Intertidal organisms must tolerate daily fluctuations in environmental parameters, and repeated exposure to co-occurring conditions may result in tolerance to multiple stressors correlating. The intertidal copepod Tigriopus californicus experiences diurnal variation in dissolved oxygen levels and pH as the opposing processes of photosynthesis and cellular respiration lead to coordinated highs during the day and lows at night. While environmental parameters with overlapping spatial gradients frequently result in correlated traits, less attention has been given to exploring temporally correlated stressors. We investigated whether hypoxia tolerance correlates with low pH tolerance by separately testing the hypoxia and low pH stress tolerance separately of 6 genetically differentiated populations of T. californicus. We independently checked for similarities in tolerance for each of the two stressors by latitude, sex, size, and time since collection as predictors. We found that although hypoxia tolerance correlated with latitude, low pH tolerance did not, and no predictor was significant for both stressors. We concluded that temporally coordinated exposure to low pH and low oxygen did not result in populations developing equivalent tolerance for both. Although climate change alters several environmental variables simultaneously, organisms’ abilities to tolerate these changes may not be similarly coupled.
Continue reading ‘Hypoxia tolerance, but not low pH tolerance, is associated with a latitudinal cline across populations of Tigriopus californicus’Posts Tagged 'zooplankton'
Hypoxia tolerance, but not low pH tolerance, is associated with a latitudinal cline across populations of Tigriopus californicus
Published 6 April 2023 Science ClosedTags: adaptation, biological response, crustaceans, field, laboratory, morphology, mortality, multiple factors, North Pacific, otherprocess, oxygen, zooplankton
Assessing the impact of ocean acidification: a methods comparison of SEM, CT and light microscopy on pteropod shells
Published 31 March 2023 Science ClosedTags: biological response, dissolution, laboratory, methods, mollusks, morphology, North Atlantic, North Pacific, zooplankton
Since the onset of the Industrial Revolution, the world’s oceans have absorbed approximately one third of all anthropogenic CO2 emissions and are experiencing acidification as a result. Pteropods are a marine group of snails that are vulnerable to acidification due to their thin shells composed of aragonite, which is 50% more soluble than calcite. Due to their vulnerability and ubiquity throughout the world’s oceans, pteropods are considered bioindicators of ocean acidification; their responses include decreased size, reduced shell thickness, and increased shell dissolution. Shell dissolution has been measured using a variety of metrics involving light microscopy, scanning electron microscopy (SEM), and computed tomography (CT). Assessing which method(s) effectively capture acidification’s impact on pteropod shells is still an active area of research. While CT and SEM metrics offer high resolution imaging, these analyses are cost- and time-intensive relative to light microscopy analyses and may be inaccessible for ocean monitoring projects and research. This research compares light microscopy, CT, and SEM shell dissolution metrics across three pteropod species: Limacina helicina, Limacina retroversa, and Heliconoides inflatus. Sourced from multiple localities, these taxa lived in tropical to subpolar environments and were exposed to varying aragonite saturations states due to stark oceanographic differences in these environments. Specimens were evaluated using light microscopy for the Limacina Dissolution Index (LDX), using SEM for average and maximum dissolution type, and using CT for shell thickness. Spearman correlation tests were run among the dissolution metrics within each species dataset and significance was assessed both before and viii after Bonferroni correction. Before Bonferroni correction, LDX and SEM average dissolution type were highly correlated for both the Limacina retroversa (rho = 0.81, p > 0.001) and Heliconoides inflatus (rho = 0.79, p > 0.001) datasets, and remained significant after Bonferroni correction. For Limacina retroversa, LDX was also significantly correlated to SEM maximum dissolution type (rho = 0.77, p > 0.001). The CT metrics for shell thickness were not significantly correlated to any other dissolution metrics for any species. However, severely dissolved (type 3) areas apparent in SEM were also visually discernible in CT thickness heatmaps. Although the genera Heliconoides and Limacina have different shell microstructures, the relationship between LDX and SEM average dissolution type did not vary by species. Additionally, the Heliconoides inflatus specimens were sourced from both the aragonite-undersaturated California Current and the aragonite-oversaturated Cariaco Basin; however, the differing localities and their respective oceanographic conditions did not have a significant influence on the relationship between LDX and SEM average dissolution. Overall, these findings show that the cheaper and faster LDX method, which needs only a light microscope, is a promising method for detecting dissolution resulting from ocean acidification across multiple species and oceanographic conditions.
Continue reading ‘Assessing the impact of ocean acidification: a methods comparison of SEM, CT and light microscopy on pteropod shells’Ocean acidification and warming modify stimulatory benthos effects on sediment functioning: an experimental study on two ecosystem engineers
Published 17 March 2023 Science ClosedTags: biological response, laboratory, mollusks, mortality, multiple factors, North Atlantic, physiology, sediment, temperature, zooplankton
Many macrofauna have a stimulatory effect on sediment functioning through their burrowing, feeding and irrigation activities. Here, we investigated the single and combined effect of ocean acidification and warming on the stimulatory effect of two key-species inhabiting sandy seabeds in the Southern Bight of the North Sea; the bivalve Abra alba and the polychaete Lanice conchilega. The species were separately incubated in natural sediment in the laboratory under ambient, low pH (pH: -0.3), warm (T: + 3°C) and mimicked climate change (pH: -0.3, T: +3°C) conditions. After six weeks of incubation, nutrient and oxygen exchange were measured at the sediment-water interface to estimate aerobic sediment metabolism and nitrogen cycling. Both species facilitate sediment community oxygen consumption, nitrification and denitrification under ambient conditions. The stimulatory effect of A. alba disappeared in a low pH environment and decreased over time in the warmer treatments along with increased mortality. In contrast, L. conchilega stimulated sediment biogeochemical cycling more when seawater becomes acidified (+ 8 to 41%, depending on the function) but warming had no effect. We explain these species-specific climate change effects by different behavioral and physiological coping strategies that cascade on to sediment biogeochemical cycling, especially through altered oxygenation the sediment matrix.
Continue reading ‘Ocean acidification and warming modify stimulatory benthos effects on sediment functioning: an experimental study on two ecosystem engineers’Nanoplastics induce epigenetic signatures of transgenerational impairments associated with reproduction in copepods under ocean acidification
Published 15 March 2023 Science ClosedTags: biological response, crustaceans, laboratory, molecular biology, multiple factors, North Pacific, reproduction, toxicants, zooplankton
Ocean acidification (OA) is one of many major global climate changes that pose a variety of risks to marine ecosystems in different ways. Meanwhile, there is growing concern about how nanoplastics (NPs) affect marine ecosystems. Combined exposure of marine organisms to OA and NPs is inevitable, but their interactive effects remain poorly understood. In this study, we investigated the multi- and transgenerational toxicity of NPs on copepods under OA conditions for ten generations. The findings revealed that OA and NPs have a synergistic negative effect on copepod reproduction across generations. In particular, the transgenerational groups showed reproductive impairments in the F1 and F2 generations (F1T and F2T), even though they were never exposed to NPs. Moreover, our epigenetic examinations demonstrated that the observed intergenerational reproductive impairments are associated with differential methylation patterns of specific genes, suggesting that the interaction of OA and NPs can pose a significant threat to the sustainability of copepod populations through epigenetic modifications. Overall, our findings provide valuable insight into the intergenerational toxicity and underlying molecular mechanisms of responses to NPs under OA conditions.
Continue reading ‘Nanoplastics induce epigenetic signatures of transgenerational impairments associated with reproduction in copepods under ocean acidification’The multi-generational effect of seawater acidification on larval development, reproduction, ingestion rate, and ATPase activity of Tigriopus japonicus Mori, 1938
Published 13 March 2023 Science ClosedTags: biological response, crustaceans, North Pacific, performance, physiology, reproduction, zooplankton
Ocean acidification threatens marine organisms continuously. To ascertain if adaptation of marine species to ocean acidification enhanced over multiple generations, we studied the transgenerational effects of ocean acidification on the development, reproduction, ingestion rate, and ATPase activity of a copepod Tigriopus japonicus Mori, 1938. In the first mode, individuals were exposed to either one of the pH levels (8.1 (control), 7.7, 7.3) for five successive generations. In the second mode, each successive generation was exposed to a lower pH level (pH levels: 8.1, 7.9, 7.7, 7.5, 7.3). After prolonged exposure to a constant seawater acidification level, the capacity to adapt to the stress increased. However, when exposed to seawater of descending pH, the detrimental effects gradually increased. Energy allocated to development and reproduction was reduced although the ingestion rate continued to improve in successive generations. Therefore, ongoing ocean acidification might lower the energy transfer of copepods to higher trophic levels.
Continue reading ‘The multi-generational effect of seawater acidification on larval development, reproduction, ingestion rate, and ATPase activity of Tigriopus japonicus Mori, 1938’Ocean acidification-mediated food chain transfer of polonium between primary producers and consumers
Published 7 March 2023 Science ClosedTags: biological response, crustaceans, laboratory, morphology, multiple factors, physiology, phytoplankton, toxicants, zooplankton
Phytoplankton and zooplankton are key marine components that play an important role in metal distribution through a food web transfer. An increased phytoplankton concentration as a result of ocean acidification and warming are well-established, along with the fact that phytoplankton biomagnify 210Po by 3–4 orders of magnitude compared to the seawater concentration. This experimental study is carried out to better understand the transfer of polonium between primary producers and consumers. The experimental produced data highlight the complex interaction between the polonium concentration in zooplankton food, i.e. phytoplankton, its excretion via defecated fecal pellets, and its bioaccumulation at ambient seawater pH and a lower pH of 7.7, typical of ocean acidification scenarios in the open ocean. The mass of copepods recovered was 11% less: 7.7 pH compared to 8.2. The effects of copepod species (n = 3), microalgae species (n = 3), pH (n = 2), and time (n = 4) on the polonium activity in the fecal pellets (expressed as % of the total activity introduced through feeding) was tested using an ANOVA 4. With the exception of time (model: F20, 215 = 176.84, p < 0.001; time: F3 = 1.76, p = 0.16), all tested parameters had an impact on the polonium activity (copepod species: F2 = 169.15, p < 0.0001; algae species: F2 = 10.21, p < 0.0001; pH: F1 = 9.85, p = 0.002) with complex interactions (copepod x algae: F2 = 19.48, p < 0.0001; copepod x pH: F2 = 10.54, p < 0.0001; algae x pH: F2 = 4.87, p = 0.009). The experimental data underpin the hypothesis that metal bioavailability and bioaccumulation will be enhanced in secondary consumers such as crustacean zooplankton due to ocean acidification.
Continue reading ‘Ocean acidification-mediated food chain transfer of polonium between primary producers and consumers’Investigation of the molecular mechanisms which contribute to the survival of the polychaete Platynereis spp. under ocean acidification conditions in the CO2 vent system of Ischia Island (Italy)
Published 9 February 2023 Science ClosedTags: biological response, field, molecular biology, physiology, vents, zooplankton
The continuous increase of CO2 emissions in the atmosphere due to anthropogenic activities is one of the most important factors that contribute to Climate Change and generates the phenomenon known as Ocean Acidification (OA). Research conducted at the CO2 vents of Castello Aragonese (Ischia, Italy), which represents a natural laboratory for the study of OA, demonstrated that some organisms, such as polychaetes, thrive under acidified conditions through different adaptation mechanisms. Some functional and ecological traits promoting tolerance to acidification in these organisms have been identified, while the molecular and physiological mechanisms underlying acclimatisation or genetic adaptation are still largely unknown. Therefore, in this study we investigated epigenetic traits, as histone acetylation and methylation, in Platynereis spp. individuals coming from the Castello vent, and from a nearby control site, in two different periods of the year (November-June). Untargeted metabolomics analysis was also carried out in specimens from the two sites. We found a different profile of acetylation of H2B histone in the control site compared to the vent as a function of the sampling period. Metabolomic analysis showed clear separation in the pattern of metabolites in polychaetes from the control site with respect to those from the Castello vent. Specifically, a significant reduction of lipid/sterols and nucleosides was measured in polychaetes from the vent. Overall results contribute to better understand the potential metabolic pathways involved in the tolerance to OA.
Continue reading ‘Investigation of the molecular mechanisms which contribute to the survival of the polychaete Platynereis spp. under ocean acidification conditions in the CO2 vent system of Ischia Island (Italy)’Ocean acidification causes fundamental changes in the cellular metabolism of the Arctic copepod Calanus glacialis as detected by metabolomic analysis
Published 23 January 2023 Science ClosedTags: biological response, crustaceans, molecular biology, physiology, zooplankton
Using a targeted metabolomic approach we investigated the effects of low seawater pH on energy metabolism in two late copepodite stages (CIV and CV) of the keystone Arctic copepod species Calanus glacialis. Exposure to decreasing seawater pH (from 8.0 to 7.0) caused increased ATP, ADP and NAD+ and decreased AMP concentrations in stage CIV, and increased ATP and phospho-L-arginine and decreased AMP concentrations in stage CV. Metabolic pathway enrichment analysis showed enrichment of the TCA cycle and a range of amino acid metabolic pathways in both stages. Concentrations of lactate, malate, fumarate and alpha-ketoglutarate (all involved in the TCA cycle) increased in stage CIV, whereas only alpha-ketoglutarate increased in stage CV. Based on the pattern of concentration changes in glucose, pyruvate, TCA cycle metabolites, and free amino acids, we hypothesise that ocean acidification will lead to a shift in energy production from carbohydrate metabolism in the glycolysis toward amino acid metabolism in the TCA cycle and oxidative phosphorylation in stage CIV. In stage CV, concentrations of most of the analysed free fatty acids increased, suggesting in particular that ocean acidification increases the metabolism of stored wax esters in this stage. Moreover, aminoacyl-tRNA biosynthesis was enriched in both stages indicating increased enzyme production to handle low pH stress.
Continue reading ‘Ocean acidification causes fundamental changes in the cellular metabolism of the Arctic copepod Calanus glacialis as detected by metabolomic analysis’Can marine hydrothermal vents be used as natural laboratories to study global change effects on zooplankton in a future ocean?
Published 23 January 2023 Science ClosedTags: biological response, methods, review, vents, zooplankton
It is claimed that oceanic hydrothermal vents (HVs), particularly the shallow water ones, offer particular advantages to better understand the effects of future climate and other global change on oceanic biota. Marine hydrothermal vents (HVs) are extreme oceanic environments that are similar to projected climate changes of the earth system ocean (e.g., changes of circulation patterns, elevated temperature, low pH, increased turbidity, increased bioavailability of toxic compounds. Studies on hydrothermal vent organisms may fill knowledge gaps of environmental and evolutionary adaptations to this extreme oceanic environment. In the present contribution we evaluate whether hydrothermal vents can be used as natural laboratories for a better understanding of zooplankton ecology under a global change scenario.
Continue reading ‘Can marine hydrothermal vents be used as natural laboratories to study global change effects on zooplankton in a future ocean?’A positive temperature-dependent effect of elevated CO2 on growth and lipid accumulation in the planktonic copepod, Calanus finmarchicus
Published 23 December 2022 Science ClosedTags: biological response, crustaceans, laboratory, morphology, multiple factors, North Atlantic, physiology, reproduction, temperature, zooplankton
Calanus finmarchicus were reared from eggs to adults at 12°C and 16°C with non-limiting food in combination with ambient (600 μatm) and high (1100 μatm) pCO2. These conditions are likely to be encountered by the species at the southern margins of its biogeographical range by the end of the century. Dry weight (DW), carbon (C) and nitrogen (N) mass, oil-sac volume (OSV), fatty acid composition (FA), and oxygen consumption rates (OCR) were measured on newly molted stage CV copepodites and recently molted adult females. By focusing our measurements on these precise events in the life cycle, we were able to obtain a more accurate comparison of growth and respiration across treatments. Copepods raised at 12°C had a significantly greater DW, OSV, and C and N mass than those raised at 16°C High pCO2, independent of temperature, was associated with a further increase in the DW and C content of the copepods. Interactive effects of temperature and pCO2 resulted in a larger OSV at low temperature and high pCO2. Mass-specific respiration rates were significantly lower at lower temperatures and elevated pCO2 suggesting that the increase in mass (DW, C, and OSV) resulted from reduced metabolic cost. The composition of fatty acids in the copepods varied mainly with temperature. Two fatty acids varied with pCO2: 16:0 tended to decrease with higher pCO2 and 18:3n−3 tended to increase with higher pCO2. These observations suggest that elevated pCO2/lower pH in future oceans may have a beneficial effect on C. finmarchicus.
Continue reading ‘A positive temperature-dependent effect of elevated CO2 on growth and lipid accumulation in the planktonic copepod, Calanus finmarchicus’Shelled pteropod abundance and distribution across the Mediterranean Sea during spring
Published 16 December 2022 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, field, Mediterranean, mollusks, otherprocess, zooplankton
Highlights
- First estimate of pteropod distribution across the Mediterranean Sea in spring.
- Highest abundance recorded in the oligotrophic Eastern Mediterranean basin.
- Temperature, aragonite saturation, oxygen and salinity main drivers of distribution.
- Pteropods and planktic foraminifera are inversely distributed in the Med Sea.
Abstract
Thecosome pteropods are a dominant group of calcifying pelagic molluscs and an important component of the food web. In this study, we characterise spring pteropod distribution throughout the Mediterranean Sea, an understudied region for this common group of marine calcifying organisms. This semi-enclosed sea is rapidly changing under climatic and anthropogenic forcings. The presence of surface water biogeochemical gradients from the Atlantic Ocean/Gibraltar Strait to the Eastern Mediterranean Sea allowed us to investigate pteropod distribution and their ecological preferences. In the ultra-oligotrophic Eastern Mediterranean Sea, we found the mean upper 200 m pteropod standing stock of 2.13 ind. m-3 was approximately 5x greater than the Western basin (mean 0.42 ind. m-3). Where standing stocks were high, pteropods appeared largely in the same family grouping belonging to Limacinidae. Temperature, O2 concentration, salinity, and aragonite saturation (Ωar) explain 96% of the observed variations in the community structure at the time of sampling, suggesting that pteropods might show a preference for environmental conditions with a lower energetic physiological demand. We also document that pteropods and planktonic foraminifera have an opposite geographical distribution in the Mediterranean Sea. Our findings indicate that in specific pelagic ultra-oligotrophic conditions, such as the Eastern Mediterranean Sea, different feeding strategies could play an important role in regulating calcifying zooplankton distribution.
Continue reading ‘Shelled pteropod abundance and distribution across the Mediterranean Sea during spring’Cascading effects augment the direct impact of CO2 on phytoplankton growth in a biogeochemical model
Published 11 November 2022 Science ClosedTags: abundance, biological response, BRcommunity, communitymodeling, globalmodeling, light, modeling, multiple factors, nutrients, otherprocess, phytoplankton, predation, temperature, zooplankton
Atmospheric and oceanic CO2 concentrations are rising at an unprecedented rate. Laboratory studies indicate a positive effect of rising CO2 on phytoplankton growth until an optimum is reached, after which the negative impact of accompanying acidification dominates. Here, we implemented carbonate system sensitivities of phytoplankton growth into our global biogeochemical model FESOM-REcoM and accounted explicitly for coccolithophores as the group most sensitive to CO2. In idealized simulations in which solely the atmospheric CO2 mixing ratio was modified, changes in competitive fitness and biomass are not only caused by the direct effects of CO2, but also by indirect effects via nutrient and light limitation as well as grazing. These cascading effects can both amplify or dampen phytoplankton responses to changing ocean pCO2 levels. For example, coccolithophore growth is negatively affected both directly by future pCO2 and indirectly by changes in light limitation, but these effects are compensated by a weakened nutrient limitation resulting from the decrease in small-phytoplankton biomass. In the Southern Ocean, future pCO2 decreases small-phytoplankton biomass and hereby the preferred prey of zooplankton, which reduces the grazing pressure on diatoms and allows them to proliferate more strongly. In simulations that encompass CO2-driven warming and acidification, our model reveals that recent observed changes in North Atlantic coccolithophore biomass are driven primarily by warming and not by CO2. Our results highlight that CO2 can change the effects of other environmental drivers on phytoplankton growth, and that cascading effects may play an important role in projections of future net primary production.
Continue reading ‘Cascading effects augment the direct impact of CO2 on phytoplankton growth in a biogeochemical model’Effects of hypoxia and acidification on Calanus pacificus: behavioral changes in response to stressful environments
Published 9 November 2022 Science ClosedTags: biological response, crustaceans, laboratory, mortality, multiple factors, oxygen, performance, zooplankton
Copepods, which play major roles in marine food webs and biogeochemical cycling, frequently undergo diel vertical migration (DVM), swimming downwards during the day to avoid visual predation and upwards at night to feed. Natural water columns that are stratified with chemical stressors at depth, such as hypoxia and acidification, are increasing with climate change. Understanding behavioral responses of copepods to these stresses—in particular, whether copepods alter their natural migration—is important to anticipating impacts of climate change on marine ecosystems. We conducted laboratory experiments using stratified water columns to measure the effects of bottom water hypoxia and pH on mortality, distribution, and swimming behaviors of the calanoid copepod Calanus pacificus. When exposed to hypoxic (0.65 mg O2 l-1) bottom waters, the height of C. pacificus from the bottom increased 20% within hypoxic columns, and swimming speed decreased 46% at the bottom of hypoxic columns and increased 12% above hypoxic waters. When exposed to low pH (7.48) bottom waters, swimming speeds decreased by 8 and 9% at the base of the tanks and above acidic waters, respectively. Additionally, we found a 118% increase in ‘moribund’ (immobile on the bottom) copepods when exposed to hypoxic, but not acidic, bottom waters. Some swimming statistics differed between copepods collected from sites with versus without historical hypoxia and acidity. Observed responses suggest potential mechanisms underlying in situ changes in copepod population distributions when exposed to chemical stressors at depth.
Continue reading ‘Effects of hypoxia and acidification on Calanus pacificus: behavioral changes in response to stressful environments’Marine heatwave impacts on newly-hatched planktonic larvae of an estuarine crab
Published 25 October 2022 Science ClosedTags: biological response, crustaceans, laboratory, mortality, multiple factors, physiology, temperature, zooplankton
Highlights
- Larvae survival was affected by temperature increase regardless of pH conditions.
- Larvae heart beating and abdominal contractions were affected by temperature and pH.
- Over the past 38 years Santos/São Vicente coast had a mean SST increase of 0.85 °C.
- Higher intensity and duration of heatwaves are expected to reduce larval recruitment.
Abstract
Climate change is imposing constant and more severe environmental challenges to coastal and marine species. Regional climate and species acclimation capacity determine the communities’ ecological response to stressors. Marine heatwave events are of serious threat to species fitness and survivorship, even more to the sensitive early-history stages of ectotherms. By combining modeled regional historical data and climate change predictions with manipulative experiments, we evaluated the potential impact of marine heatwaves in a widespread and abundant planktonic larvae of the fiddler crab Leptuca thayeri. Larvae survival was affected by temperature increase with lowest survival probability under higher temperature treatments regardless of pH conditions. Larval physiology was affected by both temperature increase and pH conditions. With heatwaves becoming more frequent, hotter, and lasting longer in the region, we could expect potential reductions in the larval recruitment and stocks with cascade ecological negative effects on estuarine habitats.
Continue reading ‘Marine heatwave impacts on newly-hatched planktonic larvae of an estuarine crab’Epigenetic plasticity enables copepods to cope with ocean acidification
Published 13 October 2022 Science ClosedTags: biological response, crustaceans, laboratory, molecular biology, morphology, North Pacific, reproduction, zooplankton
Plasticity enhances species fitness and survival under climate change. Ocean acidification poses a potential threat to copepods, a major zooplankton group that serves as a key link between the lower and higher trophic levels in the marine environment, yet the mechanisms underlying different adaptive responses remain poorly understood. Here we show that although elevated CO2 can exert negative effects on reproduction of Paracyclopina nana, multigenerational plasticity can enable recovery after three generations. By integrating the methylome and transcriptome with the draft genome and undertaking DNA methylation treatments, we demonstrate the vital role of epigenetic modifications in ocean acidification responses and identify regions associated with reproductive resilience. Our results demonstrate that DNA methylation might play an important role in enhancing species fitness of copepods and that failing to consider phenotypic plasticity could lead to overestimation of species’ vulnerabilities.
Continue reading ‘Epigenetic plasticity enables copepods to cope with ocean acidification’Experimental evolution reveals the synergistic genomic mechanisms of adaptation to ocean warming and acidification in a marine copepod
Published 27 September 2022 Science ClosedTags: adaptation, biological response, crustaceans, molecular biology, multiple factors, otherprocess, physiology, temperature, zooplankton
Metazoan adaptation to global change relies on selection of standing genetic variation. Determining the extent to which this variation exists in natural populations, particularly for responses to simultaneous stressors, is essential to make accurate predictions for persistence in future conditions. Here, we identified the genetic variation enabling the copepod Acartia tonsa to adapt to experimental ocean warming, acidification, and combined ocean warming and acidification (OWA) over 25 generations of continual selection. Replicate populations showed a consistent polygenic response to each condition, targeting an array of adaptive mechanisms including cellular homeostasis, development, and stress response. We used a genome-wide covariance approach to partition the allelic changes into three categories: selection, drift and replicate-specific selection, and laboratory adaptation responses. The majority of allele frequency change in warming (57%) and OWA (63%) was driven by shared selection pressures across replicates, but this effect was weaker under acidification alone (20%). OWA and warming shared 37% of their response to selection but OWA and acidification shared just 1%, indicating that warming is the dominant driver of selection in OWA. Despite the dominance of warming, the interaction with acidification was still critical as the OWA selection response was highly synergistic with 47% of the allelic selection response unique from either individual treatment. These results disentangle how genomic targets of selection differ between single and multiple stressors and demonstrate the complexity that nonadditive multiple stressors will contribute to predictions of adaptation to complex environmental shifts caused by global change.
Continue reading ‘Experimental evolution reveals the synergistic genomic mechanisms of adaptation to ocean warming and acidification in a marine copepod’Intergenerational effects of ocean acidification on reproductive traits of an estuarine copepod
Published 19 September 2022 Science ClosedTags: biological response, crustaceans, laboratory, mortality, North Atlantic, reproduction, zooplankton
Copepods are an important part of the marine food web because of their high biomass productivity and nutrient turnover rate compared to other zooplankton in the marine ecosystem. Despite their great ecological role in the ocean, there is only limited information available on the consequences of ocean acidification (OA) induced by the future increase in CO2 on the planet. More specifically, there is almost no information about the impact of OA on the European copepod Calanipeda aquaedulcis Kritschagin, 1873. Therefore, the present investigation hypothesized that OA would not produce negative multigenerational effects on the survival and reproductive performance of this copepod species. Here we assessed, the multigenerational (F1 and F2) effect of OA on eight important reproductive traits (maturity, prosome length, fertility, egg release, hatching success, survival rate, reproductive performance, and the total number of adults per generation). For this study, C. aquaedulcis were collected from the Guadalquivir River (southwest of Spain) and were exposed to four different pH gradients (pH 8.1 as control and pH 7.5, 7.0, 6.5 as acidified conditions) to mimic the future seawater acidification scenarios. The survival rate from nauplius to adult, C. aquaedulcis was significantly reduced by pHs and across generations. Besides, results also indicated that there were marked effects on fertility, reflected by a significantly lower number of eggs per female in each generation. Similarly, hatching success also showed a decreasing pattern towards low pH, and importantly, F1 females had lower hatching success than F0 females. While a beneficial parental effect was detected in the offspring in response to OA, it was insufficient to offset the negative effects caused by it. The findings presented here appear to have ecological significance, as decreasing the reproductive performance of copepods may have a negative impact on the marine food web, as ichthyofaunal feeding and growth are heavily reliant on this component of the food web.
Continue reading ‘Intergenerational effects of ocean acidification on reproductive traits of an estuarine copepod’Membrane lipid sensitivity to ocean warming and acidification poses a severe threat to Arctic pteropods
Published 12 September 2022 Science ClosedTags: Arctic, biological response, laboratory, mollusks, mortality, multiple factors, physiology, temperature, zooplankton
Ocean warming and acidification will be most pronounced in the Arctic. Both phenomena severely threaten thecosome pteropods (holoplanktonic marine gastropods) by reducing their survival (warming) and causing the dissolution of their aragonitic shell (acidification). Lipids, particularly phospholipids, play a major role in veligers and juveniles of the polar thecosome pteropod Limacina helicina comprising more than two-thirds of their total lipids. Membrane lipids (phospholipids) are important for the temperature acclimation of ectotherms. Hence, we experimentally investigated ocean warming and acidification effects on total lipids, lipid classes, and fatty acids of Arctic early-stage L. helicina. The temperature and pCO2 treatments chosen resembled Representative Concentration Pathway model scenarios for this century. We found a massive decrease in total lipids at elevated temperatures and at the highest CO2 concentration (1,100 μatm) of the in situ temperature. Clearly, temperature was the overriding factor. Total lipids were reduced by 47%–70%, mainly caused by a reduction of phospholipids by up to 60%. Further, based on pHT development in the incubation water of pteropods during the experiment, some evidence exists for metabolic downregulation in pteropods at high factor levels of temperature and pCO2. Consequently, the cell differentiation and energy balance of early-stage larvae were probably severely compromised. Comparison of our experimental with ‘wild’ organisms suggests phospholipid reduction to values clearly outside natural variability. Based on the well-known significance of phospholipids for membranogenesis, early development, and reproduction, negative warming effects on such a basal metabolic function may be a much more immediate threat for pteropods than so far anticipated shell dissolution effects due to acidification.
Continue reading ‘Membrane lipid sensitivity to ocean warming and acidification poses a severe threat to Arctic pteropods’
