Under predicted future ocean conditions, corals will experience frequent and intense thermal stress events while simultaneously being exposed to chronic ocean acidification. Yet, some corals will likely be more resistant and/or resilient to these predicted conditions than others and may be critical to reef persistence in the future. Following natural thermal stress in two consecutive years (2014 and 2015), we evaluated the effects of feeding and simulated ocean acidification on the physiological recovery of Montipora capitata and Porites compressa sourced from Kāneʻohe Bay and Waimānalo Bay, Hawaiʻi. Following the 2014 thermal stress event, simulated ocean acidification did not slow recovery of the holobiont and feeding enhanced recovery. However, feeding did not decrease susceptibility to the 2015 thermal stress event, and simulated ocean acidification did not increase susceptibility. Recovery strategies employed between species and between sites clearly differed, highlighting that coral reef restoration and management should consider species-level and site-specific vulnerabilities. Overall, our findings call attention to the immediate threat which ocean warming presents, the lack of additional stress to the holobiont from ocean acidification, the importance of heterotrophy in coral resilience, and the potential significance of additional local biotic stressors (i.e., predator outbreaks) for coral resiliency under annual thermal stress.
Continue reading ‘Ocean acidification does not prolong recovery of coral holobionts from natural thermal stress in two consecutive years’Posts Tagged 'nutrients'
Ocean acidification does not prolong recovery of coral holobionts from natural thermal stress in two consecutive years
Published 24 September 2024 Science ClosedTags: adaptation, biological response, BRcommunity, calcification, corals, laboratory, mortality, multiple factors, North Pacific, nutrients, otherprocess, physiology, protists, zooplankton
Lactiplantibacillus plantarum I induces gonad growth in the queen scallop Aequipecten opercularis (Linnaeus, 1758) under conditions of climate change
Published 19 September 2024 Science ClosedTags: biological response, laboratory, Mediterranean, mollusks, morphology, multiple factors, nutrients, physiology, prokaryotes
Climate change has presented a serious problem in recent times, which is why a new approach is being sought in terms of aquacultural food quality. In this study, the influence of temperature increase (by 2 °C) and pH decrease (by 0.2) was investigated on the queen scallop, Aequipecten opercularis (Linnaeus, 1758). Furthermore, the effect of a food-enriched diet with the probiotic culture Lactiplantibacillus plantarum I was assessed in climate-changed conditions. Scallops’ morphometric parameters were measured before the experimental setup and after one month of being kept in controlled conditions. Morphometric parameters included the elongation index, compactness index, convexity index, density index, condition index, meat yield, gonadosomatic index, adductor muscle index, and hepatosomatic index. Climate-changed conditions had no effect on the scallop condition index, meat yield, or hepatosomatic index. Nevertheless, the addition of probiotics to their diet had a positive effect on the queen scallops cultivated under conditions of climate change, influencing positive allometry and the increase of the gonadosomatic indices. On the other hand, the same conditions negatively affected the adductor muscle index of the scallops. To conclude, in the context of climate change conditions, queen scallops could be a good organism of choice that can be very well adapted to the changed environmental conditions, especially with the addition of the lactic acid bacteria culture Lpb. plantarum I.
Continue reading ‘Lactiplantibacillus plantarum I induces gonad growth in the queen scallop Aequipecten opercularis (Linnaeus, 1758) under conditions of climate change’Interactive effects of ocean acidification and nitrate on Ulva lactuca
Published 2 July 2024 Science ClosedTags: algae, biological response, chemistry, growth, laboratory, multiple factors, nutrients, photosynthesis, respiration
The global ocean is undergoing gradual acidification and eutrophication which may have significant impacts on macroalgal communities. However, little is known regarding the interactive effects of ocean acidification (OA) and nitrate on Ulva lactuca, a primary producer widely distributed in coastal waters. This study focuses on the possible interactive effects of OA and elevated nitrate levels on physiological parameters of U. lactuca. Higher nitrate levels may increase growth, photosynthesis, respiration, pigment synthesis, Fv/Fm and Effective Quantum Yield, whereas CO2 enrichment may result in a reduction in photosynthesis, pigment content, Fv/Fm and Effective Quantum Yield. Higher nitrate levels increase NO3– uptake rate and nitrate reductase activity, which are further amplified by elevated CO2 levels. However, the stimulation of high nitrate towards pigment synthesis and photosynthesis is negatively affected by elevated CO2 levels. Our results suggest that U. lactuca could potentially increase its biomass in coastal eutrophic waters, and OA in the future is not expected to promote the growth of U. lactuca, but it can enhance its potential biofiltration to remove nitrate from coastal ecosystems.
Continue reading ‘Interactive effects of ocean acidification and nitrate on Ulva lactuca’Quantifying the impacts of multiple stressors on the production of marine benthic resources
Published 11 March 2024 Science ClosedTags: abundance, algae, biogeochemistry, biological response, BRcommunity, chemistry, communityMF, laboratory, mesocosms, methods, modeling, mollusks, morphology, mortality, multiple factors, North Atlantic, nutrients, otherprocess, performance, physiology, regionalmodeling, temperature
Coastal ecosystems are among the most heavily affected by climate change and anthropogenic activities, which impacts their diversity, productivity and functioning and puts many of the key ecosystem services that they provide at risk. Although empirical studies have moved beyond single-stressor-single-species experiments with limited extrapolation potential and have increasingly investigated the cumulative effects of simultaneously occurring multiple stressors, consistent generalities have not yet been identified. Upscaling from controlled experiments to natural ecosystems, therefore, remains an unsolved challenge. Disentangling the independent and cumulative effects of multiple stressors across different levels of biological complexity, revealing the underlying mechanisms and understanding how coastal ecosystems may respond to predicted scenarios of global change is critical to manage and protect our natural capital.
In this thesis, I advance multiple stressor research by applying complementary approaches to quantify the impact of multiple stressors on marine benthic resources and thereby help predict the consequences of expected climate change for coastal habitats. First, I present the newly developed experimental platform QIMS (Quantifying the Impacts of Multiple Stressors) that overcomes some of the shortfalls of previous multiple stressor research (Chapter 2). Second, in a novel empirical study, I investigate the independent and combined effects of moderate ocean warming and acidification on the functioning and production of mussels and algae, considering the effects of interspecific interactions in the presence or absence of the respective other species (Chapter 3). Third, I synthesise monitoring data from Dublin Bay (representative of a typical metropolitan estuary) using conditional interference and a Bayesian Network model and provide alternative system trajectories according to different climate change scenarios. From this new model, I deepen the understanding of the complex linkages between environmental conditions and the diversity and functioning of Dublin Bay to support local decision making and management (Chapter 4).
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Continue reading ‘Quantifying the impacts of multiple stressors on the production of marine benthic resources’Ocean acidification and food availability impacts on the metabolism and grazing in a cosmopolitan herbivorous protist Oxyrrhis marina
Published 8 March 2024 Science ClosedTags: abundance, biological response, growth, laboratory, multiple factors, North Pacific, nutrients, otherprocess, performance, physiology, primary production, protists, respiration, zooplankton
The heterotrophic dinoflagellate Oxyrrhis marina is an essential microzooplankton in coastal waters, linking the energy transfer from phytoplankton to higher trophic levels. It is of general significance to investigate how it responds and acclimates to ocean acidification (OA), especially under varied availabilities of food. Here, O. marina was exposed and acclimated to three pCO2 levels (LC: 415, MC:1000, HC:1500 μatm) for 60 days, and then was further grown under the CO2 levels with different levels of food (the microalgae Dunaliella salina) availability for about 8 generations. The OA treatments did not significantly hamper its growth and ingestion rates even under the reduced food availability and starvation (deprived of the microalgae), which significantly reduced its growth rate. While the impacts of OA on the growth and ingestion rates of O. marina were insignificant, the OA treatments appeared to have resulted in a faster decline of the heterotrophic dinoflagellate cells during the starvation period. Nevertheless, the acidic stress under the elevated pCO2 of 1000 or 1500 μatm decreased its respiration by about 53% or 59% with the high and by about 26% or 23% with the low food availability, respectively. Such OA-repressed respiration was also significant during the starvation period. On the other hand, the OA treatments and deprivation of the microalgae synergistically reduced the cellular quota of particulate organic C, N and P, resulting in a reduction of food value of the heterotrophic dinoflagellate as prey. In conclusion, our results show that O. marina is highly resilient to future ocean acidification by reducing its respiration and sustaining its ingestion of microalgae.
Continue reading ‘Ocean acidification and food availability impacts on the metabolism and grazing in a cosmopolitan herbivorous protist Oxyrrhis marina’Phosphorus deficiency regulates the growth and photophysiology responses of an economic macroalga Gracilariopsis lemaneiformis to ocean acidification and warming
Published 4 March 2024 Science ClosedTags: algae, biological response, growth, laboratory, multiple factors, North Pacific, nutrients, photosynthesis, physiology, temperature
Ocean acidification and warming caused by elevated CO2 are urgent problems facing the marine ecological environment. With the strengthening of environmental governance in China, anthropogenic inputs of terrestrial phosphorus into the coastal ocean have drastically decreased, resulting in frequent phosphorus deficiency in seawater. These environmental factors in the future may affect algal growth, photosynthesis and yield. As an important economic macroalga suitable for large-scale cultivation, Gracilariopsis lemaneiformis is also potentially affected by the coupling of ocean acidification, warming and phosphorus deficiency. In this study, G. lemaneiformis was cultured outdoors under two pCO2 levels (LC, 400 μatm; HC, 1000 μatm), two temperatures (LT, 20 ℃; HT, 24 ℃) and two phosphorus concentrations (LP, 0.1 μmol L−1; HP, 10 μmol L−1) to investigate its growth and photosynthetic performance. The results showed that LP significantly decreased the relative growth rates (RGR) and the maximum photosynthesis rate (Pm) of G. lemaneiformis both under LC and HC conditions. Under P depletion condition, the effects of warming and ocean acidification on the growth and photosynthetic performance of G. lemaneiformis showed an opposite trend, that is, HC caused a decrease in the growth, Pm, maximum relative electron transfer rate (rETRmax) and light utilization efficiency (α) from the rapid light response curve of G. lemaneiformis, and HT improved these parameters. Under LP condition, HC significantly inhibited the RGR of G. lemaneiformis in the LT group but had no significant effect on RGR in the HT group. Additionally, under LP condition, HC insignificantly affected PE and PC contents in the LT group, but significantly reduced these contents in the HT group. These findings suggest that phosphorus deficiency results in a decline in the growth of G. lemaneiformis and, under LP condition, the inhibition effect of ocean acidification on the growth of G. lemaneiformis could be mitigated by warming. This study provides scientific guidance for the field cultivation and selective breeding of G. lemaneiformis in phosphorus-deficient seawater under global climate change.
Continue reading ‘Phosphorus deficiency regulates the growth and photophysiology responses of an economic macroalga Gracilariopsis lemaneiformis to ocean acidification and warming’The impact of extreme weather events exceeds those due to global-change drivers on coastal phytoplankton assemblages
Published 1 March 2024 Science ClosedTags: abundance, biological response, BRcommunity, community composition, flow, laboratory, light, multiple factors, nutrients, otherprocess, photosynthesis, phytoplankton, South Atlantic, temperature
Highlights
- Extreme wind and rainfall events have become frequent phenomena in coastal ecosystems.
- We simulated these events under global change for five phytoplankton assemblages.
- Extreme events were responsible for the bulk of variability on photosynthesis efficiency.
- The impact of extreme events is low in assemblages with high diversity and evenness
- Extreme events should be considered in global change studies.
Abstract
Extreme wind and rainfall events have become more frequent phenomena, impacting coastal ecosystems by inducing increased mixing regimes in the upper mixed layers (UML) and reduced transparency (i.e. browning), hence affecting phytoplankton photosynthesis. In this study, five plankton assemblages from the South Atlantic Ocean, from a gradient of environmental variability and anthropogenic exposure, were subjected to simulated extreme weather events under a global change scenario (GCS) of increased temperature and nutrients and decreased pH, and compared to ambient conditions (Control). Using multiple linear regression (MLR) analysis we determined that evenness and the ratio of diatoms/ (flagellates + dinoflagellates) significantly explained the variations (81–91 %) of the photosynthesis efficiency (i.e. Pchla/ETRchla ratio) for each site under static conditions. Mixing speed and the optical depth (i.e. attenuation coefficient * depth, kdz), as single drivers, explained 40–76 % of the variability in the Pchla/ETRchla ratio, while GCS drivers <9 %. Overall, assemblages with high diversity and evenness were less vulnerable to extreme weather events under a GCS. Extreme weather events should be considered in global change studies and conservation/management plans as even at local/regional scales, they can exceed the predicted impacts of mean global climate change on coastal primary productivity.
Continue reading ‘The impact of extreme weather events exceeds those due to global-change drivers on coastal phytoplankton assemblages’Ocean acidification alters shellfish-algae nutritional value and delivery
Published 1 March 2024 Science ClosedTags: biological response, BRcommunity, growth, laboratory, mollusks, morphology, multiple factors, North Pacific, nutrients, photosynthesis, physiology, phytoplankton
Highlights
- Ocean acidification promotes microalgae growth.
- The nutrient value of microalgae is positively altered under acidifying conditions.
- Nutrient changes in primary producers can have indirect effects through trophic transfer.
- Fatty acid content of food sources affects shellfish macromolecular ratios.
Abstract
The ecological effects of climate change and ocean acidification (OA) have been extensively studied. Various microalgae are ecologically important in the overall pelagic food web as key contributors to oceanic primary productivity. Additionally, no organism exists in isolation in a complex environment, and shifts in food quality may lead to indirect OA effects on consumers. This study aims to investigate the potential effects of OA on algal trophic composition and subsequent bivalve growth. Here, the growth and nutrient fractions of Chlorella sp., Phaeodactylum tricornutum and Chaetocetos muelleri were used to synthesize and assess the impact of OA on primary productivity. Total protein content, total phenolic compounds, and amino acid (AA) and fatty acid (FA) content were evaluated as nutritional indicators. The results demonstrated that the three microalgae responded positively to OA in the future environment, significantly enhancing growth performance and nutritional value as a food source. Additionally, certain macromolecular fractions found in consumers are closely linked to their dietary sources, such as phenylalanine, C14:0, C16:0, C16:1, C20:1n9, C18:0, and C18:3n. Our findings illustrate that OA affects a wide range of crucial primary producers in the oceans, which can disrupt nutrient delivery and have profound impacts on the entire marine ecosystem and human food health.
Continue reading ‘Ocean acidification alters shellfish-algae nutritional value and delivery’High nutrient availability modulates photosynthetic performance and biochemical components of the economically important marine macroalga Kappaphycus alvarezii (Rhodophyta) in response to ocean acidification
Published 24 January 2024 Science ClosedTags: algae, biological response, laboratory, multiple factors, North Pacific, nutrients, photosynthesis, physiology
Increased atmospheric CO2 concentrations not only change the components of inorganic carbon system in seawater, resulting in ocean acidification, but also lead to decreased seawater pH, resulting in ocean acidification. Consequently, increased inorganic carbon concentrations in seawater provide a sufficient carbon source for macroalgal photosynthesis and growth. Increased domestic sewage and industrial wastewater discharge into coastal areas has led to nutrient accumulation in coastal seawaters. Combined with elevated pCO2 (1200 ppmv), increased nutrient availability always stimulates the growth of non-calcifying macroalgae, such as red economical macroalga Gracilariopsis lemaneiformis. Here, we evaluated the interactive effects of nutrients with elevated pCO2 on the economically important marine macroalga Kappaphycus alvarezii (Rhodophyta) in a factorial 21-day coupling experiment. The effects of increased nutrient availability on photosynthesis and photosynthetic pigments of K. alvarezii were greater than those of pCO2 concentration. The highest Fv/Fm values (0.660 ± 0.019 and 0.666 ± 0.030, respectively) were obtained at 2 μmol L−1 of NO3–N at two pCO2 levels. Under the elevated pCO2 condition, the Chl-a content was lowest (0.007 ± 0.004 mg g−1) at 2 μmol L−1 of NO3–N and highest (0.024 ± 0.002 mg g−1) at 50 μmol L−1 of NO3–N. The phycocyanin content was highest (0.052 ± 0.012 mg g−1) at 150 μmol L−1 of NO3–N under elevated pCO2 condition. The malondialdehyde content declined from 32.025 ± 4.558 nmol g−1 to 26.660 ± 3.124 nmol g−1 with the increased nutrients at under low pCO2. To modulate suitable adjustments, soluble biochemical components such as soluble carbohydrate, soluble protein, free amino acids, and proline were abundantly secreted and were likely to protect the integrity of cellular structures under elevated nutrient availability. Our findings can serve as a reference for cultivation and bioremediation methods under future environmental conditions.
Continue reading ‘High nutrient availability modulates photosynthetic performance and biochemical components of the economically important marine macroalga Kappaphycus alvarezii (Rhodophyta) in response to ocean acidification’Survival of nutrient-starved diatoms under ocean acidification: perspective from nutrient sensing, cadmium detection, and nitrogen assimilation
Published 15 January 2024 Science ClosedTags: abundance, biological response, BRcommunity, laboratory, multiple factors, North Pacific, nutrients, otherprocess, physiology, phytoplankton
Increased anthropogenic emissions of carbon dioxide (CO2) have resulted in ocean acidification (OA) that is intertwined with enhanced ocean stratification. Diatoms are assumed to suffer from a more nutrient-limited condition in the future ocean. This study aimed to explore how OA affects the diatom dynamics under nutrient-poor conditions and the ability of diatoms to perceive nutrients (nitrogen, phosphorus, silicon, and trace metals) and cadmium (Cd) stimuli and assimilate nitrogen when receiving nutrients or Cd supplementation. Our study observed that diatom population grown under OA condition declined faster than those grown under ambient condition. Ocean acidification greatly lower intracellular Ca2+ concentration in diatom cells. Intracellular Ca2+ burst was involved in phosphorus accumulation but not in nitrogen, silicon, essential metals, and cadmium uptake. Our data demonstrate slower NO3– assimilation rates of diatoms grown in acidified seawater. Our study also indicates that diatoms have a poor perception of phosphorus availability under OA condition.
Continue reading ‘Survival of nutrient-starved diatoms under ocean acidification: perspective from nutrient sensing, cadmium detection, and nitrogen assimilation’Higher temperature, increased CO2, and changing nutrient ratios alter the carbon metabolism and induce oxidative stress in a cosmopolitan diatom
Published 8 December 2023 Science ClosedTags: biological response, growth, laboratory, multiple factors, North Atlantic, nutrients, photosynthesis, physiology, phytoplankton, primary production, respiration, temperature
Phytoplankton are responsible for about 90% of the oceanic primary production, largely supporting marine food webs, and actively contributing to the biogeochemical cycling of carbon. Yet, increasing temperature and pCO2, along with higher dissolved nitrogen: phosphorus ratios in coastal waters are likely to impact phytoplankton physiology, especially in terms of photosynthetic rate, respiration, and dissolved organic carbon (DOC) production. Here, we conducted a full-factorial experiment to identify the individual and combined effects of temperature, pCO2, and N : P ratio on the antioxidant capacity and carbon metabolism of the diatom Phaeodactylum tricornutum. Our results demonstrate that, among these three drivers, temperature is the most influential factor on the physiology of this species, with warming causing oxidative stress and lower activity of antioxidant enzymes. Furthermore, the photosynthetic rate was higher under warmer conditions and higher pCO2, and, together with a lower dark respiration rate and higher DOC exudation, generated cells with lower carbon content. An enhanced oceanic CO2 uptake and an overall stimulated microbial loop benefiting from higher DOC exudation are potential longer-term consequences of rising temperatures, elevated pCO2 as well as shifted dissolved N : P ratios.
Continue reading ‘Higher temperature, increased CO2, and changing nutrient ratios alter the carbon metabolism and induce oxidative stress in a cosmopolitan diatom’Atlantic-origin water extension into the Pacific Arctic induced an anomalous biogeochemical event
Published 15 November 2023 Science ClosedTags: Arctic, biogeochemistry, chemistry, field, fisheries, modeling, multiple factors, nutrients, oxygen, policy, regionalmodeling, salinity
The Arctic Ocean is facing dramatic environmental and ecosystem changes. In this context, an international multiship survey project was undertaken in 2020 to obtain current baseline data. During the survey, unusually low dissolved oxygen and acidified water were found in a high-seas fishable area of the western (Pacific-side) Arctic Ocean. Herein, we show that the Beaufort Gyre shrinks to the east of an ocean ridge and forms a front between the water within the gyre and the water from the eastern (Atlantic-side) Arctic. That phenomenon triggers a frontal northward flow along the ocean ridge. This flow likely transports the low oxygen and acidified water toward the high-seas fishable area; similar biogeochemical properties had previously been observed only on the shelf-slope north of the East Siberian Sea.
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Fig. 1: Schematic of the Arctic Ocean circulation and the study area with hydrographic stations.
a, b Maps of the Arctic Ocean and the study area. In a, yellow, blue, and red arrows represent flows from the shelf-slope at the north of the East Siberian Sea (ESS), and from the Pacific and Atlantic oceans in 2017–2020. Ocean circulation and water masses are abbreviated as follows: Beaufort Gyre (BG), Transpolar Drift (TPD), Pacific Water (PW), Lower Halocline Water (LHW), and Atlantic Water (AW). Geographical locations are abbreviated as follows: Canada Basin (CB), Chukchi Plateau (CP), Mendeleyev Ridge (MR), Makarov Basin (MB), and Lomonosov Ridge (LR). In b red, green, and blue dots denote the hydrographic stations conducted by the Research Vessel (R/V) Araon (Korea), R/V Mirai (Japan), and Canadian Coast Guard Ship Louis S. St-Laurent (Canada), under the 2020 Synoptic Arctic Survey project. Black dots indicate other hydrographic stations between 2002 and 2019 listed in Supplementary Table 1.
Continue reading ‘Atlantic-origin water extension into the Pacific Arctic induced an anomalous biogeochemical event’CO2 enrichment and excess nitrogen supply synergistically increase toxicity of marine dinoflagellate Alexandrium minutum
Published 2 November 2023 Science ClosedTags: abundance, biological response, laboratory, multiple factors, North Pacific, nutrients, otherprocess, physiology, phytoplankton
Discharges of CO2 and nutrients by anthropogenic activities have notable contributions to CO2 enrichment and eutrophication in coastal systems. Following our previous study that toxic dinoflagellate Alexandrium minutum will increase their growth rate and cellular toxicity under elevated levels of CO2, we further examined the joint effects of CO2 enrichment and excess nitrogen supply through a 29-day experiment under three CO2 levels (400, 800 and 1200 ppm) with a high N/P ratio of 80. It was found that the two factors have synergistical effects in promoting the increase of cellular toxicity. There were remarkable increases in toxin biosynthesis of paralytic shellfish toxins when both intracellular and extracellular toxins were considered. Under the joint impacts of CO2 enrichment and excess nitrogen supply, the apparent transformation from gonyautoxins2/3 to gonyautoxins1/4, with much higher toxicity and lower rate of release, is likely to be another major factor accounting for the increasing toxicity. The increasing growth rate and cellular toxicity of A. minutum under the scenarios with elevated concentrations of both CO2 and nitrogen in coastal systems in the future will increase the risks associated with such toxic algal blooms.
Continue reading ‘CO2 enrichment and excess nitrogen supply synergistically increase toxicity of marine dinoflagellate Alexandrium minutum’Species-dependent effects of seawater acidification on alkaline phosphatase activity in dinoflagellates (update)
Published 23 October 2023 Science ClosedTags: abundance, biological response, laboratory, molecular biology, multiple factors, nutrients, otherprocess, physiology, phytoplankton
Increases of atmospheric CO2 cause ocean acidification (OA) and global warming, the latter of which can stratify the water column and impede nutrient supply from deep water. Phosphorus (P) is an essential nutrient for phytoplankton to grow. While dissolved inorganic phosphorus (DIP) is the preferred form of P, phytoplankton have evolved alkaline phosphatase (AP) to utilize dissolved organic phosphorus (DOP) when DIP is deficient. Although the function of AP is known to require pH > 7, how OA affects AP activity and hence the capacity of phytoplankton to utilize DOP is poorly understood. Here, we examined the effects of pH conditions (5.5–11) on AP activity from six species of dinoflagellates, an important group of marine phytoplankton. We observed a general pattern that AP activity declined sharply at pH 5.5, peaked between pH 7 and 8, and dropped at pH > 8. However, our data revealed remarkable interspecific variations in optimal pH and niche breadth of pH. Among the species examined, Fugacium kawagutii and Prorocentrum cordatum had an optimal pH at 8, and Alexandrium pacificum, Amphidinium carterae, Effrenium voratum, and Karenia mikimotoi showed an optimal pH of 7. However, whereas A. pacificum and K. mikimotoi had the broadest pH niche for AP (7–10) and F. kawagutii the second (8–10), Am. carterae, E. voratum, and P. cordatum exhibited a narrow pH range. The response of Am. carterae AP to pH changes was verified using purified AP heterologously expressed in Escherichia coli. These results in concert suggest OA will likely differentially impact the capacity of different phytoplankton species to utilize DOP in the projected more acidified and nutrient-limited future ocean.
Continue reading ‘Species-dependent effects of seawater acidification on alkaline phosphatase activity in dinoflagellates (update)’Experimental ocean acidification and food limitation reveals altered energy budgets and synergistic effects on mortality of larvae of a coastal fish
Published 31 August 2023 Science ClosedTags: biological response, fish, laboratory, morphology, mortality, multiple factors, North Pacific, nutrients, performance, physiology
Ocean acidification (OA) presents a unique challenge to early life stages of marine species. Developing organisms must balance the need to grow rapidly with the energetic demands of maintaining homeostasis. The small sizes of early life stages can make them highly sensitive to changes in environmental CO2 levels, but studies have found wide variation in responses to OA. Thus far most OA studies have manipulated CO2 only, and modifying factors need to be considered in greater detail. We investigated the effects of high pCO2 and food ration on rates of growth and mortality of a coastal fish, the California Grunion (Leuresthes tenuis). We also examined how CO2 and food levels affected feeding success, metabolic rate, and swimming activity – processes reflective of energy acquisition and expenditure. In general, exposure to high CO2 decreased energy intake by reducing feeding success, and increased energy expenditure by increasing metabolic rate and routine swimming speed, though the magnitudes of these effects varied somewhat with age. Despite these changes in energetics, growth of biomass was not affected significantly by pCO2 level but was reduced by low ration level, and we did not detect an interactive effect of food ration and pCO2 on growth. However, under OA conditions, larvae were in poorer condition (as evaluated by the mass to length ratio) by the end of the experiment and our analysis of mortality revealed a significant interaction in which the effects of OA were more lethal when food energy was limited. These results are consistent with the idea that although energy can be reallocated to preserve biomass growth, increased energetic demand under ocean acidification may draw energy away from maintenance, including those processes that foster homeostasis during development. Overall, these results highlight both the need to consider the availability of food energy as a force governing species’ responses to ocean acidification and the need to explicitly consider the energy allocated to both growth and maintenance as climate changes.
Continue reading ‘Experimental ocean acidification and food limitation reveals altered energy budgets and synergistic effects on mortality of larvae of a coastal fish’Ontogenetic differences in the response of the cold-water coral Caryophyllia huinayensis to ocean acidification, warming and food availability
Published 1 August 2023 Science ClosedTags: biological response, calcification, corals, laboratory, morphology, mortality, multiple factors, nutrients, performance, respiration, South Pacific, temperature
Highlights
- Response to multiple stressors differs between cold-water coral life stages.
- Elevated temperature and reduced feeding have the strongest effect.
- Highest mortality occurs in adult corals.
- Calcification rates decrease the most in juvenile corals.
- Three-month delay in response to changing environmental conditions.
Abstract
Cold-water corals (CWCs) are considered vulnerable to environmental changes. However, previous studies have focused on adult CWCs and mainly investigated the short-term effects of single stressors. So far, the effects of environmental changes on different CWC life stages are unknown, both for single and multiple stressors and over long time periods. Therefore, we conducted a six-month aquarium experiment with three life stages of Caryophyllia huinayensis to study their physiological response (survival, somatic growth, calcification and respiration) to the interactive effects of aragonite saturation (0.8 and 2.5), temperature (11 and 15 °C) and food availability (8 and 87 μg C L−1). The response clearly differed between life stages and measured traits. Elevated temperature and reduced feeding had the greatest effects, pushing the corals to their physiological limits. Highest mortality was observed in adult corals, while calcification rates decreased the most in juveniles. We observed a three-month delay in response, presumably because energy reserves declined, suggesting that short-term experiments overestimate coral resilience. Elevated summer temperatures and reduced food supply are likely to have the greatest impact on live CWCs in the future, leading to reduced coral growth and population shifts due to delayed juvenile maturation and high adult mortality.
Continue reading ‘Ontogenetic differences in the response of the cold-water coral Caryophyllia huinayensis to ocean acidification, warming and food availability’Effects of climate change and eutrophication on photosynthesis and carbon-concentrating mechanisms: surprising diversity among reef algae
Published 19 July 2023 Science ClosedTags: algae, biological response, chemistry, growth, laboratory, multiple factors, North Pacific, nutrients, photosynthesis, physiology, primary production
Increased anthropogenic CO2 emission since the start of the Industrial Revolution has brought a changing climate and various threats to coastal ecosystems including ocean warming, ocean acidification (OA), and sea level rise. Coral reef ecosystems are especially vulnerable to the climate change, because ocean warming and acidification decrease calcification and increase bleaching in coral. In addition to these impacts of climate change, coastal ecosystems are already experiencing local anthropogenic impacts such as chronic eutrophication and continuing arrival of new invasive species. In Hawai‘i, large-scale blooms of both native and invasive macroalgae are often observed in the region with coastal eutrophication by land-based anthropogenic nutrient input. Predicting the effects of OA (increased CO2 concentration in the ocean) on algae is not straightforward because many algae are already equipped with carbon-concentrating mechanisms (CCMs) with which algae can increase their internal CO2 concentration for photosynthesis. Further, nutrient availability especially that of the macronutrient, nitrogen (N) could alter the operation of algal CCMs because CCMs involve specific, large proteins such as ribulose-1,5-biphosphate carboxylase-oxygenase (RUBISCO) and carbonic anhydrases (CA). This study experimentally investigated how OA and eutrophication, independently and synergistically, affect photosynthesis and CCMs in common Hawaiian reef algae. Algae can quickly change their maximum photosynthetic rates and CCMs when grown under elevated CO2 and N. Further, we found a surprising diversity among reef algae in how they react to elevated CO2 and N with their CCMs. The results of this study suggest that many Hawaiian algae will thrive under future climate change conditions, and OA and eutrophication will likely work in their favor, accelerating the phase shift from coral-dominated to macroalgal-dominated reefs in unpredictably faster paces and with players that are not easily predicted.
Continue reading ‘Effects of climate change and eutrophication on photosynthesis and carbon-concentrating mechanisms: surprising diversity among reef algae’Combined effects of ocean deoxygenation, acidification, and phosphorus limitation on green tide macroalga, Ulva prolifera
Published 29 June 2023 Science ClosedTags: algae, biogeochemistry, biological response, growth, laboratory, multiple factors, North Pacific, nutrients, oxygen, photosynthesis, physiology
Highlights
- Additive and antagonistic interactions between the three stressors were mainly observed.
- Ocean deoxygenation, acidification, and P limitation can dysregulate the Ulva prolifera of photosynthetic efficiency.
- Green tide macroalgal Ulva prolifera has a strong acclimation capacity to elevated CO2, low O2, and high N/P.
- Ulva prolifera could use organic P to support its growth under low inorganic phosphorus conditions.
- Increased CO2 levels can decrease the energy costs associated with CCM, and can support the growth of macroalgal cells.
Abstract
Ocean deoxygenation, acidification, and decreased phosphorus availability are predicted to increase in coastal ecosystems under future climate change. However, little is known regarding the combined effects of such environmental variables on the green tide macroalga Ulva prolifera. Here, we provide quantitative and mechanistic understanding of the acclimation mechanisms of U. prolifera to ocean deoxygenation, acidification, and phosphorus limitation under both laboratory and semi-natural (mesocosms) conditions. We found that there were significant interactions between these global environmental conditions on algal physiological performance. Although algal growth rate and photosynthesis reduced when the nitrogen-to‑phosphorus (N/P) ratio increased from 16:1 to 35:1 under ambient CO2 and O2 condition, they remained constant with further increasing N/P ratios of 105:1, 350:1, and 1050:1. However, the increasing alkaline phosphatase activities at high N/P ratios suggests that U. prolifera could use organic P to support its growth under phosphorus limitation. Deoxygenation had no effect on specific growth rate (SGR) but decreased photosynthesis under low N/P ratios of 16:1, 35:1, and 105:1, with reduced activities of several enzymes involved in N assimilation pathway being observed. Elevated CO2 promoted algal growth and alleviated the negative effect of deoxygenation on algal photosynthesis. The patterns of responses to high CO2 and low O2 treatments in in situ experiments were generally consistent with those observed in laboratory experiments. Our results generally found that the strong physiological acclimation capacity to elevated CO2, low O2, and high N/P could contribute to its large-scale blooming in coastal ecosystem.
Continue reading ‘Combined effects of ocean deoxygenation, acidification, and phosphorus limitation on green tide macroalga, Ulva prolifera’Simulated upwelling and marine heatwave events promote similar growth rates but differential domoic acid toxicity in Pseudo-nitzschia australis
Published 28 June 2023 Science ClosedTags: abundance, biogeochemistry, biological response, laboratory, multiple factors, North Pacific, nutrients, otherprocess, physiology, phytoplankton, temperature
Along the west coast of the United States, highly toxic Pseudo-nitzschia blooms have been associated with two contrasting regional phenomena: seasonal upwelling and marine heatwaves. While upwelling delivers cool water rich in pCO2 and an abundance of macronutrients to the upper water column, marine heatwaves instead lead to warmer surface waters, low pCO2, and reduced nutrient availability. Understanding Pseudo-nitzschia dynamics under these two conditions is important for bloom forecasting and coastal management, yet the mechanisms driving toxic bloom formation during contrasting upwelling vs. heatwave conditions remain poorly understood. To gain a better understanding of what drives Pseudo-nitzschia australis growth and toxicity during these events, multiple-driver scenario or ‘cluster’ experiments were conducted using temperature, pCO2, and nutrient levels reflecting conditions during upwelling (13 °C, 900 ppm pCO2, replete nutrients) and two intensities of marine heatwaves (19 °C or 20.5 °C, 250 ppm pCO2, reduced macronutrients). While P. australis grew equally well under both heatwave and upwelling conditions, similar to what has been observed in the natural environment, cells were only toxic in the upwelling treatment. We also conducted single-driver experiments to gain a mechanistic understanding of which drivers most impact P. australis growth and toxicity. These experiments indicated that nitrogen concentration and N:P ratio were likely the drivers that most influenced domoic acid production, while the impacts of temperature or pCO2 concentration were less pronounced. Together, these experiments may help to provide both mechanistic and holistic perspectives on toxic P. australis blooms in the dynamic and changing coastal ocean, where cells interact simultaneously with multiple altered environmental variables.
Continue reading ‘Simulated upwelling and marine heatwave events promote similar growth rates but differential domoic acid toxicity in Pseudo-nitzschia australis’Growth performance, antioxidant indexes, and the expression of genes were considerably promoted by dietary supplementation of alanyl-glutamine and vitamin E in juvenile marine medaka in seawater acidification by carbon dioxide
Published 26 June 2023 Science ClosedTags: biological response, fish, growth, laboratory, molecular biology, morphology, mortality, multiple factors, North Pacific, nutrients, physiology
The experiment was conducted to study the effect of different dietary supplementation of alanyl-glutamine dipeptide (AGD) and/or vitamin E (VE) on the growth performance, antioxidant indexes, and the expression of glutathione peroxidase (GPx) and peroxisome proliferator-activated receptor α (PPARⱭ) genes in juvenile marine medaka (Oryzias melastigma) in seawater acidification. Seven groups of juvenile marine medaka in triplicate were studied in an ecosystem. One of them was in normal seawater (pH 8.1, pH control), and the others were in seawater acidification (pH 7.7) regulated by carbon dioxide (CO2). The juveniles were separately fed for 10 weeks using one of six different diets. The six diets were one control diet (basic feed) without supplements and the other diets with different amounts of additional AGD and/or VE. The juveniles were sampled randomly for analysis of a whole fish in week 0 and week 10. The results showed that different dietary supplementation of AGD and/or VE could considerably promote the growth performance, antioxidant indexes, and the expression of GPx and PPARα genes of juvenile marine medaka in seawater acidification. The optimal diet was D4, with additional AGD 5 g and VE 50 IU per kg of dried feed.
Continue reading ‘Growth performance, antioxidant indexes, and the expression of genes were considerably promoted by dietary supplementation of alanyl-glutamine and vitamin E in juvenile marine medaka in seawater acidification by carbon dioxide’
