Where are the “hotspots” for ocean acidification?


By now, coastal communities are asking: “Who’ll be hit next by ocean acidification? And what can people do?” Until now, we haven’t known where exactly in the United States ocean acidification is most likely to affect marine ecosystems, and where the effects on people could be greatest. (Fortunately, several forward-thinking states are already studying the issue and recommending next steps!)

Three years ago, I teamed up with an economist, a human geographer, and another ocean acidification scientist to lead a study that would identify ocean acidification “hotspots” around the United States – places where ocean changes will be large and coastal communities depend heavily on shellfish harvests, but where people don’t have many resources to guard against losses of these harvests. We gathered a group of 20 science and policy experts to study the issue at the National Science Foundation-funded National Socio-Environmental Synthesis Center (SESYNC). Since then, we’ve synthesized information about the oceanography, shellfish harvests, and coastal communities across the United States in a formal risk assessment. We’ve just published our results in Nature Climate Change this week.

Continue reading ‘Where are the “hotspots” for ocean acidification?’

Spatial and temporal pCO2 marine monitoring near Panarea Island (Italy) using multiple low-cost GasPro sensors

The present paper describes the GasPro probe, a small, low-cost unit for in situ, continuous pCO2 monitoring. Laboratory tests defining its performance characteristics are reported, as are the results from a 60 h water-column deployment of 20 such units near a natural CO2 seep site off the coast of Panarea Island (Italy). The spatial-temporal evolution of dissolved CO2 movement is presented and possible origins and controlling mechanisms discussed. Results highlight the potential for this technology to be used for better understanding various dynamic physical and biochemical processes in marine environments, and for marine environmental monitoring of off-shore industrial sites. These experiments have allowed us to assess the advantages and disadvantages of the present GasPro prototype and to define areas for ongoing improvement.

Continue reading ‘Spatial and temporal pCO2 marine monitoring near Panarea Island (Italy) using multiple low-cost GasPro sensors’

A natural strategy against climate change

This paper presents a short description of the quantitatively most important applications of enhanced weathering of olivine to counter climate change and ocean acidification. CO2 is captured by the weathering of basic silicates, in particular olivine or its hydrated equivalent serpentine. During the whole history of the Earth, weathering has played the major role in the capture and
storage of the CO2 that was emitted by volcanoes. If all that CO2 had remained in the atmosphere there would be no life on our planet. It is logical, therefore, to stimulate this process to counteract climate change, caused by the rapidly rising CO2 levels in the atmosphere. Enhanced weathering covers applications on land, along the coast and in shallow marine environments. In addition some topics are mentioned that have no geographic restriction. An attempt is made to quantitatively estimate the carbon capture potential of each topic.

Continue reading ‘A natural strategy against climate change’

New isotopic methods to better understand the effects of ocean acidification on net ecosystem calcification and coral calcification rates in Bermuda

The health and future of coral and coral reef ecosystems remains threatened by global climate change (GCC) and ocean acidification (OA). There is a need to better understand the current health of coral reef ecosystems, particularly those in threshold environments which will likely be affected first by pressures from GCC and OA. This need can be addressed by answering two critical questions: 1) what are the current net ecosystem calcification (NEC) rates in threshold environments? And 2) what physical, biological or chemical parameter is/are driving these calcification rates? Bermuda, located at the northern threshold to support tropical coral reefs, provides an ideal study site to address these questions. To address the first question requires new methods to estimate reef water residence times, a parameter required for estimating NEC rates, but one that has traditionally been difficult to quantify with the necessary accuracy and precision. Two such methods are introduced here, one based on a radio chemical tracer (beryllium-7, 7Be) and one based on a stable chemical tracer (δ18O). Both 7Be and δ18O samples were measured from water samples collected on the Bermuda coral reef platform and yielded spatially and temporally integrated model residence times ranging between 1 and 10 days. To address the second question coral calcification rates were assessed simultaneously with physical (temperature, light) and chemical (seawater aragonite saturation states, Ωarag) properties at both seasonal and hourly timescales to assess how calcification is affected by these physical and chemical driving factors. Seasonal differences in Ωarag only explained a 2.4% change in coral growth, while seasonal differences in light and temperature explained 20% and 26% of the observed 81 mmolCaCO3 m-2 d-1 seasonal change in calcification rates of Porites astreoides and Diploria strigosa. This work contributes to the understanding impacts of GCC and OA on coral reef ecosystems by quantifying current NEC rates across the Bermuda coral reef platform, against which future rates can be assessed. This work also demonstrates that there are multiple driving factors affecting coral calcification rates in situ, though it does not suggest that OA may place a less influential role in governing future changes in coral growth rates as the expected change in Ωarag for 2100 far exceeds the observed seasonal difference in this study.

Continue reading ‘New isotopic methods to better understand the effects of ocean acidification on net ecosystem calcification and coral calcification rates in Bermuda’

Effects of CO2 and seawater acidification on the early stages of Saccharina japonica development

In this paper, we demonstrated that ocean acidification (OA) had significant negative effects on the microscopic development of Saccharina japonica in a short-term exposure experiment under a range of light conditions. Under elevated CO2, the alga showed a significant reduction in meiospore germination, fecundity, and reproductive success. Larger female and male gametophytes were noted to occur under high CO2 conditions and high light magnified these positive effects. Under conditions of low light combined with high PCO2, the differentiation of gametophytes was delayed until the end of the experiment. By contrast, gametophytes were able to survive after having been subjected to a long-term acclimation period, of 105 days. Although the elevated PCO2 resulted in a significant increase in sporophyte length, the biomass abundance (expressed as individual density attached to the seed fiber) was reduced significantly. Further stress resistance experiments showed that, although the acidified samples had lower resistance to high light and high temperature conditions, they displayed higher acclimation to CO2-saturated seawater conditions compared with the control groups. These combined results indicate that OA has a severe negative effect on S. japonica, which may result in future shifts in species dominance and community structure.

Continue reading ‘Effects of CO2 and seawater acidification on the early stages of Saccharina japonica development’

CO2-driven decrease in pH disrupts olfactory behaviour and increases individual variation in deep-sea hermit crabs

Deep-sea species are generally thought to be less tolerant of environmental variation than shallow-living species due to the relatively stable conditions in deep waters for most parameters (e.g. temperature, salinity, oxygen, and pH). To explore the potential for deep-sea hermit crabs (Pagurus tanneri) to acclimate to future ocean acidification, we compared their olfactory and metabolic performance under ambient (pH ∼7.6) and expected future (pH ∼7.1) conditions. After exposure to reduced pH waters, metabolic rates of hermit crabs increased transiently and olfactory behaviour was impaired, including antennular flicking and prey detection. Crabs exposed to low pH treatments exhibited higher individual variation for both the speed of antennular flicking and speed of prey detection, than observed in the control pH treatment, suggesting that phenotypic diversity could promote adaptation to future ocean acidification.

Continue reading ‘CO2-driven decrease in pH disrupts olfactory behaviour and increases individual variation in deep-sea hermit crabs’

Coral records of reef-water pH across the central Great Barrier Reef, Australia: assessing the influence of river runoff on inshore reefs (update)

The boron isotopic (δ11Bcarb) compositions of long-lived Porites coral are used to reconstruct reef-water pH across the central Great Barrier Reef (GBR) and assess the impact of river runoff on inshore reefs. For the period from 1940 to 2009, corals from both inner- and mid-shelf sites exhibit the same overall decrease in δ11Bcarb of 0.086 ± 0.033‰ per decade, equivalent to a decline in seawater pH (pHsw) of ~0.017 ± 0.007 pH units per decade. This decline is consistent with the long-term effects of ocean acidification based on estimates of CO2 uptake by surface waters due to rising atmospheric levels. We also find that, compared to the mid-shelf corals, the δ11Bcarb compositions of inner-shelf corals subject to river discharge events have higher and more variable values, and hence higher inferred pHsw values. These higher δ11Bcarb values of inner-shelf corals are particularly evident during wet years, despite river waters having lower pH. The main effect of river discharge on reef-water carbonate chemistry thus appears to be from reduced aragonite saturation state and higher nutrients driving increased phytoplankton productivity, resulting in the drawdown of pCO2 and increase in pHsw. Increased primary production therefore has the potential to counter the more transient effects of low-pH river water (pHrw) discharged into near-shore environments. Importantly, however, inshore reefs also show a consistent pattern of sharply declining coral growth that coincides with periods of high river discharge. This occurs despite these reefs having higher pHsw, demonstrating the overriding importance of local reef-water quality and reduced aragonite saturation state on coral reef health.

Continue reading ‘Coral records of reef-water pH across the central Great Barrier Reef, Australia: assessing the influence of river runoff on inshore reefs (update)’

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