Aragonite saturation states and pH in western Norwegian fjords: seasonal cycles and controlling factors, 2005–2009

The uptake of anthropogenic carbon dioxide (CO2) by the ocean leads to a process known as ocean acidification (OA), which lowers the aragonite saturation state (ΩAr) and pH, and this is poorly documented in coastal environments including fjords due to lack of appropriate observations.

Here we use weekly underway data from the Voluntary Observing Ships (VOS) program covering the period 2005–2009 combined with data from research cruises to estimate ΩAr and pH values in several adjacent western Norwegian fjords, and to evaluate how seawater CO2 chemistry drives their variations in response to physical and biological factors.

The OA parameters in the surface waters of the fjords are subject to strong seasonal and spatially coherent variations. These changes are governed by the seasonal changes in temperature, salinity, formation and decay of organic matter, and vertical mixing with deeper, carbon-rich coastal water. Annual mean pH and ΩAr values were 8.13 and 2.21, respectively. The former varies from minimum values ( ≈  8.05) in late December – early January to maximum values of around 8.2 during early spring (March–April) as a consequence of the phytoplankton spring bloom, which reduces dissolved inorganic carbon (DIC). In the following months, pH decreases in response to warming. This thermodynamic decrease in pH is reinforced by the deepening of the mixed layer, which enables carbon-rich coastal water to reach the surface, and this trend continues until the low winter values of pH are reached again. ΩAr, on the other hand, reaches its seasonal maximum (> 2.5) in mid- to late summer (July–September), when the spring bloom is over and pH is decreasing. The lowest ΩAr values ( ≈  1.3–1.6) occur during winter (January–March), when both pH and sea surface temperature (SST) are low and DIC is its highest. Consequently, seasonal ΩAr variations align with those of SST and salinity normalized DIC (nDIC).

We demonstrate that underway measurements of fugacity of CO2 in seawater (fCO2) and SST from VOS lines combined with high frequency observations of the complete carbonate system at strategically placed fixed stations provide an approach to interpolate OA parameters over large areas in the fjords of western Norway.

Continue reading ‘Aragonite saturation states and pH in western Norwegian fjords: seasonal cycles and controlling factors, 2005–2009’

Development of Euphausia pacifica (krill) larvae is impaired under pCO2 levels currently observed in the Northeast Pacific

Despite the critical importance of euphausiids in marine food webs, little ocean acidification (OA) research has focused on them. Euphausia pacifica is a dominant and trophically important species of euphausiid throughout the North Pacific and the California Current Ecosystem, where low pH conditions are occurring in advance of those in the global ocean. We assessed the impact of reduced pH on the hatching and larval development of E. pacifica in the laboratory and characterized the pH to which E. pacifica eggs and larvae are currently exposed in Puget Sound, Washington (USA), a large estuary connected to the California Current. In 2 independent sets of laboratory experiments that lasted 6 to 22 d and which involved broods from 110 different females, we found that hatching is robust to a wide range of pH levels, but larval development and survival are reduced at pH levels that are currently observed within their habitat. Survival from 3 d post hatch to the calyptopis 2 stage was reduced by an average of 20% at pH 7.69 compared to pH 7.96. Even though this population experiences a range of pH conditions on seasonal and daily timescales, it may be living near the limits of its pH tolerance. Continued OA may push these organisms past their threshold, which could have cascading negative consequences for higher trophic levels.

Continue reading ‘Development of Euphausia pacifica (krill) larvae is impaired under pCO2 levels currently observed in the Northeast Pacific’

Simulated leakage of high pCO2 water negatively impacts bivalve dominated infaunal communities from the Western Baltic Sea

Carbon capture and storage is promoted as a mitigation method counteracting the increase of atmospheric CO2 levels. However, at this stage, environmental consequences of potential CO2 leakage from sub-seabed storage sites are still largely unknown. In a 3-month-long mesocosm experiment, this study assessed the impact of elevated pCO2 levels (1,500 to 24,400 μatm) on Cerastoderma edule dominated benthic communities from the Baltic Sea. Mortality of C. edule was significantly increased in the highest treatment (24,400 μatm) and exceeded 50%. Furthermore, mortality of small size classes (0–1 cm) was significantly increased in treatment levels ≥6,600 μatm. First signs of external shell dissolution became visible at ≥1,500 μatm, holes were observed at >6,600 μatm. C. edule body condition decreased significantly at all treatment levels (1,500–24,400 μatm). Dominant meiofauna taxa remained unaffected in abundance. Densities of calcifying meiofauna taxa (i.e. Gastropoda and Ostracoda) decreased in high CO2 treatments (>6,600 μatm), while the non – calcifying Gastrotricha significantly increased in abundance at 24,400 μatm. In addition, microbial community composition was altered at the highest pCO2 level. We conclude that strong CO2 leakage can alter benthic infauna community composition at multiple trophic levels, likely due to high mortality of the dominant macrofauna species C. edule.

Continue reading ‘Simulated leakage of high pCO2 water negatively impacts bivalve dominated infaunal communities from the Western Baltic Sea’

A longitudinal study of Pacific oyster (Crassostrea gigas) larval development: isotope shifts during early shell formation reveal sub-lethal energetic stress

Three cohorts of Pacific oyster (Crassostrea gigas) larvae at Whiskey Creek Shellfish Hatchery (WCH) in Netarts Bay, Oregon, were monitored for stable isotope incorporation and biochemical composition: one in May 2011 and two in August 2011. Along with measures of growth and calcification, we present measurements of stable isotopes of carbon in water, algal food, and the shell and tissue, and nitrogen in food and tissue across larval development and growth. These relatively unique measures through larval ontogeny allow us to document isotopic shifts associated with initiation and rate of feeding, and the catabolism of C-rich (lipid) and N-rich (protein) pools. Similar ontological patterns in growth and bulk composition among the cohorts reinforce prior results, suggesting that the creation of the initial shell is energetically expensive, that the major carbon source is ambient dissolved inorganic carbon, and that the major energetic source during this period is maternally derived egg lipids. The May cohort did not isotopically reflect its food source as rapidly as the August cohorts, indicating slower feeding and/or higher catabolism versus anabolism. Our measurements also document differences in bulk turnover of organic carbon and nitrogen pools within the larvae, showing far greater conservation of nitrogen than carbon. These stable isotope and bulk biochemical measurements appear to be more sensitive indicators of sub-lethal environmental stress than the commonly used metrics of development and growth.

Continue reading ‘A longitudinal study of Pacific oyster (Crassostrea gigas) larval development: isotope shifts during early shell formation reveal sub-lethal energetic stress’

Time to wake up: Coral reefs and ocean acidification (video)

Continue reading ‘Time to wake up: Coral reefs and ocean acidification (video)’

Ocean acidification decreases plankton respiration: evidence from a mesocosm experiment (update)

Anthropogenic carbon dioxide (CO2) emissions are reducing the pH in the world’s oceans. The plankton community is a key component driving biogeochemical fluxes, and the effect of increased CO2 on plankton is critical for understanding the ramifications of ocean acidification on global carbon fluxes. We determined the plankton community composition and measured primary production, respiration rates and carbon export (defined here as carbon sinking out of a shallow, coastal area) during an ocean acidification experiment. Mesocosms ( ∼  55 m3) were set up in the Baltic Sea with a gradient of CO2 levels initially ranging from ambient ( ∼  240 µatm), used as control, to high CO2 (up to  ∼  1330 µatm). The phytoplankton community was dominated by dinoflagellates, diatoms, cyanobacteria and chlorophytes, and the zooplankton community by protozoans, heterotrophic dinoflagellates and cladocerans. The plankton community composition was relatively homogenous between treatments. Community respiration rates were lower at high CO2 levels. The carbon-normalized respiration was approximately 40 % lower in the high-CO2 environment compared with the controls during the latter phase of the experiment. We did not, however, detect any effect of increased CO2 on primary production. This could be due to measurement uncertainty, as the measured total particular carbon (TPC) and combined results presented in this special issue suggest that the reduced respiration rate translated into higher net carbon fixation. The percent carbon derived from microscopy counts (both phyto- and zooplankton), of the measured total particular carbon (TPC), decreased from  ∼  26 % at t0 to  ∼  8 % at t31, probably driven by a shift towards smaller plankton (< 4 µm) not enumerated by microscopy. Our results suggest that reduced respiration leads to increased net carbon fixation at high CO2. However, the increased primary production did not translate into increased carbon export, and consequently did not work as a negative feedback mechanism for increasing atmospheric CO2 concentration.

Continue reading ‘Ocean acidification decreases plankton respiration: evidence from a mesocosm experiment (update)’

The Global Ocean Data Analysis Project version 2 (GLODAPv2) – an internally consistent data product for the world ocean

Version 2 of the Global Ocean Data Analysis Project (GLODAPv2) data product is composed of data from 724 scientific cruises covering the global ocean. It includes data assembled during the previous efforts GLODAPv1.1 (Global Ocean Data Analysis Project version 1.1) in 2004, CARINA (CARbon IN the Atlantic) in 2009/2010, and PACIFICA (PACIFic ocean Interior CArbon) in 2013, as well as data from an additional 168 cruises. Data for 12 core variables (salinity, oxygen, nitrate, silicate, phosphate, dissolved inorganic carbon, total alkalinity, pH, CFC-11, CFC-12, CFC-113, and CCl4) have been subjected to extensive quality control, including systematic evaluation of bias. The data are available in two formats: (i) as submitted but updated to WOCE exchange format and (ii) as a merged and internally consistent data product. In the latter, adjustments have been applied to remove significant biases, respecting occurrences of any known or likely time trends or variations. Adjustments applied by previous efforts were re-evaluated. Hence, GLODAPv2 is not a simple merging of previous products with some new data added but a unique, internally consistent data product. This compiled and adjusted data product is believed to be consistent to better than 0.005 in salinity, 1 % in oxygen, 2 % in nitrate, 2 % in silicate, 2 % in phosphate, 4 µmol kg−1 in dissolved inorganic carbon, 6 µmol kg−1 in total alkalinity, 0.005 in pH, and 5 % for the halogenated transient tracers.

The original data and their documentation and doi codes are available at the Carbon Dioxide Information Analysis Center (http://cdiac.ornl.gov/oceans/GLODAPv2/). This site also provides access to the calibrated data product, which is provided as a single global file or four regional ones – the Arctic, Atlantic, Indian, and Pacific oceans – under the doi:10.3334/CDIAC/OTG.NDP093_GLODAPv2. The product files also include significant ancillary and approximated data. These were obtained by interpolation of, or calculation from, measured data. This paper documents the GLODAPv2 methods and products and includes a broad overview of the secondary quality control results. The magnitude of and reasoning behind each adjustment is available on a per-cruise and per-variable basis in the online Adjustment Table.
Continue reading ‘The Global Ocean Data Analysis Project version 2 (GLODAPv2) – an internally consistent data product for the world ocean’


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