Exploring alternative controls of algal proliferation in Florida's springs

Florida’s spring systems are changing dramatically, however the ecological drivers of these changes are not fully understood. Nuisance algal overgrowth is evident in many springs, shifting the ecosystem from states dominated by submerged aquatic vegetation, to domination by benthic algae.  Algal overgrowth can be detrimental for human health, recreation, and wildlife, but attempts at management may not be effective without understanding the system’s drivers. Current scientific thought proposes multi-causal drivers of ecosystems, yet questions remain about the weight of various factors. While attention has focused on nitrogen enrichment as the cause of algal overgrowth, studies within Florida’s springs have been equivocal.

New multivariate analyses are suggestive of a plausible alternative hypothesis, namely that decreasing dissolved oxygen (DO) levels in water issuing from spring boils leads to grazer exclusion and subsequent release of algal control. We postulate that this recent DO decrease may be due to the prevalence of older aquifer water contributing more to spring flows, due to interactions of climatic variation and consumptive use. The DO-grazer hypothesis is being initially tested through surveys of grazer and algal biomass along chemical and seasonal gradients within springs. We present the multivariate analyses, preliminary survey results, and plans for future in-situ experiments.