INFLUENCE OF DIFFERENT SALT MARSH PLANTS ON HYDROCARBON DEGRADING MICROORGANISMS ABUNDANCE THROUGHOUT A PHENOLOGICAL CYCLE

Abstract

The influence of Juncus maritimus, Phragmites australis, and Triglochin striata on hydrocarbon degrading microorganisms (HD) in Lima River estuary (NW Portugal) was investigated through a year-long plant life cycle. Sediments un-colonized and colonized (rhizosediments) by those salt marsh plants were sampled for HD, total cell counts (TCC), and total petroleum hydrocarbons (TPHs) assessment. Generally, TCC seemed to be markedly thriving by the presence of roots, but without significant (p > 0.05) differences among rhizosediments. Nevertheless, plants seemed to have a distinct influence on HD abundance, particularly during the flowering season, with higher HD abundance in the rhizosediments of the fibrous roots plants (J. maritimus <P. australis <T. striata). Our data suggest that different plants have distinct influence on the dynamics of HD populations within its own rhizosphere, particularly during the flowering season, suggesting a period of higher rhizoremediation activity. Additionally, during the vegetative period, plants with fibrous and dense root system tend to retain hydrocarbons around their belowground tissues more efficiently than plants with adventitious root system. Overall results indicate that fibrous root plants have a higher potential to promote hydrocarbons degradation, and that seasonality should be taken into account when designing long-term rhizoremediation strategies in estuarine areas.

KEY WORDS::

• hydrocarbon
• salt marsh plants
• fibrous roots
• adventitious roots
• rhizoremediation
• Lima estuary

ACKNOWLEDGMENTS

Authors acknowledge Nelson Matos for helping in summer and autumn sampling, Paula Guedes and Jaqueline Cochofel for helping in TPHs determinations and Paulo Alves (Biology Department, Faculty of Sciences, University of Porto) for plant identification. This work was partially funded by Fundaçãopara a Ciência e Tecnologia (FCT), Portugal, through the project PTDC/MAR/099140/2008, and the PhD fellowships awarded to H. Ribeiro (SFRH/BD/47631/2008) co-financed by POPH/FSE.