Disturbance Effects on Aquatic Vegetation in Regulated and Unregulated Lakes in Northern Minnesota

The effects of water-level regulation on aquatic macrophyte communities were investigated by comparing two regulated lakes in northern Minnesota with a nearby unregQlated lake. Natural annual fluctuations of about 1.8 m were replaced with fluctuations of 1.1 m and 2. 7 m in the regulated lakes, and the timing of water-level changes was also altered. Quadrats were sampled along transects that followed depth contours representing different plant habitats in the unregulated lake. Ordinations showed that the macrophyte communities at all sampled depths of the regulated lakes differed from those in the unregulated lake. The unregulated lake supported structurally diverse plant communities at all depths. In the lake with reduced fluctuations, only four taxa were present along transects that were never dewatered; all were erect aquatics that extended through the entire water column. In the lake with increased fluctuations, rosette and mat-forming species dominated transects where drawdown occurred in early winter and disturbance resulted from ice formation in the sediments. The natural hydrologic regime at the unregulated lake resulted in intermediate disturbance and high diversity. There was either too little or too much disturbance from water-level fluctuations in the regulated lakes, both resulting in reduced structural diversity

Implications for Faunal Habitat Related to Altered Macrophyte Structure in Regulated Lakes in Northern Minnesota

Water-level regulation has altered the plant species composition and thus the structure of nearshore aquatic macrophyte communities in two regulated lakes in northern Minnesota as compared with a nearby unregulated lake. Results of previous faunal studies in the regulated lakes were used as a basis for assessing the effects of vegetation changes on faunal communities. The unregulated lake with mean annual water-level fluctuations of 1.6 m supported structurally diverse plant communities and varied faunal habitat at all depths studied. Mean annual fluctuations on one regulated lake were reduced to 1.1 m, and dense beds of four erect aquatic macrophytes dominated the 1. 75-m depth that was never dewatered. We suggest that this lack of plant diversity and structural complexity resulted in diminished habitat for invertebrates, reduced availability of invertebrates as food for waterbirds and fish, reduced winter food supplies for muskrats, and reduced feeding efficiency for adult northern pike, yellow perch, and muskellunge. Mean annual fluctuations in the other regulated lake were increased to 2.7 m, and rosette and mat-forming species dominated the 1.25-m depth that was affected by winter drawdowns. We suggest that the lack of larger canopy plants resulted in poor habitat for invertebrates, reduced availability of invertebrates as food for waterbirds and fish, and poor nursery and adult feeding habitat for many species of fish. In addition, the timing and extent of winter drawdowns reduced access to macrophytes as food for muskrats and as spawning habitat for northern pike and yellow perch. In regulated lakes throughout the world, indirect effects on aquatic fauna resulting from alteration of wetland and aquatic macrophyte communities should be considered when water-level management plans are developed

Changes in Wetland Vegetation in Regulated Lakes in Northern Minnesota, USA Ten Years after a New Regulation Plan Was Implemented

Lake-level regulation alters wetland plant communities and their role in providing faunal habitat. Regulation plans have sometimes been changed to restore ecosystem function; however, few studies have shown the effects of such changes. In 2000, a new plan was implemented for regulation of Rainy Lake and Namakan Reservoir in northern Minnesota, USA. We had studied wetland plant communities under the previous 1970 regulation plan in 1987 and used those data to evaluate changes during 2002–2006 and 2010 resampling efforts using the same methods. Ordinations showed that plant communities changed little on Rainy Lake, where regulation changes were minor. However, on Namakan Reservoir, substantial changes had occurred in both vegetation and faunal habitat within two years, as plants favored by dewatering were replaced by submersed aquatic plants favored by year-round flooding under the new 2000 regulation plan. After ten years, Namakan showed greater similarity to unregulated Lac La Croix but still differed overall. Longer-term studies may be needed to determine if the regulation-plan change continues to alter Namakan plant communities. The speed at which changes began suggests that studies on other regulated lakes should begin in the first growing season following implementation of a new regulation plan and should continue periodically for a decade or longer

Economic Impact of a Large-Scale, Collaborative Forest Health Project: A Model for Making a Difference

The U.S. Department of Agriculture Forest Service, Mississippi State University (MSU) Extension, and the Mississippi Forestry Commission partnered on the Southern Pine Beetle Prevention Project, a collaboration on forest health. MSU Extension provided educational outreach to a wide audience of forest landowners and screened applications for the project\u27s tree-thinning cost-share program. From 2006 to 2016, the collaboration spent $4.5 million on educational outreach and cost sharing. Using IMPLAN, we estimated the project\u27s economic contribution to the state at$60.2 million, a value representing a benefit–cost ratio of 13:1. Collaboration is an effective means for agencies to leverage resources, and impact analysis is a useful tool for evaluating Extension program effectiveness

Hydrologic Variability and the Application of Index of Biotic Integrity Metrics to Wetlands: A Great Lakes Evaluation

Interest by land-management and regulatory agencies in using biological indicators to detect wetland degradation, coupled with ongoing use of this approach to assess water quality in streams, led to the desire to develop and evaluate an Index of Biotic Integrity (IBI) for wetlands that could be used to categorize the level of degradation. We undertook this challenge with data from coastal wetlands of the Great Lakes, which have been degraded by a variety of human disturbances. We studied six barrier beach wetlands in western Lake Superior, six drowned-river-mouth wetlands along the eastern shore of Lake Michigan, and six open shoreline wetlands in Saginaw Bay of Lake Huron. Plant, fish, and invertebrate communities were sampled in each wetland. The resulting data were assessed in various forms against gradients of human disturbance to identify potential metrics that could be used in IBI development. Our results suggested that the metrics proposed as potential components of an IBI for barrier beach wetlands of Lake Superior held promise. The metrics for Lake Michigan drowned-river-mouth wetlands were inconsistent in identifying gradients of disturbance; those for Lake Huron open embayment wetlands were yet more inconsistent. Despite the potential displayed by the Lake Superior results within the year sampled, we concluded that an IBI for use in Great Lakes wetlands would not be valid unless separate scoring ranges were derived for each of several sequences of water-level histories. Variability in lake levels from year to year can produce variability in data and affect the reproducibility of data collected, primarily due to extreme changes in plant communities and the faunal habitat they provide. Substantially different results could be obtained in the same wetland in different years as a result of the response to lake-level change, with no change in the level of human disturbance. Additional problems included limited numbers of comparable sites, potential lack of undisturbed reference sites, and variable effects of different disturbance types. We also evaluated our conclusions with respect to hydrologic variability and other major natural disturbances affecting wetlands in other regions. We concluded that after segregation of wetland types by geographic, geomorphic, and hydrologic features, a functional IBI may be possible for wetlands with relatively stable hydrology. However, an IBI for wetlands with unpredictable yet recurring influences of climate-induced, long-term high water periods, droughts, or drought-related fires or weather-related catastrophic floods or high winds (hurricanes) would also require differing scales of measurement for years that differ in the length of time since the last major natural disturbance. A site-specific, detailed ecological analysis of biological indicators may indeed be of value in determining the quality or status of wetlands, but we recommend that IBI scores not be used unless the scoring ranges are calibrated for the specific hydrologic history pre-dating any sampling year

PRDM6 is enriched in vascular precursors during development and inhibits endothelial cell proliferation, survival, and differentiation

The mechanisms that regulate the differentiation program of multipotential stem cells remain poorly understood. In order to define the cues that delineate endothelial commitment from precursors, we screened for candidate regulatory genes in differentiating mouse embryoid bodies. We found that the PR/SET domain protein, PRDM6, is enriched in flk1(+) hematovascular precursor cells using a microarray-based approach. As determined by 5′ RACE, full length PRDM6 protein contains a PR domain and four Krüpple-like zinc fingers. In situ hybridization in mouse embryos demonstrates staining of the primitive streak, allantois, heart, outflow tract, para-aortic splanchnopleura (P-Sp)/aorto-gonadal-mesonephric (AGM) region and yolk sac, all sites known to be enriched in vascular precursor cells. PRDM6 is also detected in embryonic and adult-derived endothelial cell lines. PRDM6 is co-localized with histone H4 and methylates H4-K20 (but not H3) in vitro and in vivo, which is consistent with the known participation of PR domains in histone methyltransferase activity. Overexpression of PRDM6 in mouse embryonic endothelial cells induces apoptosis by activating caspase-3 and inducing G1 arrest. PRDM6 inhibits cell proliferation as determined by BrdU incorporation in endothelial cells, but not in rat aortic smooth muscle cells. Overexpression of PRDM6 also results in reduced tube formation in cultured endothelial cells grown in Matrigel. Taken together, our data indicate that PRDM6 is expressed by vascular precursors, has differential effects in endothelial cells and smooth muscle cells, and may play a role in vascular precursor differentiation and survival by modulating local chromatin-remodeling activity within hematovascular subpopulations during development