Dynamics of a tropical deepwater seagrass community during a major dredging campaign

A research and monitoring program was established to examine the potential impacts of a large scale capital dredging program on a tropical deepwater seagrass community between December 2005 and June 2008. The aims of the monitoring program were to fill gaps in our understanding of the dynamics of tropical deepwater seagrass habitats, their roles in fisheries productivity and their resilience and capacity for recovery from disturbance associated with dredging. While the dynamics of shallow coastal seagrasses in the region have been the subject of many studies little was previously known about the low density deepwater seagrass habitat that typified the study area. Results of the study revealed that these deepwater meadows had a high natural seasonal and inter-annual variability. Seasonality was substantially different to neighbouring shallow seagrass communities with a winter peak in abundance declining in spring before losing all above-ground biomass during summer months. Turbidity associated with dredging inhibited seagrass recruitment but there was evidence of seagrass recovery 12 months after the completion of dredging activity. Implications of the study for managing impacts to deepwater seagrass communities and differences in response to shallow coastal seagrasses are discussed

Implementing community based seagrass monitoring in the Wellesley Island Group

A survey was commissioned in 2007 by the Carpentaria Land Council Aboriginal Corporation (CLCAC) and the North Australia Indigenous Land and Sea Management Alliance (NAILSMA) on behalf of the Traditional Owners of the Wellesley Island region who had raised concerns over unhealthy dugong and turtle reported from hunters. Traditional Owners felt that one possible cause of sick animals may have been as a result of seagrass dieback causing a shortage of food to the animals. To answer the concerns of the Traditional Owners, the Department of Primary Industries and Fisheries Marine Ecology Group was commissioned to survey the seagrass communities of the Wellesley Islands and to train Wellesley Islands Rangers on seagrass mapping techniques. This was the first time that seagrasses have been formally surveyed and mapped for 23 years in the Wellesley Islands. Seagrass communities were the dominant benthic habitat in intertidal and shallow subtidal areas with a high diversity (8 specie s) of coastal seagrass compared with other Gulf of Carpentaria locations. Evidence of heavy dugong feeding activity was observed on most intertidal seagrass meadows surveyed. The highest density of dugong feeding trails was observed in seagrass meadows dominated by Halodule uninervis (narrow leaf form) and/or Halophila ovalis. In addition, dugongs were regularly observed feeding in subtidal meadows from the helicopter during surveys. This survey was used to help fill gaps in knowledge and provide a baseline from which future monitoring could be conducted to identify research required to answer the uncertainties raised by the Traditional Owners, and to help with developing zoning plans for the management of their Sea Country

Implementing community based seagrass monitoring in the Wellesley Island Group

A survey was commissioned in 2007 by the Carpentaria Land Council Aboriginal Corporation (CLCAC) and the North Australia Indigenous Land and Sea Management Alliance (NAILSMA) on behalf of the Traditional Owners of the Wellesley Island region who had raised concerns over unhealthy dugong and turtle reported from hunters. Traditional Owners felt that one possible cause of sick animals may have been as a result of seagrass dieback causing a shortage of food to the animals. To answer the concerns of the Traditional Owners, the Department of Primary Industries and Fisheries Marine Ecology Group was commissioned to survey the seagrass communities of the Wellesley Islands and to train Wellesley Islands Rangers on seagrass mapping techniques. This was the first time that seagrasses have been formally surveyed and mapped for 23 years in the Wellesley Islands. Seagrass communities were the dominant benthic habitat in intertidal and shallow subtidal areas with a high diversity (8 specie s) of coastal seagrass compared with other Gulf of Carpentaria locations. Evidence of heavy dugong feeding activity was observed on most intertidal seagrass meadows surveyed. The highest density of dugong feeding trails was observed in seagrass meadows dominated by Halodule uninervis (narrow leaf form) and/or Halophila ovalis. In addition, dugongs were regularly observed feeding in subtidal meadows from the helicopter during surveys. This survey was used to help fill gaps in knowledge and provide a baseline from which future monitoring could be conducted to identify research required to answer the uncertainties raised by the Traditional Owners, and to help with developing zoning plans for the management of their Sea Country

Dynamics of a tropical deepwater seagrass community during a major dredging campaign

A research and monitoring program was established to examine the potential impacts of a large scale capital dredging program on a tropical deepwater seagrass community between December 2005 and June 2008. The aims of the monitoring program were to fill gaps in our understanding of the dynamics of tropical deepwater seagrass habitats, their roles in fisheries productivity and their resilience and capacity for recovery from disturbance associated with dredging. While the dynamics of shallow coastal seagrasses in the region have been the subject of many studies little was previously known about the low density deepwater seagrass habitat that typified the study area. Results of the study revealed that these deepwater meadows had a high natural seasonal and inter-annual variability. Seasonality was substantially different to neighbouring shallow seagrass communities with a winter peak in abundance declining in spring before losing all above-ground biomass during summer months. Turbidity associated with dredging inhibited seagrass recruitment but there was evidence of seagrass recovery 12 months after the completion of dredging activity. Implications of the study for managing impacts to deepwater seagrass communities and differences in response to shallow coastal seagrasses are discussed

Inclusive-photon production and its dependence on photon isolation in pp collisions at s√ = 13 TeV using 139 fb−1 of ATLAS data

Measurements of differential cross sections are presented for inclusive isolated-photon production in pp collisions at a centre-of-mass energy of 13 TeV provided by the LHC and using 139 fb−1 of data recorded by the ATLAS experiment. The cross sections are measured as functions of the photon transverse energy in different regions of photon pseudorapidity. The photons are required to be isolated by means of a fixed-cone method with two different cone radii. The dependence of the inclusive-photon production on the photon isolation is investigated by measuring the fiducial cross sections as functions of the isolation-cone radius and the ratios of the differential cross sections with different radii in different regions of photon pseudorapidity. The results presented in this paper constitute an improvement with respect to those published by ATLAS earlier: the measurements are provided for different isolation radii and with a more granular segmentation in photon pseudorapidity that can be exploited in improving the determination of the proton parton distribution functions. These improvements provide a more in-depth test of the theoretical predictions. Next-to-leading-order QCD predictions from JETPHOX and SHERPA and next-to-next-to-leading-order QCD predictions from NNLOJET are compared to the measurements, using several parameterisations of the proton parton distribution functions. The measured cross sections are well described by the fixed-order QCD predictions within the experimental and theoretical uncertainties in most of the investigated phase-space region

Measurements of Zγ+jets differential cross sections in pp collisions at s√ = 13 TeV with the ATLAS detector

Differential cross-section measurements of Zγ production in association with hadronic jets are presented, using the full 139 fb−1 dataset of s√ = 13 TeV proton–proton collisions collected by the ATLAS detector during Run 2 of the LHC. Distributions are measured using events in which the Z boson decays leptonically and the photon is usually radiated from an initial-state quark. Measurements are made in both one and two observables, including those sensitive to the hard scattering in the event and others which probe additional soft and collinear radiation. Different Standard Model predictions, from both parton-shower Monte Carlo simulation and fixed-order QCD calculations, are compared with the measurements. In general, good agreement is observed between data and predictions from MATRIX and MiNNLOPS, as well as next-to-leading-order predictions from MADGRAPH5_AMC@NLO and SHERPA

Evidence for the charge asymmetry in pp → tt¯ production at s√ = 13 TeV with the ATLAS detector

Inclusive and differential measurements of the top–antitop (tt¯) charge asymmetry Att¯C and the leptonic asymmetry Aℓℓ¯C are presented in proton–proton collisions at s√ = 13 TeV recorded by the ATLAS experiment at the CERN Large Hadron Collider. The measurement uses the complete Run 2 dataset, corresponding to an integrated luminosity of 139 fb−1, combines data in the single-lepton and dilepton channels, and employs reconstruction techniques adapted to both the resolved and boosted topologies. A Bayesian unfolding procedure is performed to correct for detector resolution and acceptance effects. The combined inclusive tt¯ charge asymmetry is measured to be Att¯C = 0.0068 ± 0.0015, which differs from zero by 4.7 standard deviations. Differential measurements are performed as a function of the invariant mass, transverse momentum and longitudinal boost of the tt¯ system. Both the inclusive and differential measurements are found to be compatible with the Standard Model predictions, at next-to-next-to-leading order in quantum chromodynamics perturbation theory with next-to-leading-order electroweak corrections. The measurements are interpreted in the framework of the Standard Model effective field theory, placing competitive bounds on several Wilson coefficients

Search for non-resonant production of semi-visible jets using Run 2 data in ATLAS

Semi-visible jets, with a significant contribution to the event's missing transverse momentum, can arise in strongly interacting dark sectors. This results in an event topology where one of the jets can be aligned with the direction of the missing transverse momentum. The first search for semi-visible jets produced via a t-channel mediator exchange is presented. The analysis uses proton-proton collisions with an integrated luminosity of 139 fb−1 and a centre-of-mass energy of 13 TeV, collected with the ATLAS detector during the Run 2 of the LHC. No excess over Standard Model predictions is observed. Assuming a coupling strength of unity between the mediator, a Standard Model quark and a dark quark, mediator masses up to 2.7 TeV are excluded at the 95% confidence level. Upper limits on the coupling strength are also derived

Search for the Zγ decay mode of new high-mass resonances in pp collisions at √s = 13 TeV with the ATLAS detector

This letter presents a search for narrow, high-mass resonances in the Zγ final state with the Z boson decaying into a pair of electrons or muons. The √s = 13 TeV pp collision data were recorded by the ATLAS detector at the CERN Large Hadron Collider and have an integrated luminosity of 140 fb−1. The data are found to be in agreement with the Standard Model background expectation. Upper limits are set on the resonance production cross section times the decay branching ratio into Zγ. For spin-0 resonances produced via gluon–gluon fusion, the observed limits at 95% confidence level vary between 65.5 fb and 0.6 fb, while for spin-2 resonances produced via gluon–gluon fusion (or quark–antiquark initial states) limits vary between 77.4 (76.1) fb and 0.6 (0.5) fb, for the mass range from 220 GeV to 3400 GeV

Observation of Wγγ triboson production in proton-proton collisions at √s = 13 TeV with the ATLAS detector

This letter reports the observation of W(ℓν)γγ production in proton-proton collisions. This measurement uses the full Run 2 sample of events recorded at a center-of-mass energy of √s = 13 TeV by the ATLAS detector at the LHC, corresponding to an integrated luminosity of 140 fb−1. Events with a leptonically-decaying W boson and at least two photons are considered. The background-only hypothesis is rejected with an observed and expected significance of 5.6 standard deviations. The inclusive fiducial production cross section of W(eν)γγ and W(μν)γγ events is measured to be σfid=13.8±1.1(stat)+2.1−2.0(syst)±0.1(lumi) fb, in agreement with the Standard Model prediction