Archive for February, 2013

Ocean acidification (video)

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Impacts of ocean acidification on marine organisms: quantifying sensitivities and interaction with warming

Ocean acidification represents a threat to marine species worldwide, and forecasting the ecological impacts of acidification is a high priority for science, management, and policy. As research on the topic expands at an exponential rate, a comprehensive understanding of the variability in organisms’ responses and corresponding levels of certainty is necessary to forecast the ecological effects. Here, we perform the most comprehensive meta-analysis to date by synthesizing the results of 228 studies examining biological responses to ocean acidification. The results reveal decreased survival, calcification, growth, development and abundance in response to acidification when the broad range of marine organisms is pooled together. However, the magnitude of these responses varies among taxonomic groups, suggesting there is some predictable trait-based variation in sensitivity despite the investigation of approximately 100 new species in recent research. The results also reveal an enhanced sensitivity of mollusc larvae, but suggest that an enhanced sensitivity of early life history stages is not universal across all taxonomic groups. In addition, the variability in species’ responses is enhanced when they are exposed to acidification in multi-species assemblages, suggesting it is important to consider indirect effects and exercise caution when forecasting abundance patterns from single species laboratory experiments. Furthermore, the results suggest that other factors, such as nutritional status or source population, could cause substantial variation in organisms’ responses. Last, the results highlight a trend towards enhanced sensitivity to acidification when taxa are concurrently exposed to elevated seawater temperature.

Continue reading ‘Impacts of ocean acidification on marine organisms: quantifying sensitivities and interaction with warming’

Acid test: threat to oceans may also harm Great Lakes

The increased carbon dioxide changing the water chemistry and ecology of oceans may also be affecting freshwater and the organisms that live in it.

It’s called ocean acidification. But some researchers suspect it will impact the Great Lakes.

“Based on our preliminary modeling and understanding of carbon cycles, we think similar acidification trends will take place in the Great Lakes to the degree that researchers are expecting in the oceans,” said Galen McKinley, a professor of atmospheric and oceanic sciences at the University of Wisconsin.

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Ocean acidification seminar to open Maine Fishermen’s Forum this Thursday, February 28

38th annual forum runs Thursday through Saturday, includes seminars, trade show, scholarship auction –

The 38th annual Maine Fishermen’s Forum will open Thursday, February 28, and continue through Saturday, March 2, at the Samoset Resort in Rockport. The forum is open to the public and attendance is free at the seminars and the trade show.

Thursday opens with a half-day seminar, 8 a.m. to 12:15 p.m. in the Rockport Room at the Samoset, on ocean acidification in Maine, presented by The Island Institute, the National Fisheries Conservation Center, and the Sustainable Fisheries Partnership. Researchers, commercial fishermen, shellfish harvesters, and growers will share stories, ask questions, and discuss next steps in addressing what can be done to protect and preserve the ocean that provides jobs and food.

Continue reading ‘Ocean acidification seminar to open Maine Fishermen’s Forum this Thursday, February 28′

Effects of ocean acidification, temperature and nutrient regimes on the appendicularian Oikopleura dioica: a mesocosm study

Increasing pCO2 is hypothesized to induce shifts in plankton communities toward smaller cells, reduced carbon export rates and increased roles of gelatinous zooplankton. Appendicularians, among the most numerous pan-global “gelatinous” zooplankton, continuously produce filter-feeding houses, shortcutting marine food webs by ingesting submicron particles, and their discarded houses contribute significantly to carbon fluxes. We present a first mesocosm-scale study on the effects of temperature, pCO2 and bloom structures on the appendicularian, Oikopleura dioica. There were effects of temperature and nutrients on phytoplankton communities. No shifts in functional phytoplankton groups, nor changes in particle sizes/morphotypes, known to impact appendicularian feeding, were observed under manipulated pCO2 conditions. However, appendicularian abundance was positively correlated with increased pCO2, temperature and nutrient levels, consistent with hypotheses concerning gelatinous zooplankton in future oceans. This suggests appendicularians will play more important roles in marine pelagic communities and vertical carbon transport under projected ocean acidification and elevated temperature scenarios.

Continue reading ‘Effects of ocean acidification, temperature and nutrient regimes on the appendicularian Oikopleura dioica: a mesocosm study’

Elevated CO2 alters larval proteome and its phosphorylation status in the commercial oyster, Crassostrea hongkongensis

Ocean acidification (OA) is beginning to have noticeable negative impact on calcification rate, shell structure and physiological energy budgeting of several marine organisms; these alter the growth of many economically important shellfish including oysters. Early life stages of oysters may be particularly vulnerable to OA-driven low pH conditions because their shell is made up of the highly soluble form of calcium carbonate (CaCO3) mineral, aragonite. Our long-term CO2 perturbation experiment showed that larval shell growth rate of the oyster species Crassostrea hongkongensis was significantly reduced at pH < 7.9 compared to the control (8.2). To gain new insights into the underlying mechanisms of low-pH-induced delays in larval growth, we have examined the effect of pH on the protein expression pattern, including protein phosphorylation status at the pediveliger larval stage. Using two-dimensional electrophoresis and mass spectrometry, we demonstrated that the larval proteome was significantly altered by the two low pH treatments (7.9 and 7.6) compared to the control pH (8.2). Generally, the number of expressed proteins and their phosphorylation level decreased with low pH. Proteins involved in larval energy metabolism and calcification appeared to be down-regulated in response to low pH, whereas cell motility and production of cytoskeletal proteins were increased. This study on larval growth coupled with proteome change is the first step toward the search for novel Protein Expression Signatures indicative of low pH, which may help in understanding the mechanisms involved in low pH tolerance.

Continue reading ‘Elevated CO2 alters larval proteome and its phosphorylation status in the commercial oyster, Crassostrea hongkongensis’

The physiological and molecular responses of larvae from the reef-building coral Pocillopora damicornis exposed to near-future increases in temperature and pCO2

Given the threats of greenhouse gas emissions and a changing climate to marine ecosystems, there is an urgent need to better understand the response of not only adult corals, which are particularly sensitive to environmental changes, but also their larvae, whose mechanisms of acclimation to both temperature increases and ocean acidification are not well understood. Brooded larvae from the reef coral Pocillopora damicornis collected from Nanwan Bay, Southern Taiwan, were exposed to ambient or elevated temperature (25 or 29 °C) and pCO2 (415 or 635 μatm) in a factorial experiment for 9 days, and a variety of physiological and molecular parameters were measured. Respiration and rubisco protein expression decreased in larvae exposed to elevated temperature, while those incubated at high pCO2 were larger in size. Collectively, these findings highlight the complex metabolic and molecular responses of this life history stage and the need to integrate our understanding across multiple levels of biological organization. Our results also suggest that for this pocilloporid larval life stage, the impacts of elevated temperature are likely a greater threat under near-future predictions for climate change than ocean acidification.

Continue reading ‘The physiological and molecular responses of larvae from the reef-building coral Pocillopora damicornis exposed to near-future increases in temperature and pCO2’

The effects of intermittent exposure to low pH and oxygen conditions on survival and growth of juvenile red abalone

Exposure of nearshore animals to hypoxic, low pH waters upwelled from below the continental shelf and advected near the coast may be stressful to marine organisms and lead to impaired physiological performance. We mimicked upwelling conditions in the laboratory and tested the effect of fluctuating exposure to water with low pH and/or low oxygen levels on the mortality and growth of juvenile red abalone (Haliotis rufescens, shell length 5–10 mm). Mortality rates of juvenile abalone exposed to low pH (7.5, total scale) and low O2 (40% saturation, 5 mg L−1) conditions for periods of 3 to 6 h every 3–5 days over 2 weeks did not differ from those exposed to control conditions (O2: 100% saturation, 12 mg L−1; pH 8.0). However, when exposure was extended to 24 h repeated twice over a 15 day period, juveniles experienced higher mortality in the low oxygen treatments compared to control conditions, regardless of pH levels (pH 7.5 vs. 8.0). Growth rates were reduced significantly when juveniles were exposed to low pH or low oxygen treatments and the growth was lowest when low pH exposure was combined with low O2. Furthermore, individual variation of growth rate increased when they were exposed to low pH and low O2 conditions. These results indicate that prolonged exposure to low oxygen levels is detrimental for the survival of red abalone, whereas both pH and oxygen is a crucial factor for their growth. However, given the higher individual variation in growth rate, they may have an ability to adapt to extended exposure to upwelling conditions.

Continue reading ‘The effects of intermittent exposure to low pH and oxygen conditions on survival and growth of juvenile red abalone’

Response of pteropod and related faunas to climate change and ocean acidification

Recent concern over the effects of ocean acidification upon calcifying organisms in the modern ocean has highlighted the aragonitic shelled thecosomatous pteropods as being at a high risk. Laboratory studies have shown that increased pCO2, leading to decreased pH and low carbonate concentrations, has a negative impact on the ability of pteropods to calcify and maintain their shells. This study presents the micropalaeontological analysis of marine cores from the Caribbean Sea, Mediterranean Sea and Indian Ocean. Pteropods, heteropods and planktic foraminifera were picked from samples to provide palaeoenvironmental data for each core. Determination of pteropod calcification was made using the Limacina Dissolution Index (LDX) and the average shell size of Limacina inflata specimens. Pteropod calcification indices were compared to global ice volume and Vostok atmospheric CO2 concentrations to determine any associations between climate and calcification. Results show that changes in surface ocean carbonate concentrations throughout the Late Pleistocene did affect the calcification of thecosomatous pteropods. These effects can be detected in shells from marine sediments that are located well above the aragonite lysocline and have not undergone post-depositional dissolution. The results of this study confirm the findings of laboratory studies, showing a decrease in calcification during interglacial periods, when surface ocean carbonate concentrations were lower. During glacial periods, calcification was enhanced due to the increased availability of carbonate. This trend was found in all sediments studied, indicating that the response of pteropods to past climate change is of global significance. These results demonstrate that pteropods have been negatively affected by oceanic pH levels relatively higher and changing at a lesser rate than those predicted for the 21st Century. Results also establish the use of pteropods and heteropods in reconstructing surface ocean conditions. The LDX is a fast and appropriate way of determining variations in surface water carbonate saturation. Abundances of key species were also found to constrain palaeotemperatures better than planktic foraminifera, a use which could be further developed.

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Enhanced gas fluxes in small sea ice leads and cracks – effects on CO2 exchange and ocean acidification

Earth system models generally partition grid cells into an ice covered and an open water area and view the ice covered area as a barrier to gas fluxes. However, observations suggest that exchange in cracks and small leads can be much higher in localized areas than expected under similar conditions in open water. While these models project a significant retreat in sea ice cover, affecting air-sea CO2 exchange and consequently ocean acidification, the simple grid cell partitioning might underestimate the actual CO2 exchange. A sensitivity study with the Canadian Earth System Model (CanESM2) shows that enhanced CO2 exchange in sea ice areas in the Arctic Ocean increases the uptake in fall and winter, allowing more continuous equilibration and hence reduced uptake in summer. The reduction in summer also hints at a limited CO2-uptake capacity of Arctic surface waters. Retreating sea ice in the future leads to a similar shift in the seasonal cycle. The annual mean carbon uptake of the Arctic Ocean north of 68°N changes only slightly with the enhanced flux parameterisation (<3 %). For the central Arctic (north of 80°N) the change is up to 21% and accelerates ocean acidification, e.g. locally, surface waters could reach aragonite undersaturation 1–2 decades earlier. The differences between standard and enhanced exchange test runs become less pronounced in the future due to the reduced ice cover and extended open water season. For the Antarctic sea ice zone where the CO2 flux is out of the ocean, the enhanced exchange increases outgassing, slightly slowing down acidification.

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Ocean acidification in the IPCC AR5 WG II

OUP book