Hypersaline Cyanobacterial Mats as Indicators of Elevated Tropical Hurricane Activity and Associated Climate Change

Abstract

The Atlantic hurricanes of 1999 caused widespread environmental damage throughout the Caribbean and US mid-Atlantic coastal regions. However, these storms also proved beneficial to certain microbial habitats; specifically, cyanobacteria-dominated mats. Modern mats represent the oldest known biological communities on earth, stromatolites. Contemporary mats are dominant biological communities in the hypersaline Bahamian lakes along the Atlantic hurricane track. We examined the impacts of varying levels of hypersalinity on 2 processes controlling mat growth, photosynthesis and nitrogen fixation, in Salt Pond, San Salvador Island, Bahamas. Hypersalinity (> 5 times seawater salinity) proved highly inhibitory to these processes. Freshwater input from Hurricane Floyd and other large storms alleviated this salt-inhibition. A predicted 10 to 40 year increase in Atlantic hurricane activity accompanied by more frequent "freshening" events will enhance mat productivity, CO2 sequestration and nutrient cycling. Cyanobacterial mats are sensitive short- and long-term indicators of climatic and ecological changes impacting these and other waterstressed environments.

Genetic Variance in the Composition of Two Functional Groups (Diazotrophs and Cyanobacteria) from a Hypersaline Microbial Mat

“…The surface area and salinity of Salt Pond vary dramatically with the wet and dry seasons, with salinity ranging in extremis from 60 to 350 practical salinity units (PSU). The lake sediments, including portions of the littoral zone that dry out over parts of the year, are covered by a microbial mat, which is dominated by benthic diatoms and nonheterocystous cyanobacteria of the orders Oscillatoriales, Chroococcales, and Pleurocapsales as described elsewhere previously (33,36).…”

“…Communities from hypersaline microbial mats have been the focus of much research (1,4,11,14,17,33,44). Several unique features of these systems make them attractive models for studies involving community dynamics, ecosystem function, and the links between the two.…”

Effects of Elevated Carbon Dioxide and Salinity on the Microbial Diversity in Lithifying Microbial Mats

“…Salinity has also been previously shown to significantly impact the metabolic activity of hypersaline mats under gradients and flux conditions [23,77,81]. Specifically, hypersalinity impedes rates of photosynthesis and nitrogen fixation and limits microbial uptake of dissolved organic carbon [23,82,83]. It is thought that these effects are due to changes in gas solubility of CO 2 and increased diffusion barriers to the release of O 2 under elevated salinity resulting in photooxidation in the mat, as O 2 is a direct inhibitor of the carbon fixing enzyme RuBisCO [77].…”

Anatoxin-a producing Tychonema (Cyanobacteria) in European waterbodies

“…They are distributed in most aquatic and terrestrial habitats, including extreme environments (Paerl et al, 2003;Boyer and Zimba, 2007;Kleinteich et al, 2012). In wateibodies characterized by high concentrations of nutrients, limited water exchange and high temperatures and thermal stability, cyanobacteria can develop with high biomasses, giving rise to the formation of blooms at the surface, euphotic zone or in the metalimnic layers, largely depending on the respective species (Paerl and Paul, 2012).…”