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The characteristics of a persistent gyre in the mouth of the Bay of Fundy are studied using model simulations. A set of climatological runs are conducted to evaluate the relative importance of the different forcing mechanisms affecting the gyre. The main mechanisms are tidal rectification, and density-driven circulation. Stronger circulation of the gyre occurs during the later part of the stratified season (July–August and September–October). The density-driven flow around the gyre is set-up by weak tidal mixing in the deep basin in the central Bay of Fundy and strong tidal mixing on the shallow flanks around Grand Manan Island and western Nova Scotia. Retention of particles in the Gyre is controlled by the residual tidal circulation, increased frontal retention during stratified periods, wind stress, and interactions with the adjacent circulation of the Gulf of Maine. Residence times longer than 30 days are predicted for particles released in the proximity of the gyre.

[1] The characteristics of the principal barotropic diurnal and semidiurnal tides are examined for the South Atlantic Bight (SAB) of the eastern United States coast. We combine recent observations from pressure gauges and ADCPs on fixed platforms and additional short-term deployments off the Georgia and South Carolina coasts together with National Ocean Service coastal tidal elevation harmonics. These data have shed light on the regional tidal propagation, particularly off the Georgia/South Carolina coast, which is perforated by a dense estuary/tidal inlet complex (ETIC). We have computed tidal solutions for the western North Atlantic Ocean on two model domains. One includes a first-order representation of the ETIC in the SAB, and the other does not include the ETIC. We find that the ETIC is highly dissipative and affects the regional energy balance of the semidiurnal tides. Nearshore, inner, and midshelf model skill at semidiurnal frequencies is sensitive to the inclusion of the ETIC. The numerical solution that includes the ETIC shows significantly improved skill compared to the solution that does not include the ETIC. For the M 2 constituent, the largest tidal frequency in the SAB, overall amplitude and phase error is reduced from 0.25 m to 0.03 m and 13.8°to 2.8°for coastal observation stations. Similar improvement is shown for midshelf stations. Diurnal tides are relatively unaffected by the ETIC.

A modified ensemble Kalman filter (KF) is proposed which can enhance performance for highly non‐linear prognostic models. The algorithm differs from the traditional ensemble KF by the addition of an expectation maximization step, which estimates the parameters of a Gaussian mixture model for the ensemble of forecast states. The algorithm is tested in twin experiments using a simple phytoplankton–zooplankton model.

Many microbial communities contain organized patterns of cell types, yet relatively little is known about the mechanism or function of this organization. In colonies of the budding yeast Saccharomyces cerevisiae, sporulation occurs in a highly organized pattern, with a top layer of sporulating cells sharply separated from an underlying layer of nonsporulating cells. A mutant screen identified the Mpk1 and Bck1 kinases of the cell-wall integrity (CWI) pathway as specifically required for sporulation in colonies. The CWI pathway was induced as colonies matured, and a target of this pathway, the Rlm1 transcription factor, was activated specifically in the nonsporulating cell layer, here termed feeder cells. Rlm1 stimulates permeabilization of feeder cells and promotes sporulation in an overlying cell layer through a cell-nonautonomous mechanism. The relative fraction of the colony apportioned to feeder cells depends on nutrient environment, potentially buffering sexual reproduction against suboptimal environments.KEYWORDS cell-wall integrity; cell permeability; cell-cell signaling; Saccharomyces cerevisiae; sporulation A S embryos develop, cells of different fates organize into patterns [reviewed in Kicheva et al. (2012) and Perrimon et al. (2012)] . Intriguingly, even unicellular microbial species form communities in which different cell types are organized into patterns [reviewed in Kaiser et al. (2010), Honigberg (2011, and Loomis (2014)]. For example, colonies of the budding yeast Saccharomyces cerevisiae form an upper layer of larger cells (U cells) overlying a layer of smaller cells (L cells). U and L cells differ in their metabolism, gene expression, and resistance to stress, and U and L layers are separated by a strikingly sharp boundary Vachova et al. 2013). Patterns are also observed in yeast biofilms, where cells closest to the plastic surface grow as ovoid cells, whereas cells further from the surface differentiate into hyphae for Candida species [reviewed in Finkel and Mitchell (2011)] or pseudohyphae and eventually asci for S. cerevisiae (White et al. 2011).Sporulation also occurs in patterns within yeast colonies. Specifically, a narrow horizontal layer of sporulated cells forms through the center of the colony early during colony development. As colonies continue to mature, this layer progressively expands upward to include the top of the colony; this wave is driven by progressive alkalization and activation of the Rim101 signaling pathway . In contrast, cells at the bottom of the colony, i.e., directly contacting the agar substrate, also sporulate at early stages of colony development, but this narrow cell layer does not expand as the colony matures . The same colony sporulation pattern is observed in a range of laboratory yeasts as well as in S. cerevisiae and S. paradoxus isolated from the wild. Indeed, in these wild yeasts, the same colony sporulation pattern forms on a range of fermentable and nonfermentable carbon sources .The mechanism of sporulation patterning and its function remai...