Using Meteorological Model Output as a Surrogate for On-Site Observations to Predict Deposition Velocity

The National Oceanic and Atmospheric Administration's Multi-Layer Model (NOAA-MLM) is used by several operational dry deposition networks for estimating the deposition velocity of O₃, SO₂, HNO₃, and particles. The NOAA-MLM requires hourly values of meteorological variables. Since collection of on-site meteorology can be expensive, a study was performed to compare NOAA-MLM predicted deposition velocitiesusing modeled meteorological data in lieu of on-site meteorological data. NOAA-MLM was run for three sites in the Clean Air Status and Trends Network using on-site data as well as the output of two mesoscale meteorological models, Eta and MM5. The differences between the deposition velocities predictedusing the mesoscale models and those predicted using the on-sitemeteorological measurements ranged from –0.001 to 0.106 cm s^-1 and were within the model error determined in NOAA-MLM evaluation studies. This research shows that the NOAA-MLM is particularly sensitive to differences in atmospheric turbulence,soil moisture budget, and canopy wetness.(On assignment to the National Exposure Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina.) (author for correspondence, e-mail     

探究条纹贻贝过滤率的最佳钙和温度条件以作为物种入侵的潜在预测因子

条纹贻贝（Dreissena rostriformis burgensis）是一种对北美具有高度入侵性的水生物种,能够过滤大量的水并造成严重的生态和经济影响。自20世纪80年代首次入侵五大湖以来,它们的活动范围一直在扩大。为了预测条纹贻贝的活动范围,了解有助于它们活动范围扩大的环境参数至关重要。影响它们分布的两个因素可能是钙和温度。在其它环境条件有利的情况下,这些因素对贻贝的适宜性最佳时其过滤率有可能被最大化,从而使贻贝发挥其生长潜力。偏离最佳条件可能导致过滤率的改变。我们探究了贻贝对两个浮游植物物种—条纹贻贝的常见食物来源之一Ankistrodesmus facaltus和一种不太可口的食物Microcystis icthyoblabe具有最大过滤率时的钙浓度和温度。实验室实验的温度范围为2~30℃,钙浓度在0~180 mg/L之间时,条纹贻贝过滤24小时后,通过细胞计数测定钙浓度和温度条件下的过滤率。使用响应面法,得出碳酸钙浓度为137 mg/L和26℃时达到最大过滤率,为22 mL/mg/h。该信息可用于预测具有较高入侵可能的淡水生境。     

Historical processes constrain patterns in global diatom diversity

There is a long-standing belief that microbial organisms have unlimited dispersal capabilities, are therefore ubiquitous, and show weak or absent latitudinal diversity gradients. In contrast, using a global freshwater diatom data set, we show that latitudinal gradients in local and regional genus richness are present and highly asymmetric between both hemispheres. Patterns in regional richness are explained by the degree of isolation of lake districts, while the number of locally coexisting diatom genera is highly constrained by the size of the regional diatom pool, habitat availability, and the connectivity between habitats within lake districts. At regional to global scales, historical factors explain significantly more of the observed geographic patterns in genus richness than do contemporary environmental conditions. Together, these results stress the importance of dispersal and migration in structuring diatom communities at regional to global scales. Our results are consistent with predictions from the theory of island biogeography and metacommunity concepts and likely underlie the strong provinciality and endemism observed in the relatively isolated diatom floras in the Southern Hemisphere.     

Estuarine surface water allocation: A case study on the interactive role of science in support of management

The inevitable need for freshwater to support the projected population growth along the ocean coast is an emerging issue of potential consequence to adjacent estuaries. A large and controversial water withdrawal/reservoir project in Virginia's coastal plain was the basis of science–management interactions that quantified the vulnerability of tidal freshwater nekton for a series of water withdrawal scenarios. Through progressive iterations of the regulatory review process, which in Virginia includes academic reviews of all aspects of projects proposed to affect the marine and estuarine environment, we developed a novel approach to modeling entrainment probabilities applicable to situations that lack a locally validated hydrodynamic model. The science/management interplay ultimately resulted in surface water allocation strategies that are balances to society and the affected natural environment. Model results showed that the probability of encounter (contact between an egg or larva and one or more units of the intake array) ranged from 1.71% under the conditions of a high river flow and low withdrawal rate to 99.99% under the conditions of a low river flow and high withdrawal rate. The collective body of scientific information was incorporated into regulatory conditions placed on water withdrawals that are designed to protect at least 95% of early life history stages within the intake array's zone of influence.