Tripton,transparency and light penetration in seven New York reservoirs

Temporal patterns and inter-system differences in the attenuation coefficient for scalar irradiance (K_s), Secchi disc transparency (SD), several measures of tripton, and chlorophyll a (Chl) are documented for the lacustrine zones of seven reservoirs (nine distinct basins) in New York (U.S.A.), based on a single year of comprehensive measurements. Analyses of these data and historic (12 years) observations of SD and Chl, including application of empirical and deterministic modeling frameworks, demonstrate that inorganic tripton is the primary attenuating constituent responsible for the substantial differences in K_s and SD among these basins, and the major temporal variations observed in these optical characteristics in most of the study basins. These inorganic particles, of terrigenous origins, are supplied directly to the water column of these basins in inflows, particularly during runoff events, and through the sediment resuspension process. Comparison of the measures of tripton indicates electron-microscopy-based measurements performed somewhat better than gravimetric analyses in explaining the variations in K_s and SD in the lower concentration systems. Increases in average SD values by factors of 2–5, compared to prevailing values, are predicted for the study basins with the deterministic model for the case of no tripton.