Living Planet: cold-water corals in a warming climate (audio)

Much of the CO2 we emit through the burning of fossil fuels ends up in the ocean, making the water more acidic. Because ocean acidification happens particularly fast in cold water, that spells trouble for cold-water corals. How do they cope as their environment becomes warmer and more acidic?

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Die Auswirkungen von Ozeanversauerung auf Fischbestände (in German)

Ein Expertenbeitrag von Dr. Catriona Clemmesen-Bockelmann, GEOMAR Helmholtz Zentrum für Ozeanforschung in Kiel

Der Gehalt an Kohlendioxid (CO2) in der Atmosphäre hat sich seit der industriellen Revolution im 19. Jahrhundert von 280 ppm (parts per million = Millionstel) auf heute 400 ppm erhöht. Wenn die momentanen anthropogenen Emissionen wie bisher fortgeführt werden, wird der CO2-Gehalt in der Atmosphäre 900 ppm im Jahre 2100 übertreffen. Diese Erkenntnis zeigt, dass Veränderungen heute in einer Geschwindigkeit ablaufen, die es bisher nicht gegeben hat. Zwar sind die Meere in der Lage, einen Teil dieses anthropogen produzierten CO2 zu absorbieren. Da CO2 sich aber nicht wie Sauerstoff einfach im Wasser löst, sondern mit Wasser reagiert, bilden sich über einen Zwischenschritt Wasserstoff-Ionen, die das Meer saurer machen (Verringerung des pH Wertes). Wir sprechen daher von Ozeanversauerung. Neben der Versauerung führt eine Zunahme des CO2-Gehaltes in der Atmosphäre gleichzeitig zu einer Temperaturerhöhung in den Ozeanen.

Continue reading ‘Die Auswirkungen von Ozeanversauerung auf Fischbestände (in German)’

Calcium carbonate (CaCO3) sediment dissolution under elevated concentrations of carbon dioxide (CO2) and nitrate (NO3−)

Ocean acidification (OA), attributed to the sequestration of atmospheric carbon dioxide (CO2) into the surface ocean, and coastal eutrophication, attributed in part to land-use change and terrestrial runoff of fertilizers, have received recent attention in an experimental framework examining the effects of each on coral reef net ecosystem calcification (Gnet). However, OA and eutrophication in conjunction have yet to receive attention from the perspective of coral reef sediment dissolution. To address this omission, CO2 and nitrate (NO3−) addition experiments were performed in Mo’orea, French Polynesia. Incubation chambers were used to measure sediment Gnet during the day and night under three different [NO3−] (0, 9.8, and 19.7 μM) that were nested within four separate constructed coral reef communities maintained at different PCO2 levels (417, 721, 1030, and 1333 μatm, respectively). PCO2 negatively affected sediment Gnetduring the day and night, resulting in a shift to diel net dissolution at a PCO2 of 1030 μatm. Elevated NO3− alone, and the combination of NO3− and PCO2, both negatively affected sediment Gnet at night. However, the response of Gnet to NO3− was less clear during the day, where diurnal sediment Gnet was enhanced under the combined treatment of elevated NO3− and PCO2, resulting in no net effect of NO3− on sediment Gnet on diel timescales. Overall, these results show that ocean acidification represents a greater threat to the balance of calcification and dissolution in Mo’orea’s back reef sediment communities than the potential impact of NO3− enrichment on relatively short timescales.

Continue reading ‘Calcium carbonate (CaCO3) sediment dissolution under elevated concentrations of carbon dioxide (CO2) and nitrate (NO3−)’

Effects of acidified seawater on calcification, photosynthetic efficiencies and the recovery processes from strong light exposure in the coral Stylophora pistillata

The aim of this study was to investigate whether coral photosynthetic efficiencies and recovery processes are affected by CO2-driven ocean acidification in symbiont photosynthesis and coral calcification. We investigated the effects of five CO2 partial pressure (pCO2) levels in adjusted seawater ranging from 300 μatm (pre-industrial) to 800 μatm (near-future) and strong and weak light intensity on maximum photosynthetic efficiency and calcification of a branching coral, Stylophora pistillata, as this species has often been used in rearing experiments to investigate the effects of acidified seawater on calcification and photosynthetic algae of corals. We found that, the photosynthetic efficiencies and recovery patterns under different light conditions did not differ among pCO2 treatments. Furthermore, calcification of S. pistillata was not affected by acidified seawater under weak or strong light conditions. Our results indicate that the photosynthetic efficiency and calcification of S. pistillata are insensitive to changes in ocean acidity.

Continue reading ‘Effects of acidified seawater on calcification, photosynthetic efficiencies and the recovery processes from strong light exposure in the coral Stylophora pistillata’

Calcifying response and recovery potential of the brown alga Padina pavonica under ocean acidification

Anthropogenic CO2 emissions are causing ocean acidification (OA), which affects calcifying organisms. Recent studies have shown that Padina pavonica investigated along a natural pCO2 gradient seems to acclimate to OA by reducing calcified structures and changing mineralogy from aragonite to calcium sulphate salts. The aim of the present study was to study the potential for acclimation of P. pavonica to OA along the same gradient and in aquaria under controlled conditions. P. pavonica was cross-transplanted for one week from a normal pH site (median value: pHTS = 8.1; pCO2 = 361 μatm) to a low pH site (median value: pHTS = 7.4; pCO2 = 1025 μatm) and vice versa. Results showed that this calcifying alga did survive under acute environmental pHTS changes but its calcification was significantly reduced. P. pavonica decalcified and changed mineralogy at pHTS = 7.4, but once brought back at pHTS = 8.1 it partially recovered the aragonite loss while preserving the calcium sulphate minerals that formed under low pHTS. These results suggest that P. pavonica could be used as a bio-indicator for monitoring OA, as well as localized anthropogenic acidity fluctuations.

Continue reading ‘Calcifying response and recovery potential of the brown alga Padina pavonica under ocean acidification’

Solar UVR sensitivity of phyto- and bacterioplankton communities from Patagonian coastal waters under increased nutrients and acidification

The effects of ultraviolet radiation (UVR) under future expected conditions of acidification and increase in nutrient inputs were studied on a post-bloom phytoplankton and bacterioplankton community of Patagonian coastal waters. We performed an experiment using microcosms where two environmental conditions were mimicked using a cluster approach: present (ambient nutrients and pH) and future (increased nutrients and acidification), and acclimating the samples for five days to two radiation treatments (full solar radiation [+UVR] and exclusion of UVR [–UVR]). We evaluated the short-term (hours) sensitivity of the community to solar UVR through chlorophyll afluorescence parameters (e.g. the effective photochemical quantum yield of PSII [ΦPSII]) at the beginning, at the mid-point and at the end of the acclimation period. Primary production and heterotrophic bacterial production (HBP) were determined, and biological weighting functions were calculated, at the beginning and at the end of the acclimation period. Mid-term effects (days) were evaluated as changes in taxonomic composition, growth rates and size structure of the community. Although the UVR-induced inhibition on ΦPSII decreased in both clusters, samples remained sensitive to UVR after the 5 days of acclimation. Also, under the future conditions, there was, in general, an increase in the phytoplankton carbon incorporation rates along the experiment as compared to the present conditions. Bacterioplankton sensitivity to UVR changed along the experiment from inhibition to enhancement of HBP, and future environmental conditions stimulated bacterial growth, probably due to indirect effects caused by phytoplankton. Those changes in the microbial loop functioning and structure under future global change conditions might have important consequences for the carbon pump and thus for the carbon sequestration and trophodynamics of Patagonian coastal waters.

Continue reading ‘Solar UVR sensitivity of phyto- and bacterioplankton communities from Patagonian coastal waters under increased nutrients and acidification’

Decreased pH and increased temperatures affect young-of-the-year red king crab (Paralithodes camtschaticus)

The red king crab (Paralithodes camtschaticus) is a high-latitude commercially important species with a complex life-history cycle which encompasses a wide variety of conditions and habitats. High-latitude waters, including those around Alaska where red king crab live, are predicted to have increased ocean acidification and temperatures in comparison to other areas. The interaction of ocean acidification and increased temperature has not been examined for any life history stage of red king crab. To determine the effects of near-future ocean acidification and warming temperature on young-of-the-year red king crab survival, growth, and morphology, we conducted a long-term (184 d) fully crossed experiment with two pHs and three temperatures: ambient pH (∼7.99), pH 7.8, ambient temperature, ambient +2 °C, and ambient +4 °C, for a total of six treatments. Mortality increased with exposure to reduced pH and higher temperatures, but a clear trend in the interactive effects of the stressors was not observed. A synergetic effect on mortality was observed in the pH 7.8 and ambient +4 °C temperature treatment. This treatment also had the lowest survival with only 3% surviving to the end of the experiment. However, an antagonistic effect on mortality was observed in the pH 7.8 and ambient +2 °C treatment. Lower pH and warmer temperatures affected intermoult duration, only temperature affected percent increase in size, but carapace length was not affected. Decreased pH and increased temperature had no effect on morphology. The results of this study combined with other studies show that decreased pH and warming has profound negative effects on red king crab. Unless the species is able to adapt or acclimate to changing climate conditions, red king crabs populations may decrease in the upcoming decades due to ocean acidification and rising temperatures.

Continue reading ‘Decreased pH and increased temperatures affect young-of-the-year red king crab (Paralithodes camtschaticus)’


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Ocean acidification in the IPCC AR5 WG II

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