Title

The Effects of Decomposing Macrophytes, Aeration, and Temperature on Water Quality Measurements in Microcosms with Sediment and Water from Lake Whatcom, Wahington

Date of Award

1996

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Science

First Advisor

Robin A. Matthews

Second Advisor

Thomas A. Storch

Third Advisor

Emily R. Peele

Abstract

Lake Whatcom sediment and water were used to study decomposition processes through the effects of temperature, aeration, and decaying macrophytes on water quality and microbial respiration using laboratory microcosms during a 43-day experiment. Thirty-two, 900 mL glass jars containing sediment and water from Lake Whatcom were placed randomly into eight treatment groups. Treatments were defined by temperature, presence or absence of aeration, and presence or absence of decaying macrophytes. The microcosms were sampled immediately prior to initiation of treatment, one and three days after treatment and then weekly over a six-week period.

Water samples were collected 3 cm above the sediment surface through silicon rubber ports in the top of the microcosms using syringes and 20 gauge needles. Micro-volume analysis techniques were developed and employed to determine the concentrations of dissolved oxygen, ammonia, nitrogen, and phosphorus as well as to compare the rates of microbial respiration through INT reduction in each microcosm.

The data were analyzed using parametric and nonparametric analyses of variance, graphic, and cluster analysis techniques. Of the three factors, the presence of decaying macrophytes had the greatest impact on water quality. Nutrient concentrations and microbial respiration were higher in the microcosms containing plant material. Aeration also affected water quality by lowering nutrient concentrations and increasing dissolved oxygen levels within the microcosms. Temperature did not significantly affect dissolved nutrient concentration, but did influence respiratory activity and percent weight loss of the macrophytes in the leaf packs.

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