Posts Tagged 'respiration'

Biochemical and physiological responses of two clam species to Triclosan combined with climate change scenario


• Triclosan bioaccumulation was enhanced under forecasted climate change conditions.

• Triclosan strongly affected clams’ antioxidant defences.

• Cellular damage was prevented by enzymatic and behaviour defence mechanisms.

• Greater response of the Manila clam to TCS exposure combined with climate change scenario.


Ocean acidification and warming are among the man-induced factors that most likely impact aquatic wildlife worldwide. Besides effects caused by temperature rise and lowered pH conditions, chemicals of current use can also adversely affect aquatic organisms. Both climate change and emerging pollutants, including toxic impacts in marine invertebrates, have been investigated in recent years. However, less information is available on the combined effects of these physical and chemical stressors that, in nature, occur simultaneously. Thus, this study contrasts the effects caused by the antimicrobial agent and plastic additive, Triclosan (TCS) in the related clams Ruditapes philippinarum (invasive) and Ruditapes decussatus (native) and evaluates if the impacts are influenced by combined temperature and pH modifications. Organisms were acclimated for 30 days at two conditions (control: 17 °C; pH 8.1 and climate change scenario: 20 °C, pH 7.7) in the absence of the drug (experimental period I) followed by a 7 days exposure under the same water physical parameters but either in absence (unexposed) or presence of TCS at 1 μg/L (experimental period II). Biochemical responses covering metabolic, oxidative defences and damage-related biomarkers were contrasted in clams at the end of experimental period II. The overall picture showed a well-marked antioxidant activation and higher TCS bioaccumulation of the drug under the forecasted climate scenario despite a reduction on respiration rate and metabolism in the exposed clams. Since clams are highly consumed shellfish, the consequences for higher tissue bioaccumulation of anthropogenic chemicals to final consumers should be alerted not only at present conditions but more significantly under predicted climatic conditions for humans but also for other components of the marine trophic chain.

Continue reading ‘Biochemical and physiological responses of two clam species to Triclosan combined with climate change scenario’

Corals exhibit distinct patterns of microbial reorganisation to thrive in an extreme inshore environment

Climate change threatens the survival of scleractinian coral from exposure to concurrent ocean warming, acidification and deoxygenation; how corals can potentially adapt to this trio of stressors is currently unknown. This study investigates three coral species (Acropora muricata, Acropora pulchra and Porites lutea) dominant in an extreme mangrove lagoon (Bouraké, New Caledonia) where abiotic conditions exceed those predicted for many reef sites over the next 100 years under climate change and compared them to conspecifics from an environmentally more benign reef habitat. We studied holobiont physiology as well as plasticity in coral-associated microorganisms (Symbiodiniaceae and bacteria) through ITS2 and 16S rRNA sequencing, respectively. We hypothesised that differences in coral-associated microorganisms (Symbiodiniaceae and bacteria) between the lagoonal and adjacent reef habitats may support coral host productivity and ultimately the ability of corals to live in extreme environments. In the lagoon, all coral species exhibited a metabolic adjustment of reduced photosynthesis-to-respiration ratios (P/R), but this was accompanied by highly divergent coral host-specific microbial associations. This was substantiated by the absence of shared ITS2-type profiles (proxies for Symbiodiniaceae genotypes). We observed that ITS2 profiles originating from Durusdinium taxa made up < 3% and a novel Symbiodinium ITS2 profile A1-A1v associated with A. pulchra. Bacterial community profiles were also highly divergent in corals from the lagoonal environment, whereas corals from the reef site were consistently dominated by Hahellaceae, Endozoicomonas. As such, differences in host–microorganism associations aligned with different physiologies and habitats. Our results argue that a multitude of host–microorganism associations are required to fulfill the changing nutritional demands of corals persisting into environments that parallel climate change scenarios.

Continue reading ‘Corals exhibit distinct patterns of microbial reorganisation to thrive in an extreme inshore environment’

Impacts of elevated temperature and pCO2 on the brooded larvae of Pocillopora damicornis from Luhuitou Reef, China: evidence for local acclimatization

In this study, we tested whether larvae brooded by the reef coral Pocillopora damicornis from a naturally extreme and highly variable environment are preadapted to cope with predicted increases in temperature and pCO2. We exposed larvae to two temperatures (29 vs. 30.8 °C) crossed with two pCO2 levels (~ 500 vs. ~ 1000 μatm) in a full-factorial experiment for 5 d. Larval performance was assessed as dark respiration (RD), net and gross photosynthesis (PN and PG, respectively), survival, settlement, and the activity of carbonic anhydrase (CA), the central enzyme involved in photosynthesis. The results showed that RD was unaffected by either elevated temperature or pCO2, while elevated temperature and/or pCO2 stimulated PN and PG and increased the ratios of PN to RD, indicating a relatively higher autotrophic capacity. Consequently, larval survivorship under elevated temperature and/or pCO2 was consistently 14% higher than that under the control treatment. Furthermore, elevated temperature and pCO2 did not affect host CA activity, but synergistically enhanced symbiont CA activity, contributing greatly to the stimulated photosynthetic capacity. These results suggest that brooded larvae of P. damicornis larvae from Luhuitou may be preadapted to cope with projected warming and ocean acidification. More generally, it appears that corals from highly variable environments may have increased resilience to the widespread climate change.

Continue reading ‘Impacts of elevated temperature and pCO2 on the brooded larvae of Pocillopora damicornis from Luhuitou Reef, China: evidence for local acclimatization’

Key biological responses over two generations of the sea urchin Echinometra sp. A under future ocean conditions

Few studies have investigated the effects of ocean warming and acidification on marine benthic organisms over ecologically relevant time scales. We used an environmentally controlled coral reef mesocosm system to assess growth and physiological responses of the sea urchin species Echinometra sp. A over 2 generations. Each mesocosm was controlled for temperature and pCO2 over 29 mo under 3 climate change scenarios (present day and predicted states in 2050 and 2100 under RCP 8.5). The system maintained treatment conditions including annual temperature cycles and a daily variation in pCO2. Over 20 mo, adult Echinometra exhibited no significant difference in size and weight among the treatments. Growth rates and respiration rates did not differ significantly among treatments. Urchins from the 2100 treatment had elevated ammonium excretion rates and reduced O2:N ratios, suggesting a change in catabolism. We detected no difference in spawning index scores or oocyte size after 20 mo in the treatments, suggesting that gonad development was not impaired by variations in pCO2 and temperature reflecting anticipated climate change scenarios. Larvae produced from experimentally exposed adults were successfully settled from all treatments and raised for 5 mo inside the mesocosm. The final size of these juveniles exhibited no significant difference among treatments. Overall, we demonstrated that the mesocosm system provided a near natural environment for this urchin species. Climate change and ocean acidification did not affect the benthic life stages investigated here. Importantly, in previous short-term (weeks to months) experiments, this species exhibited reductions in growth and gonad development, highlighting the potential for short-term experiments with non-acclimated animals to yield contrasting, possibly erroneous results.

Continue reading ‘Key biological responses over two generations of the sea urchin Echinometra sp. A under future ocean conditions’

Does ocean acidification benefit seagrasses in a mesohaline environment? a mesocosm experiment in the northern Gulf of Mexico

Ocean acidification is thought to benefit seagrasses because of increased carbon dioxide (CO2) availability for photosynthesis. However, in order to truly assess ecological responses, effects of ocean acidification need to be investigated in a variety of coastal environments. We tested the hypothesis that ocean acidification would benefit seagrasses in the northern Gulf of Mexico, where the seagrasses Halodule wrightii and Ruppia maritima coexist in a fluctuating environment. To evaluate if benefits of ocean acidification could alter seagrass bed composition, cores of H. wrightii and R. maritima were placed alone or in combination into aquaria and maintained in an outdoor mesocosm. Half of the aquaria were exposed to either ambient (mean pH of 8.1 ± 0.04 SD on total scale) or high CO2 (mean pH 7.7 ± 0.05 SD on total scale) conditions. After 54 days of experimental exposure, the δ13C values were significantly lower in seagrass tissue in the high CO2 condition. This integration of a different carbon source (either: preferential use of CO2, gas from cylinder, or both) indicates that plants were not solely relying on stored energy reserves for growth. Yet, after 41 to 54 days, seagrass morphology, biomass, photo-physiology, metabolism, and carbon and nitrogen content in the high CO2 condition did not differ from those at ambient. There was also no indication of differences in traits between the homospecific or heterospecific beds. Findings support two plausible conclusions: (1) these seagrasses rely heavily on bicarbonate use and growth will not be stimulated by near future acidification conditions or (2) the mesohaline environment limited the beneficial impacts of increased CO2 availability.

Continue reading ‘Does ocean acidification benefit seagrasses in a mesohaline environment? a mesocosm experiment in the northern Gulf of Mexico’

Model simulation of seasonal growth of Fucus vesiculosus in its benthic community

Numerical models are a suitable tool to quantify impacts of predicted climate change on complex ecosystems but are rarely used to study effects on benthic macroalgal communities. Fucus vesiculosus L. is a habitat‐forming macroalga in the Baltic Sea and alarming shifts from the perennial Fucus community to annual filamentous algae are reported. We developed a box model able to simulate the seasonal growth of the Baltic Fucus–grazer–epiphyte system. This required the implementation of two state variables for Fucus biomass in units of carbon (C) and nitrogen (N). Model equations describe relevant physiological and ecological processes, such as storage of C and N assimilates by Fucus, shading effects of epiphytes or grazing by herbivores on both Fucus and epiphytes, but with species‐specific rates and preferences. Parametrizations of the model equations and required initial conditions were based on measured parameters and process rates in the near‐natural Kiel Outdoor Benthocosm (KOB) experiments during the Biological Impacts of Ocean Acidification project. To validate the model, we compared simulation results with observations in the KOB experiment that lasted from April 2013 until March 2014 under ambient and climate‐change scenarios, that is, increased atmospheric temperature and partial pressure of carbon dioxide. The model reproduced the magnitude and seasonal cycles of Fucus growth and other processes in the KOBs over 1 yr under different scenarios. Now having established the Fucus model, it will be possible to better highlight the actual threat of climate change to the Fucus community in the shallow nearshore waters of the Baltic Sea.

Continue reading ‘Model simulation of seasonal growth of Fucus vesiculosus in its benthic community’

Effects of water acidification on Senegalese sole Solea senegalensis health status and metabolic rate: implications for immune responses and energy use

Increasing water CO2, aquatic hypercapnia, leads to higher physiological pCO2 levels in fish, resulting in an acidosis and compensatory acid-base regulatory response. Senegalese sole is currently farmed in super-intensive recirculating water systems where significant accumulation of CO2 in the water may occur. Moreover, anthropogenic releases of CO2 into the atmosphere are linked to ocean acidification. The present study was designed to assess the effects of acute (4 and 24 h) and prolonged exposure (4 weeks) to CO2 driven acidification (i.e., pH 7.9, 7.6, and 7.3) from normocapnic seawater (pH 8.1) on the innate immune status, gill acid-base ion transporter expression and metabolic rate of juvenile Senegalese sole. The acute exposure to severe hypercapnia clearly affected gill physiology as observed by an increase of NHE3b positive ionocytes and a decrease of cell shape factor. Nonetheless only small physiological adjustments were observed at the systemic level with (1) a modulation of both plasma and skin humoral parameters and (2) an increased expression of HIF-1 expression pointing to an adjustment to the acidic environment even after a short period (i.e., hours). On the other hand, upon prolonged exposure, the expression of several pro-inflammatory and stress related genes was amplified and gill cell shape factor was aggravated with the continued increase of NHE3b positive ionocytes, ultimately impacting fish growth. While these findings indicate limited effects on energy use, deteriorating immune system conditions suggest that Senegalese sole is vulnerable to changes in CO2 and may be affected in aquaculture where a pH drop is more prominent. Further studies are required to investigate how larval and adult Senegalese sole are affected by changes in CO2.

Continue reading ‘Effects of water acidification on Senegalese sole Solea senegalensis health status and metabolic rate: implications for immune responses and energy use’

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Ocean acidification in the IPCC AR5 WG II

OUP book