Posts Tagged 'biological response'



Target gene expression studies on Platynereis dumerilii and Platynereis cfr massiliensis at the shallow CO2 vents off Ischia, Italy

Many studies predict negative effects of ocean acidification on marine organisms, potentially leading to loss of biodiversity and ecosystem function. Research on species inhabiting naturally high pCO2 environments, such as volcanic CO2 vents, offers an opportunity to understand the molecular mechanisms involved in high pCO2 regulation. Here we investigate the relative expression of NADH dehydrogenase, sodium-hydrogen antiporter (NHE), carbonic anhydrase (CA) and paramyosin genes from two non-calcifying sibling Nereididae polychaetes species, Platynereis cfr massiliensis, collected in the shallow CO2 vents off Ischia (Italy; 40°43′52.0″N 13°57′46.2″E and 40°43′55.5″N 13°57′48.4″E), and P. dumerilii collected in an area nearby (40°43′34.51″N; 13°57′35.7″E). The origin of the worms was confirmed using restriction enzyme digest. NHE and paramyosin expressions were both significantly increased in P. dumerilii relative to the P. cfr massiliensis vent populations. Furthermore, a seven day laboratory transfer experiment to lower/higher pCO2 conditions was conducted to investigate the effects on the short term gene expression. The transfer experiment of the non-vent worms to high pCO2 conditions showed no significant effect on any of the genes analysed, however, two genes (NADH dehydrogenase and NHE) from worms of the vent population were significantly down-regulated under low pCO2. These findings will help to gain further insights into the cellular mechanisms affected by pCO2 changes in two polychaete species.

Continue reading ‘Target gene expression studies on Platynereis dumerilii and Platynereis cfr massiliensis at the shallow CO2 vents off Ischia, Italy’

Natural ocean acidification at Papagayo upwelling system (North Pacific Costa Rica): implications for reef development

Numerous experiments have shown that ocean acidification impedes coral calcification, but knowledge about in situ reef ecosystem response to ocean acidification is still scarce. Bahía Culebra, situated at the northern Pacific coast of Costa Rica, is a location naturally exposed to acidic conditions due to the Papagayo seasonal upwelling. We measured pH and pCO2 in situ during two non-upwelling seasons (June 2012, May–June 2013), with a high temporal resolution of every 15 and 30 min, respectively, using two Submersible Autonomous Moored Instruments (SAMI-pH, SAMI-CO2). These results were compared with published data from the upwelling season 2009. Findings revealed that the carbonate system in Bahía Culebra shows a high temporal variability. Incoming offshore waters drive inter- and intra-seasonal changes. Lowest pH (7.8) and highest pCO2 (658.3 µatm) values measured during a cold-water intrusion event in the non-upwelling season were similar to those minimum values reported from upwelling season (pH = 7.8, pCO2 = 643.5 µatm), unveiling that natural acidification occurs sporadically also in non-upwelling season. This affects the interaction of photosynthesis, respiration, calcification, and carbonate dissolution and the resulting diel cycle of pH and pCO2 in the reefs of Bahía Culebra. During non-upwelling season, the aragonite saturation state (Ωa) rises to values of > 3.3 and enhances calcification. Aragonite saturation state values during upwelling season falls below 2.5, hampering calcification and coral growth. Low reef accretion in Bahía Culebra indicates high erosion rates and that these reefs grow on the verge of their ecological tolerance. The Ωa threshold values for coral growth, derived from the correlation between Ωa and coral linear extension rates, suggest that future ocean acidification will threaten reefs in Bahía Culebra. These data contribute to build a better understanding of the carbonate system dynamics and coral reefs key response (e.g. coral growth) to natural low-pH conditions, in upwelling areas in the Eastern Tropical Pacific and beyond.

Continue reading ‘Natural ocean acidification at Papagayo upwelling system (North Pacific Costa Rica): implications for reef development’

Environmental controls on modern scleractinian coral and reef-scale calcification

Modern reef-building corals sustain a wide range of ecosystem services because of their ability to build calcium carbonate reef systems. The influence of environmental variables on coral calcification rates has been extensively studied, but our understanding of their relative importance is limited by the absence of in situ observations and the ability to decouple the interactions between different properties. We show that temperature is the primary driver of coral colony (Porites astreoides and Diploria labyrinthiformis) and reef-scale calcification rates over a 2-year monitoring period from the Bermuda coral reef. On the basis of multimodel climate simulations (Coupled Model Intercomparison Project Phase 5) and assuming sufficient coral nutrition, our results suggest that P. astreoides and D. labyrinthiformis coral calcification rates in Bermuda could increase throughout the 21st century as a result of gradual warming predicted under a minimum CO2 emissions pathway [representative concentration pathway (RCP) 2.6] with positive 21st-century calcification rates potentially maintained under a reduced CO2 emissions pathway (RCP 4.5). These results highlight the potential benefits of rapid reductions in global anthropogenic CO2 emissions for 21st-century Bermuda coral reefs and the ecosystem services they provide.

Continue reading ‘Environmental controls on modern scleractinian coral and reef-scale calcification’

Evaluating features of periphytic diatom communities as biomonitoring tools in fresh, brackish and marine waters

Highlights

• Diversity of periphytic diatoms from freshwater, brackish water and marine sites from the same biogeographical region was assessed.
• Taxonomical parameters (life-forms, cell density, biovolume, Shannon index, species richness and % relative abundance) effectively differentiate impacted sites from less-impacted one.
• Lipid bodies and deformities in diatoms show tremendous potential to be used as a rapid early warning system for assessing the ecological health of fluvial ecosystem.

Abstract

The aims of this study were to assess the biodiversity of periphytic diatom assemblages in fresh, brackish and marine waterbodies of Korea, and to assess the effect of environmental and anthropogenic factors on parameters such as the quantity and biovolume of lipid bodies and deformations of diatoms as early warning measures of anthropogenic impact. Diatom samples were collected from 31 sites (14 freshwater, 10 brackish and 7 marine), which included less impacted (upstream) and impacted (downstream) sites in each water type. Our results showed higher abundance and biodiversity of periphytic diatoms at the less impacted sites in terms of species richness, Shannon index, cell count and biovolume of the communities than at the impacted sites for freshwater and estuarine sites, but not for marine sites. 84 diatom species were noted in freshwater, 80 in brackish water and 40 in marine waters. In comparison to diatoms of the impacted sites, those of less impacted freshwater, brackish and marine sites had less lipid bodies (also less biovolume) and a lower percentage of teratological frustules, and showed more mobile forms in the community. Principal component analysis (PCA) also showed clear segregation of impacted from less impacted sites by the extent of the presence of lipid bodies (higher both in number and biovolume) and deformities in diatom frustules. Pearson correlation analysis revealed that lipid body induction and deformities were positively correlated with metals (Cd, Co, Cr, Cu, Fe, Pb and Zn) and nutrients (total phosphorus and total nitrogen), whereas they showed negative correlation with salinity, dissolved oxygen, suspended solutes and pH. Life-forms, lipid bodies and deformities in diatoms may be an effective biomonitoring tool for assessing biological effects of pollutants in non-marine aquatic ecosystems in Korea.

Continue reading ‘Evaluating features of periphytic diatom communities as biomonitoring tools in fresh, brackish and marine waters’

Ocean acidification dampens physiological stress response to warming and contamination in a commercially-important fish (Argyrosomus regius)

Highlights

• Atmospheric and water conditions/contaminants influence animal physiology status.
• Scarcely studied multi-stressor effects were extricated via full-factorial design.
• Warming stimulated mercury accumulation, but was offset by acidification.
• Co-occurring acidification countered oxidative stress elicited by other stressors.
• Enhanced mitigation pathways or chemical dynamics may underpin stressor antagonism.

Abstract

Increases in carbon dioxide (CO2) and other greenhouse gases emissions are changing ocean temperature and carbonate chemistry (warming and acidification, respectively). Moreover, the simultaneous occurrence of highly toxic and persistent contaminants, such as methylmercury, will play a key role in further shaping the ecophysiology of marine organisms. Despite recent studies reporting mostly additive interactions between contaminant and climate change effects, the consequences of multi-stressor exposure are still largely unknown. Here we disentangled how Argyrosomus regius physiology will be affected by future stressors, by analysing organ-dependent mercury (Hg) accumulation (gills, liver and muscle) within isolated/combined warming (ΔT = 4 °C) and acidification (ΔpCO2 = 1100 μatm) scenarios, as well as direct deleterious effects and phenotypic stress response over multi-stressor contexts. After 30 days of exposure, although no mortalities were observed in any treatments, Hg concentration was enhanced under warming conditions, especially in the liver. On the other hand, elevated CO2 decreased Hg accumulation and consistently elicited a dampening effect on warming and contamination-elicited oxidative stress (catalase, superoxide dismutase and glutathione-S-transferase activities) and heat shock responses. Thus, potentially unpinned on CO2-promoted protein removal and ionic equilibrium between hydrogen and reactive oxygen species, we found that co-occurring acidification decreased heavy metal accumulation and contributed to physiological homeostasis. Although this indicates that fish can be physiologically capable of withstanding future ocean conditions, additional experiments are needed to fully understand the biochemical repercussions of interactive stressors (additive, synergistic or antagonistic).

Continue reading ‘Ocean acidification dampens physiological stress response to warming and contamination in a commercially-important fish (Argyrosomus regius)’

Future research directions and gaps in our knowledge

In this final chapter, we explore the current gaps in our understanding of ocean acidification and increased sea surface temperature on sponges and highlight some future research directions to address these gaps. We particularly focus on the geographic spread of the currently available studies, the mechanisms of acclimation and the potential for long-term adaptation. We also highlight the need for more multiple stressor impact studies and a better understanding of the ecosystem consequences of changing sponge abundance. With this information, we will be able to better predict future impacts of environmental change on sponges.

Continue reading ‘Future research directions and gaps in our knowledge’

Bioeroding sponges and the future of coral reefs

Bioeroding sponges play a central role in carbonate cycling on corals reefs. They may respond differently to habitat deterioration than many other benthic invertebrates, because at some locations, their abundances increased after disturbance. We reviewed literature on these sponges in context of environmental change and provide meta-analyses at global level. A difficult taxonomy and scarce scientific expertise leave them inadequately studied, even though they are the best-known internal bioeroders. They are sheltered within the substrate they erode, appear to be comparatively resilient against environmental change and can have heat-resistant photosymbionts and ‘weedy’ traits, including multiple pathways to reproduce or disperse and fast growth and healing abilities. Especially temperature stress appears to disable calcifiers stronger than bioeroding sponges. Moreover, increases in bioeroding sponge abundances have been related to eutrophication and disturbances that led to coral mortality. Chemical sponge bioerosion is forecast to double with doubled partial pressure of carbon dioxide, but reduced substrate density may counteract this effect, as dominant sponges erode more in denser substrates. Case examples portray shifting impacts of bioeroding sponges with environmental change, with some reefs already being erosional. Most available data and the largest known species record are from the Caribbean. Data from the Coral Triangle and India are largely restricted to faunistic records. Red Sea, Japanese and cold-water reef bioeroding sponges are the least studied. We need more quality research on functions and interaction effects, about which we are still insufficiently informed. With many calcifiers increasingly failing and bioeroding sponges still doing well, at least at intermediate levels of local and global change, these sponges may continue to significantly affect coral reef carbonate budgets. This may transform them from valuable and necessary recyclers of calcium carbonate to problem organisms.

Continue reading ‘Bioeroding sponges and the future of coral reefs’


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Ocean acidification in the IPCC AR5 WG II

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