Transport of blue crab larvae in the Middle Atlantic Bight: A wet and windy journey

This paper describes the 25-year evolution of a program of research into the larval ecology of the Atlantic blue crab (Callinectes sapidus) near the mouth of Delaware Bay on the east coast of the USA (38.5N, 75.1W). The investigation began as a biological study; eventually incorporated a physical component; and finally added a mathematical modeling aspect. Early work was strictly biological and demonstrated that C. sapidus larvae are exported from the estuary to the adjacent coastal ocean where larval development occurs. Once this fact was established, it was clear that further progress demanded an understanding of shelf circulation. The consequent program of integrated biological and physical sampling was unique for its era and demonstrated a physical mechanism for retention of larvae on the inner shelf. Subsequent work explained the transport of larvae across-shelf and back to the estuary where benthic nursery habitat is located. This phase of the project was codified in a conceptual model that provided plausible mechanisms for these transport processes. The past dozen years have incorporated a more sophisticated biological approach where the temporal and spatial scales of sampling are better matched to the relevant physical processes. These improvements have allowed the quantification of larval-patch dynamics and the discovery of coastal null zones where larvae are retained near the natal estuary. The most recent phase of the project includes the continued development of mathematical models from simple empirical formulations to coupled hydrodynamic/tracking models that more accurately simulate the relevant physical and biological processes. This work has yielded a set of conceptual and physical models for larval transport that are among the most highly developed for any species of fish or invertebrate

Modeling estuarine ingress of blue crab megalopae: Effects of temporal patterns in larval release

The Atlantic blue crab Callinectes sapidus is an important predator in estuarine ecosystems and supports a large commercial fishery throughout its range. Settlement of blue crab megalopae in juvenile nurseries is episodic and is controlled by the combined effect of buoyancy- and wind-driven transport processes. Modeling studies have succeeded in hind-casting the temporal pattern of megalopal settlement but not the magnitude of individual settlement events. This shortcoming has been attributed to the lack of information concerning larval release by the adult spawning population. In this paper we present results of a set of field and modeling studies designed to test the hypothesis that temporal variation in release of larvae controls the size of settlement events. Field work consisted of collections of ovigerous female blue crabs during their spawning migration in Delaware Bay (∼38.5N; 75.1W). Egg samples were taken from each female, and the predicted date of hatching was determined using a morphological index developed as part of the study. Spectral analysis of the time series of daily larval-release events showed maximum density at low-frequency (period ≈ 40-70 days) and reflected the expected seasonality in spawning activity. There was only modest variance at higher frequencies (period ≈ 3–5 days), and the low-frequency harmonic was responsible for ∼33% of the overall variability. A series of modeling experiments was performed for the years 2002-2005. These experiments compared the observed larval release pattern in 2005, a constant release pattern, and a number of synthetic time series that incorporated the measured high- and low-frequency variations obtained from the observations. Results of these experiments showed that temporal variation in larval release can have measurable effects on the magnitude of individual settlement events. The effects on total annual settlement of high- and low-frequency variations are comparable (5–26% coefficient of variation) for any given year; however, these effects are relatively small when compared to physically-driven interannual variation in simulated settlement (81% coefficient of variation)

Transport and retention of the mitten crab (Eriocheir sinensis) in a Mid-Atlantic estuary: Predictions from a larval transport model

Invasive species cause extensive ecological damage in freshwater and marine habitats and are a threat to biodiversity in aquatic ecosystems world-wide. One such species, the Chinese mitten crab, Eriocheir sinensis, has invasive populations in northern Europe and San Francisco Bay, and there are confirmed reports of breeding female crabs in both the Chesapeake and Delaware Bays. Despite their threat to these ecosystems, there are still large gaps in the current understanding of this species\u27 larval biology that are critical to predicting the potential for large populations to establish in East Coast bays and estuaries. We addressed these issues by using a physical circulation model of Delaware Bay and the adjacent coastal ocean coupled to a modified particle advection scheme. We used this model to examine the effects of different physical mechanisms and larval behavior on transport, retention, and settlement of larvae in the bay. The circulation model produced flow fields using observed winds and river discharge for 2006 as well as systematic variations of river discharge and wind direction. Since little is known regarding mitten crab larval behavior, the larval component was purposefully general and incorporated a suite of behaviors such as tidal, diel, and ontogenetic vertical migration; however, results of this study showed that vertical migration affects the magnitude, but not locations of larval settlement. Simulations revealed that changes in the time and location of spawning can result in large variations in retention and settlement of larvae in Delaware Bay and the coastal ocean, due to seasonal variations of the physical flow field. Overall results of our study showed that the estuarine and coastal circulation typically found along the Middle Atlantic coast of the United States can result in significant retention of new and established E. sinensis populations in large estuaries as well as transport of larvae to new coastal locations

Search for CP violation in D+→ϕπ+ and D+s→K0Sπ+ decays

A search for CP violation in D + → ϕπ + decays is performed using data collected in 2011 by the LHCb experiment corresponding to an integrated luminosity of 1.0 fb−1 at a centre of mass energy of 7 TeV. The CP -violating asymmetry is measured to be (−0.04 ± 0.14 ± 0.14)% for candidates with K − K + mass within 20 MeV/c 2 of the ϕ meson mass. A search for a CP -violating asymmetry that varies across the ϕ mass region of the D + → K − K + π + Dalitz plot is also performed, and no evidence for CP violation is found. In addition, the CP asymmetry in the D+s→K0Sπ+ decay is measured to be (0.61 ± 0.83 ± 0.14)%

Differential branching fraction and angular analysis of the decay B0→K∗0μ+μ−

The angular distribution and differential branching fraction of the decay B 0→ K ∗0 μ + μ − are studied using a data sample, collected by the LHCb experiment in pp collisions at s√=7 TeV, corresponding to an integrated luminosity of 1.0 fb−1. Several angular observables are measured in bins of the dimuon invariant mass squared, q 2. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q20=4.9±0.9GeV2/c4 , where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions

Model-independent search for CP violation in D0→K−K+π−π+ and D0→π−π+π+π− decays

A search for CP violation in the phase-space structures of D0 and View the MathML source decays to the final states K−K+π−π+ and π−π+π+π− is presented. The search is carried out with a data set corresponding to an integrated luminosity of 1.0 fb−1 collected in 2011 by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. For the K−K+π−π+ final state, the four-body phase space is divided into 32 bins, each bin with approximately 1800 decays. The p-value under the hypothesis of no CP violation is 9.1%, and in no bin is a CP asymmetry greater than 6.5% observed. The phase space of the π−π+π+π− final state is partitioned into 128 bins, each bin with approximately 2500 decays. The p-value under the hypothesis of no CP violation is 41%, and in no bin is a CP asymmetry greater than 5.5% observed. All results are consistent with the hypothesis of no CP violation at the current sensitivity

Search for the lepton-flavor-violating decays Bs0→e±μ∓ and B0→e±μ∓

A search for the lepton-flavor-violating decays Bs0→e±μ∓ and B0→e±μ∓ is performed with a data sample, corresponding to an integrated luminosity of 1.0  fb-1 of pp collisions at √s=7  TeV, collected by the LHCb experiment. The observed number of Bs0→e±μ∓ and B0→e±μ∓ candidates is consistent with background expectations. Upper limits on the branching fractions of both decays are determined to be B(Bs0→e±μ∓)101  TeV/c2 and MLQ(B0→e±μ∓)>126  TeV/c2 at 95% C.L., and are a factor of 2 higher than the previous bounds

Search for the decay Bs0→D*∓π±

A search for the decay Bs0→D*∓π± is presented using a data sample corresponding to an integrated luminosity of 1.0  fb-1 of pp collisions collected by LHCb. This decay is expected to be mediated by a W-exchange diagram, with little contribution from rescattering processes, and therefore a measurement of the branching fraction will help us to understand the mechanism behind related decays such as Bs0→π+π- and Bs0→DD- . Systematic uncertainties are minimized by using B0→D*∓π± as a normalization channel. We find no evidence for a signal, and set an upper limit on the branching fraction of B(Bs0→D*∓π±)<6.1(7.8)×10-6 at 90% (95%) confidence level

Observation of the decay Bc→J/ψK+K−π+B_c \rightarrow J/\psi K^+ K^- \pi^+

The decay $B_c\rightarrow J/\psi K^+ K^- \pi^+$ is observed for the first time, using proton-proton collisions collected with the LHCb detector corresponding to an integrated luminosity of 3fb$^{-1}$. A signal yield of $78\pm14$ decays is reported with a significance of 6.2 standard deviations. The ratio of the branching fraction of \B_c \rightarrow J/\psi K^+ K^- \pi^+ decays to that of $B_c \rightarrow J/\psi \pi^+$ decays is measured to be $0.53\pm 0.10\pm0.05$, where the first uncertainty is statistical and the second is systematic.Comment: 18 pages, 2 figure