Symbiosis establishment is a milestone in the life cycles of most broadcast-spawning corals; however, it remains largely unknown how initial symbiont infection is affected by ocean warming and acidification, particularly for massive corals. This study investigated the combined effects of elevated temperature (29 vs. 31 °C) and pCO2 (~ 450 vs. ~ 1000 μatm) on the recruits of a widespread massive coral, Platygyra daedalea. Results showed that geometric diameter and symbiosis establishment were unaffected by high pCO2, while elevated temperature significantly reduced successful symbiont infection by 50% and retarded the geometric diameter by 6%. Although neither increased temperature, pCO2, nor their interaction affected survival or algal pigmentation of recruits, there was an inverse relationship between symbiont infection rates and survivorship, especially at high temperatures, possibly as a result of oxidative stress caused by algal symbionts under increased temperature. Intriguingly, the proportion of Durusdinium did not increase in recruits at 31 °C, while recruits reared under high pCO2 hosted less Breviolum and more Durusdinium, indicating a high degree of plasticity of early symbiosis and contrasting to the previous finding that heat stress usually leads to the prevalence of thermally tolerant Durusdinium in coral recruits. These results suggest that ocean warming is likely to be more deleterious for the early success of P. daedalea than ocean acidification and provide insights into our understanding of coral-algal symbiotic partnerships under future climatic conditions.
Continue reading ‘Plasticity of symbiont acquisition in new recruits of the massive coral Platygyra daedalea under ocean warming and acidification’Posts Tagged 'algae'
Plasticity of symbiont acquisition in new recruits of the massive coral Platygyra daedalea under ocean warming and acidification
Published 13 July 2021 Science ClosedTags: algae, biological response, BRcommunity, community composition, corals, laboratory, molecular biology, morphology, mortality, multiple factors, North Pacific, otherprocess, protists, reproduction, temperature
Positive species interactions strengthen in a high-CO2 ocean
Published 9 July 2021 Science ClosedTags: algae, biological response, community composition, field, fish, methods, multiple factors, performance, primary production, vents
Negative interactions among species are a major force shaping natural communities and are predicted to strengthen as climate change intensifies. Similarly, positive interactions are anticipated to intensify and could buffer the consequences of climate-driven disturbances. We used in situ experiments at volcanic CO2 vents within a temperate rocky reef to show that ocean acidification can drive community reorganization through indirect and direct positive pathways. A keystone species, the algal-farming damselfish Parma alboscapularis, enhanced primary productivity through its weeding of algae whose productivity was also boosted by elevated CO2. The accelerated primary productivity was associated with increased densities of primary consumers (herbivorous invertebrates), which indirectly supported increased secondary consumers densities (predatory fish) (i.e. strengthening of bottom-up fuelling). However, this keystone species also reduced predatory fish densities through behavioural interference, releasing invertebrate prey from predation pressure and enabling a further boost in prey densities (i.e. weakening of top-down control). We uncover a novel mechanism where a keystone herbivore mediates bottom-up and top-down processes simultaneously to boost populations of a coexisting herbivore, resulting in altered food web interactions and predator populations under future ocean acidification.
Continue reading ‘Positive species interactions strengthen in a high-CO2 ocean’Ocean acidification and direct interactions affect coral, macroalga, and sponge growth in the Florida Keys
Published 6 July 2021 Science ClosedTags: algae, biological response, BRcommunity, calcification, corals, laboratory, morphology, North Atlantic, porifera
Coral reef community composition, function, and resilience have been altered by natural and anthropogenic stressors. Future anthropogenic ocean and coastal acidification (together termed “acidification”) may exacerbate this reef degradation. Accurately predicting reef resilience requires an understanding of not only direct impacts of acidification on marine organisms but also indirect effects on species interactions that influence community composition and reef ecosystem functions. In this 28-day experiment, we assessed the effect of acidification on coral–algal, coral–sponge, and algal–sponge interactions. We quantified growth of corals (Siderastrea radians), fleshy macroalgae (Dictyota spp.), and sponges (Pione lampa) that were exposed to local summer ambient (603 μatm) or elevated (1105 μatm) pCO2 seawater. These species are common to hard-bottom communities, including shallow reefs, in the Florida Keys. Each individual was maintained in isolation or paired with another organism. Coral growth (net calcification) was similar across seawater pCO2 and interaction treatments. Fleshy macroalgae had increased biomass when paired with a sponge but lost biomass when growing in isolation or paired with coral. Sponges grew more volumetrically in the elevated seawater pCO2 treatment (i.e., under acidification conditions). Although these results are limited in temporal and spatial scales due to the experimental design, they do lend support to the hypothesis that acidification may facilitate a shift towards increased sponge and macroalgae abundance by directly benefiting sponge growth which in turn may provide more dissolved inorganic nitrogen to macroalgae in the Florida Keys.
Continue reading ‘Ocean acidification and direct interactions affect coral, macroalga, and sponge growth in the Florida Keys’Climate change increases susceptibility to grazers in a foundation seaweed
Published 5 July 2021 Science ClosedTags: algae, biological response, laboratory, mollusks, morphology, multiple factors, North Atlantic, performance, physiology, salinity, temperature
Climate change leads to multiple effects caused by simultaneous shifts in several physical factors which will interact with species and ecosystems in complex ways. In marine systems the effects of climate change include altered salinity, increased temperature, and elevated pCO2 which are currently affecting and will continue to affect marine species and ecosystems. Seaweeds are primary producers and foundation species in coastal ecosystems, which are particularly vulnerable to climate change. The brown seaweed Fucus vesiculosus (bladderwrack) is an important foundation species in nearshore ecosystems throughout its natural range in the North Atlantic Ocean and the Baltic Sea. This study investigates how individual and interactive effects of temperature, salinity, and pCO2 affect F. vesiculosus, using a fully crossed experimental design. We assessed the effects on F. vesiculosus in terms of growth, biochemical composition (phlorotannin content, C:N ratio, and ∂13C), and susceptibility to the specialized grazer Littorina obtusata. We observed that elevated pCO2 had a positive effect on seaweed growth in ambient temperature, but not in elevated temperature, while growth increased in low salinity at ambient but not high temperature, regardless of pCO2-level. In parallel to the statistically significant, but relatively small, positive effects on F. vesiculosus growth, we found that the seaweeds became much more susceptible to grazing in elevated pCO2 and reduced salinity, regardless of temperature. Furthermore, the ability of the seaweeds to induce chemical defenses (phlorotannins) was strongly reduced by all the climate stressors. Seaweeds exposed to ambient conditions more than doubled their phlorotannin content in the presence of grazers, while seaweeds exposed to any single or combined stress conditions showed only minor increases in phlorotannin content, or none at all. Despite the minor positive effects on seaweed growth, the results of this study imply that climate change can strongly affect the ability of fucoid seaweeds to induce chemical defenses and increase their susceptibility to grazers. This will likely lead to widespread consequences under future climate conditions, considering the important role of F. vesiculosus and other fucoids in many coastal ecosystems.
Continue reading ‘Climate change increases susceptibility to grazers in a foundation seaweed’Selection experiments in the sea: what can experimental evolution tell us about how marine life will respond to climate change?
Published 2 July 2021 Science ClosedTags: adaptation, algae, biological response, corals, crustaceans, echinoderms, molecular biology, mollusks, mortality, otherprocess, physiology, phytoplankton, prokaryotes, reproduction, review
Rapid evolution may provide a buffer against extinction risk for some species threatened by climate change; however, the capacity to evolve rapidly enough to keep pace with changing environments is unknown for most taxa. The ecosystem-level consequences of climate adaptation are likely to be the largest in marine ecosystems, where short-lived phytoplankton with large effective population sizes make up the bulk of primary production. However, there are substantial challenges to predicting climate-driven evolution in marine systems, including multiple simultaneous axes of change and considerable heterogeneity in rates of change, as well as the biphasic life cycles of many marine metazoans, which expose different life stages to disparate sources of selection. A critical tool for addressing these challenges is experimental evolution, where populations of organisms are directly exposed to controlled sources of selection to test evolutionary responses. We review the use of experimental evolution to test the capacity to adapt to climate change stressors in marine species. The application of experimental evolution in this context has grown dramatically in the past decade, shedding light on the capacity for evolution, associated trade-offs, and the genetic architecture of stress-tolerance traits. Our goal is to highlight the utility of this approach for investigating potential responses to climate change and point a way forward for future studies.
Continue reading ‘Selection experiments in the sea: what can experimental evolution tell us about how marine life will respond to climate change?’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’Physiology, niche characteristics and extreme events: current and future habitat suitability of a rhodolith-forming species in the Southwestern Atlantic
Published 18 June 2021 Science ClosedTags: algae, biological response, individualmodeling, laboratory, modeling, mortality, multiple factors, nutrients, performance, photosynthesis, physiology, policy, reproduction, South Atlantic, temperature
Highlights
- Global climate change and local stressors are the main threats to reef-building organisms and habitats they build, such as rhodolith beds.
- Through an experimental essay and ecological niche modelling, we were able to determine the environmental factors that determine the distribution and affect the physiology of an important rhodolith-forming species in the southwestern Atlantic.
- Our results raise the possibility of some rhodolith-forming species being resilient to future environmental change based on our current understanding of their distributions, a perspective that will need to be further explored by future studies.
- This information is helpful in informing policies for the conservation of priority areas, aiding the preservation of marine biodiversity in the South Atlantic.
Abstract
Given the ecological and biogeochemical importance of rhodolith beds, it is necessary to investigate how future environmental conditions will affect these organisms. We investigated the impacts of increased nutrient concentrations, acidification, and marine heatwaves on the performance of the rhodolith-forming species Lithothamnion crispatum in a short-term experiment, including the recovery of individuals after stressor removal. Furthermore, we developed an ecological niche model to establish which environmental conditions determine its current distribution along the Brazilian coast and to project responses to future climate scenarios. Although L. crispatum suffered a reduction in photosynthetic performance when exposed to stressors, they returned to pre-experiment values following the return of individuals to control conditions. The model showed that the most important variables in explaining the current distribution of L. crispatum on the Brazilian coast were maximum nitrate and temperature. In future ocean conditions, the model predicted a range expansion of habitat suitability for this species of approximately 58.5% under RCP 8.5. Physiological responses to experimental future environmental conditions corroborated model predictions of the expansion of this species’ habitat suitability in the future. This study, therefore, demonstrates the benefits of applying combined approaches to examine potential species responses to climate-change drivers from multiple angles.
Continue reading ‘Physiology, niche characteristics and extreme events: current and future habitat suitability of a rhodolith-forming species in the Southwestern Atlantic’Cultivating marine macroalgae in CO2-enriched seawater: a bio-economic approach
Published 17 June 2021 Science ClosedTags: algae, biological response, laboratory, morphology, multiple factors, photosynthesis, temperature
Highlights
- Seasonal variability of temperature under ambient or enriched CO2 conditions affect productivity in two model fleshy seaweeds, Ulva rigida and Gracilaria conferta.
- The growth of these seaweeds can be doubled when exposed to high CO2 concentrations.
- Maximal short-run profits were obtained at ca. 22.5 °C and 27.5 °C for U. rigida and G. conferta, respectively.
- Based on the seaweeds respond to external seasonal changes in temperature and CO2 concentration, farmers may decide what and where to grow seasonally.
Abstract
By the end of the current century atmospheric CO2 concentration may reach 1000 ppm, more than twice the present level set at ca. 400 ppm. Marine macroalgae (seaweeds) contribute to global primary production and by taking up CO2 they may ameliorate and regulate global climate change. Seaweeds also have direct and indirect economic importance by providing food and bioactive compounds for human benefit. Nonetheless, all these benefits could be jeopardized by the ongoing pressures, both local and global, on marine environments. In this study we examine the effects of dissolved CO2 and seasonal seawater temperature on the growth rates (measured weekly changes in biomass and expressed on a daily basis) of two model species, Ulva rigida (Chlorophyta) and Gracilaria conferta (Rhodophyta), which are common in the intertidal zone of the Israeli Mediterranean Sea, and cultivated by the local seaweed industry. The seaweeds were grown in land-based 40 L fiberglass tanks fertilized with sufficient N and P, supplied with running seawater and continuous air bubbling to keep equal exposure of the seaweeds to nutrients and light. The tanks were also provided with aeration with regular air (ambient CO2, ~ 400 ppm) or CO2-enriched air (~780 ppm). Seaweeds exposed to CO2–enriched seawater grew faster, 32.5 and 8.5% growth per day for U. rigida and G. conferta, respectively. Following calculations of productivity rates, market price, and input cost, we estimate production and show a quadratic production function with respect to temperature for each CO2 concentration. Thus, there is an optimal temperature that maximizes seaweed output. Based on the production function estimates and using market prices, maximal short-run profits were obtained at ca. 22.5 °C and 27.5 °C for U. rigida and G. conferta, respectively. These results may provide useful information for seaweed growers on what and where to grow seasonally, and how farming activities should adapt to external changes in temperature and CO2 concentration.
Continue reading ‘Cultivating marine macroalgae in CO2-enriched seawater: a bio-economic approach’Hands-on exploration of ocean acidification with a living calcifier
Published 14 June 2021 Science ClosedTags: algae, biological response, calcification, education, laboratory, methods
This hands-on lab allows students to explore concepts and quantify effects of ocean acidification. Many laboratory activities simplify ocean acidification through computer simulations or dripping acid on nonliving materials (e.g., sea shells) but do not provide adequate opportunities for students to measure, inquire, or see real consequences for living organisms. Thus, we developed this low-cost, easily accessible experiment to imitate ocean acidification on living, calcifying organisms.
Continue reading ‘Hands-on exploration of ocean acidification with a living calcifier’Impacts of seagrass on benthic microalgae and phytoplankton communities in an experimentally warmed coral reef mesocosm
Published 10 June 2021 Science ClosedTags: algae, biological response, BRcommunity, community composition, corals, laboratory, mesocosms, molecular biology, morphology, North Pacific, otherprocess, phanerogams, physiology, phytoplankton
The effects of seagrass on microalgal assemblages under experimentally elevated temperatures (28°C) and CO2 partial pressures (pCO2; 800 μatm) were examined using coral reef mesocosms. Concentrations of nitrate, ammonium, and benthic microalgal chlorophyll a (chl-a) were significantly higher in seagrass mesocosms, whereas phytoplankton chl-a concentrations were similar between seagrass and seagrass-free control mesocosms. In the seagrass group, fewer parasitic dinoflagellate OTUs (e.g., Syndiniales) were found in the benthic microalgal community though more symbiotic dinoflagellates (e.g., Cladocopium spp.) were quantified in the phytoplankton community. Our results suggest that, under ocean acidification conditions, the presence of seagrass nearby coral reefs may (1) enhance benthic primary productivity, (2) decrease parasitic dinoflagellate abundance, and (3) possibly increase the presence of symbiotic dinoflagellates.
Continue reading ‘Impacts of seagrass on benthic microalgae and phytoplankton communities in an experimentally warmed coral reef mesocosm’The effects of elevated-CO2 and UVR on photosynthetic performance and nitrate reductase activity of Ulva flexuosa Wulfen 1803
Published 9 June 2021 Science ClosedTags: algae, biological response, laboratory, Mediterranean, photosynthesis, physiology
After the industrial revolution, increasing anthropogenic CO2 emission causes a number of changes in seawater. These changes are known as ocean acidification and affect the seaweeds in various ways. Therefore, this study is aimed to determine the ecological succession of Ulva flexuosa Wulfen 1803 in future predicted CO2-induced low pH conditions alone and in combination with naturally relevant ultraviolet radiation (UVR). For this purpose, acidification experiments with and without UVR were conducted on U. flexuosa from the Mediterranean coast, and important physiological features of algae was investigated. In this study, the Fv/Fm ratios of U. flexuosa ranged from 0.718±0.01 to 0.754±0.009. While rETRmax values of samples exposed to elevated-CO2 were measured between 112.13 – 151.93 µmol e–m-2s-1, it was determined between 111.7 – 158.4 µmol e–m-2s-1 in samples exposed to ambient sea water. According to our results, increased CO2 concentration in seawater did not improve the photosynthetic efficiency of U. flexuosa. However, when the specimens were exposed to elevated-CO2, nitrate reductase activity of U. flexuosa was declined drastically. According to the results, it is suggested that the elevated CO2 may regulate the nitrogen preference of U. flexuosa. Besides, the data also show that U. flexuosa was not sensitive to UVR.
Continue reading ‘The effects of elevated-CO2 and UVR on photosynthetic performance and nitrate reductase activity of Ulva flexuosa Wulfen 1803’Patterns of element incorporation in calcium carbonate biominerals recapitulate phylogeny for a diverse range of marine calcifiers
Published 3 June 2021 Science ClosedTags: algae, annelids, biogeochemistry, biological response, calcification, cnidaria, crustaceans, echinoderms, growth, individualmodeling, laboratory, mollusks, paleo, performance, photosynthesis, physiology, reproduction
Elemental ratios in biogenic marine calcium carbonates are widely used in geobiology, environmental science, and paleoenvironmental reconstructions. It is generally accepted that the elemental abundance of biogenic marine carbonates reflects a combination of the abundance of that ion in seawater, the physical properties of seawater, the mineralogy of the biomineral, and the pathways and mechanisms of biomineralization. Here we report measurements of a suite of nine elemental ratios (Li/Ca, B/Ca, Na/Ca, Mg/Ca, Zn/Ca, Sr/Ca, Cd/Ca, Ba/Ca, and U/Ca) in 18 species of benthic marine invertebrates spanning a range of biogenic carbonate polymorph mineralogies (low-Mg calcite, high-Mg calcite, aragonite, mixed mineralogy) and of phyla (including Mollusca, Echinodermata, Arthropoda, Annelida, Cnidaria, Chlorophyta, and Rhodophyta) cultured at a single temperature (25°C) and a range of pCO2 treatments (ca. 409, 606, 903, and 2856 ppm). This dataset was used to explore various controls over elemental partitioning in biogenic marine carbonates, including species-level and biomineralization-pathway-level controls, the influence of internal pH regulation compared to external pH changes, and biocalcification responses to changes in seawater carbonate chemistry. The dataset also enables exploration of broad scale phylogenetic patterns of elemental partitioning across calcifying species, exhibiting high phylogenetic signals estimated from both uni- and multivariate analyses of the elemental ratio data (univariate: λ = 0–0.889; multivariate: λ = 0.895–0.99). Comparing partial R2 values returned from non-phylogenetic and phylogenetic regression analyses echo the importance of and show that phylogeny explains the elemental ratio data 1.4–59 times better than mineralogy in five out of nine of the elements analyzed. Therefore, the strong associations between biomineral elemental chemistry and species relatedness suggests mechanistic controls over element incorporation rooted in the evolution of biomineralization mechanisms.
Continue reading ‘Patterns of element incorporation in calcium carbonate biominerals recapitulate phylogeny for a diverse range of marine calcifiers’Energetic context determines the effects of multiple upwelling-associated stressors on sea urchin performance
Published 2 June 2021 Science ClosedTags: adaptation, algae, biological response, BRcommunity, community composition, echinoderms, laboratory, mesocosms, morphology, mortality, multiple factors, otherprocess, oxygen, performance, temperature
Globally, kelp forests are threatened by multiple stressors, including increasing grazing by sea urchins. With coastal upwelling predicted to increase in intensity and duration in the future, understanding whether kelp forest and urchin barren urchins are differentially affected by upwelling-related stressors will give insight into how future conditions may affect the transition between kelp forests and barrens. We assessed how current and future-predicted changes in the duration and magnitude of upwelling-associated stressors (low pH, dissolved oxygen, and temperature) affected the performance of purple sea urchins (Strongylocentrotus purpuratus) sourced from rapidly-declining bull kelp (Nereocystis leutkeana) forests and nearby barrens and maintained on habitat-specific diets. Kelp forest urchins were of superior condition to barrens urchins, with ~ 6–9 times more gonad per body mass. Grazing and condition in kelp forest urchins were more negatively affected by distant-future and extreme upwelling conditions, whereas grazing and survival in urchins from barrens were sensitive to both current-day and all future-predicted upwelling, and to increases in acidity, hypoxia, and temperature regardless of upwelling. We conclude that urchin barren urchins are more susceptible to increases in the magnitude and duration of upwelling-related stressors than kelp forest urchins. These findings have important implications for urchin population dynamics and their interaction with kelp.
Continue reading ‘Energetic context determines the effects of multiple upwelling-associated stressors on sea urchin performance’Calcification in free-living coralline algae is strongly influenced by morphology: implications for susceptibility to ocean acidification
Published 28 May 2021 Science ClosedTags: algae, biological response, calcification, laboratory, light, morphology, multiple factors, physiology, respiration
Rhodolith beds built by free-living coralline algae are important ecosystems for marine biodiversity and carbonate production. Yet, our mechanistic understanding regarding rhodolith physiology and its drivers is still limited. Using three rhodolith species with different branching morphologies, we investigated the role of morphology in species’ physiology and the implications for their susceptibility to ocean acidification (OA). For this, we determined the effects of thallus topography on diffusive boundary layer (DBL) thickness, the associated microscale oxygen and pH dynamics and their relationship with species’ metabolic and light and dark calcification rates, as well as species’ responses to short-term OA exposure. Our results show that rhodolith branching creates low-flow microenvironments that exhibit increasing DBL thickness with increasing branch length. This, together with species’ metabolic rates, determined the light-dependent pH dynamics at the algal surface, which in turn dictated species’ calcification rates. While these differences did not translate in species-specific responses to short-term OA exposure, the differences in the magnitude of diurnal pH fluctuations (~ 0.1–1.2 pH units) between species suggest potential differences in phenotypic plasticity to OA that may result in different susceptibilities to long-term OA exposure, supporting the general view that species’ ecomechanical characteristics must be considered for predicting OA responses.
Continue reading ‘Calcification in free-living coralline algae is strongly influenced by morphology: implications for susceptibility to ocean acidification’Ocean acidification and carbon limitation affect photosynthetic capacity of the seagrass (Amphibolis antarctica) and its calcifying epiphytes
Published 26 May 2021 Science ClosedTags: algae, biological response, BRcommunity, calcification, chemistry, Indian, laboratory, phanerogams, photosynthesis, physiology
Amphibolis antarctica seagrass meadows, and their associated calcifying epiphytes, are abundant on Australia’s west coast, but have declined in recent years due to anthropogenic factors such as marine heatwaves, damaging fishing practices and increased turbidity resulting from eutrophication which causes light limitation. Burning fossil fuels has increased the flux of CO2 in to the ocean, lowering surface seawater pH, and making more carbon available for photosynthetic life. There are benefits of increasing CO2 for those seagrasses that are carbon limited, as this alleviates their energetic use of carbon concentrating mechanisms (CCM’S) which are less efficient, and more energy costly than passive diffusion of CO2 across cell walls. This study used pulse amplitude modulation fluorometry to quantify relative electron transport rates (rETR) at a range of pH levels both above and below current ocean pH of 8.1, and found that A. antarctica has significantly decreased rETR at pH treatments of 7.81 and 7.61. Calcifying epiphytes on A. antarctica also had a significant drop in rETR at the lower pH treatments. There was also significantly lowered rETR at higher pH treatments, likely the result of carbon limitation. These results from the lower pH tests may have profound implications for A. antarctica meadows under ocean acidification. A decline in these meadows would cause the loss of ecosystem services provided by them, such as carbon storage and sequestration, commercial fisheries and a decline the abundance of biodiversity that they support.
Continue reading ‘Ocean acidification and carbon limitation affect photosynthetic capacity of the seagrass (Amphibolis antarctica) and its calcifying epiphytes’Marginal populations show physiological adaptations and resilience to future climatic changes across a North Atlantic distribution
Published 24 May 2021 Science ClosedTags: algae, biological response, BRcommunity, calcification, laboratory, morphology, multiple factors, North Atlantic, physiology, primary production, respiration, temperature
Highlights
- Elevated temperature has a greater effect on calcifying algae populations than pCO2.
- Southern and central populations already live close to their thermal and stress limits, while northern populations appear as the most resilient to environmental changes.
- Light calcification is the most valuable physiological process and is prioritized in populations throughout the geographical gradient in the NE Atlantic.
Abstract
Rising levels of anthropogenic carbon dioxide (CO2) in the atmosphere over the past several decades has resulted in a changing climate and is projected to further fuel global climate change in future centuries. Key components of climate change in the ocean are ocean acidification (decreasing pH and carbonate ion concentration [ CO32- ]) and rising sea surface temperatures. While several studies have investigated the effect of these climatic changes on a single population, very few studies have addressed effects on populations living at the margins of their species distribution and the full distributional range. This gap in knowledge impedes the determination of detailed predictions for most species’ futures. Over the course of four months, we investigated physiological changes (primary production, respiration, calcification and growth rates) of 6 populations of the intertidal ecosystem engineer and articulated coralline alga Corallina officinalis to future climatic conditions (low pH (∼7.8); T + 3 °C; as well as the combination of low pH and T + 3 °C). The populations (n = 2 per geographical location) represent the northern (Iceland) and southern (Spain) margins, as well as the centre (England) of the species distribution in the NE Atlantic. Here, we show that southern and central populations are already living closer to their thermal and stress limits, while Northern populations appear to be the most resilient to environmental changes. We present data confirming light calcification to be the most valuable physiological process which is prioritized in populations throughout the geographical gradient in the NE Atlantic. We found elevated temperature to have a greater effect on populations than pCO2. Investigating and monitoring organism physiology and structure under these extreme environmental conditions provides important information to predict their acclimatisation and resilience to future environmental conditions and potential changes in their distribution.
Kolzenburg R., D’Amore F., McCoy S. J. & Ragazzola F., 2021. Marginal populations show physiological adaptations and resilience to future climatic changes across a North Atlantic distribution. Environmental and Experimental Botany: 104522. doi: 10.1016/j.envexpbot.2021.104522. Article (subscription required).
Effects of ocean acidification on the growth and biochemical composition of a green alga (Ulva fasciata) and its associated microbiota
Published 21 May 2021 Science ClosedTags: algae, biological response, BRcommunity, chemistry, growth, laboratory, molecular biology, photosynthesis, physiology, prokaryotes
In marine ecosystems, fluctuations in surface-seawater carbon dioxide (CO2), significantly influence the whole metabolism of marine algae, especially during the early stages of macroalgal development. In this study, the response of the green alga Ulva fasciata for elevating ocean acidification was investigated using four levels of pCO2 ∼280, 550, 750 and 1050 µatm. Maximum growth rate (6.6 % day-1), protein (32.43 %DW) and pigment (2.9 mg/g) accumulation were observed at pCO2-550 with an increase of ∼2-fold compared to control. On the other hand, lipid and carbohydrate contents recorded their maximum production (4.23 and 46.96 %DW, respectively) at pCO2-750 while control showed 3.70 and 42.37 %DW, respectively. SDS-PAGE showed the presence of unique bands in response to pCO2, especially at 550 µatm. Dominant associated bacteria was shifted from Halomonas hydrothermalis of control to Vibrio toranzoniae at pCO2-1050. These findings suggest that ocean acidification at 550 µatm might impose noticeable effects on growth, protein, pigments, and protein profile of U. fasciata, which could be a good source for fish farming. While, pCO2-750 was recommended for energetic purpose, due to its high lipid and carbohydrate contents.
Continue reading ‘Effects of ocean acidification on the growth and biochemical composition of a green alga (Ulva fasciata) and its associated microbiota’Rapid multi-generational acclimation of coralline algal reproductive structures to ocean acidification
Published 14 May 2021 Science ClosedTags: abundance, algae, biological response, Indian, laboratory, otherprocess, reproduction
The future of coral reef ecosystems is under threat because vital reef-accreting species such as coralline algae are highly susceptible to ocean acidification. Although ocean acidification is known to reduce coralline algal growth rates, its direct effects on the development of coralline algal reproductive structures (conceptacles) is largely unknown. Furthermore, the long-term, multi-generational response of coralline algae to ocean acidification is extremely understudied. Here, we investigate how mean pH, pH variability and the pH regime experienced in their natural habitat affect coralline algal conceptacle abundance and size across six generations of exposure. We show that second-generation coralline algae exposed to ocean acidification treatments had conceptacle abundances 60% lower than those kept in present-day conditions, suggesting that conceptacle development is initially highly sensitive to ocean acidification. However, this negative effect of ocean acidification on conceptacle abundance disappears after three generations of exposure. Moreover, we show that this transgenerational acclimation of conceptacle development is not facilitated by a trade-off with reduced investment in growth, as higher conceptacle abundances are associated with crusts with faster growth rates. These results indicate that the potential reproductive output of coralline algae may be sustained under future ocean acidification.
Continue reading ‘Rapid multi-generational acclimation of coralline algal reproductive structures to ocean acidification’Global declines in coral reef calcium carbonate production under ocean acidification and warming
Published 11 May 2021 Science ClosedTags: algae, biological response, calcification, chemistry, corals, dissolution, globalmodeling, review
Significance
The growth of coral reefs is threatened by the dual stressors of ocean warming and acidification. Despite a wealth of studies assessing the impacts of climate change on individual taxa, projections of their impacts on coral reef net carbonate production are limited. By projecting impacts across 233 different locations, we demonstrate that the majority of coral reefs will be unable to maintain positive net carbonate production globally by the year 2100 under representative concentration pathways RCP4.5 and 8.5, while even under RCP2.6, coral reefs will suffer reduced accretion rates. Our results provide quantitative projections of how different climate change stressors will influence whole ecosystem carbonate production across coral reefs in all major ocean basins.
Abstract
Ocean warming and acidification threaten the future growth of coral reefs. This is because the calcifying coral reef taxa that construct the calcium carbonate frameworks and cement the reef together are highly sensitive to ocean warming and acidification. However, the global-scale effects of ocean warming and acidification on rates of coral reef net carbonate production remain poorly constrained despite a wealth of studies assessing their effects on the calcification of individual organisms. Here, we present global estimates of projected future changes in coral reef net carbonate production under ocean warming and acidification. We apply a meta-analysis of responses of coral reef taxa calcification and bioerosion rates to predicted changes in coral cover driven by climate change to estimate the net carbonate production rates of 183 reefs worldwide by 2050 and 2100. We forecast mean global reef net carbonate production under representative concentration pathways (RCP) 2.6, 4.5, and 8.5 will decline by 76, 149, and 156%, respectively, by 2100. While 63% of reefs are projected to continue to accrete by 2100 under RCP2.6, 94% will be eroding by 2050 under RCP8.5, and no reefs will continue to accrete at rates matching projected sea level rise under RCP4.5 or 8.5 by 2100. Projected reduced coral cover due to bleaching events predominately drives these declines rather than the direct physiological impacts of ocean warming and acidification on calcification or bioerosion. Presently degraded reefs were also more sensitive in our analysis. These findings highlight the low likelihood that the world’s coral reefs will maintain their functional roles without near-term stabilization of atmospheric CO2 emissions.
Continue reading ‘Global declines in coral reef calcium carbonate production under ocean acidification and warming’
