Posts Tagged 'growth'

Elevated water CO2 can prevent dietary-induced osteomalacia in post-smolt Atlantic salmon (Salmo salar, L.)

Expansion of land-based systems in fish farms elevate the content of metabolic carbon dioxide (CO2) in the water. High CO2 is suggested to increase the bone mineral content in Atlantic salmon (Salmo salar, L.). Conversely, low dietary phosphorus (P) halts bone mineralization. This study examines if high CO2 can counteract reduced bone mineralization imposed by low dietary P intake. Atlantic salmon post-seawater transfer (initial weight 207.03 g) were fed diets containing 6.3 g/kg (0.5P), 9.0 g/kg (1P), or 26.8 g/kg (3P) total P for 13 weeks. Atlantic salmon from all dietary P groups were reared in seawater which was not injected with CO2 and contained a regular CO2 level (5 mg/L) or in seawater with injected CO2 thus raising the level to 20 mg/L. Atlantic salmon were analyzed for blood chemistry, bone mineral content, vertebral centra deformities, mechanical properties, bone matrix alterations, expression of bone mineralization, and P metabolism-related genes. High CO2 and high P reduced Atlantic salmon growth and feed intake. High CO2 increased bone mineralization when dietary P was low. Atlantic salmon fed with a low P diet downregulated the fgf23 expression in bone cells indicating an increased renal phosphate reabsorption. The current results suggest that reduced dietary P could be sufficient to maintain bone mineralization under conditions of elevated CO2. This opens up a possibility for lowering the dietary P content under certain farming conditions.

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Acid times in physiology: a systematic review of the effects of ocean acidification on calcifying invertebrates

The reduction in seawater pH from rising levels of carbon dioxide (CO2) in the oceans has been recognized as an important force shaping the future of marine ecosystems. Therefore, numerous studies have reported the effects of ocean acidification (OA) in different compartments of important animal groups, based on field and/or laboratory observations. Calcifying invertebrates have received considerable attention in recent years. In the present systematic review, we have summarized the physiological responses to OA in coral, echinoderm, mollusk, and crustacean species exposed to predicted ocean acidification conditions in the near future. The Scopus, Web of Science, and PubMed databases were used for the literature search, and 75 articles were obtained based on the inclusion criteria. Six main physiological responses have been reported after exposure to low pH. Growth (21.6%), metabolism (20.8%), and acid-base balance (17.6%) were the most frequent among the phyla, while calcification and growth were the physiological responses most affected by OA (>40%). Studies show that the reduction of pH in the aquatic environment, in general, supports the maintenance of metabolic parameters in invertebrates, with redistribution of energy to biological functions, generating limitations to calcification, which can have severe consequences for the health and survival of these organisms. It should be noted that the OA results are variable, with inter and/or intraspecific differences. In summary, this systematic review offers important scientific evidence for establishing paradigms in the physiology of climate change in addition to gathering valuable information on the subject and future research perspectives.

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Assessing the impacts of simulated ocean alkalinity enhancement on viability and growth of cultures of near-shore species of phytoplankton

Over the past 250 years, atmospheric carbon dioxide concentrations have risen steadily from 277 ppm to 405 ppm, leading to the exacerbation of the effects of climate change. As a result, new technologies are being developed to remove carbon from the atmosphere, such as negative emission technologies (NETs). One proposed NET is Ocean Alkalinity Enhancement (OAE), which would mimic the ocean’s natural weathering processes and sequester carbon dioxide from the atmosphere. An analysis of published data investigating the effects of elevated pH on phytoplankton growth rate and experimental assessment of pH dependence of viability and growth rate was used to assess the potential impacts of OAE. Viability was assessed with a modified Serial Dilution Culture – Most Probable Number assay. Chlorophyll a fluorescence was used to test for changes in growth rates and photosynthetic competence. The results from this study suggest that there will be no significant impact on the viability or growth rates of Thalassiosira pseudonana or Pavlova lutheri with short-term (10 minute) exposure to elevated pH. However, when long-term (days) exposure occurs there is a significant decrease in growth rates with elevated pH. Short-term exposure is anticipated to more closely mirror the natural systems in which OAE will be implemented because of system flushing and replenishment of nutrients. These preliminary findings suggest that there will be little to no impact on a variety of taxonomic groups of phytoplankton when OAE occurs in naturally flushed systems.

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Addressing the joint impact of temperature and pH on Vibrio harveyi adaptation in the time of climate change

Global warming and acidification of the global ocean are two important manifestations of the ongoing climate change. To characterize their joint impact on Vibrio adaptation and fitness, we analyzed the temperature-dependent adaptation of Vibrio harveyi at different pHs (7.0, 7.5, 8.0, 8.3 and 8.5) that mimic the pH of the world ocean in the past, present and future. Comparison of V. harveyi growth at 20, 25 and 30 °C show that higher temperature per se facilitates the logarithmic growth of V. harveyi in nutrient-rich environments in a pH-dependent manner. Further survival tests carried out in artificial seawater for 35 days revealed that cell culturability declined significantly upon incubation at 25 °C and 30 °C but not at 20 °C. Moreover, although acidification displayed a negative impact on cell culturability at 25 °C, it appeared to play a minor role at 30 °C, suggesting that elevated temperature, rather than pH, was the key player in the observed reduction of cell culturability. In addition, analyses of the stressed cell morphology and size distribution by epifluorescent microscopy indicates that V. harveyi likely exploits different adaptation strategies (e.g., acquisition of coccoid-like morphology) whose roles might differ depending on the temperature–pH combination.

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Effects of dissolved carbon dioxide on growth and vertebral column of hybrid marine grouper (Epinephelus fuscoguttatus × E. lanceolatus) early advanced larvae


  • Ocean acidification negatively impacted the early advanced larvae of the marine hybrid tiger grouper × giant grouper (TG × GG).
  • Worst growth, survival, weight, food consumption, and conversion rates at 1000 ppm CO2.
  • Deformed vertebral columns were observed at 1000 ppm CO2, while normal vertebral column observed at 400 ppm CO2.
  • This study provides guidelines for future studies on TG × GG larvae or other marine fish larvae under elevated CO2 concentrations.


This study investigated the effects of different dissolved carbon dioxide (CO2) concentrations (400, 700, and 1000 ppm) on the growth and vertebral column formation of hybrid tiger grouper × giant grouper (TG × GG) in their advanced larval stage under controlled laboratory conditions for 12 weeks. Growth parameters, including specific growth rate (SGR), survival rate, food consumption (FC), and food conversion rate (FCR), were calculated at the end of the experiment. Vertebral column formation was analysed using X-radiography and osteology methods. The results showed that all growth parameters were significantly affected by CO2 concentration, with the best performances observed under 400 ppm CO2. The highest statistically significant (p < 0.05) SGR, survival rate, and FC were observed under 400 ppm CO2, whereas the lowest was observed under 1000 ppm CO2. The lowest FCR (0.40, p < 0.05) was observed in 400 ppm CO2 and the highest was observed at 1000 ppm CO2 (0.59, p < 0.05). Furthermore, larvae without vertebral column malformations were observed in 400 ppm CO2, while larvae with small angles of kyphosis were observed in 700 ppm CO2, and larvae with kyphosis, lordosis, and vertebral compression were observed in 1000 ppm CO2. Only six spine measurements out of 31 obtained under different CO2 concentrations were significantly different (p < 0.05). Overall, the results suggest that CO2 concentration plays a crucial role in the growth and vertebral column formation of TG × GG in their advanced larval stage. The optimal CO2 concentration for the aquaculture of TG × GG in their advanced larval stage was found to be 400 ppm or lower. This study highlights the importance of maintaining optimal CO2 concentrations to enhance the growth and health of fish in aquaculture systems…

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From marine snails to marine spatial planning : the science of human impacts and relationships with marine ecosystems

Extractive human systems are driving unprecedented biodiversity loss and exacerbating social inequity. The magnitude of the intertwined climate, biodiversity, and social inequity crises has prompted the development of interdisciplinary research approaches to address these complex problems. One such approach, social-ecological systems (SES), aims to understand the relationships between coupled human and ecological systems. This thesis applies an SES lens to understand the science of human impacts on and relationships with marine ecosystems and inform characterizations of system vulnerability. First, I examined the sensitivity of marine ectothermic animals to climate change by conducting a meta-analysis of the effects of ocean acidification and warming. My synthesis of nearly five hundred factorial studies demonstrates the negative effects of these two drivers, identifies specific taxonomic groups (molluscs), life- history traits (adults, sessile), and latitudes (tropical and temperate) that are more sensitive, and refutes two common assumptions about the drivers’ interactive effects. Next, I tested whether populations of a marine snail vary in their vulnerability to ocean warming based on thermal sensitivity and local rates of ocean warming. Using coupled lab and field experiments with snails from two regions in the middle of their range that differ in thermal characteristics, I found that snails from the warmer Salish Sea, an urban sea, showed greater vulnerability to ocean warming than those from the cooler central coast of British Columbia, Canada. Finally, to inform how humans can mitigate our impacts while sustaining complex relationships with the ocean, I partnered with the Sḵwx̲wú7mesh Úxwumixw (Squamish Nation) and regional stewardship organizations on a marine spatial planning project in the Salish Sea. I employed a mixed- methods community-based participatory mapping approach to characterize place-based values and outline opportunities to decolonize research and mapping processes. The results contribute important social data about place-based values, reveal value interactions, reflect knowledge system plurality, and identify avenues to advance reconciliation. Overall, this thesis highlights the vulnerability of marine life, particularly life within urban seas, to climate change and provides a roadmap for researchers and decision-makers to meaningfully steward the health and well-being of coastal social-ecological systems.

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Ocean acidification alters the benthic biofilm communities in intertidal soft sediments

Microphytobenthos (MPB) and bacterial biofilms play crucial roles in primary and secondary production, nutrient cycling and invertebrate settlement in coastal ecosystems, yet little is known of the effects of ocean acidification (OA) on these communities in intertidal soft sediments. To fill in this gap, a 28-day CO2 enhancement experiment was conducted for the benthic biofilms in soft intertidal sediments (muds and sands) from Qingdao, China. This experiment included three CO2 treatments: 400 ppm CO2 (control), 700 ppm CO2 and 1000 ppm CO2 (IPCC predicted value in 2100), which were established in a three-level CO2 incubator that can adjust the CO2 concentration in the overlying air. The effects of OA on benthic biofilms were assessed in the following three aspects: MPB biomass, biofilm community structure and microbial biogeochemical cycling (e.g., C-cycle, N-cycle and S-cycle). This study found that the 700 ppm CO2 treatment did not significantly affect the benthic biofilms in intertidal soft sediments, but the 1000 ppm CO2 treatment significantly altered the biofilm community composition and potentially their role in microbial biogeochemical cycling in sediments (especially in sandy sediments). For the bacterial community in biofilms, the 1000 ppm CO2 enhancement increased the relative abundance of Alteromonadales and Bacillales but decreased the relative abundance of Rhodobacterales and Flavobacteriales. For microbial biogeochemical cycling, the 1000 ppm CO2 treatment enhanced the potential of chemoheterotrophic activity, nitrate reduction and sulfur respiration in sediments, likely resulting in a more stressful environment (hypoxic and enriched H2S) for most benthic organisms. Even though incubations in this study were only 28 days long and thus couldn’t fully accommodate the range of longer-term adaptions, it still suggests that benthic biofilms in intertidal sandy sediments are likely to change significantly near the end of the century if anthropogenic CO2 emissions unmitigated, with profound implications on local ecosystems and biogeochemical cycling.

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Reallocation of elemental content and macromolecules in the coccolithophore Emiliania huxleyi to acclimate to climate change

Global climate change leads to simultaneous changes in multiple environmental drivers in the marine realm. Although physiological characterization of coccolithophores has been studied under climate change, there is limited knowledge on the biochemical responses of this biogeochemically important phytoplankton group to changing multiple environmental drivers. Here, we investigate the interactive effects of reduced phosphorus availability (4 to 0.4 µmol L−1), elevated pCO2 concentrations (426 to 946 µatm), and increasing light intensity (40 to 300 µmol photons m−2 s−1) on elemental content and macromolecules of the cosmopolitan coccolithophore Emiliania huxleyi. Reduced phosphorus availability reduces particulate organic nitrogen (PON) and protein contents per cell under 40 µmol photons m−2 s−1 but not under 300 µmol photons m−2 s−1. Reduced phosphorus availability and elevated pCO2 concentrations act synergistically to increase particulate organic carbon (POC) and carbohydrate contents per cell under 300 µmol photons m−2 s−1 but not under 40 µmol photons m−2 s−1. Reduced phosphorus availability, elevated pCO2 concentrations, and increasing light intensity act synergistically to increase the allocation of POC to carbohydrates. Under elevated pCO2 concentrations and increasing light intensity, enhanced carbon fixation could increase carbon storage in the phosphorus-limited regions of the oceans where E. huxleyi dominates the phytoplankton assemblages. In each type of light intensity, elemental-carbon-to-phosphorus (C:P) and nitrogen-to-phosphorus (N:P) ratios decrease with increasing growth rate. These results suggest that coccolithophores could reallocate chemical elements and energy to synthesize macromolecules efficiently, which allows them to regulate their elemental content and growth rate to acclimate to changing environmental conditions.

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Deoxygenation enhances photosynthetic performance and increases N2 fixation in the marine cyanobacterium Trichodesmium under elevated pCO2

Effects of changed levels of dissolved O2 and CO2 on marine primary producers are of general concern with respect to ecological effects of ongoing ocean deoxygenation and acidification as well as upwelled seawaters. We investigated the response of the diazotroph Trichodesmium erythraeum IMS 101 after it had acclimated to lowered pO2 (~60 μM O2) and/or elevated pCO2 levels (HC, ~32 μM CO2) for about 20 generations. Our results showed that reduced O2 levels decreased dark respiration significantly, and increased the net photosynthetic rate by 66 and 89% under the ambient (AC, ~13 μM CO2) and the HC, respectively. The reduced pO2 enhanced the N2 fixation rate by ~139% under AC and only by 44% under HC, respectively. The N2 fixation quotient, the ratio of N2 fixed per O2 evolved, increased by 143% when pO2 decreased by 75% under the elevated pCO2. Meanwhile, particulate organic carbon and nitrogen quota increased simultaneously under reduced O2 levels, regardless of the pCO2 treatments. Nevertheless, changed levels of O2 and CO2 did not bring about significant changes in the specific growth rate of the diazotroph. Such inconsistency was attributed to the daytime positive and nighttime negative effects of both lowered pO2 and elevated pCO2 on the energy supply for growth. Our results suggest that Trichodesmium decrease its dark respiration by 5% and increase its N2-fixation by 49% and N2-fixation quotient by 30% under future ocean deoxygenation and acidification with 16% decline of pO2 and 138% rise of pCO2 by the end of this century.

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Increased food resources help eastern oyster mitigate the negative impacts of coastal acidification

Oceanic absorption of atmospheric CO2 results in alterations of carbonate chemistry, a process coined ocean acidification (OA). The economically and ecologically important eastern oyster (Crassostrea virginica) is vulnerable to these changes because low pH hampers CaCO3 precipitation needed for shell formation. Organisms have a range of physiological mechanisms to cope with altered carbonate chemistry; however, these processes can be energetically expensive and necessitate energy reallocation. Here, the hypothesis that resilience to low pH is related to energy resources was tested. In laboratory experiments, oysters were reared or maintained at ambient (400 ppm) and elevated (1300 ppm) pCO2 levels during larval and adult stages, respectively, before the effect of acidification on metabolism was evaluated. Results showed that oysters exposed to elevated pCO2 had significantly greater respiration. Subsequent experiments evaluated if food abundance influences oyster response to elevated pCO2. Under high food and elevated pCO2 conditions, oysters had less mortality and grew larger, suggesting that food can offset adverse impacts of elevated pCO2, while low food exacerbates the negative effects. Results also demonstrated that OA induced an increase in oyster ability to select their food particles, likely representing an adaptive strategy to enhance energy gains. While oysters appeared to have mechanisms conferring resilience to elevated pCO2, these came at the cost of depleting energy stores, which can limit the available energy for other physiological processes. Taken together, these results show that resilience to OA is at least partially dependent on energy availability, and oysters can enhance their tolerance to adverse conditions under optimal feeding regimes.

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Photoinhibition of the picophytoplankter Synechococcus is exacerbated by ocean acidification

The marine picocyanobacterium Synechococcus accounts for a major fraction of the primary production across the global oceans. However, knowledge of the responses of Synechococcus to changing pCO2 and light levels has been scarcely documented. Hence, we grew Synechococcus sp. CB0101 at two CO2 concentrations (ambient CO2 AC:410 μatm; high CO2 HC:1000 μatm) under various light levels between 25 and 800 μmol photons m−2 s−1 for 10–20 generations and found that the growth of Synechococcus strain CB0101 is strongly influenced by light intensity, peaking at 250 μmol m−2 s−1 and thereafter declined at higher light levels. Synechococcus cells showed a range of acclimation in their photophysiological characteristics, including changes in pigment content, optical absorption cross section, and light harvesting efficiency. Elevated pCO2 inhibited the growth of cells at light intensities close to or greater than saturation, with inhibition being greater under high light. Elevated pCO2 also reduced photosynthetic carbon fixation rates under high light but had smaller effects on the decrease in quantum yield and maximum relative electron transport rates observed under increasing light intensity. At the same time, the elevated pCO2 significantly decreased particulate organic carbon (POC) and particulate organic nitrogen (PON), particularly under low light. Ocean acidification, by increasing the inhibitory effects of high light, may affect the growth and competitiveness of Synechococcus in surface waters in the future scenario.

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Response of juvenile Saccharina japonica to the combined stressors of elevated pCO2 and excess copper

Coastal macroalgae may be subjected to global and local environmental stressors, such as ocean acidification and heavy-metal pollution. We investigated the growth, photosynthetic characteristics, and biochemical compositions of juvenile sporophytes of Saccharina japonica cultivated at two pCO2 levels (400 and 1000 ppmv) and four copper concentrations (natural seawater, control; 0.2 μM, low level; 0.5 μM, medium level; and 1 μM, high level) to better understand how macroalgae respond to ongoing environmental changes. The results showed that the responses of juvenile S. japonica to copper concentrations depended on the pCO2 level. Under the 400 ppmv condition, medium and high copper concentrations significantly decreased the relative growth rate (RGR) and non-photochemical quenching (NPQ) but increased the relative electron transfer rate (rETR) and chlorophyll a (Chl a), chlorophyll c (Chl c), carotenoid (Car), and soluble carbohydrate contents. At 1000 ppmv, however, none of the parameters had significant differences between the different copper concentrations. Our data suggest that excess copper may inhibit the growth of juvenile sporophytes of S. japonica, but this negative effect could be alleviated by CO2-induced ocean acidification.

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Acclimatization in a changing environment: linking larval and juvenile performance in the quahog Mercenaria mercenaria

Marine invertebrates in coastal communities are currently experiencing unprecedented, rapid environmental change. These symptoms of climate change and ocean acidification are projected to worsen faster than can be accommodated by evolutionary processes like adaptation via natural selection, necessitating investigations of alternative mechanisms that facilitate adaptive responses to environmental change. This dissertation posits that in the absence of adaptation, early development (larval) exposure to stressors can increase population tolerance by leveraging existing variation in the energy metabolism and host-microbial interactions. Focusing specifically on resiliency to acidification (low pH), hypoxia (low dissolved oxygen), and elevated temperature stress in the clam, Mercenaria mercenaria, this dissertation uses a combination of laboratory and field experiments in conjunction with next-generation sequencing and physiological assays to investigate the relationship between host health, microbial community structure, and environmental change.

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Sediment-seawater exchange altered adverse effects of ocean acidification towards marine microalgae


  • Five marine microalgal species showed different sensitivities to OA.
  • OA promoted algal growth except I. galbana after introducing sediments.
  • N, P and Fe released from sediments mitigated OA-induced toxicity to E. huxleyi.
  • OA-induced algal community instability was alleviated by the presence of sediments.


Ocean acidification (OA) exhibits high threat to marine microalgae. However, the role of marine sediment in the OA-induced adverse effect towards microalgae is largely unknown. In this work, the effects of OA (pH 7.50) on the growth of individual and co-cultured microalgae (Emiliania huxleyiIsochrysis galbanaChlorella vulgarisPhaeodactylum tricornutum, and Platymonas helgolandica tsingtaoensis) were systematically investigated in the sediment-seawater systems. OA inhibited E. huxleyi growth by 25.21 %, promoted P. helgolandica (tsingtaoensis) growth by 15.49 %, while did not cause any effect on the other three microalgal species in the absence of sediment. In the presence of the sediment, OA-induced growth inhibition of E. huxleyi was significantly mitigated, because the released chemicals (N, P and Fe) from seawater-sediment interface increased the photosynthesis and reduced oxidative stress. For P. tricornutum, C. vulgaris and P. helgolandica (tsingtaoensis), the growth was significantly increased in the presence of sediment in comparison with those under OA alone or normal seawater (pH 8.10). For I. galbana, the growth was inhibited when the sediment was introduced. Additionally, in the co-culturing system, C. vulgaris and P. tricornutum were the dominant species, while OA increased the proportions of dominant species and decreased the community stability as indicated by Shannon and Pielou’s indexes. After the introduction of sediment, the community stability was recovered, but remained lower than that under normal condition. This work demonstrated the role of sediment in the biological responses to OA, and could be helpful for better understanding the impact of OA on marine ecosystems.

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Will ocean acidification affect the digestive physiology and gut microbiota of whelk Brunneifusus ternatanus?

To understand the physiological responses of the Brunneifusus ternatanus to future ocean acidification (OA), histology, enzyme activity and gut bacterial composition at different pH levels (Control: C group, pH 8.1; Exposure period: EP group, pH 7.3) for 28 days were studied under laboratory conditions. Microbiota composition was analyzed using 16S rRNA gene amplicon sequencing. Enzyme activities of trypsin (TRY), lipase (LPS), amylase (AMS), and lysozyme (LZM) were used as biochemical indicators, as well as weight gain rate (WGR), specific growth rate (SGR) as growth indicators. The stress caused by OA resulted in alterations to the intestine, including partially swollen and degranulated enterocytes and rough endoplasmic reticulum (RER). The relative abundance of the core phylum in the acidified group changed significantly, showing an increase in Tenericutes and a decrease in Proteobacteria. Firmicutes/Bacteroides ratio declined from 4.38 in the control group to 1.25 in the EP group. We found that the enzymes TRY, LPS, and AMS activities were inhibited at reduced pH, which was positively correlated with the dominant genera Mycoplasma and Bacteroides; while LZM activities showed a significant increment, but showing a strong negative correlation. Furthermore, both WG and SRG values showed a depression at low pH lever. These results suggest that if anthropogenic CO2 emissions continue to accelerate, OA could negatively impact the whelk’s health, compromising their growth performance and even survival. These findings will benefit the future risk assessments of OA or other related emerging environmental issues.

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Effects of ocean acidification and eutrophication on the growth and photosynthetic performances of a green tide alga Ulva prolifera

With the impact of fossil fuel burning and industrialization, atmospheric CO2 concentration will reach about 1000 ppmv in 2100, and more and more CO2 will be absorbed by ocean, resulting in ocean acidification. The Chinese coastal waters are showing unexpectedly high levels of acidification due to a combination of global ocean acidification and severe regional eutrophication, which is caused by natural accumulation or human activities such as aquacultural tail water input, potentially affecting macroalgal blooms. However, little is known about the combined effects of ocean acidification and entrophication on the eco-physiology of bloom-forming macroalgae. This study investigated Ulva prolifera, a dominant species causing green tide in the South Yellow Sea, and explored its growth and physiological responses under the combination conditions of ocean acidification and enriched nutrients. In this study, U. prolifera thalli were cultured under two CO2 conditions (air and 1000 μatm) and two nutrient conditions (High Nutrient, HN, 135 μmol L-1 N and 8.5 μmol L-1 P; Normal Nutrient, NN, 27 μmol L-1 N and 1.7 μmol L-1 P). The results showed that eutrophication conditions obviously enhanced the relative growth rate and photosynthetic performance of U. prolifera. Elevated pCO2 had no significant effect on U. prolifera growth and photosynthetic performance under normal nutrient conditions. However, under eutrophication conditions elevated pCO2 inhibited U. prolifera growth. Moreover, eutrophication conditions markedly improved the contents of chlorophyll a, chlorophyll b and nitrate reductase activity and inhibited the soluble carbohydrate content, but elevated pCO2 had no significant effect on them under nutrient-replete conditions. In addition, elevated pCO2 significantly reduced the carotenoid content under eutrophication conditions and had no effect on it under normal nutrient conditions. These findings indicate that seawater eutrophication would greatly accelerate U. prolifera bloom, which may also be suppressed to a certain extent by ocean acidification in the future. The study can provide valuable information for predicting the future outbreaks of U. prolifera green tide in nearshore regions.

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Assessing the impact of different carbonate system parameters on benthic foraminifera from controlled growth experiments

Insights into past marine carbon cycling and water mass properties can be obtained by means of geochemical proxies calibrated through controlled laboratory experiments with accurate seawater carbonate system (C-system) manipulations. Here, we explored the use of strontium/calcium ratio (Sr/Ca) of the calcite shells of benthic foraminifera as a potential seawater C-system proxy through a controlled growth experiment with two deep-sea species (Bulimina marginata and Cassidulina laevigata) and one intertidal species (Ammonia T6). To this aim, we used two experimental set-ups to decouple as much as possible the individual components of the carbonate system, i.e., changing pH at constant dissolved inorganic carbon (DIC) and changing DIC at constant pH. Four climatic chambers were used with different controlled concentrations of atmospheric pCO2 (180 ppm, 410 ppm, 1000 ppm, 1500 ppm). Our results demonstrated that pH did not influence the survival and growth of the three species. However, low DIC conditions (879 μmol kg−1) negatively affected B. marginata and C. laevigata through reduced growth, whereas no effect was observed for Ammonia T6. Our results also showed that Sr/Ca was positively correlated with total Alkalinity (TA), DIC and bicarbonate ion concentration ([HCO3]) for Ammonia T6 and B. marginata; i.e., DIC and/or [HCO3] were the main controlling factors. For these two species, the regression models were coherent with published data (existing so far only for Ammonia T6) and showed overall similar slopes but different intercepts, implying species-specific effects. Furthermore, the Sr/Ca – C-system relationship was not impacted by ontogenetic trends between chamber stages, which is a considerable advantage for paleo-applications. This applied particularly to Ammonia T6 that calcified many chambers compared to the two other species. However, no correlation with any of the C-system parameters was observed for Sr/Ca in C. laevigata. This might imply either a strong species-specific effect and/or a low tolerance to laboratory conditions leading to a physiological stress, thereby impacting the Sr incorporation into the calcite lattice of C. laevigata.

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Enormously enhanced particulate organic carbon and nitrogen production by elevated CO2 and moderate aluminum enrichment in the coccolithophore Emiliania huxleyi

Aluminum (Al) is abundant and ubiquitous in the environment. However, little information is available on its effects on photosynthetic microbes in alkaline seawater. Thus, we investigated the physiological performance in the most cosmopolitan coccolithophorid, viz., Emiliania huxleyi, grown under low (410 µatm) and high (1000 µatm) CO2 levels in seawater having none (0 nM, NAl), low (0.2 µM, LAl) and high (2 µM, HAl) Al concentrations. Under low CO2 conditions, the specific growth rate showed no significant difference between the NAl and LAl treatments, which was higher than the HAL treatment. Elevated CO2 inhibited the growth rate in the NAl and LAl cultures but did not affect the HAl cultures. The addition of Al had no effects on (LAl) or slightly elevated (HAl) the particulate organic carbon (POC) production rate under low CO2 conditions. With increasing CO2 concentration, the production rate of POC was enhanced by 55.3 % during the NAl treatment and further increased by 22.3 % by adding 0.2 µM Al. The responses of particulate organic nitrogen (PON) production rate, cellular POC, and PON contents to the different treatments revealed the same pattern as those of the POC production rate. The particulate inorganic carbon (PIC) production rate and PIC/POC ratio were not affected by Al under low CO2 conditions. They were significantly decreased by elevated CO2 in the LAl and HAl cultures. Our results indicate that high CO2 could increase carbon export to ocean depths by elevating the efficiency of the biological pump at low Al levels occurring in natural seawater (0.2 μM), with potentially significant implications for the carbon cycle of the ocean under accelerating anthropogenic influences.

Continue reading ‘Enormously enhanced particulate organic carbon and nitrogen production by elevated CO2 and moderate aluminum enrichment in the coccolithophore Emiliania huxleyi’

Interaction of CO2 and light availability on photophysiology of tropical coccolithophorids (Emiliania huxleyi, Gephyrocapsa oceanica, and Ochosphaera sp.)

The study to examine the calcification rate, adaptation, and the biotic response of three tropical coccolithophorids (Emiliania huxleyi, Gephyrocapsa oceanica, and Ochosphaera sp) to changes in CO2 concentration. Three selected calcifying coccolitophorids were grown at batch culture with CO2 system at two levels of CO2 (385 and 1000 ppm) and two light dark periods. The parameters measured and calculation including growth rate, particulate organic carbon content, particulate inorganic carbon content, chlorophyll a, cell size, photosynthetic, organic, inorganic carbon production, photosynthesis, and calcification rate.  The results showed that there was a different response to carbonate chemistry changes and dark and light periods in any of the analyzed parameters.  The growth rate of three selected calcifying microalgae tested was decreasing significantly at high concentrations of CO2 (1000 ppm) treatment on 14:10 hour light: dark periods. However, there was no significant difference between the two CO2 concentrations where they were illuminated by 24 hours light in growth rate.  The increasing CO2 concentration and light-dark periods were species-specific responses to photosynthesis and calcification rate for three selected calcifying microalgae.

Continue reading ‘Interaction of CO2 and light availability on photophysiology of tropical coccolithophorids (Emiliania huxleyi, Gephyrocapsa oceanica, and Ochosphaera sp.)’

Antagonism toxicity of CuO nanoparticles and mild ocean acidification to marine algae

Graphical abstract

The toxicity of CuO nanoparticles (NPs) to marine microalgae (Emiliania huxleyi) under ocean acidification (OA) conditions (pHs 8.10, 7.90, 7.50) was investigated. CuO NPs (5.0 mg/L) caused significant toxicity (e.g., 48-h growth inhibition, 20%) under normal pH (8.10), and severe OA (pH 7.50) increased the toxicity of CuO NPs (e.g., 48-h growth inhibition, 68%). However, toxicity antagonism was observed with a growth inhibition (48 h) decreased to 37% after co-exposure to CuO NPs and mild OA (pH 7.90), which was attributed to the released Cu2+ ions from CuO NPs. Based on biological responses as obtained from RNA-sequencing, the dissolved Cu2+ ions (0.078 mg/L) under mild OA were found to increase algae division (by 17%) and photosynthesis (by 28%) through accelerating photosynthetic electron transport and promoting ATP synthesis. In addition, mild OA enhanced EPS secretion by 41% and further increased bioavailable Cu2+ ions, thus mitigating OA-induced toxicity. In addition, excess Cu2+ ions could be transformed into less toxic Cu2S and Cu2O based on X-ray absorption near-edge spectroscopy (XANES) and high-resolution transmission electron microscopy (HR-TEM), which could additionally regulate the antagonism effect of CuO NPs and mild OA. The information advances our knowledge in nanotoxicity to marine organisms under global climate change.

Continue reading ‘Antagonism toxicity of CuO nanoparticles and mild ocean acidification to marine algae’

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