Influence of light and algae on nutrient transformations at the sediment-water interface of an agricultural stream

The sediment-water interface is an active biogeochemical zone within streams, where solutes come in contact with mineral surfaces, biota, and reducing conditions. Here, we sought to examine the influence of light, the sediment water interface, and algae on dissolved organic carbon (DOC), nitrogen, and phosphorus within Maple Creek, an agriculturally impacted stream located in Fremont, Nebraska. Simultaneous continuous injection experiments into replicate open- and closed-bottom chambers were used to control the hydrologic residence time. A bromide tracer was injected, and samples were taken for nutrient analysis in the surface and subsurface water at depths up to 8 cm. Dissolved oxygen (DO) and temperature were recorded in order to monitor biotic production. Experiments were conducted over 10 hours, encompassing both light and dark conditions. Results show a strong biotic influence at the sediment-water interface causing nutrient uptake and changes in carbon quality. Changes are especially pronounced during peak photosynthesis hours. The open-bottom mesocosms consistently showed removal of N and P from the surface water to the subsurface. An increase in DOC flux was observed in the open-bottom mesocosms and the organic matter pool exhibited evidence of microbial reduction. The closed-bottom mesocosm showed NH?⁺ increased likely due to photochemical oxidation. These results show the importance of promoting exchange through the subsurface and across the sediment-water interface due to the positive impact it has on nutrient retention.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Biological Systems Engineering

Department dc:contributor.department

Biological Systems Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2011

Author dc:creator

• Pinney, Jenae Elizabeth

Chair dc:contributor.committeechair

• Scott, Durelle T.

Committee members dc:contributor.committeemember

• Gallagher, Daniel L.
• Hession, W. Cully

• DOM
• Ammonium
• Phosphorus
• Nitrate
• Nutrient Retention

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Dc Identifier Other

etd-06192011-172727

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/76801