Modeling the Effects of Potential Salinity Shifts on the Recovery of Striped Bass in the Savannah River Estuary,Georgia–South Carolina,United States

Increased salinity in spawning and nursery grounds in the Savannah River estuary was cited as the primary cause of a 97% decrease in adult striped bass (Morone saxatilis) and a concomitant 96% decrease in striped bass egg production. Restoration efforts focused on environmental remediation and stock enhancement have resulted in restored salinity patterns and increased egg and adult abundances. However, future water needs or harbor development may preclude further recovery by reducing freshwater inflow or increasing salinity intrusion. To assess the effect of potential changes in the salinity regime, we developed models relating discharge, tidal phase, and salinity to striped bass egg and early larval survival and re-cast these in a quantitative Bayesian belief network. The model indicated that a small upstream shift (≤1.67 km) in the salinity regime would have the least impact on striped bass early life history survival, whereas shifts >1.67 km would have progressively larger impacts, with a 8.33-km shift potentially reducing our estimated survival probability by >28%. Such an impact could have cumulative and long-term detrimental effects on the recovery of the Savannah River striped bass population. The available salinity data were collected during average and low flows, so our model represents some typical and some extreme conditions during a striped bass spawning season. Our model is a relatively simplistic, “first-order” attempt at evaluating potential effects of changes in the Savannah River estuarine salinity regime and points to areas of concern and potential future research.     

Downward Migration of Dense Bottom Currents

The focus of this paper is on the dynamics of a dense current flowing along the continental slope, and the frictionally induced downward motion it experiences. In particular, the movement of the lateral boundaries where the isopycnals meet the bottom are considered. The current is taken to be wide compared to the Rossby radius, which is in accordance with observations and makes the dynamics quasigeostrophic. The time development of the plume thickness is studied, using three different parameterisations for the bottom friction.Independently of the choice of parameterisation, the following results are obtained: In the central part of the plume friction acts as a diffusive process to minimise the curvature of the upper surface of the plume. At the upper edge the plume quickly approaches a state with small slope, i.e. small geostrophic velocity and small frictionally induced downward flow. At the lower edge a tongue of dense water shoots out creating a widening layer. The thickness of the migrating layer is approximately equal to the boundary layer depth and its downward speed is comparable to the along-slope geostrophic velocity. The downslope end of the migrating layer may form a steep front which requires some precautions in the numerical procedure.     

Three-Dimensional Modelling of Concentration Fluctuations in Complicated Geometry

The strong fluctuating component in the measured concentration time series of a dispersing gaseous pollutant in the atmospheric boundary layer, and the hazard level associated to short-term concentration levels, demonstrate the necessity of calculating the magnitude of turbulent fluctuations of concentration using computational simulation models. Moreover the computation of concentration fluctuations in cases of dispersion in realistic situations, such as built-up areas or street canyons, is of special practical interest for hazard assessment purposes. In this paper, the formulation and evaluation of a model for concentration fluctuations, based on a transport equation, are presented. The model is applicable in cases of complex geometry. It is included in the framework of a computational code, developed for simulating the dispersion of buoyant pollutants over complex geometries. The experimental data used for the model evaluation concerned the dispersion of a passive gas in a street canyon between 4 identical rectangular buildings performed in a wind tunnel. The experimental concentration fluctuations data have been derived from measured high frequency concentrations. The concentration fluctuations model is evaluated by comparing the model's predictions with the observations in the form of scatter plots, quantile-quantile plots, contour plots and statistical indices as the fractional bias, the geometrical mean variance and the factor-of-two percentage. From the above comparisons it is concluded that the overall model performance in the present complex geometry case is satisfactory. The discrepancies between model predictions and observations are attributed to inaccuracies in prescribing the actual wind tunnel boundary conditions to the computational code.     

Identifying the largest individual sample value from a two-way composite sampling design

Composite sampling techniques for identifying the largest individual sample value seem to be cost effective when the composite samples are internally homogeneous. However, since it is not always possible to form homogeneous composite samples, these methods can lead to higher costs than expected. In this paper we propose a two-way composite sampling design as a way to improve on the cost effectiveness of the methods available to identify the largest individual sample value.     

一个新的拓扑指数用于芳烃化合物溶解度、分配系数及生物毒性的研究

在分子拓扑理论的基础上,提出了一个新的拓扑指数Yx,并用Yx研究了芳烃化合物的溶解度、分配系数及生物毒(活）性,给出了相关方程。结果表明,新方法计算方便,物理意义明确,预测值与相应的实验值较吻合。     

Phylogenetic relationships within the Octocorallia (Cnidaria: Anthozoa) based on nuclear 18S rRNA sequences

We determined the nuclear 18S rRNA sequences for 41 species of octocorals and used these to address the validity of the historical ordinal divisions and the current subordinal divisions within the subclass Octocorallia. We also explored the phylogenetic affinities of the species Dendrobrachia paucispina, which was originally classified in the order Antipatharia (subclass Ceriantipatharia) although polyp structure indicates it belongs in the subclass Octocorallia. Trees constructed using maximum likelihood techniques are incongruent with the current and historical taxonomy of the Octocorallia. There appeared to be three major clades of octocorals. The first clade included most, but not all, pennatulaceans as a monophyletic group. The second clade contained 21 species, representing all major octocoral groups other than pennatulaceans. The third clade contained members from three suborders of the Alcyonacea and one member of the Pennatulacea. These data could not be used to distinguish the branching order of the three major clades. The species D. paucispina had a close affinity with the genera Corallium and Paragorgia (Alcyonacea: Scleraxonia), although its morphology suggests it is more similar to the genus Chrysogorgia (Alcyonacea: Calcaxonia). The morphological character of dimorphism (the presence of both autozooids and siphonozooids within a single colony) corresponded loosely with the topology of the most likely trees, and a single origin of dimorphism could not be rejected. Despite sampling from the majority of families within the Octocorallia, many of the relationships within this group remain ambiguous. Received: 16 June 2000 / Accepted: 14 September 2000     

A Systematic Test of an Enterprise Strategy for Community-Based Biodiversity Conservation

Abstract: A commonly held belief is that if people can benefit financially from enterprises that depend on nearby forests, reefs, and other natural habitats, then they will take action to conserve and sustainably use them. The Biodiversity Conservation Network brought together conservation and development organizations and local communities to systematically test this hypothesis across 39 conservation project sites in Asia and the Pacific. Each project implemented one or more community-based enterprises such as setting up an ecotourism lodge, distilling essential oils from wild plant roots, producing jams and jellies from forest fruits, harvesting timber, or collecting marine samples to test for pharmaceutical compounds. Each project team collected the biological, enterprise, and social data necessary to test the network's hypothesis. We present the results of this test. We found that a community-based enterprise strategy can lead to conservation, but only under limited conditions and never on its own. We summarize the specific conditions under which an enterprise strategy will and will not work in a decision chart that can be used by project managers to determine whether this strategy might make sense at their site. We also found that an enterprise strategy can be subsidized and still create a net gain that pays for conservation. Based on our experiences, we recommend developing "learning portfolios" that combine action and research to test other conservation strategies.