Posts Tagged 'temperature'

Impact of ocean acidification and warming on the bioenergetics of developing eggs of Atlantic herring Clupea harengus

Atlantic herring (Clupea harengus) is a benthic spawner, therefore its eggs are prone to encounter different water conditions during embryonic development, with bottom waters often depleted of oxygen and enriched in CO2. Some Atlantic herring spawning grounds are predicted to be highly affected by ongoing Ocean Acidification and Warming with water temperature increasing by up to +3°C and CO2 levels reaching ca. 1000 μatm (RCP 8.5). Although many studies investigated the effects of high levels of CO2 on the embryonic development of Atlantic herring, little is known about the combination of temperature and ecologically relevant levels of CO2. In this study, we investigated the effects of Ocean Acidification and Warming on embryonic metabolic and developmental performance such as mitochondrial function, respiration, hatching success (HS) and growth in Atlantic herring from the Oslo Fjord, one of the spawning grounds predicted to be greatly affected by climate change. Fertilized eggs were incubated under combinations of two PCO2 conditions (400 μatm and 1100 μatm) and three temperatures (6, 10 and 14°C), which correspond to current and end-of-the-century conditions. We analysed HS, oxygen consumption (MO2) and mitochondrial function of embryos as well as larval length at hatch. The capacity of the electron transport system (ETS) increased with temperature, reaching a plateau at 14°C, where the contribution of Complex I to the ETS declined in favour of Complex II. This relative shift was coupled with a dramatic increase in MO2 at 14°C. HS was high under ambient spawning conditions (6–10°C), but decreased at 14°C and hatched larvae at this temperature were smaller. Elevated PCO2 increased larval malformations, indicating sub-lethal effects. These results indicate that energetic limitations due to thermally affected mitochondria and higher energy demand for maintenance occur at the expense of embryonic development and growth.

Continue reading ‘Impact of ocean acidification and warming on the bioenergetics of developing eggs of Atlantic herring Clupea harengus’

Acclimatisation and adaptive capacity of echinoderms in response to ocean acidification and warming

Future ocean acidification and warming pose a substantial threat to the viability of some marine populations. In order to persist, marine species will need to acclimate or adapt to the forecasted changes. Recent research into adaptive capacity of marine species has identified mechanisms of non-genetic inheritance including trans-generational plasticity as important sources of resilience.

Based on literature indicating that echinoderms are tolerant to moderate increases in temperature and seawater pCO2, this study hypothesises three outcomes of long-term exposure to combined ocean acidification and warming:

1. Echinoderms possess the genetic capacity to adapt over long time-scales to
predicted levels of combined ocean acidification and warming.
2. Echinoderms possess the physiological capability to acclimatize to ocean
acidification and warming over long time-scales without a significant cost to
metabolic energy budget.
3. After long-term exposure to ocean acidification and warming, echinoderm parents would alter the phenotype (Anticipatory Parental Effect) of their offspring to increase fitness in the F1 generation in response to the environment to which theparents were exposed.

Continue reading ‘Acclimatisation and adaptive capacity of echinoderms in response to ocean acidification and warming’

Temperature driven changes in benthic bacterial diversity influences biogeochemical cycling in coastal sediments

Marine sediments are important sites for global biogeochemical cycling, mediated by macrofauna and microalgae. However, it is the microorganisms that drive these key processes. There is strong evidence that coastal benthic habitats will be affected by changing environmental variables (rising temperature, elevated CO2), and research has generally focused on the impact on macrofaunal biodiversity and ecosystem services. Despite their importance, there is less understanding of how microbial community assemblages will respond to environmental changes. In this study, a manipulative mesocosm experiment was employed, using next-generation sequencing to assess changes in microbial communities under future environmental change scenarios. Illumina sequencing generated over 11 million 16S rRNA gene sequences (using a primer set biased toward bacteria) and revealed Bacteroidetes and Proteobacteria dominated the total bacterial community of sediment samples. In this study, the sequencing coverage and depth revealed clear changes in species abundance within some phyla. Bacterial community composition was correlated with simulated environmental conditions, and species level community composition was significantly influenced by the mean temperature of the environmental regime (p = 0.002), but not by variation in CO2 or diurnal temperature variation. Species level changes with increasing mean temperature corresponded with changes in NH4 concentration, suggesting there is no functional redundancy in microbial communities for nitrogen cycling. Marine coastal biogeochemical cycling under future environmental conditions is likely to be driven by changes in nutrient availability as a direct result of microbial activity.

Continue reading ‘Temperature driven changes in benthic bacterial diversity influences biogeochemical cycling in coastal sediments’

You better repeat it: complex CO2 × temperature effects in Atlantic Silverside offspring revealed by serial experimentation

Concurrent ocean warming and acidification demand experimental approaches that assess biological sensitivities to combined effects of these potential stressors. Here, we summarize five CO2 × temperature experiments on wild Atlantic silverside, Menidia menidia, offspring that were reared under factorial combinations of CO2 (nominal: 400, 2200, 4000, and 6000 µatm) and temperature (17, 20, 24, and 28 °C) to quantify the temperature-dependence of CO2 effects in early life growth and survival. Across experiments and temperature treatments, we found few significant CO2 effects on response traits. Survival effects were limited to a single experiment, where elevated CO2 exposure reduced embryo survival at 17 and 24 °C. Hatch length displayed CO2 × temperature interactions due largely to reduced hatch size at 24 °C in one experiment but increased length at 28 °C in another. We found no overall influence of CO2 on larval growth or survival to 9, 10, 15 and 13–22 days post-hatch, at 28, 24, 20, and 17 °C, respectively. Importantly, exposure to cooler (17 °C) and warmer (28 °C) than optimal rearing temperatures (24 °C) in this species did not appear to increase CO2 sensitivity. Repeated experimentation documented substantial inter- and intra-experiment variability, highlighting the need for experimental replication to more robustly constrain inherently variable responses. Taken together, these results demonstrate that the early life stages of this ecologically important forage fish appear largely tolerate to even extreme levels of CO2 across a broad thermal regime.

Continue reading ‘You better repeat it: complex CO2 × temperature effects in Atlantic Silverside offspring revealed by serial experimentation’

Rising levels of temperature and CO2 antagonistically affect phytoplankton primary productivity in the South China Sea

Highlights

• Ocean warming and acidification individually increased phytoplankton productivity of western South China Sea.
• The combination of high temperature and high CO2 showed an antagonistic effect on phytoplankton productivity.
• High temperature decreased Chl a concentrations in off-shore waters at ambient CO2.
• High CO2 level increased night respiration in the coastal waters at ambient temperatures.

Abstract

Coastal and offshore waters in the South China Sea are warming and becoming acidified due to rising atmospheric levels of carbon dioxide (CO2), yet the combined effects of these two stressors are poorly known. Here, we carried out shipboard incubations at ambient (398 μatm) and elevated (934 μatm) pCO2 at in situ and in situ+1.8 °C temperatures and we measured primary productivity at two coastal and two offshore stations. Both warming and increased CO2 levels individually increased phytoplankton productivity at all stations, but the combination of high temperature and high CO2 did not, reflecting an antagonistic effect. Warming decreased Chl a concentrations in off-shore waters at ambient CO2, but had no effect in the coastal waters. The high CO2 treatment increased night time respiration in the coastal waters at ambient temperatures. Our findings show that phytoplankton assemblage responses to rising temperature and CO2 levels differ between coastal and offshore waters. While it is difficult to predict how ongoing warming and acidification will influence primary productivity in the South China Sea, our data imply that predicted increases in temperature and pCO2 will not boost surface phytoplankton primary productivity.

Continue reading ‘Rising levels of temperature and CO2 antagonistically affect phytoplankton primary productivity in the South China Sea’

Interactive effects of ocean acidification and ocean warming on Pacific herring (Clupea pallasi) early life stages

The synergy of ocean acidification and ocean warming may lead to negative effects in  marine organism responses that would be absent under single stressors. While adult fish are  effective acid-base regulators, early life stages may be more susceptible to environmental  stressors. Pacific herring are ecologically and economically important forage fish native to the  U.S. Pacific Northwest (PNW), and several herring populations in the PNW have experienced reductions in stock abundance. Studies to date have focused on Atlantic herring, and little is  known about the response of Pacific herring to ocean acidification and warming. Therefore, this  study focused on the combined effects of ocean acidification and warming on Pacific herring early life stages. We incubated Pacific herring embryos under a factorial design of two  temperature (10°C, 16°C) and two pCO2 (600 µatm, 1200 µatm) treatments from fertilization  until hatch (11 to 15 days depending on temperature). Elevated pCO2 was associated with a small increase in embryo mortality. However, elevated temperature was associated with greater  embryo mortality, greater embryo heart rates and yolk areas upon hatch, lower percent normal hatch, and decreased larval lengths. The interaction of elevated temperature and pCO2 was associated greater embryo respiration rates and yolk areas. This study indicates that temperature will likely be the primary global change stressor affecting Pacific herring embryology, and interactive effects with pCO2 may introduce additional challenges.
Continue reading ‘Interactive effects of ocean acidification and ocean warming on Pacific herring (Clupea pallasi) early life stages’

Coral responses to temperature, irradiance and acidification stress: linking physiology to satellite remote sensing

The success of the symbiosis of scleractinian corals with dinoflagellates of the genus Symbiodinium is highly dependent on the availability of sufficient, but not excess, light for photosynthesis. After decades of fundamental research into the effect of light on the coral-dinoflagellate symbiosis, an important practical application is emerging in remote monitoring of bleaching at coral reefs. Coral bleaching that originates with the dysfunction of photosynthesis can be either photoacclimatory, a controlled adjustment in response to environmental change, or it can be associated with photodamage, an uncontrolled response to environmental change. It is the latter that tends to lead to severe bleaching events that decrease the rate of carbon fixation, generate excessive oxygen radicals and may ultimately lead to coral death if unfavourable conditions persist. Current best practice methods for the prediction of coral bleaching use water temperature as detected via satellite, and predict the onset of coral bleaching accurately, but not the percent of corals bleached at a reef or the extent of the ensuing mortality.

Continue reading ‘Coral responses to temperature, irradiance and acidification stress: linking physiology to satellite remote sensing’


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