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Declines in the abundance of submersed aquatic vegetation (SAV) in Florida’s spring systems are attributed, in large part, to the proliferation of nuisance algae. Macroalgal mats and increased periphyton burdens on the leaves of native vascular plants are particularly problematic as these algae intercept incident light necessary for photosynthesis and maintenance of SAV beds that provide important ecosystem services. In the spring-fed systems along the west coast of peninsular Florida, documented increases in periphyton on SAV are temporally concordant with losses of important plant species such as Vallisneria americana. This observation is suggestive of a cause and effect relationship, though the direct effects of periphyton on light reduction and performance of SAV in these systems have not been investigated. Toward this end, we used field collected data to model the relationship between periphyton biomass on Vallisneria americana leaves and light transmission. Our results suggest that the PAR attenuation as a function of epiphytes biomass can be well described by a negative hyperbolic equation, with a rapid reduction in light transmission associated with an increased epiphytic load. Based on known light requirements of SAV we will use the modeled data to make predictions about periphyton thresholds and plant performance. The ultimate aim is to provide water resource managers with an objective tool to assess the vulnerability of SAV to the negative impacts of increased periphyton loads. |