Physiological response of Crocosphaera watsonii to enhanced and fluctuating carbon dioxide conditions

We investigated the effects of elevated pCO2 on cultures of the unicellular N2-fixing cyanobacterium Crocosphaera watsonii WH8501. Using CO2-enriched air, cultures grown in batch mode under high light intensity were exposed to initial conditions approximating current atmospheric CO2 concentrations (~400 ppm) as well as CO2 levels corresponding to low- and high-end predictions for the year 2100 (~750 and 1000 ppm). Following acclimation to CO2 levels, the concentrations of particulate carbon (PC), particulate nitrogen (PN), and cells were measured over the diurnal cycle for a six-day period spanning exponential and early stationary growth phases. High rates of photosynthesis and respiration resulted in biologically induced pCO2 fluctuations in all treatments. Despite this observed pCO2 variability, and consistent with previous experiments conducted under stable pCO2 conditions, we observed that elevated mean pCO2 enhanced rates of PC production, PN production, and growth. During exponential growth phase, rates of PC and PN production increased by ~1.2- and ~1.5-fold in the mid- and high-CO2 treatments, respectively, when compared to the low-CO2 treatment. Elevated pCO2 also enhanced PC and PN production rates during early stationary growth phase. In all treatments, PC and PN cellular content displayed a strong diurnal rhythm, with particulate C:N molar ratios reaching a high of 22:1 in the light and a low of 5.5:1 in the dark. The pCO2 enhancement of metabolic rates persisted despite pCO2 variability, suggesting a consistent positive response of Crocosphaera to elevated and fluctuating pCO2 conditions.

Continue reading ‘Physiological response of Crocosphaera watsonii to enhanced and fluctuating carbon dioxide conditions’

Skeletal mineralogy of geniculate corallines: providing context for climate change and ocean acidification research

Marine species depositing high-magnesium (Mg) calcite (>8% MgCO3) are projected to be among the first to show response to the impacts of climate change, i.e. increased sea surface temperature (SST) and ocean acidification (OA), given the increasing solubility of calcite in seawater with increasing Mg content. Temperature is a major driver of Mg incorporation into the skeletons of calcifying macroalgae, and thus climate change may induce deposition of more soluble calcite, exacerbating responses to OA. Assessment of the skeletal Mg content of 3 geniculate, calcifying species of the genera Corallina and Ellisolandia (Rhodophyta, Corallinales), C. officinalis, C. caespitosa and E. elongata, sampled during 2012-2013 in the UK intertidal, demonstrated the existence of seasonal cycles in skeletal Mg. Seasonal cycles in skeletal Mg were also observed for herbarium collections of the Natural History Museum (British Museum), London, sampled during the recent past (1850-2010). Comparative sampling across a northeastern Atlantic latitudinal transect (Iceland to northern Spain) indicated a decreasing Mg content with increasing latitude for present-day C. officinalis, and relationships between SST and Corallina Mg content (r2 = 0.45-0.76) demonstrated the dominant influence of temperature on Corallina species skeletal mineralogy. Corallina and Ellisolandia species show lower absolute values of Mg content (0.11-0.16 mol% Mg/Ca), and smaller variation with change in SST (0.0028-0.0047 mol% Mg/Ca °C-1), than other temperate calcifying macroalgae studied to date. Over the period 1850-2010, no change in the magnitude of Mg incorporation by C. officinalis was detected in herbarium samples. However, the strong relationship between SST and Mg content indicates that projected increases in SST by 2100, which are far greater than temperature increases that occurred between 1850-2010, could have substantial impact on geniculate coralline algae skeletal mineralogy, and must be considered synergistically with the effects of OA.

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Climate experts say ocean acidification is hurting the Belize Barrier Reef

The Belize Barrier Reef is the longest in the Western Hemisphere, and the second-longest in the world. It is also on the frontlines of climate change, with new observed impacts arising from increase ocean acidity.

BELMOPAN, Belize, October 27, 2014 (AMG) — The effects of climate change are weighing heavily on the fishing and tourism industries in Belize, according to experts at the Caribbean Community Climate Change Centre (CCCCC).

Citing increasingly-acidic oceans, the CCCCC has observed declines in marine populations, with a knock-on effect on exports and foreign exchange earnings. The reality is made worse by illegal overfishing and premature harvesting of conch and lobster during the country’s enforced closed seasons.

Ocean acidification occurs when greenhouse gases (GHGs) in the atmosphere are trapped and stored in the ocean as carbonic acid. Calcium in the shells of crustaceans interacts with the carbonic acid forming calcium carbonate, which dissolves crustaceans’ shells – affecting their ability to survive. Coral bleaching, which occurs as a result of warm ocean temperatures, also affects the health of the reefs where much of the marine population lives.

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Effects of ocean acidification on development of Alaskan crab larvae

The oceans absorb a large proportion of the carbon dioxide gas (CO2) emitted into the atmosphere. This CO2 changes the chemistry of seawater to make it more acidic, a phenomenon termed ocean acidification. Ocean acidification can have negative impacts on marine fauna, especially during early life stages, presenting a risk to ecosystems and fisheries. This research tested the effects of ocean acidification on the larval development of three crab species in Alaska: Tanner crab (Chionoecetes bairdi), rock crab (Glebocarcinus oregonensis), and Dungeness crab (Metacarcinus magister). Experiments were undertaken to assess the effects of exposure to low-pH conditions (decrease of up to 0.6 pH units from current levels, range of pH ~8.1 to 7.5) on survival, growth (morphometrics and mass), and carapace mineral composition of larval Tanner, rock, and Dungeness crabs. Results showed a decrease in survival as well as a small but nonsignificant decrease in size of Tanner crabs. There was a small and complex effect of pH on survival of Dungeness crabs. Rock crabs raised in low-pH conditions (pH 7.5) had higher individual biomass than those raised in ambient conditions (pH 8.1). There was no significant impact of pH on mineralization of any species. Therefore, low pH had a negative effect on development of Tanner crabs, a small effect on Dungeness larval survival and no discernible negative effect on rock crab larvae. Differences in response to ocean acidification may be related to pre-adaptation to variable pH conditions through lifestyle such that species that live in deeper, more stable waters (e.g., Tanner crab) are more vulnerable than species living in shallower, more variable waters (e.g., rock and Dungeness crabs). These observations suggest that ocean acidification will have negative impacts on Tanner and Dungeness crab larval survival with potential implications for recruitment to the adult population and consequently, for their fisheries.

Continue reading ‘Effects of ocean acidification on development of Alaskan crab larvae’

Ocean acidification in the aftermath of the Marinoan glaciation

Boron isotope patterns preserved in cap carbonates deposited in the aftermath of the younger Cryogenian (Marinoan, ca. 635 Ma) glaciation confirm a temporary ocean acidification event on the continental margin of the southern Congo craton, Namibia. To test the significance of this acidification event and reconstruct Earth’s global seawater pH states at the Cryogenian-Ediacaran transition, we present a new boron isotope data set recorded in cap carbonates deposited on the Yangtze Platform in south China and on the Karatau microcontinent in Kazakhstan. Our compiled δ11B data reveal similar ocean pH patterns for all investigated cratons and confirm the presence of a global and synchronous ocean acidification event during the Marinoan deglacial period, compatible with elevated postglacial pCO2 concentrations. Differences in the details of the ocean acidification event point to regional distinctions in the buffering capacity of Ediacaran seawater.

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Comparative responses of two dominant Antarctic phytoplankton taxa to interactions between ocean acidification, warming, irradiance, and iron availability

We investigated the responses of the ecologically dominant Antarctic phytoplankton species Phaeocystis antarctica (a prymnesiophyte) and Fragilariopsis cylindrus (a diatom) to a clustered matrix of three global change variables (CO2, mixed-layer depth, and temperature) under both iron (Fe)-replete and Fe-limited conditions based roughly on the Intergovernmental Panel on Climate Change (IPCC) A2 scenario: (1) Current conditions, 39 Pa (380 ppmv) CO2, 50 µmol photons m−2 s−1 light, and 2°C; (2) Year 2060, 61 Pa (600 ppmv) CO2, 100 µmol photons m−2 s−1 light, and 4°C; (3) Year 2100, 81 Pa (800 ppmv) CO2, 150 µmol photons m−2 s−1 light, and 6°C. The combined interactive effects of these global change variables and changing Fe availability on growth, primary production, and cell morphology are species specific. A competition experiment suggested that future conditions could lead to a shift away from P. antarctica and toward diatoms such as F. cylindrus. Along with decreases in diatom cell size and shifts from prymnesiophyte colonies to single cells under the future scenario, this could potentially lead to decreased carbon export to the deep ocean. Fe : C uptake ratios of both species increased under future conditions, suggesting phytoplankton of the Southern Ocean will increase their Fe requirements relative to carbon fixation. The interactive effects of Fe, light, CO2, and temperature on Antarctic phytoplankton need to be considered when predicting the future responses of biology and biogeochemistry in this region.

Continue reading ‘Comparative responses of two dominant Antarctic phytoplankton taxa to interactions between ocean acidification, warming, irradiance, and iron availability’

Deep-water boost for a community exposed to ocean change: Mesocosm experiment on the effects of ocean acidification at its summit

29. October, 2014/ Kiel, Taliarte. In a long-term field study led by GEOMAR Helmholtz Centre for Ocean Research Kiel, an international team of scientists investigates the effects of ocean acidification on pelagic ecosystems in the subtropical Atlantic. The field experiment with the KOSMOS mesocosms off Gran Canary now culminates in the simulation of deep-water upwelling – an event that can boost productivity in these nutrient-starving waters. For this purpose, the researchers developed an 80,000 litres deep-water collector.
How do communities in the nutrient-poor, so-called oligotrophic open ocean react, if the seawater gradually acidifies due to the uptake of human-induced carbon dioxide (CO2)? How are elemental fluxes and interactions in the food web affected, if these high-CO2 exposed communities experience an influx of nutrient-rich deep-water? In a large-scale field experiment, 53 scientists from Germany, Spain, France, Great Britain and the United States are investigating how ocean acidification influences important functions in an ecosystem representative for two-thirds of the world’s oceans. For this experiment, the two German research networks BIOACID (Biological Impacts of Ocean Acidification) and SOPRAN (Surface Ocean Processes in the Anthropocene) cooperate with the Spanish research station Plataforma Oceánica de Canarias (PLOCAN) and the University of Las Palmas de Gran Canaria (ULPGC).

Continue reading ‘Deep-water boost for a community exposed to ocean change: Mesocosm experiment on the effects of ocean acidification at its summit’

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