Posts Tagged 'algae'

Ocean acidification in the Baltic Sea: involved processes, metrology of pH in brackish waters, and calcification under fluctuating conditions

The oceanic uptake of anthropogenic CO2 emissions counteracts global warming, but comes at the cost of Ocean Acidification, which is a threat to many marine organisms. In the Baltic Sea, the acidification process and its impact could so far not be quantified due to a lack of appropriate pH measurement techniques and the large pH variability. Looking back, in the first focus of this study acidification scenarios are derived from a detailed analysis of past alkalinity trends in the Baltic Sea water, which are put into context of the atmospheric CO2 forcing. In the second focus, the scientific basis for meaningful pH measurements in brackish waters is formed. Therefore, pH buffer solutions are characterized as primary standards and used to calibrate high-quality spectrophotometric pH measurements. In the last focus, pH fluctuations in benthic ecosystems are quantified. The importance of periods with high pH, during which organisms can maintain calcification rates even under acidified conditions, are highlighted.

Continue reading ‘Ocean acidification in the Baltic Sea: involved processes, metrology of pH in brackish waters, and calcification under fluctuating conditions’

Sporophytic photosynthesis and gametophytic growth of the kelp Ecklonia stolonifera affected by ocean acidification and warming

Juvenile sporophytes and gametophytes of Ecklonia stolonifera were incubated in combinations of three pCO2 levels (360, 720 and 980 ppmv) and two temperatures (10 and 15°C for sporophytes; 15 and 20°C for gametophytes) to examine potential effects of climate change on photosynthesis and growth. Sporophytes had significantly higher maximum quantum yields (Fv/Fm) and maximum relative electron transport rates (rETRmax) at 720 ppmv than 360 and 980 ppmv. Also, these parameters were significantly lower at higher temperature of 15°C than at 10°C. Growth of female gametophytes was maximal at 360 ppmv rather than enriched pCO2 levels. Female gametophytes had significantly lower growth at higher temperature of 20°C than at 15°C. These results indicate effects of elevated pCO2 varied between generations: stimulating sporophytic photosynthesis and inhibiting gametophytic growth. Ocean acidification and warming would constitute a grave threat to seedling cultivation of E. stolonifera caused by growth inhibition of gametophytes at high pCO2 levels and temperatures.

Continue reading ‘Sporophytic photosynthesis and gametophytic growth of the kelp Ecklonia stolonifera affected by ocean acidification and warming’

Elevated CO2 leads to enhanced photosynthesis but decreased growth in early life stages of reef building coralline algae

Crustose coralline algae (CCA) are key organisms in coral reef ecosystems, where they contribute to reef building and substrate stabilization. While ocean acidification due to increasing CO2 can affect the biology, physiology and ecology of fully developed CCA, the impacts of elevated CO2 on the early life stages of CCA are much less explored. We assessed the photosynthetic activity and growth of 10-day-old recruits of the reef-building crustose coralline alga Porolithon cf. onkodes exposed to ambient and enhanced CO2 seawater concentration causing a downward shift in pH of ∼0.3 units. Growth of the CCA was estimated using measurements of crust thickness and marginal expansion, while photosynthetic activity was studied with O2 microsensors. We found that elevated seawater CO2 enhanced gross photosynthesis and respiration, but significantly reduced vertical and marginal growth of the early life stages of P. cf. onkodes. Elevated CO2 stimulated photosynthesis, particularly at high irradiance, likely due to increased availability of CO2, but this increase did not translate into increased algal growth as expected, suggesting a decoupling of these two processes under ocean acidification scenarios. This study confirms the sensitivity of early stages of CCA to elevated CO2 and identifies complexities in the physiological processes underlying the decreased growth and abundance in these important coral reef builders upon ocean acidification.

Continue reading ‘Elevated CO2 leads to enhanced photosynthesis but decreased growth in early life stages of reef building coralline algae’

Ability of eelgrass to alter oyster growth and physiology is spatially limited and offset by increasing predation risk

Marine foundation species have strong effects on sympatric species, but the strength may vary along environmental gradients. Climate change is shifting the distribution and magnitude of environmental gradients, making identification of when and where foundation species effects occur necessary for effective management. We reviewed existing work to identify expected mechanisms by which seagrass affect suspension feeding bivalves, then tested whether these effects shifted across estuarine conditions for two species of oysters (native Ostrea lurida and non-native Crassostrea gigas) grown in and out of eelgrass (Zostera marina) at six estuarine sites in Washington state. Hypothesized mechanisms of eelgrass influence include reduced predation pressure, reduced or altered food availability, and amelioration of environmental (pH) stress. We analyzed oyster survival, shell and tissue growth, shell strength, and stable isotope (SI) and fatty acid (FA) biomarkers. Oyster survival was > 20% lower in eelgrass at lower-estuary sites, but not up-estuary sites. Both species grew faster in eelgrass at one low-estuary (higher pH) site, but not elsewhere. Shell strength in eelgrass increased by 21.1% for native but decreased by 12.6% for non-native oysters. FA and SI biomarkers only differed in eelgrass at one site but correlated significantly to growth among individuals. No measurement showed a consistent response to eelgrass across estuarine conditions and taxa, and responses were often opposite of expectations based on published literature. These results have important implications for management and restoration of oysters in areas with eelgrass.

Continue reading ‘Ability of eelgrass to alter oyster growth and physiology is spatially limited and offset by increasing predation risk’

Performance and herbivory of the tropical topshell Trochus histrio under short-term temperature increase and high CO2

Highlights

• Tropical algae-herbivore interactions were studied under a climate change scenario.

• Survival of topshells did not vary but body fitness declined under high CO2.

• Elevated temperature resulted in better physical condition and stimulated herbivory.

• Dynamic index was temperature- and pCO2-interactively dependent.

• Dominance of bottom-up control (i.e. lower grazing pressure) under high CO2.

Abstract

Within tropical environments, short-term impacts of increased seawater temperature and pCO2 on algae-herbivore interactions remain poorly understood. We investigated the isolated and combined 7-day effects of increased temperature (+4 °C) and pCO2 (~1000 μatm) on the trophic interaction Ulva sp./Trochus histrio, by assessing: i) topshells’ survival and condition index; ii) grazer consumption rates, nutritional composition and interaction strength expressed as a dynamic index. No survival differences were observed whilst body condition varied significantly. Topshells under high pCO2 displayed poor performance, concomitant with lower consumption of macroalgae. Individuals exposed to increased temperature had better physical condition, thus stimulating herbivory, which in turn was negatively correlated with carbon and nitrogen contents. The dynamic index was temperature- and pCO2- interactively dependent, suggesting lower grazing pressure under single acidification. Despite some limitations inherent to a short-term exposure, this study provides new insights to accurately predict tropical species’ phenotypic responses in a changing ocean.

Continue reading ‘Performance and herbivory of the tropical topshell Trochus histrio under short-term temperature increase and high CO2’

The potential environmental response to increasing ocean alkalinity for negative emissions

The negative emissions technology, artificial ocean alkalinization (AOA), aims to store atmospheric carbon dioxide (CO2) in the ocean by increasing total alkalinity (TA). Calcium carbonate saturation state (ΩCaCO3) and pH would also increase meaning that AOA could alleviate sensitive regions and ecosystems from ocean acidification. However, AOA could raise pH and ΩCaCO3 well above modern-day levels, and very little is known about the environmental and biological impact of this. After treating a red calcifying algae (Corallina spp.) to elevated TA seawater, carbonate production increased by 60% over a control. This has implication for carbon cycling in the past, but also constrains the environmental impact and efficiency of AOA. Carbonate production could reduce the efficiency of CO2 removal. Increasing TA, however, did not significantly influence Corallina spp. primary productivity, respiration, or photophysiology. These results show that AOA may not be intrinsically detrimental for Corallina spp. and that AOA has the potential to lessen the impacts of ocean acidification. However, the experiment tested a single species within a controlled environment to constrain a specific unknown, the rate change of calcification, and additional work is required to understand the impact of AOA on other organisms, whole ecosystems, and the global carbon cycle.

Continue reading ‘The potential environmental response to increasing ocean alkalinity for negative emissions’

Rising CO2 levels alter the responses of the red macroalga Pyropia yezoensis under light stress

Highlights

• The aquaculture can be effected by light intensity.
• The effects of pCO2 on the production depended on the light intensity changes.
• Pyropia yezoensis might be benefited from ocean acidification at low light.

Abstract

Increased ocean uptake of CO2, due to rising atmospheric CO2 is leading to ocean acidification (OA) and alters light intensity due to increased turbidity and depth variation in seawater. Macroalgae have been found to alter their behavior in response to OA and other climate factors. In order to optimize farming strategies for economically important seaweeds, this study assesses the growth of Pyropia yezoensis at three different light intensities (HL:35%; ML:10%; LL:5%) and two CO2 concentrations (ambient CO2, 400 ppm; elevated CO2, 1000 ppm). Results show that P. yezoensis growth was significantly inhibited by decreased light intensity, due to reductions in photosynthesis, relative electron transfer rate (rETR) and carotenoid synthesis. However, under LL conditions, the relative growth rates (RGR), maximum net photosynthetic rate (Pmax) and maximum relative electron transfer rate (rETRmax) of PSI and PSII in P. yezoensis, were significantly enhanced under elevated CO2 concentrations. Phycocyanin (PC) and phycoerythrin (PE) levels in P. yezoensis were simultaneously increased under elevated CO2 concentrations. This study demonstrates that algal species may adapt to ocean acidification in the future and avoid light-induced growth inhibition.

Continue reading ‘Rising CO2 levels alter the responses of the red macroalga Pyropia yezoensis under light stress’


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Ocean acidification in the IPCC AR5 WG II

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