Posts Tagged 'laboratory'



Limited response of a spring bloom community inoculated with filamentous cyanobacteria to elevated temperature and pCO2

Temperature and CO2 levels are projected to increase in the future, with consequences for carbon and nutrient cycling in brackish environments, such as the Baltic Sea. Moreover, filamentous cyanobacteria are predicted to be favored over other phytoplankton groups under these conditions. Under a 12-day outdoor experiment, we examined the effect on a natural phytoplankton spring bloom community of elevated temperature (from 1°C to 4°C) and elevated pCO2 (from 390 to 970 μatm). No effects of elevated pCO2 or temperature were observed on phytoplankton biovolumes, but a significantly higher photosystem II activity was observed at elevated temperature after 9 days. In addition, three species of diazotrophic filamentous cyanobacteria were inoculated to test their competitive capacity under spring bloom conditions. The toxic cyanobacterium Nodularia spumigena exhibited an average specific growth rate of 0.10 d−1 by the end of the experiment, indicating potential prevalence even during wintertime in the Baltic Sea. Generally, none of the inoculated cyanobacteria species were able to outcompete the natural phytoplankton species at temperatures ≤4°C. No direct effects were found on heterotrophic bacteria. This study demonstrates the highly efficient resistance towards short-term (12 days) changes in abiotic factors by the natural Baltic Sea spring bloom community.

Continue reading ‘Limited response of a spring bloom community inoculated with filamentous cyanobacteria to elevated temperature and pCO2’

Changes in growth performance and biochemical composition of Nannochloropsis oceanica in response to elevated CO2 concentrations

We studied the growth performance and biochemical composition (including
soluble carbohydrates, proteins, lipids, phenols, chlorophyll-a, carotenoid and the C/N-ratio) of Nannochloropsis oceanica under various CO2 concentrations. The cell density of N. oceanic increased with a rise in CO2 concentration and got the high level at a CO2 concentration of 1000ppm or 1500ppm. In addition, except the proteins all tested biochemical composition were significantly affected by CO2 concentration (0.01 <P< 0.05; one factorial ANOVA). However comparing with other biochemical components, the contents of phenols in N. oceanic showed the opposite trends (P<0.01; one factorial ANOVA). In general, the short-term stimulation of elevated CO2 concentration to N. oceanic can promote cell division and synthesis of most of biochemical components (expect proteins and phenols).

Continue reading ‘Changes in growth performance and biochemical composition of Nannochloropsis oceanica in response to elevated CO2 concentrations’

Seawater acidification affects the immune enzyme activities of the Manila clam Ruditapes philippinarum

Ocean acidification leads to changes in physiological and immune responses of bivalves, but the effect on the immune enzyme activities of the Manila clam, Ruditapes philippinarum, when the pH is lower than the normal value has not been studied in detail. In this study, experiments were conducted to determine how pH (7.4, 7.7, 8.0) affects the immune enzyme activities in the gill and hemocytes of the Manila clam. Membrane stability and phagocytosis increased with decrease of pH from 8.0 to 7.7 and then decreased at pH 7.4. The total protein content in the hemocytes and gills decreased with decreasing pH. Lysozyme content in the hemocytes increased with decreasing pH, and the differences were significant among the different pH groups ( P < 0.05). Adenosine triphosphatase activity at pH 7.4 was significantly higher than in the other two groups, but no significant difference was observed between pH 7.7 and 8.0. Catalase activity decreased from pH 8.0 to 7.7 and then increased at pH 7.4, and the differences were significant among the experimental groups ( P < 0.05). These findings provide valuable information about the immune response of R. philippinarum to reduced water pH and insights for future research investigating exposure of bivalves to elevated CO2 conditions.

Continue reading ‘Seawater acidification affects the immune enzyme activities of the Manila clam Ruditapes philippinarum’

Impact de l’acidification et du réchauffement sur les communautés planctoniques de l’estuaire du Saint-Laurent et la production de diméthylsulfure (in French)

Anthropogenic carbon dioxide (CO2) emissions have increased since the industrial revolution, leading to modifications in atmospheric CO2 content and an increase in oceanic CO2 partial pressures (pCO2). The uptake of CO2 by the oceans has resulted in a lowering of surface water pH, corresponding to an increase in the acidity of the oceans by ~30 % compared with pre-industrial times. Furthermore, climate change resulting from the accumulation of anthropogenic CO2 in the atmosphere is responsible for the observed warming of sea surface temperatures since the mid 20th century. The fate of planktonic communities in the face of these changes in the marine environment over the next century remains uncertain. Even less understood are the possible interactions of acidification and warming on the production of dimethylsulfide (DMS), a sulfur-containing gas produced by planktonic communities and involved in climate regulation. The aim of this thesis is to determine the impact of heightened pCO2 on the development of the phytoplanktonic blooms in the Lower St. Lawrence Estuary (LSLE), and their production of DMS, as well as to evaluate how concomitant warming could modulate the effects of acidification. Two intricate experiments were carried out during this study. First, a microcosm experiment (~20 L) was conducted in the summer of 2013 to assess the effects of pCO2 on the development of the LSLE spring diatom bloom, paying special attention to the microbial processes governing the production of DMS. Second, a multifactorial mesocosm experiment (~2600 L) was carried out in the fall of 2014 to investigate the combined effects of pCO2 and temperature on the development of the fall bloom in the LSLE and the production of DMS. Results from our microcosm experiment show that the blooming phytoplankton community of the LSLE during spring is resistant to pCO2 increases superior to the expected values for 2100. This resistance likely reflects its adaptation to the estuarine setting, an environment known for rapid and intense fluctuations of pCO2. This first experiment has also highlighted a reduction of the average concentrations of DMS by 15 and 40 % in planktonic assemblages respectively subjected to pCO2 of ~1850 μatm and ~2700 μatm compared to the control (~775 μatm). Parallel incubations have shown, using 35S-DMSPd, that the negative effect of acidification on DMS mostly stemmed from a decrease in the conversion efficiency of DMSP to DMS by bacteria. The second experiment has also highlighted a strong resistance of the diatom Skeletonema costatum to a wide range of pH (~8.0–7.2), and corresponding pCO2 (~90–3000 μatm). In this study, a warming of 5 °C accelerated the development and decline of the bloom, but did not affect the integrated primary production over the duration of the experiment. As in the first experiment, heightened pCO2 resulted in a decrease of average concentrations of DMS of ~66 % in the most acidified mesocosms compared to the least acidified mesocosms at in situ temperature (10 °C). However, the negative effect of an increase in pCO2 on the net production of DMS could be mitigated by a warming of surface waters. Indeed, my results reveal that the net production of DMS was higher at 15 °C compared to 10 °C over the whole pCO2 gradient in our mesocosm study. These novel results suggest that warming of surface waters could mitigate, at least partly, the negative effect of acidification on DMS net production in the LSLE and perhaps in the world’s oceans.

Continue reading ‘Impact de l’acidification et du réchauffement sur les communautés planctoniques de l’estuaire du Saint-Laurent et la production de diméthylsulfure (in French)’

Ocean acidification buffers the physiological responses of the king ragworm Alitta virens to the common pollutant copper

Highlights

• Whilst ocean acidification (OA) often increases the toxicity of copper to marine invertebrates, here we find the opposite in the ragworm Alitta virens.

• There was no increase in copper-induced DNA damage or lipid peroxidation under OA conditions.

• Instead OA appeared to buffer the effects of copper on lipid peroxidation and acid-base disturbance, reducing these effects relative to ambient seawater conditions.

Abstract

Ocean acidification (OA) has the potential to alter the bioavailability of pH sensitive metals contaminating coastal sediments, particularly copper, by changing their speciation in seawater. Hence OA may drive increased toxicity of these metals to coastal biota. Here, we demonstrate complex interactions between OA and copper on the physiology and toxicity responses of the sediment dwelling polychaete Alitta virens. Worm coelomic fluid pCO2 was not increased by exposure to OA conditions (pHNBS 7.77, pCO2 530 μatm) for 14 days, suggesting either physiological or behavioural responses to control coelomic fluid pCO2. Exposure to 0.25 µM nominal copper caused a decrease in coelomic fluid pCO2 by 43.3% and bicarbonate ions by 44.6% but paradoxically this copper-induced effect was reduced under near-future OA conditions. Hence OA appeared to ‘buffer’ the copper-induced acid-base disturbance. DNA damage was significantly increased in worms exposed to copper under ambient pCO2 conditions, rising by 11.1% compared to the worms in the no copper control, but there was no effect of OA conditions on the level of DNA damage induced by copper when exposed in combination. These interactions differ from the increased copper toxicity under OA conditions reported for several other invertebrate species. Hence this new evidence adds to the developing paradigm that species’ physiology is key in determining the interactions of these two stressors rather than it purely being driven by the changes in metal chemistry under lower seawater pH.

Continue reading ‘Ocean acidification buffers the physiological responses of the king ragworm Alitta virens to the common pollutant copper’

Ocean acidification may alter predator-prey relationships and weaken nonlethal interactions between gastropods and crabs

Predator-prey interactions often drive ecological patterns and are governed by factors including predator feeding rates, prey behavioral avoidance, and prey structural defenses. Invasive species can also play a large ecological role by disrupting food webs, driving local extinctions, and influencing evolutionary changes in prey defense mechanisms. This study documents a substantial reduction in the behavioral and morphological responses of multiple gastropod species (Nucella lapillus, N. ostrina, Urosalpinx cinerea) to an invasive predatory crab (green crab Carcinus maenas) under ocean acidification conditions. These results suggest that climate-related changes in ocean chemistry may diminish non-lethal effects of predators on prey responses including behavioral avoidance. While snails with varying shell mineralogies were similarly successful at deterring predation, those with primarily aragonitic shells were more susceptible to dissolution and erosion under high CO2 conditions. The varying susceptibility to predation among species with similar ecological roles could indicate that the impacts of invasive species like green crabs could be modulated by the ability of native and invasive prey to withstand ocean acidification conditions.

Continue reading ‘Ocean acidification may alter predator-prey relationships and weaken nonlethal interactions between gastropods and crabs’

Larval development, juvenile survival, and burrowing rate of geoduck clams (Panopea japonica) under different pH conditions

Changes in seawater pH in the culture environment have numerous effects on marine bivalves. To investigate the effect of pH on larval development, juvenile survival, and burrowing rate of geoduck clams (Panopea japonica), specimens were cultured under different experimental pH conditions (6.8, 7.2, 7.6, 8.0, 8.4, and 9.2). The pH range for optimal growth and development differed among different larval stages. However, significant changes in larval development (p < 0.5) relative to the control (pH 8.0) were detected at very high or low pH. The best hatching rate occurred at pH 7.6–8.8, and it was significantly lower (p < 0.5) at pH 6.8, 7.2, and 9.2. Larval survival was only 4% at pH 6.8. Growth rate of larvae increased with increasing pH and the optimal range was 8.0 to 8.8. This finding suggests that alkaline conditions favor growth and development of larvae and allow them to reach the metamorphic stage promptly. Prolonged metamorphosis was a common feature in larvae in the different experimental pH groups. pH below 7.6 and above 8.8 resulted in a significantly (p < 0.5) lower metamorphosis rate, suggesting that high acidity and alkalinity were deleterious to larval metamorphosis. Thus, the suitable pH range for metamorphosis was 8.0 to 8.8. Lower and higher pH also affected the digging behavior of geoduck clams, and the suitable pH range for burrowing was 7.2 to 8.8. Geoduck clams stopped burrowing in the sand at pH 6.8 and 9.2, possibly due to impairment of biological process caused by acidic and alkaline seawater. These findings provide valuable information about the larval and juvenile responses of P. japonica in variable pH.

Continue reading ‘Larval development, juvenile survival, and burrowing rate of geoduck clams (Panopea japonica) under different pH conditions’


Subscribe to the RSS feed

Powered by FeedBurner

Follow AnneMarin on Twitter

Blog Stats

  • 1,242,876 hits

OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book