MICROBIAL MATS: GREEN FILTERS OR SOURCES FOR P?

PERILLO, V.L.; LA COLLA, N.S.; SERRA, A.V.; PAN, J.; BOTTÉ, S.E.; CUADRADO, D.G.

virtual

Congreso; III International Congress of Rivers and Wetlands; 2021

Universidad de la Costa

Remediation of eutrophic waters is key as the algae that bloom in such water bodies can have negative effects on ecosystem function and public health, and also impact economic and recreational activities. Thus, so-called ?green filters? are being studied for bioremediation practices, and among these, microbial mats (complex, stratified biosedimentary consortia of bacteria, archaea, and microeukaryotes) promise to have multiple uses, from the chelation/biomineralization of metals to degradation of oil spills. However, few studies have focused on epibenthic microbial mats as possible green filters to remediate eutrophic seawater. The use of these microecosystems in this way would possibly require maximizing their contact with polluted water, which would imply changing the natural conditions under which these microbial mats prosper (i.e. supratidal areas). Hence, evaluating the metabolic adaptation of microbial mats to different inundation conditions in relation to their short-term efficiency at nutrient removal is an essential first step for their consideration as possible green filters. The study consisted of incubating epibenthic microbial mats, taken from a tidal flat located in the Bahía Blanca Estuary, Argentina, with and without the addition of a high phosphorus concentration (5 mg PO43- L-1) and under two simulated tidal-flooding conditions (i.e., periodically exposed to air or continuously flooded). High P concentrations as well as continual flooding of the microbial mats resulted in a change in cyanobacterial communities evidenced by a decrease in the dominant Coleofasciculus chthonoplastes population, giving rise to the dominance of other representatives, such as Arthrospira sp. or Oscillatoria sp. By comparison to natural successional patterns, mats reverted to a less-mature cyanobacterial community under continuous inundation. Water P removal, as seen in triplicate samples, was highly efficient (60-87 %) when the mats were treated with the high-P water. However, microbial mat behavior changed from sink to source of P when the mats were incubated in seawater with no P addition, suggesting that mats can both function as sinks or sources of P, depending on the condition of the water they come in contact with. These results indicate that microbial mats could potentially be useful as green filters in highly eutrophic waters but should be reconsidered when P concentration is lower.