Does exposure to reduced pH and diclofenac induce oxidative stress in marine bivalves? A comparative study with the mussel Mytilus galloprovincialis and the clam Ruditapes philippinarum

• Combined effects of seawater acidification and diclofenac are assessed in bivalves.
• Biochemical parameters were more influenced by reduced pH than by diclofenac.
• Lowered pH induced oxidative stress in M. galloprovincialis and R. philippinarum.
• Lowered pH reduced COX activity in of R. philippinarum.
R. philippinarum is more vulnerable to acidification than M. galloprovincialis.

CO2-driven acidification and emerging contaminants, such as pharmaceuticals, pose new threats for the maintenance of natural populations of marine organisms by interfering with their normal biochemical pathways and defences. The combined effects of seawater acidification, as predicted in climate change scenarios, and an emerging contaminant (the non-steroidal anti-inflammatory drug, NSAID, diclofenac) on oxidative stress-related parameters were investigated in the Mediterranean mussel Mytilus galloprovincialis and the Manila clam Ruditapes philippinarum. A flow-through system was used to carry out a three-week exposure experiment with the bivalves. First, the animals were exposed to only three pH values for 7 days. The pH was manipulated by dissolving CO2 in the seawater to obtain two reduced pH treatments (pH −0.4 units and pH −0.7 units), which were compared with seawater at the natural pH level (8.1). Thereafter, the bivalves were concomitantly exposed to the three experimental pH values and environmentally relevant concentrations of diclofenac (0.00, 0.05 and 0.50 μg/L) for an additional 14 days. The activities of superoxide dismutase, catalase and cyclooxygenase, and lipid peroxidation and DNA strand-break formation were measured in both the gills and digestive gland after 7, 14 and 21 days of exposure to each experimental condition. The results show that the biochemical parameters measured in both the mussels and clams were more influenced by the reduced pH than by the contaminant or the pH*contaminant interaction, although the biomarker variation patterns differed depending on the species and tissues analysed. Generally, due to increases in its antioxidant defence, M. galloprovincialis was more resistant than R. philippinarum to both diclofenac exposure and reduced pH. Conversely, reduced pH induced a significant decrease in COX activity in both the gills and digestive gland of clams, possibly resulting in the increased DNA damage observed in the digestive gland tissue.

Continue reading ‘Does exposure to reduced pH and diclofenac induce oxidative stress in marine bivalves? A comparative study with the mussel Mytilus galloprovincialis and the clam Ruditapes philippinarum’

Seawater acidification aggravated cadmium toxicity in the oyster Crassostrea gigas: Metal bioaccumulation, subcellular distribution and multiple physiological responses

• Ocean acidification aggravated the toxicity of environmental relevant concentration of Cd on C. gigas.
• OA exacerbated the oxidative stresses, histopathological damage, and apoptosis of Cd-exposed oysters.
• Apoptosis-pathway was generally stimulated in Cd-OA exposed oysters.
• Increased toxicity perhaps associated with the increased accumulation and altered subcellular distribution of Cd.

Mounting evidence has demonstrated the combined effects of ocean acidification (OA) and other environmental stressors on marine organisms. Although metal pollution is widely distributed in coasts and estuaries, the combined effects of OA and metal pollution have received little attention until recent years. In this study, the accumulation and subcellular distribution of cadmium (Cd) and the physiological responses of the oyster Crassostrea gigas were investigated after 31 days of exposure to OA and Cd, either alone or in combination. Increased Cd accumulation was found both in gills (about 57% increase at pH 7.8, 22% increase at pH 7.6) and digestive glands (about 38% increase at pH 7.8, 22% increase at pH 7.6) of C. gigas under elevated pCO2 exposure. Although a similar total Cd accumulation pattern was seen in oyster gills and digestive glands, a higher partition of Cd in the BIM (biologically inactive metal) fractions of gills (about 60%) was found in Cd-exposed treatments compared to the digestive glands (about 45%), which might correspond to the generally lower toxicity in gills. Moreover, synergetic effects of Cd and OA on the oxidative stresses, histopathological damage, and apoptosis of exposed oysters were observed in this study, which might be explained by significant interactions of these two factors on increased generation of ROS. These findings demonstrated that OA could aggravate the toxicity of metals in marine organisms, with significant implications for coastal benthic ecosystems regarding the widespread metal contamination and the concurrent increase of acidified seawater.

Continue reading ‘Seawater acidification aggravated cadmium toxicity in the oyster Crassostrea gigas: Metal bioaccumulation, subcellular distribution and multiple physiological responses’

First data revealed from state ferry Columbia tests on ocean acidity from Southeast AK to WA (audio)

The state ferry Columbia now has six months of data since last October when it began testing the waters for acidity from Southeast Alaska across the entire Province of British Columbia to Bellingham, Washington.

It is part of an unprecedented Alaska/Canada project to learn how increasing ocean acidity affects regional fisheries.

“The fantastic thing about this vessel is it’s going from Bellingham to Skagway and back every week. That’s a 1,600-kilometer run. Nowhere in the world is there a ferry system that’s outfitted with CO2 sensors that’s running that scale of a transit. This is really exciting.”

Wiley Evans is with the Canadian Hakai Institute and the technical lead in the program.

His team rigged the 418-foot ferry to suck up water samples while it is under way.

The samples are measured automatically for oxygen, temperature, salinity and carbon dioxide. The CO2 levels indicate the acidity of the water.

Continue reading ‘First data revealed from state ferry Columbia tests on ocean acidity from Southeast AK to WA (audio)’

Synergistic effects of nano-ZnO and low pH of sea water on the physiological energetics of the thick shell mussel Mytilus coruscus

In order to investigate the ecotoxicological effects of nano-ZnO particles and seawater acidification on marine bivalves, the thick shell mussels, Mytilus coruscus were subjected to joint treatments with different nano-ZnO concentrations (0 [control], 2.5 and 10 mg L-1 [high]) under two pH levels (7.7 [low]and 8.1 [control]) for 14 days. The results showed that respiration rate (RR), absorption efficiency (AE), clearance rate (CR), O:N ratio and scope for growth (SFG) were significantly reduced with nano-ZnO concentration increase, but ammonium excretion rate (ER) was increased. Low pH significantly reduced CR, RR, SFG, and O:N ratio of the mussels especially under high nano-ZnO conditions, and significantly increased ER. Principal component analysis (PCA) showed consistent relationships among most tested parameters, especially among SFG, RR, O:N ratio and CR under the normal pH and 0 nano-ZnO conditions. Therefore, seawater acidification and nano-ZnO interactively impact the ecophysiological responses of mussels and cause more severe effects when they appear concurrently.

Continue reading ‘Synergistic effects of nano-ZnO and low pH of sea water on the physiological energetics of the thick shell mussel Mytilus coruscus’

The ocean is getting more acidic—what that actually means

Picture of an autonomous glider floating two miles off Atlantic City

An autonomous glider floats about two miles off Atlantic City, after being deployed by a team from Rutgers University. Researchers are using the glider to sample ocean pH to help them understand how increasing carbon dioxide in the atmosphere is boosting levels of ocean acidity in the water. 
Photograph by Eric Niiler

Thanks to carbon emissions, the ocean is changing, and that is putting a whole host of marine organisms at risk. These scientists are on the front lines.

Atlantic City, NJ- Grace Saba steadies herself on the back of a gently rocking boat as she and her crew slide a six-foot long yellow torpedo into the sea. A cheer erupts as the device surfaces, turns on its electronic signal, and begins a three-week journey along the New Jersey coast.

“It’s taken seven years to get this done,” said Saba, who has been working on this experiment since 2011. “I’m so happy, I think I might cry!”

Saba is an assistant professor of marine ecology at Rutgers University, where she is studying how fish, clams, and other creatures are reacting to rising levels of ocean acidity. Acidification is a byproduct of climate change; a slow but exorable real-life experiment in which industrial emissions of carbon dioxide into the atmosphere are absorbed and then undergo chemical reactions in the sea. Rising ocean acidity has already bleached Florida’s coral reefs and killed valuable oysters in the Pacific Northwest.

Continue reading ‘The ocean is getting more acidic—what that actually means’

Oxidative stress in the hydrocoral Millepora alcicornis exposed to CO2-driven seawater acidification

Global impacts are affecting negatively coral reefs’ health worldwide. Ocean acidification associated with the increasing CO2 partial pressure in the atmosphere can potentially induce oxidative stress with consequent cellular damage in corals and hydrocorals. In the present study, parameters related to oxidative status were evaluated in the hydrocoral Millepora alcicornis exposed to three different levels of seawater acidification using a mesocosm system. CO2-driven acidification of seawater was performed until reaching 0.3, 0.6 and 0.9 pH units below the current pH of seawater pumped from the coral reef adjacent to the mesocosm. Therefore, treatments corresponded to control (pH 8.1), mild (pH 7.8), intermediate (pH 7.5) and severe (pH 7.2) seawater acidification. After 0, 16 and 30 d of exposure, hydrocorals were collected and the following parameters were analyzed in the holobiont: antioxidant capacity against peroxyl radicals (ACAP), total glutathione (GSHt) concentration, reduced (GSH) and oxidized (GSSG) glutathione ratio (GSH/GSSG), lipid peroxidation (LPO) and protein carbonyl group (PC) levels. ACAP was increased in hydrocorals after 16 d of exposure to intermediate levels of seawater acidification. GSHt and GSH/GSSG did not change over the experimental period. LPO was increased at any level of seawater acidification, while PC content was increased in hydrocorals exposed to intermediate and severe seawater acidification for 30 d. These findings indicate that the antioxidant defense system of M. alcicornis is capable of coping with acidic conditions for a short period of time (16 d). Additionally, they clearly show that a long-term (30 d) exposure to seawater acidification induces oxidative stress with consequent oxidative damage to lipids and proteins, which could compromise hydrocoral health.

Continue reading ‘Oxidative stress in the hydrocoral Millepora alcicornis exposed to CO2-driven seawater acidification’

A three-dimensional niche comparison of Emiliania huxleyi and Gephyrocapsa oceanica: reconciling observations with projections (update)

Coccolithophore responses to changes in carbonate chemistry speciation such as CO2 and H+ are highly modulated by light intensity and temperature. Here, we fit an analytical equation, accounting for simultaneous changes in carbonate chemistry speciation, light and temperature, to published and original data for Emiliania huxleyi, and compare the projections with those for Gephyrocapsa oceanica. Based on our analysis, the two most common bloom-forming species in present-day coccolithophore communities appear to be adapted for a similar fundamental light niche but slightly different ones for temperature and CO2, with E. huxleyi having a tolerance to lower temperatures and higher CO2 levels than G. oceanica. Based on growth rates, a dominance of E. huxleyi over G. oceanica is projected below temperatures of 22 °C at current atmospheric CO2 levels. This is similar to a global surface sediment compilation of E. huxleyi and G. oceanica coccolith abundances suggesting temperature-dependent dominance shifts. For a future Representative Concentration Pathway (RCP) 8.5 climate change scenario (1000 µatm fCO2), we project a CO2 driven niche contraction for G. oceanica to regions of even higher temperatures. However, the greater sensitivity of G. oceanica to increasing CO2 is partially mitigated by increasing temperatures. Finally, we compare satellite-derived particulate inorganic carbon estimates in the surface ocean with a recently proposed metric for potential coccolithophore success on the community level, i.e. the temperature-, light- and carbonate-chemistry-dependent CaCO3 production potential (CCPP). Based on E. huxleyi alone, as there was interestingly a better correlation than when in combination with G. oceanica, and excluding the Antarctic province from the analysis, we found a good correlation between CCPP and satellite-derived particulate inorganic carbon (PIC) with an R2 of 0.73, p < 0.01 and a slope of 1.03 for austral winter/boreal summer and an R2 of 0.85, p < 0.01 and a slope of 0.32 for austral summer/boreal winter.

Continue reading ‘A three-dimensional niche comparison of Emiliania huxleyi and Gephyrocapsa oceanica: reconciling observations with projections (update)’

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Ocean acidification in the IPCC AR5 WG II

OUP book