Posts Tagged 'biological response'



Selective breeding of edible bivalves and its implication of global climate change

Bivalve molluscs are very nutritious and are an important source of human animal protein. To date, bivalve farming has contributed to about 15% of the mean per capita animal protein intake of approximate 1.5 billion people around the world. Unfortunately, the effects of climate change, mainly global warming and ocean acidification, have had many deleterious effects on bivalve aquaculture, not only leading to mass mortalities of bivalves in farms and hatcheries, but also causing collapse of natural bivalve populations. In response to the recurrent mass mortalities of farmed bivalves, many selective breeding programmes have been launched with the breeding goal of reducing mortality rate caused by disease outbreaks and changing ocean conditions. This article reviews the progress and potential of selective breeding of edible bivalves in the context of global climate change. It is clear from the literature that in terms of environmental sensitivity, and disease resistance and tolerance, selective breeding has great potential for improving the robustness of edible bivalves with significant heritability and genetic gain. Because the robustness of edible bivalves to climate change is a complex trait affected by multiple genes, the application of modern genomic tools in selective breeding is expected to dramatically enhance the accuracy and efficacy of genetic improvements and produce bivalve strains that are robust to climate change. The information in this article is very useful for guidance on adaptation strategies for climate‐smart bivalve aquaculture solutions to be implemented in bivalve hatcheries and farms.

Continue reading ‘Selective breeding of edible bivalves and its implication of global climate change’

Bioprocess strategies for enhancing the outdoor production of Nannochloropsis gaditana: an evaluation of the effects of pH on culture performance in tubular photobioreactors

A priority of the industrial applications of microalgae is the reduction of production costs while maximizing algae biomass productivity. The purpose of this study was to carry out a comprehensive evaluation of the effects of pH control on the production of Nannochloropsis gaditana in tubular photobioreactors under external conditions while considering the environmental, biological, and operational parameters of the process. Experiments were carried out in 3.0 m3 tubular photobioreactors under outdoor conditions. The pH values evaluated were 6.0, 7.0, 8.0, 9.0, and 10.0, which were controlled by injecting pure CO2 on-demand. The results have shown that the ideal pH for microalgal growth was 8.0, with higher values of biomass productivity (Pb) (0.16 g L−1 d−1), and CO2 use efficiency (ECO2) (74.6% w w−1); RCO2/biomass value obtained at this pH (2.42 gCO2 gbiomass−1) was close to the theoretical value, indicating an adequate CO2 supply. At this pH, the system was more stable and required a lower number of CO2 injections than the other treatments. At pH 6.0, there was a decrease in the Pb and ECO2; cultures at pH 10.0 exhibited a lower Pb and photosynthetic efficiency as well. These results imply that controlling the pH at an optimum value allows higher CO2 conversions in biomass to be achieved and contributes to the reduction in costs of the microalgae production process.

Continue reading ‘Bioprocess strategies for enhancing the outdoor production of Nannochloropsis gaditana: an evaluation of the effects of pH on culture performance in tubular photobioreactors’

Effects of low and high pH on sea urchin settlement, implications for the use of alkali to counter the impacts of acidification

Highlights

• Seaweeds and diatoms on settlement plates created low pH and high pH conditions as they respired and photosynthesised.

• Low pH had adverse effects on growth and morphology of sea urchin post-larvae.

• High pH generally had little effect on growth and development, but reduced settlement rates.

• Controlling pH in invertebrate culture systems might improve settlement rates and post-settlement growth.

Abstract

Respiration, photosynthesis, and calcification of cultured organisms and biological substrata can substantially alter the pH and other carbonate parameters of water in aquaculture systems. One such example is the diel cycle of photosynthesis and respiration by diatoms and seaweeds growing on ‘settlement plates’ used to induce metamorphosis of invertebrate larvae and as food for post-larvae. We documented low pH and high pH conditions in nursery raceways and simulated settlement tanks that were as much as 0.26 pH units lower and 0.52 pH units higher than the pH of the source seawater supplied to the systems. To better understand whether the low pH and high pH conditions commonly found in aquaculture culture systems affected the success of the settlement stage of the sea urchin Centrostephanus rodgersii, we induced larvae to settle at pH 7.6, 7.8 (created by injecting CO2), 8.1 (ambient), 8.2, and 8.3 (created by raising total alkalinity), and followed post-settlement growth, development, and survival for 16 d. At metamorphosis, low pH significantly increased the occurrence of abnormalities and reduced the number and length of the sea urchins’ spines and pedicellaria, but did not affect settlement rate or size compared to ambient pH. In contrast, high pH generally had little effect on morphological traits, but settlement was significantly reduced by 14–26% compared to ambient and low pH treatments. After 16 d, juveniles in the low pH treatments were as much as 7% smaller, had 2–4 fewer and 9–13% shorter spines, and had less-developed digestive systems compared to juveniles in ambient or high pH treatments, and there was a non-significant trend towards lower survival in low pH treatments. Our results highlight that the low pH and high pH conditions in invertebrate settlement and nursery culture systems have the potential to hamper production through reduced settlement or growth rates. We need to understand the impacts of fluctuating pH in culture systems, especially day-night oscillations. Treating seawater with alkali chemicals to stabilise pH and counter acidification should be done with caution. Due to the potential for deleterious effects on settlement, dosage regimens will need to be optimised.

Continue reading ‘Effects of low and high pH on sea urchin settlement, implications for the use of alkali to counter the impacts of acidification’

CO2-induced low pH in an eastern oyster (Crassostrea virginica) hatchery positively affects reproductive development and larval survival but negatively affects larval shape and size, with no intergenerational linkages

In North America, studies regarding effects of CO2-induced low pH in bivalve aquaculture are largely restricted to the US Pacific coast. Studies on species from the northwest Atlantic are lacking. Furthermore, information on the roles of intergenerational exposure and biological sex in bivalve responses to low pH, particularly in an aquaculture-specific context, is scant. We tested if short-term (1 month) exposure to CO2-induced reductions in pHNBS affected the reproductive development of male and female eastern oysters (Crassostrea virginica) during hatchery-specific reproductive conditioning and whether maternal and/or paternal exposure influenced larval responses. Reduced pH (7.5–7.7) increased the rate of reproductive development in both males and females. There was no indication of intergenerational effects; adult pH conditions did not affect early larval development. In contrast, low pH conditions experienced by gametes during spawning, fertilization, and embryo incubation (48 h) resulted in higher larval survival (+6–8% from control), reduced shell height (−2 to 3 µm), and increased deformities (abnormal shell shape; +3–5%). We suggest that local adaptation to acidic land runoff may account for the positive effects of low pH observed in this study. Bioeconomic assessments are now needed to understand the implications of reduced pH on aquaculture operations in these regions of Atlantic Canada.

Continue reading ‘CO2-induced low pH in an eastern oyster (Crassostrea virginica) hatchery positively affects reproductive development and larval survival but negatively affects larval shape and size, with no intergenerational linkages’

Impacts of ocean acidification under multiple stressors on typical organisms and ecological processes

The oceans are taking up over one million tons of fossil CO2 per hour, resulting in increased pCO2 and declining pH, leading to ocean acidification (OA). At the same time, accumulation of CO2 and other greenhouse gases is causing ocean warming, which enhances stratification with thinned upper mixed layers, exposing planktonic organisms to increasing levels of daytime integrated UV radiation. Ocean warming also reduces dissolved oxygen in seawater, resulting in ocean deoxygenation. All these ocean global changes are impacting marine ecosystems and effects are well documented for each individual driver (pH, oxygen, temperature, UV). However, combined effects are still poorly understood, strongly limiting our ability to project impacts at regional or local levels. Different regions are often exposed (and often adapted) to contrastingly different physical and chemical environmental conditions and organisms, and ecosystems from different parts of the world will be exposed to unique combinations of stressors in the future. Understanding the modulating role of adaptation, species niche and stressors’ interaction is key. This review, being a non-exhaustively explored one, aims to provide an overview on understandings of ecophysiological effects of OA and its combination with covarying drivers, mainly warming, deoxygenation and solar UV radiation. We propose a testable hypothetical model as well as future research perspectives.

Continue reading ‘Impacts of ocean acidification under multiple stressors on typical organisms and ecological processes’

Reduced growth with increased quotas of particulate organic and inorganic carbon in the coccolithophore Emiliania huxleyi under future ocean climate change conditions

Effects of ocean acidification and warming on marine primary producers can be modulated by other environmental factors, such as levels of nutrients and light. Here, we investigated the interactive effects of five oceanic environmental drivers (CO2, temperature, light, dissolved inorganic nitrogen and phosphate) on growth rate, particulate organic (POC) and inorganic (PIC) carbon quotas of the cosmopolitan coccolithophore Emiliania huxleyi. Population growth rate increased with increasing temperature (16 to 20 °C) and light intensities (60 to 240 μmol photons m−2  s−1), but decreased with elevated pCO2 concentrations (370 to 960 μatm) and reduced availability of nitrate (24.3 to 7.8 μmol L−1) and phosphate (1.5 to 0.5 μmol L−1). POC quotas were predominantly enhanced by combined effects of increased pCO2 and decreased availability of phosphate. PIC quotas increased with decreased availability of nitrate and phosphate. Our results show that concurrent changes in nutrient concentrations and pCO2 levels predominantly affected growth, photosynthetic carbon fixation and calcification of E. huxleyi, and imply that plastic responses to progressive ocean acidification, warming and decreasing availability of nitrate and phosphate reduce population growth rate while increasing cellular quotas of particulate organic and inorganic carbon of E. huxleyi, ultimately affecting coccolithophore-related ecological and biogeochemical processes.

Continue reading ‘Reduced growth with increased quotas of particulate organic and inorganic carbon in the coccolithophore Emiliania huxleyi under future ocean climate change conditions’

Regional and species level responses of Scleractinian corals under global change within the Caribbean Sea

Human-induced global change has caused rapid increases in ocean temperature (warming) and declines in seawater pH (acidification), and are expected to have negative impacts on tropical reef-building corals globally. Abnormally high seawater temperatures disrupt the symbiosis between corals and their algal endosymbiont in a process known as ‘coral bleaching.’ During such bleaching events, calcification rates decline and physiological processes deteriorate. Additionally, corals rely heavily on elevated seawater pH in order to support and maintain production of their calcium carbonate skeletons. Together, changes in ocean temperatures and seawater pH pose serious threats to coral reefs, foundational ecosystems that provide habitat for countless essential fisheries, while also acting as natural buffers from storms and providing major economic support for tropical coastal communities. Identifying how these global scale stressors impact Caribbean coral reefs is critical in understanding community composition and coral abundance on future reefs. This dissertation employs an interdisciplinary suite of techniques to assess the impacts of ocean acidification and warming on the growth and physiology of Caribbean corals to improve understandings of the responses of coral under projected global change, and provide a framework for similar future studies. Through the use of a meta-analysis (Chapter 1), I identified trends in coral calcification throughout the Greater Caribbean Sea in response to experimental ocean acidification and warming, and performed quantitative assessment of experimental design effects on coral calcification rates. I then conducted a 93- day simulated ocean acidification and warming mesocosm experiment to identify growth (Chapter 2, 4) and physiological (Chapter 3) responses of several species of common Caribbean corals. The results from this work highlight the diversity of responses of Caribbean corals to projected global change at individual and species levels, as well as between the coral host and algal endosymbiont. Overall, the variation in growth and physiological responses of these important Caribbean coral species under ocean acidification and warming is critical in predicting the future ‘winners’ and ‘losers’ of Caribbean reefs as global change unfolds.

Continue reading ‘Regional and species level responses of Scleractinian corals under global change within the Caribbean Sea’

Plasticity of adult coralline algae to prolonged increased temperature and pCO2 exposure but reduced survival in their first generation

Crustose coralline algae (CCA) are vital to coral reefs worldwide, providing structural integrity and inducing the settlement of important invertebrate larvae. CCA are known to be impacted by changes in their environment, both during early development and adulthood. However, long-term studies on either life history stage are lacking in the literature, therefore not allowing time to explore the acclimatory or potential adaptive responses of CCA to future global change scenarios. Here, we exposed a widely distributed, slow growing, species of CCA, Sporolithon cf. durum, to elevated temperature and pCO2 for five months and their first set of offspring (F1) for eleven weeks. Survival, reproductive output, and metabolic rate were measured in adult S. cf. durum, and survival and growth were measured in the F1 generation. Adult S. cf. durum experienced 0% mortality across treatments and reduced their O2 production after five months exposure to global stressors, indicating a possible expression of plasticity. In contrast, the combined stressors of elevated temperature and pCO2 resulted in 50% higher mortality and 61% lower growth on germlings. On the other hand, under the independent elevated pCO2 treatment, germling growth was higher than all other treatments. These results show the robustness and plasticity of S. cf. durum adults, indicating the potential for them to acclimate to increased temperature and pCO2. However, the germlings of this species are highly sensitive to global stressors and this could negatively impact this species in future oceans, and ultimately the structure and stability of coral reefs.

Continue reading ‘Plasticity of adult coralline algae to prolonged increased temperature and pCO2 exposure but reduced survival in their first generation’

The impacts of ocean acidification on marine ecosystems and reliant human communities

Rising atmospheric carbon dioxide (CO2) levels, from fossil fuel combustion and deforestation, along with agriculture and land-use practices are causing wholesale increases in seawater CO2 and inorganic carbon levels; reductions in pH; and alterations in acid-base chemistry of estuarine, coastal, and surface open-ocean waters. On the basis of laboratory experiments and field studies of naturally elevated CO2 marine environments, widespread biological impacts of human-driven ocean acidification have been posited, ranging from changes in organism physiology and population dynamics to altered communities and ecosystems. Acidification, in conjunction with other climate change–related environmental stresses, particularly under future climate change and further elevated atmospheric CO2 levels, potentially puts at risk many of the valuable ecosystem services that the ocean provides to society, such as fisheries, aquaculture, and shoreline protection. This review emphasizes both current scientific understanding and knowledge gaps, highlighting directions for future research and recognizing the information needs of policymakers and stakeholders.

Continue reading ‘The impacts of ocean acidification on marine ecosystems and reliant human communities’

Effects of seawater salinity and pH on cellular metabolism and enzyme activities in biomineralizing tissues of marine bivalves

Highlights

•Effects of salinity and pH on cellular metabolism were studied in bivalves.

•Biomineralizing cells had robust metabolism in the studied salinity and pH range.

•Oxygen consumption and protein synthesis rates declined at low pH.

•Na+/K+ ATPase activity increased at low salinity.

•H+ and Ca2+ transport activities were little affected by salinity and pH variation.

Abstract

Molluscan shell formation is a complex energy demanding process sensitive to the shifts in seawater CaCO3 saturation due to changes in salinity and pH. We studied the effects of salinity and pH on energy demand and enzyme activities of biomineralizing cells of the Pacific oyster (Crassostrea gigas) and the hard-shell clam (Mercenaria mercenaria). Adult animals were exposed for 14 days to high (30), intermediate (18), or low (10) salinity at either high (8.0-8.2) or low (7.8) pH. Basal metabolic cost as well as the energy cost of the biomineralization-related cellular processes were determined in isolated mantle edge cells and hemocytes. The total metabolic rates were similar in the hemocytes of the two studied species, but considerably higher in the mantle cells of C. gigas compared with those of M. mercenaria. Cellular respiration was unaffected by salinity in the clams’ cells, while in oysters’ cells the highest respiration rate was observed at intermediate salinity (18). In both studied species, low pH suppressed cellular respiration. Low pH led to an upregulation of Na+/K+ ATPase activity in biomineralizing cells of oysters and clams. Activities of Ca2+ ATPase and H+ ATPase, as well as the cellular energy costs of Ca2+ and H+ transport in the biomineralizing cells were insensitive to the variation in salinity and pH in the clams and oysters. Species-specific variability in cellular response to low salinity and pH indicates that the disturbance of shell formation under these conditions has different underlying mechanisms in the two studied species.

Continue reading ‘Effects of seawater salinity and pH on cellular metabolism and enzyme activities in biomineralizing tissues of marine bivalves’

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