Posts Tagged 'arthropoda'

Transgenerational exposure to ocean acidification induces biochemical distress in a keystone amphipod species (Gammarus locusta)

Highlights

  • A transgenerational ocean acidification exposure was performed in Gammarus locusta
  • Biomarkers of cellular damage, protein repair and oxidative stress were quantified
  • Within- and transgenerational oxidative damage occurred under high CO2
  • Oxidative stress in F0-proteome may impair offspring’ DNA efficiency repair system
  • Increased vulnerability of wild G. locusta populations under ocean acidification

Abstract

Atmospheric carbon dioxide (CO2) levels are increasing at the fastest rate ever recorded, causing higher CO2 dissolution in the ocean, leading to a process known as ocean acidification (OA). Unless anthropogenic CO2 emissions are reduced, they are expected to reach ~900 ppm by the century’s end, resulting in a 0.13-0.42 drop in the seawater pH levels. Since the transgenerational effects of high CO2 in marine organisms are still poorly understood at lower levels of biological organization (namely at the biochemical level), here we reared a key ecological relevant marine amphipod, Gammarus locusta, under control and high CO2 conditions for two generations. We measured several stress-related biochemical endpoints: i) oxidative damage [lipid peroxidation (LPO) and DNA damage]; ii) protein repair and removal mechanisms [heat shock proteins (HSPs) and ubiquitin (Ub)]; as well as iii) antioxidant responses [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione s-transferase (GST)] and total antioxidant capacity (TAC). The present results support the premise that exposure to high CO2 is expected to decrease survival rates in this species and cause within- and transgenerational oxidative damage. More specifically, the predicted upsurge of reactive oxygen and nitrogen species seemed to overwhelm the stimulated amphipod antioxidant machinery, which proved insufficient in circumventing protein damage within the parents. Additionally, negative effects of OA are potentially being inherited by the offspring, since the oxidative stress imposed in the parent’s proteome appears to be restricting DNA repair mechanisms efficiency within the offspring’s. Thus, we argue that a transgenerational exposure of G. locusta could further increase vulnerability to OA and may endanger the fitness and sustainability of natural populations.

Continue reading ‘Transgenerational exposure to ocean acidification induces biochemical distress in a keystone amphipod species (Gammarus locusta)’

The weakest link: sensitivity to climate extremes across life stages of marine invertebrates

Predicting the effects of climate change on Earth’s biota becomes even more challenging when acknowledging that most species have life cycles consisting of multiple stages, each of which may respond differently to extreme environmental conditions. There is currently no clear consensus regarding which stages are most susceptible to increasing environmental stress, or ‘climate extremes’. We used a meta‐analytic approach to quantify variation in responses to environmental stress across multiple life stages of marine invertebrates. We identified 287 experiments in 29 papers which examined the lethal thresholds of multiple life stages (embryo, larva, juvenile, and adult) of both holoplanktonic and meroplanktonic marine invertebrates subjected to the same experimental conditions of warming, acidification, and hypoxia stress. Most studies considered short acute exposure to stressors. We calculated effect sizes (log response ratio) for each life stage (unpaired analysis) and the difference in effect sizes between stages of each species (paired analysis) included in each experiment. In the unpaired analysis, all significant responses were negative, indicating that warming, acidification and hypoxia tended to increase mortality. Furthermore, embryos, larvae, and juveniles were more negatively affected by warming than adults. The paired analysis revealed that, when subjected to the same experimental conditions, younger life stages were more negatively affected by warming than older life stages, specifically among pairings of adults vs. juveniles and larvae vs. embryos. Although responses to warming are well documented, few studies of the effects of acidification and hypoxia met the criteria for inclusion in our analyses. Our results suggest that while most life stages will be negatively affected by climate change, younger stages of marine invertebrates are more sensitive to extreme heating events.

Continue reading ‘The weakest link: sensitivity to climate extremes across life stages of marine invertebrates’

Combined, short-term exposure to reduced seawater pH and elevated temperature induces community shifts in an intertidal meiobenthic assemblage

In future global change scenarios the surface ocean will experience continuous acidification and rising temperatures. While effects of both stressors on marine, benthic communities are fairly well studied, consequences of the interaction of both factors remain largely unknown. We performed a short-term microcosm experiment exposing a soft-bottom community from an intertidal flat in the Westerscheldt estuary to two levels of seawater pH (ambient pHT = 7.9, reduced pHT = 7.5) and temperature (10 °C ambient and 13 °C elevated temperature) in a crossed design. After 8 weeks, meiobenthic community structure and nematode staining ratios, as a proxy for mortality, were compared between treatments and structural changes were related to the prevailing abiotic conditions in the respective treatments (pore water pHT, sediment grain size, total organic matter content, total organic carbon and nitrogen content, phytopigment concentrations and carbonate concentration). Pore water pHT profiles were significantly altered by pH and temperature manipulations and the combination of elevated temperature and reduced pH intensified the already more acidic porewater below the oxic zone. Meiofauna community composition was significantly affected by the combination of reduced pH and elevated temperature resulting in increased densities of predatory Platyhelminthes, reduced densities of Copepoda and Nauplii and complete absence of Gastrotricha compared to the experimental control. Furthermore, nematode staining ratio was elevated when seawater pH was reduced pointing towards reduced degradation rates of dead nematode bodies. The observed synergistic interactions of pH and temperature on meiobenthic communities and abiotic sediment characteristics underline the importance of multistressor experiments when addressing impacts of global change on the marine environment.

Continue reading ‘Combined, short-term exposure to reduced seawater pH and elevated temperature induces community shifts in an intertidal meiobenthic assemblage’

Influence of elevated temperature, pCO2, and nutrients on larva-biofilm interaction: Elucidation with acorn barnacle, Balanus amphitrite Darwin (Cirripedia: Thoracica)

Highlights

  • Biofilm- and diet-mediated effects of acidification and warming on barnacle larval settlement.
  • Acidification had no direct effect but had cascading effect on settlement via biofilm-mediated changes.
  • Warming either alone or in combination with acidification had direct negative effect on settlement.
  • The negative effect of warming on settlement was compensated by biofilm-mediated changes.
  • Diet grown under acidified and warmer condition yielded higher larval settlement.


Abstract

Selection of optimal habitat by larvae of sessile organism is influenced by cues offered by the biofilm. Ocean warming and acidification are likely to enforce changes in the biofilm community and inturn influence the settlement process. Hence, we evaluated the influence of biofilm (multispecies and unialgal) and diet-mediated changes on the settlement of Balanus amphitrite cyprids (presettlement non-feeding larval stage) under different combinations of temperature (28, 30, 32 and 34 °C), pCO2 (400, 750 and 1500 μatm) and nutrient (unenriched and f/2 enriched). Nutrient enrichment enhanced the diatom and bacterial abundance at ambient temperature (30 °C) and pCO2 (400 μatm), which inturn increased larval settlement. Elevated pCO2 (750 and 1500 μatm) had no direct effect but a variable cascading effect on the settlement via biofilm-mediated changes was observed, depending on the type of biofilm. In contrast, elevated temperature (32 and 34 °C), either individually or in combination with elevated pCO2 had direct negative effect on settlement. However, biofilm-mediated changes compensated this negative effect. The larval settlement was also influenced by changes in the larval diet. Under elevated temperature and pCO2, cyprids raised with a feed (Chaetoceros calcitrans) from ambient temperature and pCO2 were of poor quality (lower RNA:DNA ratio, lower protein synthetic capacity) and yielded lower settlement. However, cyprids raised with a feed from elevated temperature and pCO2 were of better quality (higher RNA:DNA ratio, higher protein synthetic capacity) and yielded higher settlement. Overall, the observations from the present study provide insights into the significance of biotic interactions on the coastal biofouling communities under future climatic scenario and emphasise the need for future experiments on these aspects.

Continue reading ‘Influence of elevated temperature, pCO2, and nutrients on larva-biofilm interaction: Elucidation with acorn barnacle, Balanus amphitrite Darwin (Cirripedia: Thoracica)’

Predicted levels of future ocean acidification and temperature rise could alter community structure and biodiversity in marine benthic communities

A mesocosm experiment was conducted to quantify the effects of reduced pH and elevated temperature on an intact marine invertebrate community. Standardised faunal communities, collected from the extreme low intertidal zone using artificial substrate units, were exposed to one of eight nominal treatments (four pH levels: 8.0, 7.7, 7.3 and 6.7, crossed with two temperature levels: 12 and 16°C). After 60 days exposure communities showed significant changes in structure and lower diversity in response to reduced pH. The response to temperature was more complex. At higher pH levels (8.0 and 7.7) elevated temperature treatments contained higher species abundances and diversity than the lower temperature treatments. In contrast, at lower pH levels (7.3 and 6.7), elevated temperature treatments had lower species abundances and diversity than lower temperature treatments. The species losses responsible for these changes in community structure and diversity were not randomly distributed across the different phyla examined. Molluscs showed the greatest reduction in abundance and diversity in response to low pH and elevated temperature, whilst annelid abundance and diversity was mostly unaffected by low pH and was higher at the elevated temperature. The arthropod response was between these two extremes with moderately reduced abundance and diversity at low pH and elevated temperature. Nematode abundance increased in response to low pH and elevated temperature, probably due to the reduction of ecological constraints, such as predation and competition, caused by a decrease in macrofaunal abundance. This community-based mesocosm study supports previous suggestions, based on observations of direct physiological impacts, that ocean acidification induced changes in marine biodiversity will be driven by differential vulnerability within and between different taxonomical groups. This study also illustrates the importance of considering indirect effects that occur within multispecies assemblages when attempting to predict the consequences of ocean acidification and global warming on marine communities.
Continue reading ‘Predicted levels of future ocean acidification and temperature rise could alter community structure and biodiversity in marine benthic communities’


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Ocean acidification in the IPCC AR5 WG II

OUP book