Search

Ocean acidification is considered a major threat to marine ecosystems and may particularly affect calcifying organisms such as corals, foraminifera and coccolithophores. Here we investigate the impact of elevated pCO2 and lowered pH on growth and calcification in the common calcareous dinoflagellate Thoracosphaera heimii. We observe a substantial reduction in growth rate, calcification and cyst stability of T. heimii under elevated pCO2. Furthermore, transcriptomic analyses reveal CO2 sensitive regulation of many genes, particularly those being associated to inorganic carbon acquisition and calcification. Stable carbon isotope fractionation for organic carbon production increased with increasing pCO2 whereas it decreased for calcification, which suggests interdependence between both processes. We also found a strong effect of pCO2 on the stable oxygen isotopic composition of calcite, in line with earlier observations concerning another T. heimii strain. The observed changes in stable oxygen and carbon isotope composition of T. heimii cysts may provide an ideal tool for reconstructing past seawater carbonate chemistry, and ultimately past pCO2. Although the function of calcification in T. heimii remains unresolved, this trait likely plays an important role in the ecological and evolutionary success of this species. Acting on calcification as well as growth, ocean acidification may therefore impose a great threat for T. heimii.

12 pages, 3 figures, Climate change is already transforming the seascapes of our oceans by changing the energy availability and the metabolic rates of the organisms. Among the ecosystem-engineering species that structure the seascape, marine animal forests (MAFs) are the most widespread. These habitats, mainly composed of suspension feeding organisms, provide structural complexity to the sea floor, analogous to terrestrial forests. Because primary and secondary productivity is responding to different impacts, in particular to the rapid ongoing environmental changes driven by climate change, this paper presents some directions about what could happen to different MAFs depending on these fast changes. Climate change could modify the resistance or resilience of MAFs, potentially making them more sensitive to impacts from anthropic activities (i.e. fisheries and coastal management), and vice versa, direct impacts may amplify climate change constraints in MAFs. Such changes will have knock-on effects on the energy budgets of active and passive suspension feeding organisms, as well as on their phenology, larval nutritional condition, and population viability. How the future seascape will be shaped by the new energy fluxes is a crucial question that has to be urgently addressed to mitigate and adapt to the diverse impacts on natural system, We also thank the Marie Curie International Outgoing Fellowship project ANIMAL FOREST HEALTH (Grant Agreement Number 327845). This work contributes to the ICTA “Unit of Excellence” (MinECo, MDM2015-0552). We are also grateful with the CALMED project (CTM2016-79547-R) and the AGAUR Generalitat de Catalunya (MERS, 2017 SGR 1588). SR and MS thanks the CAPES-Print Programme and CNPq Research Productivity Fellowship (Brazil)

Bramanti, Lorenzo ... et al.-- 12 pages, 4 figures, 3 tables, supporting information additional may be found in the online version of this article: http://onlinelibrary.wiley.com/doi/10.1111/gcb.12171/suppinfo, The mean predicted decrease of 0.3 to 0.4 pH units in the global surface ocean by the end of the century has prompted urgent research to assess the potential effects of ocean acidification on the marine environment, with strong emphasis on calcifying organisms. Among them, the Mediterranean red coral (Corallium rubrum) is expected to be particularly susceptible to acidification effects, due to the elevated solubility of its Mg-calcite skeleton. This, together with the large overexploitation of this species, depicts a bleak future for this organism over the next decades. In this study, we evaluated the effects of low pH on this species from aquaria experiments. Several colonies of C. rubrum were long-term maintained for 314 days in aquaria at two different pH levels (8.10 and 7.81, pHT). Calcification rate, spicule morphology, major biochemical constituents (protein, carbohydrates and lipids) and fatty acids composition were measured periodically. Exposure to lower pH conditions caused a significant decrease in the skeletal growth rate in comparison to the control treatment. Similarly, the spicule morphology clearly differed between both treatments at the end of the experiment, with aberrant shapes being observed only under the acidified conditions. On the other hand, while total organic matter was significantly higher under low pH conditions, no significant differences were detected between treatments regarding total carbohydrate, lipid, protein and fatty acid composition. However, the lower variability found among samples maintained in acidified conditions relative to controls, suggests a possible effect of pH decrease on the metabolism of the colonies. Our results show, for the first time, evidence of detrimental ocean acidification effects on this valuable and endangered coral specie, The research has been funded by the EC 7th FP (grant agreement 265103, Project MedSeA) and by the Spanish Ministry of Economy and Competitiveness (MINECO; CTM2009-08849, Project ACDC). The authors are grateful for the invaluable support of the Cap de Creus Marine Protected Area staff. [...] L.B. was supported by a Marie Curie IEF fellowship (EC7th FP, Project nº 221072), J.M. by a FPI studentship (BES-2007-16537), M.G. by of Erasmus Mundus scolarship (contract no. JEMES European UAB 2009/No.3) and S.R. by a Ramón y Cajal Contract (RyC-2007-01327) from MINECO. US National Science Foundation grant OCE 08-44785 provided support to L.B. during part of the writing of manuscript. This is a contribution from the Marine Biogeochemistry and Global Change research group, funded by Generalitat de Catalunya through grant 2009SGR142

BackgroundThere is a scarcity of long time-span and geographically wide research on the health status of Corallium rubrum, including limited research on its historical ecology and carbon sequestration capacity.ObjectivesTo reconstruct the temporal trends of the most reported C. rubrum population parameters in the Northwestern Mediterranean Sea and to determine the changes in total carbon sequestration by this species.Data sourcesQuantitative and qualitative, academic and grey documents were collected from scientific web browsers, scientific libraries, and requests to scientists.Study eligibility criteriaDocuments with original information of basal diameter, height and/or weight per colony, with a depth limit of 60 m in the Catalan and Ligurian Seas were analyzed.Synthesis methodsWe calculated yearly average values of C. rubrum biometric parameters, as well as estimated total weight, carbon flux, and carbon fixation in the structures of C. rubrum's colonies.ResultsIn both study areas, the values of the selected morphometric parameters for C. rubrum decreased until the 1990s, then increased from the 2000s, with average values surpassing the levels of the 1960s (Ligurian Sea) or reaching levels slightly lower than those of the 1980s (Catalan Sea). The difference in carbon sequestered between the oldest (1960s: Ligurian Sea; 1970s: Catalan Sea) and the lowest (1990s) biomass value of colonies is nearly double.LimitationsQuantitative data previous to the 1990s are very limited. Information on recent recovery trends in C. rubrum parameters is concentrated in a few areas and biased towards colonies in marine protected areas, with scarce quantitative information from colonies in other areas.ConclusionsThe halt in the C. rubrum decreasing trend coincided with the exhaustion of tree-like colonies and the first recovery response due to effective protection measures in some areas. Nevertheless, C. rubrum climate change mitigation capacity through carbon sequestration can be drastically reduced from its potential in only a few decades.

Profiles of alkenone concentration, the abundance of the calcified alkenone-producing species Emiliania huxleyi and Gephyrocapsa oceanica as well as nutrient and phytoplankton pigment concentrations were measured through the euphotic zone in surface waters of the Gulf of California during cruises in two different summers (2004, 2005) and one winter (2005). As determined using a biomarker and pigment inventory approach, E. huxleyi and G. oceanica, always the most abundant coccolithophore species at all sampling sites and seasons, represented only a minor fraction of total haptophytes which themselves constituted only a minor fraction of the total phytoplankton community. In winter, alkenone concentration was highest at the surface and displayed relatively uniform values with depth throughout the nutrient-replete euphotic zone. In summer, it display a subsurface peak in nitrate-depleted waters situated just above the nitracline and the deep chlorophyll maximum layer (DCML), a feature found to be well-developed at most sites. Maximum biomarker abundance was comparable in the two seasons, although the putative alkenone-producing coccolithophore species were more abundant in winter than in summer. Estimates of cellular alkenone content for the combined abundance of E. huxleyi and G. oceanica at each sampling depth showed that cells residing in the nitrate-depleted upper euphotic zone in summer were typically more enriched than those residing in nutrient-replete waters found deeper in the euphotic zone or throughout the euphotic zone in winter. The former estimates were very similar to values documented in laboratory cultures of E. huxleyi harvested in a nutrient-depleted stationary growth phase and the latter to those harvested in an exponential growth phase, under the influence of incipient light limitation. Overall, our findings imply that calcifying forms of E. huxleyi and G. oceanica can account for the measured alkenone concentration at all sites and sampling times. Although the life history of these organisms is known to include non-calcifying stages, it is unnecessary to invoke such an explanation as the cause for the elevated alkenone content of cells from nutrient-depleted surface waters in summer.

A natural pH gradient caused by marine CO2 seeps off Vulcano Island (Italy) was used to assess the effects of ocean acidification on coccolithophores, which are abundant planktonic unicellular calcifiers. Such seeps are used as natural laboratories to study the effects of ocean acidification on marine ecosystems, since they cause long-term changes in seawater carbonate chemistry and pH, exposing the organisms to elevated CO2 concentrations and therefore mimicking future scenarios. Previous work at CO2 seeps has focused exclusively on benthic organisms. Here we show progressive depletion of 27 coccolithophore species, in terms of cell concentrations and diversity, along a calcite saturation gradient from Omega(calcite) 6.4 to

Six moorings were deployed at different locations in the deep submarine canyons along the south–west margin of Crete, providing a total of eight sediment-trap time series from June 2005 to May 2006. Within this dataset, we analyzed the record from intact coccospheres, which represent the signal of export production from the coccolithophore community. The most abundant species at all stations during the whole investigated period were E. huxleyi and A. robusta, followed by S. pulchra HET, G. flabellatus, H. carteri, F. profunda, S. pulchra HOL oblonga, while the rest of the species represented ≤ 1% of the assemblage. Overall the assemblage composition was comparable at all stations, with slight variations mostly related to the different preservation of coccosphere integrity at the different collection depths. The consistent pattern of seasonal variation in species distribution and total coccolithophore export allowed us to define the occurrence of three main periods: a) March to June, with high overall coccosphere flux (up to 4.3 × 105–3.4 × 106 coccospheres m− 2 day− 1), increased abundance of E. huxleyi and subordinate H. carteri s.s., Umbilicosphaera spp. and S. pulchra; b) June to November, with high but gradually decreasing total coccosphere flux (up to 7 × 105–1.4 × 106 coccospheres m− 2 day− 1) and high relative abundance of the deep photic zone species A. robusta, F. profunda, G. flabellatus as well as S. pulchra and Coronosphaera spp., R. clavigera, U. tenuis, D. tubifera and holococcolithophores; c) November to February, with low overall export fluxes (3.5–9 × 104 coccospheres m− 2 day− 1) and high relative abundance of A. robusta, S. pulchra and Syracosphaera spp. These three periods correspond to the seasonal changes in sea surface temperature, surface mixed layer depth and rainfall and are associated with varying total surface primary production, as detected through remote sensing in the surface waters.

The distribution of coccolithophorid assemblages is analyzed from water samples collected in the photic zone of the middle Ionian Sea during a cruise of R/V Urania in November-December 1997. Coccolithophorids are an important phytoplankton group in the oligotrophic eastern Mediterranean, and their coccoliths make an important contribution to the sediments of this area, being also widely used for paleoclimatic and paleoceanographic reconstructions. Nevertheless, studies on extant coccolithophorids ecology and distribution in the eastern Mediterranean are limited and mostly related to surface waters: this study, even if restricted to a single period of the year, provides the first detailed analysis of species distribution throughout the photic zone, with relation to the main local physicochemical parameters. During the investigated period, the area is characterized by the presence of a surface mixed layer, reaching a depth of 25 to 90 m. Below this layer, a marked thermo- and halocline is developed. Coccolithophorids are the dominant phytoplankton group in the investigated samples and reach concentrations up to 2 x 10(4) coccospheres per liter of seawater. The species assemblage is that typical of the subtropical latitude, with a general high species diversity and a well-defined depth distribution. It is in fact possible to recognize an upper photic zone assemblage, dominated by E. huxleyi and characterized by higher concentration and species diversity and a lower photic zone where typically deep-living species (i.e., F. profunda, G. flabellatus) are present. These two zones are separated by a transition layer, where species of both zones are represented and new ones appear. Such vertical distribution appears to be strictly related to the local hydrology, with the zone boundaries rising and falling as a function of the location of the isotherms. In particular the first significant occurrence of F. profunda from surface to the deep photic zone corresponds with the start of the thermocline. Comparison of present plankton data with the surface sediment record, although displaying a consistent pattern of species assemblage, shows some differences in the presence and relative abundance of some species (G. oceanica): this can be related to seasonal as well as interannual variations in the pattern and intensity of surface circulation in the investigated area.