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The dislodged periphyton will be rinsed into a labeled whirlpack, covered in foil, and <br />stored on ice. The longest axis of each rock will be measured. <br />Subtask 2.2 - Level 1 tech - periphyton sampling <br />Assistance for field periphyton sampling and lab analysis <br />Subtask 2.3 - Lab Analysis <br />Chlorophyll a is a commonly used index of algal biomass. Within 24 hours of cotlection, <br />the periphyton samples will be filtered on glass fiber filters and stored frozen. <br />Periphyton that consists of clumps or filaments wili be blended prior to filtration. <br />Within 30 days of collection, the frozen periphyton samples will be analyzed for <br />chlorophyll cr. Chtorophyll in the periphyton on filters will be extracted with ethanol <br />for 20 to 24 hours in the dark. Chlorophyll a will be determined by the non- <br />acidification method using a Turner Trilogy Fluorometer. <br />Ash-free dry mass (AFDM} is a measurement of the organic contents of the periphyton. <br />AFDM includes algat as well as non-algal components. Within 24 hours of collection, the <br />periphyton samples will be filtered on ashed and pre-weighed glass fiber filters and <br />stored frozen. Periphyton that consists of clumps or filaments will be blended prior to <br />filtration. Within 14 days of collection, the frozen filter samples will be dried at 60°C. <br />The dried filter samples wilt be weighed, then ashed at 550°C for 4 hours. The ashed <br />filter sampies will be cooled in a desiccator and then re-weighed. AFDM wilt be <br />determined by the difference in mass between dry and ashed samples. <br />Subtask 2.4 - Periphyton nitrogen 15 isotopic signature <br />The nitrogen 15 isotopic signature is a measure of the amount of heavy nitrogen 15 <br />compared to the more common isotope nitrogen 14. It is reported as the delta nitrogen <br />15 (aN15). Different sources of nitrogen often have distinctive isotope signatures that <br />can provide a better understanding of the system than simply measuring <br />concentrations of nitrogen. An increase in b15N usually signifies an increasing <br />anthropogenic source. For example, in Toda et at. (2002) b15N in periphyton increased <br />with increasing distance from headwaters. The increase in periphyton d15N atso <br />correlated with increasing re:lative contribution of nitrate from sewage and animal <br />waste. A similar relationship was found between increasing agricultural use of <br />watersheds and increasing b15N by Luecke and Messner (2005). Nitrate from human <br />and animal wastes generally has a higher d15N than nitrate derived soil nitrogen or <br />from synthetic fertilizers, however. In the 2006 nutrient source identification study <br />conducted on the New Mexico portion of the Animas River, a striking increase in a15N <br />occurred downstream of the Aztec Wastewater Treatment Plant and continued for <br />several miles through the more urbanized lower portion of the river {K. Nydick, <br />unpublished data). <br />Within 24 hours of cotlection, the periphyton samples will be filtered on ashed glass <br />fiber filters and stored frozen. Periphyton that consists of clumps or filaments will be <br />blended prior to filtration. Within 14 days of collection, the frozen filter samples will <br />be dried at 60 The filters are then encapsulated in tin capsules. a15N is determined <br />by mass spectrometry at the University of California-Davis or comparable laboratory. <br />Subtask 2.5 - Data Anatysis &t Reporting on periphyton <br />This information will be compited, summarized, and presented in both table and map <br />