Dissolved inorganic nitrogen fluxes from common Florida Bay (U.S.A.) sponges

Sponge biomass represents the largest heterotrophic component of benthic biota in the Florida Bay ecosystem. These organisms can significantly alter the water quality of their surrounding environment through biogeochemical transformations of nutrient elements resulting from their dynamic pumping, water filtration, and respiration processes. Ammonium (NH4 +) and nitrate plus nitrite (NO3 − + NO2 −; NOx −) fluxes were obtained for 11 ecologically important species at three sites within Florida Bay, Florida (U.S.A.) utilizing chamber incubations on undisturbed individual sponges. Significant dissolved inorganic nitrogen (DIN) effluxes ranging between 9.0 ± 2.2 μmol N h−1 Lsponge −1 and 141 ± 26 μmol N h−1 Lsponge −1 were observed for eight of the 11 tested sponges; specifically, from six of eight tested high-microbial abundance (HMA) sponges, and from two of three tested low-microbial abundance (LMA) sponges. The abundant HMA species Chondrilla nucula showed the highest, volume-normalized rate of DIN release. These fluxes represent a continuation of the previously observed dichotomy in the chemical speciation of DIN in exhalent waters of LMA and HMA sponges, with NH4 + and NOx − dominating their respective exhalent jets. Surprisingly, we found that dissolved organic matter (DOM) appeared to make a negligible contribution to the total released N, but we hypothesize that the lack of DOM utilization or production was due to methodological limitations. Our flux data combined with sponge biomass estimates indicate that sponges, particularly HMA species, are a large, and potentially dominant, source of inorganic nitrogen to Florida Bay waters

Sponges represent a major source of inorganic nitrogen in Florida Bay (U.S.A.)

Florida Bay nutrient budgets have shown that the majority of existing and influent nitrogen (N) is in organic forms. Consequently, local remineralization processes have been found to regulate the supply of dissolved inorganic nitrogen (DIN). Sponges have dominated benthic animal biomass in Florida Bay and are known to influence local DIN concentrations through remineralization organic matter, yet the role of these organisms in local N budgets is largely unaddressed. We quantified the role of sponges in N cycling in Florida Bay during 2012–2013 by constructing an N budget for a sponge-rich basin. Surveys of sponge biomass conducted in Mystery Basin found sponges at 57 of the 59 assessed stations. Sponge population maxima reached 21 individuals m−2 and biomass contributions as high as 4.4 Lsponge m−2. We estimated an average areal DIN contribution from total sponge biomass of 0.59 ± 0.28 mmol N m−2 d−1. However, calculated fluxes from the 59 stations exhibited significant spatial variability associated with changes in the size and species composition of the sponge community; peak N fluxes reached 3.5 ± 0.9 mmol N m−2 d−1 in areas with large populations of high microbial abundance sponges. The average flux from the sponge community was the largest of the estimated sources of DIN to Mystery Basin, representing roughly half of the overall N sourcing. This N satisfied more than half of the demand by primary productivity. These results indicate that sponges are important sources of inorganic N to Florida Bay environments

Consumption of dissolved organic carbon by Caribbean reef sponges

Sponges are conspicuous and abundant within the benthic fauna on Caribbean reefs. The ability of these organisms to efficiently capture carbon from particulate sources is well known and the importance of dissolved organic carbon (DOC) uptake has been recognized for several species. We surveyed DOC ingestion by seven sponge species common to Florida Keys reefs using nondisruptive sampling methods on undisturbed individuals. Three of the seven species exhibited significant DOC removal ranging from 13% to 24% of ambient concentrations. The tested species that removed DOC host large microbial consortia within their tissues, while the converse was observed for those that did not. This divergent behavior may suggest an important role for sponge associated microbes in the utilization of DOC by these species. The feeding behaviors of individuals of Xestospongia muta were then monitored over time to investigate its respiratory consumption of particulate and DOC. The uptake rates of dissolved oxygen (DO) and organic carbon by two undisturbed individuals revealed that DOC represented 96% of removed C, and that the tested individuals removed approximately equal quantities of C and DO. This demonstrates that X. muta largely satisfies its respiration demands through DOC consumption, and that DOC likely represents the dominant C source for biomass production and cell overturn in this species. These results further illustrate the metabolic importance of DOC to sponges, and suggest that these organisms are an important pathway for remineralizing organic matter on Caribbean reefs

Oyster reefs as carbon sources and sinks

Carbon burial is increasingly valued as a service provided by threatened vegetated coastal habitats. Similarly, shellfish reefs contain significant pools of carbon and are globally endangered, yet considerable uncertainty remains regarding shellfish reefs’ role as sources (+) or sinks (-) of atmospheric CO2. While CO2 release is a by-product of carbonate shell production (then burial), shellfish also facilitate atmospheric-CO2 drawdown via filtration and rapid biodeposition of carbon-fixing primary producers. We provide a framework to account for the dual burial of inorganic and organic carbon, and demonstrate that decade-old experimental reefs on intertidal sandflats were net sources of CO2 (7.1 ± 1.2 MgC ha-1 yr-1 (m ± s.e.)) resulting from predominantly carbonate deposition, whereas shallow subtidal reefs (-1.0 ± 0.4 MgC ha-1 yr-1) and saltmarsh-fringing reefs (-1.3 ± 0.4 MgC ha-1 yr-1) were dominated by organic-carbon-rich sediments and functioned as net carbon sinks (on par with vegetated coastal habitats). These landscape-level differences reflect gradients in shellfish growth, survivorship and shell bioerosion. Notably, down-core carbon concentrations in 100- to 4000-year-old reefs mirrored experimental-reef data, suggesting our results are relevant over centennial to millennial scales, although we note that these natural reefs appeared to function as slight carbon sources (0.5 ± 0.3 MgC ha-1 yr-1). Globally, the historical mining of the top metre of shellfish reefs may have reintroduced more than 400 000 000 Mg of organic carbon into estuaries. Importantly, reef formation and destruction do not have reciprocal, counterbalancing impacts on atmospheric CO2 since excavated organic material may be remineralized while shell may experience continued preservation through reburial. Thus, protection of existing reefs could be considered as one component of climate mitigation programmes focused on the coastal zone

Coastal squeeze on temperate reefs: Long-term shifts in salinity, water quality, and oyster-associated communities

Foundation species, such as mangroves, saltmarshes, kelps, seagrasses, and oysters, thrive within suitable environmental envelopes as narrow ribbons along the land–sea margin. Therefore, these habitat-forming species and resident fauna are sensitive to modified environmental gradients. For oysters, many estuaries impacted by sea-level rise, channelization, and municipal infrastructure are experiencing saltwater intrusion and water-quality degradation that may alter reef distributions, functions, and services. To explore decadal-scale oyster–reef community patterns across a temperate estuary in response to environmental change, we resampled reefs in the Newport River Estuary (NRE) during 2013–2015 that had previously been studied during 1955–1956. We also coalesced historical NRE reef distribution (1880s–2015), salinity (1913–2015), and water-quality-driven shellfish closure boundary (1970s–2015) data to document environmental trends that could influence reef ecology and service delivery. Over the last 60–120 years, the entire NRE has shifted toward higher salinities. Consequently, oyster–reef communities have become less distinct across the estuary, manifest by 20%–27% lower species turnover and decreased faunal richness among NRE reefs in the 2010s relative to the 1950s. During the 2010s, NRE oyster–reef communities tended to cluster around a euhaline, intertidal-reef type more so than during the 1950s. This followed faunal expansions farther up estuary and biological degradation of subtidal reefs as NRE conditions became more marine and favorable for aggressive, reef-destroying taxa. In addition to these biological shifts, the area of suitable bottom on which subtidal reefs persist (contracting due to up-estuary intrusion of marine waters) and support human harvest (driven by water quality, eroding from up-estuary) has decreased by >75% since the natural history of NRE reefs was first explored. This “coastal squeeze” on harvestable subtidal oysters (reduced from a 4.5-km to a 0.75-km envelope along the NRE's main axis) will likely have consequences regarding the economic incentives for future oyster conservation, as well as the suite of services delivered by remaining shellfish reefs (e.g., biodiversity maintenance, seafood supply). More broadly, these findings exemplify how “squeeze” may be a pervasive concern for biogenic habitats along terrestrial or marine ecotones during an era of intense global change

Haslea silbo, a novel cosmopolitan species of blue diatoms

Specimens of a new species of blue diatoms from the genus Haslea Simonsen were discovered in geographically distant sampling sites, first in the Canary Archipelago, then North Carolina, Gulf of Naples, the Croatian South Adriatic Sea, and Turkish coast of the Eastern Mediterranean Sea. An exhaustive characterization of these specimens, using a combined morphological and genomic approach led to the conclusion that they belong to a single new to science cosmopolitan species, Haslea silbo sp. nov. A preliminary characterization of its blue pigment shows similarities to marennine produced by Haslea ostrearia, as evidenced by UV–visible spectrophotometry and Raman spectrome-try. Life cycle stages including auxosporulation were also observed, providing data on the cardinal points of this species. For the two most geographically distant populations (North Carolina and East Mediterranean), complete mitochondrial and plastid genomes were sequenced. The mitogenomes of both strains share a rare atp6 pseudogene, but the number, nature, and positions of the group II introns inside its cox1 gene differ between the two populations. There are also two pairs of genes fused in single ORFs. The plastid genomes are characterized by large regions of recombination with plasmid DNA, which are in both cases located between the ycf35 and psbA genes, but whose content differs between the strains. The two sequenced strains hosts three plasmids coding for putative serine recombinase protein whose sequences are compared, and four out of six of these plasmids were highly conserved

The performance of the jet trigger for the ATLAS detector during 2011 data taking

The performance of the jet trigger for the ATLAS detector at the LHC during the 2011 data taking period is described. During 2011 the LHC provided proton–proton collisions with a centre-of-mass energy of 7 TeV and heavy ion collisions with a 2.76 TeV per nucleon–nucleon collision energy. The ATLAS trigger is a three level system designed to reduce the rate of events from the 40 MHz nominal maximum bunch crossing rate to the approximate 400 Hz which can be written to offline storage. The ATLAS jet trigger is the primary means for the online selection of events containing jets. Events are accepted by the trigger if they contain one or more jets above some transverse energy threshold. During 2011 data taking the jet trigger was fully efficient for jets with transverse energy above 25 GeV for triggers seeded randomly at Level 1. For triggers which require a jet to be identified at each of the three trigger levels, full efficiency is reached for offline jets with transverse energy above 60 GeV. Jets reconstructed in the final trigger level and corresponding to offline jets with transverse energy greater than 60 GeV, are reconstructed with a resolution in transverse energy with respect to offline jets, of better than 4 % in the central region and better than 2.5 % in the forward direction

Measurement of the cross section for isolated-photon plus jet production in pp collisions at √s=13 TeV using the ATLAS detector

The dynamics of isolated-photon production in association with a jet in proton–proton collisions at a centre-of-mass energy of 13 TeV are studied with the ATLAS detector at the LHC using a dataset with an integrated luminosity of 3.2 fb−1. Photons are required to have transverse energies above 125 GeV. Jets are identified using the anti- algorithm with radius parameter and required to have transverse momenta above 100 GeV. Measurements of isolated-photon plus jet cross sections are presented as functions of the leading-photon transverse energy, the leading-jet transverse momentum, the azimuthal angular separation between the photon and the jet, the photon–jet invariant mass and the scattering angle in the photon–jet centre-of-mass system. Tree-level plus parton-shower predictions from Sherpa and Pythia as well as next-to-leading-order QCD predictions from Jetphox and Sherpa are compared to the measurements

Measurement of the View the tt production cross-section using eμ events with b-tagged jets in pp collisions at √s = 13 TeV with the ATLAS detector

This paper describes a measurement of the inclusive top quark pair production cross-section (σtt¯) with a data sample of 3.2 fb−1 of proton–proton collisions at a centre-of-mass energy of √s = 13 TeV, collected in 2015 by the ATLAS detector at the LHC. This measurement uses events with an opposite-charge electron–muon pair in the final state. Jets containing b-quarks are tagged using an algorithm based on track impact parameters and reconstructed secondary vertices. The numbers of events with exactly one and exactly two b-tagged jets are counted and used to determine simultaneously σtt¯ and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section is measured to be: σtt¯ = 818 ± 8 (stat) ± 27 (syst) ± 19 (lumi) ± 12 (beam) pb, where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the integrated luminosity and the LHC beam energy, giving a total relative uncertainty of 4.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. A fiducial measurement corresponding to the experimental acceptance of the leptons is also presented

A search for resonances decaying into a Higgs boson and a new particle X in the XH → qqbb final state with the ATLAS detector

A search for heavy resonances decaying into a Higgs boson (H) and a new particle (X) is reported, utilizing 36.1 fb−1 of proton–proton collision data at collected during 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. The particle X is assumed to decay to a pair of light quarks, and the fully hadronic final state is analysed. The search considers the regime of high XH resonance masses, where the X and H bosons are both highly Lorentz-boosted and are each reconstructed using a single jet with large radius parameter. A two-dimensional phase space of XH mass versus X mass is scanned for evidence of a signal, over a range of XH resonance mass values between 1 TeV and 4 TeV, and for X particles with masses from 50 GeV to 1000 GeV. All search results are consistent with the expectations for the background due to Standard Model processes, and 95% CL upper limits are set, as a function of XH and X masses, on the production cross-section of the resonance