Sediment and light requirements of four species of native submerged macrophytes occurring in Florida lakes

The purpose of this research was to investigate sediment and light growth requirements, two key factors in the establishment of native submersed macrophytes in shallow eutrophic Florida lakes. The study plants were Najas guadelupensis, Potamogeton illinoensis, Vallisneria americana and Chara sp., all Florida native submerged species commonly occurring state-wide. The selected species exhibited a variety of morphometries and life histories. The results will be of value to lake managers for use in the development of a more systematic approach to the establishment of diverse communities of desirable native species.; This study was divided into two main objectives. In Objective 1, the study species were cultured outdoors in growth tanks in south Florida for three separate 9-week culture periods on inorganic sediments collected three different times from four littoral stations in Lake Hollingsworth and on artificial control sediments. The results suggested that the inorganic sediments collected from Lake Hollingsworth had sufficient nutrient levels to support the growth of the study species. The findings further indicated that late spring was the ideal time to introduce plant propagules into restored systems. Submerged macrophyte growth in this study appeared to be most significantly affected by a combination of factors including light, water temperature and sediment nutrients.; In Objective 2, shade cloth was used to establish four light treatment groups in an outdoor growth tank in south Florida. The light requirements of mature plants and vegetative propagules were investigated during three culture periods for each group. The photosynthetic photon flux density (PPFD) for no net growth of mature plants ranged from 14 to 416 mumol photons s -1 m-2 (2 to 50% incident irradiance). The PPFD for no net growth of propagules ranged from 25 to 183 mumol photons s-1 m-2 (3 to 22% incident irradiance). V. americana exhibited the lowest minimum light requirement for growth, 2 to 18% incident irradiance. Propagules of P. illinoensis and V. americana had higher light requirements as compared with mature plants. Both mature and propagule plants exhibited the greatest capability for growth at low light levels during the summer culture periods.