Case study: Blue Cypress Marsh Conservation Area, Florida, USA

Name of the respondent

Kimberli J. Ponzio, Steven J Miller, Dean Dobberfuhl
St. Johns River Water Management District

What you have seen in the wetland – state, change, and drivers

Background – The Blue Cypress Marsh Conservation Area (BCMCA) is in the headwaters of the Upper St. Johns River Basin (USJRB) in east-central Florida. The USJRB originally encompassed nearly 400,000 acres and was characterized by a mosaic of habitats dominated by extensive herbaceous marshes and numerous shallow lakes. Conversion of the historic USJRB floodplain to agricultural lands began early in the 20th century and by 1972 approximately 62% of the 100-year floodplain had been lost. Agricultural development led to widespread ecological degradation, including loss of floodplain water storage, increased potential for economically damaging floods, diminished water quality, disruption of the natural hydrologic and fire regimes, decreases in fish and wildlife populations, and expansion of exotic and invasive species.

To provide flood protection in conjunction with environmental protection and enhancement, the St. Johns River Water Management District (District) partnered with the U.S. Army Corps of Engineers on a project to reclaim and restore historic floodplain functions using a “semi-structural” approach, whereby water storage capacity was expanded through the acquisition and restoration of over 70,000 acres of former floodplain wetlands and active water management was facilitated through the construction of levees, canals, and water control structures. Project features included Water Management Areas (WMAs) designed to improve water quality by retaining agricultural and urban runoff and Marsh Conservation Areas (MCAs) designed to store floodwater, restore historic wetland habitats, and further improve water quality (Figure 1). The Blue Cypress Marsh Conservation Area (BCMCA; 29,400 acres) is one of the most pristine MCAs in the headwaters of the USJRB and is characterized by extensive herbaceous wetlands interspersed with water lily sloughs, shrub/tree islands (Figure 2), and a shallow lake lined with cypress trees (Figure 3). One operational goal for the BCMCA is to re-establish natural hydrologic patterns that are defined by a comprehensive set of numerical environmental hydrologic criteria (EHC). Adherence to the EHC provides a direct quantifiable method for assessing long-term environmental performance. The establishment of natural hydrologic patterns in BCMCA enhances the ability to provide for important ecosystem services such as nutrient retention, carbon sequestration, fish and wildlife habitat (including habitat for several federally listed or endangered species), and public recreation while still meeting the mandated level of flood control. This approach to water management has been successful in the past and has resulted in the acknowledgement from several entities of the value of the ecosystem that has been restored and preserved. In 1998, the St. Johns River was identified as an American Heritage River; the USJRB Project received the 2008 Theiss International River Prize; and, in 2016, the Florida Engineering Society lauded the USJRB Project as a Project of the Century due to its multipurpose semi-structural approach to flood control and wetland restoration. The Indian River Citrus League, an important stakeholder in the region, also said that the USJRB has been a game changer for citrus growers in the watershed due to the availability of water for irrigation and freeze protection”.

State, Change, and Drivers – While BCMCA remains one of the most pristine areas in the USJRB, its management has not been without challenges and there are current and emerging stressors that threaten to diminish its condition. As the main driver of ecological change, the importance of getting the appropriate hydrology in BCMCA is of paramount concern. In the last decade, EHC have provided the basis for modifying structure operations to reduce soil oxidation, slow nutrient release, retard the encroachment of invasive species, and prevent the loss of important slough habitats. However, in the face of climate change, which may result in a shift in rainfall patterns and increased temperatures, it may become increasingly difficult to meet the EHC. Climate change may eventually force mangers to reconsider what constitutes the “appropriate” hydrology for the BCMCA and reassess habitat expectations.

Fire is another major driving force influencing USJRB ecosystems. Already, landscape fragmentation, increasing urban development, and strictly enforced burn regulations make it challenging to restore historic natural fire patterns. The BCMCA is currently burned on a 5-7-year cycle. However, vegetation changes such as a dramatic increase in Carolina willow (Salix caroliniana) has altered the ability to use fire because willow shades out and outcompetes the understory vegetation needed to support a burn. This has led to the increased use of herbicides to supplement burning in re-establishing herbaceous marsh. Increased temperatures and altered rainfall patterns due to climate change will likely have a dramatic influence on the ability to use fire as a managed disturbance in the future.

There are several exotic, invasive species (both plants and animals) that pose potential threats to the natural flora and fauna of the BCMCA.  Plant species include: Old World climbing fern, Lygodium microphyllum, Paragrass Urochloa mutica, Wright’s nutrush Scleria lacustris, West Indian marshgrass Hymenachne amplexicaulis, and water hyacinth Eichhornia crassipes.  The ability of these species to form dense monotypic stands allows them to outcompete natives, reduce plant species diversity, and adversely affect habitat for fish and wildlife.  Most are fire resistant and are currently being controlled primarily by extensive herbicide treatments.  However, there is growing public concern that herbicides are harming the environment, killing off desirable native plants, and degrading water quality.

Invasive exotic fish species include: suckermouth catfish Hypostomus plecostomus, sailfin catfish Pterygoplichthys disjunctivus, and blue tilapia Oreochromis aureus.  Sailfin catfish and tilapia can extensively alter important littoral habitats.  Because they build extensive burrows, sailfin catfish even pose a threat to the integrity of project levees.  No methods are currently available to control these species and their effects on native fish communities are unknown.  One invasive exotic invertebrate which is expanding in the USJRBP is the island apple snail Pomacea insularum.  There is concern these large prolific snails may adversely affect populations of native apple snails Pomacea paludosa, and potentially negatively affect native plant species.          

One of the most concerning threats to BCMCA is increasing phosphorous levels (TP) in Blue Cypress Lake in conjunction with an increase in the frequency and intensity of blue-green algal blooms (Figure 4).  While several contributing factors are being considered to explain the TP increase, much of the current focus is on investigating the role of biosolid (a by-product of wastewater treatment) applications on farmland in the watershed.  There has been nearly a two-fold increase in TP in the lake since biosolids were first applied in 2007.  Despite a 2018 moratorium on biosolid applications, a real concern is that legacy phosphorus may continue to impact the nutrient status of Blue Cypress Lake well into the future.

Why you took part & what you hope will come from the survey

Desired Outcomes – The BCMCA is a wetland of international importance and should be monitored and protected within an adaptive management context.  Employing science-based management strategies and maintaining a strong base of stakeholder support will be pivotal in protecting the ecological integrity of the BCMCA as well as other USJRB project areas, and in maintaining the important ecosystem services they all provide into the future.  However, climate change, exotic species, and increasing nutrient loading all pose significant threats to the ability to meet these goals.  Implementing adaptive strategies that account for the changing chemical, physical, and biotic environments will be critical to this effort.