A review of the causes, effects, and potential management of harmful brown tide blooms caused byAureococcus anophagefferens (Hargraves et sieburth)

Brown tides caused by the harmful algaAureococcus anophagefferens abruptly appeared in some coastal embayments of the northeastern United States (Rhode Island, New York) in 1985. Since then, brown tides have vanished from some bays, chronically reoccurred in others, and recently have exhibited an apparent southern expansion into new regions (e.g., New Jersey, Delaware, Maryland, and Virginia). Brown tides have also recently been detected across the Atlantic Ocean in South Africa. Although blooms ofA. anophagefferens have no known direct, negative effects on human health, they are considered harmful because of their detrimental effects on estuarine organisms, such as suspension feeders (scallops and hard clams) and submerged aquatic vegetation. The selective effect of blooms on pelagic grazers (zooplankton and shellfish) is likely to affect food webs and biodiversity within affected ecosystems. Recent findings indicate brown tides occur in shallow estuaries with long residence times and high salinities (> 25‰). These estuarine characteristics may foster the accumulation of algal biomass and a nutrient environment (high dissolved organic matter and low dissolved in organic nitrogen) as well as a low light regime that encourages rapid cellular growth ofA. anophagefferens. A lack of sufficient grazing control by benthic and pelagic suspension feeders during the initiation phase of blooms is also implicated in brown tide development.     

“Miss Remington” Goes to Work: Gender,Space, and Technology at the Dawn of the Information Age*

At the end of the 19th century, the financial services sector underwent a technological “revolution” with the invention of the typewriter, dictaphone, and hollerith machine. At the same time, the gender of labor within this sector was also changing, such that by the end of the first quarter of the 20th century, most of the work taking place in white‐collar offices was performed by women. After introducing the broader research project on which this is based, I consider how technology and social relations shaped one another at the level of the body, the workplace, and with broader networks of branch banking, focusing on early 20th‐century Montreal, Canada. I argue that the financial services sector worked to create a system in which men flowed through and women functioned as fixed points. I further argue that this pattern was echoed at different scales within the financial services industry, from the level of the body and the workplace up through spatially dispersed national‐level networks.     

Rotating flow over long shallow ridges

Abstract

The flow of a rotating homogeneous, incompressible fluid past a long ridge is investigated. An analysis is presented for flows in which E ? 1, Ro ～ E^½, H/D ～ E⁰, h/D ～ E^½ and cosα ～ E⁰ where E is the Ekman number, Ro the Rossby number, H/D the fluid depth to ridge width ratio, h/D the ridge height to ridge width ratio and α the angle between the free stream flow and a line perpendicular to the ridge axis. The analysis includes effects of the nonlinear inertial terms. Particular examples of a ridge of triangular cross section and a sinusoidal topography are investigated in some detail. Experiments are presented for a triangular ridge which are in good agreement with the theory.     

Evolutionary history of hoofed mammals during the Oligocene–Miocene transition in Western Europe

The biostratigraphy and diversity patterns of terrestrial, hoofed mammals help to understand the transition between the Palaeogene and the Neogene in Western Europe. Three phases are highlighted: (1) the beginning of the Arvernian (Late Oligocene, MP25-27) was characterised by a “stable” faunal composition including the last occurrences of taxa inherited from the Grande Coupure and of newly emerged ones; (2) the latest Arvernian (Late Oligocene, MP28-30) and the Agenian (Early Miocene, MN1-2) saw gradual immigrations leading to progressive replacement of the Arvernian, hoofed mammals towards the establishment of the “classical” Agenian fauna; (3) the beginning of the Orleanian (Early Miocene, MN3-4) coincided with the African-Eurasian faunal interchanges of the Proboscidean Datum Events and led to complete renewal of the Agenian taxa and total disappearance of the last Oligocene survivors. Faunal balances, poly-cohorts and particularly cluster analyses emphasise these three periods and define a temporally well-framed Oligocene–Miocene transition between MP28 and MN2. This transition started in MP28 with a major immigration event, linked to the arrival in Europe of new ungulate taxa, notably a stem group of “Eupecora” and the small anthracothere Microbunodon. Due to its high significance in the reorganisation of European, hoofed-mammal communities, we propose to name it the Microbunodon Event. This first step was followed by a phase of extinctions (MP29-30) and later by a phase of regional speciation and diversification (MN1-2). The Oligocene–Miocene faunal transition ended right before the two-phased turnover linked to the Proboscidean Datum Events (MN3-4). Locomotion types of rhinocerotids and ruminants provide new data on the evolution of environments during the Oligocene–Miocene transition and help understand the factors controlling these different phases. Indeed, it appears that the faunal turnovers were primarily directed by migrations, whereas the Agenian transitional phase mainly witnessed speciations.     

Broad-scale spatial pattern of forest landscape types in the Guiana Shield

Detecting broad scale spatial patterns across the South American rainforest biome is still a major challenge. Although several countries do possess their own, more or less detailed land-cover map, these are based on classifications that appear largely discordant from a country to another. Up to now, continental scale remote sensing studies failed to fill this gap. They mostly result in crude representations of the rainforest biome as a single, uniform vegetation class, in contrast with open vegetations. A few studies identified broad scale spatial patterns, but only when they managed to map a particular forest characteristic such as biomass. The main objective of this study is to identify, characterize and map distinct forest landscape types within the evergreen lowland rainforest at the sub-continental scale of the Guiana Shield (north-east tropical South-America 10° North-2° South; 66° West-50° West). This study is based on the analysis of a 1-year daily data set (from January 1st to December 31st, 2000) from the VEGETATION sensor onboard the SPOT-4 satellite (1-km spatial resolution). We interpreted remotely sensed landscape classes (RSLC) from field and high resolution remote sensing data of 21 sites in French Guiana. We cross-analyzed remote sensing data, field observations and environmental data using multivariate analysis. We obtained 33 remotely sensed landscape classes (RSLC) among which five forest-RSLC representing 78% of the forested area. The latter were classified as different broad forest landscape types according to a gradient of canopy openness. Their mapping revealed a new and meaningful broad-scale spatial pattern of forest landscape types. At the scale of the Guiana Shield, we observed a spatial patterns similarity between climatic and forest landscape types. The two most open forest-RSLCs were observed mainly within the north-west to south-east dry belt. The three other forest-RSLCs were observed in wetter and less anthropized areas, particularly in the newly recognized “Guianan dense forest arch”. Better management and conservation policies, as well as improvement of biological and ecological knowledge, require accurate and stable representations of the geographical components of ecosystems. Our results represent a decisive step in this way for the Guiana Shield area and contribute to fill one of the major shortfall in the knowledge of tropical forests.     

Environmental controls on the Late Holocene carbonate sedimentation of a karstic lake in the Middle‐Atlas Mountains (Lake Afourgagh,Morocco)

The Lake Afourgagh sediment record and facies successions provide an outstanding example of environmentally controlled carbonate sedimentation. Afourgagh is a small, shallow permanent lake located in the Middle‐Atlas Mountains in Morocco in a karstic context. It is fed by ground waters that are relatively enriched in Mg resulting from the leaching of the Jurassic dolomitic bedrock of the catchment. This eutrophic lake is episodically restricted and characterized by alkaline waters with a fluctuating high Mg/Ca ratio. The maximum extension of the Holocene shoreline coincides with evidence of a lake stabilization level corresponding to the outflow of the lake through a wadi. Lakeshore terrace sediments deposited on an alluvial fan siltstone during the past ca 2500 cal yr bp comprise four main facies: a littoral crust, palaeosols, palustrine silts and charophyte tufas, which reflect different environments from the shoreline toward the deeper water. In the more distal parts, the charophyte tufas display a well‐expressed lamination punctuated by the development of microstromatolites on algae thalli. The mineralogical composition of the carbonates is linked to the facies. While the charophyte tufas are characterized by a relatively high content in aragonite, in addition to low‐Mg calcite, the littoral crust is mainly composed of magnesite. This pattern is related to the evolving chemistry of water due to the influence of charophyte proliferation during dry summers. Calcium‐carbonate precipitation on algae thalli (both bioinduced and microbially mediated) progressively induces an increase in the Mg/Ca ratio of the lake water, while the capillary evaporation of shallow ground waters causes precipitation of a magnesite precursor on the shoreline, producing magnesite during early diagenesis. This effect is characteristic of two episodes: part of the Roman Warm Period and the beginning of the Dark Age Cold Period. The carbonate mineralogy of the different depositional sequences at Afourgagh indicates lake‐level and water‐chemistry fluctuations under a climatic influence. Therefore, among other regional records, the Lake Afourgagh sedimentary record provides useful evidence for reconstructing these environmental changes.     

Distribution of Diatoms and Development of Diatom-Based Models for Inferring Salinity and Nutrient Concentrations in Florida Bay and Adjacent Coastal Wetlands of South Florida (USA)

The composition and distribution of diatom algae inhabiting estuaries and coasts of the subtropical Americas are poorly documented, especially relative to the central role diatoms play in coastal food webs and to their potential utility as sentinels of environmental change in these threatened ecosystems. Here, we document the distribution of diatoms among the diverse habitat types and long environmental gradients represented by the shallow topographic relief of the South Florida, USA, coastline. A total of 592 species were encountered from 38 freshwater, mangrove, and marine locations in the Everglades wetland and Florida Bay during two seasonal collections, with the highest diversity occurring at sites of high salinity and low water column organic carbon concentration (WTOC). Freshwater, mangrove, and estuarine assemblages were compositionally distinct, but seasonal differences were only detected in mangrove and estuarine sites where solute concentration differed greatly between wet and dry seasons. Epiphytic, planktonic, and sediment assemblages were compositionally similar, implying a high degree of mixing along the shallow, tidal, and storm-prone coast. The relationships between diatom taxa and salinity, water total phosphorus (WTP), water total nitrogen (WTN), and WTOC concentrations were determined and incorporated into weighted averaging partial least squares regression models. Salinity was the most influential variable, resulting in a highly predictive model (r _apparent² = 0.97, r _jackknife² = 0.95) that can be used in the future to infer changes in coastal freshwater delivery or sea-level rise in South Florida and compositionally similar environments. Models predicting WTN (r _apparent² = 0.75, r _jackknife² = 0.46), WTP (r _apparent² = 0.75, r _jackknife² = 0.49), and WTOC (r _apparent² = 0.79, r _jackknife² = 0.57) were also strong, suggesting that diatoms can provide reliable inferences of changes in solute delivery to the coastal ecosystem.     

Isotopes of magnesium in the solar atmosphere

We have analysed MgH A ² -X ²(0.0), (1.1), (2.2), (0.1) and (1.2) absorption bands in a sunspot spectrum. By two different methods, which are almost independent of the estimated value of the correction for stray light, we have determined the solar isotopic ratios of magnesium. These ratios are equal to the terrestrial ones - ²⁴Mg²⁵Mg²⁶Mg = 801010.     

Resolution issues in numerical models of oceanic and coastal circulation

The baroclinic and barotropic properties of ocean processes vary on many scales. These scales are determined by various factors such as the variations in coastline and bottom topography, the forcing meteorology, the latitudinal dependence of the Coriolis force, and the Rossby radius of deformation among others. In this paper we attempt to qualify and quantify scales of these processes, with particular attention to the horizontal resolution necessary to accurately reproduce physical processes in numerical ocean models. We also discuss approaches taken in nesting or down-scaling from global/basin-scale models to regional-scale or shelf-scale models. Finally we offer comments on how vertical resolution affects the representation of stratification in these numerical models.