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’Posts Tagged 'growth'
Interaction of CO2 and light availability on photophysiology of tropical coccolithophorids (Emiliania huxleyi, Gephyrocapsa oceanica, and Ochosphaera sp.)
Published 28 February 2023 Science ClosedTags: biological response, calcification, growth, laboratory, light, morphology, multiple factors, photosynthesis, physiology, phytoplankton
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
Published 22 February 2023 Science ClosedTags: biological response, growth, laboratory, metals, molecular biology, multiple factors, photosynthesis, physiology, phytoplankton, toxicants
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’Morphology and stable isotope ecology of Pleuroncodes planipes adult life stages and their vulnerability to climate change stressors
Published 16 February 2023 Science ClosedTags: biological response, crustaceans, growth, morphology, multiple factors, temperature
Like many in Southern California during the 2015/16 El Niño event, I was struck by the presence of thousands of bright red tuna crabs (Pleuroncodes planipes) abundant at sea and washing ashore. Their sudden prevalence inspired me to learn more about these fascinating animals. Despite drawing so much attention, basic details related to their feeding behaviors and life history remain unknown. P. planipes have long been thought, but never confirmed, to experience a unique life history among crustaceans during which they undergo a sequential habitat shift from pelagic to benthic as adults. In this dissertation research, I applied contemporary methods of stable isotope ecology in combination with ecomorphology to examine aspects of their life history relevant to their pelagic and benthic life stages. We further assessed their vulnerability to the climate change stressors of ocean acidification and ocean warming through a long-term experiment. Through this work, we uncovered morphological differences and an ontogenetic diet shift between pelagic and benthic adult stages as well as significant impacts of temperature, but not pCO2/pH on molting and growth in pelagic adults. These results provide the first evidence in support of the hypothesis that P. planipes adult pelagic and benthic stages are distinct and yield important insight into how this transition could be impacted as the oceans continue to change.
Continue reading ‘Morphology and stable isotope ecology of Pleuroncodes planipes adult life stages and their vulnerability to climate change stressors’Life-stage-dependent effects of multiple flood-associated stressors on a coastal foundational species
Published 15 February 2023 Science ClosedTags: biological response, growth, laboratory, mollusks, morphology, mortality, multiple factors, oxygen, reproduction, salinity
Global changes in precipitation patterns have increased the frequency and duration of flooding events. Freshwater inflows into estuaries reduce salinity levels and increase nutrient inputs, which can lead to eutrophication and impaired water quality. Oysters are important ecosystem engineers in coastal environments that are vulnerable to co-occurring environmental stressors associated with freshwater flooding events. Successful recruitment is necessary to maintain adult oyster populations, but early life stage responses to multiple stressors are not well understood. Flood-associated stressor conditions were observed near oyster habitats at multiple locations across the northern Gulf of Mexico during peak recruitment months in the spring and summer of 2021. In the laboratory, we examined the interactive effects of acidification, hypoxia, and low salinity on larval and juvenile life stages of the eastern oyster (Crassostrea virginica) to better understand the impact of flooding events on oyster development and survival. Salinity stress in isolation reduced larval growth and settlement, and decreased survival and growth at the juvenile stage. Hypoxia was more stressful to oyster larvae than to juveniles, whereas low pH had negative effects on juvenile growth. There were no synergistic effects of multiple flood-associated stressors on early oyster life stages and effects were either additive or predicted by the salinity stress response. The negative impacts of flooding disturbances on recruitment processes in benthic populations need to be considered in restoration planning and flood control mitigation strategies as the frequency and intensity of extreme freshwater events continue to rise worldwide.
Continue reading ‘Life-stage-dependent effects of multiple flood-associated stressors on a coastal foundational species’Plastic responses lead to increased neurotoxin production in the diatom Pseudo-nitzschia under ocean warming and acidification
Published 14 February 2023 Science ClosedTags: biological response, growth, laboratory, molecular biology, multiple factors, phytoplankton, temperature
Ocean warming (OW) and acidification (OA) are recognized as two major climatic conditions influencing phytoplankton growth and nutritional or toxin content. However, there is limited knowledge on the responses of harmful algal bloom species that produce toxins. Here, the study provides quantitative and mechanistic understanding of the acclimation and adaptation responses of the domoic acid (DA) producing diatom Pseudo-nitzschia multiseries to rising temperature and pCO2 using both a one-year in situ bulk culture experiment, and an 800-day laboratory acclimation experiment. Ocean warming showed larger selective effects on growth and DA metabolism than ocean acidification. In a bulk culture experiment, increasing temperature +4 °C above ambient seawater temperature significantly increased DA concentration by up to 11-fold. In laboratory when the long-term warming acclimated samples were assayed under low temperatures, changes in growth rates and DA concentrations indicated that P. multiseries did not adapt to elevated temperature, but could instead rapidly and reversibly acclimate to temperature shifts. However, the warming-acclimated lines showed evidence of adaptation to elevated temperatures in the transcriptome data. Here the core gene expression was not reversed when warming-acclimated lines were moved back to the low temperature environment, which suggested that P. multiseries cells might adapt to rising temperature over longer timescales. The distinct strategies of phenotypic plasticity to rising temperature and pCO2 demonstrate a strong acclimation capacity for this bloom-forming toxic diatom in the future ocean.
Continue reading ‘Plastic responses lead to increased neurotoxin production in the diatom Pseudo-nitzschia under ocean warming and acidification’Potential effects of climate change on the growth response of the toxic dinoflagellate Karenia selliformis from Patagonian waters of Chile
Published 6 February 2023 Science ClosedTags: abundance, biological response, growth, laboratory, multiple factors, otherprocess, phytoplankton, South Pacific, temperature
Northern Patagonia (41–44°S) is affected by climatic, hydrological and oceanographic anomalies, which in synergy with processes such as global warming and acidification of the coastal oceans may affect the frequency and intensity of harmful algal blooms (HABs). Greater frequency of HABs has been reported in the southeastern Pacific Ocean, including blooms of the toxic dinoflagellate Karenia selliformis, causing massive mortality of marine fauna in the oceanic and coastal areas of Patagonia. The objective of this study was to determine the effects of temperature and pH interaction on the growth of K. selliformis (strain CREAN_KS02), since these factors have wide seasonal fluctuations in the Patagonian fjord ecosystem. The CREAN_KS02 strain isolated from the Aysén Region (43°S) was used in a factorial experiment with five pH levels (7.0, 7.4, 7.7, 8.1 and 9.0) and two temperatures (12 and 17 °C) during a period of 18–21 days. Results indicated a significant effect of temperature and pH interaction on growth rate (range 0.22 ± 0.00 to 0.08 ± 0.01 d−1) and maximum density (range 13,710 ± 2,616 to 2,385 ± 809 cells mL−1) of K. selliformis. The highest density and growth of K. selliformis was found at 12 °C with a reduced pH (7.0–7.7). The results suggest that the current environmental conditions of coastal Patagonia, waters of low temperature and relatively low pH, may be favorable for the development of blooms of this species during autumn. We suggest that there is natural plasticity of K. selliformis in a wide pH range (7.0–8.1) but in a narrow low temperature range (10.6–12.9 °C), values that are typically recorded in the oceanic region of northern Patagonia. In contrast, in an extreme climate change scenario (ocean warming and coastal acidification) in northern Patagonia, a negative effect on the growth of K. selliformis may be expected due to amplification of the acidification effects caused by the thermal stress of high temperature water.
Continue reading ‘Potential effects of climate change on the growth response of the toxic dinoflagellate Karenia selliformis from Patagonian waters of Chile’Effects of global environmental change on microalgal photosynthesis, growth and their distribution
Published 6 February 2023 Science ClosedTags: biological response, growth, light, morphology, multiple factors, photosynthesis, physiology, phytoplankton, review, salinity, temperature
Global climate change (GCC) constitutes a complex challenge posing a serious threat to biodiversity and ecosystems in the next decades. There are several recent studies dealing with the potential effect of increased temperature, decrease of pH or shifts in salinity, as well as cascading events of GCC and their impact on human-environment systems. Microalgae as primary producers are a sensitive compartment of the marine ecosystems to all those changes. However, the potential consequences of these changes for marine microalgae have received relatively little attention and they are still not well understood. Thus, there is an urgent need to explore and understand the effects generated by multiple climatic changes on marine microalgae growth and biodiversity. Therefore, this review aimed to compare and contrast mechanisms that marine microalgae exhibit to directly respond to harsh conditions associated with GCC and the potential consequences of those changes in marine microalgal populations. Literature shows that microalgae responses to environmental stressors such as temperature were affected differently. A stress caused by salinity might slow down cell division, reduces size, ceases motility, and triggers palmelloid formation in microalgae community, but some of these changes are strongly species-specific. UV irradiance can potentially lead to an oxidative stress in microalgae, promoting the production of reactive oxygen species (ROS) or induce direct physical damage on microalgae, then inhibiting the growth of microalgae. Moreover, pH could impact many groups of microalgae being more tolerant of certain pH shifts, while others were sensitive to changes of just small units (such as coccolithophorids) and subsequently affect the species at a higher trophic level, but also total vertical carbon transport in oceans. Overall, this review highlights the importance of examining effects of multiple stressors, considering multiple responses to understand the complexity behind stressor interactions.
Continue reading ‘Effects of global environmental change on microalgal photosynthesis, growth and their distribution’No effect of ocean acidification on growth, photosynthesis, or dissolved organic carbon release by three temperate seaweeds with different dissolved inorganic carbon uptake strategies
Published 27 January 2023 Science ClosedTags: algae, biological response, BRcommunity, chemistry, growth, Indian, laboratory, morphology, multiple factors, nutrients, photosynthesis, physiology, respiration
In a future ocean, dissolved organic carbon (DOC) release by seaweed has been considered a pathway for organic carbon that is not incorporated into growth under carbon dioxide (CO2) enrichment/ocean acidification (OA). To understand the influence of OA on seaweed DOC release, a 21-day experiment compared the physiological responses of three seaweed species, two which operate CO2 concentrating mechanisms (CCMs), Ecklonia radiata (C. Agardh) J. Agardh and Lenormandia marginata (Hooker F. and Harvey) and one that only uses CO2 (non-CCM), Plocamium cirrhosum (Turner) M.J. Wynne. These two groups (CCM and non-CCM) are predicted to respond differently to OA dependent on their affinities for Ci (defined as CO2 + bicarbonate, HCO3−). Future ocean CO2 treatment did not drive changes to seaweed physiology—growth, Ci uptake, DOC production, photosynthesis, respiration, pigments, % tissue carbon, nitrogen, and C:N ratios—for any species, regardless of Ci uptake method. Our results further showed that Ci uptake method did not influence DOC release rates under OA. Our results show no benefit of elevated CO2 concentrations on the physiologies of the three species under OA and suggest that in a future ocean, photosynthetic CO2 fixation rates of these seaweeds will not increase with Ci concentration.
Continue reading ‘No effect of ocean acidification on growth, photosynthesis, or dissolved organic carbon release by three temperate seaweeds with different dissolved inorganic carbon uptake strategies’Ocean acidification and ammonium enrichment interact to stimulate a short-term spike in growth rate of a bloom forming macroalga
Published 10 January 2023 Science ClosedTags: algae, biological response, growth, laboratory, multiple factors, North Pacific, nutrients, photosynthesis, physiology
Introduction: The coastal macroalgal genus, Ulva, is found worldwide and is considered a nuisance algal genus due to its propensity for forming vast blooms. The response of Ulva to ocean acidification (OA) is of concern, particularly with nutrient enrichment, as these combined drivers may enhance algal blooms because of increased availability of dissolved inorganic resources.
Methods: We determined how a suite of physiological parameters were affected by OA and ammonium (NH4+) enrichment in 22-day laboratory experiments to gain a mechanistic understanding of growth, nutrient assimilation, and photosynthetic processes. We predicted how physiological parameters change across a range of pCO2 and NH4+ scenarios to ascertain bloom potential under future climate change regimes.
Results: During the first five days of growth, there was a positive synergy between pCO2 and NH4+ enrichment, which could accelerate initiation of an Ulva bloom. After day 5, growth rates declined overall and there was no effect of pCO2, NH4+, nor their interaction. pCO2 and NH4+ acted synergistically to increase NO3– uptake rates, which may have contributed to increased growth in the first five days. Under the saturating photosynthetically active radiation (PAR) used in this experiment (500 μmol photon m-2 s-1), maximum photosynthetic rates were negatively affected by increased pCO2, which could be due to increased sensitivity to light when high CO2 reduces energy requirements for inorganic carbon acquisition. Activity of CCMs decreased under high pCO2 and high NH4+ conditions indicating that nutrients play a role in alleviating photodamage and regulating CCMs under high-light intensities.
Discussion: This study demonstrates that OA could play a role in initiating or enhancing Ulva blooms in a eutrophic environment and highlights the need for understanding the potential interactions among light, OA, and nutrient enrichment in regulating photosynthetic processes.
Continue reading ‘Ocean acidification and ammonium enrichment interact to stimulate a short-term spike in growth rate of a bloom forming macroalga’Effects of seawater acidification and solar ultraviolet radiation on photosynthetic performances and biochemical compositions of Rhodosorus sp. SCSIO-45730
Published 6 January 2023 Science ClosedTags: algae, biological response, growth, laboratory, light, multiple factors, North Pacific, photosynthesis, physiology
Ocean acidification (OA) caused by rising atmospheric CO2 concentration and solar ultraviolet radiation (UVR) resulting from ozone depletion may affect marine organisms, but little is known regarding how unicellular Rhodosorus sp. SCSIO-45730, an excellent species resource containing various biological-active compounds, responds to OA and UVR. Therefore, we conducted a factorial coupling experiment to unravel the combined effects of OA and UVR on the growth, photosynthetic performances, biochemical compositions and enzyme activities of Rhodosorus sp. SCSIO-45730, which were exposed to two levels of CO2 (LC, 400 μatm, current CO2 level; HC, 1000 μatm, future CO2 level) and three levels of UVR (photosynthetically active radiation (PAR), PAR plus UVA, PAR plus UVB) treatments in all combinations, respectively. Compared to LC treatment, HC stimulated the relative growth rate (RGR) due to higher optimum and effective quantum yields, photosynthetic efficiency, maximum electron transport rates and photosynthetic pigments contents regardless of UVR. However, the presence of UVA had no significant effect but UVB markedly reduced the RGR. Additionally, higher carbohydrate content and lower protein and lipid contents were observed when Rhodosorus sp. SCSIO-45730 was cultured under HC due to the ample HCO−3HCO3− applications and active stimulation of metabolic enzymes of carbonic anhydrase and nitrate reductase, thus resulting in higher TC/TN. OA also triggered the production of reactive oxygen species (ROS), and the increase of ROS coincided approximately with superoxide dismutase and catalase activities, as well as phenols contents. However, UVR induced photochemical inhibition and damaged macromolecules, making algal cells need more energy for self-protection. Generally, these results revealed that OA counteracted UVR-related inhibition on Rhodosorus sp. SCSIO-45730, adding our understanding of the red algae responding to future global climate changes.
Continue reading ‘Effects of seawater acidification and solar ultraviolet radiation on photosynthetic performances and biochemical compositions of Rhodosorus sp. SCSIO-45730’Implications of salinity and acidic environments on fitness and oxidative stress parameters in early developing seahorses Hippocampus reidi
Published 19 December 2022 Science ClosedTags: biological response, fish, growth, laboratory, morphology, mortality, multiple factors, performance, physiology, reproduction, salinity
Simple Summary
The main aim of the present study was to assess the effects of acidification (pH 6.5 vs. pH 8.0) under two salinity conditions (brackish water—BW vs. seawater—SW) on the development and fitness (oxidative stress) of early developing seahorses (Hippocampus reidi). The growth of juveniles reared in BW was impaired at pH 6.5, and the levels of superoxide dismutase and DT-diaphorase, as well as the oxidative stress index, increased compared to SW juveniles. However, survival and growth at pH 6.5 decreased in the former. These results suggest higher overall performance and optimal fitness in juveniles reared in seawater under acidic conditions (pH = 6.5).
Abstract
Water acidification affects aquatic species, both in natural environmental conditions and in ex situ rearing production systems. The chronic effects of acidic conditions (pH 6.5 vs. pH 8.0) in seahorses (Hippocampus spp.) are not well known, especially when coupled with salinity interaction. This study investigated the implications of pH on the growth and oxidative stress in the seahorse Hippocampus reidi (Ginsburg, 1933), one of the most important seahorse species in the ornamental trade. Two trials were carried out in juveniles (0–21 and 21–50 DAR—days after the male’s pouch release) reared under acid (6.5) and control (8.0) pH, both in brackish water (BW—salinity 11) and seawater (SW—salinity 33). In the first trial (0–21 DAR), there was no effect of pH on the growth of seahorses reared in SW, but the survival rate was higher for juveniles raised in SW at pH 6.5. However, the growth and survival of juveniles reared in BW were impaired at pH 6.5. Compared to SW conditions, the levels of superoxide dismutase and DT-diaphorase, as well as the oxidative stress index, increased for juveniles reared in BW. In the second trial, seahorse juveniles were reared in SW at pH 8.0, and subsequently kept for four weeks (from 21 to 50 DAR) at pH 6.5 and 8.0. The final survival rates and condition index were similar in both treatments. However, the growth under acidic conditions was higher than at pH 8.0. In conclusion, this study highlights that survival, growth, and oxidative status condition was enhanced in seahorse juveniles reared in SW under acidic conditions (pH = 6.5). The concurrent conditions of acidic pH (6.5) and BW should be avoided due to harmful effects on the fitness and development of seahorse juveniles.
Continue reading ‘Implications of salinity and acidic environments on fitness and oxidative stress parameters in early developing seahorses Hippocampus reidi’Responses of corals and coral reef ecosystems to ocean acidification under variable temperature and light
Published 19 December 2022 Science ClosedTags: biological response, BRcommunity, calcification, corals, field, growth, laboratory, light, molecular biology, mortality, multiple factors, photosynthesis, physiology, protists, temperature, vents
Coral reefs are under increasing pressure from ocean acidification. However, much of our understanding is based on single-species aquarium experiments made in isolation from realistic environmental parameters (e.g. light, water flow, food supply) and other co occurring stressors (e.g. increasing sea surface temperatures, reduced water clarity due to terrestrial runoff). In my PhD project I aimed to understand how ocean acidification affects the ecophysiology of reef corals and reef communities in natural settings, and how effects may differ with concurrent exposure to variable temperature and light. I used a combination of experimental and observational studies at unique field sites with naturally high levels of CO2 (CO2 seep sites), and multi-factor experiments in the aquarium facilities of The Australian Institute of Marine Science’s National Sea Simulator to address these questions.
In chapter 2, I investigated if corals can acclimate to ocean acidification by switching their photosymbionts to types that may be able to utilise the more abundant CO2 in photosynthesis. I used molecular techniques to investigate the dominant photosymbiont types in six species of coral from the field and found them to be highly conserved within species between CO2 seep and control sites. In chapter 3, I used a combination of field surveys and a multifactor laboratory experiment to investigate if elevated CO2 increased the severity of coral thermal bleaching. Field surveys during a bleaching event at the CO2 seeps, as well as the experimental study, both showed that corals were not significantly more susceptible to thermal stress under high CO2. In chapter 4, I used a multifactor laboratory experiment to investigate if reduced or variable daily light availability affected the responses of corals to high CO2. Here I found that reductions in light levels, regardless of the variability in daily light integrals, can reduce coral growth rates more than high CO2. In chapter 5, I followed the development of early successional coral reef benthic communities on settlement tiles along a gradient of CO2 exposure at the seep sites, and further measured rates of community metabolism. Here high CO2 strongly influenced the development of communities, shifting them away from a dominance of calcifying taxa under present day conditions to a range of non-calcifying algae as CO2 levels increased. These high CO2 communities progressively recorded lower rates of calcification and higher rates of hotosynthesis at high CO2.
Results from this thesis show that the considerable changes to the CO2 seep benthic communities are likely due to secondary ecological effects, rather than the physiological effects on corals alone. Moreover, the negative effects of cooccurring stressors on corals and coral reefs will also be substantial. Hence there is an immediate need to reduce atmospheric CO2 emissions and improve the management of local stressors to prevent further declines to the health and functioning of coral reef ecosystems.
Continue reading ‘Responses of corals and coral reef ecosystems to ocean acidification under variable temperature and light’Decreased salinity offsets the stimulation of elevated pCO2 on photosynthesis and synergistically inhibits the growth of juvenile sporophyte of Saccharina japonica (Laminariaceae, Phaeophyta)
Published 12 December 2022 Science ClosedTags: algae, biological response, growth, laboratory, multiple factors, North Pacific, photosynthesis, physiology, salinity
The combined effect of elevated pCO2 (Partial Pressure of Carbon Dioxide) and decreased salinity, which is mainly caused by freshwater input, on the growth and physiological traits of algae has been poorly assessed. In order to investigate their individual and interactive effects on the development of commercially farmed algae, the juvenile sporophytes of Saccharina japonica were cultivated under different levels of salinity (30, 25 and 20 psu) and pCO2 (400 and 1000 µatm). Individually, decreased salinity significantly reduced the growth rate and pigments of S. japonica, indicating that the alga was low-salinity stressed. The maximum quantum yield, Fv/Fm, declined at low salinities independent of pCO2, suggesting that the hyposalinity showed the main effect. Unexpectedly, the higher pCO2 enhanced the maximum relative electron transport rate (rETRmax) but decreased the growth rate, pigments and soluble carbohydrates contents. This implies a decoupling between the photosynthesis and growth of this alga, which may be linked to an energetic reallocation among the different metabolic processes. Interactively and previously untested, the decreased salinity offset the improvement of rETRmax and aggravated the declines of growth rate and pigment content caused by the elevated pCO2. These behaviors could be associated with the additionally decreased pH that was induced by the low salinity. Our data, therefore, unveils that the decreased salinity may increase the risks of future CO2-induced ocean acidification on the production of S. japonica.
Continue reading ‘Decreased salinity offsets the stimulation of elevated pCO2 on photosynthesis and synergistically inhibits the growth of juvenile sporophyte of Saccharina japonica (Laminariaceae, Phaeophyta)’Biological responses of the predatory blue crab and its hard clam prey to ocean acidification and low salinity
Published 9 December 2022 Science ClosedTags: biological response, BRcommunity, crustaceans, growth, laboratory, mesocosms, mollusks, morphology, mortality, multiple factors, performance, predation, salinity
How ocean acidification (OA) interacts with other stressors is understudied, particularly for predators and prey. We assessed long-term exposure to decreased pH and low salinity on (1) juvenile blue crab Callinectes sapidus claw pinch force, (2) juvenile hard clam Mercenaria mercenaria survival, growth, and shell structure, and (3) blue crab and hard clam interactions in filmed mesocosm trials. In 2018 and 2019, we held crabs and clams from the Chesapeake Bay, USA, in crossed pH (low: 7.0, high: 8.0) and salinity (low: 15, high: 30) treatments for 11 and 10 wk, respectively. Afterwards, we assessed crab claw pinch force and clam survival, growth, shell structure, and ridge rugosity. Claw pinch force increased with size in both years but weakened in low pH. Clam growth was negative, indicative of shell dissolution, in low pH in both years compared to the control. Growth was also negative in the 2019 high-pH/low-salinity treatment. Clam survival in both years was lowest in the low-pH/low-salinity treatment and highest in the high-pH/high-salinity treatment. Shell damage and ridge rugosity (indicative of deterioration) were intensified under low pH and negatively correlated with clam survival. Overall, clams were more severely affected by both stressors than crabs. In the filmed predator-prey interactions, pH did not substantially alter crab behavior, but crabs spent more time eating and burying in high-salinity treatments and more time moving in low-salinity treatments. Given the complex effects of pH and salinity on blue crabs and hard clams, projections about climate change on predator-prey interactions will be difficult and must consider multiple stressors.
Continue reading ‘Biological responses of the predatory blue crab and its hard clam prey to ocean acidification and low salinity’Corals adapted to extreme and fluctuating seawater pH increase calcification rates and have unique symbiont communities
Published 7 December 2022 Science ClosedTags: biological response, BRcommunity, calcification, chemistry, corals, field, growth, laboratory, molecular biology, morphology, photosynthesis, physiology, protists, South Pacific
Ocean acidification (OA) is a severe threat to coral reefs mainly by reducing their calcification rate. Identifying the resilience factors of corals to decreasing seawater pH is of paramount importance to predict the survivability of coral reefs in the future. This study compared corals adapted to variable pH (i.e., 7.23-8.06 pH units) from the semi-enclosed lagoon of Bouraké, New Caledonia, to corals adapted to more stable seawater pH (i.e., 7.90-8.18 pH units). In a 100-day aquarium experiment, we examined the physiological response and genetic diversity of Symbiodiniaceae from three coral species ( Acropora tenuis , Montipora digitata and Porites sp.) from both sites under three stable pH conditions (i.e., 8.11, 7.76, 7.54 pH units) and fluctuating pH conditions (i.e., between 7.56 and 8.07 pH units). Bouraké corals consistently exhibited higher growth rates than corals from the stable pH environment, with specific ITS2 intragenomic variant profiles. While OA generally decreased coral calcification by ca. 16%, Bouraké coralsshowed higher growth rates (21 to 93% increase, depending on species with all pH conditions pooled) than those from the stable pH environment. This superior performance coincided with divergent ITS2-like profiles with better consistency for both variable and low pH conditions. This response was not gained by corals from the more stable environment exposed to variable pH during the four-month experiment, suggesting that such a kind of plasticity is time dependent. Future long-term experiments should address the exposure duration required to confer fitness benefits for sustained calcification, hopefully fast enough to cope with the ongoing rapid OA.
Continue reading ‘Corals adapted to extreme and fluctuating seawater pH increase calcification rates and have unique symbiont communities’Effects of temperature and pH on the growth, calcification, and biomechanics of two species of articulated coralline algae
Published 23 November 2022 Science ClosedTags: biological response, corals, growth, morphology, multiple factors, physiology, temperature
Ocean warming and acidification are predicted to impact the physiology of marine organisms, especially marine calcifiers that must deposit calcium carbonate and resist dissolution. Of particular concern are articulated coralline algae, which must maintain both calcified segments (intergenicula) and uncalcified joints (genicula) in order to thrive along wave-swept rocky coastlines. We examined the effect of pH and temperature, both individually and in combination, on the growth, calcification, and biomechanical properties of 2 species of articulated coralline algae, Corallina vancouveriensis and Calliarthron tuberculosum, common on wave-exposed shores in the NE Pacific. Increased temperature and reduced pH were found to reduce growth rates in both species (30-89% lower) but had little influence on the amount of intergenicular calcium carbonate or on the genicular biomechanical properties of these species. Results suggest that although growth rates may decline, these 2 coralline species will maintain the integrity of their tissues and continue to persist under future climate stress.
Continue reading ‘Effects of temperature and pH on the growth, calcification, and biomechanics of two species of articulated coralline algae’Community context and pCO2 impact the transcriptome of the “helper” bacterium Alteromonas in co-culture with picocyanobacteria
Published 22 November 2022 Science ClosedTags: biological response, BRcommunity, growth, laboratory, molecular biology, physiology, prokaryotes
Many microbial photoautotrophs depend on heterotrophic bacteria for accomplishing essential functions. Environmental changes, however, could alter or eliminate such interactions. We investigated the effects of changing pCO2 on gene transcription in co-cultures of 3 strains of picocyanobacteria (Synechococcus strains CC9311 and WH8102 and Prochlorococcus strain MIT9312) paired with the ‘helper’ bacterium Alteromonas macleodii EZ55. Co-culture with cyanobacteria resulted in a much higher number of up- and down-regulated genes in EZ55 than pCO2 by itself. Pathway analysis revealed significantly different transcription of genes involved in carbohydrate metabolism, stress response, and chemotaxis, with different patterns of up- or down-regulation in co-culture with different cyanobacterial strains. Gene transcription patterns of organic and inorganic nutrient transporter and catabolism genes in EZ55 suggested resources available in the culture media were altered under elevated (800 ppm) pCO2 conditions. Altogether, changing transcription patterns were consistent with the possibility that the composition of cyanobacterial excretions changed under the two pCO2 regimes, causing extensive ecophysiological changes in both members of the co-cultures. Additionally, significant downregulation of oxidative stress genes in MIT9312/EZ55 cocultures at 800 ppm pCO2 were consistent with a link between the predicted reduced availability of photorespiratory byproducts (i.e., glycolate/2PG) under this condition and observed reductions in internal oxidative stress loads for EZ55, providing a possible explanation for the previously observed lack of “help” provided by EZ55 to MIT9312 under elevated pCO2. If similar broad alterations in microbial ecophysiology occur in the ocean as atmospheric pCO2 increases, they could lead to substantially altered ecosystem functioning and community composition.
Continue reading ‘Community context and pCO2 impact the transcriptome of the “helper” bacterium Alteromonas in co-culture with picocyanobacteria’
