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Wetlands are biogeochemically active ecosystems where primary production and respiration interact with physico‐chemical conditions to influence nutrient availability across spatio‐temporal scales. The effect of episodic disturbances on water quality dynamics within wetlands is relatively unknown, especially in large oligotrophic wetlands such as the Everglades. We describe a range of episodic disturbance events and their impacts on the spatio‐temporal dynamics of surface water total N (TN) and total P (TP) concentrations in the Everglades as a means to understand their effect and legacies. Water quality monitoring along the two principal drainages—Taylor Slough (TS) and Shark River Slough (SRS)—has been ongoing since 2000, spanning myriad disturbances ranging from high‐energy storms such as Hurricane Wilma in 2005 to a record cold event in 2010 and large fires. Local events include pulsed rainfall, low marsh stage, and stage recession and recovery (i.e., droughts and subsequent dry‐to‐wet transitions). The deposition of marine‐derived sediment from Hurricane Wilma corresponded with a doubling of TP in SRS mangrove sites (from 0.39 to 0.84 μmol/L) before recovering to pre‐disturbance mean after 5–6 yr. A brief increase in TP within one week of the 2010 cold event was followed by delayed spikes in TN (>1000 μmol/L) and TN:TP exceeding 5000 after one month. In 2008, a large fire in upper SRS prior to the wet season caused a lagged TP pulse at downstream locations SRS2, SRS3, and possibly SRS4. TP also varied negatively with depth/stage in marsh sites and positively with salinity in estuarine sites, reflecting physical concentration or dilution effects. In upper TS, TP varied according to extremes such as high rainfall and low stage relative to normal conditions. Although excess P in the Everglades is generally derived from anthropogenic upland or natural marine sources, episodic disturbance mobilizes internal sources of nutrients along an Everglades freshwater‐to‐estuary continuum, affecting water quality from days to years depending on disturbance type and intensity. The capacity for resilience is high in coastal wetland ecosystems that are exposed to high‐energy tropical storms and other episodic events, even in the highly managed Florida Everglades.

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Agricultural and urban runoff pumped into the perimeter canals of the Arthur R. Marshall Loxahatchee National Wildlife Refuge (Refuge), a 58,320-ha soft-water wetland, has elevated nutrients which impact the Refuge interior marsh. To best manage the Refuge, linkages between inflows to the perimeter canals and environmental conditions within the marsh need to be understood. Conductivity, which typically is high in the canals and lowest at the most interior sites, was used as a surrogate tracer to characterize patterns of constituent transport. The Refuge was initially classified into four zones based upon patterns and variability in conductivity data: Canal Zone; Perimeter Zone (canal to 2.5 km into the interior); Transition Zone (2.5 to 4.5 km from the canal); Interior Zone (>4.5 km from the canal). Conductivity variability declined from the Perimeter to the Interior Zone, with the highest variability in the marsh observed in the Perimeter Zone and the lowest variability observed in the Interior Zone. Analysis of other water quality parameters indicated that conditions in the Perimeter and Transition Zones were different, and more impacted, than in the Interior Zone. In general, there was a positive relationship between structure inflows and canal phosphorus concentrations, including discharges from treatment wetlands and bypasses of untreated water. This classification approach is applicable for stratified sampling designs, resolving spatial bias in water quality models, and in aiding in management decisions about resource allocation.

Recent appearance of cattail (Typha domingensis) within a southern Everglades slough-Upper Taylor Slough (Everglades National Park)-suggests ecosystem eutrophication. We analyze water quality, nutrient enrichment, and water management operations as potential drivers of eutrophication in Upper Taylor Slough. Further, we attempt to determine why surface water phosphorus, a parameter used commonly to monitor ecosystem health in the Everglades, did not serve as an early warning for eutrophication, which has broader implication for other restoration efforts. We found that surface water total phosphorus concentrations generally were below a 0.01 mg L(-1) threshold determined to cause imbalances in flora and fauna, suggesting no ecosystem eutrophication. However, assessment of nutrient loads and loading rates suggest Upper Taylor Slough has experienced eutrophication and that continued total phosphorus loading through a point-source discharge was a major driver. These nutrient loads, combined with increases in hydroperiods, led to the expansion of cattail in Upper Taylor Slough. We recommend other metrics, such as nutrient loads, periphyton and arthropod community shifts, and sediment core analyses, for assessing ecosystem health. Monitoring surface water alone is not enough to indicate ecosystem stress.