Posts Tagged 'Mediterranean'

Calcification response of planktic foraminifera to environmental change in the western Mediterranean Sea during the industrial era (update)

Published 2 May 2023 Science Closed
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The Mediterranean Sea sustains a rich and fragile ecosystem currently threatened by multiple anthropogenic impacts that include, among others, warming, pollution, and changes in seawater carbonate speciation associated to increasing uptake of atmospheric CO2. This environmental change represents a major risk for marine calcifiers such as planktonic foraminifera, key components of pelagic Mediterranean ecosystems and major exporters of calcium carbonate to the sea floor, thereby playing a major role in the marine carbon cycle. In this study, we investigate the response of planktic foraminifera calcification in the northwestern Mediterranean Sea on different timescales across the industrial era. This study is based on data from a 12-year-long sediment trap record retrieved in the in the Gulf of Lions and seabed sediment samples from the Gulf of Lions and the promontory of Menorca. Three different planktic foraminifera species were selected based on their different ecology and abundance: Globigerina bulloides, Neogloboquadrina incompta, and Globorotalia truncatulinoides. A total of 273 samples were weighted in both sediment trap and seabed samples.

The results of our study suggest substantial different seasonal calcification patterns across species: G. bulloides shows a slight calcification increase during the high productivity period, while both N. incompta and G. truncatulinoides display a higher calcification during the low productivity period. The comparison of these patterns with environmental parameters indicate that controls on seasonal calcification are species-specific. Interannual analysis suggests that both G. bulloides and N. incompta did not significantly reduce their calcification between 1994 and 2005, while G. truncatulinoides exhibited a constant and pronounced increase in its calcification that translated in an increase of 20 % of its shell weight. The comparison of these patterns with environmental data reveals that optimum growth conditions affect positively and negatively G. bulloides and G. truncatulinoides calcification, respectively. Sea surface temperatures (SSTs) have a positive influence on N. incompta and G. truncatulinoides calcification, while carbonate system parameters appear to affect positively the calcification of three species in the Gulf of Lions throughout the 12-year time series.

Finally, comparison between sediment trap data and seabed sediments allowed us to assess the changes of planktic foraminifera calcification during the late Holocene, including the pre-industrial era. Several lines of evidence indicate that selective dissolution did not bias the results in any of our data sets. Our results showed a weight reduction between pre-industrial and post-industrial Holocene and recent data, with G. truncatulinoides experiencing the largest weight loss (32 %–40 %) followed by G. bulloides (18 %–24 %) and N. incompta (9 %–18 %). Overall, our results provide evidence of a decrease in planktic foraminifera calcification in the western Mediterranean, most likely associated with ongoing ocean acidification and regional SST trends, a feature consistent with previous observations in other settings of the world’s oceans.

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Morpho-anatomical, and chemical characterization of some calcareous Mediterranean red algae species

Published 26 April 2023 Science Closed
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Climatic changes are anticipated to have a detrimental effect on calcifying marine species. Calcareous red algae may be especially vulnerable to seasonal variations since they are common and essential biologically, but there is little research on the morpho-anatomical, and chemical characterization of such species. This study conducted the seasonal investigation of the three dominant Mediterranean calcified red algae. Morphological and 18S rRNA analysis confirmed the identification of collected species as Corallina officinalis, Jania rubens, and Amphiroa rigida. In general, C. officinalis was represented in the four seasons and flourishing maximum in autumn (70% of total species individuals). While J. rubens species was represented in winter, autumn, and spring and completely absent in summer. A. rigida was abundant only in the summer season by 40%. A full morphological and anatomical description of these species were examined, and their chemical compositions (carbohydrate, protein, lipid, pigments, and elements content) were assessed in different seasons, where carbohydrates were the dominant accumulates followed by proteins and lipids. Pearson correlation analysis confirmed a positive correlation between salinity level and nitrogenous nutrients of the seawater with the pigment contents (phycobiliproteins, carotenoids, and chlorophyll a) of the studied seaweeds. The results proved that calcified red algae were able to deposit a mixture of calcium carbonates such as calcite, vaterite, calcium oxalate, calcite-III I calcium carbonate, and aragonite in variable forms depending on the species.

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Abundance and size structure of Patella spp. (Mollusca, Gastropoda) under ocean acidification conditions at CO2 vents (Ischia Island, Italy)

Published 25 April 2023 Science Closed
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Abundance and size structure of Patella spp. were studied at Ischia Island (Tyrrhenian Sea) in two populations living at CO2 vents off Castello Aragonese, under natural ocean acidification (OA) conditions (pH 7.4-7.9), and three control populations in sites characterized by normal pH conditions (pH 8.1). Both CO2 vent populations had 95% of heavily corroded shells and significant lower abundances than control populations, while the size structure showed individuals of higher dimensions (>2 cm), fewer small specimens (0-1 cm) and lack of new recruits in the vent’s populations subjected to OA conditions. These results confirm that, although with low densities, limpets thrive under OA conditions, and exhibit larger sizes, than in control areas, but a reduced recruitment of juveniles. This fact suggests a habitat selection only by adult specimens likely more robust to OA then juveniles, and the potential influence of other indirect factors, such as the amount and quality of the plant food (higher N content), which seems higher under OA conditions, or a reduced predation, that can explain the larger limpet’s size.

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Ocean acidification as a governance challenge in the Mediterranean Sea: impacts from aquaculture and fisheries

Published 25 April 2023 Science Closed
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Despite the progress in the international and regional governance efforts at the level of climate change, ocean acidification (OA) remains a global problem with profoundly negative environmental, social, and economical consequences. This requires extensive mitigation and adaptation effective strategies that are hindered by current shortcomings of governance. This multidisciplinary chapter investigates the risks of ocean acidification (OA) for aquaculture and fisheries in the Mediterranean Sea and its sub-basins and the role of regional adaptive governance to tackle the problem. The identified risks are based on the biological sensitivities of the most important aquaculture species and biogenic habitats and their exposure to the current and future predicted (2100) RCP 8.5 conditions. To link OA exposure and biological sensitivity, we produced spatially resolved and depth-related pH and aragonite saturation state exposure maps and overlaid these with the existing aquaculture industry in the coastal waters of the Mediterranean basin to demonstrate potential risk for the aquaculture in the future. We also identified fisheries’ vulnerability through the indirect effects of OA on highly sensitive biogenic habitats that serve as nursery and spawning areas, showing that some of the biogenic habitats are already affected locally under existing OA conditions and will be more severely impacted across the entire Mediterranean basin under 2100 scenarios. This provided a regional vulnerability assessment of OA hotspots, risks and gaps that created the baseline for discussing the importance of adaptive governance and recommendations for future OA mitigation/adaptation strategies. By understanding the risks under future OA scenarios and reinforcing the adaptability of the governance system at the science-policy interface, best informed, “situated” management response capability can be optimised to sustain ecosystem services.

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How ocean warming and acidification affect the life cycle of six worldwide commercialised sea urchin species: a review

Published 19 April 2023 Science Closed
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Ongoing global changes are expected to affect the worldwide production of many fisheries and aquaculture systems. Because invertebrates represent a relevant industry, it is crucial to anticipate challenges that are resulting from the current environmental alterations. In this review, we rely on the estimated physiological limits of six commercialised species of sea urchins (Loxechinus albus, Mesocentrotus franciscanus, Paracentrotus lividus, Strongylocentrotus droebachiensis, Strongylocentrotus intermedius and Strongylocentrotus purpuratus) to define the vulnerability (or resilience) of their populations facing ocean warming and acidification (OW&A). Considering that coastal systems do not change uniformly and that the populations’ response to stressors varies depending on their origin, we investigate the effects of OW&A by including studies that estimate future environmental mutations within their distribution areas. Cross-referencing 79 studies, we find that several sea urchin populations are potentially vulnerable to the predicted OW&A as environmental conditions in certain regions are expected to shift beyond their estimated physiological limit of tolerance. Specifically, while upper thermal thresholds seem to be respected for L. albus along the SW American coast, M. franciscanus and S. purpuratus southern populations appear to be vulnerable in NW America. Moreover, as a result of the strong warming expected in the Arctic and sub-Arctic regions, the local productivity of S. droebachiensis is also potentially largely affected. Finally, populations of S. intermedius and P. lividus found in northern Japan and eastern Mediterranean respectively, are supposed to decline due to large environmental changes brought about by OW&A. This review highlights the status and the potential of local adaptation of a number of sea urchin populations in response to changing environmental conditions, revealing possible future challenges for various local fishing industries.

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The potential effect of anthropogenic salinization and ocean acidification on lightning flash intensity over the Mediterranean Sea

Published 17 April 2023 Science Closed
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Description

This dataset contains the results of experiments designed to test the effect of changes un Mediterranean seawater salinity and corresponding changes ub total alkalinity on the intensity of an electrical spark discharged into the water surface (LFI). The data includes the results of a number of experiments that tested the the dependence of LFI on different levels of salinity that were obtained by additions of deionized water (dilution) and NaOH to Mediterranean seawater samples, followed by bubbling of the seawater with CO2 and resulting in consecutive decreases in pH. The results of these experiments show that LFI is positively dependent on the salinity and total alkalinity of seawater and negatively dependent on pH.

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Spatial variability of lightning intensity over the Mediterranean sea correlates with seawater properties

Published 17 April 2023 Science Closed
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The divergence of total alkalinity (TA) from conservation with salinity (S) and relatively acidic conditions (pH) in surface seawater was suggested to explain the high prevalence of lightning superbolts in the Mediterranean sea, North sea and upwelling regions of the oceans. In this study we tested the combined effects of changes in S, TA and pH of Mediterranean sea surface water on the intensity of laboratory generated electrical sparks, which are considered to be analogous to cloud to sea-surface intensity of lightning discharges. The experimental results were used to develop a multivariate linear equation (MLE) of Lightning Flash Intensity (LFI) as a function of S, TA/S and pH. This relation was validated with wintertime (DJF) LFI measurements along a Mediterranean sea zonal profile during the period 2009–2020 compared to corresponding climate model outputs of S, TA and pH. Based on the resulting MLE, the combined effects of climate change, ocean acidification and the damming of the Nile, may have increased LFI in the Levantine Sea by 16 ± 14% until now relative to the pre-Aswan Dam period. Furthermore, assuming that salinization and acidification of the Levantine Sea will continue at current trends, the LFI is predicted to increase by 25 ± 13% by the year 2050.

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Volcanic-associated ecosystems of the Mediterranean Sea: a systematic map and an interactive tool to support their conservation

Published 11 April 2023 Science Closed
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Background

Hydrothermal vents, cold seeps, pockmarks and seamounts are widely distributed on the ocean floor. Over the last fifty years, the knowledge about these volcanic-associated marine ecosystems has notably increased, yet available information is still limited, scattered, and unsuitable to support decision-making processes for the conservation and management of the marine environment.

Methods

Here we searched the Scopus database and the platform Web of Science to collect the scientific information available for these ecosystems in the Mediterranean Sea. The collected literature and the bio-geographic and population variables extracted are provided into a systematic map as an online tool that includes an updated database searchable through a user-friendly R-shiny app.

Results

The 433 literature items with almost one thousand observations provided evidence of more than 100 different volcanic-associated marine ecosystem sites, mostly distributed in the shallow waters of the Mediterranean Sea. Less than 30% of these sites are currently included in protected or regulated areas. The updated database available in the R-shiny app is a tool that could guide the implementation of more effective protection measures for volcanic-associated marine ecosystems in the Mediterranean Sea within existing management instruments under the EU Habitats Directive. Moreover, the information provided in this study could aid policymakers in defining the priorities for the future protection measures needed to achieve the targets of the UN Agenda 2030.

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Elevated river inputs of the total alkalinity and dissolved inorganic carbon in the Northern Adriatic Sea

Published 5 April 2023 Science Closed
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The response of coastal systems to global acidification depends strongly on river inputs, which can alter the total alkalinity (AT) and dissolved inorganic carbon (DIC) in seawater. The northern Adriatic Sea (NAd) is a shallow continental shelf region that currently receives about 15% of the total freshwater input in the Mediterranean Sea, where the role of riverine discharges on the carbonate system has been poorly studied. In particular, river discharges can alter the carbonate system in the sea, affecting both the equilibrium chemistry and biological processes. For the main rivers flowing into the NAd (the Po, Adige, Brenta, Piave, Livenza, Tagliamento, Isonzo, Timavo and Rižana), data were collected for the pH, concentrations of the total alkalinity (AT), Ca2+ and Mg2+ and the isotopic ratio of stable carbon in the dissolved inorganic carbon (δ13CDIC). The DIC fluxes were estimated using the THINCARB (THermodynamic modeling of INOrganic CARBon) model for the compilation of the AT and pH data. The results show that the total transport of the AT in the rivers was 205 Gmol yr−1 while the transport of the DIC was 213 Gmol yr−1, of which about 70% was from the Po River. About 97% of the DIC in the river waters was in the form of bicarbonates. The high Mg2+/Ca2+ ratios indicate that dolomite weathering is predominant in the Adige, Piave, and Livenza river basins, while lower ratios in the Timavo and Rižana rivers indicate a greater proportion of calcite. The mean δ13C-DIC value was estimated to be −10.0 ± 1.7 ‰, a value nowadays considered typical for the DIC flux inputs in oceanic carbon cycle modeling. The DIC flux depends on the mineral weathering and biological activity in each river basin. However, these natural processes can be modified by anthropogenic disturbances that should be better quantified.

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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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Thanks mum. Maternal effects in response to ocean acidification of sea urchin larvae at different ecologically relevant temperatures

Published 3 March 2023 Science Closed
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Graphical abstract

Highlights

  • Ocean acidification and temperature differently influence larval development of Arbacia lixula and Paracentrotus lividus.
  • Larvae of the two A. lixula populations (ambient-pH vs vent sites) respond differently to ocean acidification and temperature.
  • Maternal buffer effect was observed in response to ocean acidification and temperature in both species.
  • A. lixula seems to be more tolerant to changes in temperature than P. lividus.

Abstract

Juvenile stages of marine species might be more vulnerable than adults to climate change, however larval vulnerability to predictable environmental changes can be mitigated by parental anticipatory buffer effects occurring during gametogenesis. In this study, ocean acidification effect were investigated on larval growth of two sea urchins, Arbacia lixula and Paracentrotus lividus, at different temperature levels. Results showed that altered pH and temperature affected larval development in both species, with significant length reductions of spicules and significant increases in abnormal larvae. Detrimental effects of reduced pH and high temperature were however dependent on the mother. Furthermore, the responses of A. lixula larvae from the ambient site (pH ∼ 8.0) were compared with those of larvae obtained from mothers collected from a natural CO2 vent (pH ∼ 7.7) in Ischia. Comparisons highlighted a transgenerational response, as the CO2 vent larvae proved to be more resilient to reduced pH, although more sensitive to increased temperature.

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Acclimatization of a coral-dinoflagellate mutualism at a CO2 vent

Published 14 February 2023 Science Closed
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Ocean acidification caused by shifts in ocean carbonate chemistry resulting from increased atmospheric CO2 concentrations is threatening many calcifying organisms, including corals. Here we assessed autotrophy vs heterotrophy shifts in the Mediterranean zooxanthellate scleractinian coral Balanophyllia europaea acclimatized to low pH/high pCO2 conditions at a CO2 vent off Panarea Island (Italy). Dinoflagellate endosymbiont densities were higher at lowest pH Sites where changes in the distribution of distinct haplotypes of a host-specific symbiont species, Philozoon balanophyllum, were observed. An increase in symbiont C/N ratios was observed at low pH, likely as a result of increased C fixation by higher symbiont cell densities. δ13C values of the symbionts and host tissue reached similar values at the lowest pH Site, suggesting an increased influence of autotrophy with increasing acidification. Host tissue δ15N values of 0‰ strongly suggest that diazotroph N2 fixation is occurring within the coral tissue/mucus at the low pH Sites, likely explaining the decrease in host tissue C/N ratios with acidification. Overall, our findings show an acclimatization of this coral-dinoflagellate mutualism through trophic adjustment and symbiont haplotype differences with increasing acidification, highlighting that some corals are capable of acclimatizing to ocean acidification predicted under end-of-century scenarios.

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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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Chapter 11 – Mediterranean Sea general biogeochemistry

Published 5 January 2023 Science Closed
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This chapter gives an overview of the general biogeochemistry in the Mediterranean Sea explaining the particularities of the main biogeochemical variables and the physical, biological, and geochemical processes driving their distribution in the main basins of this marginal sea. Each subsection focuses on one essential variable, starting from dissolved oxygen and following inorganic nutrients, dissolved organic carbon and the CO2 system. A brief overview on the utility of those biogeochemical variables to identify water masses is also given. The chapter concludes with a summary of the projections and threats on biogeochemistry in the Mediterranean Sea under different future climate change scenarios.

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Calcareous nannoplankton response to a high CO2 world: evidence from sediment traps (Aegean and Ionian Seas) and Pliocene paleofluxes

Published 20 December 2022 Science Closed
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One of the most enigmatic features of long-term Cenozoic climatic evolution, with some analogue potential for present/ future global climate change, is the last sustained warm and high-atmospheric CO2 interval in Earth’s history. The Pliocene is the most recent period in Earth’s history when average global temperature, atmospheric CO2 concentrations, and sea level were higher than today. This time period offers an appropriate interval to understand the climatic processes of a warm, high CO2 world, similar to the ongoing climatic conditions. Also, due to the high absorption capacity of the Eastern Mediterranean to anthropogenic CO2, the study area (Aegean and Ionian seas) is an ideal location to assess the impact of anthropogenic ocean acidification on calcifying organisms. The main objective of the present study is to investigate calcareous nannoplankton fluxes in the NE Mediterranean Sea as recorded by sediment traps and paleoceanographic records. The study material is collected from sediment traps in the Aegean and Ionian Seas and from the sedimentary record of the Eastern Mediterranean Deep Sea Drilling Project (DSDP Leg42A, Site 378). In the present study, coccolith fluxes from sediment traps were examined and compared in different sites of the Aegean and Ionian Seas. Data were compared in order to define the spatial and seasonal variability in assemblage composition and coccolithophore fluxes. The present study reflects in the coccolithophore export productivity the context of biogenic sedimentation in the water column. Furthermore, a water and sediment trap samples (N.Aegean Sea) analysis was carried out and through the comparison with data derived from surface sediment of the same site, valuable information were provided on the alterations observed in coccolithophore assemblage composition during their export from the euphotic zone to the seafloor. In addition, the morphometric analysis of coccoliths contributed to the investigation of water masses in the water column of the North Aegean Sea. In the DSDP core data we focus on the “warm Pliocene” interval, after the Zanclean “flooding” phenomenon in the Aegean after the Messinian Mediterranean Salinity Crisis (Zanclean reflooding). According to the detailed biostratigraphy and the derived age model, this study presents a composite dataset of the two boreholes of DSDP-Leg42A-Site 378 for the interval 3.8-5.08Ma. Subsequently, we studied how coccolithophores adapted to the Pliocene environment by quantifying their abundance through paleofluxes, species composition and correlation with geochemical paleo-indices analyses performed on the core material. In addition, the DSDP sedimentary record provided evidence on the Zanclean reflooding mechanism in the Cretan Basin. This study aims to improve our understanding of long-term adaptation strategies of calcareous nannoplankton in warm, high-CO2 climates by combining present-day evidence with Lower Pliocene fossil time series.

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Shelled pteropod abundance and distribution across the Mediterranean Sea during spring

Published 16 December 2022 Science Closed
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Highlights

  • First estimate of pteropod distribution across the Mediterranean Sea in spring.
  • Highest abundance recorded in the oligotrophic Eastern Mediterranean basin.
  • Temperature, aragonite saturation, oxygen and salinity main drivers of distribution.
  • Pteropods and planktic foraminifera are inversely distributed in the Med Sea.

Abstract

Thecosome pteropods are a dominant group of calcifying pelagic molluscs and an important component of the food web. In this study, we characterise spring pteropod distribution throughout the Mediterranean Sea, an understudied region for this common group of marine calcifying organisms. This semi-enclosed sea is rapidly changing under climatic and anthropogenic forcings. The presence of surface water biogeochemical gradients from the Atlantic Ocean/Gibraltar Strait to the Eastern Mediterranean Sea allowed us to investigate pteropod distribution and their ecological preferences. In the ultra-oligotrophic Eastern Mediterranean Sea, we found the mean upper 200 m pteropod standing stock of 2.13 ind. m-3 was approximately 5x greater than the Western basin (mean 0.42 ind. m-3). Where standing stocks were high, pteropods appeared largely in the same family grouping belonging to Limacinidae. Temperature, O2 concentration, salinity, and aragonite saturation (Ωar) explain 96% of the observed variations in the community structure at the time of sampling, suggesting that pteropods might show a preference for environmental conditions with a lower energetic physiological demand. We also document that pteropods and planktonic foraminifera have an opposite geographical distribution in the Mediterranean Sea. Our findings indicate that in specific pelagic ultra-oligotrophic conditions, such as the Eastern Mediterranean Sea, different feeding strategies could play an important role in regulating calcifying zooplankton distribution.

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Calcium isotope ratios of malformed foraminifera reveal biocalcification stress preceded Oceanic Anoxic Event 2

Published 16 December 2022 Science Closed
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Ocean acidification causes biocalcification stress. The calcium isotope composition of carbonate producers can archive such stress because calcium isotope fractionation is sensitive to precipitation rate. Here, we synthesize morphometric observations of planktic foraminifera with multi-archive calcium isotope records from Gubbio, Italy and the Western Interior Seaway spanning Cretaceous Ocean Anoxic Event 2 (~94 million years ago). Calcium isotope ratios increase ~60 thousand years prior to the event. The increase coincides with foraminiferal abnormalities and correlates with existing proxy records for carbon dioxide release during large igneous province volcanism. The results highlight Ocean Anoxic Event 2 as a geologic ocean acidification analog. Moreover, decreasing calcium isotope ratios during the event provide evidence for ocean alkalinization, which could have shifted air-sea carbon dioxide partitioning. These data offer an explanation for the Plenus Cold Event and further have implications for refining ocean alkalinity enhancement, a leading anthropogenic carbon dioxide removal strategy.

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Responses of the macroalga Ulva prolifera Müller to ocean acidification revealed by complementary NMR- and MS-based omics approaches

Published 9 December 2022 Science Closed
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Ocean acidification (OA) is a dramatic perturbation of seawater environments due to increasing anthropogenic emissions of CO2. Several studies indicated that OA frequently induces marine biota stress and a reduction of biodiversity. Here, we adopted the macroalga Ulva prolifera as a model and applied a complementary multi-omics approach to investigate the metabolic profiles under normal and acidified conditions. Our results show that U. prolifera grows at higher rates in acidified environments. Consistently, we observed lower sucrose and phosphocreatine concentrations in response to a higher demand of energy for growth and a higher availability of essential amino acids, likely related to increased protein biosynthesis. In addition, pathways leading to signaling and deterrent compounds appeared perturbed. Finally, a remarkable shift was observed here for the first time in the fatty acid composition of triglycerides, with a decrease in the relative abundance of PUFAs towards an appreciable increase of palmitic acid, thus suggesting a remodeling in lipid biosynthesis. Overall, our studies revealed modulation of several biosynthetic pathways under OA conditions in which, besides the possible effects on the marine ecosystem, the metabolic changes of the alga should be taken into account considering its potential nutraceutical applications.

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Seasonal dynamics and annual budget of dissolved inorganic carbon in the northwestern Mediterranean deep convection region

Published 28 November 2022 Science Closed
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Deep convection plays a key role in the circulation, thermodynamics and biogeochemical cycles in the Mediterranean Sea, considered as a hotspot of biodiversity and climate change. In the framework of the DEWEX (Dense Water Experiment) project, the seasonal cycle and annual budget of dissolved inorganic carbon in the deep convection area of the northwestern Mediterranean Sea are investigated over the period September 2012–September 2013, using a 3-dimensional coupled physical-biogeochemical-chemical modeling approach. We estimate that the northwestern Mediterranean Sea deep convection region was a moderate sink of CO2 for the atmosphere over the study period. The model results show the reduction of CO2 uptake during deep convection, and its increase during the abrupt spring phytoplankton bloom following the deep convection events. We highlight the dominant role of both biological and physical flows in the annual dissolved inorganic carbon budget. The upper layer of the northwestern deep convection region gained dissolved inorganic carbon through vertical physical supplies and, to a lesser extent, air-sea flux, and lost dissolved inorganic carbon through lateral transport and biological fluxes. The region, covering 2.5 % of the Mediterranean, acted as a source of dissolved inorganic carbon for the surface and intermediate water masses of the western and southern Western Mediterranean Sea and could contribute up to 10 and 20 % to the CO2 exchanges with the Eastern Mediterranean Sea and the Atlantic Ocean.

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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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