The purpose of this research was to determine population trends of major nearshore fish species in Indiana waters of Lake Michigan from 1984 to 1998 to gain insight into species dynamics. Index trawl samples were collected twice monthly from June through August at three locations. Trends of catch-per-unit-effort (CPUE) were investigated for the most abundant species: yellow perch (Perca flavescens), alewife (Alosa pseudoharengus), spottail shiner (Notropis hudsonius), rainbow smelt (Osmerus mord iz), and bloater (Coregonus hoyi). Trawl catch of yellow perch, alewife, and spottail shiners at sites M, K, and G were strongly correlated suggesting similar fluctuations. Young-of-the-year trawl catch revealed that insight to population dynamics of species was not always reliable. Trawl CPUE of > age 1 fish provided insight to dynamics of the major species at all sample locations with strong trend similarities between sites. No strong major species interactions were found using simple linear correlations. / Department of Biology

Yellow perch, Perca flavescens, were collected by night trawling and gill netting at 5 m in a study area near Kintzele Ditch in Indiana waters of Lake Michigan during the months of June through September, 1975. Additional collections made by the Indiana Department of Natural Resources and the U.S. Fish and Wildlife Service using gill nets were included in some aspects of the study.Population characteristics were analyzed and compared to other studies. The rate of growth was significantly greater than in past Great Lakes' populations. The calculated length-weight relationships and growth rates were comparable to those reported by recent studies for southern Lake Michigan. Growth differed between males and females of the same age, and different ages were often represented in the same length interval. Nearly all male yellow perch were mature by age I and 130 mm. About half of the age II females and most at the 200 mm length interval were mature. Sex ratios were variable.Higher catch-per-unit-effort (cpe) was related to warmer water temperatures to the thermocline level. When water temperatures were mixed resulting in low inshore temperatures, cpe values were lower.There existed a great deal of sample variability within and between gear types as a result of seasonal population availability, gear characteristics, and non-random distribution of the population.Trawling, although more efficient than gill netting at sampling total numbers and widest range of lengths, was selective for smaller fish, and gill netting was selective for larger fish. Depth (from 5 m to 18.3 m) and particular gill net methods employed had little effect upon the sizes and length-percent frequency distribution sampled.Great differences between percentage age compositions compiled from trawl and gill net catches reflected the size selectivity of the gears. These results raised questions concerning the validity of management techniques involving percentage age composition and cpe index values to determine relative year class strength.The age groups I and II were represented by the proportion 8:2 (1:11) in the trawl catch which adequately sampled the sizes including the age I and II fish. Further study would be needed to determine the validity and usefulness to management considerations of this method of relative year class strength determinations. Recommendations for additional study were made.

The potential near-shore forage fish populations were investigated by bottom trawling during the months of June through August of 1984-86 in Lake Michigan, near Michigan City, Indiana. Data were collected on the six moat common species including: yellow perch (Perca flavescens); alewife (Aloes pseudoharenqus); rainbow smelt(Osmerus mordax); bloater (Coreaonus,hovi); spottail shiner (Notroois hudsonius); and trout-perch (Perconsis omiscomavcus). Results of the 1984-86 sampling period were compared with data for 1973 in an attempt to document changes in population density, species composition, annual catch, seasonal abundance, and population structure.The total trawl catch for all species increased nearly seven-fold since 1973 even though sample methods and collection effort were unchanged. A dramatic increase in yellow perch abundance was primarily responsible for the elevated levels sampled for all species from 1984-86.The species composition of the catch shifted since 1973. In 1973, spottail shiners were the most abundant species (41%) and trout-perch and alewives were the next most abundant species comprising 20% and 17% of the catch, respectively. Yellow perch, which comprised only 12% of the catch in 1973, increased to 81% of the catch in 1986. Bloater also showed a great increase in relative importance since 1973 when they were rare in the catch. Other species, including alewife, were relatively minor components of the total catch each year from 1984-86. The trawl catch results revealed that alewife and trout-perch declined 71% and 87%, respectively, comparing 1973 with 1984-86. During the same period, yellow perch increased 72-fold and bloater over 3000-fold. By comparison, the spottail shiner population was stable with no long-term changes, but rainbow smelt populations fluctuated widely.Seasonal abundance of adult fish (age I or older) generally decreased from June to August for each fish species and year sampled with the exception of yellow perch which peaked in July of 1973, and in August of 1985-86. Young-of-the-year fish were generally captured in late July and August.Population structure changes were evaluated by examining pooled length-frequency data. Yellow perch length-frequency distributions indicated that strong year classes were produced every year from 1983 to 1986. The 1985 year class was well over twice as large as any of the other years sampled. Spottail shiner and rainbow smelt length-frequency distributions remained approximately stable since 1973, while alewife length-frequency distributions fluctuated annually. Capture of bloaters was almost entirely limited to June, and consisted primarily of age I+ fish in 1984-86.These results reveal significant changes have occurred in the potential near-shore forage fish populations in Indiana waters of Lake Michigan since the early 1970's. Although several factors may be involved in the shifts noted, the major contributing factor is likely predator-prey interactions as a result of salmonid predator density.

The purpose of the study was to examine how forest harvesting affects the accumulation of carbon dioxide (CO2) and methane (CH4) under the ice-cover. Dissolved organic carbon (DOC) was hypothesized to increases post-harvest, this supplementation would in turn lead to an increased accumulation of CO2 and CH4 under the ice-cover. Four small boreal lakes, (two treatment lakes, two reference lakes) were sampled once a year during winter, under a three-year period (2012-2014). The sampling was performed using a headspace equilibration technique. During the three study years (2012-2014), the CO2 concentration increased in both the reference lakes and the harvested lakes (percentage increase; 18 % and 89 % respectively). The mean CH4-concentration in the reference lakes increased during the years 2012-2014, (2, 6, 7.5 μM). While the concentrations in the harvested lakes showed a slightly different pattern, with a peak during year 2013 which latter decreased until year 2014, (6, 12.5, 8.5 μM). The result of this study suggests that harvest in the catchment area increases the accumulation of CO2 and possible CH4 under the ice. Inflow of supersaturated surface water was found to be a more important source to the increased accumulation under ice than DOC, contradicting the previous hypothesis that DOC would be a more important factor controlling the CO2 and CH4 production. Moreover this study indicates that the dimension of the edge-zone left in connection to the inlets can be of crucial importance, possible reducing the amount of supersaturated surface water reaching the lakes.

Nutrients in the sediments of Lake Manitoba’s south basin are resuspended regularly due to its shallow, polymictic nature. In 2009 short sediment core samples were used to determine an internal available nutrient load from sediment of 17,533 tonnes total nitrogen (TN) and 167 tonnes total phosphorous (TP). Water samples were collected at the Whitemud River and Assiniboine River Diversion (ARD) to determine the N and P input to the lake, resulting in an estimate of a total point source input of 3,547 tonnes of TN and 1,130 tonnes of TP. Open water samples were collected to determine a suspended content of 9.2 tonnes of TN /km2 or and 1.7 tonnes of TP/km2. The ARD is the largest contributor of TP to the south basin. The internal sediment pool is a significant source of TN, and when the ARD does not operate, the largest input of TP to the south basin.

The rocks studied in this thesis have been the subject of considerable discussion as to their original nature. J. D. Bateman of the Geological Survey of Canada considers that they are of igneous origin whereas others believe that they are metamorphosed sediments. It was thought that a petrographical study might provide some information that would help to decide the problem and it was with this object in view that this study was undertaken. Cree Lake, in the vicinity of which the rocks occur, is situated 2 miles North of the Sherritt-Gordon Mine, Manitoba, which lies about 20 miles east of the Manitoba-Saskatchewan border and 120 miles northwest of the north end of L. Winnipeg. The Sherritt-Gordon copper-zinc ore deposit is a very remarkable deposit in that it is a tabular body with a total outcrop length of 16,000 feet and an average width of 15 feet, thus being one of the longest exposed ore bodies in the world. The rocks in question outcrop around Found Lake which lies very close to and just to the southeast of Cree Lake (see Map 44-4) and fall into two groups; firstly, thos that outcrop south of Found Lake in an area which was mapped by J. D. Bateman as an oval body of oligoclase granite (Map 44-4, No. 12) about one mile long and 1/4 mile wide and secondly, those that outcrop as three smaller masses north of Found Lake but enclosed by the arms of Cree Lake and mapped as anorthositic gabbro (Map 44-4, No. 11). [...]

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Human society has influenced the environment for at least the last 15000 years but, since the Industrial Revolution, the resultant environmental impacts have been widely used in many studies for reconstructing this impact over medium timescales (tens to hundreds of years). Few long-term studies of hydrological change exist and sediments are useful as surrogates for direct monitoring since they are sensitive to change within the catchment. This study uses the properties of urban lake sediments in order to reconstruct environment pollution history. The two principal objectives of this study were the reconstruction of historical atmospheric, point source and diffuse heavy metal pollution in an urban environment and the evaluation of the lake-sediment record as a source of proxy hydrological data over the last 100-150 years. A paired lake-catchment study was undertaken by comparing the records contained in a closed and an open lake. The closed lake (Swanswell Pool) is situated in the centre of the city of Coventry where the main source of pollution is atmospheric. This site provides a contrast to an open basin (Wyken Pool) with a multi-source catchment in addition to atmospheric influx. Trends in urban lake sediment cores indicate increasing heavy metal concentrations upcore, with cultural enrichment factors for individual heavy metals of between 55.4 and 2.6. Storage of heavy metals in the catchment of the closed basin were significant, although it was found that up to 85% of the Zn and 90% of the Pb were actually stored in the lake sediments. Catchment sources contributed up to 5 times more than the atmosphere in the Wyken Slough catchment. Heavy metals budgets were calculated, and these showed that loadings of metals have increased by up to 7.5 times between 1850 and the present day. Sequential digestion of the lake sediments at both sites showed that the important fractions containing heavy metals were Fe and Mn oxides and organic matter. The heavy metals associated with these fractions could be remobilised with changing environmental conditions, but an analysis of contemporary water quality indicated that, at present, suitable Eh and pH conditions for remobilisation did not occur. It was concluded that these urban lakes do preserve the heavy metals record and can provide surrogate data on medium-term environmental change. However, the complex mixture of materials associated with urban sedimentation resulted in a lack of correlation between heavy metals and mineral magnetic properties in either lake, and in the catchment of Wyken Slough. Hence mineral magnetic properties of sediments in urban catchments do not appear to be a suitable surrogate for heavy metals analysis. Urban lakes appear to provide a much-neglected opportunity for palaeolimnological reconstruction over a period when little directly monitored data exists.

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