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Lake Urmia (LU), which once had been the second largest hypersaline lake in the world, and greatest in the Middle East, has undergone severe environmental changes during recent years that have led to widespread desiccation. These changes have converted the lakebed into a significant Aeolian mineral source, which promotes aerosol plumes that can seriously impact downwind regions. A question remains as to how significant emissions are from LU as compared to others impacting the West and East Azarbaijan provinces encompassing LU. This study uses daily Aerosol Optical Depth (AOD) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) between 2001 and 2015 to show that AOD levels are significantly larger in the latter half of the study period (2008-2015) with AOD values in the West consistently being lower but approaching those of the East with time owing to a combination of increasing emissions from the West province and neighboring areas. While the interannual AOD profile over Azarbaijan resembles that of Iraq owing to transported dust, signatures of the local impact of increasing emissions is evident over the 15-year time period, especially in the months outside of the peak dust season (January, February and October) and on the immediate periphery of LU. Consequently, the spatial profile of AOD over Azarbaijan is not uniform but with distinct hot spot. The onset of the spring AOD ramp-up over Azarbaijan is shown to have started earlier (in February) when comparing 2009-2015 versus earlier years. Correlative analysis confirms that AOD is related to factors promoting dust emissions but also reveals that smoke contributes to AOD over Azarbaijan during the summer months.

Lake Victoria (LV), is the largest tropical fresh water lake. It is however facing a myriad of challenges like eutrophication, introducing species, mass extinction and climate change. Eutrophication has mostly been seen as a result of non-point pollution from upstream agricultural areas. However, studies have found that atmospheric deposition could perhaps be the greatest cause of nutrient loading in the lake. Our study looked at black carbon as one of the factors favoring eutrophication in LV. Black carbon is a product of incomplete combustion of biomass or fossil fuel. Biomass burning is prevalent in many areas of Africa and our results have shown a great spatial and temporal variability in its concentration in sediments. The sedimentation rates calculated after analyzing 210Pb activity were 0.87, 0.53 and 0.35 g cm-2 yr-1 while the average black carbon concentrations were 4.6, 2.1 and 6.9 mg g-1 for Siaya, Kisumu and Busia, respectively. These results provided valuable information when compared to past historical events in the Lake region especially eutrophication. The study also found that soot BC has been increasing in the past 100 years suggesting the input from fossil fuels. This study elucidates the complexity of drivers of eutrophication in Lake Victoria. Nitrogen and Phosphorous from the upstream agricultural sites has long been seen as the main cause of eutrophication. Through this study we find that soot deposition in the lake coincides with the period of increased primary productivity. The Total Organic Carbon and Total Nitrogen were also analyzed and have shown increased remarkable increase with time. All these geochemical variables are a testament to the increased role of human activities on the lake’s productivity. While other studies on soot in marine environments have associated bacterial growth to nutrients attached to soot black carbon. We correlate the concentration of soot in Lake Victoria basin to blooming of cyanobacteria.

The effects of thermal discharges on the density, distribution, production, and drift of benthic organisms were studied at North Lake reservoir.

A total of 192 largemouth bass were caught at Lake Ray Roberts, Texas (1995) to investigate five controversial bass angling techniques relative to hooking mortality. The bait types were Texas-rigged scented and non-scented plastic worms, Carolina-rigged scented and non-scented plastic worms, and live golden shiners. Overall hooking mortality was 21.87% and mortality was dependent upon bait type. Highest mortality resulted from the Texas-rigged scented lures, while the lowest mortality was generated by live golden shiners. A creel survey indicated that few anglers were having success with the investigated baits. Factors that had a confirmed effect on hooking mortality were hooking location and water temperature. Hooking mortality was not excessive compared to other similar studies.

Lake trout populations were extirpated from the lower four Great Lakes by 1960 and from Lake Champlain by 1900. The decline of lake trout populations fueled a wave of restoration-based research that spanned the Great Lakes and filled in many of the gaps in our knowledge of lake trout behavior and ecology. However, remarkably little is known about lake trout spawning behavior, even less about sex-specific differences in spawning site use. Lake trout use specific spawning sites, and may return to the same site year after year. More males are caught on spawning sites than females and are present at spawning sites earlier in the spawning season. The focus of this project is to describe the spawning movements of male and female lake trout within and among spawning seasons and spawning sites. I used acoustic telemetry in Lake Champlain to look at specific questions of spawning site fidelity and whether or not there were differences in male and female movements. I hypothesized that males show site fidelity and remain at a preferred site during the spawning season, whereas females 'sample' multiple spawning reefs to maximize their reproductive success. I established an acoustic telemetry array of ten acoustic receivers placed over eight spawning sites and implanted acoustic transmitters (tags) in 44 male and 48 female lake trout over two years. During two spawning seasons, males spent more time on spawning sites than females. Both male and female lake trout that were active on monitored sites during the spawning season selected a single preferred site. There was no difference in the number of sites visited by males and females. Of the lake trout detected during both spawning seasons, most returned to their capture site in the subsequent spawning season, showing evidence of site fidelity. I also developed a binomial rolling residence test (BRR test) to improve the current method of assessing the duration of a fish's residence at a single receiver. I measured daily detection probabilities (DP) at a given distance from a receiver site. The BRR test evaluates a tag's residence every minute by moving a one-hour time window centered on time t across the duration of the data. The daily DPs are incorporated into a binomial test of the null hypothesis that a fish is not within x meters of the receiver at time t. I performed a 48-hour stationary residence test using two onsite tags and two offsite tags and compared the performance of the BRR test to three residence assessment methods found in the literature. The results showed that the BRR test performs better than all of the time-threshold residency evaluations in our 48-hour stationary residence test. We suggest that this method has the potential to advance the field of telemetry by improving the interpretation of telemetry data.

This study focused on the effectiveness of integrating traditional plant community analyses with landscape ecological analyses based on remotely sensed data. A temporal analysis of plant community diversity was conducted for major plant communities of the Ray Roberts Lake area using transect monitoring data collected between 1987 and 1997. Landscape analyses were performed with FRAGSTATS*ARC using classified SPOT satellite imagery for 1987 and 1997. Although the methodology developed in this work was exploratory, it was found that characterizing the dynamics of major plant communities in the study area produced a more effective and insightful analysis of Ray Roberts Lake area landscape dynamics.

1971

The burbot (Lota lota, Linnaeus 1758) is a benthic and predatory cod-relative that only occurs in fresh- and brackish water around the northern hemisphere. It has long been a common catch in Swedish lakes and rivers, but the species has seen a decline by over 20% since the mid 1980’s. This led to the burbot being red listed as nearly threatened (NT) in 2010. A decline of this magnitude might be alarming, the burbot is mostly declining in smaller lakes and rivers in southern Sweden and it’s still showing significant numbers in larger lakes such as Vänern – Sweden’s largest lake. Although recent monitoring of the burbot shows an erratic population that’s declining over several years, only to bounce back a couple of years later. This peculiar pattern made me interested in the historical aspects of the burbot population and its potential influencing factors in lake Vänern. In this study I compare data from the oldest known gillnet sampling done in lake Vänern that also contain burbot with more contemporary samplings (2010, 2011, 2012, 2015 and 2018). I manage to show that the number of large burbot caught were in line later years, but I also manage to show a decline by over 80% in the number of middle-sized burbot between 1973 and the later years. Furthermore, I produced results showing that the burbot seems to be aggregating deeper in later years compared to 1973. Finally, I correlate the population changes to environmental data and get statistically significant correlations showing that the declining numbers of fish and their decent into deeper areas of the lake are connected to the rising water temperatures. This result is in line with ecological studies that describes the burbot as cold-water dependent with a preferred temperature of around 10 – 14 °C. This study suggests that the burbot is affected by rising average water temperatures caused by climate change.