Changing atmospheric composition due to human activities, primarily carbon dioxide (CO2) emissions from fossil fuel burning, is already impacting ocean circulation, biogeochemistry, and ecology, and model projections indicate that observed trends will continue or even accelerate over this century. Elevated atmospheric CO2 alters Earth’s radiative balance, leading to global-scale warming and climate change. The ocean stores the majority of resulting anomalous heat, which in turn drives other physical, chemical, and biological impacts. Sea surface warming and increased ocean vertical stratification are projected to reduce global-integrated primary production and export flux as well as to lower subsurface dissolved oxygen concentrations. Upper trophic levels will be affected both directly by warming and indirectly from changes in productivity and expanding low oxygen zones. The ocean also absorbs roughly one-quarter of present-day anthropogenic CO2 emissions. The resulting changes in seawater chemistry, termed ocean acidification, include declining pH and saturation state for calcium carbon minerals that may have widespread impacts on many marine organisms. Climate warming will likely slow ocean CO2 uptake but is not expected to significantly reduce upper ocean acidification. Improving the accuracy of future model projections requires better observational constraints on current rates of ocean change and a better understanding of the mechanisms controlling key physical and biogeochemical processes.
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Archive for February, 2014
Historical and future trends in ocean climate and biogeochemistry
Published 19 February 2014 Science 2 CommentsTags: biogeochemistry, chemistry, review
Deep ocean carbonate chemistry and glacial-interglacial atmospheric CO2 changes
Published 19 February 2014 Science ClosedTags: chemistry, paleo, review
Changes in deep ocean carbonate chemistry have profound implications for glacial-interglacial atmospheric CO2 changes. Here, we review deep ocean carbonate ion concentration ([CO32–]) changes based on the benthic foraminiferal boron-to-calcium ratio (B/Ca) and their links to global carbon reorganization since the last ice age. Existing deep ocean [CO32–] reconstructions are consistent with changes in the biological pump, in ocean stratification, and in the associated oceanic alkalinity inventory as key mechanisms for modulating atmospheric CO2 on glacial-interglacial time scales. We find that the global mean deep ocean [CO32–] was roughly similar between the Last Glacial Maximum (LGM; 18,000–22,000 years ago) and the Late Holocene (0–5,000 years ago). In view of elevated glacial surface [CO32–], this indicates enhanced storage of respiratory carbon in a more alkaline deep ocean during the LGM. During early deglaciation, rising [CO32–] at three locations in the deep ocean suggests a release of deep-sea CO2 to the atmosphere, probably via the Southern Ocean. Both increased late deglacial carbonate burial in deep-sea sediments due to elevated [CO32–] and Holocene expansion of coral reefs on newly flooded continental shelves depleted global ocean alkalinity, which reduced CO2 solubility in seawater and contributed to atmospheric CO2 rises at these times.
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“Oceanography” magazine – special issue on changing ocean chemistry
Published 19 February 2014 Science ClosedA special issue of the Oceanography magazine covering the changing ocean chemistry has been recently published online. The special issue features over 20 articles selected and prepared for publishing by two guest editors: John W. Farrington from the Woods Hole Oceanographic Institution and Flip Froelich from the Froelich Education Service. The issue was produced with the support of the US National Science Foundation. The printed version will be available as of March 2014.
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Intercomparison of carbonate chemistry measurements on a cruise in northwestern European shelf seas
Published 19 February 2014 Science ClosedTags: chemistry, field, methods, North Atlantic
Four carbonate system variables were measured in surface waters during a cruise traversing northwestern European shelf seas in the summer of 2011. High resolution surface water data were collected for partial pressure of carbon dioxide (pCO2; using two independent instruments) and pHT, in addition to discrete measurements of total alkalinity and dissolved inorganic carbon. We thus overdetermined the carbonate system (four measured variables, two degrees of freedom) which allowed us to evaluate the level of agreement between the variables. Calculations of carbonate system variables from other measurements generally compared well (Pearson’s correlation coefficient always ≥ 0.94; mean residuals similar to the respective uncertainties of the calculations) with direct observations of the same variables. We therefore conclude that the four independent datasets of carbonate chemistry variables were all of high quality, and as a result that this dataset is suitable to be used for the evaluation of ocean acidification impacts and for carbon cycle studies. A diurnal cycle with maximum amplitude of 41 µatm was observed in the difference between the pCO2 values obtained by the two independent analytical pCO2 systems, and this was partly attributed to irregular seawater flows to the equilibrator and partly to biological activity inside the seawater supply and one of the equilibrators. We discuss how these issues can be addressed to improve carbonate chemistry data quality on research cruises.
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Jackson High School students learn about ocean acidification
Published 19 February 2014 Media coverage Closed
Photo by Roger Kelly
Yeast. Sugar. Water. These ingredients could have been used to bake bread, but as Jackson High School chemistry students recently found out, they can also simulate ocean acidification, a current and future environmental problem.
Ocean acidification is a decrease in the pH of ocean water caused primarily by the absorption of excess carbon dioxide from the atmosphere by the world’s oceans and by pollutants in stormwater runoff.
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Herbivory mediates the expansion of an algal habitat under nutrient and CO2 enrichment
Published 19 February 2014 Science ClosedTags: algae, biological response, BRcommunity, community composition, mollusks, multiple factors, nutrients, otherprocess
Certain environmental conditions facilitate the control of primary producers by herbivores. Environmental change can, therefore, mediate the strength of consumption relative to production such that the abundance of primary producers is altered, potentially driving phase-shifts from one habitat type to another (e.g. the displacement kelp forests by mats of turfs along temperate coasts). Here, we assessed the extent to which herbivores may counter the increased cover of kelp-competitors (i.e. turfs) anticipated to be caused by enriched nutrients and CO2. Specifically, we experimentally enriched nutrients and CO2 and quantified the change in cover of algal turfs in the presence and absence of gastropod grazers. In the absence of grazers, turf algae responded positively to the combination of enriched nutrients and CO2 such that they occupied >95% of available space. In contrast, where grazers were present, sparse covers of algal turfs were maintained even under CO2 and nutrient enrichment (i.e. turfs occupied <5% of available space). This result indicates that consumption by grazers increased where enrichment of nutrients and CO2 facilitated greater algal cover such that cover continued to be largely restricted. By recognising the environmental conditions which will maintain or disrupt the balance between the processes of production and consumption, we may improve forecasts regarding the probability of habitat stasis or shifts.
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Experimental influence of pH on the early life-stages of sea urchins II: increasing parental exposure times gives rise to different responses
Published 19 February 2014 Science ClosedTags: adaptation, biological response, echinoderms, laboratory, methods, morphology, otherprocess, reproduction, survival
Many studies into the responses of early life-stages to ocean acidification utilise offspring obtained from parents reared under present-day conditions. Their offspring are directly introduced to altered-pH conditions. This study determined whether this approach is suitable by pre-exposing parent sea urchins (Psammechinus miliaris) to altered seawater pH (~1000 μatm) for several durations, spawning them and rearing their offspring to settlement. Parents acclimated when exposed to low seawater pH for extended periods (>42 d). Longer adult pre-exposures reduced larval survival and less competent offspring were removed from populations earlier than in controls. Control offspring were larger during earlier development stages (2–7 d), but smaller during later development stages (14 + d) than offspring reared under low pH conditions. Juvenile settlement levels were similar across all treatments. After 17 d, offspring sourced from parents pre-exposed to low pH for 42 and 70 d were larger than those pre-exposed for 28 d and ambient sourced offspring directly transferred to low pH. These different responses show that the use of ambient derived offspring utilised in many studies is likely not an ideal approach when assessing larval development responses via morphometric measurements and survivorship prior to settlement. This study also suggests that calcifying organisms have capacities to acclimate and possibly adapt towards conditions beyond natural rates of ocean acidification.
Continue reading ‘Experimental influence of pH on the early life-stages of sea urchins II: increasing parental exposure times gives rise to different responses’
Direct impacts of near-future ocean acidification on sea urchins
Published 18 February 2014 Science ClosedTags: biological response, echinoderms, morphology, mortality, reproduction, review
Anthropogenic CO2 emissions are acidifying the world’s oceans. A growing body of evidence demonstrates that this ocean acidification can impact survival, growth, development and physiology in marine invertebrates. A few years ago, a global analysis of the literature revealed that echinoderms were surprisingly robust to ocean acidification (Dupont et al., 2010a). An updated semi-quantitative analysis of the literature confirms that sea urchins are resilient to near-future ocean acidification. Direct impacts of ocean acidification on sea urchins are mostly negative but sub-lethal. These include slower somatic and gonadal growth and reflect a shift in energy budgets linked to additional costs of pHe and pHi regulation rather than a direct impact on calcification. This highlights the plasticity of this taxonomic group at levels from molecular to whole organism physiology when facing a changing environment. All life-history stages can be impacted but juveniles are the most sensitive to near-future ocean acidification. Sea urchins also show evidence of acclimation and adaptation potential. However, despite some resilience to ocean acidification in adult and larval stages, strong negative carry-over effects between adult, larval and juvenile stages are likely to compromise the sustainability of some urchin populations. Most of the published evidence are based on short term analyses and focus on single life-history stages, neglecting key processes such as carry-over effects between different life-history stages and generations. As a consequence, the vast majority of published evidence probably underestimates the real impact of ocean acidification. Recommendations for experimental design and future research priorities are discussed.
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Adaptive strategies and environmental significance of lingulid brachiopods across the late Permian extinction
Published 18 February 2014 Science ClosedTags: paleo
Linguliform brachiopods are traditionally considered a conservative group which seems to pass through the late Permian extinction without any significant loss, and even appear to thrive immediately after the extinction peak. In the Southern Alps, lingulids are very common in the post-extinction Mazzin Member (early Induan) of the Werfen Formation. Sparse occurrences are also known in the overlying Siusi and Gastropod Oolite members (late Induan and early Olenekian in age respectively). The recent discovery of well preserved specimens from a pre-extinction bed of the Bellerophon Formation (Changhsingian) has permitted a detailed comparative analysis, mostly based on the interior characters, preserved in the lingulid succession from across the extinction beds. The following effects on the lingulid populations have been analysed: i) change in taxonomic assessment; ii) adaptive strategies during the surviving and recovery phases; iii) environmental proxy connected with the killing mechanisms of the late Permian extinction.
The pre-extinction individuals belong to Lingularia? cf. smirnovae Biernat and Emig, a species that is characterized by large-sized shells with a short lophophoral cavity. The post-extinction populations belong to different species and, probably, even to a different genus. The first post-extinction population (early Induan), with small-sized shells and long lophophoral cavity, has been referred to Lingularia yini (Peng and Shi). It records the most severe effects of the late Permian extinction on the marine ecosystems. The late Induan – Olenekian Lingularia borealis (Bittner), with large sized shells and long lophophoral cavity, appears during the first phase of the Triassic biotic recovery.
The main adaptive strategies of Lingularia yini, in comparison with the Permian species, include: i) shell miniaturization; ii) increasing of the lophophoral cavity surface (respiratory surface); iii) increasing of shell width/length ratio. These modifications are interpreted as adaptations towards warming and hypoxia, two main killing mechanisms of the marine biota. The recovery species Lingularia borealis maintains a large lophophoral cavity, indicating an adaptation towards predominant low oxygenated bottom marine waters.
The appearance and the great abundance of Lingularia yini in the Mazzin Member (early Induan) represents a proxy of dysaerobic conditions, which determined the appearance of the second phase of the Lilliput biota, characterized by the definitive disappearance of the rhynchonelliform brachiopods and calcareous algae in the Southern Alps.
Long-term effects of elevated CO2 and temperature on the Arctic calanoid copepods Calanus glacialis and C. hyperboreus
Published 18 February 2014 Science ClosedTags: Arctic, biological response, crustaceans, laboratory, morphology, mortality, multiple factors, reproduction, respiration, temperature, zooplankton
The sensitivity of copepods to ocean acidification (OA) and warming may increase with time, however, studies >10 days and on synergistic effects are rare. We therefore incubated late copepodites and females of two dominant Arctic species, Calanus glacialis and Calanushyperboreus, at 0 °C at 390 and 3000 μatm pCO2 for several months in fall/winter 2010. Respiration rates, body mass and mortality in both species and life stages did not change with pCO2. To detect synergistic effects, in 2011 C. hyperboreus females were kept at different pCO2 and temperatures (0, 5, 10 °C). Incubation at 10 °C induced sublethal stress, which might have overruled effects of pCO2. At 5 °C and 3000 μatm, body carbon was significantly lowest indicating a synergistic effect. The copepods, thus, can tolerate pCO2 predicted for a future ocean, but in combination with increasing temperatures they could be sensitive to OA.
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Coccolithophores on the north-west European shelf: calcification rates and environmental controls
Published 18 February 2014 Science ClosedTags: abundance, biological response, calcification, community composition, field, multiple factors, North Atlantic, nutrients, otherprocess, phytoplankton
Coccolithophores are a key functional group in terms of the pelagic production of calcium carbonate (calcite), although their contribution to shelf-sea biogeochemistry, and how this relates to environmental conditions, is poorly constrained. Measurements of calcite production (CP) and coccolithophore abundance were made on the north-west European shelf to examine trends in coccolithophore calcification along natural gradients of carbonate chemistry, macronutrient availability and plankton composition. Similar measurements were also made in three bioassay experiments where nutrient (nitrate, phosphate) and pCO2 levels were manipulated. Nanoflagellates (<10 µm) dominated chlorophyll biomass and primary production (PP) at all but one sampling site, with CP ranging from 0.6–9.6 mmolCm-2d-1. Highest CP and coccolithophore cell abundance occurred in a diatom bloom in fully mixed waters off Helgoland, rather than in two distinct coccolithophore blooms in the central North Sea and Western English Channel. Estimates of coccolithophore contributions to total PP and nanoplankton PP were generally <5 %, apart from in a coccolithophore bloom at the Western English Channel Observatory (E1) where coccolithophores contributed up to 11 % and at Helgoland where they contributed ∼23 % to nanoplankton PP. Variability in CP was influenced by cell numbers, species composition and cell-normalised calcification rates under both in situ conditions and in the experimental bioassays. Water column structure and light availability had a strong influence on cellular calcification, whereas nitrate (N) to phosphate (P) ratios influenced bulk CP. Coccolithophore communities in the northern North Sea and over the Norwegian Trench showed responses to N and P addition whereas oceanic communities in the Bay of Biscay showed no response. Sharp decreases in pH and a rough halving of calcite saturation states in the bioassay experiments led to decreased CP in the Bay of Biscay and Northern North Sea, but not over the Norwegian Trench. These variable relationships to nutrient availability and changes in carbonate chemistry highlight the complex response of coccolithophore physiology to growth environment.
Can technological advances help acidifying seas?
MANY scientists are increasingly acknowledging that we can no longer afford to dismiss some gee-whiz technological fixes outright. We need to understand what, if any of it, could help.
In 2012, a controversial California entrepreneur motored off the coast of British Columbia and dumped 100 tonnes of iron dust into the Pacific Ocean, hoping to spark a 360sqkm plankton bloom. Scientists around the world were outraged. The broad-scale move to scrub carbon dioxide from a patch of water by stimulating plant growth took place with no input from the international community.
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Otters, ecosystems and ocean acidification in Washington waters: Free Educator Workshop
Published 17 February 2014 Courses and training ClosedThe workshop is focused on teachers of grades 3-7.
Saturday, March 1, 2014, 8:30 AM – 3:30 PM (Six clock hours available)
Seattle Aquarium, 1483 Alaska Way, Seattle, WA 98101
Join KCTS 9 QUEST Northwest, Seattle Aquarium and Taylor Shellfish for a free teacher workshop that will explore otters, ecosystems and ocean acidification in Washington waters. The workshop will include keynote speaker Dr. Shawn Larson, Curator of Conservation and Research at Seattle Aquarium, discussing her research of sea otter populations in Washington. The workshop will also introduce classroom activities and resources on ocean acidification and ecosystems of Puget Sound. Light breakfast a nd afternoon snacks will be provided. Parking and clock hours will be reimbursed.
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20 facts about ocean acidification – now available in French, Spanish and German
Published 14 February 2014 Science Closed
Polar coralline algal CaCO3-production rates correspond to intensity and duration of the solar radiation (update)
Published 14 February 2014 Science ClosedTags: algae, Arctic, biological response, calcification, field
In this study we present a comparative quantification of CaCO3 production rates by rhodolith-forming coralline red algal communities situated in high polar latitudes and assess which environmental parameters control these production rates. The present rhodoliths act as ecosystem engineers, and their carbonate skeletons provide an important ecological niche to a variety of benthic organisms. The settings are distributed along the coasts of the Svalbard archipelago, being Floskjeret (78°18′ N) in Isfjorden, Krossfjorden (79°08′ N) at the eastern coast of Haakon VII Land, Mosselbukta (79°53′ N) at the eastern coast of Mosselhalvøya, and Nordkappbukta (80°31′ N) at the northern coast of Nordaustlandet. All sites feature Arctic climate and strong seasonality.
The algal CaCO3 production rates were calculated from fuchsine-stained, presumably annual growth increments exhibited by the rhodoliths and range from 100.9 g (CaCO3) m−2 yr−1 at Nordkappbukta to 200.3 g (CaCO3) m−2 yr−1 at Floskjeret. The rates correlate to various environmental parameters with geographical latitude being the most significant (negative correlation, R2 = 0.95, p = 0.0070), followed by the duration of the polar night (negative correlation, R2 = 0.93, p = 0.0220), the duration of the sea ice cover (negative correlation, R2 = 0.87, p = 0.0657), and the annual mean temperature (positive correlation, R2 = 0.48, p = 0.0301).
This points out sufficient light incidence to be the main control of the growth of the examined coralline red algal rhodolith communities, while temperature is less important. Thus, the ongoing global change with its rising temperatures will most likely result in impaired conditions for the algae, because the concomitant increased global runoff will decrease water transparency and hence light incidence at the four offshore sites. Regarding the aforementioned role of the rhodoliths as ecosystem engineers, the impact on the associated organisms will presumably also be negative.
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Meeting the eye-witnesses of ocean change (press release)
Published 13 February 2014 Press releases ClosedScientists team up with fishing industry, government agencies and tourism sector to model socio-economic impacts of ocean acidification.
Members of the German research network BIOACID (Biological Impacts of Ocean Acidification) are developing a model that links ecosystem changes triggered by ocean acidification and climate change with their economic and societal consequences. Workshops and interviews with stakeholders from the Norwegian fishing industry and tourism sector, the government and environmental organisations help them to identify key aspects for their assessment.
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Acclimatization of the crustose coralline alga Porolithon onkodes to variable pCO2
Published 13 February 2014 Science ClosedTags: adaptation, algae, biological response, calcification, mesocosms, otherprocess, primary production, respiration, South Pacific
Ocean acidification (OA) has important implications for the persistence of coral reef ecosystems, due to potentially negative effects on biomineralization. Many coral reefs are dynamic with respect to carbonate chemistry, and experience fluctuations in pCO2 that exceed OA projections for the near future. To understand the influence of dynamic pCO2 on an important reef calcifier, we tested the response of the crustose coralline alga Porolithon onkodes to oscillating pCO2. Individuals were exposed to ambient (400 µatm), high (660 µatm), or variable pCO2 (oscillating between 400/660 µatm) treatments for 14 days. To explore the potential for coralline acclimatization, we collected individuals from low and high pCO2 variability sites (upstream and downstream respectively) on a back reef characterized by unidirectional water flow in Moorea, French Polynesia. We quantified the effects of treatment on algal calcification by measuring the change in buoyant weight, and on algal metabolism by conducting sealed incubations to measure rates of photosynthesis and respiration. Net photosynthesis was higher in the ambient treatment than the variable treatment, regardless of habitat origin, and there was no effect on respiration or gross photosynthesis. Exposure to high pCO2 decreased P. onkodes calcification by >70%, regardless of the original habitat. In the variable treatment, corallines from the high variability habitat calcified 42% more than corallines from the low variability habitat. The significance of the original habitat for the coralline calcification response to variable, high pCO2 indicates that individuals existing in dynamic pCO2 habitats may be acclimatized to OA within the scope of in situ variability. These results highlight the importance of accounting for natural pCO2 variability in OA manipulations, and provide insight into the potential for plasticity in habitat and species-specific responses to changing ocean chemistry.
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Physiology and biogeochemistry of corals subjected to repeat bleaching and combined ocean acidification and warming
Published 13 February 2014 Science ClosedTags: biological response, calcification, corals, laboratory, multiple factors, physiology, temperature
Rising atmospheric CO2 concentrations threaten coral reefs worldwide by causing ocean warming and acidification. When seawater temperatures are unusually high, corals lose a significant portion of their vital algal endosymbionts and/or photosynthetic pigments making them appear pale or white – a process referred to as coral bleaching. As corals get most of their carbon from the algal endosymbionts, the breakdown of this symbiosis significantly weakens coral and can lead to widespread mortality if bleaching is severe. Bleaching events have been predicted to become annual events sometime later this century. Despite this knowledge, the impacts of annual bleaching on coral physiology, biogeochemistry, and overall resilience remain largely unknown. For the first time, annually recurring bleaching was simulated on ecologically relevant timescales by subjecting three Caribbean coral species (Orbicella faveolata, Porites astreoides, and Porites divaricata) to experimental coral bleaching (+1°C for 2.5 weeks) in two consecutive years. Impacts on their physiology and biogeochemistry were assessed in great detail immediately after repeat bleaching as well as after short and long term recovery. We show that repeat bleaching can dramatically alter thermal tolerance of the coral holobiont (i.e., animal host and endosymbiont). Species such as P. divaricata will be able to rapidly acclimate to frequent temperature stress and persist on future coral reefs, whereas others such as P. astreoides will show increasing bleaching susceptibility and may thus face significant decline.
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Temperature modulates coccolithophorid sensitivity of growth, photosynthesis and calcification to increasing seawater pCO2
Published 13 February 2014 Science ClosedTags: biological response, calcification, growth, laboratory, multiple factors, photosynthesis, primary production, temperature
Increasing atmospheric CO2 concentrations are expected to impact pelagic ecosystem functioning in the near future by driving ocean warming and acidification. While numerous studies have investigated impacts of rising temperature and seawater acidification on planktonic organisms separately, little is presently known on their combined effects. To test for possible synergistic effects we exposed two coccolithophore species, Emiliania huxleyi and Gephyrocapsa oceanica, to a CO2 gradient ranging from ~0.5–250 µmol kg−1 (i.e. ~20–6000 µatm pCO2) at three different temperatures (i.e. 10, 15, 20°C for E. huxleyi and 15, 20, 25°C for G. oceanica). Both species showed CO2-dependent optimum-curve responses for growth, photosynthesis and calcification rates at all temperatures. Increased temperature generally enhanced growth and production rates and modified sensitivities of metabolic processes to increasing CO2. CO2 optimum concentrations for growth, calcification, and organic carbon fixation rates were only marginally influenced from low to intermediate temperatures. However, there was a clear optimum shift towards higher CO2 concentrations from intermediate to high temperatures in both species. Our results demonstrate that the CO2 concentration where optimum growth, calcification and carbon fixation rates occur is modulated by temperature. Thus, the response of a coccolithophore strain to ocean acidification at a given temperature can be negative, neutral or positive depending on that strain’s temperature optimum. This emphasizes that the cellular responses of coccolithophores to ocean acidification can only be judged accurately when interpreted in the proper eco-physiological context of a given strain or species. Addressing the synergistic effects of changing carbonate chemistry and temperature is an essential step when assessing the success of coccolithophores in the future ocean.
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Calcification patterns of the coccolithophore Coccolithus braarudii (Haptophyta), from the late Quaternary to present in the Southern Ocean
Published 13 February 2014 Science ClosedTags: biological response, morphology, paleo, phytoplankton
Ocean acidification, caused by a decrease in pH due to elevated anthropogenic CO2 input from the atmosphere into the ocean, is the focus of intense current research with regard to biological impacts. Allegedly, the most affected species will be those that produce hard calcite and aragonite shells. In the present study, we assessed calcification and morphometry of the large-sized, heavily calcified coccolithophore genus Coccolithus, in the Southern Ocean, south of Tasmania. Firstly, we characterised the species, past and present, in the Southern Ocean using the following source materials: fossil core-top material from Core GC07 (South Tasman Rise); recent sediment trap samples collected during Sept 2003 – Feb 2004 from the Subantarctic Zone (SAZ) south of the subtropical front (STF); and two newly isolated culture strains from coastal Tasmania. Results showed that only a single taxon , designated Coccolithus braarudii [(Gaarder, 1962) Baumann et al., 2003] sensu Geisen et al. (2002) and Young et al., (2003), was consistently present in the Southern Ocean, with coccolith length ranging from 10-16 μm and consistent presence of a central bar across the central area.
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