Posts Tagged 'phanerogams'

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How does ocean acidification affect Zostera marina during a marine heatwave?

Published 22 August 2023 Science Closed
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Highlights

  • Under extreme conditions Z. marina grows in both leaf length and wet mass.
  • Increasing CO2 levels for Z. marina at high temperatures may stimulate growth.
  • Extremely high temperatures inhibit sucrose and starch synthesis in Z. marina.
  • Out of 223 identified differentially expressed genes 70 were upregulated.
  • Glycolysis and the TCA cycle controlling genes and metabolites were upregulated.

Abstract

Extreme ocean events caused by global warming, such as marine heatwaves (MHWs) and ocean acidification (OA), are projected to intensify. A combination of extreme events may have severe consequences for marine ecosystems. Zostera marina was selected to understand how seagrass adapts to OA in extremely hot conditions. By combining morphology, transcriptomics, and metabolomics under mesoscale experimental conditions, we systematically investigated the response characteristics of Z. marina. Extremely high temperatures had a pronounced effect on growth, and the combined effect of OA mitigated the inhibitory effect of MHW. Both transcriptomic and metabolomic results showed that Z. marina resisted OA and MHW by upregulating the TCA cycle, glycolysis, amino acid metabolism, and relevant genes, as well as by activating the antioxidant system. The results of this study serve to improve our understanding of dual effects of factors of climate change on seagrass and may be used to direct future management and conservation efforts.

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Seasonal production dynamics of high latitude seaweeds in a changing ocean: implications for bottom-up effects on temperate coastal food webs

Published 10 August 2023 Science Closed
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As the oceans absorb excess heat and CO2 from the atmosphere, marine primary producers face significant changes to their abiotic environments and their biotic interactions with other species. Understanding the bottom-up consequences of these effects on marine food webs is essential to informing adaptive management plans that can sustain ecosystem and cultural services. In response to this need, this dissertation provides an in-depth consideration of the effects of global change on foundational macroalgal (seaweed) species in a poorly studied, yet highly productive region of our world’s oceans. To explore how seaweeds within seasonally dynamic giant kelp forest ecosystems will respond to ocean warming and acidification, I employ a variety of methods: year-round environmental monitoring using an in situ sensor array, monthly subtidal community surveys, and a series of manipulative experiments. I find that a complementary phenology of macroalgal production currently characterizes these communities, providing complex habitat and a nutritionally diverse energy supply to support higher trophic levels throughout the year. I also find that future ocean warming and acidification will lead to substantial shifts in the phenology, quantity and quality of macroalgal production in these systems. My results suggest that the giant kelp Macrocystis pyrifera may be relatively resilient to the effects of global change in future winter and summer seasons at high latitudes. In contrast, the calcifying coralline algae Bossiella orbigniana and Crusticorallina spp. and the understory kelps Hedophyllum nigripes and Neoagarum fimbriatum will experience a suite of negative impacts, especially in future winter conditions. The resulting indirect effects on macroalgal-supported coastal food webs will be profound, with projected reductions in habitat and seasonal food supply on rocky reefs. Coming at a time of heightened interest in seaweed production potential at high latitudes, this dissertation provides a comprehensive evaluation of the future of these foundational organisms in a changing environment.

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Seagrass Thalassia hemprichii and associated bacteria co-response to the synergistic stress of ocean warming and ocean acidification

Published 21 July 2023 Science Closed
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Seagrass meadows play vital ecological roles in the marine ecosystem. Global climate change poses considerable threats to seagrass survival. However, it is unclear how seagrass and its associated bacteria will respond under future complex climate change scenarios. This study explored the effects of ocean warming (+2 °C) and ocean acidification (−0.4 units) on seagrass physiological indexes and bacterial communities (sediment and rhizosphere bacteria) of the seagrass Thalassia hemprichii during an experimental exposure of 30 days. Results demonstrated that the synergistic effect of ocean warming and ocean acidification differed from that of one single factor on seagrass and the associated bacterial community. The seagrass showed a weak resistance to ocean warming and ocean acidification, which manifested through the increase in the activity of typical oxidoreductase enzymes. Moreover, the synergistic effect of ocean warming and ocean acidification caused a significant decrease in seagrass’s chlorophyll content. Although the bacterial community diversity exhibited higher resistance to ocean warming and ocean acidification, further bacterial functional analysis revealed the synergistic effect of ocean warming and ocean acidification led to significant increases in SOX-related genes abundance which potentially supported the seagrass in resisting climate stress by producing sulfates and oxidizing hydrogen sulfide. More stable bacterial communities were detected in the seagrass rhizosphere under combined ocean warming and ocean acidification. While for one single environmental stress, simpler networks were detected in the rhizosphere. In addition, the observed significant correlations between several modules of the bacterial community and the physiological indexes of the seagrass indicate the possible intimate interaction between seagrass and bacteria under ocean warming and ocean acidification. This study extends our understanding regarding the role of seagrass associated bacterial communities and sheds light on both the prediction and preservation of the seagrass meadow ecosystems in response to global climate change.

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The effect of differences pH of waters on the growth rate of seagrass of Cymodocea rotundata (in Indonesian)

Published 20 July 2023 Science Closed
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The continued use of fossil fuels will increase the concentration of carbon dioxide (CO2) in the atmosphere. Ocean acidification occurs due to CO2 in the atmosphere diffusing into the oceans. The oceans are able to absorb CO2 in the atmosphere as much as 35 % more which causes a decrease in ocean pH. Seagrass Cymodocea rotundata is a type of seagrass that can be found growing in tropical waters. This situation raises concerns about the possible impact on the growth of seagrass C. rotundata. This study aims to analyze the content of nitrate, phosphate and potassium and the growth of seagrass C. rotundata which includes the growth of leaves, rhizomes and roots of C. rotundata against differences in pH. The study used an experimental method with a completely randomized design using a random table. A total of 15 jars with a diameter of 20 cm and a height of 25 cm were used with 3 treatments, each treatment was repeated 5 times. The results of the linear regression test showed that pH had an effect on nitrate concentrations, and had a strong effect on phosphate and potassium concentrations. The highest growth rate of C. rotundata seagrass leaves in the control ranged from 0.50–1.29 mm/day while the lowest at low pH ranged from 0.07–0.73 mm/day. The growth rate of seagrass rhizomes horizontally and vertically was highest at low pH while the lowest was at control pH. The highest growth rate of seagrass roots at low pH ranged from 0.20–0.90 mm/day. while the lowest was in the control ranged from 0.13–0.43 mm/day. pH also affects the growth rate of leaves, rhizomes and seagrass roots of C. rotundata. The lower the pH, the lower the leaf growth rate, in contrast to rhizomes and roots, the lower the pH, the higher the growth rate.

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The potential role of Posidonia oceanica for mitigating acidification on coastal waters of Europe

Published 12 July 2023 Science Closed
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Ocean acidification is a major environmental concern that has significant ecological., economic, and social implications. The plantation and restoration of seagrass meadows in coastal waters, specifically Posidonia oceanica, is one possible method to combat ocean acidification and has the potential to have a significant positive impact on the marine environment and the overall state of the biosphere. As there has been a decline of Posidonia oceanica of about 30% in the Mediterranean Sea over the past three decades to about 1.2 mio ha in the Mediterranean Sea, the positive effects of the sea grass have diminished due to anthropogenic influence. Still, its importance as a carbon sink should not be underestimated. By using recent literature and different studies that have been analysed of the capacity of sea grass to mitigate the impacts of ocean acidification and the effects on the marine ecosystems, supported by several experiments that have been conducted, this thesis demonstrated the importance of Posidonia oceanica. The experiments showed that seagrass ecosystems have higher pH than ecosystems without seagrass, with a mean difference of 0.43. As the pH is interlocked with the CO2-levels and the oxygen levels, also experiments on these factors have been conducted. In general, the concentration of oxygen with P. oceanica present is 2mg/L higher than without. Equally, the CO2 concentration was lower with P. oceanica present. The Posidonia oceanica meadows present in the Mediterranean Sea are able to fixate about 13,3 mio tons of CO2, which is equal to 0,3% of Europeans CO2 emissions. About 2,8 mio tons of CO2 are sequestered by the sea grass, which is about 0,07% of European CO2 emissions. Furthermore, recent plantation efforts show the successful restoration of seagrass meadows and their overall benefits for the regional environment. Overall, this paper provides valuable insights into the potential role of seagrass meadows in mitigating ocean acidification and improving marine biosystems while providing specific numbers to support its findings.

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Marine macroinvertebrate ecosystem services under changing conditions of seagrasses and mangroves

Published 5 June 2023 Science Closed
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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.

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

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