Posts Tagged 'biodiversity'

Boosted fish abundance associated with Posidonia oceanica meadows in temperate shallow CO2 vents


  • Ocean acidification (OA) may induce shifts in the structure and function of coastal marine ecosystems
  • CO2 vents were used to assess the effects of OA on fish assemblages associated with Posidonia oceanica
  • Posidonia structure and associated fish assemblages were compared at vents and off-vents using underwater visual census
  • Posidonia density increases and fish show boosted abundance but not reduced diversity at vents
  • Mediterranean Posidonia fish assemblages may cope with OA under near-future acidification level


Ocean acidification (OA) may induce major shifts in the structure and function of coastal marine ecosystems. Studies in volcanic CO2 vents, where seawater is naturally acidified, have reported an overall simplification of fish assemblages structure, while some primary producers are likely to increase their biomass under elevated concentration of CO2. Here we used temperate shallow CO2 vents located around the coast of Ischia island (Italy) to assess the effects of OA on necto-benthic fish assemblages associated with the foundation seagrass species Posidonia oceanica in the Mediterranean Sea. We compared P. oceanica meadow structure, its epiphytic community and the associated fish assemblage structure and diversity at vents with low pH sites and reference sites with ambient pH using underwater visual census strip transects, in two seasons (fall 2018 and summer 2019). Data were analysed using both univariate and multivariate statistical techniques. Results showed greater P. oceanica habitat complexity (i.e. shoot density) and lower abundance of epiphytic calcareous species (e.g. coralline algae) at the vents than reference sites. Total abundance of adult and juvenile fish was higher at vents than reference sites, while no differences were found for species richness and composition. Overall, the herbivore Sarpa salpa stands out among the species contributing the most to dissimilarity between vents and reference sites, showing higher abundances under OA conditions. This pattern could be explained by the combined effect of a positive response to the higher structural meadows complexity and the greater seagrasses palatability / nutritional value occurring at the vents, which may help herbivores to withstand the higher energetic cost to live under high pCO2 / low pH conditions. Our results indicate that necto-benthic fish assemblages associated with the Mediterranean P. oceanica ecosystem may cope with OA under the CO2 emission scenarios forecasted for the end of this century.

Continue reading ‘Boosted fish abundance associated with Posidonia oceanica meadows in temperate shallow CO2 vents’

Community composition has greater impact on the functioning of marine phytoplankton communities than ocean acidification

Ecosystem functioning is simultaneously affected by changes in community composition and environmental change such as increasing atmospheric carbon dioxide (CO2) and subsequent ocean acidification. However, it largely remains uncertain how the effects of these factors compare to each other. Addressing this question, we experimentally tested the hypothesis that initial community composition and elevated CO2 are equally important to the regulation of phytoplankton biomass. We full-factorially exposed three compositionally different marine phytoplankton communities to two different CO2 levels and examined the effects and relative importance (ω2) of the two factors and their interaction on phytoplankton biomass at bloom peak. The results showed that initial community composition had a significantly greater impact than elevated CO2 on phytoplankton biomass, which varied largely among communities. We suggest that the different initial ratios between cyanobacteria, diatoms, and dinoflagellates might be the key for the varying competitive and thus functional outcome among communities. Furthermore, the results showed that depending on initial community composition elevated CO2 selected for larger sized diatoms, which led to increased total phytoplankton biomass. Our study highlights the relevance of initial community composition, which strongly drives the functional outcome, when assessing impacts of climate change on ecosystem functioning. In particular, the increase in phytoplankton biomass driven by the gain of larger sized diatoms in response to elevated CO2 potentially has strong implications for nutrient cycling and carbon export in future oceans.

Continue reading ‘Community composition has greater impact on the functioning of marine phytoplankton communities than ocean acidification’

Travelling through time: the past, present and future biogeographic range of the invasive foraminifera Amphistegina spp. in the Mediterranean Sea

The opening of the Suez Canal in 1869 has created a pathway of migration for biota from the Red Sea into the Mediterranean Sea. This has a substantial impact on the marine ecology, endangering many local and endemic taxa. Larger foraminifera of the genus Amphistegina are among the most successful invaders, as evidenced by their abundance, ubiquity and wide extension in the Aegean and Ionian Sea. Because global climate change will amplify the entry and range expansion of tropical species in the Mediterranean, the interest in predicting species ranges and forecasting potentially negative impacts on ecosystems has grown substantially. We modeled the potential distribution of Amphistegina spp. and projected the result on future climate scenarios for 2050 and 2100, to predict range extensions of the taxon in future and compare these to range expansions under warm climate as documented in the fossil record. Results indicate that further warming is likely to cause a continued range extension, and predicts dispersal along the central Mediterranean coasts. The average range expansion rates were computed between 11.76 and 13.82 km per year, and are projected to lead to a total range expansion of 525 km (4.71° latitude) and 1035 km (11.87° longitude) in the year 2100. The results corroborate findings from the fossil record showing that some larger symbiont-bearing foraminifera cope well with rising water temperatures and are beneficiaries of warmer climate. It is anticipated that the ongoing warming trend will convey the northwestward migration of Mediterranean amphisteginids, implicating substantial consequences for marine ecosystems.

Continue reading ‘Travelling through time: the past, present and future biogeographic range of the invasive foraminifera Amphistegina spp. in the Mediterranean Sea’

Surviving rapid climate change in the deep sea during the Paleogene hyperthermals

Predicting the impact of ongoing anthropogenic CO2 emissions on calcifying marine organisms is complex, owing to the synergy between direct changes (acidification) and indirect changes through climate change (e.g., warming, changes in ocean circulation, and deoxygenation). Laboratory experiments, particularly on longer-lived organisms, tend to be too short to reveal the potential of organisms to acclimatize, adapt, or evolve and usually do not incorporate multiple stressors. We studied two examples of rapid carbon release in the geological record, Eocene Thermal Maximum 2 (∼53.2 Ma) and the Paleocene Eocene Thermal Maximum (PETM, ∼55.5 Ma), the best analogs over the last 65 Ma for future ocean acidification related to high atmospheric CO2 levels. We use benthic foraminifers, which suffered severe extinction during the PETM, as a model group. Using synchrotron radiation X-ray tomographic microscopy, we reconstruct the calcification response of survivor species and find, contrary to expectations, that calcification significantly increased during the PETM. In contrast, there was no significant response to the smaller Eocene Thermal Maximum 2, which was associated with a minor change in diversity only. These observations suggest that there is a response threshold for extinction and calcification response, while highlighting the utility of the geological record in helping constrain the sensitivity of biotic response to environmental change.

Continue reading ‘Surviving rapid climate change in the deep sea during the Paleogene hyperthermals’

Intertidal rocky shore seaweed communities subject to the influence of shallow water hydrothermal activity in São Miguel (Azores, Portugal)

The volcanic origin of the Azores archipelago (Portugal) gives rise to active deep sea and shallow water hydrothermal activity that affects benthic communities. Intertidal seaweed surveys were conducted at two shores affected by intense shallow water hydrothermal vents. Water temperature, acidity and salinity were monitored. Seaweed communities were found to be species poor and have a disproportionally larger number of filamentous early successional species on shores that are subject to the effect of hot and acidic freshwater of volcanic origin. There is an ecological resemblance between hydrothermally affected seaweed communities in the Azores and those affected by acid mine drainage in the UK, thus indicating that hydrothermalism can be a useful scenario for pollution studies under conditions of ocean warming and acidification.

Continue reading ‘Intertidal rocky shore seaweed communities subject to the influence of shallow water hydrothermal activity in São Miguel (Azores, Portugal)’

Structural and functional vulnerability to elevated pCO2 in marine benthic communities

The effect of elevated pCO2/low pH on marine invertebrate benthic biodiversity, community structure and selected functional responses which underpin ecosystem services (such as community production and calcification) was tested in a medium-term (30 days) mesocosm experiment in June 2010. Standardised intertidal macrobenthic communities, collected (50.3567°N, 4.1277°W) using artificial substrate units (ASUs), were exposed to one of seven pH treatments (8.05, 7.8. 7.6, 7.4, 7.2, 6.8 and 6.0). Community net calcification/dissolution rates, as well as changes in biomass, community structure and diversity, were measured at the end of the experimental period. Communities showed significant changes in structure and reduced diversity in response to reduced pH: shifting from a community dominated by calcareous organisms to one dominated by non-calcareous organisms around either pH 7.2 (number of individuals and species) or pH 7.8 (biomass). These results were supported by a reduced total weight of CaCO3 structures in all major taxa at lowered pH and a switch from net calcification to net dissolution around pH 7.4 (Ωcalc = 0.78, Ωara = 0.5). Overall community soft tissue biomass did not change with pH and high mortality was observed only at pH 6.0, although molluscs and arthropods showed significant decreases in soft tissue. This study supports and refines previous findings on how elevated pCO2 can induce changes in marine biodiversity, underlined by differential vulnerability of different phyla. In addition, it shows significant elevated pCO2-/low pH-dependent changes in fundamental community functional responses underpinning changes in ecosystem services.

Continue reading ‘Structural and functional vulnerability to elevated pCO2 in marine benthic communities’

Marine biodiversity: its history, present status and future threats

Whilst the measured rise in atmospheric CO2 levels and global temperatures are dramatic, these increases would have been even greater were it not for the fact that almost half of all the anthropogenic CO2 emitted over the last 250 years has been taken up by the world’s oceans (Sabine et al. 2004).

Continue reading ‘Marine biodiversity: its history, present status and future threats’

Biodiversity stability of shallow marine benthos in Strait of Georgia, British Columbia, Canada through climate regimes, overfishing and ocean acidification

The highest human population density in British Columbia, Canada is situated around the shores of the Strait of Georgia, where current government policy is focusing early efforts toward achieving ecosystem-based management of marine resources. Climate regime shifts are acknowledged to have affected commercial fishery production in southern British Columbia (McFarlane et al., 2000), and overfishing is well documented in the Strait of Georgia region for a variety of important species, to the extent that Rockfish Conservation Areas have been created (Marliave & Challenger, 2009). As CO2 levels rise in the atmosphere, the oceans become progressively more acidic. While ocean acidification is predicted to be a great threat to marine ecosystems, little is known about its ecosystem impacts. Few taxpayer-funded studies have committed to long-term monitoring of full ecosystem biodiversity. This document presents results of over forty years of private taxonomic monitoring of shallow seafloors in the region centering on the Strait of Georgia.
Also presented are records of ambient ocean acidity levels (pH), documented continuously by the Vancouver Aquarium through the same time period. Biodiversity data are summarized in ways that enable visualization of possible relationships to climate regimes and ocean acidification. This work does not attempt statistical analyses, in the hope that the data trends can be incorporated into future models.

Continue reading ‘Biodiversity stability of shallow marine benthos in Strait of Georgia, British Columbia, Canada through climate regimes, overfishing and ocean acidification’

The impact of low pH, low aragonite saturation state on calcifying corals: an in-situ study of ocean acidification from the “ojos” of Puerto Morelos, Mexico

Recent increases in atmospheric carbon dioxide have resulted in rising aqueous CO2 concentrations that lower the pH of the oceans (Caldeira and Wickett 2003, 2005, Doney et al., 2009). It is estimated that over the next 100 years, the pH of the surface oceans will decrease by ~0.4 pH units (Orr et al., 2005), which is expected to hinder the calcifying capabilities of numerous marine organisms. Previous field work (Hall-Spencer et al., 2008) indicates that ocean acidification will negatively impact calcifying species; however, to date, very little is known about the long-term impacts of ocean acidification from the in-situ study of coral reef ecosystems. The Yucatán Peninsula of Quintana Roo, Mexico, represents an ecosystem where naturally low pH groundwater (7.14-8.07) has been discharging offshore at highly localized points (called ojos) for millennia. We present preliminary chemical and biological data on a selection of ojos from lagoon sites in Puerto Morelos, Mexico. Our findings indicate a decrease in species richness and size with proximity to the low pH waters. We address the potential long-term implications of low pH, low aragonite saturation state on coral reef ecosystems.

Continue reading ‘The impact of low pH, low aragonite saturation state on calcifying corals: an in-situ study of ocean acidification from the “ojos” of Puerto Morelos, Mexico’

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Ocean acidification in the IPCC AR5 WG II

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