Impacts of Rotational Grazing and Riparian Buffers on Physicochemical and Biological Characteristicsof Southeastern Minnesota, USA, Streams

We assessed the relationship between riparian management and stream quality along five southeastern Minnesota streams in 1995 and 1996. Specifically, we examined the effect of rotationally and continuously grazed pastures and different types of riparian buffer strips on water chemistry, physical habitat, benthic macroinvertebrates, and fish as indicators of stream quality. We collected data at 17 sites under different combinations of grazing and riparian management, using a longitudinal design on three streams and a paired watershed design on two others. Continuous and rotational grazing were compared along one longitudinal study stream and at the paired watershed. Riparian buffer management, fenced trees (wood buffer), fenced grass, and unfenced rotationally grazed areas were the focus along the two remaining longitudinal streams. Principal components analysis (PCA) of water chemistry, physical habitat, and biotic data indicated a local management effect. The ordinations separated continuous grazing from sites with rotational grazing and sites with wood buffers from those with grass buffers or rotationally grazed areas. Fecal coliform and turbidity were consistently higher at continuously grazed than rotationally grazed sites. Percent fines in the streambed were significantly higher at sites with wood buffers than grass and rotationally grazed areas, and canopy cover was similar at sites with wood and grass buffers. Benthic macroinvertebrate metrics were significant but were not consistent across grazing and riparian buffer management types. Fish density and abundance were related to riparian buffer type, rather than grazing practices. Our study has potentially important implications for stream restoration programs in the midwestern United States. Our comparisons suggest further consideration and study of a combination of grass and wood riparian buffer strips as midwestern stream management options, rather than universally installing wood buffers in every instance. RID=" ID=" The Unit is jointly sponsored by the US Geological Survey, Biological Resources Division; the Minnesota Department of Natural Resources; the University of Minnesota; and the Wildlife Management Institute.     

Patterns of Aquatic Species Imperilment in the Southern Appalachians: An Evaluation of Regional Databases

/ For regional analyses of species imperilment patterns, data on species distributions are available from the U.S. Fish and Wildlife Service and from the state heritage programs. We compared these two different databases as sources of best available information for regional analyses of patterns of aquatic species imperilment for 132 counties in the southern Appalachians and examined patterns produced from the databases. The heritage program database contained information about a greater number of imperiled species because species need not be federally listed as threatened or endangered to be included in this database. In the southern Appalachians, about half of imperiled molluscs and about one-fourth of imperiled fish were listed as threatened or endangered; much smaller proportions of other taxonomic groups were federally listed. Most threatened and endangered species appeared on both lists, but for about 40% of the species inconsistencies exist, notably a lack of recent records in the heritage program dataset. Numbers of species in each county were significantly different between the two datasets for Georgia, Tennessee, and Virginia, where the largest number of threatened and endangered species reside. Nevertheless, some counties always appeared as centers of imperilment, and the general spatial patterns of imperilment were similar.     

猪肝微粒体体外代谢2,2’,4,4’-四溴联苯醚

多溴联苯醚(PBDEs)是一类在环境中普遍存在的持久性有机污染物,研究PBDEs的体外代谢行为对理解其在体内的富集和转化具有重要意义。文章以猪肝微粒体作为研究对象,以体外代谢形式研究其对2,2’,4,4’-四溴联苯醚(BDE-47)的代谢能力,优化了代谢条件,并研究了0.01、0.05、0.1、0.5、1、5、10 mg/L的BDE-47对细胞色素P450酶系中7-乙氧基香豆素-O-脱乙基酶(ECOD)、7-乙氧基异吩唑酮-O-脱乙基酶(EROD)和苯胺4-羟基化酶(ANH)活性的影响。结果表明,孵育0.1 mg/L的BDE-47时,猪肝微粒体对BDE-47的代谢率可达到28.6%。实验所设各浓度BDE-47均能够保护微粒体的ECOD活性,但较高浓度的BDE-47(0.5、1、5 mg/L)对微粒体的EROD活性有显著抑制作用,而各浓度BDE-47对ANH活性没有显著影响。     

Polychlorinated biphenyls and omega-3 fatty acid exposure from fish consumption, and thyroid cancer among New York anglers

Fish from the Great Lakes contain polychlorinated biphenyls(PCBs)which have been shown to disrupt endocrine function and mimic thyroid hormones,but they also contain beneficial omega-3 fatty acids that may offer protection against endocrine cancers.The purpose of this study was to examine the effects of Lake Ontario fish consumption and the estimated consumption of PCBs and omega-3 fatty acids on the risk of thyroid cancer in a group of sport fishermen.Anglers from the New York State Angler Cohort Study were followed for cancer incidence from 1991–2008.Twenty-seven cases of incident thyroid cancer and 108 controls were included in the analyses.Total estimated fish consumption,estimated omega-3 fatty acid consumption,and estimated PCB consumption from Lake Ontario fish were examined for an association with the incidence of thyroid cancer,while matching on sex,and controlling for age and smoking status.Results from logistic regression indicate no significant associations between fish consumption,short-term estimated omega-3 fatty acids,or estimated PCB consumption from Great Lakes fish and the development of thyroid cancer,but it was suggested that long-term omega-3 fatty acid from Great Lakes fish may be protective of the development of thyroid cancer.In conclusion,fish consumption,with the possible concomitant PCBs,from the Great Lakes does not appear to increase the risk of thyroid cancer in New York anglers.Further research is needed in order to separate the individual health effects of PCBs from omega-3 fatty acids contained within the fish.     

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.     

Identifying Biotic Integrity and Water Chemistry Relations in Nonwadeable Rivers of Wisconsin: Toward the Development of Nutrient Criteria

We sampled 41 sites on 34 nonwadeable rivers that represent the types of rivers in Wisconsin, and the kinds and intensities of nutrient and other anthropogenic stressors upon each river type. Sites covered much of United States Environmental Protection Agency national nutrient ecoregions VII—Mostly Glaciated Dairy Region, and VIII—Nutrient Poor, Largely Glaciated upper Midwest. Fish, macroinvertebrates, and three categories of environmental variables including nutrients, other water chemistry, and watershed features were collected using standard protocols. We summarized fish assemblages by index of biotic integrity (IBI) and its 10 component measures, and macroinvertebrates by 2 organic pollution tolerance and 12 proportional richness measures. All biotic and environmental variables represented a wide range of conditions, with biotic measures ranging from poor to excellent status, despite nutrient concentrations being consistently higher than reference concentrations reported for the regions. Regression tree analyses of nutrients on a suite of biotic measures identified breakpoints in total phosphorus (~0.06 mg/l) and total nitrogen (~0.64 mg/l) concentrations at which biotic assemblages were consistently impaired. Redundancy analyses (RDA) were used to identify the most important variables within each of the three environmental variable categories, which were then used to determine the relative influence of each variable category on the biota. Nutrient measures, suspended chlorophyll a, water clarity, and watershed land cover type (forest or row-crop agriculture) were the most important variables and they explained significant amounts of variation within the macroinvertebrate (R ² = 60.6%) and fish (R ² = 43.6%) assemblages. The environmental variables selected in the macroinvertebrate model were correlated to such an extent that partial RDA analyses could not attribute variation explained to individual environmental categories, assigning 89% of the explained variation to interactions among the categories. In contrast, partial RDA attributed much of the explained variation to the nutrient (25%) and other water chemistry (38%) categories for the fish model. Our analyses suggest that it would be beneficial to develop criteria based upon a suite of biotic and nutrient variables simultaneously to deem waters as not meeting their designated uses.     

Can Warmwater Streams Be Rehabilitated Using Watershed-Scale Standard Erosion Control Measures Alone?

Degradation of warmwater streams in agricultural landscapes is a pervasive problem, and reports of restoration effectiveness based on monitoring data are rare. Described is the outcome of rehabilitation of two deeply incised, unstable sand-and-gravel-bed streams. Channel networks of both watersheds were treated using standard erosion control measures, and aquatic habitats within 1-km-long reaches of each stream were further treated by addition of instream structures and planting woody vegetation on banks (“habitat rehabilitation”). Fish and their habitats were sampled semiannually during 1–2 years before rehabilitation, 3–4 years after rehabilitation, and 10–11 years after rehabilitation. Reaches with only erosion control measures located upstream from the habitat measure reaches and in similar streams in adjacent watersheds were sampled concurrently. Sediment concentrations declined steeply throughout both watersheds, with means ≥40% lower during the post-rehabilitation period than before. Physical effects of habitat rehabilitation were persistent through time, with pool habitat availability much higher in rehabilitated reaches than elsewhere. Fish community structure responded with major shifts in relative species abundance: as pool habitats increased after rehabilitation, small-bodied generalists and opportunists declined as certain piscivores and larger-bodied species such as centrarchids and catostomids increased. Reaches without habitat rehabilitation were significantly shallower, and fish populations there were similar to the rehabilitated reaches prior to treatment. These findings are applicable to incised, warmwater streams draining agricultural watersheds similar to those we studied. Rehabilitation of warmwater stream ecosystems is possible with current knowledge, but a major shift in stream corridor management strategies will be needed to reverse ongoing degradation trends. Apparently, conventional channel erosion controls without instream habitat measures are ineffective tools for ecosystem restoration in incised, warmwater streams of the Southeastern U.S., even if applied at the watershed scale and accompanied by significant reductions in suspended sediment concentration.     

气相色谱法测定鱼组织中的久效磷

采用气相色谱法氮磷检测器测定鱼肉和内脏中的久效磷含量。鱼肉或内脏匀浆后，用正己烷洗涤，二氯甲烷提了，以内标法定量分析，方法简单，灵敏，准确。当取鱼组织0．5g时，方法检测限为0．002mg/kg，加标回收率为72．6％－83．3％，相对标准差在3．3％－7．0％之间。