ORGANIC MATTER IN LEAF LITTER LEACHATE IMPACTS CYANOBACTERIAL BLOOMS BOTH POSITIVELY AND NEGATIVELY

Much of our understanding of the links between biogeochemical processes and freshwater cyanobacterial blooms has focussed on nutrient concentrations and loads. However, the impact of other terrestrial compounds on cyanobacterial growth is less well studied. Our research focussed on characterizing tDOM and determining the effect of tDOM leachate from leaf litter and terrestrial soil on growth of a toxic cyanobacterial species. Chemical studies, Using 1H-NMR, showed that the leachate contained a complex mixture of dissolved organic compounds, with the amino acid, proline, as well as gallic acid and polyphenols had the greatest inhibitory effect on cyanobacterial photosynthesis. In a mesocosm study, the concentration of leaf leachate additions impacted the scale of suppression of a toxic cyanobacterial bloom. Light availability was not the primary driver. By contrast, at lower concentrations, leachate from soil and leaves were shown to stimulate growth of algae, either directly from increased dissolved inorganic nutrient concentrations, or indirectly via microbially-mediated transformation of organic nutrients into inorganic nutrients. Our research shows the important role that tDOM plays in freshwater systems, both directly on cyanobacterial growth, and indirectly via the impact on the microbial community. With DOM concentrations increasing globally, the ultimate impact on the ecosystem health of freshwaters warrants further investigation.

Presentation Preference: Oral

Primary Presenter: Michele Burford, griffith university (M.Burford@griffith.edu.au)

Authors:

Michele Burford, Griffith University  (m.burford@griffith.edu.au)

Hannah Frankliin, Griffith University  (h.franklin@griffith.edu.au)

Anthony Carroll, Griffith University  (a.carroll@griffith.edu.au)