Posts Tagged 'phanerogams'

Marine macroinvertebrate ecosystem services under changing conditions of seagrasses and mangroves

Published 5 June 2023 Science Leave a Comment
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Highlights

  • Overfishing and climate change show potential effects on MMI ES.
  • MMI regulating ES can be quantified using species richness and functional traits.
  • Digital platforms are valuable tools to retrieve data but have limitations.
  • Baseline data and information on environmental changes and MMI ES is provided.

Abstract

This study aimed to investigate the impact of changing environmental conditions on MMI ES in seagrasses and mangroves. We used data from satellite and biodiversity platforms combined with field data to explore the links between ecosystem pressures (habitat conversion, overexploitation, climate change), conditions (environmental quality, ecosystem attributes), and MMI ES (provisioning, regulation, cultural). Both seagrass and mangrove extents increased significantly since 2016. While sea surface temperature showed no significant annual variation, sea surface partial pressure CO2, height above sea level and pH presented significant changes. Among the environmental quality variables only silicate, PO4 and phytoplankton showed significant annual varying trends. The MMI food provisioning increased significantly, indicating overexploitation that needs urgent attention. MMI regulation and cultural ES did not show significant trends overtime. Our results show that MMI ES are affected by multiple factors and their interactions can be complex and non-linear. We identified key research gaps and suggested future directions for research. We also provided relevant data that can support future ES assessments.

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Acidification alters sediment nitrogen source-sink dynamics in eelgrass (Zostera marina (L.)) beds

Published 9 May 2023 Science Closed
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Dissolved carbon dioxide (CO2) in seawater lowers water pH and can disrupt microbial nutrient cycles. It is unclear how acidification impacts hot spots of nutrient cycling in marine ecosystems such as eelgrass (Zostera marina) beds. We measured nutrient and gas fluxes in sediment cores from Z. marina beds and unvegetated-sediment habitats in Shinnecock Bay, New York, USA in a continuous-flow system with acidified and ambient pH treatments. Under ambient conditions, uptake of N2 by nitrogen (N) fixation was greater than production of N2 by denitrification. Denitrification, however, was dominant under acidified conditions. We then enriched flowing seawater with 15NO3− to test the impact of a nutrient pulse with ambient pH or acidified conditions in the eelgrass and unvegetated cores. Sediment N2 efflux was higher in eelgrass than unvegetated sediments under acidified pH with N-enriched treatments. Results suggest that eelgrass beds may serve as sinks rather than sources of N under the combined stressors of acidification and N-loading. Documenting changes to N pathways under acidification can inform efforts to manage marine ecosystems and conserve benthic habitats.

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Field development of Posidonia oceanica seedlings changes under predicted acidification conditions

Published 27 March 2023 Science Closed
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Ocean acidification has been consistently evidenced to have profound and lasting impacts on marine species. Observations have shown seagrasses to be highly susceptible to future increased pCO2 conditions, but the responses of early life stages as seedlings are poorly understood. This study aimed at evaluating how projected Mediterranean Sea acidification affects the survival, morphological and biochemical development of Posidonia oceanica seedlings through a long-term field experiment along a natural low pH gradient. Future ocean conditions seem to constrain the morphological development of seedlings. However, high pCO2 exposures caused an initial increase in the degree of saturation of fatty acids in leaves and then improved the fatty acid adjustment increasing unsaturation levels in leaves (but not in seeds), suggesting a nutritional compound translocation. Results also suggested a P. oceanica structural components remodelling which may counteract the effects of ocean acidification but would not enhance seagrass seedling productivity.

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Climate change amelioration by marine producers: does dominance predict impact?

Published 13 January 2023 Science Closed
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Climate change threatens biodiversity worldwide, and assessing how those changes will impact communities will be critical for conservation. Dominant primary producers can alter local-scale environmental conditions, reducing temperature via shading and mitigating ocean acidification via photosynthesis, which could buffer communities from the impacts of climate change. We conducted two experiments on the coast of southeastern Alaska to assess the effects of a common seaweed species, Neorhodomela oregona, on temperature and pH in field tide pools and tide pool mesocosms. We found that N. oregona was numerically dominant in this system, covering >60% of habitable space in the pools and accounting for >40% of live cover. However, while N. oregona had a density-dependent effect on pH in isolated mesocosms, we did not find a consistent effect of N. oregona on either pH or water temperature in tide pools in the field. These results suggest that the amelioration of climate change impacts in immersed marine ecosystems by primary producers is not universal and likely depends on species’ functional attributes, including photosynthetic rate and physical structure, in addition to abundance or dominance.

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Posidonia bonsai: dwarf Posidonia oceanica shoots associated to hydrothemal vent systems (Panarea Island, Italy)

Published 11 January 2023 Science Closed
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Highlights

  • Dwarf Posidonia oceanica (bonsai) observed in hydrothermal vents off Panarea.
  • Bonsai shoots are from 61–75% smaller in leaf biomass than regular-sized shoots
  • Bonsai shoots lacks the regular seasonal pattern in sheath thickness (lepidochronology) of normal-sized shoots

Abstract

Very small-sized shoots of the Mediterranean seagrass Posidonia oceanica, defined as “bonsai” shoots, were found in areas with most intense CO2 emissions and low pH associated with four vents systems off Panarea island (Aeolian Archipelago, Sicily, Southern Tyrrhenian Sea). Bonsai shoots were sampled in September 2021 and October 2022: Bottaro crater (8 m depth), Camp 7 (16 m and 21 m), Black Point (20 m) and Hot/Cold Points (10 m). They had 2–6 leaves, and adult-intermediate leaves were 5–21 cm long and 3.5–7 mm wide, with leaf shoot surface ranging 4.8 and 44.5 cm2, and shoot leaf biomass between 16 and 89 mg (d.w.). These values were all significantly lower (t-test p < 0.006–0.0001) than those measured in normal-sized shoots collected within the vents and in control sites not affected by gas emissions. Bonsai shoots had 86–89% lower leaf surface, and 61–75% lower leaf biomass than all normal-sized shoots measured. The sheath thickness of the bonsai shoots was very low (0.1–0.8 mm), and the temporal trend of sheath thickness along the rhizome (lepidochronology) showed an irregular pattern, without the clear cyclical seasonal variation typical of normal-sized shoots. The reasons of size reduction and lack of temporal cycle in lepidochronology are discussed in the light of plant acclimatization and the constraints imposed by the continuous exposure to the stressful conditions of seawater acidification and presence of phytotoxic gases (e.g. hydrogen sulfide) in the vents.

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Photorespiration in eelgrass (Zostera marina L.): a photoprotection mechanism for survival in a CO2-limited world

Published 17 November 2022 Science Closed
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Photorespiration, commonly viewed as a loss in photosynthetic productivity of C3 plants, is expected to decline with increasing atmospheric CO2, even though photorespiration plays an important role in the oxidative stress responses. This study aimed to quantify the role of photorespiration and alternative photoprotection mechanisms in Zostera marina L. (eelgrass), a carbon-limited marine C3 plant, in response to ocean acidification. Plants were grown in controlled outdoor aquaria at different [CO2]aq ranging from ~55 (ambient) to ~2121 μM for 13 months and compared for differences in leaf photochemistry by simultaneous measurements of O2 flux and variable fluorescence. At ambient [CO2], photosynthesis was carbon limited and the excess photon absorption was diverted both to photorespiration and non-photochemical quenching (NPQ). The dynamic range of NPQ regulation in ambient grown plants, in response to instantaneous changes in [CO2]aq, suggested considerable tolerance for fluctuating environmental conditions. However, 60 to 80% of maximum photosynthetic capacity of ambient plants was diverted to photorespiration resulting in limited carbon fixation. The photosynthesis to respiration ratio (PE: RD) of ambient grown plants increased 6-fold when measured under high CO2 because photorespiration was virtually suppressed. Plants acclimated to high CO2 maintained 4-fold higher PE: RD than ambient grown plants as a result of a 60% reduction in photorespiration. The O2 production efficiency per unit chlorophyll was not affected by the CO2 environment in which the plants were grown. Yet, CO2 enrichment decreased the light level to initiate NPQ activity and downregulated the biomass specific pigment content by 50% and area specific pigment content by 30%. Thus, phenotypic acclimation to ocean carbonation in eelgrass, indicating the coupling between the regulation of photosynthetic structure and metabolic carbon demands, involved the downregulation of light harvesting by the photosynthetic apparatus, a reduction in the role of photorespiration and an increase in the role of NPQ in photoprotection. The quasi-mechanistic model developed in this study permits integration of photosynthetic and morphological acclimation to ocean carbonation into seagrass productivity models, by adjusting the limits of the photosynthetic parameters based on substrate availability and physiological capacity.

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Impact of climate change on Arctic macroalgal communities

Published 4 November 2022 Science Closed
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The Arctic region faces a warming rate that is more than twice the global average. Seaice loss, increase in precipitation and freshwater discharge, changes in underwater light, and amplification of ocean acidification modify benthic habitats and the communities they host. Here we synthesize existing information on the impacts of climate change on the macroalgal communities of Arctic coasts. We review the shortand long-term changes in environmental characteristics of shallow hard-bottomed Arctic coasts, the floristics of Arctic macroalgae (description, distribution, life-cycle, adaptations), the responses of their biological and ecological processes to climate change, the resulting winning and losing species, and the effects on ecosystem functioning. The focus of this review is on fucoid species, kelps, and coralline algae which are key ecosystem engineers in hard-bottom shallow areas of the Arctic, providing food, substrate, shelter, and nursery ground for many species. Changes in seasonality, benthic functional diversity, food-web structure, and carbon cycle are already occurring and are reshaping Arctic benthic ecosystems. Shallow communities are projected to shift from invertebrate-to algal-dominated communities. Fucoid and several kelp species are expected to largely spread and dominate the area with possible extinctions of native species. A considerable amount of functional diversity could be lost impacting the processing of land-derived nutrients and organic matter and significantly altering trophic structure and energy flow up to the apex consumers. However, many factors are not well understood yet, making it difficult to appreciate the current situation and predict the future coastal Arctic ecosystem. Efforts must be made to improve knowledge in key regions with proper seasonal coverage, taking into account interactions between stressors and across species.

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Climate change and species facilitation affect the recruitment of macroalgal marine forests

Published 3 November 2022 Science Closed
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Marine forests are shrinking globally due to several anthropogenic impacts including climate change. Forest-forming macroalgae, such as Cystoseira s.l. species, can be particularly sensitive to environmental conditions (e.g. temperature increase, pollution or sedimentation), especially during early life stages. However, not much is known about their response to the interactive effects of ocean warming (OW) and acidification (OA). These drivers can also affect the performance and survival of crustose coralline algae, which are associated understory species likely playing a role in the recruitment of later successional species such as forest-forming macroalgae. We tested the interactive effects of elevated temperature, low pH and species facilitation on the recruitment of Cystoseira compressa. We demonstrate that the interactive effects of OW and OA negatively affect the recruitment of C. compressa and its associated coralline algae Neogoniolithon brassica-florida. The density of recruits was lower under the combinations OW and OA, while the size was negatively affected by the temperature increase but positively affected by the low pH. The results from this study show that the interactive effects of climate change and the presence of crustose coralline algae can have a negative impact on the recruitment of Cystoseira s.l. species. While new restoration techniques recently opened the door to marine forest restoration, our results show that the interactions of multiple drivers and species interactions have to be considered to achieve long-term population sustainability.

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The differential ability of two species of seagrass to use carbon dioxide and bicarbonate and their modelled response to rising concentrations of inorganic carbon

Published 31 October 2022 Science Closed
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Seagrass meadows are one of the most productive ecosystems on the planet, but their photosynthesis rate may be limited by carbon dioxide but mitigated by exploiting the high concentration of bicarbonate in the ocean using different active processes. Seagrasses are declining worldwide at an accelerating rate because of numerous anthropogenic pressures. However, rising ocean concentrations of dissolved inorganic carbon, caused by increases in atmospheric carbon dioxide, may benefit seagrass photosynthesis. Here we compare the ability of two seagrass from the Mediterranean Sea, Posidonia oceanica (L.) Delile and Zostera marina L., to use carbon dioxide and bicarbonate at light saturation, and model how increasing concentrations of inorganic carbon affect their photosynthesis rate. pH-drift measurements confirmed that both species were able to use bicarbonate in addition to carbon dioxide, but that Z. marina was more effective than P. oceanica. Kinetic experiments showed that, compared to Z. marina, P. oceanica had a seven-fold higher affinity for carbon dioxide and a 1.6-fold higher affinity for bicarbonate. However, the maximal rate of bicarbonate uptake in Z. marina was 2.1-fold higher than in P. oceanica. In equilibrium with 410 ppm carbon dioxide in the atmosphere, the modelled rates of photosynthesis by Z. marina were slightly higher than P. oceanica, less carbon limited and depended on bicarbonate to a greater extent. This greater reliance by Z. marina is consistent with its less depleted 13C content compared to P. oceanica. Modelled photosynthesis suggests that both species would depend on bicarbonate alone at an atmospheric carbon dioxide partial pressure of 280 ppm. P. oceanica was projected to benefit more than Z. marina with increasing atmospheric carbon dioxide partial pressures, and at the highest carbon dioxide scenario of 1135 ppm, would have higher rates of photosynthesis and be more saturated by inorganic carbon than Z. marina. In both species, the proportional reliance on bicarbonate declined markedly as carbon dioxide concentrations increased and in P. oceanica carbon dioxide would become the major source of inorganic carbon.

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Seaweeds cultivation methods and their role in climate mitigation and environmental cleanup

Published 24 October 2022 Science Closed
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Seaweed cultivation is an emerging sector of food production that can full fill the future food demand of the growing population. Considering the importance, Asia is home to seven of the top ten seaweed-producing nations, and Asian countries contributed 99.1% of all seaweed cultivated for food. Besides, it can reduce the carbon budget of the ocean through seaweed farms and act as a CO2 sink. In the context of climate change mitigation, the seaweed culture is the energy crop, and during its entire life cycle can serve as a bio-filter and bio-extractor. The climate change effect can be reduced by farming seaweed on a commercial scale and it will protect the coastal area by decreasing the physical damage through damping wave energy. The seaweed can reduce eutrophication by removing excess nutrients from water bodies and releasing oxygen as a byproduct in return. The cultivation of seaweed plays an important role as the source of bioenergy for full fill the future energy requirement and it will act as clean energy through the establishment of algal biorefinery along with the seaweed cultivation site. Thus, the marine energy industrial sector moves further toward large-scale expansion of this sector by adopting energy devices to offer power for seaweed growth for biofuel operation. The current reviews provides the evidence of seaweed farming methodology adopted by different countries, as well as their production and output. To mitigate climate change by direct measures such as carbon sequestration, eutrophication risk reduction, and bioenergy, as well as through indirect measures like supplying food for cattle and reducing the strain on aquaculture. The US, Japan, and Germany lastly suggest the large-scale offshore commercial farming as a feasible climate change mitigation strategy.

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Response of the green alga Ulva prolifera grown at different irradiance levels under ocean acidification at different life cycle stages

Published 6 October 2022 Science Closed
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The effects of ocean acidification on macroalgae have been extensively studied. However, most studies focused on the adult stages, while other life cycle stages have been overlooked. To better understand the influence of the marine environment on macroalgae, their whole life cycle should be considered, especially the juvenile stage. In this study, Ulva prolifera was cultured under two CO2 concentrations (400 and 1000 ppmv) and at 10, 18, 30, and 55% of incident sunlight to assess the photosynthetic performance. Our results showed that the acidification treatment had a negative effect on growth at the juvenile stage, but a positive effect at the adult stage. The relative growth rate and effective quantum yield of PSII increased with decreased light levels, irrespective of the CO2 concentration. At the adult stage, the Chlorophyll (Chl) a, Chl b, and carotenoid contents declined under the high CO2 concentration. The protein content significantly increased at 18, 30%, and full sunlight levels under the high CO2 but not under the low CO2 concentration. Our results suggest that juveniles were less tolerant of the acidic stress compared with the adult stage, although the alga was able to increase cellular proteins in response to the acidic stress.

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Environmental response and pH tolerance of induced CO2 in Ulva rigida C. Agardh, 1823 (Chlorophyta) under controlled conditions

Published 17 August 2022 Science Closed
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The increase in integrated multitrophic aquaculture (IMTA), where seaweed (particularly Ulva rigida C. Agardh, 1823) is used as a feedstock and a wastewater scrubber in South African IMTA systems, has necessitated research into seaweed growth rates, which has subsequently increased production technologies. Seaweed growth can be increased by controlling the culture media. One of the means to control growth rate is through CO2 gas addition to culture media via aeration. This has the potential added benefit of using waste CO2 production from an alternative source to decrease overall carbon dioxide emissions. The consequence of elevated CO2 concentration on the pH of culture medium and the equivalent functional reactions in the seaweed were examined using U. rigida in flow-through systems. Toxicity investigation of Hydrogen ion concentrations were carried out on U. rigida to examine their anatomy cum functional differences arising due to CO2 exerted stress. Elevated CO2 levels and the accompanying decrease in culture media pH (4.71 – 6.67) lead to a significant decrease in biomass with varied sporulation activities. In addition, U. rigida in flow-through systems showed a gradual degeneration in specific growth rate, from day 7, at varying rates until the end of the experiment in the following sequence pH 7.20 > 8.20 > 7.50 > 7.80. The treatment set at pH 7.20 yielded the greatest specific biomass and the greatest produce. The cultured input stocking rate of 5 g.l-1 of seawater proved to be suitable for cultivation. The pH toxicity reaction was significant in predicting the suitability of seaweed cultured under CO2 induced concentrations.

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Net effect of environmental fluctuations in multiple global-change drivers across the tree of life

Published 17 August 2022 Science Closed
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Significance

Recent advances in ecology show evidence that multiple environmental drivers interact and that their impact on community and ecosystem functioning cannot be predicted from single-driver studies. However, ecologists still largely disregard the role that fluctuations in these drivers (i.e., changes above/below mean trends) play in modulating the magnitude and direction of global-change impacts. Through a 30-year quantitative review, we show that contrary to the established paradigm, additive effects are more frequent when environmental fluctuations are considered in multiple-driver (i.e., acidification, hyperpoxia and hypoxia, light, resource supply, or temperature) scenarios, although such effects are strongly dependent on trophic strategy and phylogeny. Our findings stress the need to consider environmental variability in ecological studies and conservation plans to better predict the impacts of global climate change.

Abstract

Jensen’s inequality predicts that the response of any given system to average constant conditions is different from its average response to varying ones. Environmental fluctuations in abiotic conditions are pervasive on Earth; yet until recently, most ecological research has addressed the effects of multiple environmental drivers by assuming constant conditions. One could thus expect to find significant deviations in the magnitude of their effects on ecosystems when environmental fluctuations are considered. Drawing on experimental studies published during the last 30 years reporting more than 950 response ratios (n = 5,700), we present a comprehensive analysis of the role that environmental fluctuations play across the tree of life. In contrast to the predominance of interactive effects of global-change drivers reported in the literature, our results show that their cumulative effects were additive (58%), synergistic (26%), and antagonistic (16%) when environmental fluctuations were present. However, the dominant type of interaction varied by trophic level (autotrophs: interactive; heterotrophs: additive) and phylogenetic group (additive in Animalia; additive and positive antagonism in Chromista; negative antagonism and synergism in Plantae). In addition, we identify the need to tackle how complex communities respond to fluctuating environments, widening the phylogenetic and biogeographic ranges considered, and to consider other drivers beyond warming and acidification as well as longer timescales. Environmental fluctuations must be taken into account in experimental and modeling studies as well as conservation plans to better predict the nature, magnitude, and direction of the impacts of global change on organisms and ecosystems.

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Elevated CO2 does not alter behavioural lateralization in free-swimming juvenile European sea bass (Dicentrarchus labrax) tested in groups

Published 16 August 2022 Science Closed
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We investigated left-right turning preferences of N=260 juvenile European sea bass (Dicentrarchus labrax) reared in either: ambient conditions; ocean acidification (OA) conditions; or reared in ambient conditions but tested in OA water. Groups of 10 individuals were observed alone in a circular tank and individuals’ left and right turning during free-swimming were quantified using trajectory data from video. We show that near future OA levels does not affect the number of turns made, or behavioural lateralization (turning preference), in juvenile D. labrax tested in groups.

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Diurnal fluctuations in seawater pCO2 amplify the negative effects of ocean acidification on the biotic performance of the calcifying macroalga Halimeda opuntia

Published 4 August 2022 Science Closed
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Although the adverse effects of increasing atmospheric CO2-induced ocean acidification (OA) on marine calcifying macroalgae have been widely reported, there are limited studies on how daily fluctuations in pCO2 (pH) within shallow ecosystems influence the growth and physiological performance of these calcifiers. Therefore, a 42-day laboratory mimetic experiment to determine how growth, biological performance and related carbon and nitrogen metabolic products of the calcifying macroalga, Halimeda opuntia are generated in response to fluctuating pCO2 under OA conditions (1200 ppmv) was performed. The results of present study showed that the adverse effects of OA were more determined by the adverse influence of elevated acidity (H+) on growth rates, calcification, photosynthesis and the related biotic performance of H. opuntia compared with the positive effects that higher CO2 provided. Moreover, diurnal fluctuations in pCO2 levels [with higher (nearly 8.10) and lower pH (nearly 7.40) values during day and night times, respectively] have amplified these negative influences on H. opuntia. To mitigate elevated pCO2-related stress, higher contents of free amino acids and proline were highly secreted and likely linked to protecting the integrity of algal cellular structures. The above results contribute to increasing our understanding of the biological consequences of pCO2 (pH) variability on calcifying Halimeda species and their physiological plasticity in response to further oceanic pCO2 changes.

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Biological sensitivities to high-resolution climate change projections in the California current marine ecosystem

Published 29 July 2022 Science Closed
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The California Current Marine Ecosystem is a highly productive system that exhibits strong natural variability and vulnerability to anthropogenic climate trends. Relating projections of ocean change to biological sensitivities requires detailed synthesis of experimental results. Here, we combine measured biological sensitivities with high-resolution climate projections of key variables (temperature, oxygen, and pCO2) to identify the direction, magnitude, and spatial distribution of organism-scale vulnerabilities to multiple axes of projected ocean change. Among 12 selected species of cultural and economic importance, we find that all are sensitive to projected changes in ocean conditions through responses that affect individual performance or population processes. Response indices were largest in the northern region and inner shelf. While performance traits generally increased with projected changes, fitness traits generally decreased, indicating that concurrent stresses can lead to fitness loss. For two species, combining sensitivities to temperature and oxygen changes through the Metabolic Index shows how aerobic habitat availability could be compressed under future conditions. Our results suggest substantial and specific ecological susceptibility in the next 80 years, including potential regional loss of canopy-forming kelp, changes in nearshore food webs caused by declining rates of survival among red urchins, Dungeness crab, and razor clams, and loss of aerobic habitat for anchovy and pink shrimp. We also highlight fillable gaps in knowledge, including specific physiological responses to stressors, variation in responses across life stages, and responses to multistressor combinations. These findings strengthen the case for filling information gaps with experiments focused on fitness-related responses and those that can be used to parameterize integrative physiological models, and suggest that the CCME is susceptible to substantial changes to ecosystem structure and function within this century.

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Integrated multi-trophic aquaculture mitigates the effects of ocean acidification: seaweeds raise system pH and improve growth of juvenile abalone

Published 11 July 2022 Science Closed
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Highlights

  • Integrated multi-trophic aquaculture (IMTA) with seaweeds improves abalone growth.
  • IMTA designs with high recirculation rates increase system pH.
  • Abalone growth was positively associated with pH levels in the IMTA system.
  • IMTA designs altered water chemistry and can reduce eutrophication.
  • IMTA designs can reduce the time to market for abalone from 4 to 3 years.

Abstract

Integrated multi-trophic aquaculture (IMTA) has the potential to enhance growth, reduce nutrient loads, and mitigate environmental conditions compared to traditional single-species culture techniques. The goal of this project was to develop a land-based system for the integrated culture of seaweeds and shellfish, to test the efficacy of integrated versus non-integrated designs, and to assess the potential for IMTA to mitigate the effects of climate change from ocean acidification on shellfish growth and physiology. We utilized the red abalone (Haliotis rufescens) and the red seaweed dulse (Devaleraea mollis) as our study species and designed integrated tanks at three different recirculation rates (0%, 30%, and 65% recirculation per hour) to test how an integrated design would affect growth rates of the abalone and seaweeds, modify nutrient levels, and change water chemistry. We specifically hypothesized that IMTA designs would raise seawater pH to benefit calcifying species. Our results indicated that juvenile abalone grew significantly faster in weight (22% increase) and shell area (11% increase) in 6 months in tanks with the highest recirculation rates (65%). The 65% recirculation treatment also exhibited a significant increase in mean seawater pH (0.2 pH units higher) due to the biological activity of the seaweed in the connected tanks. We found a significant positive relationship between the mean pH of seawater in the tanks and juvenile abalone growth rates across all treatments. There were no significant differences in the growth of dulse among treatments, but dulse growth did vary seasonally. Seawater phosphate and nitrate concentrations were depleted in the highest recirculation rate treatment, but ammonium concentrations were elevated, likely due to the abalone effluent. Overall, our results indicate that there are benefits to IMTA culture of seaweeds and abalone in terms of improving growth in land-based systems, which will reduce the time to market and buffer commercial abalone operations against the effects of ocean acidification during vulnerable early life stages.

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Simulated response of St. Joseph Bay, Florida, seagrass meadows and their belowground carbon to anthropogenic and climate impacts

Published 5 July 2022 Science Closed
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Highlights

  • The bio-optical model GrassLight predicted the response of the relatively stable seagrass meadows of St. Joseph Bay, Florida to future climate and anthropogenic scenarios.
  • Simulations predicted a 2–8% decline in seagrass extent with rising temperatures that was offset by a 3–11% expansion in seagrass extent in response to ocean acidification.
  • Anthropogenic changes in water quality were a bigger stressor than temperature and pH, predicting up to 21% decline in seagrass extent.
  • Ocean acidification may stimulate seagrass productivity sufficiently to offset both the negative effects of thermal stress and declining water quality on the seagrasses of St. Joseph Bay, Florida.

Abstract

Seagrass meadows are degraded globally and continue to decline in areal extent due to human pressures and climate change. This study used the bio-optical model GrassLight to explore the impact of climate change and anthropogenic stressors on seagrass extent, leaf area index (LAI) and belowground organic carbon (BGC) in St. Joseph Bay, Florida, using water quality data and remotely-sensed sea surface temperature (SST) from 2002 to 2020. Model predictions were compared with satellite-derived measurements of seagrass extent and shoot density from the Landsat images for the same period. The GrassLight-derived area of potential seagrass habitat ranged from 36.2 km2 to 39.2 km2, averaging 38.0 ± 0.8 km2 compared to an observed seagrass extent of 23.0 ± 3.0 km2 derived from Landsat (range = 17.9–27.4 km2). GrassLight predicted a mean seagrass LAI of 2.7 m2 leaf m−2 seabed, compared to a mean LAI of 1.9 m2 m−2 estimated from Landsat, indicating that seagrass density in St. Joseph Bay may have been below its light-limited ecological potential. Climate and anthropogenic change simulations using GrassLight predicted the impact of changes in temperature, pH, chlorophyll a, chromophoric dissolved organic matter and turbidity on seagrass meadows. Simulations predicted a 2–8% decline in seagrass extent with rising temperatures that was offset by a 3–11% expansion in seagrass extent in response to ocean acidification when compared to present conditions. Simulations of water quality impacts showed that a doubling of turbidity would reduce seagrass extent by 18% and total leaf area by 21%. Combining climate and water quality scenarios showed that ocean acidification may increase seagrass productivity to offset the negative effects of both thermal stress and declining water quality on the seagrasses growing in St. Joseph Bay. This research highlights the importance of considering multiple limiting factors in understanding the effects of environmental change on seagrass ecosystems.

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A regional view of the response to climate change: a meta-analysis of European benthic organisms’ responses

Published 4 July 2022 Science Closed
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Climate change is impacting organisms in every region of the world ocean by acting though on individuals in response to their local environments. Given projected future risks derived from these changes, it is becoming increasingly important to understand regional signals of how organisms respond to facilitate their governance and protection. Benthic organisms structure ecological compositions and ecosystem dynamics, therefore not only providing insights into their own response to climate change but also how ecosystems might respond to future conditions. European seas are transitional areas including boreal, warm-temperate, and subarctic waters with organisms frequently at limits of their distributions. Here, we use a meta-analytical approach to assess how calcification, growth, metabolism, photosynthesis, reproduction, and survival in European benthic organisms respond to ocean acidification and warming. Using meta-regression, we examine how study design factors influence effect-size outcomes. Longer experimental periods generally amplified the effects of climate change on taxonomic groupings and related physiological traits and against expectation do not result in acclimation. In agreement with global studies, we find that impacts vary considerably on different taxonomic groupings and their physiological traits. We found calcifying organisms are an at-risk taxon in European waters, with climate stressors decreasing growth rates, reproduction, and survival rates. Fleshy algal species demonstrate resilience to climate stressors, suggesting future European benthic ecosystems will undergo restructuring based on current climate emission pathways.

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Becoming nose-blind—climate change impacts on chemical communication

Published 31 May 2022 Science Closed
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Chemical communication via infochemicals plays a pivotal role in ecological interactions, allowing organisms to sense their environment, locate predators, food, habitats, or mates. A growing number of studies suggest that climate change-associated stressors can modify these chemically mediated interactions, causing info-disruption that scales up to the ecosystem level. However, our understanding of the underlying mechanisms is scarce. Evidenced by a range of examples, we illustrate in this opinion piece that climate change affects different realms in similar patterns, from molecular to ecosystem-wide levels. We assess the importance of different stressors for terrestrial, freshwater, and marine ecosystems and propose a systematic approach to address highlighted knowledge gaps and cross-disciplinary research avenues.

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