Elevated CO2 delays the early development of scleractinian coral Acropora gemmifera

The effects of elevated CO2 on the early life stages of coral were investigated by culturing the pelagic larvae and new recruits of Acropora gemmifera at three concentrations of CO2 (corresponding to pH = 8.1, 7.8 and 7.5, respectively). Acidified seawater resulted in fewer A. gemmifera larvae settling, and led to the production of smaller new recruits by slowing the development of the skeleton. The delayed development of new recruits due to elevated CO2 was consistent with the downregulation of calcification related genes. Several genes related to HCO3− and Ca2+ transporters were downregulated by elevated CO2, with solute carriers (SLC) (membrane transport proteins) possibly playing an important role. The downregulation of these membrane transport proteins might suppress the transport of calcium, bicarbonate and organic matter, resulting in the delayed development of A. gemmifera.

Continue reading ‘Elevated CO2 delays the early development of scleractinian coral Acropora gemmifera’

Carbonate chemistry of an in-situ free-ocean CO2 enrichment experiment (antFOCE) in comparison to short term variation in Antarctic coastal waters

Free-ocean CO2 enrichment (FOCE) experiments have been deployed in marine ecosystems to manipulate carbonate system conditions to those predicted in future oceans. We investigated whether the pH/carbonate chemistry of extremely cold polar waters can be manipulated in an ecologically relevant way, to represent conditions under future atmospheric CO2 levels, in an in-situ FOCE experiment in Antarctica. We examined spatial and temporal variation in local ambient carbonate chemistry at hourly intervals at two sites between December and February and compared these with experimental conditions. We successfully maintained a mean pH offset in acidified benthic chambers of −0.38 (±0.07) from ambient for approximately 8 weeks. Local diel and seasonal fluctuations in ambient pH were duplicated in the FOCE system. Large temporal variability in acidified chambers resulted from system stoppages. The mean pH, Ωarag and fCO2 values in the acidified chambers were 7.688 ± 0.079, 0.62 ± 0.13 and 912 ± 150 µatm, respectively. Variation in ambient pH appeared to be mainly driven by salinity and biological production and ranged from 8.019 to 8.192 with significant spatio-temporal variation. This experiment demonstrates the utility of FOCE systems to create conditions expected in future oceans that represent ecologically relevant variation, even under polar conditions.

Continue reading ‘Carbonate chemistry of an in-situ free-ocean CO2 enrichment experiment (antFOCE) in comparison to short term variation in Antarctic coastal waters’

Ecological responses to ocean acidification by developing marine fouling communities

Increasing levels of CO2 in the atmosphere are rapidly affecting ocean chemistry, leading to increased acidification (i.e., decreased pH) and reductions in calcium carbonate saturation state. This phenomenon, known as ocean acidification, poses a serious imminent threat to marine species, especially those that use calcium carbonate. In this dissertation, I use a variety of methods (field-based experiments, surveys, meta-analysis) to understand how marine communities respond to both natural and experimental CO2 enrichment and how responses could be shaped by species interactions or food availability. I found that ocean acidification influenced community assembly, recruitment, and succession to create homogenized, low diversity communities. I found broadly that soft-bodied, weedy taxa (e.g., algae and ascidians) had an advantage in acidified conditions and outcompeted heavily calcified taxa (e.g., mussels, serpulids) that were more vulnerable to the effects of acidification, although calcified bryozoans and barnacles exhibited mixed responses. Next, I examined an important hypothesis of context dependency in ocean acidification research: that negative responses by calcifiers to high CO2 could be reduced by higher energy input. I found little support for this hypothesis for species growth and abundance, and in fact found that, for some species, additional food supply exacerbated or brought out the negative effects of CO2. Further, I found that acidification stress can tip the balance of community composition towards invasion, under resource conditions that enabled the native community to resist invasions. Overall, it is clear that acidification is a strong driving force in marine communities but understanding the underlying energetic and competitive context is essential to predicting climate change responses.

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Ocean acidification affects both the predator and prey to alter interactions between the oyster Crassostrea gigas (Thunberg, 1793) and the whelk Tenguella marginalba (Blainville, 1832)

As the oceans acidify, marine invertebrates will experience physiological and behavioural changes that may alter how predators interact with their prey. This study assessed whether ocean acidification alters the predatory whelk Tenguella marginalba, their prey, the Pacific oyster, Crassostrea gigas, and their interactions. Oysters and whelks were exposed separately to ambient or elevated pCO2 for 6 weeks, after which, a reciprocal cross design was used to expose oysters and whelks together to ambient and elevated pCO2. Both T. marginalba and C. gigas were measured for growth, shell morphology, shell compression strength and metabolic rate. The rate at which whelks consumed oysters was also measured. We found C. gigas had weaker shells and greater SMR at elevated pCO2, but lowered its SMR when held at ambient pCO2 with T. marginalba. T. marginalba had a greater SMR and consumed more C. gigas when both the predator and prey were held at elevated pCO2. We also tested whether C. gigas responses to predator chemical cues were altered by ocean acidification. C. gigas lowered its metabolic rate in response to predator cues at ambient, but not elevated pCO2. We conclude that elevated pCO2 may increase the energy requirements of predators, as they attempt to maintain homoeostasis. Furthermore, elevated pCO2 may also alter the morphology and increase the visibility of prey. Whether the consequence of this will be a sustained increase in consumption by the predator is less certain as molluscs acclimate and the dynamics of other organisms in marine ecosystems are also altered.

Continue reading ‘Ocean acidification affects both the predator and prey to alter interactions between the oyster Crassostrea gigas (Thunberg, 1793) and the whelk Tenguella marginalba (Blainville, 1832)’

Population-specific responses in physiological rates of Emiliania huxleyi to a broad CO2 range

Although coccolithophore physiological responses to CO2-induced changes in seawater carbonate chemistry have been widely studied in the past, there is limited knowledge on the variability of physiological responses between populations. In the present study, we investigated the population-specific responses of growth, particulate organic (POC) and inorganic carbon (PIC) production rates of 17 strains of the coccolithophore Emiliania huxleyi from three regions in the North Atlantic Ocean (Azores, Canary Islands, and Norwegian coast near Bergen) to a CO2 partial pressure (pCO2) range from 120 µatm to 2630 µatm. Physiological rates of each population and individual strain displayed the expected optimum curve responses to the pCO2 gradient. Optimal pCO2 for growth and POC production rates and tolerance to low pH (i.e. high proton concentration) was significantly higher in an E. huxleyi population isolated from a Norwegian fjord than in those isolated near the Azores and Canary Islands. This may be due to the large pCO2 and pH variability in coastal waters off Bergen compared to the rather stable oceanic conditions at the other two sites. Maximum growth and POC production rates of the Azores and Bergen populations were similar and significantly higher than of the Canary Islands population. One of the reasons may be that the chosen incubation temperature (16 °C) is slightly below what strains isolated near the Canary Islands normally experience. Our results indicate adaptation of E. huxleyi to their local environmental conditions. Within each population, different growth, POC and PIC production rates at different pCO2 levels indicated strain-specific phenotypic plasticity. The existence of distinct carbonate chemistry responses between and within populations will likely benefit E. huxleyi to acclimate to rising CO2 levels in the oceans.

Continue reading ‘Population-specific responses in physiological rates of Emiliania huxleyi to a broad CO2 range’

Update to SDG14.3 Voluntary Committment: Enhancing global ocean acidification monitoring and research by GOA-ON

Update from 25 January 2018: GOA-ON contributes to the Sustainable Development Goals and the 2030 Agenda

The 2030 Agenda for Sustainable Development, adopted in September 2015 by the United Nations, contains 17 Sustainable Development Goals (SDGs). Goal 14, life below water, is to conserve and sustainably use the oceans, seas, and marine resources, and consists of 10 targets. Of particular interest to the Global Ocean Acidification Observing Network (GOA-ON) community is target 14.3, minimize and address the impacts of ocean acidification, including through scientific cooperation at all levels.

GOA-ON directly contributes to the achievement of SDG 14.3. At the June 2017 UN Oceans Conference, which focused on SDG 14, GOA-ON made a voluntary commitment to expand the spatial and temporal coverage of ocean acidification observations around the world, and participated in multiple side events as well as the Partnership Dialogue on ocean acidification. In addition, GOA-ON has joined forces with several partner organizations to conduct capacity building workshops around the world, which consist of lectures, practical training, and, in some cases, the provision of sensing equipment to local scientists.


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How oysters, mussels, and corals help marine vegetation buffer ocean acidification


Photo: Kristin Riser/Wikimedia Commons (CC0)

Ocean acidification is already threatening marine life around the world, and conditions are only expected to worsen in the coming years. But for certain shoreline environments, there may be a workaround. Researchers have discovered that marine vegetation such as seaweed and seagrass exert such a strong mitigating effect on local water acidification that they could alleviate some of the impacts on coastal ecosystems.

Continue reading ‘How oysters, mussels, and corals help marine vegetation buffer ocean acidification’

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Ocean acidification in the IPCC AR5 WG II

OUP book