Relationship between biodiversity and landscape structure in the Gyungan stream basin,central Korea

The relationship between landscape structure and biodiversity was investigated in the Gyungan stream basin, central Korea, in order to prepare a biodiversity conservation plan. The study area was divided into upstream, midstream, downstream and Gonjiam stream sub‐watersheds based on the land use pattern of each sub‐watershed. The quality of the terrestrial landscape was assessed by connectivity and percentages of deciduous broad‐leaved forest and urbanized area. The quality of the terrestrial landscape was the highest in the downstream sub‐watershed followed by Gonjiam stream, midstream and upstream sub‐watersheds. The quality of the riparian landscape assessed by percentages of the number and the area that the wetland vegetation elements occupy in the whole area showed a similar trend to that of terrestrial landscape. The diversity of all taxa including fish, reptiles and amphibians, birds, mammals and wetland vegetation except benthic macroinvertebrates was the highest downstream. The diversity of benthic macroinvertebrates was the highest in the Gonjiam stream sub‐watershed. Thus, biodiversity was shown to be the highest in the downstream sub‐watershed, followed, in order, by Gonjiam stream, midstream and upstream sub‐watersheds in proportion to landscape quality. On the other hand, the quality of the aquatic environment based on the ecological score of benthic macroinvertebrate (ESB) index was the highest downstream, followed, in order, by upstream, Gonjiam stream and midstream areas. This trend is different from that of biodiversity. In order to improve landscape quality degraded by excessive land use and to increase biodiversity, we recommended a restoration plan that addresses both ecosystem and landscape.     

Large-scale climate change vulnerability assessment of stream health

Freshwater streams are critical resources that provide multiple benefits to humans and aquatic biota alike. As climate changes, it is projected that changes to the hydrological cycle and water temperatures will affect individual biota and aquatic ecosystems as a whole. The goal of this study was to determine the extent of climate change impacts on stream ecosystems as represented by four commonly used stream health indicators (Ephemeroptera, Plecoptera, and Trichoptera taxa (EPT), Family Index of Biotic Integrity (FIBI), Hilsenhoff Biotic Index (HBI), and fish Index of Biotic Integrity (IBI)). Seven watersheds in Michigan were selected based on stream thermal regimes. The Soil and Water Assessment Tool was used to simulate streamflow and pollutant loads. Important variables for each thermal class were selected using a Bayesian variable selection method and used as inputs to adaptive neuro-fuzzy inference systems models of EPT, FIBI, HBI, and IBI. Finally, an ensemble of climate models from the Coupled Model Intercomparison Project Phase 5 were used to determine the impacts of climate on the stream health in 2020–2040 compared to 1980–2000. The risk of declining stream health was determined using cumulative distribution functions. A stream temperature regression model was also developed to assess potential changes in stream thermal regimes, which could cause shifts in composition of aquatic communities. Several flow regime variables, including those related to flow variability, duration of extreme events, and timing were mainly affected by changing climate. At the watershed scale, most indicators were relatively insensitive to changing climate and the magnitude of stream health decline was low. However, at the reach scale, there are many instances of high risk and large magnitude of declines in the stream health indicators. At the same time, several streams experienced changes in thermal class, mostly transitioning from cold-transitional and cool streams to warm streams. This research demonstrated the applicability of the stream health modeling process in performing a climate change impacts assessment.     

Aquatic degradation in shallow coastal plain lakes: Gradients or thresholds?

The establishment of introduced species in aquatic and wetland habitats is often associated with human-related environmental degradation. In the blackwater streams of the New Jersey Pinelands, the presence of nonnative species drives the relationship between community composition and watershed disturbance associated with developed land and upland agriculture. Most Pinelands lakes are shallow, artificial stream impoundments. In this study, we determined if land-use gradients or thresholds were associated with the presence of nonnative-herbaceous-plant, woody-plant, fish, and anuran species in 30 Pinelands stream impoundments. Correlation and regression analyses indicated that the response of all four taxonomic groups to watershed disturbance was an increase in the number of nonnative species and the proportion of total species richness represented by nonnative species. Native-anuran richness decreased along the watershed-disturbance gradient. We found both linear and nonlinear responses when relating species-richness attributes to the percentage of altered land (combined percentage of upland agriculture and developed land) in the associated watersheds, but the nonlinear responses cannot be considered land-use-related degradation-threshold responses. The breaks in the regression lines describing the relationship between the percentage of total species richness represented by nonnative plants and fish and altered land in our Pinelands watersheds did not represent a degradation threshold because, with the exception of the percentage of total species richness represented by nonnative-anuran species, a progressive decline in aquatic integrity was observed before the break points. Kruskal–Wallis ANOVA revealed significant differences in species-richness attributes only among stream impoundments with contrasting altered-land profiles, providing further evidence that aquatic degradation was progressive. Logistic regression identified the point along the watershed-disturbance gradient at which the probability of encountering nonnative bullfrogs was greater than that for native carpenter frogs.     

Using multiple indicators to evaluate the ecological integrity of a coastal plain stream system

We demonstrate the use of multiple indicators to characterize the ecological integrity of a coastal plain stream system in the New Jersey Pinelands in relation to human-induced watershed alterations. The individual indicators include pH, specific conductance, stream vegetation and stream-fish, impoundment-fish, and anuran assemblages. We evaluate and compare the utility of the individual and multiple environmental and biological indicators and present a relatively straightforward method for ranking sites. Specific conductance and pH measured at 88 monitoring sites varied in relation to the percentage of altered land (developed land and upland agriculture) within the associated watersheds. All three environmental variables were associated with variations in the composition of stream vegetation and stream fish, impoundment fish, and anuran assemblages. With the exception of impoundment fish, the association between altered land and the multiple-indicator scores based on the two water-quality indicators and the four biological indicators was stronger than that displayed by any of the individual variables.     

Geomorphic predictors of riparian vegetation in small mountain watersheds

Aims Hydrogeomorphic processes operating at watershed, process zone and site scales influence the distribution of riparian vegetation. However, most studies examining the relationships between hydrogeomorphic processes and riparian vegetation are conducted at site scales. We quantified the relative importance of watershed, process zone and site geomorphic characteristics for predicting riparian plant community types and plant species abundances in four small mountain watersheds in central Nevada, USA.Methods We mapped riparian vegetation types and identified process zones (based on dominant geomorphic process and valley fill material) within the watersheds. We sampled sites in each combination of vegetation type and process zone (n = 184 sites) and collected data on watershed scale factors, valley and stream geomorphic characteristics and on plant cover of each geomorphic surface. Plant community types were defined by cluster and indicator species analyses of plant cover data, and related to geomorphic variables using ordination analysis (nonmetric multidimensional scaling). Linear mixed effects models were used to predict abundances of indicator species.Important findings Variables describing position in the watershed (elevation, contributing area) that are related to gradients of temperature, moisture and stream discharge were of primary importance in predicting plant community types. Variables describing local geomorphic setting (valley width, stream gradient, channel sediments, geomorphic surface height) were of secondary importance, but accurately described the geomorphic setting of indicator species. The process zone classification did not include position in the watershed or channel characteristics and only predicted plant community types with unique geomorphic settings. In small mountain watersheds, predicting riparian vegetation distribution requires explicit consideration of scale and geomorphic context within and among watersheds in addition to site variables.     

Is the biological classification of benthic diatom communities concordant with ecotypes?

In this study a biological classification based on diatom communities (a posteriori classification) was used to search for the most appropriate a priori classification in reference conditions, on the basis of 31 reference sites encompassing eight watersheds in the NE Iberian Peninsula. We considered three different a priori systems for comparison: (i) a typological classification (ecotypes and subecotypes) based on geomorphology and water flow; (ii) the watershed as a unit, irrespective of its size; and (iii) a classification based on the geographical distance between sites under the assumption that biological characteristics are increasingly similar in geographically closer sites. Classification in ecotypes and subecotypes was the most robust with minor differences between them. The watershed (hydrological units) classification was significant though weaker than the typological classification and there was a larger environmental variation within watersheds than within ecotypes. Finally, results showed that geographically closer sites were not more biologically similar in terms of diatom community composition. We can conclude that the ecotypological environmental-based classifications developed by the local water agency did adequately describe the biological classification based on epilithic diatoms.     

Stream community richness predicts apex predator occupancy dynamics in riparian systems

Streams and adjacent riparian habitats represent linked terrestrial and aquatic ecosystems that exchange materials and energy. Recognized relationships among apex predators and ecosystem biodiversity led us to hypothesize that these predators in riparian‐stream systems were more likely to be found in sites with high stream quality, defined as increased ecosystem function and integrity. In our freshwater study system, river otter Lontra canadensis and mink Neovison vison play critical roles as apex predators. We used multi‐season occupancy modelling across three sampling years (2012–2014) to compare aspects of the stream communities that explain occupancy dynamics of river otter and mink, including their interactions with other semi‐aquatic mammals. We surveyed for semi‐aquatic mammals at 77 sites in 12 major watersheds in southern Illinois, USA (44 526 km²). Naïve occupancy differed among years but generally increased for river otter, and remained high (≥93.5%) for mink. Increasing substrate availability increased detectability of river otter, whereas mink detection varied by survey period. Occupancy of river otter during the initial survey period was higher in sites closer to reintroduction points. Probability of colonization of river otter was positively associated with macroinvertebrate index of biotic integrity, fish species richness, and beaver presence. Sites with high species richness of fish families preferred by river otter also had increased river otter persistence. Mink occupied sites with increased fish richness, muskrat presence and mussel community index. Taken together, our results show occupancy of both mink and river otter were predicted by aspects of prey diversity and presence, indicating the importance of community composition in occupancy dynamics of riparian predators. Ultimately, these relationships suggest that habitat heterogeneity and system stability are important to apex predator site use. However, the relative role of bottom–up and top–down forcing in stream systems remains to be resolved.     

Distribution of methanotrophs in managed and highly disturbed watersheds

Potential impacts of mechanized infantry training activities on the distribution of methanotrophs were investigated in two watersheds on Fort Benning, a US Army installation in southwest Georgia, USA. The Bonham Creek watershed shows significant impacts from intensive training exercises, including severe erosion and deposition of sediments in bottomlands. The Sally Branch watershed is a managed watershed with only limited exposure to mechanized training activity and much less erosion. A clone library of the gene encoding particulate methane monooxygenase, pmoA, was constructed from DNA extracted from Sally Branch bottomland and upland samples. Libraries were constructed from only one watershed in the interest of decreasing the amount of sequencing, and Sally Branch was chosen for construction of these libraries because relatively undisturbed environments generally exhibit higher levels of diversity. The Sally Branch pmoA libraries were dominated by a deeply rooted lineage related to Type I methanotrophs (the “Benning soil cluster γ,” BSCγ). Sequences clustering with known Type II methanotrophs were restricted to samples taken from the Sally Branch bottomland sample. Terminal restriction fragment length polymorphism (T-RFLP) analysis of pmoA was applied to samples taken from transects located in upland and bottomland sites within the two watersheds. Observed T-RFs matched well with T-RFs predicted from sequences obtained from the clone library, with few exceptions. Principal components analysis revealed that in both watersheds most T-RFLPs from upland samples clustered separately from bottomland samples. Upland and bottomland T-RFLPs clustered separately in the Sally Branch transect; however, some Bonham Creek bottomland T-RFLPs clustered within the upland cluster, suggesting mixing of upland with bottomland soils in this watershed. Assemblages were, in general, similar between the eroded and managed watersheds, although erosional soil movement likely resulted in mixing of upland assemblages with bottomland assemblages in the Bonham Creek watershed.     

Stream invertebrate communities of Mongolia: current structure and expected changes due to climate change

ABSTRACT: BACKGROUND: Mongolia's riverine landscape is divided into three watersheds, differing in extent of permafrost, amount of precipitation and in hydrological connectivity between sub-drainages. In order to assess the vulnerability of macroinvertebrate communities to ongoing climate change, we consider the taxonomic and functional structures of stream communities in two major watersheds: The Central Asian Internal Watershed (CAIW) and the Arctic Ocean Watershed (AOW), together covering 86.1% of Mongolia's surface area. We assess the consequences of the hydrological connectivity between sub-drainages on the nestedness and distinctness of the stream communities. And accordingly, we discuss the expected biotic changes to occur in each watershed as a consequence of climate change. RESULTS: Gamma and beta diversities were higher in the CAIW than the AOW. High community nestedness was also found in the CAIW along with a higher heterogeneity of macroinvertebrate assemblage structure. Assemblages characteristic of cold headwater streams in the CAIW, were typical of the drainages of the Altai Mountain range. Macroinvertebrate guilds of the CAIW streams exhibited traits reflecting a high stability and low resilience capacity for eutrophication. In contrast, the community of the AOW had lower nestedness and a combination of traits reflecting higher stability and a better resilience capacity to disturbances. CONCLUSION: Higher distinctness of stream communities is due to lower connectivity between the drainages. This was the case of the stream macroinvertebrate communities of the two major Mongolian watersheds, where connectivity of streams between sub-drainages is an important element structuring their communities. Considering differences in the communities' guild structure, hydrological connectivity and different magnitudes of upcoming impacts of climate change between the two watersheds, respective stream communities will be affected differently. The hitherto different communities will witness an increasing differentiation and divergent adaptations for the upcoming changes. Accordingly, in an increasing awareness to protect Mongolia's nature, our results encourage adapting conservation planning and management strategies specifically by watershed.     

Stream communities across a rural–urban landscape gradient

Rapid urbanization throughout the world is expected to cause extensive loss of biodiversity in the upcoming decades. Disturbances associated with urbanization frequently operate over multiple spatial scales such that local species extirpations have been attributed both to localized habitat degradation and to regional changes in land use. Urbanization also may shape stream communities by restricting species dispersal within and among stream reaches. In this patch-dynamics view, anthropogenic disturbances and isolation jointly reduce stream biodiversity in urbanizing landscapes. We evaluated predictions of stream invertebrate community composition and abundance based on variation in environmental conditions at five distinct spatial scales: stream habitats, reaches, riparian corridors and watersheds and their spatial location within the larger three-river basin. Despite strong associations between biodiversity loss and human density in this study, local stream habitat and stream reach conditions were poor predictors of community patterns. Instead, local community diversity and abundance were more accurately predicted by riparian vegetation and watershed landscape structure. Spatial coordinates associated with instream distances provided better predictions of stream communities than any of the environmental data sets. Together, results suggest that urbanization in the study region was associated with reduced stream invertebrate diversity through the alteration of landscape vegetation structure and patch connectivity. These findings suggest that maintaining and restoring watershed vegetation corridors in urban landscapes will aid efforts to conserve freshwater biodiversity.     

Artificial ponds: a substitute for natural Beaver ponds in a Central European Highland (Eifel,Germany)?

Stormwater ponds are increasingly common aquatic habitats whose biotic communities are largely unexplored. As anthropogenic development continues to alter the landscape, watershed land use is gaining recognition for its potential to predict species compositions in aquatic systems. This study reports species composition of five aquatic hemipteran families (Notonectidae, Corixidae, Belostomatidae, Nepidae, Pleidae) in 28 permanent, artificial stormwater ponds in watersheds with different land covers and associated contaminant input. We hypothesized that land cover variables would be significant drivers of aquatic hemipteran community structure in ponds, and that ponds with a high percentage of agricultural and lawn cover in the watershed would be characterized by the absence of species intolerant of the chemical, physical, and ultimately biotic changes associated with these watersheds. Non-metric multi-dimensional scaling (NMS) was used to identify dominant gradients of species composition and environmental variables. Pond morphology variables, watershed lawn, watershed agriculture, and predatory fish abundance were each found to have statistically significant correlations with hemipteran community structure. The abundance of Notonecta undulata, the species responsible for creating the largest (ranked) distance in species structure among ponds, was positively correlated with shallow, fishless ponds and independent of land use variables. The abundances of four species of corixids were negatively correlated with watershed agriculture, and hemipteran richness was positively correlated with watershed lawn and negatively correlated with pond surface area. Heirarchical cluster analysis revealed non-random hemipteran species assemblages in which congeneric corixid species tended to co-occur, contradicting traditional niche theory. Since artificial stormwater ponds are chemically different from natural-pond habitat and rapidly increasing in number, knowledge of which insect species are capable of thriving in this environment and their relationship to land use in the watershed is of both environmental and evolutionary interest. Handling editor: D. Dudgeon     

河流流量对流域下垫面特性的响应

以美国切斯比克湾地区为例,对该区域150个小流域的下垫面特性(包括土地利用类型、地面不透水系数和土壤物理属性)进行了提取,根据1984—2004年间逐日流量观测数据计算出了33个水文指标,运用逐步回归方法在不同地理区分析了9种下垫面特性对其中17个重要水文指标的影响。结果表明:随着草地和林地比例的增加,流量趋于减小、流量变化趋于稳定,随着建设用地和不透水层的增加,流量增加、流量变化剧烈,随着土壤水文组等级的升高,流量减少;在整个切斯比克湾流域,对流域下垫面特性响应最为显著的水文指标是高脉冲个数及历时,在阿巴拉契亚高地地区响应最为显著的水文指标是年极值流量、高脉冲个数及历时,在皮德蒙特山地响应最为显著的水文指标是高脉冲个数及历时,在沿海平原地区响应最为显著的水文指标是高脉冲个数及历时、流量变化的速率与频率。     

Long-term changes in ecosystem health of two Hudson Valley watersheds, New York, USA, 1936–2001

We examined long-term ecological change in two Hudson River tributaries, the Wappinger and Fishkill Creek watersheds in Dutchess County, New York State. Fish data spanning 65 years (1936, 1988, 1992, and 2001) and shorter term macroinvertebrate data (1988, 2001) were used to assess the influence of land use practices. Between 1988 and 2001, macroinvertebrate index Biotic Assessment Profile (BAP) improved by 113–165% in the Fishkill Creek watershed, and fish Index of Biotic Integrity (IBI) improved by 117–140%. Fish IBI and fish species richness were significantly different (p < 0.01) between the watersheds, with Wappinger Creek in better condition. Long-term fish IBI scores showed degradation in both watersheds since the 1930s. Changes in species composition suggest community homogenization on par with overall changes in the fish fauna of New York. Most notable were increases in tolerant species and declines in intolerant or moderately tolerant species. Whereas Fishkill Creek IBIs showed decline in 1988 relative to 1936, followed by improvement, Wappinger Creek declined monotonically in environmental quality. Development has intensified in both watersheds, but Fishkill Creek is improving while Wappinger Creek watershed is undergoing less mitigated degradation. We find that older, semi-quantitative data can be used to construct environmental quality indicators, and can be of great use for measuring long-term change.     

基于陆地-水生态系统耦合的海河流域水生态功能分区

水生态功能分区是针对水生态系统特征的陆地生态系统划分,是为流域水生态管理提供生态背景和基本单元。陆地-水生态系统的耦合是水生态功能分区的核心,但多停留在个别小流域进行理论探讨,大型流域的实际案例较少。针对海河流域独特的气候、地貌、水文和人类活动特征,提出了水生态功能分区的三级指标体系。一级二级区针对气候、地貌、水文背景进行"自上而下"的分区,三级区针对人类活动对水资源、水环境、生境影响,采用"自下而上"的分区方法。最终,海河流域划分了6个一级区、16个二级区和73个三级区。研究充分体现了"以水定陆、以陆控水"的基本原则,以及"自下而上"和"自上而下"分区方法的优点,结果可为海河流域水生态管理提供科学依据,为水资源空间调配与合理利用、产业结构布局与区域协调等服务。     

Denitrification in Agriculturally Impacted Streams: Seasonal Changes in Structure and Function of the Bacterial Community

Denitrifiers remove fixed nitrogen from aquatic environments and hydrologic conditions are one potential driver of denitrification rate and denitrifier community composition. In this study, two agriculturally impacted streams in the Sugar Creek watershed in Indiana, USA with different hydrologic regimes were examined; one stream is seasonally ephemeral because of its source (tile drainage), whereas the other stream has permanent flow. Additionally, a simulated flooding experiment was performed on the riparian benches of the ephemeral stream during a dry period. Denitrification activity was assayed using the chloramphenicol amended acetylene block method and bacterial communities were examined based on quantitative PCR and terminal restriction length polymorphisms of the nitrous oxide reductase (nosZ) and 16S rRNA genes. In the stream channel, hydrology had a substantial impact on denitrification rates, likely by significantly lowering water potential in sediments. Clear patterns in denitrification rates were observed among pre-drying, dry, and post-drying dates; however, a less clear scenario was apparent when analyzing bacterial community structure suggesting that denitrifier community structure and denitrification rate were not strongly coupled. This implies that the nature of the response to short-term hydrologic changes was physiological rather than increases in abundance of denitrifiers or changes in composition of the denitrifier community. Flooding of riparian bench soils had a short-term, transient effect on denitrification rate. Our results imply that brief flooding of riparian zones is unlikely to contribute substantially to removal of nitrate (NO₃ ^-) and that seasonal drying of stream channels has a negative impact on NO₃ ^- removal, particularly because of the time lag required for denitrification to rebound. This time lag is presumably attributable to the time required for the denitrifiers to respond physiologically rather than a change in abundance or community composition.     

Return of Salmon-Derived Nutrients from the Riparian Zone to the Stream during a Storm in Southeastern Alaska

Spawning salmon deliver nutrients (salmon-derived nutrients, SDN) to natal watersheds that can be incorporated into terrestrial and aquatic food webs, potentially increasing ecosystem productivity. Peterson Creek, a coastal watershed in southeast Alaska that supports several species of anadromous fish, was sampled over the course of a storm during September 2006 to test the hypothesis that stormflows re-introduce stored SDN into the stream. We used stable isotopes and PARAFAC modeling of fluorescence excitation–emission spectroscopy to detect flushing of DOM from salmon carcasses in the riparian zone back into a spawning stream. During the early storm hydrograph, streamwater concentrations of NH₄–N and total dissolved phosphorus (TDP), the fluorescent protein tyrosine and the δ¹⁵N content of DOM peaked, followed by a rapid decrease during maximum stormflow. Although δ¹⁵N has previously been used to track SDN in riparian zones, the use of fluorescence spectroscopy provides an independent indicator that SDN are being returned from the riparian zone to the stream after a period of intermediate storage outside the stream channel. Our findings further demonstrate the utility of using both δ¹⁵N of streamwater DOM and fluorescence spectroscopy with PARAFAC modeling to monitor how the pool of streamwater DOM changes in spawning salmon streams.     

钱塘江中游流域不同空间尺度环境因子对底栖动物群落的影响

溪流底栖动物群落结构受不同空间尺度环境因子的共同作用。基于2010年钱塘江中游流域60个样点的大型底栖无脊椎动物和环境变量数据,寻找与研究流域底栖动物群落结构变化密切相关的关键环境变量,解析流域尺度和河段尺度的环境因子对底栖动物群落的相对影响。PCA分析表明该区域的主要环境梯度是流域内的土地利用类型及其引起的溪流物理生境退化程度和水体营养状态。CCA分析发现影响底栖动物群落的流域尺度的关键环境变量是纬度、海拔、样点所在流域大小、森林用地百分比,河段尺度是总氮、总磷、钙浓度、二氧化硅浓度和平均底质得分。偏CCA分析得到两种尺度环境因子对底栖动物变异的总解释量为26.4%,流域尺度和河段尺度变量分别为总解释量的50%和31%;方差分解结果表明研究区域大型底栖无脊椎动物受到两种尺度环境因子的综合影响,且流域尺度环境因子较河段尺度环境因子更为重要,体现了其在溪流生态系统保护、恢复、监测和评价中的重要参考价值。     

Effects of Watershed History on Dissolved Organic Matter Characteristics in Headwater Streams

Dissolved organic matter (DOM) is recognized as a major component in the global carbon cycle and is an important driver in aquatic ecosystem function. Climate, land use, and forest cover changes all impact stream DOM and alter biogeochemical cycles in terrestrial environments. We determined the temporal variation in DOM quantity and quality in headwater streams at a reference watershed (REF), a watershed clear-cut 30 years ago (CC), and a watershed converted to a white pine plantation 50 years ago (WP) at the US Forest Service, Coweeta Hydrologic Laboratory, in the Nantahala Mountains of western North Carolina, USA. Average stream dissolved organic carbon (DOC) concentrations in CC or WP were 60 and 80% of those in REF, respectively. Stream DOM composition showed that the difference was mainly due to changes in humic-like components in chromophoric DOM. In addition, excitation–emission matrix fluorescence data with parallel factor analysis indicate that although the concentration of protein-like components did not differ significantly among watersheds, their relative abundance showed an enrichment in CC and WP compared to REF. The ratio of humic acid-type to fulvic acid-type components was highest and lowest at REF and WP, respectively. Our data suggest that forest ecosystem disturbance history affects the DOM quantity and quality in headwater streams over decades as a result of changes in watershed soil organic matter characteristics due to differences in organic matter inputs.     

Restricted gene flow between resident Oncorhynchus mykiss and an admixed population of anadromous steelhead

The species Oncorhynchus mykiss is characterized by a complex life history that presents a significant challenge for population monitoring and conservation management. Many factors contribute to genetic variation in O. mykiss populations, including sympatry among migratory phenotypes, habitat heterogeneity, hatchery introgression, and immigration (stray) rates. The relative influences of these and other factors are contingent on characteristics of the local environment. The Rock Creek subbasin in the middle Columbia River has no history of hatchery supplementation and no dams or artificial barriers. Limited intervention and minimal management have led to a dearth of information regarding the genetic distinctiveness of the extant O. mykiss population in Rock Creek and its tributaries. We used 192 SNP markers and collections sampled over a 5‐year period to evaluate the temporal and spatial genetic structures of O. mykiss between upper and lower watersheds of the Rock Creek subbasin. We investigated potential limits to gene flow within the lower watershed where the stream is fragmented by seasonally dry stretches of streambed, and between upper and lower watershed regions. We found minor genetic differentiation within the lower watershed occupied by anadromous steelhead (F_ST = 0.004), and evidence that immigrant influences were prevalent and ubiquitous. Populations in the upper watershed above partial natural barriers were highly distinct (F_ST = 0.093) and minimally impacted by apparent introgression. Genetic structure between watersheds paralleled differences in local demographics (e.g., variation in size), migratory restrictions, and habitat discontinuity. The evidence of restricted gene flow between putative remnant resident populations in the upper watershed and the admixed anadromous population in the lower watershed has implications for local steelhead productivity and regional conservation.     

A geospatial approach for assessing denitrification sinks within lower-order catchments

Local decision makers can influence land use practices that alter N loading and processing within the drainage basin of lower-order stream reaches. Because many practices reduce water retention times and alter the timing and pathways of water flow, local decisions regarding land use can potentially exert a major influence on watershed N export. We illustrate a geospatial approach for assessing the role of denitrification sinks in watershed N delivery at the local level using: (a) widely available geospatial data, (b) current findings from peer-reviewed literature, (c) USGS stream gage data, and (d) locally based data on selected stream attributes. With high resolution, high quality GIS data increasingly available to local communities, they are now in a position to guide local management of watershed N by targeting upland source controls and by identifying landscape sinks for protection and/or restoration. We characterize riparian wetlands, lentic water bodies, and stream reaches as N sinks in the landscape and use geospatial particle tracking to estimate flow paths from N sources and evaluate N removal within sinks. We present an example analysis of the Chickasheen drainage basin, RI, USA, comparing N flux from three equivalent hypothetical N source areas situated in different regions of the watershed and illustrating the role of each N sink type in mediating N flux. Because our goal is to generate a tool that is used by and useful to decision makers we are exploring methods to better understand how decision makers understand and respond to the manner in which information is presented.