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Full-Text Articles in Life Sciences
Green And Choking: Exploring The Dynamics Of Seasonal Productivity And Hypoxia In A Great Lakes Area Of Concern And Habitat Blueprint Estuary Using Time-Series Measurements, Anthony D. Weinke
Masters Theses
Although hypoxia (dissolved oxygen <4 mg L-1) in the bottom waters of lakes, reservoirs, and estuaries may be a natural product of stratification in eutrophic or mesotrophic systems, there is increasing concern because the occurrence of hypoxia is spreading in many areas where hypoxia did not previously exist. Part of this new knowledge can be attributed to time-series data from buoy observatories that monitor systems in good weather and in bad, and allowing insight into the inner workings of a lake where sampling only a few times per year would not. This study made use of a five-year time-series of meteorological and water quality data in order to examine the effect of episodic wind-events on stratification and hypoxia within Muskegon Lake, Michigan, as well as performing bi-weekly lake-wide monitoring to evaluate the effects of stratification, hypoxia, and wind-events on the lake. In the wind-event portion of the study, we found that events where wind speeds were above average for an extended period of time occurred fairly frequently on the lake, but that thermal stratification allowed only the strongest events to significantly mix the water column at the buoy location a few times per year. This provided infrequent relief of hypoxia in the bottom waters. The second portion of the study found extensive effects on the water quality and biology in the bottom of the lake due to hypoxia such as increased phosphorus concentrations, enhanced phycocyanin following a strong windevent, and decreased fish abundance, richness, and size. We also found that hypoxia occurred lake-wide at all four sample locations, but was most stable at the deepest point in the lake that was least influenced by wind-events. It is possible that the combination of hypoxia and strong episodic wind-events leads to entrainment of phosphorus-rich waters to the surface initiating or continuing an algal bloom. Hypoxia and wind-event mediated internal loading of phosphorus could be a positive feedback loop for cyanobacterial blooms and hypoxia in Muskegon Lake.
The Effect Of Seasonal Fish Migration On Energy Budgets In Two Coastal Michigan Streams, Emily M. Dean
The Effect Of Seasonal Fish Migration On Energy Budgets In Two Coastal Michigan Streams, Emily M. Dean
Masters Theses
Migratory fish are known to seasonally enter coastal stream systems but the magnitude of the effects these migrations have on stream energy budgets is not fully understood. The Laurentian Great Lakes have several introduced and native adfluvial fish, where only a few studies have investigated the impacts of their migration on energy budgets in Michigan coastal streams. We quantified the contribution of energy from Chinook salmon (Oncorhynchus tshawytscha) muscle and eggs, steelhead (Oncorhynchus mykiss) eggs, and larval white suckers (Catostomus commersonii) to coastal stream energy budgets. Energy densities and energy delivered to streams were estimated using bomb calorimetry and annual …