Posts Tagged 'adaptation'

Ocean acidification increases larval swimming speed and has limited effects on spawning and settlement of a robust fouling bryozoan, Bugula neritina

Few studies to date have investigated the effects of ocean acidification on non-reef forming marine invertebrates with non-feeding larvae. Here, we exposed adults of the bryozoan Bugula neritina and their larvae to lowered pH. We monitored spawning, larval swimming, settlement, and post-settlement individual sizes at two pHs (7.9 vs. 7.6) and settlement dynamics alone over a broader pH range (8.0 down to 6.5). Our results show that spawning was not affected by adult exposure (48 h at pH 7.6), larvae swam 32% faster and the newly-settled individuals grew significantly larger (5%) at pH 7.6 than in the control. Although larvae required more time to settle when pH was lowered, reduced pH was not lethal, even down to pH 6.5. Overall, this fouling species appeared to be robust to acidification, and yet, indirect effects such as prolonging the pelagic larval duration could increase predation risk, and might negatively impact population dynamics.

Continue reading ‘Ocean acidification increases larval swimming speed and has limited effects on spawning and settlement of a robust fouling bryozoan, Bugula neritina’

Species-specific responses to ocean acidification should account for local adaptation and adaptive plasticity

Global stressors, such as ocean acidification, constitute a rapidly emerging and significant problem for marine organisms, ecosystem functioning and services. The coastal ecosystems of the Humboldt Current System (HCS) off Chile harbour a broad physical–chemical latitudinal and temporal gradient with considerable patchiness in local oceanographic conditions. This heterogeneity may, in turn, modulate the specific tolerances of organisms to climate stress in species with populations distributed along this environmental gradient. Negative response ratios are observed in species models (mussels, gastropods and planktonic copepods) exposed to changes in the partial pressure of CO2 (pCO2) far from the average and extreme pCO2 levels experienced in their native habitats. This variability in response between populations reveals the potential role of local adaptation and/or adaptive phenotypic plasticity in increasing resilience of species to environmental change. The growing use of standard ocean acidification scenarios and treatment levels in experimental protocols brings with it a danger that inter-population differences are confounded by the varying environmental conditions naturally experienced by different populations. Here, we propose the use of a simple index taking into account the natural pCO2 variability, for a better interpretation of the potential consequences of ocean acidification on species inhabiting variable coastal ecosystems. Using scenarios that take into account the natural variability will allow  understanding of the limits to plasticity across organismal traits, populations and species.

Continue reading ‘Species-specific responses to ocean acidification should account for local adaptation and adaptive plasticity’

Functional genomic analysis of corals from natural CO2-seeps reveal core molecular responses involved in acclimatization to ocean acidification

Little is known about the potential for acclimatization or adaptation of corals to ocean acidification and even less about the molecular mechanisms underpinning these processes. Here we examine global gene expression patterns in corals and their intracellular algal symbionts from two replicate population pairs in Papua New Guinea that have undergone long-term acclimatization to natural variation in pCO2. In the coral host, only 61 genes were differentially expressed in response to pCO2 environment, but the pattern of change was highly consistent between replicate populations, likely reflecting the core expression homeostasis response to ocean acidification. Functional annotations highlight lipid metabolism and a change in the stress response capacity of corals as a key part of this process. Specifically, constitutive downregulation of molecular chaperones was observed, which may impact response to combined climate-change related stressors. Elevated CO2 has been hypothesized to benefit photosynthetic organisms but expression changes of in hospite Symbiodinium in response to acidification were greater and less consistent among reef populations. This population-specific response suggests hosts may need to adapt not only to an acidified environment, but also to changes in their Symbiodinium populations that may not be consistent among environments. This process adds another challenging dimension to the physiological process of coping with climate change.

Continue reading ‘Functional genomic analysis of corals from natural CO2-seeps reveal core molecular responses involved in acclimatization to ocean acidification’

Iron availability modulates the effects of future CO2 levels within the marine planktonic food web

Ocean acidification (OA) due to increased anthropogenic CO2 emissions is affecting marine ecosystems at an unprecedented rate, altering biogeochemical cycles. Direct empirical studies on natural communities are required to analyse the interactive effects of multiple stressors while spanning multiple trophic levels. We investigated the interactive effects of changes in CO2 and iron availability on functional plankton groups. We used mesocosms manipulating the carbonate system from the start to achieve present (low concentration, LC) and predicted future pCO2 levels (high concentration, HC). To manipulate dissolved iron (dFe), half of the mesocosms were amended with 70 nM (final concentration) of the siderophore desferoxamine B (DFB) on Day 7 (+DFB and -DFB treatments). Manipulation of both CO2 and DFB increased dFe compared to the control. During the 22 experimental days, the plankton community structure showed 2 distinct phases. In phase 1 (Days 1-10), only bacterioplankton abundances increased at elevated pCO2. In contrast, a strong community response was evident in phase 2 (Days 11-22) due to DFB addition. Biomass of the coccolithophore Emiliania huxleyi increased massively at LC+DFB. HC negatively affected E. huxleyi and Synechococcus sp., and high dFe (+DFB) had a positive effect on both. The rest of the plankton community was unaffected by the treatments. Increased dFe partially mitigated the negative effect of HC imposed on the coccolithophores, indicating that E. huxleyi was able to acclimate better to OA. This physiological iron-mediated acclimation can diminish the deleterious effects of OA on carbon export and the rain ratio, thus affecting food web dynamics and future ecosystem functioning.

Continue reading ‘Iron availability modulates the effects of future CO2 levels within the marine planktonic food web’

Response and adaptation to climate change in the South China Sea and Coral Sea

Over the past decades, climate change in the tropical western Pacific has led to surface warming, a distinct decrease in sea surface salinity, obvious sea level rise (SLR), and ocean acidification in the South China Sea (SCS) and Coral Sea (CS), which have had profound impacts on marine ecosystems and coastal communities. The aim of this study is to examine and compare the extent of marine climate change in these two areas, and to summarize possible adaptations in response to climate change. Our results indicate that a fast rise in sea surface temperature (SST) at a rate of more than 0.07 °C decade−1 and a decrease in sea surface salinity (SSS) at a rate of more than −0.09 g kg−1 decade−1 appeared in the SCS, which are greater than that in the CS, although SST changes also show a plateau consistent with the global warming hiatus since 2000. As a proxy for marine productivity, concentrations of chlorophyll-a apparently varied with the SSS and SST changes in the two areas. Our findings suggest that marine ecosystem functions have been greatly affected by climate change through changes in tropical evaporation and rainfall. Meanwhile, persistent SLR and ocean acidification pose serious threats to low-lying coastal areas, small islands, coral-dominated reef ecosystems, and related subsistence fisheries. The sustainable development of communities in low-lying coastal zones and small islands faces significant future challenge. Adaptation strategies for mitigating the effects of climate changes need to be developed and put forward.

Continue reading ‘Response and adaptation to climate change in the South China Sea and Coral Sea’

Intra-population variability of ocean acidification impacts on the physiology of Baltic blue mussels (Mytilus edulis): integrating tissue and organism response

Increased maintenance costs at cellular, and consequently organism level, are thought to be involved in shaping the sensitivity of marine calcifiers to ocean acidification (OA). Yet, knowledge of the capacity of marine calcifiers to undergo metabolic adaptation is sparse. In Kiel Fjord, blue mussels thrive despite periodically high seawater PCO2, making this population interesting for studying metabolic adaptation under OA. Consequently, we conducted a multi-generation experiment and compared physiological responses of F1 mussels from ‘tolerant’ and ‘sensitive’ families exposed to OA for 1 year. Family classifications were based on larval survival; tolerant families settled at all PCO2 levels (700, 1120, 2400 µatm) while sensitive families did not settle at the highest PCO2 (≥99.8% mortality). We found similar filtration rates between family types at the control and intermediate PCO2 level. However, at 2400 µatm, filtration and metabolic scope of gill tissue decreased in tolerant families, indicating functional limitations at the tissue level. Routine metabolic rates (RMR) and summed tissue respiration (gill and outer mantle tissue) of tolerant families were increased at intermediate PCO2, indicating elevated cellular homeostatic costs in various tissues. By contrast, OA did not affect tissue and routine metabolism of sensitive families. However, tolerant mussels were characterised by lower RMR at control PCO2 than sensitive families, which had variable RMR. This might provide the energetic scope to cover increased energetic demands under OA, highlighting the importance of analysing intra-population variability. The mechanisms shaping such difference in RMR and scope, and thus species’ adaptation potential, remain to be identified.

Continue reading ‘Intra-population variability of ocean acidification impacts on the physiology of Baltic blue mussels (Mytilus edulis): integrating tissue and organism response’

Evolutionary genomics of the cold-adapted diatom Fragilariopsis cylindrus

The Southern Ocean houses a diverse and productive community of organisms. Unicellular eukaryotic diatoms are the main primary producers in this environment, where photosynthesis is limited by low concentrations of dissolved iron and large seasonal fluctuations in light, temperature and the extent of sea ice. How diatoms have adapted to this extreme environment is largely unknown. Here we present insights into the genome evolution of a cold-adapted diatom from the Southern Ocean, Fragilariopsis cylindrus, based on a comparison with temperate diatoms. We find that approximately 24.7 per cent of the diploid F. cylindrus genome consists of genetic loci with alleles that are highly divergent (15.1 megabases of the total genome size of 61.1 megabases). These divergent alleles were differentially expressed across environmental conditions, including darkness, low iron, freezing, elevated temperature and increased CO2. Alleles with the largest ratio of non-synonymous to synonymous nucleotide substitutions also show the most pronounced condition-dependent expression, suggesting a correlation between diversifying selection and allelic differentiation. Divergent alleles may be involved in adaptation to environmental fluctuations in the Southern Ocean.

Continue reading ‘Evolutionary genomics of the cold-adapted diatom Fragilariopsis cylindrus’


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Ocean acidification in the IPCC AR5 WG II

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