Archive for June, 2015



Quantifying anthropogenic carbon inventory changes in the Pacific sector of the Southern Ocean

The Southern Ocean plays a major role in mediating the uptake, transport, and long-term storage of anthropogenic carbon dioxide (CO2) into the deep ocean. Examining the magnitude and spatial distribution of this oceanic carbon uptake is critical to understanding how the earth’s carbon system will react to continued increases in this greenhouse gas. Here, we use the extended multiple linear regression technique to quantify the total and anthropogenic change in dissolved inorganic carbon (DIC) along the S04P and P16S CLIVAR/U.S. Global Ocean Carbon and Repeat Hydrography Program lines south of 67°S in the Pacific sector of the Southern Ocean between 1992 and 2011 using discrete bottle measurements from repeat occupations. Along the S04P section, which is located in the seasonal sea ice zone south of the Antarctic Circumpolar Current in the Pacific, the anthropogenic component of the DIC increase from 1992 to 2011 is mostly found in the Antarctic Surface Water (AASW, upper 100 m), while the increase in DIC below the mixed layer in the Circumpolar Deep Water can be primarily attributed to either a slowdown in circulation or decreased ventilation of deeper, high CO2 waters. In the AASW we calculate an anthropogenic increase in DIC of 12 − 18 μmol kg− 1 and an average storage rate of anthropogenic CO2 of 0.10 ± 0.02 mol m− 2 yr− 1 for this region compared to a global average of 0.5 ± 0.2 mol m− 2 yr− 1. In surface waters this anthropogenic CO2 uptake results in an average pH decrease of 0.0022 ± 0.0004 pH units yr− 1, a 0.47 ± 0.10 % yr− 1 decrease in the saturation state of aragonite (ΩAragonite) and a 2.0 ± 0.7 m yr− 1 shoaling of the aragonite saturation horizons (calculated for the ΩAragonite = 1.3 contour).

Continue reading ‘Quantifying anthropogenic carbon inventory changes in the Pacific sector of the Southern Ocean’

Growth responses of a green alga to multiple environmental drivers

One feature of global change is that biota must respond not to single, but to multiple environmental drivers. By growing a model photosynthetic microbe in environments containing between one and eight different drivers, including changes in CO2, temperature, and pH, in different combinations, we show that the number as well as the identities of drivers explain shifts in population growth rates. This is because the biotic response to multiple environmental drivers depends on the response to the single dominant driver, and the chance of a driver of large effect being present increases with the number of drivers. Interactions between drivers slightly counteract the expected drop in growth. Our results demonstrate that population growth declines in a predictable way with the number of environmental drivers, and provide an empirically supported model for scaling up from studies on organismal responses to single drivers to predict responses to large numbers of environmental drivers.

Continue reading ‘Growth responses of a green alga to multiple environmental drivers’

Is ocean acidification killing off baby oysters?

SHELTON, Washington – Tucked into a hillside of pine, just above the Puget Sound, is perhaps the world’s most prolific nursery.

On any given day, hundreds of millions of sea creatures begin life under the watchful eye of marine biologist Benoit Eudeline. He raises oysters for the Taylor Shellfish Company, the largest producer of shellfish in the U.S., processing some 60 million oysters each year.

The oysters begin life in tanks filled with sea water, going from egg to a fully swimming larvae within 24 hours – the larvae so small they can only be seen with a microscope.

But now, these newly born oysters are under threat from a phenomenon known as ocean acidification.

Although it doesn’t get as much attention as melting ice caps or rising sea levels, ocean acidification is one of the most serious effects of greenhouse gas emissions. Nearly a third of the world’s carbon emissions, or about 22 million tons of CO2, is absorbed by the ocean every day. Scientists say this pollution has fundamentally changed ocean chemistry.

Continue reading ‘Is ocean acidification killing off baby oysters?’

Biological oceanography: The CO2 switch in diatoms

Diatoms are important primary producers in the ocean, however their response to rising CO2 is uncertain. Now research shows how diatoms regulate their metabolism in response to changing CO2.

Continue reading ‘Biological oceanography: The CO2 switch in diatoms’

Disciplinary reporting affects the interpretation of climate change impacts in global oceans

Climate change is affecting marine ecosystems, but different investigative approaches in physical, chemical, and biological disciplines may influence interpretations of climate-driven changes in the ocean. Here, we review the ocean change literature from 2007 to 2012 based on 461 of the most highly cited studies in physical and chemical oceanography and three biological subdisciplines. Using highly cited studies, we focus on research that has shaped recent discourse on climate-driven ocean change. Our review identified significant differences in spatial and temporal scales of investigation among disciplines. Physical/chemical studies had a median duration of 29 years (n = 150) and covered the greatest study areas (median 1.41 × 107 km2, n = 148). Few biological studies were conducted over similar spatial and temporal scales (median 8 years, n = 215; median 302 km2, n = 196), suggesting a more limited ability to separate climate-related responses from natural variability. We linked physical/chemical and biological disciplines by tracking studies examining biological responses to changing ocean conditions. Of the 545 biological responses recorded, a single physical or chemical stressor was usually implicated as the cause (59%), with temperature as the most common primary stressor (44%). The most frequently studied biological responses were changes in physiology (31%) and population abundance (30%). Differences in disciplinary studies, as identified in this review, can ultimately influence how researchers interpret climate-related impacts in marine systems. We identified research gaps and the need for more discourse in (1) the Indian and other Southern Hemisphere ocean basins; (2) research themes such as archaea, bacteria, viruses, mangroves, turtles, and ocean acidification; (3) physical and chemical stressors such as dissolved oxygen, salinity, and upwelling; and (4) adaptive responses of marine organisms to climate-driven ocean change. Our findings reveal that highly cited biological studies are rarely conducted on scales that match those of physical and chemical studies. Rather, we suggest a need for measuring responses at biologically relevant scales.

Continue reading ‘Disciplinary reporting affects the interpretation of climate change impacts in global oceans’

It’s not just climate — Pope Francis is also warning about the health of our oceans

With the release of his encyclical “Laudato Si” on Thursday, Pope Francis made headlines for recognizing the threat of human-caused climate change.

But the encyclical also called attention to the world’s oceans, affirming just how vital they are to “our common home.” In Laudato Si, Francis talked about the unique threats marine environments face in a planet changed by humanity. (…)

Ocean acidification

“Carbon dioxide pollution increases the acidification of the oceans and compromises the marine food chain. If present trends continue, this century may well witness…an unprecedented destruction of ecosystems, with serious consequences for all of us.”

Continue reading ‘It’s not just climate — Pope Francis is also warning about the health of our oceans’

Ocean acidification update from a shellfish grower on the front line

Over the past year, there have been many claims about ocean acidification and the impact on oysters. Many of those claims have withered under scrutiny. Taylor Shellfish is on the front line of dealing with environmental issues facing oyster growers. They agreed to answer questions about the current state of science and what they are facing. What follows are their answers and do not reflect our views. After meeting with Bill Dewey of Taylor Shellfish, we felt he provided an interesting perspective and some new information – some that supports and some that contradicts what has been in the public discourse. We don’t endorse everything here, but thought it was an interesting and useful contribution to the discussion.

Bill Dewey manages public affairs for Shelton based Taylor Shellfish Farms. He served on governor Gregoire’s Ocean Acidification Blue Ribbon Panel and serves today on Governor Inslee’s Marine Resources Advisory Council which advises the state’s ocean acidification response.

Continue reading ‘Ocean acidification update from a shellfish grower on the front line’

A transcriptomic analysis of the response of the arctic pteropod Limacina helicina to carbon dioxide-driven seawater acidification

Ocean acidification from the uptake of anthropogenic carbon dioxide (CO2) is regarded as a critical threat particularly to marine calcifying organisms. The arctic pteropod Limacina helicina may be one of the first polar organisms that are expected to display early sensitivity to ocean acidification, but a molecular approach as a foundation for understanding the effect of ocean acidification on this pteropod has rarely been reported. In this study, we examined the sublethal effects of CO2-driven seawater acidification at the transcriptome level in L. helicina. cDNAs, treated under control (pH 8.2), high-CO2 (pH 7.5), and extreme-CO2 (pH 6.5) conditions, generated a total of 31,999,474 reads, comprising a total of 2,271,962,654 bp, using the Illumina platform. De novo assembly yielded 53,121 transcripts comprising 31.79 Mbp. Among the upregulated genes, 346 (0.7 %) and 655 (1.2 %) genes responded to extreme-level CO2 (pH 6.5) and high-level CO2 (pH 7.5), respectively. Also, 76 (0.1 %) transcripts were commonly upregulated in both conditions. Among the downregulated genes, 690 (1.3 %) and 739 (1.4 %) genes were in response to extreme-level CO2 and high-level CO2, respectively. Also, 270 downregulated genes (0.5 %) were affected in both acidic stress conditions. Moreover, 504 transcripts (1 %) of biomineralization-related genes were identified; 16 of these genes showed differential expression in response to acidified seawater. The dataset provides the first comprehensive overview of changes in transcript levels in the arctic pteropod L. helicina in response to increased CO2, emphasizing the potential impact of future environmental change and ocean acidification on Arctic species with external calcified structures.

Continue reading ‘A transcriptomic analysis of the response of the arctic pteropod Limacina helicina to carbon dioxide-driven seawater acidification’

Stress tests for the sea: can fisheries withstand ocean acidification?

Photo credit: A. Obaza (NOAA)

Photo credit: A. Obaza (NOAA)

In the aftermath of the recent global financial crisis, financial regulators began subjecting banks to “stress tests” to determine whether banks and their assets were vulnerable to scenarios such as rising interest rates or falling stock prices. These tests aim to understand the risk inherent in current policies, and how assets will perform if there is a shift from the present day economic environment. The expectation is that such tests will identify areas where adjustment of regulation will avoid an undesirable level of risk. An analogous thought process may benefit fisheries managers struggling to incorporate ocean acidification into their already-complicated list of tasks.

Ocean acidification has the potential to alter marine ecosystems by fundamentally changing their chemistry. Many marine species are sensitive to changes in pH and the concentration of carbon dioxide, carbonate ions, and bicarbonate ions brought about by ocean acidification, However, they differ in the degree of their sensitivity, what physiological functions are altered under acidified conditions, and their expected ability to acclimate or adapt to ocean acidification. Because of the high variability in sensitivity and response to ocean acidification among species, the phenomenon has a strong potential to reorganize marine food webs and ecosystems.

Continue reading ‘Stress tests for the sea: can fisheries withstand ocean acidification?’

PhD opportunity: ”Effect of ocean acidification on natural Southern Ocean phytoplankton communities”, University of Otago, New Zealand

Climate change related stressors such as ocean acidification and ocean warming will expose marine phytoplankton to enormous changes in their environment with so far widely unknown effects on for phytoplankton communities. The majority of research on this topic has concentrated on analyses of a single stressor or a single species in laboratory experiments. This PhD project will investigate multiple stressor effects on natural Southern Ocean phytoplankton communities over the course of at least two years. The collected dataset will be used to model effect of future environmental changes on the Southern Ocean marine ecosystem.

The PhD student will receive training in all aspects of this project from participating in collection of seawater samples on board the Otago research vessel Polaris, using especially designed incubators with precise pH control, and measuring phytoplankton species composition and activity using a combination of different methods including: microscopy, flow cytometry, FRRF, metagenomics, and metatranscriptomics.

The successful applicant would be expected to be eligible for and to apply for a University of Otago PhD scholarship.

Continue reading ‘PhD opportunity: ”Effect of ocean acidification on natural Southern Ocean phytoplankton communities”, University of Otago, New Zealand’


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