Adaptive evolution and phenotypic plasticity will fuel resilience in the geologically unprecedented warming and acidification of the earth’s oceans, however, we have much to learn about the interactions and costs of these mechanisms of resilience. Here, using 20 generations of experimental evolution followed by three generations of reciprocal transplants, we investigated the relationship between adaptation and plasticity in the marine copepod, Acartia tonsa, in future global change conditions (high temperature and high CO2). We found parallel adaptation to global change conditions in genes related to stress response, gene expression regulation, actin regulation, developmental processes, and energy production. However, reciprocal transplantation showed that adaptation resulted in a loss of transcriptional plasticity, reduced fecundity, and reduced population growth when global change-adapted animals were returned to ambient conditions or reared in low food conditions. However, after three successive transplant generations, global change-adapted animals were able to match the ambient-adaptive transcriptional profile. Concurrent changes in allele frequencies and erosion of nucleotide diversity suggest that this recovery occurred via adaptation back to ancestral conditions. These results demonstrate that while plasticity facilitated initial survival in global change conditions, it eroded after 20 generations as populations adapted, limiting resilience to new stressors and previously benign environments.
Continue reading ‘Loss of transcriptional plasticity but sustained adaptive capacity after adaptation to global change conditions in a marine copepod’Posts Tagged 'zooplankton'
Loss of transcriptional plasticity but sustained adaptive capacity after adaptation to global change conditions in a marine copepod
Published 16 March 2022 Science ClosedTags: adaptation, biological response, crustaceans, laboratory, molecular biology, mortality, multiple factors, North Atlantic, otherprocess, physiology, reproduction, temperature, zooplankton
Effects of local acidification on benthic communities at shallow hydrothermal vents of the Aeolian Islands (Southern Tyrrhenian, Mediterranean Sea)
Published 10 March 2022 Science ClosedTags: field, laboratory, Mediterranean, sediment, vents, zooplankton
Simple Summary
Ocean acidification is causing major changes in marine ecosystems, with varying levels of impact depending on the region and habitat investigated. Here, we report noticeable changes in both meio- and macrobenthic assemblages at shallow hydrothermal vents located in the Mediterranean Sea. In general, the areas impacted by the vent fluids showed decrease in the abundance of several taxa and a shift in community composition, but with a clear biomass reduction evident only for macrofauna. CO2 emissions at shallow hydrothermal vents cause a progressive simplification of community structure and a general biodiversity decline due to the loss of the most sensitive meio- and macrofaunal taxa, which were replaced by the more tolerant groups, such as oligochaetes, or highly mobile species, able to escape from extreme conditions. Our results provide new insight on the tolerance of marine meio- and macrofaunal taxa to the extreme conditions generated by hydrothermal vent emissions in shallow-water ecosystems.
Abstract
The Aeolian Islands (Mediterranean Sea) host a unique hydrothermal system called the “Smoking Land” due to the presence of over 200 volcanic CO2-vents, resulting in water acidification phenomena and the creation of an acidified benthic environment. Here, we report the results of a study conducted at three sites located at ca. 16, 40, and 80 m of depth, and characterized by CO2 emissions to assess the effects of acidification on meio- and macrobenthic assemblages. Acidification caused significant changes in both meio- and macrofaunal assemblages, with a clear decrease in terms of abundance and a shift in community composition. A noticeable reduction in biomass was observed only for macrofauna. The most sensitive meiofaunal taxa were kinorhynchs and turbellarians that disappeared at the CO2 sites, while the abundance of halacarids and ostracods increased, possibly as a result of the larger food availability and the lower predatory pressures by the sensitive meiofaunal and macrofaunal taxa. Sediment acidification also causes the disappearance of more sensitive macrofaunal taxa, such as gastropods, and the increase in tolerant taxa such as oligochaetes. We conclude that the effects of shallow CO2-vents result in the progressive simplification of community structure and biodiversity loss due to the disappearance of the most sensitive meio- and macrofaunal taxa.
Continue reading ‘Effects of local acidification on benthic communities at shallow hydrothermal vents of the Aeolian Islands (Southern Tyrrhenian, Mediterranean Sea)’Ocean acidification induces distinct metabolic responses in subtropical zooplankton under oligotrophic conditions and after simulated upwelling
Published 11 January 2022 Science ClosedTags: algae, biological response, community composition, field, mesocosms, otherprocess, physiology, zooplankton
Highlights
- Effects of rising atmospheric CO2 on zooplankton were studied in coastal mesocosms.
- Mesozooplankton metabolism was more affected by elevated CO2 than microzooplankton.
- CO2-induced effects were more marked in eutrophic than in oligotrophic conditions.
- Elevated CO2 impacts the role of zooplankton on the carbon and nitrogen cycles.
Abstract
Ocean acidification (OA) is one of the most critical anthropogenic threats to marine ecosystems. While significant ecological responses of plankton communities to OA have been revealed mainly by small-scale laboratory approaches, the interactive effect of OA-related changes on zooplankton metabolism and their biogeochemical implications in the natural environment still remains less well understood. Here, we explore the responses of zooplankton respiration and ammonium excretion, two key processes in the nutrient cycling, to high pCO2 levels in a 9-week in situ mesocosm experiment conducted during the autumn oligotrophic season in the subtropical northeast Atlantic. By simulating an upwelling event halfway through the study, we further evaluated the combined effects of OA and nutrient availability on the physiology of micro-and mesozooplankton. OA conditions generally resulted in a reduction in the biomass-specific metabolic and enzymatic rates, particularly in the mesozooplankton community. The situation reversed after the nutrient-rich deep-water addition, which initially promoted a diatom bloom and increased heterotrophic activities in all mesocosms. Under high pCO2 conditions (>800 μatm), however, the nutrient fertilization triggered the proliferation of the harmful alga Vicicitus globosus, with important consequences for the metabolic performance of the two zooplankton size classes. Here, the zooplankton contribution to the remineralization of organic matter and nitrogen regeneration dropped by 30% and 24%, respectively, during the oligotrophic period, and by 40% and 70% during simulated upwelling. Overall, our results indicate a potential reduction in the biogeochemical role of zooplankton under future ocean conditions, with more evident effects on the large mesozooplankton and during high productivity events.
Continue reading ‘Ocean acidification induces distinct metabolic responses in subtropical zooplankton under oligotrophic conditions and after simulated upwelling’Under pressure: nanoplastics as a further stressor for sub-Antarctic pteropods already tackling ocean acidification
Published 4 January 2022 Science ClosedTags: Antarctic, biological response, laboratory, mollusks, mortality, multiple factors, toxicants, zooplankton
In the Southern Ocean (SO), plastic debris has already been found in waters and sediments. Nanoplastics (<1 μm) are expected to be as pervasive as their larger counterparts, but more harmful to biological systems, being able to enter cells and provoke toxicity. In the SO, (nano)plastic pollution occurs concomitantly with other environmental threats such as ocean acidification (OA), but the potential cumulative impact of these two challenges on SO marine ecosystems is still overlooked. Here the single and combined effects of nanoplastics and OA on the sub-Antarctic pteropod Limacina retroversa are investigated under laboratory conditions, using two surface charged polystyrene nanoparticles (PS NPs) as a proxy for nanoplastics. Sub-Antarctic pteropods are threatened by OA due to the sensitivity of their shells to changes in seawater carbonate chemistry. Short-term exposure (48 h) to PS NPs compromised the ability of pteropods to counteract OA stress, resulting in a negative effect on their survival. Our results highlights the importance of addressing plastic pollution in the context of climate change to identify realistic critical thresholds of SO pteropods.
Continue reading ‘Under pressure: nanoplastics as a further stressor for sub-Antarctic pteropods already tackling ocean acidification’Arctic planktonic calcifiers in a changing ocean – A study on recent planktonic foraminifera and shelled pteropods in the Fram Strait-Barents Sea region
Published 3 January 2022 Science ClosedTags: Arctic, biological response, BRcommunity, community composition, laboratory, mollusks, otherprocess, phytoplankton, zooplankton
The Arctic marine realm is being transformed due to the anthropogenically-induced climate change. In the Arctic, the effects of climate change are intensified due to polar amplification and have led to processes in the ocean such as sea-ice retreat, ocean acidification and the increased presence of boreal species referred to as ‘Atlantification’. This thesis presents rare investigations of marine calcifiers in the Fram Strait-Barents Sea region; planktonic foraminifera (Phylum Retaria) and the shelled pteropod Limacina helicina (Phylum Mollusca). There are few previous studies signifying several unknowns pertaining to their ecology and life cycles, and hence how they have and will continue to respond to climate change. The overarching aim of the thesis is to increase the knowledge of living planktonic foraminifera and pteropods in the Arctic, more specifically their distribution patterns, absolute and relative abundance, seasonality, diversity, ontogeny, and calcification. These studies are based on investigations from two dynamic areas; the Bjørnøyrenna Craters in the northern Barents Sea that is a site of intense methane seepage, and the Northeast Greenland Shelf where there is a rapid sea-ice reduction and interplay between Polar and Atlantic water masses. This thesis has shown that the Fram Strait-Barents Sea region is characterized by low species diversity of the planktonic foraminiferal faunas, where Neogloboquadrina pachyderma dominates in Polar Water and Turborotalita quinqueloba dominates in Atlantic Water. Our study areas have low standing stock of both planktonic foraminifera and pteropods in spring and a medium to high standing stock in summer. They have a distinct vertical shell density gradient and are not affected by intense methane seepage even in the relatively shallow Barents Sea. In terms recent impact of climate, there may be a decrease in the relative abundance of N. pachyderma on the Northeast Greenland shelf compared to studies from the 1990s, and sub-tropical species can be found in the Barents Sea. Furthermore, this thesis has helped in filling gaps in research into the impacts of ocean acidification in the Arctic, especially pertaining to methane release from dissociation of methane hydrates. Lastly, we have been able to show that planktonic foraminifera and pteropods in the same size class captured from the same location and depth interval have a wide range of shell densities. The same is also true for planktonic foraminifera found in surface sediments. These two points may complicate modern geochemical or ocean acidification studies as well as paleo-studies.
Continue reading ‘Arctic planktonic calcifiers in a changing ocean – A study on recent planktonic foraminifera and shelled pteropods in the Fram Strait-Barents Sea region’Gene expression and epigenetic responses of the marine Cladoceran, Evadne nordmanni, and the copepod, Acartia clausi, to elevated CO2
Published 2 December 2021 Science ClosedTags: biological response, BRcommunity, crustaceans, laboratory, molecular biology, North Atlantic, physiology, zooplankton
Characterizing the capacity of marine organisms to adapt to climate change related drivers (e.g., pCO2 and temperature), and the possible rate of this adaptation, is required to assess their resilience (or lack thereof) to these drivers. Several studies have hypothesized that epigenetic markers such as DNA methylation, histone modifications and noncoding RNAs, act as drivers of adaptation in marine organisms, especially corals. However, this hypothesis has not been tested in zooplankton, a keystone organism in marine food webs. The objective of this study is to test the hypothesis that acute ocean acidification (OA) exposure alters DNA methylation in two zooplanktonic species—copepods (Acartia clausii) and cladocerans (Evadne nordmanii). We exposed these two species to near-future OA conditions (400 and 900 ppm pCO2) for 24 h and assessed transcriptional and DNA methylation patterns using RNA sequencing and Reduced Representation Bisulfite Sequencing (RRBS). OA exposure caused differential expression of genes associated with energy metabolism, cytoskeletal and extracellular matrix functions, hypoxia and one-carbon metabolism. Similarly, OA exposure also caused altered DNA methylation patterns in both species but the effect of these changes on gene expression and physiological effects remains to be determined. The results from this study form the basis for studies investigating the potential role of epigenetic mechanisms in OA induced phenotypic plasticity and/or adaptive responses in zooplanktonic organisms.
Continue reading ‘Gene expression and epigenetic responses of the marine Cladoceran, Evadne nordmanni, and the copepod, Acartia clausi, to elevated CO2’Experimental evolution reveals the synergistic genomic mechanisms of adaptation to ocean warming and acidification in a marine copepod
Published 11 November 2021 Science ClosedTags: adaptation, biological response, crustaceans, molecular biology, otherprocess, zooplankton
Metazoan adaptation to global change will rely on selection of standing genetic variation. Determining the extent to which this variation exists in natural populations, particularly for responses to simultaneous stressors, is therefore essential to make accurate predictions for persistence in future conditions. Here, we identify the genetic variation enabling the copepod Acartia tonsa to adapt to experimental ocean warming, acidification, and combined ocean warming and acidification (OWA) conditions over 25 generations. Replicate populations showed a strong and 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 genomic changes into selection, drift, and lab adaptation and found that the majority of allele frequency change in warming (56%) and OWA (63%) was driven by selection but acidification was dominated by drift (66%). OWA and warming shared 37% of their response to selection but OWA and acidification shared just 1%. Accounting for lab adaptation was essential for not inflating a shared response to selection between all treatments. Finally, the mechanisms of adaptation in the multiple-stressor OWA conditions were not an additive product of warming and acidification, but rather a synergistic response where 47% of the allelic responses to selection were unique. These results are among the first to disentangle how the genomic targets of selection differ between single and multiple stressors and to demonstrate the complexity that non-additive multiple stressors will contribute to attempts to predict adaptive responses to complex environments.
Continue reading ‘Experimental evolution reveals the synergistic genomic mechanisms of adaptation to ocean warming and acidification in a marine copepod’Influence of global environmental change on plankton
Published 8 November 2021 Science ClosedTags: biological response, crustaceans, phytoplankton, review, zooplankton
Much has been published on the effects of ocean acidification on plankton since the original Royal Society 2005 report. In addition to direct effects on primary production, it is clear that ocean acidification also has profound consequences for biogeochemistry. Furthermore, although ocean acidification can have direct effects of on grazers such as copepods, acidification induces changes in nutritional value of phytoplankton which can be passed on up the food chain. There has also been recognition of the complexity of the interactions between elevated CO2 and other environmental factors and this has seen an upsurge in climate change research involving multifactorial experiments. In particular, the interaction of ocean acidification with global warming resulting from the increasing greenhouse effect has been investigated. There has also been research on acidification and warming effects in inland water plankton. These, combined with novel experimental techniques and long term studies of genetic adaptation, are providing better insights to plankton biology and communities in a future world.
Continue reading ‘Influence of global environmental change on plankton’Composition and dominance of edible and inedible phytoplankton predict responses of Baltic Sea summer communities to elevated temperature and CO2
Published 8 November 2021 Science ClosedTags: Baltic, biological response, community composition, crustaceans, laboratory, mesocosms, multiple factors, otherprocess, phytoplankton, prokaryotes, temperature, zooplankton
Previous studies with Baltic Sea phytoplankton combining elevated seawater temperature with CO2 revealed the importance of size trait-based analyses, in particular dividing the plankton into edible (>5 and <100 µm) and inedible (<5 and >100 µm) size classes for mesozoopankton grazers. While the edible phytoplankton responded predominantly negative to warming and the inedible group stayed unaffected or increased, independent from edibility most phytoplankton groups gained from CO2. Because the ratio between edible and inedible taxa changes profoundly over seasons, we investigated if community responses can be predicted according to the prevailing composition of edible and inedible groups. We experimentally explored the combined effects of elevated temperatures and CO2 concentrations on a late-summer Baltic Sea community. Total phytoplankton significantly increased in response to elevated CO2 in particular in combination with temperature, driven by a significant gain of the inedible <5 µm fraction and large filamentous cyanobacteria. Large flagellates disappeared. The edible group was low as usual in summer and decreased with both factors due to enhanced copepod grazing and overall decline of small flagellates. Our results emphasize that the responses of summer communities are complex, but can be predicted by the composition and dominance of size classes and groups.
Continue reading ‘Composition and dominance of edible and inedible phytoplankton predict responses of Baltic Sea summer communities to elevated temperature and CO2’Distribution and abundances of planktic foraminifera and shelled pteropods during the polar night in the sea-ice covered Northern Barents Sea
Published 25 October 2021 Science ClosedTags: Arctic, biological response, BRcommunity, chemistry, field, laboratory, mollusks, morphology, protists, zooplankton
Planktic foraminfera and shelled pteropods are important calcifying groups of zooplankton in all oceans. Their calcium carbonate shells are sensitive to changes in ocean carbonate chemistry predisposing them as an important indicator of ocean acidification. Moreover, planktic foraminfera and shelled pteropods contribute significantly to food webs and vertical flux of calcium carbonate in polar pelagic ecosystems. Here we provide, for the first time, information on the under-ice planktic foraminifera and shelled pteropod abundance, species composition and vertical distribution along a transect (82°–76°N) covering the Nansen Basin and the northern Barents Sea during the polar night in December 2019. The two groups of calcifiers were examined in different environments in the context of water masses, sea ice cover, and ocean chemistry (nutrients and carbonate system). The average abundance of planktic foraminifera under the sea-ice was low with the highest average abundance (2 ind. m–3) close to the sea-ice margin. The maximum abundances of planktic foraminifera were concentrated at 20–50 m depth (4 and 7 ind. m–3) in the Nansen Basin and at 80–100 m depth (13 ind. m–3) close to the sea-ice margin. The highest average abundance (13 ind. m–3) and the maximum abundance of pteropods (40 ind. m–3) were found in the surface Polar Water at 0–20 m depth with very low temperatures (–1.9 to –1°C), low salinity (<34.4) and relatively low aragonite saturation of 1.43–1.68. The lowest aragonite saturation (<1.3) was observed in the bottom water in the northern Barents Sea. The species distribution of these calcifiers reflected the water mass distribution with subpolar species at locations and depths influenced by warm and saline Atlantic Water, and polar species in very cold and less saline Polar Water. The population of planktic foraminifera was represented by adults and juveniles of the polar species Neogloboquadrina pachyderma and the subpolar species Turborotalita quinqueloba. The dominating polar pteropod species Limacina helicina was represented by the juvenile and veliger stages. This winter study offers a unique contribution to our understanding of the inter-seasonal variability of planktic foraminfera and shelled pteropods abundance, distribution and population size structure in the Arctic Ocean.
Continue reading ‘Distribution and abundances of planktic foraminifera and shelled pteropods during the polar night in the sea-ice covered Northern Barents Sea’Species’ distribution and evolutionary history influence the responses of marine copepods to climate change: a global meta-analysis
Published 1 October 2021 Science ClosedTags: crustaceans, review, zooplankton
Ocean acidification (OA) and ocean warming (OW) are predicted to drive changes to the distribution of species and the structure of biological communities globally. Differences in life-history, physical traits, and the phenotypic response of organisms will, however, mean that the effects of OA and OW will differ among species. Geographical differences in environmental characteristics across habitats will also influence the effects of OA and OW, thereby driving inter-population differences in phenotypic response as determined by local adaptations. While is it accepted that the response of species will vary globally, predicting the trends in response of species remains highly uncertain. We undertook a meta-analysis of key biological traits of 47 marine copepod species from 88 studies to identify the intrinsic and extrinsic factors influencing the effects of OA and OW on copepod population demographics. Data from OA and OW were analysed independently due to insufficient two-stressor studies. We found that the large disparity in the response of species to OA and OW is largely defined by their environmental history. Additionally, the response of copepod species to OW is related to their evolutionary history which has less influence on their response to OA. Therefore, our study identified that the response of copepods to OA is driven by a combination of biotic and abiotic factors in their habitats. Under OA alone, copepods from less variable environments may be more susceptible, but the effects of OA will only be strongly negative at extreme low pH (<7). On the other hand, the response to OW is deeply tied to their phylogeny, whereby closely related species share similar costs and trade-offs. However, the effects of near-future OW (+2 to 4°C) seem mainly positive unless these temperatures exceed a species’ thermal limit. Finally, our analysis revealed that OW has a greater influence on key copepod traits than OA. Overall, this study shows that attempting to draw global patterns in the response of species to climate change from a single species or habitat without consideration of environmental and evolutionary history could lead to inaccurate and misleading predictions with respect to the future of biological communities.
Continue reading ‘Species’ distribution and evolutionary history influence the responses of marine copepods to climate change: a global meta-analysis’Integrated assessment of ocean acidification risks to pteropods in the Northern high latitudes: regional comparison of exposure, sensitivity and adaptive capacity
Published 13 September 2021 Science ClosedTags: adaptation, Antarctic, biological response, chemistry, field, globalmodeling, laboratory, modeling, molecular biology, mollusks, North Pacific, otherprocess, physiology, South Pacific, zooplankton
Exposure to the impact of ocean acidification (OA) is increasing in high-latitudinal productive habitats. Pelagic calcifying snails (pteropods), a significant component of the diet of economically important fish, are found in high abundance in these regions. Pteropods have thin shells that readily dissolve at low aragonite saturation state (Ωar), making them susceptible to OA. Here, we conducted a first integrated risk assessment for pteropods in the Eastern Pacific subpolar gyre, the Gulf of Alaska (GoA), Bering Sea, and Amundsen Gulf. We determined the risk for pteropod populations by integrating measures of OA exposure, biological sensitivity, and resilience. Exposure was based on physical-chemical hydrographic observations and regional biogeochemical model outputs, delineating seasonal and decadal changes in carbonate chemistry conditions. Biological sensitivity was based on pteropod morphometrics and shell-building processes, including shell dissolution, density and thickness. Resilience and adaptive capacity were based on species diversity and spatial connectivity, derived from the particle tracking modeling. Extensive shell dissolution was found in the central and western part of the subpolar gyre, parts of the Bering Sea, and Amundsen Gulf. We identified two distinct morphotypes: L. helicina helicina and L. helicina pacifica, with high-spired and flatter shells, respectively. Despite the presence of different morphotypes, genetic analyses based on mitochondrial haplotypes identified a single species, without differentiation between the morphological forms, coinciding with evidence of widespread spatial connectivity. We found that shell morphometric characteristics depends on omega saturation state (Ωar); under Ωar decline, pteropods build flatter and thicker shells, which is indicative of a certain level of phenotypic plasticity. An integrated risk evaluation based on multiple approaches assumes a high risk for pteropod population persistence with intensification of OA in the high latitude eastern North Pacific because of their known vulnerability, along with limited evidence of species diversity despite their connectivity and our current lack of sufficient knowledge of their adaptive capacity. Such a comprehensive understanding would permit improved prediction of ecosystem change relevant to effective fisheries resource management, as well as a more robust foundation for monitoring ecosystem health and investigating OA impacts in high-latitudinal habitats.
Continue reading ‘Integrated assessment of ocean acidification risks to pteropods in the Northern high latitudes: regional comparison of exposure, sensitivity and adaptive capacity’First record of straight-needle pteropod Creseis acicula Rang, 1828 bloom in the Çanakkale Strait (NE Aegean Sea, Turkey)
Published 10 September 2021 Science ClosedTags: chemistry, field, laboratory, Mediterranean, mollusks, morphology, photosynthesis, sediment, zooplankton
Pteropods are marine pelagic calcifier mollusks sensitive to chemical changes in seawater due to their highly soluble aragonite shells. Increased acidity (reduced pH) of seawater causes difficulties in precipitating their shells and/or results in their dissolution, which is related to increased atmospheric CO2 concentrations and warming of seawater. They are therefore indicators of environmental changes. In this paper, we present the first record of the straight-needle pteropod Creseis acicula Rang, 1828 bloom in the surface waters of the Ҫanakkale Strait, Turkey (NE Aegean Sea), encountered in July 2020, when the highest sea surface temperatures and pH levels since 2007 were recorded. In coastal zones, such as the Ҫanakkale Strait, anthropogenic activity contributes significantly to environmental changes. Consequently, the increase in pH at elevated temperatures indicates an auxiliary factor (i.e. anthropogenic activity) that triggered the C. acicula bloom, rather than global atmospheric CO2 levels.
Continue reading ‘First record of straight-needle pteropod Creseis acicula Rang, 1828 bloom in the Çanakkale Strait (NE Aegean Sea, Turkey)’Evolution and biomineralization of pteropod shells
Published 8 September 2021 Science ClosedTags: mollusks, review, zooplankton
Highlights
- Pteropod shells harbor a striking diversity of microstructures.
- Curved aragonite fibres are found in both superfamilies: Limacinoidea (coiled) and Cavolinioidea (uncoiled).
- Different levels of complexity of the helical microstructure exist: from incomplete to multiple helical turns.
- Microstructural observations in the fossil record suggest that the emergence of curved fibres precedes the diversification of euthecosomatous pteropods.
- Candidate biomineralization genes are identified based on shell matrix proteins from benthic and terrestrial snails.
Abstract
Shelled pteropods, known as ‘sea butterflies’, are a group of small gastropods that spend their entire lives swimming and drifting in the open ocean. They build thin shells of aragonite, a metastable polymorph of calcium carbonate. Pteropod shells have been shown to experience dissolution and reduced thickness with a decrease in pH and therefore represent valuable bioindicators to monitor the impacts of ocean acidification. Over the past decades, several studies have highlighted the striking diversity of shell microstructures in pteropods, with exceptional mechanical properties, but their evolution and future in acidified waters remains uncertain. Here, we revisit the body-of-work on pteropod biomineralization, focusing on shell microstructures and their evolution. The evolutionary history of pteropods was recently resolved, and thus it is timely to examine their shell microstructures in such context. We analyse new images of shells from fossils and recent species providing a comprehensive overview of their structural diversity. Pteropod shells are made of the crossed lamellar and prismatic microstructures common in molluscs, but also of curved nanofibers which are proposed to form a helical three-dimensional structure. Our analyses suggest that the curved fibres emerged before the split between coiled and uncoiled pteropods and that they form incomplete to multiple helical turns. The curved fibres are seen as an important trait in the adaptation to a planktonic lifestyle, giving maximum strength and flexibility to the pteropod thin and lightweight shells. Finally, we also elucidate on the candidate biomineralization genes underpinning the shell diversity in these important indicators of ocean health.
Continue reading ‘Evolution and biomineralization of pteropod shells’Reduced pH increases mortality and genotoxicity in an Arctic coastal copepod, Acartia longiremis
Published 6 September 2021 Science ClosedTags: Arctic, biological response, crustaceans, laboratory, molecular biology, mortality, physiology, zooplankton
Highlights
- The fast micromethod for DNA damage analysis was modified for use on copepods.
- Lowered seawater pH causes elevated mortality in Acartia longiremis.
- DNA damage in A. longiremis was elevated after long-term exposure to lowered pH.
Summary
This study investigates DNA damage and mortality in an Arctic marine copepod after long-term exposure to lowered pH. Acartia longiremis were collected from northern Norway and incubated in ambient pH 8.1, and reduced pH 7.6 and 7.2 over 3-4 weeks. Cumulative mortality was significantly elevated in the lowered pH treatments in all exposures. The fluorescence-based fast micromethod for analysis of DNA strand breaks and alkali-labile sites was modified for use on crustaceous zooplankton. DNA damage initially increased in the lowered pH treatments, decreasing after >14 days, and DNA damage was significantly higher in lowered pH conditions. This method is ideal for investigating oxidative stress and genotoxicity response to low pH in Arctic marine copepods exposed to future ocean acidification conditions.
Continue reading ‘Reduced pH increases mortality and genotoxicity in an Arctic coastal copepod, Acartia longiremis’Short-term effects of winter warming and acidification on phytoplankton growth and mortality: more losers than winners in a temperate coastal lagoon
Published 5 August 2021 Science ClosedTags: abundance, biological response, BRcommunity, community composition, growth, laboratory, mortality, multiple factors, North Atlantic, otherprocess, photosynthesis, phytoplankton, primary production, prokaryotes, temperature, zooplankton
Changes in temperature and CO2 are typically associated with climate change, but they also act on shorter time scales, leading to alterations in phytoplankton physiology and community structure. Interactions among stressors may cause synergistic or antagonistic effects on phytoplankton dynamics. Therefore, the main goal of this work is to understand the short-term isolated and interactive effects of warming and high CO2 on phytoplankton nutrient consumption, growth, production, and community structure in the Ria Formosa coastal lagoon (southern Portugal). We performed microcosm experiments with temperature and CO2 manipulation, and dilution experiments under temperature increase, using winter phytoplankton assemblages. Phytoplankton responses were evaluated using inverted and epifluorescence microscopy. Overall, phytoplankton growth and microzooplankton grazing on phytoplankton decreased with warming. Negative antagonist interactions with CO2 alleviated the negative effect of temperature on phytoplankton and cryptophytes. In contrast, higher temperature benefited smaller-sized phytoplankton, namely cyanobacteria and eukaryotic picophytoplankton. Diatom growth was not affected by temperature, probably due to nutrient limitation, but high CO2 had a positive effect on diatoms, alleviating the effect of nutrient limitation. Results suggest that this winter phytoplankton assemblage is well acclimated to ambient conditions, and short-term increases in temperature are detrimental, but can be alleviated by high CO2.
Continue reading ‘Short-term effects of winter warming and acidification on phytoplankton growth and mortality: more losers than winners in a temperate coastal lagoon’Adaptation to simultaneous warming and acidification carries a thermal tolerance cost in a marine copepod
Published 16 July 2021 Science ClosedTags: adaptation, biological response, crustaceans, laboratory, otherprocess, physiology, zooplankton
The ocean is undergoing warming and acidification. Thermal tolerance is affected both by evolutionary adaptation and developmental plasticity. Yet, thermal tolerance in animals adapted to simultaneous warming and acidification is unknown. We experimentally evolved the ubiquitous copepod Acartia tonsa to future combined ocean warming and acidification conditions (OWA approx. 22°C, 2000 µatm CO2) and then compared its thermal tolerance relative to ambient conditions (AM approx. 18°C, 400 µatm CO2). The OWA and AM treatments were reciprocally transplanted after 65 generations to assess effects of developmental conditions on thermal tolerance and potential costs of adaptation. Treatments transplanted from OWA to AM conditions were assessed at the F1 and F9 generations following transplant. Adaptation to warming and acidification, paradoxically, reduces both thermal tolerance and phenotypic plasticity. These costs of adaptation to combined warming and acidification may limit future population resilience.
Continue reading ‘Adaptation to simultaneous warming and acidification carries a thermal tolerance cost in a marine copepod’Global review of the impact of naturally occurring shallow water CO2 seeps
Published 1 July 2021 Science ClosedTags: algae, biological response, calcification, chemistry, corals, crustaceans, mitigation, mollusks, phanerogams, photosynthesis, review, vents, zooplankton
Studying the local impacts of natural marine discharges can help in understanding the local impacts of large-scale restoration programs. This paper reviews studies of naturally occurring CO2 rich hydrothermal vents to understand how nature responds. Venting CO2 raises both total DIC, and the CO2 partial pressure by a factor of 10 or 20 times, lowering the pH and the saturation state of calcium carbonate, impeding calcification by calcifying organisms.
The ocean is a relatively stable environment and significant changes to water chemistry caused by high levels of CO2 input impacts marine organisms. Many algae are able to survive and photosynthesise at low pH levels, and some may actually benefit from an increase in dissolved CO2. However, coralline and calcareous algae that form carbonate skeletons are negatively impacted at low pH. Ecologically and economically valuable marine flora such as kelp, seagrass and certain seaweeds can benefit from increased DIC, exhibiting increases in photosynthetic and growth rates. Kelp and seagrass may also increase local pH levels, creating refuges for calcifying marine species.
The calcification rates of Many marine invertebrates decrease with increasing pCO2. At sites closer to vent openings, with lower pH, the abundance and diversity of invertebrates is significantly reduced. This can impact species valuable to the fishery and aquaculture industry by directly affecting recruitment, growth and survivorship of species such as mussels and oysters and indirectly through reduced abundance of invertebrate prey for herring and mackerel. Corals are also negatively impacted by declining pH and calcium carbonate saturation, yet not all hard corals respond evenly. More resilient genera such as Porites can survive pH drops to approximately 7.8, however below this value reef development is virtually absent and the habitat is dominated by algae and soft corals.
Naturally occurring low pH sites are relatively common in the marine environment and though they clearly alter species composition and abundance, the locally lower pH does not kill marine life, and beyond dispersion zones species are unaffected. Global ocean acidification is a serious problem, however the impacts of local releases of CO2 are relatively limited, resulting in community shifts towards low pH tolerant species. Reversal of global ocean acidification is essential, and restoration of the oceans will require huge carbon dioxide removal (CDR) processes.
Continue reading ‘Global review of the impact of naturally occurring shallow water CO2 seeps’Planktic foraminiferal and pteropod contributions to carbon dynamics in the Arctic Ocean (North Svalbard Margin)
Published 10 June 2021 Science ClosedTags: abundance, biogeochemistry, biological response, chemistry, community composition, field, laboratory, mollusks, morphology, otherprocess, phytoplankton, protists, zooplankton
Planktic foraminifera and shelled pteropods are some of the major producers of calcium carbonate (CaCO3) in the ocean. Their calcitic (foraminifera) and aragonitic (pteropods) shells are particularly sensitive to changes in the carbonate chemistry and play an important role for the inorganic and organic carbon pump of the ocean. Here, we have studied the abundance distribution of planktic foraminifera and pteropods (individuals m–3) and their contribution to the inorganic and organic carbon standing stocks (μg m–3) and export production (mg m–2 day–1) along a longitudinal transect north of Svalbard at 81° N, 22–32° E, in the Arctic Ocean. This transect, sampled in September 2018 consists of seven stations covering different oceanographic regimes, from the shelf to the slope and into the deep Nansen Basin. The sea surface temperature ranged between 1 and 5°C in the upper 300 m. Conditions were supersaturated with respect to CaCO3 (Ω > 1 for both calcite and aragonite). The abundance of planktic foraminifera ranged from 2.3 to 52.6 ind m–3 and pteropods from 0.1 to 21.3 ind m–3. The planktic foraminiferal population was composed mainly of the polar species Neogloboquadrina pachyderma (55.9%) and the subpolar species Turborotalita quinqueloba (21.7%), Neogloboquadrina incompta (13.5%) and Globigerina bulloides (5.2%). The pteropod population was dominated by the polar species Limacina helicina (99.6%). The rather high abundance of subpolar foraminiferal species is likely connected to the West Spitsbergen Current bringing warm Atlantic water to the study area. Pteropods dominated at the surface and subsurface. Below 100 m water depth, foraminifera predominated. Pteropods contribute 66–96% to the inorganic carbon standing stocks compared to 4–34% by the planktic foraminifera. The inorganic export production of planktic foraminifera and pteropods together exceeds their organic contribution by a factor of 3. The overall predominance of pteropods over foraminifera in this high Arctic region during the sampling period suggest that inorganic standing stocks and export production of biogenic carbonate would be reduced under the effects of ocean acidification.
Continue reading ‘Planktic foraminiferal and pteropod contributions to carbon dynamics in the Arctic Ocean (North Svalbard Margin)’
