Tape grass life history metrics associated with environmental variables in a controlled estuary

Twenty samples of tape grass were removed from four locations along a salinity gradient in the Caloosahatchee River in Lee County, Florida each month in 1998. Examination of the environmental, independent variables indicates a strong seasonal cycle for temperature and a trend toward increasing chlorophyll levels during the year. Dependent response variables recorded for tape grass also indicated a seasonal pattern that mimicked the temperature cycle. There was a time lag in maximal life history attributes. Number of shoots per sample, number of blades per sample, and number of blades per shoot had highest values during the warmer months, i.e., May-August. Blade length, blade width, and biomass were higher during the later part of the summer and early fall. Reproductive attributes of the plants, i.e., number of male and female flowers, were highest during the fall. The salinity gradient that was part of the study design was weak and accounted for only a small part of the variation observed between locations along the river. Typically, the end of the year parameter levels were higher than the beginning of the parameter levels for all response variables among plants. It is suspected that this is due to the inordinately heavy rains during early 1998 that led to lower salinities at all locations. These normally freshwater plants were apparently less stressed because of the lower salinity conditions in the estuary. This situation may have provided a "boost" to their growth that helped expand the extent, size, and-fitness of tape grass within the estuarine system. A paradox was revealed in that higher plant growth parameters were recorded among plants from the higher salinity portions of the river. During 1998, salinities were low at the most seaward location, but water clarity was greater, thus providing conditions that may have facilitated growth of this normally freshwater plant in an estuarine ecosystem.