Location

Diamond 122

Start Date

1-5-2014 1:00 PM

End Date

1-5-2014 4:00 PM

Project Type

Presentation

Description

The Messalonskee Stream in central Maine has five hydroelectric dams on 16.6km. Each dam drastically changes the flow regime of the stream, dividing it into segments with different patterns of sediment settling and organic matter retention. We investigated how these disruptions impact nitrogen cycling, specifically nitrification rates above and below each dam. We expected higher nitrification rates above the dams, where levels of organic matter are higher, and lower rates below the dam where scouring removes organic matter and fine sediment from the streambed. We measured sediment nitrification rates with a nitrapyrin-inhibition assay and potential drivers of nitrification including sediment organic matter and pore water ammonia (NH4+) above and below each dam. Nitrification rates ranged from below detection to 552 μg NH4+ gAFDM-1 day-1 with no consistent pattern between above and below sites. Variation among the five dam sites is due different distributions of sediment above and below the dams and widely varying flow velocity.

Faculty Sponsor

Russ Cole

Sponsoring Department

Colby College. Environmental Studies Program

CLAS Field of Study

Interdisciplinary Studies

Event Website

http://www.colby.edu/clas

ID

659

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May 1st, 1:00 PM May 1st, 4:00 PM

The Impact of Dams on Nitrogen Cycling in the Messalonskee Stream

Diamond 122

The Messalonskee Stream in central Maine has five hydroelectric dams on 16.6km. Each dam drastically changes the flow regime of the stream, dividing it into segments with different patterns of sediment settling and organic matter retention. We investigated how these disruptions impact nitrogen cycling, specifically nitrification rates above and below each dam. We expected higher nitrification rates above the dams, where levels of organic matter are higher, and lower rates below the dam where scouring removes organic matter and fine sediment from the streambed. We measured sediment nitrification rates with a nitrapyrin-inhibition assay and potential drivers of nitrification including sediment organic matter and pore water ammonia (NH4+) above and below each dam. Nitrification rates ranged from below detection to 552 μg NH4+ gAFDM-1 day-1 with no consistent pattern between above and below sites. Variation among the five dam sites is due different distributions of sediment above and below the dams and widely varying flow velocity.

http://digitalcommons.colby.edu/clas/2014/program/351