Summary and Synthesis of the Available Literature on the Effects of Nutrients on Spring Organisms and Systems

Executive Summary This summary of the state of the knowledge related to nutrient effects on spring ecosystems and biota represents a synthesis of the most important findings from the literature. The report was commissioned by the Springs Initiative of the Florida Department of Environmental Protection (DEP) to review the pertinent literature related to nutrient effects on spring ecosystems and biota. To address the complexity of spring ecosystems, this literature synthesis was prepared by a diverse team of spring researchers at the DEP's mandate was threefold: 1) to prepare a review of what is known about the interactions between nutrients and springs, 2) to identify what information gaps exist that inject substantial uncertainty for springs restoration and management, and 3) make recommendations for public policy and research to address these gaps. The following summary draws the most important highlights from each chapter according to this mandate. This chapter focuses on describing the abiotic and biotic components of spring and spring run ecosystems, their forcing functions and inputs, and the known ecology of these unique aquatic ecosystems. From this review of the existing literature on spring ecosystems there are several conclusions that can be drawn: • Springs and spring runs represent a unique class of aquatic ecosystems typified by high water clarity, relatively constant water temperature and chemical conditions, and complex biotic interactions. • In their natural state, springs persist in a quasi environmental steady-state and due to this stability have developed complex biological systems that are highly efficient at converting solar energy into useful productive work. • During the past century humans have been exerting an increasing variety of external and internal stresses on spring ecosystems in Florida, the most pervasive include: o Alteration of discharge regimes resulting from increased groundwater withdrawals, o Increased levels of nutrients, particularly nitrate-N in groundwaters discharging from springs, o Extensive recreational disturbance of springs and spring runs, and o Increased disturbance in the form of management actions, for instance exotic species control. Several studies suggest that multiple stressors can affect the productivity of spring ecosystems, suggesting that the measurement of ecosystem metabolism may allow for the quantification of these stressors as well as the health of spring ecosystems. To further develop these concepts the following research directions are suggested: • Development of a holistic management strategy for springs to foster better understanding of the relative importance and synergism of direct stressors at the local level …