Posts Tagged 'mollusks'

The potential impact of underwater exhausted CO2 from innovative ships on invertebrate communities

Liquefied natural gas (LNG) powered ships equipped with an underwater exhaust system to reduce the ship’s water resistance could form a future generation of energy-efficient ships. The potential consequences of the underwater exhaust gas to the local ecosystems are still unknown. Especially, the CO2 levels may locally exceed estimated future global levels. The present study exposes marine communities to a wide range of CO2 dosages, resulting in pH 8.6–5.8 that was remained for 49 days. We found that the zooplankton and benthic community were adversely affected by high CO2 exposure levels. In detail, (1) between pH 6.6 and 7.1 polychaete worms became the dominating group of the benthic community and their larvae dominated the zooplankton group. (2) Due to the reduced grazing pressure and the flux of nutrients from decaying organic material planktonic microalgae (phytoplankton) stared blooming at the highest exposure level. The periphyton (fouling microalgae) community was not able to take advantage under these conditions. (3) Marine snails’ (periwinkle) shell damage and high mortality were observed at pH < 6.6. However, the growth of the surviving periwinkles was not directly related to pH, but was positively correlated with the availability of periphyton and negatively correlated with the polychaete worm density that most likely also used the periphyton as food source. Our result indicates that the impact of underwater exhaust gasses depends on various factors including local biological and abiotic conditions, which will be included in future research.

Continue reading ‘The potential impact of underwater exhausted CO2 from innovative ships on invertebrate communities’

Biomonitoring acidification using marine gastropods

Highlights

• Data loggers offer limited coverage of acidification in marine ecosystems.

• Intertidal water pH was reflected in organismal attributes of gastropods.

• Shell surface erosion presents a clear estimate of corrosive water exposure.

• Gastropod biomonitoring can identify coastal areas of more or lesser acidification.

Abstract

Ocean acidification is mainly being monitored using data loggers which currently offer limited coverage of marine ecosystems. Here, we trial the use of gastropod shells to monitor acidification on rocky shores. Animals living in areas with highly variable pH (8.6–5.9) were compared with those from sites with more stable pH (8.6–7.9). Differences in site pH were reflected in size, shape and erosion patterns in Nerita chamaeleon and Planaxis sulcatus. Shells from acidified sites were shorter, more globular and more eroded, with both of these species proving to be good biomonitors. After an assessment of baseline weathering, shell erosion can be used to indicate the level of exposure of organisms to corrosive water, providing a tool for biomonitoring acidification in heterogeneous intertidal systems. A shell erosion ranking system was found to clearly discriminate between acidified and reference sites. Being spatially-extensive, this approach can identify coastal areas of greater or lesser acidification. Cost-effective and simple shell erosion ranking is amenable to citizen science projects and could serve as an early-warning-signal for natural or anthropogenic acidification of coastal waters.

Continue reading ‘Biomonitoring acidification using marine gastropods’

Climate change and bivalve mass mortality in temperate regions

One of the fastest-growing global food sectors is the bivalve aquaculture industry. Bivalves particularly oysters, mussels and clams are important sources of animal protein (Tan and Ransangan 2016a, b). Bivalve aquaculture represents 14–16% of the average per capita animal protein for 1.5 billion people and supports over 200,000 livelihoods, mostly in developing countries (FAO 2018). Most of the bivalves produced around the world (89%) are from aquaculture (FAO 2016). To date, mollusc aquaculture have accounted for 21.42% (17.14 million tonnes) of the total aquaculture production, with Asia being the largest contributor (92.27%) (FAO 2018).

Continue reading ‘Climate change and bivalve mass mortality in temperate regions’

Cryptic genetic variation underpins rapid adaptation to ocean acidification

Global climate change has intensified the need to assess the capacity for natural populations to adapt to abrupt shifts in the environment. Reductions in seawater pH constitute a conspicuous stressor associated with increasing atmospheric carbon dioxide that is affecting ecosystems throughout the world’s oceans. Here, we quantify the phenotypic and genetic modifications associated with rapid adaptation to reduced seawater pH in the marine mussel, Mytilus galloprovincialis. We reared a genetically diverse larval population in ambient and extreme low pH conditions (pHT 8.1 and 7.4) and tracked changes in the larval size and allele frequency distributions through settlement. Additionally, we separated larvae by size to link a fitness-related trait to its underlying genetic background in each treatment. Both phenotypic and genetic data show that M. galloprovincialis can evolve in response to a decrease in seawater pH. This process is polygenic and characterized by genotype-environment interactions, suggesting the role of cryptic genetic variation in adaptation to future climate change. Holistically, this work provides insight into the processes underpinning rapid evolution, and demonstrates the importance of maintaining standing variation within natural populations to bolster species’ adaptive capacity as global change progresses.

Continue reading ‘Cryptic genetic variation underpins rapid adaptation to ocean acidification’

Effect of pH on the bacterial community present in larvae and spat of Crassostrea gigas

Changes in marine environments, including pH changes, have been correlated to alterations in the physiology and disease susceptibility of cultured organisms at the early stages of development. In this study, high-throughput sequencing of the V3-V4 region of the 16S rRNA gene was performed to evaluate the bacterial
biodiversity of Crassostrea gigas pediveliger larvae and spat under acidic stress compared to that of larvae at normal pH value. The evaluation was performed in an experimental system with continuous water flow and pH
manipulation by CO2 bubbling to simulate acidification (pH 7.38 ± 0.039), using the current ocean pH conditions (pH 8.116 ± 0.023) as a reference. The results indicated that the bacterial communities associated with both pediveliger larvae and spat were modified in response to acidic conditions. The families Rhodobacteraceae and Campylobacteraceae were the most affected by the change in pH, with increases in Vibrionaceae in pediveliger larvae and Planctomycetaceae and Phyllobacteriaceae in spat detected. The results of this study demonstrate that the bacterial communities associated with C. gigas pediveliger larvae and spat are responsive to changes in ocean acidification

Continue reading ‘Effect of pH on the bacterial community present in larvae and spat of Crassostrea gigas’

How calorie-rich food could help marine calcifiers in a CO2-rich future

Increasing carbon emissions not only enrich oceans with CO2 but also make them more acidic. This acidifying process has caused considerable concern because laboratory studies show that ocean acidification impairs calcification (or shell building) and survival of calcifiers by the end of this century. Whether this impairment in shell building also occurs in natural communities remains largely unexplored, but requires re-examination because of the recent counterintuitive finding that populations of calcifiers can be boosted by CO2 enrichment. Using natural CO2 vents, we found that ocean acidification resulted in the production of thicker, more crystalline and more mechanically resilient shells of a herbivorous gastropod, which was associated with the consumption of energy-enriched food (i.e. algae). This discovery suggests that boosted energy transfer may not only compensate for the energetic burden of ocean acidification but also enable calcifiers to build energetically costly shells that are robust to acidified conditions. We unlock a possible mechanism underlying the persistence of calcifiers in acidifying oceans.

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Comparison of larval development in domesticated and naturalized stocks of the Pacific oyster Crassostrea gigas exposed to high pCO2 conditions

Ocean acidification (OA) has had significant negative effects on oyster populations on the west coast of North America over the past decade. Many studies have focused on the physiological challenges experienced by young oyster larvae in high pCO2/low pH seawater with reduced aragonite saturation state (Ωarag), which is characteristic of OA. Relatively few, by contrast, have evaluated these impacts upon fitness traits across multiple larval stages and between discrete oyster populations. In this study, we conducted 2 replicated experiments, in 2015 and 2016, using larvae from naturalized ‘wild’ and selectively bred stocks of the Pacific oyster Crassostrea gigas from the US Pacific Northwest and reared them in ambient (~400 µatm) or high (~1600 µatm) pCO2 seawater from fertilization through final metamorphosis to juvenile ‘spat.’ In each year, high pCO2 seawater inhibited early larval development and affected the timing, but not the magnitude, of mortality during this stage. The effects of acidified seawater on metamorphosis of pediveligers to spat were variable between years, with no effect of seawater pCO2 in the first experiment but a ~42% reduction in spat in the second. Despite this variability, larvae from selectively bred oysters produced, on average, more (+ 55 and 37%) and larger (+ 5 and 23%) spat in ambient and high pCO2 seawater, respectively. These findings highlight the variable and stage-specific sensitivity of larval oysters to acidified seawater and the influence that genetic factors have in determining the larval performance of C. gigas exposed to high pCO2 seawater.

Continue reading ‘Comparison of larval development in domesticated and naturalized stocks of the Pacific oyster Crassostrea gigas exposed to high pCO2 conditions’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

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