Archive for February, 2018

Oxidative stress induced by titanium dioxide nanoparticles increases under seawater acidification in the thick shell mussel Mytilus coruscus

Highlights

• Effects of nano-TiO2  and low pH on the mussel M. coruscus are investigated.
• Synergistic and carry-over effects of nano-TiO2  and low pH were observed.
• Low pH significantly affected the antioxidant indexes of mussels under high-concentration nano-TiO2 .
• The oxidative stress of gills is more evident than that of digestive glands.

Abstract
Biochemical responses of the mussel Mytilus coruscus exposed to different concentrations of titanium dioxide nanoparticles (nano-TiO2 ) (0, 2.5, 10 mg L−1) and two pH levels (pH 8.1 and pH 7.3) for 14 days. Mussel responses were also investigated after a 7 days recovery period (pH 8.1 and no nanoparticle). Exposure to nano-TiO2 led changes in antioxidant indexes (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH)), biotransformation enzyme activity (GST) and malondialdehyde level (MDA) in gills and digestive glands. An increase in MDA level and a decrease in SOD and GSH activities were observed in gill of mussels exposed to 10 mg L−1 nano-TiO2 . This effect was more severe in mussels kept at pH 7.3 as compared to pH 8.1. A different response was observed in the digestive gland as SOD, CAT and GSH levels increased in mussels exposed to nano-TiO2 . These contrasting results in digestive glands and gills were only evident at high concentration of nano-TiO2  and low pH. A 7 days recovery period was not sufficient to fully restore SOD, GPx, GST, GSH and MDA levels to levels before exposure to nano-TiO2  and low pH. Overall, our results confirmed that seawater acidification modulates effects of nanoparticles in mussels, and that gills are more sensitive to these stressors as compared with digestive glands.

Continue reading ‘Oxidative stress induced by titanium dioxide nanoparticles increases under seawater acidification in the thick shell mussel Mytilus coruscus’

Ocean acidification in the Middle East and North African region

After examining the current state of knowledge about ocean acidification in Middle East and North African (MENA) countries, we model the socio-economic impacts of disasters, ocean acidification and ecological risk. We use Extreme Value Theory and Peak Over Threshold concept to define the critical threshold point for ocean pH value as an Ornstein-Uhlenbeck process, initially with Gaussian noise. We define the benchmark pH based on time series observations which exhibit moderate to large variations and use Monte Carlo simulations and also model non-Gaussian cases to examine the probability of disasters.

Continue reading ‘Ocean acidification in the Middle East and North African region’

Gene expression correlated with delay in shell formation in larval Pacific oysters (Crassostrea gigas) exposed to experimental ocean acidification provides insights into shell formation mechanisms

Background

Despite recent work to characterize gene expression changes associated with larval development in oysters, the mechanism by which the larval shell is first formed is still largely unknown. In Crassostrea gigas, this shell forms within the first 24 h post fertilization, and it has been demonstrated that changes in water chemistry can cause delays in shell formation, shell deformations and higher mortality rates. In this study, we use the delay in shell formation associated with exposure to CO2-acidified seawater to identify genes correlated with initial shell deposition.

Results

By fitting linear models to gene expression data in ambient and low aragonite saturation treatments, we are able to isolate 37 annotated genes correlated with initial larval shell formation, which can be categorized into 1) ion transporters, 2) shell matrix proteins and 3) protease inhibitors. Clustering of the gene expression data into co-expression networks further supports the result of the linear models, and also implies an important role of dynein motor proteins as transporters of cellular components during the initial shell formation process.

Conclusions

Using an RNA-Seq approach with high temporal resolution allows us to identify a conceptual model for how oyster larval calcification is initiated. This work provides a foundation for further studies on how genetic variation in these identified genes could affect fitness of oyster populations subjected to future environmental changes, such as ocean acidification.

Continue reading ‘Gene expression correlated with delay in shell formation in larval Pacific oysters (Crassostrea gigas) exposed to experimental ocean acidification provides insights into shell formation mechanisms’

Ocean acidification projected to weaken coral skeletons

A thriving coral reef community at Hotsarihie, Republic of Palau.

A thriving coral reef community at Hotsarihie, Republic of Palau.
Hannah Barkley / Woods Hole Oceanographic Institution

Scientists at the Woods Hole Oceanographic Institution have released a study that found ocean acidification could weaken coral skeletons by up to 20 percent by the end of the century. Continue reading ‘Ocean acidification projected to weaken coral skeletons’

Workshop on Durafet-based pH sensors highlights importance of collecting reference samples

Ocean pH sensor technology has advanced quickly over the last few years. This is predominately driven by the integration of Honeywell™ Durafet® pH electrodes in oceanographic sensor packages. Durafets sensors contain Ion Sensitive Field Effect Transistor (ISFET) technology, which produces highly precise pH measurements in seawater. Precision is better than 0.005 units pHT and stability of the calibration can be maintained for several months (Martz et al. 2010; Takeshita et al. 2014). These characteristics have made Durafet-based sensors popular among oceanographers and marine biologists alike.

Since 2010, multiple Durafet-based pH sensors have become commercially available. Sensors are currently used in estuarine, coastal, and deep-sea ecosystems, underway measurements, profiling floats, and laboratory-based ocean acidification experiments. Durafet-based sensors require specialized expertise for optimal operation and high-quality data acquisition (McLaughlin et al. 2017). The crux of data quality lies in the intricacies associated with calibration of these sensors. While commercial sensors have a factory calibration, this may not be accurate enough for certain marine applications (Figure 1). Most often, users need to perform a calibration using multiple, independent, seawater samples which are then analyzed for pH in the laboratory and used in data processing (Bresnahan et al. 2014). Using such reference samples for calibration, and following proper maintenance, a single SeaFET™ pH sensor can produce high-quality data for multiple years in a coastal environment (Kapsenberg et al. 2017a). Currently, data quality varies among user groups and is associated with experience level (McLaughlin et al. 2017). For this reason, hands-on training provides a beneficial supplement to recently published best practices (Bresnahan et al. 2014; Kapsenberg et al. 2017b; Rivest et al. 2016).

Continue reading ‘Workshop on Durafet-based pH sensors highlights importance of collecting reference samples’

Reproductive trade-offs in a temperate reef fish under high pCO2 levels

Highlights

•Reproductive activity in two-spotted goby is stimulated under high  pCO2  levels.
•Females under high  pCO2  levels produce more eggs.
•Larvae of parental pairs under high  pCO2  levels hatch smaller.
•Different energy allocation strategies are used by females under .
•High  pCO2  levels.

Abstract

Fishes are currently facing novel types of anthropogenic stressors that have never experienced in their evolutionary history, such as ocean acidification. Under these stressful conditions, energetically costly processes, such as reproduction, may be sacrificed for increased chances of survival. This trade-off does not only affect the organism itself but may result in reduced offspring fitness. In the present study, the effects of exposure to high  pCO2 levels were tested on the reproductive performance of a temperate species, the two-spotted goby, Gobiusculus flavescens. Breeding pairs were kept under control (∼600 μatm, pH∼ 8.05) and high  pCO2  levels (∼2300 μatm, pH∼ 7.60) conditions for a 4-month period. Additionally, oxidative stress and energy metabolism-related biomarkers were measured. Results suggest that reproductive activity is stimulated under high  pCO2  levels. Parental pairs in the simulated ocean acidification conditions exhibited increased reproductive output, with 50% more clutches and 44% more eggs per clutch than pairs under control conditions. However, there was an apparent trade-off between offspring number and size, as larvae of parental pairs under high  pCO2  levels hatched significantly smaller, suggesting differences in parental provisioning, which could be related to the fact that these females produce more eggs. Moreover, results support the hypothesis of different energy allocation strategies used by females under high  pCO2  conditions. These changes might, ultimately, affect individual fitness and population replenishment.

Continue reading ‘Reproductive trade-offs in a temperate reef fish under high pCO2 levels’

Interactive effect of temperature, acidification and ammonium enrichment on the seagrass Cymodocea nodosa

Highlights

•A significant synergy can occur when several environmental factors interact.
•Warming positively affect plant production but at expense of reducing carbon reserves.
•Loss leaf rates increased with ammonium supply
•CO2 increase did not produce significant effects.
•Future scenarios may benefit to C. nodosa improving their growth and carbon reserves.

Abstract

Global (e.g. climate change) and local factors (e.g. nutrient enrichment) act together in nature strongly hammering coastal ecosystems, where seagrasses play a critical ecological role. This experiment explores the combined effects of warming, acidification and ammonium enrichment on the seagrass Cymodocea nodosa under a full factorial mesocosm design. Warming increased plant production but at the expense of reducing carbon reserves. Meanwhile, acidification had not effects on plant production but increased slightly carbon reserves, while a slight stimulation of net production and a slight decrease on carbon reserves under ammonium supply were recorded. When all the factors were combined together improved the production and carbon reserves of Cymodocea nodosa, indicating that acidification improved ammonium assimilation and buffered the enhanced respiration promoted by temperature. Therefore, it could indicate that this temperate species may benefit under the simulated future scenarios, but indirect effects (e.g. herbivory, mechanical stress, etc.) may counteract this balance.

Continue reading ‘Interactive effect of temperature, acidification and ammonium enrichment on the seagrass Cymodocea nodosa’

Monitoring a changing bay

Meltwater gushes from Lamplugh Glacier

Meltwater gushes from beneath Lamplugh Glacier in Glacier Bay National Park and Preserve.
NPS

Is the fresh water pouring from rapidly melting glaciers changing the seawater in Glacier Bay? If so, what will that mean for marine life…and those who depend on it?

Project Dates
Phase I: 2011 to 2014
Phase II: 2015 to 2018

Melting into Glacier Bay

“Glacier Bay waters may be experiencing ocean acidification on steroids.” – Lewis Sharman, Ecologist, Glacier Bay National Park and Preserve

University of AK Fairbanks biological oceanography professor Russ Hopcroft looks down at the cupful of soupy water in his hand with something very near affection. An expert in zooplankton ecology, Russ is part of a research team on board the vessel Fog Lark. The team is studying ocean acidification in the bay’s waters, in partnership with Glacier Bay National Park and Preserve. In his hand is a concentrated sample of filtered bay seawater. The object of his affection – the thick mass of zooplankton casting about in this water. This is the elixir of life in Glacier Bay.

Continue reading ‘Monitoring a changing bay’

Climate change impacts on Florida’s fisheries and aquaculture sectors and options for adaptation

Florida supports diverse marine and freshwater fisheries and a significant aquaculture industry with a combined economic impact of approximately 15 billion US$. We begin by describing the characteristics of the different fisheries and aquaculture sectors. This is followed by a description of the relevant climate change and confounding drivers. We then present an integrated social-ecological systems framework for analyzing climate change impacts and apply this framework to the different fisheries and aquaculture sectors. We highlight how the characteristics of each sector gives rise to distinct expected climate change impacts and potential adaptation measures. We conclude with general considerations for monitoring and adaptation.

Continue reading ‘Climate change impacts on Florida’s fisheries and aquaculture sectors and options for adaptation’

Inter and intraspecific comparisons of the skeletal Mg/Ca ratios of high latitude Antarctic echinoderms

Echinoderms are vulnerable to ocean acidification because of their high magnesium calcite skeletons. Here, skeletal Mg/Ca ratios were examined within and between individuals of 20 Antarctic echinoderms representative of the asteroids, ophiuroids and echinoids. The highest mean Mg/Ca ratios occurred in the discs and arms (0.111 and 0.110, respectively) of brittle-stars and the lowest in the spines (0.010) of cidaroid sea urchins. Many taxa (11 of 14 species) from the collection sites showed no intraspecific differences in Mg/Ca ratios between given skeletal components. Exceptions were the spines of two regular sea urchins and the skeletal ossicles of the combined arms and disc of a brittle-star. The relationship between skeletal magnesium content and latitude was further evaluated and an inverse correlation was found between Antarctic echinoderm taxa skeletal magnesium content and latitude across 62° to 76°, indicating that the relationship occurs over relatively narrow latitudes. Upon examination of an even narrower range (70–76° latitude), a region where the mineralogy of echinoderm skeletons has not been investigated, the predicted inverse relationship between Mg/Ca ratio and latitude was still observed in sea-stars, but not in brittle-stars or sea urchins.

Continue reading ‘Inter and intraspecific comparisons of the skeletal Mg/Ca ratios of high latitude Antarctic echinoderms’


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Ocean acidification in the IPCC AR5 WG II

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