Understanding the long-term response of key marine phytoplankton species to ongoing global changes is pivotal in determining how oceanic community composition will respond over the coming decades. To better understand the impact of ocean acidification and warming, we acclimated two strains of Skeletonema marinoi isolated from natural communities to three pCO2 (400 atm, 600 atm and 1000 atm) for 8 months and five temperature conditions (7°C, 10°C, 13°C, 16°C and 19°C) for 11 months. These strains were then tested in natural microbial communities, exposed to three pCO2 treatments (400 atm, 600 atm and 1000 atm). DNA metabarcoding of the 16S and 18S gene for prokaryotes and eukaryotes respectively was used to show differences in abundance and diversity between the three CO2 treatments. We found there were no significant differences in acclimated S. marinoi concentrations between the three pCO2 treatments, most likely due to the high variability these strains experience in their natural environment. There were significant compositional differences between the pCO2 treatments for prokaryotes suggesting that indirect changes to phytoplankton-bacteria interactions could be a possible driver of bacterial community composition. Yet, there were no differences for eukaryotic community composition, with all treatments dominated by diatoms (but not the acclimated S. marinoi) resulting in similar biodiversity. Furthermore, strain-specific differences in community composition suggests interactions between prokaryotic and eukaryotic taxa could play a role in determining future community composition.
Continue reading ‘Acclimation to various temperature and pCO2 levels does not impact the competitive ability of two strains of Skeletonema marinoi in natural communities subjected to different pCO2 treatments’Posts Tagged 'temperature'
Acclimation to various temperature and pCO2 levels does not impact the competitive ability of two strains of Skeletonema marinoi in natural communities subjected to different pCO2 treatments
Published 12 July 2023 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, molecular biology, multiple factors, otherprocess, phytoplankton, prokaryotes, temperature
Potential for acclimation of banded-dye murex, Hexaplex trunculus (Linnaeus, 1758) aft er long-term exposure to low pH
Published 5 July 2023 Science ClosedTags: adaptation, biological response, growth, laboratory, Mediterranean, mollusks, multiple factors, otherprocess, temperature
Previous work on ocean acidification highlighted contrasting response between marine species and population. This so-called species-specific response was hypothesized to be partly a consequence of local adaptation to the present range of natural variability in the carbonate chemistry. Under that hypothesis, species tolerance threshold should be correlated to its environmental pH niche. This paper aims to evaluate shell growth rate of Hexaplex trunculus, an important predatory gastropod in benthic communities of Mali Ston Bay. A long-term experiment (310 days) was designed to test a range of pH treatments covering present and future pH levels relevant in the context of future ocean acidification (7.95-7.22 pHT) at the sampling site. Sex had an effect on the shell growth rate irrespective of pH, and was only significant after 236 days. As growth rate in all pH treatments followed seasonal patterns correlating to changes in seawater temperature, the data were divided into 3 time periods. A positive relationship between shell growth rate (SGR, mm day-1) and pH was observed for the period 1-59 days (temperature ranging between 26.5 & 18.8 °C), whereas SGR decreased significantly with pH for the following period (60-236 days, temperature ranging between 20.6 & 8.5 °C). After 236 days (temperature ranging between 27.5 & 14.1 °C), there was no significant difference in SGR among pH. Similar temperature was experienced between the first and third period and the difference in response could be explained as a consequence of an acute negative response versus a longer exposure indicating possible potential for acclimation. Our results highlight the modulating eff ect of temperature and the importance of long-term experiments to better assess impacts of ocean acidifi cation on marine organisms.
Continue reading ‘Potential for acclimation of banded-dye murex, Hexaplex trunculus (Linnaeus, 1758) aft er long-term exposure to low pH’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’FNRCThe roles of carbonate, borate, and bicarbonate ions in affecting zooplankton hatching success under ocean acidification
Published 27 June 2023 Science ClosedTags: biogeochemistry, biological response, individualmodeling, modeling, multiple factors, physiology, reproduction, respiration, review, temperature, zooplankton
Two ocean acidification studies about egg hatching success (HS) in geographically important marine copepods, Calanus finmarchicus and C. helgolandicus, were reanalyzed with improved statistical procedures. The new results at low and moderate levels of seawater acidification showed no HS inhibition at normal habitat temperatures but statistically significant inhibition at warmer and colder temperatures. These HS results were compared with seawater carbonate system and borate concentrations from precise seawater measurements. The temperature dependent differences in HS could not be directly explained by changes in the seawater concentrations of either H+, bicarbonate (HCO3−), or CO2* (CO2* being the sum of unhydrated CO2 and H2CO3). In contrast, HS differences did match trends in seawater carbonate (CO32−) concentrations. A numerical model was developed which evaluates the concentrations of O2 or CO2*, HCO3−, and CO32− at the cellular level across an egg and embryo by considering both gas diffusion with the seawater and respiration by the embryo. Again, temperature-dependent trends in HS could not be explained changes in intracellular CO2* or HCO3− concentrations, but HS did trend with the changes in intracellular CO32− concentrations. Carbonate ions form strong coordination complexes with metals, so acidification-driven decreases in external seawater carbonate concentrations, which are amplified at warmer temperatures, could release injurious metals, thus driving the HS inhibition at warmer temperatures. Increases in cytoplasmic carbonate concentrations at warmer temperatures caused by seawater acidification could complex with biochemically-needed nutrient-type metals within the cells, also causing the increased HS inhibition at warmer temperatures. Furthermore, boron is essential in chemically signaling within and between cells. Seawater borate concentrations were closely correlated with HS inhibition via Michaelis-Menton equations, suggesting that acidification-driven decreases in seawater borate concentrations may also inhibit HS. Finally, the acidification-driven increases in CO2 diffusion into cells dramatically increased intracellular bicarbonate concentrations. At mild levels of seawater acidification, an organism might compensate by exporting bicarbonate from the cells to the haemolymph and then to the seawater. Although the energetic cost, as percentage of ATP production, might be high, increased respiration rates at warmer temperatures might better allow the organism to survive. However, as temperature is lowered, the cellular respiration rate declines more rapidly with respect to temperature than does the gas diffusion coefficient. Consequently, bicarbonate accumulation driven by inward CO2 diffusion might overwhelm the egg’s bicarbonate export capacity at colder temperatures, explaining the colder temperature HS inhibition.
Continue reading ‘FNRCThe roles of carbonate, borate, and bicarbonate ions in affecting zooplankton hatching success under ocean acidification’Impact of fluctuating temperature and elevated CO2 on the growth, survival, and metabolic rate of the endangered pinto abalone (Haliotis kamtschatkana) in the Salish Sea
Published 23 June 2023 Science ClosedTags: biological response, laboratory, mollusks, morphology, mortality, multiple factors, North Pacific, physiology, temperature
Pinto abalone (Haliotis kamtschatkana) is the only abalone species found in the Salish Sea in the northeastern Pacific Ocean. They were recently declared as a State endangered species and human intervention is necessary to recover the species. Puget Sound Restoration Fund (PSRF) is one of the organizations trying to restore pinto abalone populations in the Salish Sea. Some of their outplant sites are less successful than others although they are physically similar. Currently, there is no research on how environmental variation affects juvenile pinto abalone survival, growth, and metabolic rate.
The goal of my thesis was to simulate summer sea water temperature fluctuations in the Salish Sea at different pCO2 levels. I investigated how these treatments affected juvenile pinto abalone growth, survival, and metabolic rate. I also included abalone size as a factor in my growth and survival experiment. I hypothesized that (1) fluctuating temperature and elevated pCO2 would negatively interact, resulting in less growth and survival, with larger abalone less affected. And (2) that fluctuating temperature and elevated pCO2 would synergistically interact, resulting in abalone with an increased metabolic rate. Fluctuating temperature significantly decreased abalone survival. Growth was not impacted by initial size nor pCO2 level. There was a significant interaction between temperature and pCO2 on abalone metabolic rate.
In addition to the physical parameters used to determine outplant sites, PSRF can use my findings to choose outplant sites better suited for juvenile pinto abalone to increase the probability of their populations recovering in the Salish Sea.
Continue reading ‘Impact of fluctuating temperature and elevated CO2 on the growth, survival, and metabolic rate of the endangered pinto abalone (Haliotis kamtschatkana) in the Salish Sea’Projected ocean acidification and seasonal temperature alter the behaviour and growth of a range extending tropical fish
Published 21 June 2023 Science ClosedTags: biological response, fish, laboratory, morphology, multiple factors, performance, South Pacific, temperature
Climate-driven invasions of ecosystems by range-extending animals are often mediated by behavioural modifications that increase their chances of establishment in foreign biological communities. This creates novel ecological interactions that can affect the behaviour of native species in recipient ecosystems. However, this question has seldom been addressed in marine systems, in particular with the additive effect of ocean acidification and the mediating effects of seasonal climate variability. Here, we performed a laboratory experiment to evaluate how novel species interactions, ocean acidification, and projected future summer versus winter temperatures could affect the behaviour and growth of a range-extending tropical and co-shoaling temperate fish. Compared to current-day summer temperatures, tropical fish became 4% more active, 90% more aggressive, and increased their growth rates (standard length: +42%) during future summers in their novel poleward ranges, but reduced their aggression by 64%, boldness by 52%, feeding by 45% and growth rates (wet weight: −70%, standard length: −26%) during future winters compared to current-day summer temperatures. Additionally, tropical fish became 3% more active under ocean acidification compared to no ocean acidification. Conversely, temperate fish behaviour was unaffected by climate treatments but their growth rates were > 200% faster under future winter versus current and future summer temperatures. We conclude that projected future winter conditions in temperate ecosystems may reduce the performance of range-extending fishes in temperate fish communities and slow down tropicalisation of higher latitudes.
Continue reading ‘Projected ocean acidification and seasonal temperature alter the behaviour and growth of a range extending tropical fish’Effects of climate change on the growth and chemical composition of primary producers and its impacts on coastal aquaculture
Published 21 June 2023 Science ClosedTags: abundance, algae, growth, laboratory, multiple factors, North Atlantic, otherprocess, physiology, phytoplankton, temperature
Coastal aquaculture has been growing rapidly in the last decades as a response to the global seafood demand and overexploited wild marine populations. As more sustainable food production practices are sought, the attention on the production of low trophic level organisms has increased significantly. Responsible production of primary producers and primary consumers in coastal areas can help meet the ever-increasing seafood demands and ease burdens on natural resources. However, conditions in coastal areas are not easy to control, and changes in ambient factors can impact coastal aquaculture productivity in various ways. Temperature and pH are factors that are already changing globally and are expected to keep changing in response to climate change.
The growth and chemical composition of primary producers, like algae and seaweed, are influenced by the ambient conditions where they grow. Their cells can chemically adapt to the environment, responding to changes in ambient conditions by producing biomass with different nutritional values. Primary producers are the base of the food chain in aquatic ecosystems, serving as a food source for consumers at higher trophic levels. Herbivores and filter feeders directly depend on the availability of good quality primary producers’ sources, hence, any changes in the nutrient content and growth of primary producers will affect the ability to produce these species. Therefore, to assure sustainable growth of coastal aquaculture, it is important to understand how species of interest are affected by the changes in ambient conditions predicted due to climate change, and how they interact and relate to each other.
Here, the relationship between environmental conditions, primary producers, and primary consumers was explored. The main goal of this study was to understand how changes in temperature and pH can influence the production of herbivore species in coastal areas, by changing the nutritional value of their diets. For this, as a first approximation, a microalgae culture system that maintained multiple pH cultures through automatic addition of CO2 to keep the desired pH was designed, and the effects of temperature and pH on the growth and protein content of two species of marine microalgae were explored. The species Nannochloropsis oculata and Chaetoceros gracilis were selected for this study as they are important species in coastal aquaculture of filter feeder species. The study consisted of growing these two species under two different temperatures, 13°C and 20°C, and two pH levels, 8.2 and 7.6, representing the current and projected ocean conditions, in Northern California, due to climate change, respectively. The highest final cell count, specific growth rate, and protein content were found when both species of algae were grown at 20°C and pH 7.6, indicating the projected conditions caused by climate change did not have negative effects on the marine microalgae tested. The statistical analysis results for all the parameters suggest that temperature has a bigger influence than pH on both species of algae.
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The results of this study suggest that rising ocean temperature and ocean acidification caused by climate change might have positive effects on the protein content and the growth of the marine microalgae studied. Furthermore, temperature seemed to be a more influential factor than pH. In the same way, rising ocean temperature positively affected the protein content of the seaweed studied, however, its growth and condition deteriorated as temperature increased. Therefore, even though dulse growing at 17°C yielded higher growth rates of abalone, keeping this seaweed at higher temperatures will not be sustainable. The different diets used for this study did not affect the nutritional composition of the juvenile red abalone. Finally, higher temperatures due to climate change did not seem to have negative indirect effects on the juvenile red abalone and overall dulse growth rate was the only factor studied that was negatively affected by the predicted conditions due to climate change.
Continue reading ‘Effects of climate change on the growth and chemical composition of primary producers and its impacts on coastal aquaculture’Variable food alters responses of larval crown-of-thorns starfish to ocean warming but not acidification
Published 20 June 2023 Science ClosedTags: biological response, echinoderms, laboratory, morphology, mortality, multiple factors, nutrients, performance, South Pacific, temperature
Phytoplankton abundance is decreasing and becoming more variable as the ocean climate changes. We examine how low, high, and variable phytoplankton food supply affected the survival, development, and growth of larval crown-of-thorns starfish, Acanthaster sp. exposed to combined warming (26, 30 °C) and acidification (pH 8.0, 7.6). Larvae fed a low food ration are smaller, and develop slower and with more abnormalities than larvae fed a high ration. Larvae fed a variable food supply (low, followed by high ration) overcome the negative effects of low food on development rate and occurrence of abnormalities, but are 16–17% smaller than larvae fed the high ration continuously. Acidification (pH 7.6) slows growth and development and increases abnormalities regardless of the food regime. Warming slows growth and development, but these effects are mitigated by high food availability. As tropical oceans warm, the success of crown-of-thorns starfish larvae may depend on the abundance of their phytoplankton prey.
Continue reading ‘Variable food alters responses of larval crown-of-thorns starfish to ocean warming but not acidification’Global climate change increases the impact of pollutant mixtures in the model species Paracentrotus lividus
Published 20 June 2023 Science ClosedTags: biological response, echinoderms, laboratory, morphology, multiple factors, North Atlantic, reproduction, temperature, toxicants
Highlights
- Impact of chlorpyrifos (CPF) and microplastics (MP) on P. lividus is studied.
- We also studied if climate change increases the toxicity of these pollutants.
- CPF has a marked effect on growth of larvae, but less on the fertilisation rate.
- MP increases the negative effect of CPF on growth and development.
- Global climate change conditions increase the sensitivity of embryos to MP and CPF.
Abstract
The goal of the present work is to study whether ocean- acidification (OA) and -warming (OW) could increase the toxicity of pollutants on P. lividus. We studied how model pollutants such as chlorpyrifos (CPF) and microplastics (MP), alone or in combination, impact the fertilisation process, and the development of larvae under conditions of OA (dissolved inorganic carbon increase of 126 × 10−6 mol per kg of sea water) and OW (temperature increase of 4 °C) predicted by FAO (Food and Agriculture Organization) for the next 50 years. Fertilisation was determined by microscopic examination after 1 h. Growth, morphology, and alteration level were measured after 48 h of incubation. Results showed that CPF has a marked effect on the growth of larvae, but less on the fertilisation rate. When larvae are exposed to both MP and CPF, the effect on fertilisation and growth is higher than when CPF is added alone. Larvae exposed to CPF tend to adopt a rounded shape which is detrimental to their buoyancy and the combination with other stressors aggravate this situation. The variables most influenced by CPF or its mixtures are those related to body length, body width, and higher levels of body abnormalities, which is consistent with the degenerative effects caused by CPF on sea urchin larvae. The PCA analysis showed that temperature has more influence when embryos or larvae are exposed to a combination of stressors, demonstrating that global climate change drastically increase the impact of CPF on aquatic ecosystems. Overall, in this work we demonstrated that global climate change conditions increase the sensitivity of embryos to MP and CPF. Our findings support the idea that global change conditions could have a severe impact on marine life, increasing the negative effect of toxic agents commonly present in the sea and their mixtures.
Continue reading ‘Global climate change increases the impact of pollutant mixtures in the model species Paracentrotus lividus’Future ocean conditions induce necrosis, microbial dysbiosis and nutrient cycling imbalance in the reef sponge Stylissa flabelliformis
Published 16 June 2023 Science ClosedTags: abundance, archaea, biological response, BRcommunity, community composition, laboratory, molecular biology, multiple factors, otherprocess, physiology, porifera, prokaryotes, South Pacific, temperature
Oceans are rapidly warming and acidifying in the context of climate change, threatening sensitive marine biota including coral reef sponges. Ocean warming (OW) and ocean acidification (OA) can impact host health and associated microbiome, but few studies have investigated these effects, which are generally studied in isolation, on a specific component of the holobiont. Here we present a comprehensive view of the consequences of simultaneous OW and OA for the tropical sponge Stylissa flabelliformis. We found no interactive effect on the host health or microbiome. Furthermore, OA (pH 7.6 versus pH 8.0) had no impact, while OW (31.5 °C versus 28.5 °C) caused tissue necrosis, as well as dysbiosis and shifts in microbial functions in healthy tissue of necrotic sponges. Major taxonomic shifts included a complete loss of archaea, reduced proportions of Gammaproteobacteria and elevated relative abundances of Alphaproteobacteria. OW weakened sponge-microbe interactions, with a reduced capacity for nutrient exchange and phagocytosis evasion, indicating lower representations of stable symbionts. The potential for microbially-driven nitrogen and sulphur cycling was reduced, as was amino acid metabolism. Crucially, the dysbiosis annihilated the potential for ammonia detoxification, possibly leading to accumulation of toxic ammonia, nutrient imbalance, and host tissue necrosis. Putative defence against reactive oxygen species was greater at 31.5 °C, perhaps as microorganisms capable of resisting temperature-driven oxidative stress were favoured. We conclude that healthy symbiosis in S. flabelliformis is unlikely to be disrupted by future OA but will be deeply impacted by temperatures predicted for 2100 under a “business-as-usual” carbon emission scenario.
Continue reading ‘Future ocean conditions induce necrosis, microbial dysbiosis and nutrient cycling imbalance in the reef sponge Stylissa flabelliformis’The impacts of ocean acidification, warming and their interactive effects on coral prokaryotic symbionts
Published 14 June 2023 Science ClosedTags: biological response, BRcommunity, community composition, corals, laboratory, molecular biology, multiple factors, North Pacific, otherprocess, physiology, primary production, prokaryotes, temperature
Reef-building corals, the foundation of tropical coral reefs, are vulnerable to climate change e.g. ocean acidification and elevated seawater temperature. Coral microbiome plays a key role in host acclimatization and maintenance of the coral holobiont’s homeostasis under different environmental conditions, however, the response patterns of coral prokaryotic symbionts to ocean acidification and/or warming are rarely known at the metatranscriptional level, particularly the knowledge of interactive and persistent effects is limited. Using branching Acropora valida and massive Galaxea fascicularis as models in a lab system simulating extreme ocean acidification (pH 7.7) and/or warming (32 °C) in the future, we investigated the changes of in situ active prokaryotic symbionts community and gene expression of corals under/after (6/9 d) acidification (A), warming (H) and acidification–warming (AH) by metatranscriptome analysis with pH8.1, 26 °C as the control.
Continue reading ‘The impacts of ocean acidification, warming and their interactive effects on coral prokaryotic symbionts’Interaction matters: bottom-up driver interdependencies alter the projected response of phytoplankton communities to climate change
Published 9 June 2023 Science ClosedTags: abundance, biological response, community composition, communitymodeling, globalmodeling, light, modeling, multiple factors, otherprocess, phytoplankton, regionalmodeling, temperature
Phytoplankton growth is controlled by multiple environmental drivers, which are all modified by climate change. While numerous experimental studies identify interactive effects between drivers, large-scale ocean biogeochemistry models mostly account for growth responses to each driver separately and leave the results of these experimental multiple-driver studies largely unused. Here, we amend phytoplankton growth functions in a biogeochemical model by dual-driver interactions (CO2 and temperature, CO2 and light), based on data of a published meta-analysis on multiple-driver laboratory experiments. The effect of this parametrization on phytoplankton biomass and community composition is tested using present-day and future high-emission (SSP5-8.5) climate forcing. While the projected decrease in future total global phytoplankton biomass in simulations with driver interactions is similar to that in control simulations without driver interactions (5%–6%), interactive driver effects are group-specific. Globally, diatom biomass decreases more with interactive effects compared with the control simulation (−8.1% with interactions vs. no change without interactions). Small-phytoplankton biomass, by contrast, decreases less with on-going climate change when the model accounts for driver interactions (−5.0% vs. −9.0%). The response of global coccolithophore biomass to future climate conditions is even reversed when interactions are considered (+33.2% instead of −10.8%). Regionally, the largest difference in the future phytoplankton community composition between the simulations with and without driver interactions is detected in the Southern Ocean, where diatom biomass decreases (−7.5%) instead of increases (+14.5%), raising the share of small phytoplankton and coccolithophores of total phytoplankton biomass. Hence, interactive effects impact the phytoplankton community structure and related biogeochemical fluxes in a future ocean. Our approach is a first step to integrate the mechanistic understanding of interacting driver effects on phytoplankton growth gained by numerous laboratory experiments into a global ocean biogeochemistry model, aiming toward more realistic future projections of phytoplankton biomass and community composition.
Continue reading ‘Interaction matters: bottom-up driver interdependencies alter the projected response of phytoplankton communities to climate change’Microbial mats as model to decipher climate change effect on microbial communities through a mesocosm study
Published 7 June 2023 Science ClosedTags: adaptation, biological response, BRcommunity, community composition, laboratory, mesocosms, methods, multiple factors, otherprocess, performance, physiology, prokaryotes, temperature
Marine environments are expected to be one of the most affected ecosystems by climate change, notably with increasing ocean temperature and ocean acidification. In marine environments, microbial communities provide important ecosystem services ensuring biogeochemical cycles. They are threatened by the modification of environmental parameters induced by climate change that, in turn, affect their activities. Microbial mats, ensuring important ecosystem services in coastal areas, are well-organized communities of diverse microorganisms representing accurate microbial models. It is hypothesized that their microbial diversity and metabolic versatility will reveal various adaptation strategies in response to climate change. Thus, understanding how climate change affects microbial mats will provide valuable information on microbial behaviour and functioning in changed environment. Experimental ecology, based on mesocosm approaches, provides the opportunity to control physical-chemical parameters, as close as possible to those observed in the environment. The exposure of microbial mats to physical-chemical conditions mimicking the climate change predictions will help to decipher the modification of the microbial community structure and function in response to it. Here, we present how to expose microbial mats, following a mesocosm approach, to study the impact of climate change on microbial community.
Continue reading ‘Microbial mats as model to decipher climate change effect on microbial communities through a mesocosm study’Effects of anthropogenic stressorson Helgoland’s lobsters(Homarus gammarus)
Published 2 June 2023 Science ClosedTags: biological response, crustaceans, laboratory, morphology, mortality, multiple factors, North Atlantic, physiology, temperature
As meroplankton, lobsters make up a great portion of both benthic communities and planktonic fauna in the water column. Furthermore, they represent a mayor food source across the marine food web and a vital source of protein for humans. As an economically important species, lobsters are highly susceptible to anthropogenic stressors (e.g habitat destruction, over-fishing, noise pollution). Moreover, climate change may magnify the impact of human activities on lobsters’ fitness. The collapse of the population of European lobster (Homarus gammarus) around Helgoland constitutes a good example and prompted a largescale restocking program. Yet, the question arises if recruitment of remaining natural individuals and program released specimens could be stunted by ongoing climate change and human activities.
In my thesis I investigate the effect of several anthropogenic stressors that could potentially be affecting the route to recovery of Helgoland’s lobsters.
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Owing to the difficulties in catching lobster larvae in the field, I used larvae from lobster-rearing facilities to study the effects of anthropogenic stress on larval development and physiology. Studies on the effects of climate change on European lobster larvae have mostly focused on the isolated effect of ocean acidification or warming. Acidification treatments were based on two shared socio-economic pathways emitted by the Intergovernmental Panel on Climate Change (IPCC) regarding the amount of atmospheric CO2 for the end of the century. This study is the first to provide a more complete picture of the thermal limits at different levels of biological organization of lobster larvae under acidification by including a ten-level temperature gradient setup (13-24°C) The results show temperature was positively correlated with growth and energy metabolism; while, pCO2 had a negative impact on survival and morphology. Thus, climate change could potentially stunt the European lobster restocking efforts taking place on the island.
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Continue reading ‘Effects of anthropogenic stressorson Helgoland’s lobsters(Homarus gammarus)’Separate and combined effects of elevated pCO2 and temperature on the branching reef corals Acropora digitifera and Montipora digitata
Published 31 May 2023 Science ClosedTags: abundance, algae, biological response, calcification, corals, laboratory, mortality, multiple factors, North Pacific, otherprocess, photosynthesis, temperature
Ocean acidification (OA) and warming (OW) are major global threats to coral reef ecosystems; however, studies on their combined effects (OA + OW) are scarce. Therefore, we evaluated the effects of OA, OW, and OA + OW in the branching reef corals Acropora digitifera and Montipora digitata, which have been found to respond differently to environmental changes. Our results indicate that OW has a greater impact on A. digitifera and M. digitata than OA and that the former species is more vulnerable to OW than the latter. OW was the main stressor for increased mortality and decreased calcification in the OA + OW group, and the effect of OA + OW was additive in both species. Our findings suggest that the relative abundance and cover of M. digitata are expected to increase whereas those of A. digitifera may decrease in the near future in Okinawa.
Continue reading ‘Separate and combined effects of elevated pCO2 and temperature on the branching reef corals Acropora digitifera and Montipora digitata’Taphonomy and dissolution rates of the razor clam Ensis magnus shells: current status and projected acidification scenarios
Published 25 May 2023 Science ClosedTags: biological response, chemistry, dissolution, field, laboratory, modeling, mollusks, morphology, multiple factors, North Atlantic, regionalmodeling, temperature
Highlights
- Natural variability of seawater (Ta, Ωaragonite and pCO2) revealed an increase of acidification though such change did not suppose abrupt detrimental effects for taphonomic characteristics of shells (length, thickness, organic content or strength).
- Temperature affected negatively shell strength and thickness, although the large correlation between the environmental variables would disturb the individual characterization of environmental parameters.
- Dissolution rates of shells subjected to projected laboratory scenarios were significantly greater for cold-acidic environment (more corrosive) as compared to warm-acidic. Mean dissolution time (DT50) for cold-acidic scenario was reduced by half (15 years) as compared to current water chemistry conditions (30 years).
- More recent shells are being secreted in a progressively less saturated carbonate environment (at an annual rate of change of −0.0127 for Ωaragonite) and accordingly, were more prone to suffer dissolution (and weakening) in projected laboratory scenarios.
- Marine shells support ecosystem services including refuge for multiple species, substrate to attach and settle of fauna that may change in future environments or may bring changes in the ecological interactions of our coastal areas affecting biodiversity and optimal functioning of the ecosystem services.
Abstract
The analysis of the natural variability of seawater (Ta, Ωaragonite and pCO2) at Rodas Beach (NW Iberian Peninsula, Spain) revealed an increase of acidification. However, such pH change was not linked to any detrimental effect of the shell taphonomic characteristics of live razor clams harvested during distinct temporal series (length, thickness, organic content or strength). Temperature affected negatively shell strength and thickness, although the large correlation between the environmental variables would limit the individual characterization. Modelled trends in pH (and Ωaragonite) showed a significant decrease in the last 20 years, despite Ω > 1. Therefore, more recent shells are being secreted in a progressively less saturated carbonate environment and, consequently, more prone to suffer dissolution (and weakening) in projected climatic scenarios. When shells of harvested razor clams were exposed to projected climatic scenarios in the laboratory, dissolution rates were significantly greater for cold-acidic scenarios (more corrosive) as compared to warm-acidic. The median dissolution time (DT50) for shells under the cold-acidic scenario was reduced by half (15 years) when compared to the values observed for shells under current water chemistry conditions (30 years).
Galician coastline, often characterised by pCO2-rich and cold waters due to upwelling system, would represent the most corrosive scenario for the shells according to the responses monitored in our survey which highlight future compromise for the ecosystem services supplied by these hard skeletons. Future climate scenarios might condition performance of bivalves but also more complex processes related to carbonate structures. Local biodiversity may be lowered which may reduce the possibility that many species find shelter and feeding grounds, diminishing the optimal substrate for other organisms as needed elements for optimal services in the ecosystems.
Continue reading ‘Taphonomy and dissolution rates of the razor clam Ensis magnus shells: current status and projected acidification scenarios’Effects of ocean acidification and ocean warming on the behavior and physiology of a subarctic, intertidal grazer
Published 24 May 2023 Science ClosedTags: biological response, laboratory, mollusks, multiple factors, performance, physiology, temperature
The global ocean is expected to both acidify and warm concurrently; thus, multiple-stressor manipulative experimentation is an emergent area of study that ultimately aims to examine the individual and interactive effects of these factors on marine organisms. We characterized the physiological responses to acidification and warming of the intertidal grazer Lottia scutum, and examined how these ocean change variables influenced predator-prey dynamics with Evasterias troschelii, a key sea star predator. Specifically, we conducted a laboratory experiment where we exposed limpets to factorial combinations of temperature (11 and 15°C) and pH (7.6 and 8.0), and measured effects on thermal tolerance, metabolic rate, cortisol concentrations, and behavioral responses to the predator. We found that ocean warming (OW) decreased the critical thermal maxima (CTmax) and increased cortisol levels in L. scutum, whereas ocean acidification (OA) increased the mass-specific metabolic rate in this species. Additionally, we found that there was no significant effect of OA or OW on the anti-predator behavior of L. scutum when exposed to E. troschelii. These results highlight the need for future studies to integrate multidisciplinary experimental designs (i.e. behavior and physiology) that span multiple levels of biological organization to make ecologically relevant predictions for how marine organisms will respond to ocean change.
Continue reading ‘Effects of ocean acidification and ocean warming on the behavior and physiology of a subarctic, intertidal grazer’Long-term physiological responses to combined ocean acidification and warming show energetic trade-offs in an asterinid starfish
Published 22 May 2023 Science ClosedTags: biological response, calcification, echinoderms, laboratory, mortality, multiple factors, North Atlantic, performance, physiology, temperature
While organismal responses to climate change and ocean acidification are increasingly documented, longer-term (> a few weeks) experiments with marine organisms are still sparse. However, such experiments are crucial for assessing potential acclimatization mechanisms, as well as predicting species-specific responses to environmental change. Here, we assess the combined effects of elevated pCO2 and temperature on organismal metabolism, mortality, righting activity, and calcification of the coral reef-associated starfish Aquilonastra yairi. Specimens were incubated at two temperature levels (27 °C and 32 °C) crossed with three pCO2 regimes (455 µatm, 1052 µatm, and 2066 µatm) for 90 days. At the end of the experiment, mortality was not altered by temperature and pCO2 treatments. Elevated temperature alone increased metabolic rate, accelerated righting activity, and caused a decline in calcification rate, while high pCO2 increased metabolic rate and reduced calcification rate, but did not affect the righting activity. We document that temperature is the main stressor regulating starfish physiology. However, the combination of high temperature and high pCO2 showed nonlinear and potentially synergistic effects on organismal physiology (e.g., metabolic rate), where the elevated temperature allowed the starfish to better cope with the adverse effect of high pCO2 concentration (low pH) on calcification and reduced skeletal dissolution (antagonistic interactive effects) interpreted as a result of energetic trade-offs.
Continue reading ‘Long-term physiological responses to combined ocean acidification and warming show energetic trade-offs in an asterinid starfish’Warmer and more acidic conditions enhance performance of an endemic low shore gastropod
Published 17 May 2023 Science ClosedTags: adaptation, biological response, laboratory, mollusks, multiple factors, otherprocess, physiology, temperature
Changing ocean temperatures are predicted to challenge marine organisms, especially when combined with other factors, such as ocean acidification. Acclimation, as a form of phenotypic plasticity, can however, moderate the consequences of changing environments for biota. Our understanding of how altered temperature and acidification together influence species acclimation responses is, however, limited compared to responses to single stressors. This study investigated how temperature and acidification affected the thermal tolerance and righting speed of the Girdled Dogwhelk, Trochia cingulata (Linnaeus, 1771). Whelks were acclimated for two weeks to combinations of three temperatures (11°C: cold, 13°C: moderate and 15°C: warm) and two pH regimes (8.0: moderate and 7.5: acidic). We measured the temperature sensitivity of righting response by generating thermal performance curves from individual data collected at seven test temperatures and determined critical thermal minima (CTmin) and maxima (CTmax). We found that T. cingulata has a broad basal thermal tolerance range (∼38°C) and after acclimation to the warm temperature regime, both the optimal temperature for maximum righting speed and CTmax increased. Contrary to predictions, acidification did not narrow this population’s thermal tolerance but increased CTmax. These plastic responses are likely driven by the predictable exposure to temperature extremes measured in the field which originate from the local tidal cycle and the periodic acidification associated with ocean upwelling in the region. This acclimation ability suggests that T. cingulata has at least some capacity to buffer the thermal changes and increased acidification predicted to occur with climate change.
Continue reading ‘Warmer and more acidic conditions enhance performance of an endemic low shore gastropod’Impacts of ocean acidification and warming on post-larval growth and metabolism in two populations of the great scallop (Pecten maximus L.)
Published 17 May 2023 Science ClosedTags: biological response, field, molecular biology, mollusks, morphology, mortality, multiple factors, North Atlantic, physiology, reproduction, temperature
Ocean acidification and warming are key stressors for many marine organisms. Some organisms display physiological acclimatisation or plasticity, but this may vary across species ranges, especially if populations are adapted to local climatic conditions. Understanding how acclimatisation potential varies among populations is therefore important in predicting species responses to climate change. We carried out a common garden experiment to investigate how different populations of the economically important great scallop (Pecten maximus) from France and Norway responded to variation in temperature and pCO2 concentration. After acclimation, post-larval scallops (spat) were reared for 31 days at one of two temperatures (13°C and 19°C) under either ambient or elevated pCO2 (pH 8.0 and pH 7.7). We combined measures of proteomic, metabolic, and phenotypic traits to produce an integrative picture of how physiological plasticity varies between the populations. The proteome of French spat showed significant sensitivity to environmental variation, with 12 metabolic, structural and stress-response proteins responding to temperature and/or pCO2. Principal component analysis revealed seven energy metabolism proteins in French spat that were consistent with countering ROS stress under elevated temperature. Oxygen uptake in French spat did not change under elevated temperature, but increased under elevated pCO2. In contrast, Norwegian spat reduced oxygen uptake under both elevated temperature and pCO2. Metabolic plasticity seemingly allowed French scallops to maintain greater energy availability for growth than Norwegian spat. However, increased physiological plasticity and growth in French spat may come at a cost, as French (but not Norwegian) spat showed reduced survival under elevated temperature.
Continue reading ‘Impacts of ocean acidification and warming on post-larval growth and metabolism in two populations of the great scallop (Pecten maximus L.) ‘
