Posts Tagged 'physiology'

Impact of ocean warming and acidification on symbiosis establishment and gene expression profiles in recruits of reef coral Acropora intermedia

The onset of symbiosis and the early development of most broadcast spawning corals play pivotal roles in recruitment success, yet these critical early stages are threatened by multiple stressors. However, molecular mechanisms governing these critical processes under ocean warming and acidification are still poorly understood. The present study investigated the interactive impact of elevated temperature (∼28.0°C and ∼30.5°C) and partial pressure of carbon dioxide (pCO2) (∼600 and ∼1,200 μatm) on early development and the gene expression patterns in juvenile Acropora intermedia over 33 days. The results showed that coral survival was >89% and was unaffected by high temperature, pCO2, or the combined treatment. Notably, high temperature completely arrested successful symbiosis establishment and the budding process, whereas acidification had a negligible effect. Moreover, there was a positive exponential relationship between symbiosis establishment and budding rates (y = 0.0004e6.43xR = 0.72, P < 0.0001), which indicated the importance of symbiosis in fueling asexual budding. Compared with corals at the control temperature (28°C), those under elevated temperature preferentially harbored Durusdinium spp., despite unsuccessful symbiosis establishment. In addition, compared to the control, 351 and 153 differentially expressed genes were detected in the symbiont and coral host in response to experimental conditions, respectively. In coral host, some genes involved in nutrient transportation and tissue fluorescence were affected by high temperature. In the symbionts, a suite of genes related to cell growth, ribosomal proteins, photosynthesis, and energy production was downregulated under high temperatures, which may have severely hampered successful cell proliferation of the endosymbionts and explains the failure of symbiosis establishment. Therefore, our results suggest that the responses of symbionts to future ocean conditions could play a vital role in shaping successful symbiosis in juvenile coral.

Continue reading ‘Impact of ocean warming and acidification on symbiosis establishment and gene expression profiles in recruits of reef coral Acropora intermedia’

Effects of low pH and low salinity induced by meltwater inflow on the behavior and physical condition of the Antarctic limpet, Nacella concinna

Seawater acidification and freshening in the intertidal zone of Marian Cove, Antarctica, which occurs by the freshwater inflow from snow fields and glaciers, could affect the physiology and behavior of intertidal marine organisms. In this study, we exposed Antarctic limpets, Nacella concinna, to two different pH (8.00 and 7.55) and salinity (34.0 and 27.0 psu) levels and measured their righting ability after being flipped over, mortality, condition factor, and shell dissolution. During the 35-day exposure, there was no significant difference in behavior and mortality between different treatments. However, the condition factor was negatively affected by low salinity. Both low pH and low salinity negatively influenced shell formation by decreasing the aragonite saturation state (Ωarg) and enhancing shell dissolution. Our results suggest that, though limpets can tolerate short-term low pH and salinity conditions, intrusions of meltwater accompanied by the glacial retreat may act as a serious threat to the population of N. concinna.

Continue reading ‘Effects of low pH and low salinity induced by meltwater inflow on the behavior and physical condition of the Antarctic limpet, Nacella concinna’

Extracellular multi-unit recording from the olfactory nerve of teleosts

Recent studies have shown that ocean acidification affects olfactory-driven behavior in fish. This may be due in part to a reduction in olfactory sensitivity in high PCO2/low pH water. To assess the effects of ocean acidification, or olfactory sensitivity in marine fish in general, we propose that extracellular multi-unit recording from the olfactory nerve is the method of choice. Although invasive, it is sensitive, robust, reproducible and independent of external salinity (unlike the electro-olfactogram [EOG], for example). Furthermore, it records a primary sensory input into the CNS, prior to any central processing. We show that this method can show a reduction in olfactory sensitivity that is both temporary and odorant-dependent, using a range of amino acids to construct concentration-response curves and calculate the thresholds of detection.

Continue reading ‘Extracellular multi-unit recording from the olfactory nerve of teleosts’

Early development and metabolic rate of the sea louse Caligus rogercresseyi under different scenarios of temperature and pCO2

Highlights

  • The temperature has a significant effect on the hatching time of C. royercresseyi.

  • Combination of pCO2 and temperature has a significant effect on survival in C. rogercresseyi.

  • The combination of pCO2 and temperature had no impact on the size of nauplius I, nauplius II and copepodid stage.

  • Only the temperature has a significant effect on oxygen consumption rate of C. royercresseyi.

Abstract

Anthropogenic CO2 emissions have led to ocean acidification and a rise in the temperature. The present study evaluates the effects of temperature (10, 15 and 20 °C) and pCO2 (400 and 1200 μatm) on the early development and oxygen consumption rate (OCR) of the sea louse Caligus rogercresseyi. Only temperature has an effect on the hatching and development times of nauplius I. But both factors affected the development time of nauplius II (<temperature = longer development time). Copepodid survival time was also affected by temperature and pCO2, at 10 °C and 400 μatm, survival was 30 and 44% longer than at 15 and 20 °C. OCRs were impacted by temperature but not by pCO2. In all treatments, OCR was lower for nauplius II than for the copepodid. Our results show the need to further evaluate the effects of a combination of environmental drivers on the performance of C. rogercresseyi, in a changing and uncertain future.

Continue reading ‘Early development and metabolic rate of the sea louse Caligus rogercresseyi under different scenarios of temperature and pCO2’

Lack of oxidative damage on temperate juvenile catsharks after a long-term ocean acidification exposure

Ocean acidification is a consequence of chemical changes driven mainly by a continuous uptake of carbon dioxide, resulting in pH decrease. This phenomenon represents an additional threat to marine life, with expected effects ranging from changes in behavioral responses and calcification rates to the potential promotion of oxidative stress. To unravel the impacts of ocean acidification on the antioxidant system of sharks, we performed a long-term exposure (9 months, since early embryogenesis) to high CO2 conditions (pCO2 ~ 900 μatm) on a temperate shark (Scyliorhinus canicula). The following biomarkers were measured: enzymatic antioxidant defense (superoxide dismutase, catalase and glutathione peroxidase), protein repair and removal (heat shock proteins and ubiquitin), and oxidative damage on lipids (malondialdehyde) and DNA (8-hydroxy-2′-deoxyguanosine). Changes in the antioxidant enzyme defense were restricted to an increase in catalase activity in the muscle, an enzyme that plays a major role in oxidative stress mitigation. On the other hand, no evidence of oxidative damage was found, indicating that the observed increase in catalase activity may be enough to neutralize the effects of potentially higher reactive oxygen species. These results further indicate that these sharks’ antioxidant system can successfully cope with the levels of carbon dioxide projected for the end of the century. Nonetheless, the interaction between ocean acidification and the rise in temperature expected to occur in a near future may disturb their antioxidant capacity, requiring further investigation.

Continue reading ‘Lack of oxidative damage on temperate juvenile catsharks after a long-term ocean acidification exposure’

Functionally redundant herbivores: urchin and gastropod grazers respond differently to ocean warming and rising CO2

Future ocean CO2 and temperatures are predicted to increase primary productivity across tropical marine habitats, potentially driving a shift towards algal-dominated systems. However, increased consumption of algae by benthic grazers could potentially counter this shift. Yet, the response of different grazer species to future conditions will be moderated by their physiologies, meaning that they may not be functional equivalents. Here, we experimentally assessed the physiological response of key grazers — the sea urchin Heliocidaris crassispina and 2 gastropod species, Astralium haematragum and Trochus maculatus— to predicted CO2 concentrations (400, 700 and 1000 ppm) and temperature conditions (ambient, +3 and +5°C). In line with metabolic theory, we found that urchin metabolic rate increased at future temperatures regardless of CO2 conditions, with evidence of metabolic acclimation to higher temperatures. The metabolic rate of A. haematragum was depressed only by CO2, whereas T. maculatus /i>initially had elevated metabolic rates at moderate CO2, which were depressed by the combination of the highest CO2 concentration and temperatures. Taxa showed differential survival, with no urchin mortality under any future conditions but substantial mortality of both gastropods under elevated temperatures regardless of CO2 concentration. Importantly, all species had substantially reduced algal consumption in response to elevated CO2, though the urchins only demonstrated an energetic mismatch under combined future CO2 and temperature. Therefore, despite sharing an ecological niche, these key grazers are likely to be differentially affected by future environmental conditions, potentially reducing the strength of eco logical compensatory responses depending on the functional redundancy in this grazing community.

Continue reading ‘Functionally redundant herbivores: urchin and gastropod grazers respond differently to ocean warming and rising CO2’

The regulations of varied carbon-nitrogen supplies to physiology and amino acid contents in Gracilariopsis lemaneiformis (Gracilariales, Rhodophyta)

Highlights

  • Growth, photosynthesis, and amino acid accumulation of G. lemaneiformis increases with higher nitrogen application.

  • Application of nitrogen fertiliser maybe an effective way to increase G. lemaneiformis yield with improved nutrient quality.

  • Seawater nitrogen enrichment may alleviate the physiological stress caused by high CO2 on G. lemaneiformis in the future.

Abstract

Gracilariopsis lemaneiformis (Gracilariales, Rhodophyta) is an important economic alga in Southern China. In the present study, G. lemaneiformis thalli collected from Nan’ao Island, China, were cultured in six different treatments with three carbon supply levels (20, 400 and 1000 μatm) and two nitrogen supply levels (15 and 300 μmol L1). The thalli were used in the examination of the effects of altered carbon supply and high nitrogen content in seawater on the growth, photosynthetic characteristics and amino acid (AA) content of this farmed algal species. Regardless of nitrogen levels, the relative growth rate of G. lemaneiformis increased with CO2 supply. Decrease and increase in the carbon supply of the culture both decreased the maximum quantum yield of photosystem PS II (Fv/Fm), initial slope of the rapid light curves (ɑ), non-photochemical quenching, maximum relative electron transport rate and AA content of G. lemaneiformis thalli. Moreover, under low and high CO2 supply conditions, the growth rates, Fv/Fm, antioxidant activities (SOD, CAT and POD) and AAs of G. lemaneiformis increases with higher nitrogen application (300 μmol L1). Our results indicated that the inhibition of growth, photosynthesis, and AA accumulation of G. lemaneiformis can be alleviated by appropriately increasing the concentration of nitrogen in seawater. We suggest that during G. lemaneiformis mariculture, the appropriate application of nitrogen fertiliser may be an effective way to increase algal yield with improved nutrient quality, and seawater nitrogen enrichment may alleviate the physiological stress caused by high CO2 on G. lemaneiformis in the future.

Continue reading ‘The regulations of varied carbon-nitrogen supplies to physiology and amino acid contents in Gracilariopsis lemaneiformis (Gracilariales, Rhodophyta)’

Response of bacterial communities in Barents Sea sediments in case of a potential CO2 leakage from carbon reservoirs

Highlights

  • Simulation of real conditions of a CCS site are essentials for environmental risk assessments.

  • Marine bacteria may adapt to a new situation in case of acidification event for a short time.

  • Marine bacteria community is altered in case of a CO2 leakage after 3 weeks in long-term simulation.

  • Results did not show a potential recovery of marine bacteria when CO2 was stopped within the monitored period.

Abstract

Carbon capture and storage sites in Barents Sea shelf are currently in progress as part of climate change mitigation activities. However environmental impacts of a possible CO2 seepage on bacterial community are lacking knowledge. This work addressed potential consequences on bacterial communities from Snøvit region in Barents Sea sediments. Long-term experiment (92 days) was carried out mimicking realistic conditions of pressure (∼30 bars) using the unique hyperbaric chamber (Karl Erik TiTank). The experiment was divided in three stages: i) 21 days of no CO2, ii) 50 days of simulation of carbon dioxide leakage (depletion of pH to 7.0) and iii) 14 days emulating a leakage cessation. Results suggested that bacterial communities can adapt to a CO2 leakage in short term. However, bacteria showed negative effects in terms of activity, community structure, and number of cells after long term CO2 exposure. After CO2 leakage cessation, bacterial communities did not show a significant recovery. These findings highlighted that, even though marine bacteria showed adaptation to the new conditions (acidified environment), in case of a small but continuous CO2 leakage marine bacteria might not be recovered upon pre-exposure status.

    Continue reading ‘Response of bacterial communities in Barents Sea sediments in case of a potential CO2 leakage from carbon reservoirs’

    Contrasting responses to salinity and future ocean acidification in arctic populations of the amphipod Gammarus setosus

    Highlights

    • Climate change is leading to changes in salinity and pCO2 in arctic/sub-arctic coastal ecosystems.

    • We examined Gammarus setosus at 3 sites along a salinity gradient in the field and laboratory.

    • Reduced salinity had more of an effect than elevated pCO2 by reducing energy budgets.

    • Lower salinities increased ion transporting capacities in the laboratory but not in the field.

    • G. setosus at lower salinity sites have lower energy budgets suggesting impacts on performance.

    Abstract

    Climate change is leading to alterations in salinity and carbonate chemistry in arctic/sub-arctic marine ecosystems. We examined three nominal populations of the circumpolar arctic/subarctic amphipod, Gammarus setosus, along a salinity gradient in the Kongsfjorden-/Krossfjorden area of Svalbard. Field and laboratory experiments assessed physiological (haemolymph osmolality and gill Na+/K+-ATPase activity, NKA) and energetic responses (metabolic rates, MO2, and Cellular Energy Allocation, CEA). In the field, all populations had similar osmregulatory capacities and MO2, but lower-salinity populations had lower CEA. Reduced salinity (S = 23) and elevated pCO2 (∼1000 μatm) in the laboratory for one month increased gill NKA activities and reduced CEA in all populations, but increased MO2 in the higher-salinity population. Elevated pCO2 did not interact with salinity and had no effect on NKA activities or CEA, but reduced MO2 in all populations. Reduced CEA in lower-rather than higher-salinity populations may have longer term effects on other energy demanding processes (growth and reproduction).

    Continue reading ‘Contrasting responses to salinity and future ocean acidification in arctic populations of the amphipod Gammarus setosus’

    Ocean acidification amplifies the olfactory response to 2-phenylethylamine: altered cue reception as a mechanistic pathway?

    With carbon dioxide (CO2) levels rising dramatically, climate change threatens marine environments. Due to increasing CO2 concentrations in the ocean, pH levels are expected to drop by 0.4 units by the end of the century. There is an urgent need to understand the impact of ocean acidification on chemical-ecological processes. To date, the extent and mechanisms by which the decreasing ocean pH influences chemical communication are unclear. Combining behaviour assays with computational chemistry, we explore the function of the predator related cue 2-phenylethylamine (PEA) for hermit crabs (Pagurus bernhardus) in current and end-of-the-century oceanic pH. We demonstrate that this dietary predator cue for mammals and sea lampreys is an attractant for hermit crabs. Furthermore, we show that the potency of the cue increases at pH levels expected for the year 2100. In order to explain this increased potency, we assess changes to PEA’s conformational and charge-related properties as one potential mechanistic pathway. Using quantum chemical calculations validated by NMR spectroscopy, we characterise the different protonation states of PEA in water. We show how protonation of PEA could affect receptor-ligand binding, using a possible model receptor for PEA (human TAAR1). Investigating potential mechanisms of pH dependent effects on olfactory perception of PEA and the respective behavioural response, our study advances the understanding of how ocean acidification interferes with the sense of smell and thereby might impact essential ecological interactions in marine ecosystems.

    Continue reading ‘Ocean acidification amplifies the olfactory response to 2-phenylethylamine: altered cue reception as a mechanistic pathway?’


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