Warming ecosystem temperatures in a Florida ecotone experiencing transition

The existence of marsh habitats depend on their ability to build up soil in order to keep up with rising seas. The roots of plants found in marsh habitats “push up” the soil helping to increase the marsh elevation. However, with the oxygen provided by the marsh plants, bacteria in the soil are able to decompose the debris, resulting in decreasing marsh elevation.

This project investigates how warming temperatures and invading plants alter marsh elevation. In order to test this, our team have installed warming chambers (photos above) at three locations along the Florida coastline. The chambers have been be placed over vegetation plots containing pure marsh vegetation (e.g., smooth cordgrass) or a mixture of marsh vegetation and mangroves. For the next three years we will measure and compare root growth, root biomass, above-ground biomass, decomposition rates, and surface elevation among the plots.


 

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The role of Glycine betaine in range expansions; protecting mangroves against extreme freeze events.

Glycine betaine is an organic osmolyte that plays a key role in osmoregulation, allowing a variety of plant species to tolerate environmental stresses such as salinity and extreme temperatures. Glycine betaine improves enzyme and membrane integrity within the cytosol and chloroplasts, and helps mediate osmotic adjustment in plants grown under stress conditions. A few mangrove species, including the common mangrove Avicennia marina, accumulate relatively high concentrations of glycine betaine in response to increased salinity, allowing these plants to survive across the intertidal zone, suggesting an additional tolerance to hypersaline conditions. However, the role glycine betaine plays in allowing mangroves to survive extreme weather events such as impact freezes is unknown.

Due to a warming climate mangroves are expanding their range poleward. Their current range limit now includes locations that experience freezing temperatures suggesting mangroves do have a mechanism to survive freezing conditions. In this research project I used a combination of common garden experiments grown in various locations across southern USA to test if freezing temperatures correspond with increased glycine betaine concentrations in A. germinans and if increased glycine betaine synthesis corresponds with increased survivability. The results of this experiment will help our understanding of how mangroves expand their ranges and adapt to survive extreme freeze events.


 

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Foliar water uptake of coastal wetland plants from an atmosphere of high humidity

An increasing number of studies have linked climate change to species range shifts and changes in community structure in terrestrial and marine habitats. Many of these range shifts are associated with shifts in higher latitude, with species expanding their range poleward with increasing temperatures. Mangrove ecosystems are also expanding their range limits poleward, encroaching upon saltmarsh systems, and changing community structures across their newly acquired habitats. Temperature, however, does not explain the range limitation of mangroves along arid coastlines, such as in Baja, Mexico, where mangroves are range limited at latitudes southward of their temperature limitation. Here, plants are likely limited by the arid zone conditions along this coastline, in particular water availability, which can be as low as 70mm per year.

Plants living in arid zones often have water saving adaptations and access available water sources such as dew and mist through foliar water uptake. For this project I am investigating if mangroves living along the arid coast of Baja, Mexico, use foliar water uptake to increase non-saline water availability and if this increases plant productivity. The results of this study will increase our understanding of how mangroves will respond to changes in water availability, and how these changes will impact mangrove range expansion.  By understanding how coastal wetland communities will respond to changes in water availability we can better plan for future scenarios such as arid zone expansion and increased extreme weather events.


 

adams beach mangrove

The role of groundwater on above- and belowground growth in mangrove forests

Mangrove forests are recognized as important sites for nutrient and carbon cycling along subtropical and tropical coastlines. They reduce nutrient runoff into the coastal zone, providing a buffer to seagrass and coral habitats. Degradation of these systems leads to a significant release of greenhouse house gases in to the atmosphere, an increase in erosion, and increases nutrient runoff into coastal zones. This research project focuses on the role of non-saline groundwater on the growth and biomass allocation of Avicennia marina, the mangrove species most commonly found along the east coast of the Australian coastline where this research was performed.

This study shows that mangroves use non-saline groundwater and rainwater when available rather than saline water sources. Groundwater flows into the intertidal stimulates organic matter accumulation in aboveground biomass suggesting the availability of non-saline water sources, such as groundwater and rainfall, are important for the growth and productivity of mangrove forests.