Posts Tagged 'crustaceans'

Impact of ocean acidification on the biogeochemistry and meiofaunal assemblage of carbonate-rich sediments: results from core incubations (Bay of Villefranche, NW Mediterranean Sea)

Highlights

• A sediment incubation experiment to assess the effect of ocean acidification
• Porewater concentration gradients and sediment-water fluxes (DIC, TA, pH, Ca2+, O2)
• Ocean acidification impacts early diagenesis in carbonate-rich sediments.
• CaCO3 dissolution and the TA release may increase the buffering capacity of bottom water.

Abstract

Marine sediments are an important carbonate reservoir whose partial dissolution could buffer seawater pH decreases in the water column as a consequence of anthropogenic CO2 uptake by the ocean. This study investigates the impact of ocean acidification on the carbonate chemistry at the sediment-water interface (SWI) of shallow-water carbonate sediments. Twelve sediment cores were sampled at one station in the Bay of Villefranche (NW Mediterranean Sea). Four sediment cores were immediately analyzed in order to determine the initial distribution (T0) of dissolved inorganic carbon (DIC), total alkalinity (TA), pH and dissolved oxygen (O2) in the porewaters and to quantify sediment-water fluxes. Four other cores were kept submerged in the laboratory for 25 days with ambient seawater (pHT = 8.12) and the remaining four cores were incubated with acidified seawater (average pH offset of −0.68). This acidification experiment was carried out in an open-flow system, in the dark and at in-situ temperature (15 °C). Every three days, sediment-water fluxes (DIC, TA, pH, O2 and nutrients) were determined using a whole core 12-h incubation technique. Additionally, vertical O2 and pH microprofiles were regularly recorded in the first 2 cm of the sediment during the entire experiment. At the end of the experiment, TA, DIC and Ca2+ concentrations were analyzed in the porewaters and the abundance and taxonomic composition of meiofaunal organisms were assessed. The saturation states of the porewaters with respect to calcite and aragonite were over-saturated but under-saturated with respect to 12 mol% Mg-calcite, in both acidified and non-acidified treatments. The sediment-water fluxes of TA and DIC increased in the acidified treatment, likely as a consequence of enhanced carbonate dissolution. In contrast, the acidification of the overlying water did not significantly affect the O2 and nutrients fluxes at the SWI. Meiofaunal abundance decreased in both treatments over the duration of the experiment, but the organisms seemed unaffected by the acidification. Our results demonstrate that carbonate dissolution increased under acidified conditions but other parameters, such as microbial redox processes, were apparently not affected by the pH decrease, at least during the duration of our experiment. The dissolution of sedimentary carbonates and the associated release of TA may potentially buffer bottom water, depending on the intensity of the TA flux, the TA/DIC ratio, vertical mixing and, therefore, the residence time of bottom water. Under certain conditions, this process may mitigate the effect of ocean acidification on benthic ecosystems.

Continue reading ‘Impact of ocean acidification on the biogeochemistry and meiofaunal assemblage of carbonate-rich sediments: results from core incubations (Bay of Villefranche, NW Mediterranean Sea)’

Acidification increases abundances of Vibrionales and Planctomycetia associated to a seaweed-grazer system: potential consequences for disease and prey digestion efficiency

Ocean acidification significantly affects marine organisms in several ways, with complex interactions. Seaweeds might benefit from rising CO2 through increased photosynthesis and carbon acquisition, with subsequent higher growth rates. However, changes in seaweed chemistry due to increased CO2 may change the nutritional quality of tissue for grazers. In addition, organisms live in close association with a diverse microbiota, which can also be influenced by environmental changes, with feedback effects. As gut microbiomes are often linked to diet, changes in seaweed characteristics and associated microbiome can affect the gut microbiome of the grazer, with possible fitness consequences. In this study, we experimentally investigated the effects of acidification on the microbiome of the invasive brown seaweed Sargassum muticum and a native isopod consumer Synisoma nadejda. Both were exposed to ambient CO2 conditions (380 ppm, pH 8.16) and an acidification treatment (1,000 ppm, pH 7.86) for three weeks. Microbiome diversity and composition were determined using high-throughput sequencing of the variable regions V5-7 of 16S rRNA. We anticipated that as a result of acidification, the seaweed-associated bacterial community would change, leading to further changes in the gut microbiome of grazers. However, no significant effects of elevated CO2 on the overall bacterial community structure and composition were revealed in the seaweed. In contrast, significant changes were observed in the bacterial community of the grazer gut. Although the bacterial community of S. muticum as whole did not change, Oceanospirillales and Vibrionales (mainly Pseudoalteromonas) significantly increased their abundance in acidified conditions. The former, which uses organic matter compounds as its main source, may have opportunistically taken advantage of the possible increase of the C/N ratio in the seaweed under acidified conditions. Pseudoalteromonas, commonly associated to diseased seaweeds, suggesting that acidification may facilitate opportunistic/pathogenic bacteria. In the gut of S. nadejda, the bacterial genus Planctomycetia increased abundance under elevated CO2. This shift might be associated to changes in food (S. muticum) quality under acidification. Planctomycetia are slow-acting decomposers of algal polymers that could be providing the isopod with an elevated algal digestion and availability of inorganic compounds to compensate the shifted C/N ratio under acidification in their food.

In conclusion, our results indicate that even after only three weeks of acidified conditions, bacterial communities associated to ungrazed seaweed and to an isopod grazer show specific, differential shifts in associated bacterial community. These have potential consequences for seaweed health (as shown in corals) and isopod food digestion. The observed changes in the gut microbiome of the grazer seem to reflect changes in the seaweed chemistry rather than its microbial composition.

Continue reading ‘Acidification increases abundances of Vibrionales and Planctomycetia associated to a seaweed-grazer system: potential consequences for disease and prey digestion efficiency’

Characterization of a γ‐aminobutyrate type A receptor‐associated protein gene, which is involved in the response of Portunus trituberculatus to CO2‐induced ocean acidification

The γ‐aminobutyrate type A receptor‐associated protein (GABARAP) is a ubiquitin‐like modifier implicated in membrane trafficking and fusion events involving the γ‐aminobutyrate type A receptor, autophagy and apoptosis. In this study, the gene encoding GABARAP was cloned from swimming crab Portunus trituberculatus (PtGABARAP) based on the expression sequence tag (EST). The full‐length cDNA of 664 bp includes a 5′ untranslated region (UTR) of 87 bp, a 3′ UTR of 223 bp with a poly(A) tail, and an open reading frame (ORF) of 354 bp encoding a polypeptide of 117 amino acids with a predicted molecular weight of 13.96 kDa. The deduced amino acid sequence shares high similarity (93%–100%) with GABARAPs from other species and includes a conserved Atg8 domain. In a phylogenetic analysis PtGABARAP clustered with GABARAPs from other species, and more widely with other GABARAP family proteins. The impact of elevated ocean acidification (OA) on P. trituberculatus behaviours was investigated, and real‐time RT‐PCR revealed that PtGABARAP expression was up‐regulated after OA exposure. Ocean acidification also caused crabs anxiety‐like behaviours, like the shoal average speed increase, preference for dark environment (scototaxis) and fast exploration. The results indicated that GABARAP might be involved in the interactions of GABAA receptors and elevated‐CO2 seawater.

Continue reading ‘Characterization of a γ‐aminobutyrate type A receptor‐associated protein gene, which is involved in the response of Portunus trituberculatus to CO2‐induced ocean acidification’

Transgenerational deleterious effects of ocean acidification on the reproductive success of a keystone crustacean (Gammarus locusta)

Highlights

• High CO2 reduced survival and mate-guarding duration.
• Initial stimulation of egg production in F0 was followed by a decline in F1.
• Drop in fecundity revealed in the second generation under high CO2.
• Overall negative carry-over effects of transgenerational exposure to high CO2.

Abstract

Ocean acidification (OA) poses a global threat to marine biodiversity. Notwithstanding, marine organisms may maintain their performance under future OA conditions, either through acclimation or evolutionary adaptation. Surprisingly, the transgenerational effects of high CO2 exposure in crustaceans are still poorly understood. For the first time, the present study investigated the transgenerational effect of OA, from hatching to maturity, of a key amphipod species (Gammarus locusta). Negative transgenerational effects were observed on survival of the acidified lineage, resulting in significant declines (10–15%) compared to the control groups in each generation. Mate-guarding duration was also significantly reduced under high CO2 and this effect was not alleviated by transgenerational acclimation, indicating that precopulatory behaviours can be disturbed under a future high CO2 scenario. Although OA may initially stimulate female investment, transgenerational exposure led to a general decline in egg number and fecundity. Overall, the present findings suggest a potential fitness reduction of natural populations of G. locusta in a future high CO2 ocean, emphasizing the need of management tools towards species’ sustainability.

Continue reading ‘Transgenerational deleterious effects of ocean acidification on the reproductive success of a keystone crustacean (Gammarus locusta)’

Behavioural responses of Antarctic krill (Euphausia superba) to CO2-induced ocean acidification: would krill really notice?

The Southern Ocean is expected to be significantly affected by future ocean acidification. Antarctic krill (Euphausia superba) is the key species of the Southern Ocean ecosystem. Understanding their behavioural responses to acidification is critical for assessing the impacts of ocean acidification on the ecosystem. Adult Antarctic krill reared in different holding tanks with various CO2 levels for 6 months prior to the experiments were tested for their behavioural responses to different carbon dioxide partial pressures (pCO2) (400, 1000, 1500, 2000, and 4000 μatm pCO2) in a two-channel flume. The time krill occupied either of the flume channels (with high or ambient CO2 levels) was highly variable in all tests. In most cases no significant preference to either side of the flume was found. The krill did not display any systematic discrimination to the sea water with different CO2 levels regardless of the CO2 levels that krill were acclimated for in the 6 months prior to the experiment. Poor ability to discriminate high CO2 waters may have an important implication to their life history in the future as ocean acidification rapidly progresses in parts of Southern Ocean.

Continue reading ‘Behavioural responses of Antarctic krill (Euphausia superba) to CO2-induced ocean acidification: would krill really notice?’

Acute toxicity of carbon dioxide to juvenile marine shrimp Litopenaeus vannamei (Boone 1931)

Elevated concentrations of dissolved carbon dioxide (CO2) and reduced pH levels are observed during the culture and transportation of aquatic organisms. Studies on the toxicity effects of CO2 in penaeid shrimp are scarce when compared to the amount of research in fish. The objective of the present study was to determine the lethal concentration and safety levels of CO2 for juvenile white shrimp Litopenaeus vannamei. Juveniles (1.76 ± 0.36 g) were exposed for 96 h to one of six concentrations of dissolved CO2 (14.5, 23.8, 59.0, 88.0, 115.0, and 175.0 mg/L) or a control condition (without the addition of CO2), and their survival was monitored for 96 h. The LC50 values with 95% confidence limits at 24, 48, 72, and 96 h were 130.05 (104.2–162.1), 77.2 (73.8–80.02), 69.65 (65.47–74.32), and 59.12 (53.08–66.07) mg/L of CO2, respectively. The calculated safety level was 5.9 mg/L of CO2, and the highest concentration that did not induce significantly higher mortality than that observed in controls (NOEC) was 23.8 mg/L of CO2. We recommend that CO2 levels should be kept below the safety level obtained in this study.

Continue reading ‘Acute toxicity of carbon dioxide to juvenile marine shrimp Litopenaeus vannamei (Boone 1931)’

Increasing use of human-dominated habitats as CO2 emissions warm and acidify oceans

Urban and artificial structures are increasingly added to the world’s coasts during a time in which changing climate is forecast to drive shifts in naturally occurring habitats. We ask whether the role of artificial structures as marine habitats will increase in importance relative to their natural counterparts, particularly as natural habitats are negatively affected by ocean warming and acidification. To evaluate this model, we contrasted use of natural (kelp forest and turfing algae) and artificial habitat (plastic pier-piling) by a nest-building amphipod (Cymadusa pemptos) under current and future climate conditions of CO2 and temperature. Under future conditions, amphipod populations in mesocosms increased, but this did not lead to greater proportional colonization of kelp and turf. Instead, colonization doubled in artificial habitats, and there was increasing production and occupation of nests on artificial habitats relative to natural habitats. In an age when human modification of natural substrata is increasingly cited as an agent of wildlife decline, understanding the future role of artificial habitats as replacement dwellings for natural habitats is critical. We pioneer an understanding of the future role of natural and artificial habitats, identifying the possibility that the role of urban structures as marine habitats may only increase.

Continue reading ‘Increasing use of human-dominated habitats as CO2 emissions warm and acidify oceans’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book