Posts Tagged 'BRcommunity'

Ecological responses to ocean acidification by developing marine fouling communities

Increasing levels of CO2 in the atmosphere are rapidly affecting ocean chemistry, leading to increased acidification (i.e., decreased pH) and reductions in calcium carbonate saturation state. This phenomenon, known as ocean acidification, poses a serious imminent threat to marine species, especially those that use calcium carbonate. In this dissertation, I use a variety of methods (field-based experiments, surveys, meta-analysis) to understand how marine communities respond to both natural and experimental CO2 enrichment and how responses could be shaped by species interactions or food availability. I found that ocean acidification influenced community assembly, recruitment, and succession to create homogenized, low diversity communities. I found broadly that soft-bodied, weedy taxa (e.g., algae and ascidians) had an advantage in acidified conditions and outcompeted heavily calcified taxa (e.g., mussels, serpulids) that were more vulnerable to the effects of acidification, although calcified bryozoans and barnacles exhibited mixed responses. Next, I examined an important hypothesis of context dependency in ocean acidification research: that negative responses by calcifiers to high CO2 could be reduced by higher energy input. I found little support for this hypothesis for species growth and abundance, and in fact found that, for some species, additional food supply exacerbated or brought out the negative effects of CO2. Further, I found that acidification stress can tip the balance of community composition towards invasion, under resource conditions that enabled the native community to resist invasions. Overall, it is clear that acidification is a strong driving force in marine communities but understanding the underlying energetic and competitive context is essential to predicting climate change responses.

Continue reading ‘Ecological responses to ocean acidification by developing marine fouling communities’

Dimethylsulfide (DMS) production in polar oceans may be resilient to ocean acidification

Emissions of dimethylsulfide (DMS) from the polar oceans play a key role in atmospheric processes and climate. Therefore, it is important we increase our understanding of how DMS production in these regions may respond to environmental change. The polar oceans are particularly vulnerable to ocean acidification (OA). However, our understanding of the polar DMS response is limited to two studies conducted in Arctic waters, where in both cases DMS concentrations decreased with increasing acidity. Here, we report on our findings from seven summertime shipboard microcosm experiments undertaken in a variety of locations in the Arctic Ocean and Southern Ocean. These experiments reveal no significant effects of short term OA on the net production of DMS by planktonic communities. This is in contrast to identical experiments from temperate NW European shelf waters where surface ocean communities responded to OA with significant increases in dissolved DMS concentrations. A meta-analysis of the findings from both temperate and polar waters (n = 18 experiments) reveals clear regional differences in the DMS response to OA. We suggest that these regional differences in DMS response reflect the natural variability in carbonate chemistry to which the respective communities may already be adapted. Future temperate oceans could be more sensitive to OA resulting in a change in DMS emissions to the atmosphere, whilst perhaps surprisingly DMS emissions from the polar oceans may remain relatively unchanged. By demonstrating that DMS emissions from geographically distinct regions may vary in response to OA, our results may facilitate a better understanding of Earth’s future climate. Our study suggests that the way in which processes that generate DMS respond to OA may be regionally distinct and this should be taken into account in predicting future DMS emissions and their influence on Earth’s climate.

Continue reading ‘Dimethylsulfide (DMS) production in polar oceans may be resilient to ocean acidification’

Resilience by diversity: large intraspecific differences in climate change responses of an Arctic diatom

The potential for adaptation of phytoplankton to future climate is often extrapolated based on single strain responses of a representative species, ignoring variability within and between species. The aim of this study was to approximate the range of strain-specific reaction patterns within an Arctic diatom population, which selection can act upon. In a laboratory experiment, we first incubated natural communities from an Arctic fjord under present and future conditions. In a second step, single strains of the diatom Thalassiosira hyalina were isolated from these selection environments and exposed to a matrix of temperature (3°C and 6°C) and pCO2 levels (180 μatm, 370 μatm, 1000 μatm, 1400 μatm) to establish reaction norms for growth, production rates, and elemental quotas. The results revealed interactive effects of temperature and pCO2 as well as wide tolerance ranges. Between strains, however, sensitivities and optima differed greatly. These strain-specific responses corresponded well with their respective selection environments of the previous community incubation. We therefore hypothesize that intraspecific variability and the selection between coexisting strains may pose an underestimated source of species’ plasticity. Thus, adaptation of phytoplankton assemblages may also occur by selection within rather than only between species, and species-wide inferences from single strain experiments should be treated with caution.

Continue reading ‘Resilience by diversity: large intraspecific differences in climate change responses of an Arctic diatom’

Do increasing CO2 concentration impacted on changing phytoplankton assemblages?

The effect of seawater pCO2 concentration of 280, 380, 550, 650, 750 and 1000 ppm on the changing of phytoplankton assemblage was determined through a mesocosm experiment at the Barrang Lompo Island. The experiment was run for 48 and 96 hours without nutrient enrichment. The aim of the study is to examine the effect of the increasing CO2 concentration on the changing phytoplankton assemblages. The result showed that Bacillariophyceae has been the most important algal group accounting for 74.5% for 48 hours of incubation period. Moreover, Diatomaceae was the most dominant algal group for 96 hours of the incubation period, accounting for 50.9%. There was no clear trend of Shannon diversity (H’) and the evenness values between CO2 concentration and incubation period. There was a clear grouping of species assemblages between the incubation periods. ANOSIM result showed that there is no significant difference in species assemblage among CO2 treatments. On the other hand, a significant difference in species assemblage between incubation periods between CO2 concentration treatments was observed. The three taxa that are most responsible for the dissimilarity were Rhizosolenia fragilissima (10.1%), Gyrosigma acuminatum (9.3%), and Biddulphia sinensis (9.2%).
Continue reading ‘Do increasing CO2 concentration impacted on changing phytoplankton assemblages?’

Impact of ocean acidification and warming on the productivity of a rock pool community


• Fleshy algae drive the response of assemblages.
• The response of coralline algae to global change depend on the season.
• Rock pool assemblages are robust to ocean acidification and warming.


This study examined experimentally the combined effect of ocean acidification and warming on the productivity of rock pool multi-specific assemblages, composed of coralline algae, fleshy algae, and grazers. Natural rock pool communities experience high environmental fluctuations. This may confer physiological advantage to rock pool communities when facing predicted acidification and warming. The effect of ocean acidification and warming have been assessed at both individual and assemblage level to examine the importance of species interactions in the response of assemblages. We hypothesized that rock pool assemblages have physiological advantage when facing predicted ocean acidification and warming. Species exhibited species-specific responses to increased temperature and pCO2. Increased temperature and pCO2 have no effect on assemblage photosynthesis, which was mostly influenced by fleshy algal primary production. The response of coralline algae to ocean acidification and warming depended on the season, which evidenced the importance of physiological adaptations to their environment in their response to climate change. We suggest that rock pool assemblages are relatively robust to changes in temperature and pCO2, in terms of primary production.

Continue reading ‘Impact of ocean acidification and warming on the productivity of a rock pool community’

CO2 leakage alters biogeochemical and ecological functions of submarine sands

Subseabed CO2 storage is considered a future climate change mitigation technology. We investigated the ecological consequences of CO2 leakage for a marine benthic ecosystem. For the first time with a multidisciplinary integrated study, we tested hypotheses derived from a meta-analysis of previous experimental and in situ high-CO2 impact studies. For this, we compared ecological functions of naturally CO2-vented seafloor off the Mediterranean island Panarea (Tyrrhenian Sea, Italy) to those of nonvented sands, with a focus on biogeochemical processes and microbial and faunal community composition. High CO2 fluxes (up to 4 to 7 mol CO2 m−2 hour−1) dissolved all sedimentary carbonate, and comigration of silicate and iron led to local increases of microphytobenthos productivity (+450%) and standing stocks (+300%). Despite the higher food availability, faunal biomass (−80%) and trophic diversity were substantially lower compared to those at the reference site. Bacterial communities were also structurally and functionally affected, most notably in the composition of heterotrophs and microbial sulfate reduction rates (−90%). The observed ecological effects of CO2 leakage on submarine sands were reproduced with medium-term transplant experiments. This study assesses indicators of environmental impact by CO2 leakage and finds that community compositions and important ecological functions are permanently altered under high CO2.

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Physiological stress response associated with elevated CO2 and dissolved iron in a phytoplankton community dominated by the coccolithophore Emiliania huxleyi

We exposed a natural phytoplankton community to combined present (390 µatm, low carbon [LC]) and future CO2 levels predicted for the year 2100 (900 µatm, high carbon [HC]), and ambient (4.5 nM, -DFB [desferoxamine B]) and high (12 nM, +DFB) dissolved iron (dFe) levels, for 25 d in mesocosms. We report on the physiological response of the community dominated by the coccolithophore Emiliania huxleyi. The community structure shifted on Day 10, leading to 2 different phases (1 and 2), i.e. before and after Day 10, respectively. We focussed on the massive bloom of E. huxleyi that developed in Phase 2, in the LC+DFB treatment. In high dFe conditions, pigments and photosynthetic parameters increased compared to the control (LC-DFB). Cell death was only detected during the community shift (Days 10-12) and mostly increased in the presence of high CO2. The accumulation of reactive oxygen species (ROS) decreased under high dFe, pointing to an efficient, rather than a stressed, metabolism. DNA lesions, caused by excess irradiance, were minimised under high Fe. E. huxleyi is known for its low Fe requirements for growth. However, we demonstrate that Fe is essential to E. huxleyi for DNA repair and ROS management, and to maintain optimal functioning of the photosynthetic machinery, with implications for carbon cycling and future ecosystem functioning.

Continue reading ‘Physiological stress response associated with elevated CO2 and dissolved iron in a phytoplankton community dominated by the coccolithophore Emiliania huxleyi’

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Ocean acidification in the IPCC AR5 WG II

OUP book