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Importance of new versus recycled nutrients in meeting algal growth demands.
Shostell, Joseph1, Bukaveckas, Paul1, 1
ABSTRACT- Volumetric loading of P and N from gizzard shad, zooplankton, and a primary inflow were compared to algal nutrient demand in a Kentucky reservoir. Average nutrient loading by the primary inflow was greater than that of gizzard shad or zooplankton with DP inputs from the catchment of .036 mol l-1 day-1, while inputs from fish and zooplankton were .016 and .030 mol l-1 day-1. Average DIN inputs from the catchment, gizzard shad and zooplankton were .447, .115, and .353 umol l-1 day-1. Algal nutrient demands estimated from primary production and Redfield ratios were .06 P umol l-1 day-1 and .95 umol DIN l-1 day-1. Tributary inputs accounted for 60% and 47% of algal P and N demand respectively. Tributary inputs varied widely over a 10-year period (26 fold for P and 61 fold for N) compared to gizzard shad and zooplankton changes of around 2-fold among experiments conducted over a 2-year period. Volumetric loading of nutrients by gizzard shad at times exceeded that by tributaries for P or were 54% for N. On average, gizzard shad accounted for 26% and 12% of algal phosphorus and nitrogen demand.
KEY WORDS: gizzard shad, nutrients, tributary, zooplankton