Assessing the potential for biotic communities to recolonise freshwater wetlands affected by sulfidic sediments

1. The formation of sulfidic sediments in response to factors such as secondary salinisation and fertiliser usage is an emerging concern for the management of many freshwater wetlands. However, fundamental knowledge regarding the influence of sulfidic sediments on the aquatic biota is still lacking
2. This study investigated the potential for biota to recolonise wetlands affected by sulfidic sediments, by assessing zooplankton hatching and aquatic plant germination following inundation with freshwater. Sediment samples were collected from 16 wetlands in the southern Murray-Darling Basin, Australia, that ranged in condition from non-impacted to possessing a known history of sulfidic sediments and ⁄ or acidification.
3. Principal Components Analysis indicated that the wetlands separated out into five different groups based on their sediment chemistry: non-impacted, sulfidic, sulfidic and highly saline (sediment EC 46 800–209 000 lS cm)1 ), sulfidic and potentially acidic (sediment pH 5.81–6.45 and ANC 0.07–0.31% CaCO 3 ), and sulfidic and acidic (sediment pH 4.37 and ANC 0.00% CaCO3
4. A viable dormant propagule bank was present in all wetlands, but the taxon richness of zooplankton and aquatic plants was significantly lower in wetlands affected by sulfidic sediments compared with those that were non-affected.
5. This suggests that zooplankton and aquatic plants will be capable of recolonising wetlands that have accumulated sulfidic sediments via their propagule banks if the appropriate remediation measures are undertaken, although the communities developing are likely to be less diverse compared with those in non-affected wetlands.