Posts Tagged 'morphology'

Effects of elevated CO2 on growth, calcification, and spectral dependence of photoinhibition in the coccolithophore Emiliania huxleyi (Prymnesiophyceae)

We studied the effects of elevated CO2 concentrations on cell growth, calcification, and spectral variation in the sensitivity of photosynthesis to inhibition by solar radiation in the globally important coccolithophore Emiliania huxleyi. Growth rates and chlorophyll a content per cell showed no significant differences between elevated (800 ppmv) and ambient (400 ppmv) CO2 conditions. However, the production of organic carbon and the cell quotas for both carbon and nitrogen, increased under elevated CO2 conditions, whilst particulate inorganic carbon production rates decreased under the same conditions. Biometric analyses of cells showed that coccoliths only presented significant differences due to treatments in the central area width. Most importantly, the size of the coccosphere decreased under elevated CO2 conditions. The susceptibility of photosynthesis to inhibition by ultraviolet radiation (UVR) was estimated using biological weighting functions (BWFs) and a model that predicts photosynthesis under photosynthetically active radiation and UVR exposures. BWF results demonstrated that the sensitivity of photosynthesis to UVR was not significantly different between E. huxleyi cells grown under elevated and present CO2 concentrations. We propose that the acclimation to elevated CO2 conditions involves a physiological mechanism of regulation and allocation of energy and metabolites in the cell, which is also responsible for altering the sensitivity to UVR. In coccolithophores, this mechanism might be affected by the decrease in the calcification rates.

Continue reading ‘Effects of elevated CO2 on growth, calcification, and spectral dependence of photoinhibition in the coccolithophore Emiliania huxleyi (Prymnesiophyceae)’

The potential impact of underwater exhausted CO2 from innovative ships on invertebrate communities

Liquefied natural gas (LNG) powered ships equipped with an underwater exhaust system to reduce the ship’s water resistance could form a future generation of energy-efficient ships. The potential consequences of the underwater exhaust gas to the local ecosystems are still unknown. Especially, the CO2 levels may locally exceed estimated future global levels. The present study exposes marine communities to a wide range of CO2 dosages, resulting in pH 8.6–5.8 that was remained for 49 days. We found that the zooplankton and benthic community were adversely affected by high CO2 exposure levels. In detail, (1) between pH 6.6 and 7.1 polychaete worms became the dominating group of the benthic community and their larvae dominated the zooplankton group. (2) Due to the reduced grazing pressure and the flux of nutrients from decaying organic material planktonic microalgae (phytoplankton) stared blooming at the highest exposure level. The periphyton (fouling microalgae) community was not able to take advantage under these conditions. (3) Marine snails’ (periwinkle) shell damage and high mortality were observed at pH < 6.6. However, the growth of the surviving periwinkles was not directly related to pH, but was positively correlated with the availability of periphyton and negatively correlated with the polychaete worm density that most likely also used the periphyton as food source. Our result indicates that the impact of underwater exhaust gasses depends on various factors including local biological and abiotic conditions, which will be included in future research.

Continue reading ‘The potential impact of underwater exhausted CO2 from innovative ships on invertebrate communities’

Biomonitoring acidification using marine gastropods

Highlights

• Data loggers offer limited coverage of acidification in marine ecosystems.

• Intertidal water pH was reflected in organismal attributes of gastropods.

• Shell surface erosion presents a clear estimate of corrosive water exposure.

• Gastropod biomonitoring can identify coastal areas of more or lesser acidification.

Abstract

Ocean acidification is mainly being monitored using data loggers which currently offer limited coverage of marine ecosystems. Here, we trial the use of gastropod shells to monitor acidification on rocky shores. Animals living in areas with highly variable pH (8.6–5.9) were compared with those from sites with more stable pH (8.6–7.9). Differences in site pH were reflected in size, shape and erosion patterns in Nerita chamaeleon and Planaxis sulcatus. Shells from acidified sites were shorter, more globular and more eroded, with both of these species proving to be good biomonitors. After an assessment of baseline weathering, shell erosion can be used to indicate the level of exposure of organisms to corrosive water, providing a tool for biomonitoring acidification in heterogeneous intertidal systems. A shell erosion ranking system was found to clearly discriminate between acidified and reference sites. Being spatially-extensive, this approach can identify coastal areas of greater or lesser acidification. Cost-effective and simple shell erosion ranking is amenable to citizen science projects and could serve as an early-warning-signal for natural or anthropogenic acidification of coastal waters.

Continue reading ‘Biomonitoring acidification using marine gastropods’

Ocean acidification has little effect on the biochemical composition of the coccolithophore Emiliania huxleyi

Owing to the hierarchical organization of biology, from genomes over transcriptomes and proteomes down to metabolomes, there is continuous debate about the extent to which data and interpretations derived from one level, e.g. the transcriptome, are in agreement with other levels, e.g. the metabolome. Here, we tested the effect of ocean acidification (OA; 400 vs. 1000 μatm CO2) and its modulation by light intensity (50 vs. 300 μmol photons m-2 s-1) on the biomass composition (represented by 75 key metabolites) of diploid and haploid life-cycle stages of the coccolithophore Emiliania huxleyi (RCC1216 and RCC1217) and compared these data with interpretations from previous physiological and gene expression screenings. The metabolite patterns showed minor responses to OA in both life-cycle stages. Whereas previous gene expression analyses suggested that the observed increased biomass buildup derived from lipid and carbohydrate storage, this dataset suggests that OA slightly increases overall biomass of cells, but does not significantly alter their metabolite composition. Generally, light was shown to be a more dominant driver of metabolite composition than OA, increasing the relative abundances of amino acids, mannitol and storage lipids, and shifting pigment contents to accommodate increased irradiance levels. The diploid stage was shown to contain vastly more osmolytes and mannitol than the haploid stage, which in turn had a higher relative content of amino acids, especially aromatic ones. Besides the differences between the investigated cell types and the general effects on biomass buildup, our analyses indicate that OA imposes only negligible effects on E. huxleyi´s biomass composition.

Continue reading ‘Ocean acidification has little effect on the biochemical composition of the coccolithophore Emiliania huxleyi’

Cryptic genetic variation underpins rapid adaptation to ocean acidification

Global climate change has intensified the need to assess the capacity for natural populations to adapt to abrupt shifts in the environment. Reductions in seawater pH constitute a conspicuous stressor associated with increasing atmospheric carbon dioxide that is affecting ecosystems throughout the world’s oceans. Here, we quantify the phenotypic and genetic modifications associated with rapid adaptation to reduced seawater pH in the marine mussel, Mytilus galloprovincialis. We reared a genetically diverse larval population in ambient and extreme low pH conditions (pHT 8.1 and 7.4) and tracked changes in the larval size and allele frequency distributions through settlement. Additionally, we separated larvae by size to link a fitness-related trait to its underlying genetic background in each treatment. Both phenotypic and genetic data show that M. galloprovincialis can evolve in response to a decrease in seawater pH. This process is polygenic and characterized by genotype-environment interactions, suggesting the role of cryptic genetic variation in adaptation to future climate change. Holistically, this work provides insight into the processes underpinning rapid evolution, and demonstrates the importance of maintaining standing variation within natural populations to bolster species’ adaptive capacity as global change progresses.

Continue reading ‘Cryptic genetic variation underpins rapid adaptation to ocean acidification’

A future 1.2 °C increase in ocean temperature alters the quality of mangrove habitats for marine plants and animals

Highlights
• Mangrove habitats are more resilient to climate change than other habitats.

• Climate change might have positive effects on mangrove-root species communities.

• Using mesocosms we show that an increase of 1.2 °C leads to community homogenisation.

• Warming also led to diversity loss and flattening of mangrove root epibiont communities.

• Juvenile fish altered their use of mangrove habitats under warming and acidification.

Abstract
Global climate stressors, like ocean warming and acidification, contribute to the erosion of structural complexity in marine foundation habitats by promoting the growth of low-relief turf, increasing grazing pressure on structurally complex marine vegetation, and by directly affecting the growth and survival of foundation species. Because mangrove roots are woody and their epibionts are used to ever-changing conditions in highly variable environments, mangrove habitats may be more resilient to global change stressors than other marine foundation species. Using a large-scale mesocosm experiment, we examined how ocean warming and acidification, under a reduced carbon emission scenario, affect the composition and structural complexity of mangrove epibiont communities and the use of mangrove habitat by juvenile fishes. We demonstrate that even a modest increase in seawater temperature of 1.2 °C leads to the homogenisation and flattening of mangrove root epibiont communities. Warming led to a 24% increase in the overall cover of algal epibionts on roots but the diversity of the epibiont species decreased by 33%. Epibiont structural complexity decreased owing to the shorter stature of weedy algal turfs which prospered under elevated temperature. Juvenile fishes showed alterations in mangrove habitat use with ocean warming and acidification, but these were independent of changes to the root epibiont community. We reveal that the quality of apparently resilient mangrove habitats and their perceived value as habitat for associated fauna are still vulnerable under a globally reduced carbon emission scenario.

Continue reading ‘A future 1.2 °C increase in ocean temperature alters the quality of mangrove habitats for marine plants and animals’

How calorie-rich food could help marine calcifiers in a CO2-rich future

Increasing carbon emissions not only enrich oceans with CO2 but also make them more acidic. This acidifying process has caused considerable concern because laboratory studies show that ocean acidification impairs calcification (or shell building) and survival of calcifiers by the end of this century. Whether this impairment in shell building also occurs in natural communities remains largely unexplored, but requires re-examination because of the recent counterintuitive finding that populations of calcifiers can be boosted by CO2 enrichment. Using natural CO2 vents, we found that ocean acidification resulted in the production of thicker, more crystalline and more mechanically resilient shells of a herbivorous gastropod, which was associated with the consumption of energy-enriched food (i.e. algae). This discovery suggests that boosted energy transfer may not only compensate for the energetic burden of ocean acidification but also enable calcifiers to build energetically costly shells that are robust to acidified conditions. We unlock a possible mechanism underlying the persistence of calcifiers in acidifying oceans.

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