A comprehensive survey of Douglas Lake, Cheboygan County, MI.

Without knowledge of the natural state of a lake at a given degree of productivity and a profile of its features, it is at best difficult to define what the goal of lake and watershed conservation/management for a lake at that state of development should be. With the objective of developing a full profile of Douglas Lake, Cheboygan County, Michigan, a comprehensive survey was undertaken. The morphometric parameters investigated were a) the method of basin formation, b) morphometry of the lake basin and littoral zone, c) geology underlying the lake basin and watershed, d) underlying soils of the watershed, e) area of the watershed, and f) watershed land use patterns. Physical parameters measured in Douglas Lake included a) depth, b) temperature and summer thermal stratification, c) depth-dependent light intensity, d) conductivity, e) oxygenation, f) chlorophyll a levels, g) alkalinity/hardness, and h) concentrations of nitrogen, phosphorous, and silica (nutrient richness) by strata. Biotic parameters were surveyed by measuring a) the abundance and diversity of non-benthic phytoplankton, b) abundance and diversity of non-benthic zooplanktoon, c) diversity of littoral zone macroinvertebrates, and d) diversity of littoral zone macrophytes. The goal of the survey was to measure the basic morphometric, physical, and biotic parameters of Douglas Lake, analyze the surveyed measurements for their individual indications of trophic status, and ultimately integrate all measurements and analyses to create a picture of the lake's overall productivity. Leeches are usually found under sticks or stones or in the mud on the bottom of lakes, ponds, and streams unless actively in search of food. Of approximately three hundred leeches collected in the Douglas Lake region during June and July, none were found at a depth greater than two feet. The temperature range of the water was between 18 C and 26 C. Gently moving water in protected coves or at the outlets or inlets of lakes is preferred to still water.http://deepblue.lib.umich.edu/bitstream/2027.42/54731/1/3172.pd

Elevated atmospheric CO 2 alters leaf litter quality for stream ecosystems: an in situ leaf decomposition study

Trembling aspen ( Populus tremuloides ) seedlings were exposed to both elevated (720 ppm; ELEV) and ambient (370 ppm; AMB) concentrations of atmospheric CO 2 for a 6-month growing season after which senesced leaves were collected and analyzed for differences in chemical composition. Elevated levels of atmospheric CO 2 significantly increased total phenolic compounds, lignin levels, and C:N ratios, while decreasing the concentration of foliar nitrogen. ELEV and AMB leaf aggregates were placed into a headwater stream in the autumn of 1999 for 4 months to assess microbial activity, macroinvertebrate colonization, and leaf decomposition rates. Elevated CO 2 significantly reduced 30 day microbial community respiration (−36.8%), and percent leaf mass remaining after 30 and 120 days of stream incubation (−9.4% and −13%, respectively). Low resolution of the experimental design for testing macroinvertebrate responses to altered leaves, including the free movement of macroinvertebrates among leaf aggregates, may explain the lack of treatment effect on invertebrate distribution between AMB and ELEV leaves. Elevated CO 2 -induced increases in leaf litter total phenolic compounds, lignins, and C:N appear to have negative effects on leaf decomposition, especially in the early stages of the decay process where microorganisms play a dominant role.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42898/1/10750_2004_Article_5124449.pd