature and partial pressure of carbon dioxide (pCO2), on the microbiomes of a foundation species, the giant kelp Macrocystis pyrifera, and the surrounding water column. The water and kelp microbiome responded differently to each of the climate stressors. In the water microbiome, each condition caused an increase in a distinct microbial order, whereas the kelp microbiome exhibited a reduction in the dominant kelp-associated order, Alteromondales. The water column microbiomes were most disrupted by elevated pCO2, with a 7.3 fold increase in Rhizobiales. The kelp microbiome was most influenced by elevated temperature and elevated temperature in combination with elevated pCO2. Kelp growth was negatively associated with elevated temperature, and the kelp microbiome showed a 5.3 fold increase Flavobacteriales and a 2.2 fold increase alginate degrading enzymes and sulfated polysaccharides. In contrast, kelp growth was positively associated with the combination of high temperature and high pCO2 ‘future conditions’, with a 12.5 fold increase in Planctomycetales and 4.8 fold increase in Rhodobacteriales. Therefore, the water and kelp microbiomes acted as distinct communities, where the kelp was stabilizing the microbiome under changing pCO2 conditions, but lost control at high temperature. Under future conditions, a new equilibrium between the kelp and the microbiome was potentially reached, where the kelp grew rapidly and the commensal microbes responded to an increase in mucus production.

Continue reading ‘Elevated temperature drives kelp microbiome dysbiosis, while elevated carbon dioxide induces water microbiome disruption’

Increasing use of human-dominated habitats as CO2 emissions warm and acidify oceans

Urban and artificial structures are increasingly added to the world’s coasts during a time in which changing climate is forecast to drive shifts in naturally occurring habitats. We ask whether the role of artificial structures as marine habitats will increase in importance relative to their natural counterparts, particularly as natural habitats are negatively affected by ocean warming and acidification. To evaluate this model, we contrasted use of natural (kelp forest and turfing algae) and artificial habitat (plastic pier-piling) by a nest-building amphipod (Cymadusa pemptos) under current and future climate conditions of CO2 and temperature. Under future conditions, amphipod populations in mesocosms increased, but this did not lead to greater proportional colonization of kelp and turf. Instead, colonization doubled in artificial habitats, and there was increasing production and occupation of nests on artificial habitats relative to natural habitats. In an age when human modification of natural substrata is increasingly cited as an agent of wildlife decline, understanding the future role of artificial habitats as replacement dwellings for natural habitats is critical. We pioneer an understanding of the future role of natural and artificial habitats, identifying the possibility that the role of urban structures as marine habitats may only increase.

Continue reading ‘Increasing use of human-dominated habitats as CO2 emissions warm and acidify oceans’

Plankton responses to ocean acidification: the role of nutrient limitation

Highlights

• Ocean acidification increases phytoplankton standing stock.
• This increase is more pronounced in smaller-sized taxa.
• Primary consumers reac differently depending on nutrient availability.
• Bacteria and micro-heterotrophs benefited under limiting conditions.
• In general, heterotrophs are negatively affected at nutrient replete periods.

Abstract

In situ mesocosm experiments on the effect of ocean acidification (OA) are an important tool for investigating potential OA-induced changes in natural plankton communities. In this study we combined results from various in-situ mesocosm studies in two different ocean regions (Arctic and temperate waters) to reveal general patterns of plankton community shifts in response to OA and how these changes are modulated by inorganic nutrient availability. Overall, simulated OA caused an increase in phytoplankton standing stock, which was more pronounced in smaller-sized taxa. This effect on primary producers was channelled differently into heterotroph primary consumers depending on the inorganic nutrient availability. Under limiting conditions, bacteria and micro-heterotrophs benefited with inconsistent responses of larger heterotrophs. During nutrient replete periods, heterotrophs were in general negatively affected, although there was an increase of some mesozooplankton developmental stages (i.e. copepodites). We hypothesize that changes in phytoplankton size distribution and community composition could be responsible for these food web responses.

Continue reading ‘Plankton responses to ocean acidification: the role of nutrient limitation’

Using a mesocosm approach to evaluate marine benthic assemblage alteration associated with CO2 enrichment in coastal environments

Highlights

  • The effects of CO2 enrichment in marine macrobenthic communities were assessed.
  • Acidification showed low variation in the concentrations of metals in the sediment.
  • Significant decrease in the biological indices was reveled related to the lowest pH.
  • The contamination and pH reduction can interfere in the benthic community indices.

Abstract

The effects of acidification related to the CO2 enrichment in the coastal environments on marine macrobenthic abundance, diversity and richness were analyzed in a medium- term (21 days) using mesocosm experiments. Two sampling sites located in the Bay of Cadiz – SW, Spain were selected and tested at pH values ranged from 7.9 to 6.0 (± 0.1). Moreover, variations in the concentrations of metals in the sediment samples were analyzed at the end of each experiment. The results showed low variation in the concentrations of metals in the sediment among the pH treatments. A significant decrease (p < 0.05) in the abundance, diversity and richness of assemblages were measured between the control and the lowest pH level in both sampling sites tested in this study (Rio San Pedro and El Trocadero). The majority of species were found in all samples except in pH 6.0 which only two species were found (Hydrobia ulvae and Scrobicularia plana,) in Rio San Pedro sediment fauna. In general, the results of cluster analysis showed 60% and 40% similarity in all replicated tests in El Trocadero and Rio San Pedro of sediment fauna, respectively. The results of the Principal Component Analysis (PCA) showed that both sediment parameters and pH reduction can interfere in the benthic assemblage indices. Although the assemblages’ indices have shown decreases only in the lower pHs, the organisms also could be impacted by chronic effects. Therefore, the extension of this study is important in order to improve the knowledge about the risks associated with CO2 enrichment in on marine organisms.

Continue reading ‘Using a mesocosm approach to evaluate marine benthic assemblage alteration associated with CO2 enrichment in coastal environments’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book