Anomalies in the carbonate system of Red Sea coastal habitats

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Baldry, K., Saderne, V., McCorkle, D. C., Churchill, J. H., Agust, S., & Duarte, C. M. Anomalies in the carbonate system of Red Sea coastal habitats. Biogeosciences, 17(2), (2020): 423-439, doi:10.5194/bg-17-423-2020.We use observations of dissolved inorganic carbon (DIC) and total alkalinity (TA) to assess the impact of ecosystem metabolic processes on coastal waters of the eastern Red Sea. A simple, single-end-member mixing model is used to account for the influence of mixing with offshore waters and evaporation–precipitation and to model ecosystem-driven perturbations on the carbonate system chemistry of coral reefs, seagrass meadows and mangrove forests. We find that (1) along-shelf changes in TA and DIC exhibit strong linear relationships that are consistent with basin-scale net calcium carbonate precipitation; (2) ecosystem-driven changes in TA and DIC are larger than offshore variations in >70 % of sampled seagrass meadows and mangrove forests, changes which are influenced by a combination of longer water residence times and community metabolic rates; and (3) the sampled mangrove forests show strong and consistent contributions from both organic respiration and other sedimentary processes (carbonate dissolution and secondary redox processes), while seagrass meadows display more variability in the relative contributions of photosynthesis and other sedimentary processes (carbonate precipitation and oxidative processes). The results of this study highlight the importance of resolving the influences of water residence times, mixing and upstream habitats on mediating the carbonate system and coastal air–sea carbon dioxide fluxes over coastal habitats in the Red Sea.This research has been supported by the King Abdullah University of Science and Technology (KAUST) (grant nos. BAS/1/1071-01-01 and BAS/1/1072-01-01) and the Investment in Science fund at WHOI

Annual plankton community metabolism in estuarine and coastal waters in Perth (Western Australia)

The planktonic metabolic balance that is the balance between gross primary production (GPP) and community respiration (CR) was determined in Matilda Bay (estuarine) and Woodman Point (coastal) in Perth, Western Australia. The rates of net community production (NCP = GPP – CR) and the ratio between GPP and CR (P/R) were assessed to evaluate whether the metabolic balance in the two coastal locations tends to be net autotrophic (production exceeding community respiration) or net heterotrophic (respiration exceeding production). We also analyzed environmental variability by measuring temperature, salinity, and nutrients and chlorophyll a concentration. Samples were collected biweekly from March 2014 to March 2015. During the study period the metabolic rates were three times higher in Matilda Bay than in Woodman Point. The predominant metabolism was net autotrophic at both sites with P/R ratios >1 in the majority of the sampling dates. In Matilda Bay, the metabolic rates were negatively correlated with salinity denoting river dynamics influence, and positively with chlorophyll a. In Woodman Point only the GPP was positively correlated with chlorophyll a. The positive correlation between P/R ratio and GPP in Matilda Bay and the positive correlations between the metabolic rates and chlorophyll a suggest that factors controlling autotrophic processes are modulating the planktonic metabolic balance in the coastal marine ecosystem in Perth. Significant correlations were found between CR and GPP-standardized to chlorophyll a and water temperature. The net autotrophic metabolic balance indicates that in both ecosystems planktonic communities are acting as a sink of CO2 and as a source of organic matter and oxygen to the system and are able to export organic matter to other ecosystems

Projected Changes in Photosynthetic Picoplankton in a Warmer Subtropical Ocean

The oligotrophic subtropical gyres are the largest biome on Earth, where picoplankton constitute the dominant autotrophs. The trend for autotrophic picoplankton to increase with sea temperature has led to predictions that picophytoplankton abundance will increase with warming. Here we conducted a global survey in the open subtropical-tropical ocean to resolve the functional relationships between picophytoplankton abundance and oceanic properties (water temperature, chlorophyll a concentration, nutrient concentrations, and underwater visible and ultraviolet B radiation). We then used these relationships to build models projecting the future changes of Synechococcus, Prochlorococcus, and eukaryotic picoautotrophs populations in the subtropical gyres with warming. Our goal is to refine the forecasts for this large biome and implement the analysis by including the picoeukaryotes, absent in previous models, but a relevant component of picophytoplankton. The data obtained and the relationships found in our global survey of the subtropical-tropical ocean between picophytoplankton abundance and ocean properties differed from previous global studies including colder (temperate, subpolar, and polar) and coastal waters. These differences included a lower abundance of Synechococcus populations, significant negative relationships between Prochlorococcus abundance and nutrient concentrations, and positive relationships for picoeukaryotes and no relationship for Synechococcus abundance, and, a moderate response to temperature in the warm waters of the tropical-subtropical open ocean. A model based on temperature increase alone forecasts a general increase in picoautotrophs by year 2100, although minimal for picoeukaryotes, and much more moderate for Synechococcus than previously forecasted. However, a global change model linking the thermal increase with the associated decline in chlorophyll a, and increased underwater solar radiation penetration, projected a decline in the abundance of autotrophic picoplankton. The decline was larger at the surface layer and partially compensated by the increased importance of deep picophytoplankton blooms, especially those of Prochlorococcus. The global change model predicted an increased dominance of Prochlorococcus sp. in the subtropical-tropical ocean with future warming. Our results, based on current patterns of picophytoplankton distribution, help improve existing projections by considering feedbacks affecting picophytoplankton abundance in the future subtropical and tropical ocean, the larger biome on Earth

Survey, identification, and characterization of Cylindrocarpon-like asexual morphs in Spanish forest nurseries

[EN] Cylindrocarpon-like asexual morphs infect herbaceous and woody plants, mainly in agricultural scenarios, but also in forestry systems. The aim of the present study was to characterize a collection of Cylindrocarpon-like isolates recovered from the roots of a broad range of forest hosts from nurseries showing decline by morphological and molecular studies. Between 2009 and 2012, 17 forest nurseries in Spain were surveyed and a total of 103 Cylindrocarpon-like isolates were obtained. Isolates were identified based on DNA sequences of the partial gene regions histone H3 (his3). For the new species, the internal transcribed spacer and intervening 5.8S nrRNA gene (ITS) region, beta-tubulin (tub2), and translation elongation factor 1-alpha (tefl) were also used to determine their phylogenetic position. Twelve species belonging to the genera Cylindrodendrum, Dactylonectria, and Ilyonectria were identified from damaged roots of 15 different host genera. The species C. alicantinum, D. macrodidyma, D. novozelandica, D. pauciseptata, D. pinicola, D. torresensis, I. capensis, I. cyclaminicola, I. liriodendri, I. pseudodestructans, I. robusta, and I. rufa were identified. In addition, two Dactylonectria species (D. hispanica sp. nov. and D. valentina sp. nov.), one Ilyonectria species (I. ilicicola sp. nov.), and one Neonectria species (N. quercicola sp. nov.) are newly described. The present study demonstrates the prevalence of this fungal group associated with seedlings of diverse hosts showing decline symptoms in forest nurseries in Spain.This research was supported by funding from the Spanish project AGL2011-30438-C02-01 (Ministerio de Economia y Competitividad, Spain). It was also funded by Portuguese national funds through Fundacao para a Ciencia e a Tecnologia grant SFRH/BPD/84508/2012 for Ana Cabral and FCT Unit funding UID/AGR/04129/2013). C. Agusti-Brisach is the holder of a 'Juan de la Cierva-Formacion' fellowship from MINECO (Spain).Mora-Sala, B.; Cabral, A.; León Santana, M.; Agusti Brisach, C.; Armengol Fortí, J.; Abad Campos, P. (2018). Survey, identification, and characterization of Cylindrocarpon-like asexual morphs in Spanish forest nurseries. Plant Disease. 102(11):2083-2100. https://doi.org/10.1094/PDIS-01-18-0171-RES208321001021

Metatranscriptomes reveal functional variation in diatom communities from the Antarctic Peninsula

Functional genomics of diatom-dominated communities from the Antarctic Peninsula was studied using comparative metatranscriptomics. Samples obtained from diatom-rich communities in the Bransfield Strait, the western Weddell Sea and sea ice in the Bellingshausen Sea/Wilkins Ice Shelf yielded more than 500K pyrosequencing reads that were combined to produce a global metatranscriptome assembly. Multi-gene phylogenies recovered three distinct communities, and diatom-assigned contigs further indicated little read-sharing between communities, validating an assembly-based annotation and analysis approach. Although functional analysis recovered a core of abundant shared annotations that were expressed across the three diatom communities, over 40% of annotations (but accounting for <10% of sequences) were community-specific. The two pelagic communities differed in their expression of N-metabolism and acquisition genes, which was almost absent in post-bloom conditions in the Weddell Sea community, while enrichment of transporters for ammonia and urea in Bransfield Strait diatoms suggests a physiological stance towards acquisition of reduced N-sources. The depletion of carbohydrate and energy metabolism pathways in sea ice relative to pelagic communities, together with increased light energy dissipation (via LHCSR proteins), photorespiration, and NO3 uptake and utilization all pointed to irradiance stress and/or inorganic carbon limitation within sea ice. Ice-binding proteins and cold-shock transcription factors were also enriched in sea ice diatoms. Surprisingly, the abundance of gene transcripts for the translational machinery tracked decreasing environmental temperature across only a 4 degrees C range, possibly reflecting constraints on translational efficiency and protein production in cold environments.Portuguese Science Foundation (FCT) [PTDC/MAR/72630]; Spanish Ministry of Economy and Competitiveness (under the scope of the International Polar Year (IPY)) [POL2006-00550/CTM]info:eu-repo/semantics/publishedVersio

DC voltage stability analysis and enhancement for grid-forming-based MTDC systems

This letter first identifies a new mode of lowfrequency harmonic instability when combining grid-forming control with the typical DC voltage droop control necessitated in multi-terminal high voltage direct-current transmissions. This mode does not exist when grid-following control is applied and its mechanism is explicitly revealed by the DC-side input admittance modeling of the converter. Then, a phase compensator plus a virtual power system stabilizer are introduced to pacify the input admittance within the critical frequency range and de-risk the related instability. Last, it is also demonstrated that the proposed control strategy achieves excellent performance in contingent active power imbalance ride-through in the DC system. All the analyses are verified by electro-magnetic-transient simulations with a modular multi-level converter model comprising 278 submodules per arm

Oxygen supersaturation protects coastal marine fauna from ocean warming

Ocean warming affects the life history and fitness of marine organisms by, among others, increasing animal metabolism and reducing oxygen availability. In coastal habitats, animals live in close association with photosynthetic organisms whose oxygen supply supports metabolic demands and may compensate for acute warming. Using a unique high-frequency monitoring dataset, we show that oxygen supersaturation resulting from photosynthesis closely parallels sea temperature rise during diel cycles in Red Sea coastal habitats. We experimentally demonstrate that oxygen supersaturation extends the survival to more extreme temperatures of six species from four phyla. We clarify the mechanistic basis of the extended thermal tolerance by showing that hyperoxia fulfills the increased metabolic demand at high temperatures. By modeling 1 year of water temperatures and oxygen concentrations, we predict that oxygen supersaturation from photosynthetic activity invariably fuels peak animal metabolic demand, representing an underestimated factor of resistance and resilience to ocean warming in ectotherms

Temperature dependence of plankton community metabolism in the subtropical and tropical oceans

Here we assess the temperature dependence of the metabolic rates (gross primary production (GPP), community respiration (CR), and the ratio GPP/CR) of oceanic plankton communities. We compile data from 133 stations of the Malaspina 2010 Expedition, distributed among the subtropical and tropical Atlantic, Pacific, and Indian oceans. We used the in vitro technique to measured metabolic rates during 24 h incubations at three different sampled depths: surface, 20%, and 1% of the photosynthetically active radiation measured at surface. We also measured the % of ultraviolet B radiation (UVB) penetrating at surface waters. GPP and CR rates increased with warming, albeit different responses were observed for each sampled depth. The overall GPP/CR ratio declined with warming. Higher activation energies (Ea) were derived for both processes (GPPChla = 0.97; CRChla = 1.26; CRHPA = 0.95 eV) compared to those previously reported. The Indian Ocean showed the highest Ea (GPPChla = 1.70; CRChla = 1.48; CRHPA = 0.57 eV), while the Atlantic Ocean showed the lowest (GPPChla = 0.86; CRChla = 0.77; CRHPA = 0.13 eV). We believe that the difference between previous assessments and the ones presented here can be explained by the overrepresentation of Atlantic communities in the previous data sets. We found that UVB radiation also affects the temperature dependence of surface GPP, which decreased rather than increased under high levels of UVB. Ocean warming, which causes stratification and oligotrophication of the subtropical and tropical oceans, may lead to reduced surface GPP as a result of increased penetration of UVB radiation.En prens

Rebuilding marine life

The UN Sustainable Development Goal 14 aims to “conserve and sustainably use the oceans, seas and marine resources for sustainable development”. Achieving this goal will require rebuilding the marine life-support systems that deliver the many benefits society receives from a healthy ocean. In this Review we document the recovery of marine populations, habitats and ecosystems following past conservation interventions. Recovery rates across studies suggest that substantial recovery of the abundance, structure, and function of marine life could be achieved by 2050, should major pressures, including climate change, be mitigated. Rebuilding marine life represents a doable Grand Challenge for humanity, and ethical obligation, and a smart economic objective to achieve a sustainable future