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Combined effects of global climate change and nutrient enrichment on the physiology of three temperate maerl species

Made up of calcareous coralline algae, maerl beds play a major role as ecosystem engineers in coastal areas throughout the world. They undergo strong anthropogenic pressures, which may threaten their survival. The aim of this study was to gain insight into the future of maerl beds in the context of global and local changes. We examined the effects of rising temperatures (+3°C) and ocean acidification (−0.3 pH units) according to temperature and pH projections (i.e., the RCP 8.5 scenario), and nutrient (N and P) availability on three temperate maerl species (Lithothamnion corallioides, Phymatolithon calcareum, and Lithophyllum incrustans) in the laboratory in winter and summer conditions. Physiological rates of primary production, respiration, and calcification were measured on all three species in each treatment and season. The physiological response of maerl to global climate change was species‐specific and influenced by seawater nutrient concentrations. Future temperature–pH scenario enhanced maximal gross primary production rates in P. calcareum in winter and in L. corallioides in both seasons. Nevertheless, both species suffered an impairment of light harvesting and photoprotective mechanisms in winter. Calcification rates at ambient light intensity were negatively affected by the future temperature–pH scenario in winter, with net dissolution observed in the dark in L. corallioides and P. calcareum under low nutrient concentrations. Nutrient enrichment avoided dissolution under future scenarios in winter and had a positive effect on L. incrustans calcification rate in the dark in summer. In winter conditions, maximal calcification rates were enhanced by the future temperature–pH scenario on the three species, but P. calcareum suffered inhibition at high irradiances. In summer conditions, the maximal calcification rate dropped in L. corallioides under the future global climate change scenario, with a potential negative impact on CaCO3 budget for maerl beds in the Bay of Brest where this species is dominant. Our results highlight how local changes in nutrient availability or irradiance levels impact the response of maerl species to global climate change and thus point out how it is important to consider other abiotic parameters in order to develop management policies capable to increase the resilience of maerl beds under the future global climate change scenario.

Continue reading ‘Combined effects of global climate change and nutrient enrichment on the physiology of three temperate maerl species’

The effects of co-exposure of graphene oxide and copper under different pH conditions in Manila clam Ruditapes philippinarum

Carbon nanomaterials (CNM), such as graphene oxide (GO), have been the focus of study in several areas of science mostly due to their physical-chemical properties. However, data concerning the potential toxic effects of these CNM in bivalves are still scarce. When present in the aquatic systems, the combination with other contaminants, as well as pH environmental variations, can influence the behavior of these nanomaterials and, consequently, their toxicity. Thus, the main goal of this study was to evaluate the effect of exposure of clam Ruditapes philippinarum to GO when acting alone and in the combination with copper (Cu), under two pH levels (control 7.8 and 7.3). A 28-day exposure was performed and metabolism and oxidative stress-related parameters were evaluated. The effects caused by GO and Cu exposures, either isolated or co-exposed, showed a direct and dependent relationship with the pH in which the organisms were exposed. In clams maintained at control pH (7.8), Cu and GO + Cu treatments showed lower lipid peroxidation (LPO) and lower electron transport system (ETS) activity, respectively. In clams maintained at low pH, glutathione-S-transferases (GSTs) activities were increased in Cu and Cu + GO treatments, whereas reduced glutathione (GSH) levels were increased in Cu treatment and ETS activity was higher in GO + Cu. Thus, it can be observed that clams responses to Cu and GO were strongly modulated by pH in terms of their defense system and energy production, although this does not result into higher LPO levels.

Continue reading ‘The effects of co-exposure of graphene oxide and copper under different pH conditions in Manila clam Ruditapes philippinarum’

Attributing ocean acidification to major carbon producers

Recent research has quantified the contributions of CO2 and CH4 emissions traced to the products of major fossil fuel companies and cement manufacturers to global atmospheric CO2, surface temperature, and sea level rise. This work has informed societal considerations of the climate responsibilities of these major industrial carbon producers. Here, we extend this work to historical (1880–2015) and recent (1965–2015) acidification of the world’s ocean. Using an energy balance carbon-cycle model, we find that emissions traced to the 88 largest industrial carbon producers from 1880–2015 and 1965–2015 have contributed ~55% and ~51%, respectively, of the historical 1880–2015 decline in surface ocean pH. As ocean acidification is not spatially uniform, we employ a three-dimensional ocean model and identify five marine regions with large declines in surface water pH and aragonite saturation state over similar historical (average 1850–1859 to average 2000–2009) and recent (average 1960–1969 to average of 2000–2009) time periods. We characterize the biological and socioeconomic systems in these regions facing loss and damage from ocean acidification in the context of climate change and other stressors. Such analysis can inform societal consideration of carbon producer responsibility for current and near-term risks of further loss and damage to human communities dependent on marine ecosystems and fisheries vulnerable to ocean acidification.

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Dynamic response in the larval geoduck (Panopea generosa) proteome to elevated pCO2

Pacific geoducks (Panopea generosa) are clams found along the northeast Pacific
coast where they are important components of coastal and estuarine ecosystems
and a major aquaculture product. The Pacific coastline, however, is also experiencing rapidly changing ocean habitat, including significant reductions in pH. To better understand the physiological impact of ocean acidification on geoduck clams, we characterized for the first time the proteomic profile of this bivalve during larval development and compared it to that of larvae exposed to low pH conditions. Geoduck larvae were reared at pH 7.5 (ambient) or pH 7.1 in a commercial shellfish hatchery from day 6 to day 19 postfertilization and sampled at six time points for an in-depth proteomics analysis using high-resolution data-dependent analysis. Larvae reared at low pH were smaller than those reared at ambient pH, especially in the prodissoconch II phase of development, and displayed a delay in their competency for settlement. Proteomic profiles revealed that metabolic, cell cycle, and protein turnover pathways differed between the two pH and suggested that differing phenotypic outcomes between pH 7.5 and 7.1 are likely due to environmental disruptions to the timing of physiological events. In summary, ocean acidification results in elevated energetic demand on geoduck larvae, resulting in delayed development and disruptions to normal molecular developmental pathways, such as carbohydrate metabolism, cell growth, and protein synthesis.

Continue reading ‘Dynamic response in the larval geoduck (Panopea generosa) proteome to elevated pCO2’

The effect of elevated CO2 on the production and respiration of a Sargassum thunbergii community: a mesocosm study

Approximately one‐third of anthropogenic carbon dioxide is absorbed into the ocean and causes it to become more acidic. The Intergovernmental Panel on Climate Change (IPCC) suggested that the surface ocean pH, by the year 2100, would drop by a further 0.3 and 0.4 pH units under RCP (Representative Concentration Pathway) 6.0 and 8.5 climate scenarios. The macroalgae communities that consisted of Sargassum thunbergii and naturally attached epibionts were exposed to fluctuations of ambient and manipulated pH (0.3–0.4 units below ambient pH). The production and respiration in S. thunbergii communities were calculated from dissolved oxygen time‐series recorded with optical dissolved oxygen sensors. The pH, irradiance, and dissolved oxygen occurred in parallel with diurnal (day/night) patterns. According to net mesocosm production – photosynthetically active radiation (PAR) model, the saturation and compensation PAR, the mean maximum gross mesocosm production (GMP), and daily mesocosm respiration were higher in the CO2 enrichment, than in the ambient condition, while the mean of photosynthetic coefficient was similar. In conclusion, elevated CO2 stimulated oxygen production and consumption of S. thunbergii communities in the mesocosm. Furthermore, the sensitivity of the GMP of the S. thunbergii community to irradiance was reduced, and achieved maximum production rate at higher PAR. These positive responses to CO2 enrichment suggest that S. thunbergii communities may thrive in under high CO2 conditions.

Continue reading ‘The effect of elevated CO2 on the production and respiration of a Sargassum thunbergii community: a mesocosm study’

Call for proposals: Ocean Acidification Information Exchange microgrants

The mission of the Ocean Acidification Information Exchange is to respond and adapt to ocean and coastal acidification by fostering an online environment built on trust, where our members, regardless of background, feel empowered to ask, answer, and learn from one another. By promoting the collegial exchange of information across disciplines and geographical boundaries, our goal is to facilitate the creation of more holistic, effective response strategies and share lessons learned. To that end, we are offering grants for members of the site who propose innovative strategies for leveraging the OA Information Exchange’s collaboration tools to advance our community’s mission, facilitate their own work related to ocean and coastal acidification and expand the reach/utility of the OA Information Exchange.

Project Ideas:
These are provided as examples of projects that would likely receive funding based on the criteria of this RFP.

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Simulated CO2-induced ocean acidification for ocean in the East China: historical conditions since preindustrial time and future scenarios

Since preindustrial times, as atmospheric CO2 concentration increases, the ocean continuously absorbs anthropogenic CO2, reducing seawater pH and [CO2−3], which is termed ocean acidification. We perform Earth system model simulations to assess CO2-induced acidification for ocean in the East China, one of the most vulnerable areas to ocean acidification. By year 2017, ocean surface pH in the East China drops from the preindustrial level of 8.20 to 8.06, corresponding to a 35% rise in [H+], and reduction rate of pH becomes faster in the last two decades. Changes in surface seawater acidity largely result from CO2-induced changes in surface dissolved inorganic carbon (DIC), alkalinity (ALK), salinity and temperature, among which DIC plays the most important role. By year 2300, simulated reduction in sea surface [CO2−3] is 13% under RCP2.6, contrasted to 72% under RCP8.5. Furthermore, simulated results show that CO2-induced warming acts to mitigate reductions in [CO2−3], but the individual effect of oceanic CO2 uptake is much greater than the effect of CO2-induced warming on ocean acidification. Our study quantifies ocean acidification induced by anthropogenic CO2, and indicates the potentially important role of accelerated CO2 emissions in projections of future changes in biogeochemistry and ecosystem of ocean in the East China.

Continue reading ‘Simulated CO2-induced ocean acidification for ocean in the East China: historical conditions since preindustrial time and future scenarios’

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Ocean acidification in the IPCC AR5 WG II

OUP book