Factors affecting the maximum depth of colonization by submersed macrophytes in Florida lakes

Abstract In 32 Florida lakes, Secchi depth (SD), light attenuation coefficient measured with a light meter, plant and sediment type, and slope were examined with respect to the maximum depth of plant colonization (MDC). The MDC was shown to be significantly related to light through measurements taken by SD (R2 = 0.46; p < 0.05) and a light meter (R2 = 0.41; p < 0.05). While both light measurements can be used to estimate MDC, SD accounted for more variance in MDC than light attenuation coefficients. Plant type, sediment type and slope did not account for more variance in MDC than light measurements for these Florida lakes. Additional unpublished data from 187 Florida Lakes (Florida LAKEWATCH, 279 lake-years of data) also showed a significant positive relationship between SD and MDC (R2 = 0.68; p < 0.05). The best fit MDC-SD regression line in meters was: log (MDC) = 0.66 log (SD) + 0.31. A maximum MDC line relating MDC to SD in meters was also calculated and was found to be equal to: log (max MDC) = 0.53 log (SD) + 0.59. The maximum MDC line describes light limitation when the MDC response falls on or near the response curve, and when MDC values fall below the line, some other factor likely limits colonization of macrophytes.