Humboldt Journal of Microbiology


Wastewater management is an essential component of modern society that is necessary for reducing human environmental impact, particularly in aquatic ecosystems. In Humboldt County, California, the Arcata Wastewater Treatment Plant and Wildlife Sanctuary (Arcata Marsh) is a model for other wastewater treatment plants worldwide to treat waste naturally, reducing the use of chemicals. This wastewater is then discharged into the Humboldt Bay. It is well known how treatment helps remove harmful waste materials, but it has not been investigated how phytoplankton diversity is affected before, during, and after treatment. Phytoplankton are primary producers that are responsible for carbon sequestration and production of oxygen, and are an essential food source for higher trophic-level organisms. When nutrient levels are high, such as in human waste water, it can lead to single species proliferation, thus resulting in lower diversity and higher abundance of other species in the community. This can have negative consequences on the higher trophic levels that consume them and also creates “dead-zones'' where aerobic species are unable to survive. In this study, pre-treatment water and post-treatment water were sampled and observed for diversity and abundance of diatoms, a quantifiable subphylum of phytoplankton. It was hypothesized that successful treatment would result in higher diversity of diatoms in post-treatment waters than that of pretreatment waters. This study found 30 morphologies across all sample sites, with abundance of 2-4 species being significantly greater in pre-treatment ponds than post-treatment ponds. There were no significant trends in diversity across the ponds.

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