The shallow tidal and freshwater coastal wetlands adjacent to the Great Barrier Reef lagoon provide a vital nursery and feeding complex that supports the life cycles of marine and freshwater fish, important native vegetation and vital bird habitat. Urban and agricultural development threaten these wetlands, with many of the coastal wetlands becoming lost or changed due to the construction of artificial barriers (e.g. bunds, roads, culverts and floodgates). Infestation by weeds has become a major issue within many of the wetlands modified (bunded) for ponded pasture growth last century. A range of expensive chemical and mechanical control methods have been used in an attempt to restore some of these coastal wetlands, with limited success. This study describes an alternative approach to those methods, investigating the impact of tidal reinstatement after bund removal on weed infestation, associated changes in water quality, and fish biodiversity, in the Boolgooroo lagoon region of the Mungalla wetlands, East of Ingham in North Queensland. High resolution remote sensing, electrofishing and in-water logging was used to track changes over time– 1 year before and 4 years after removal of an earth bund. With tides only penetrating the wetland a few times yearly, gross changes towards a more natural system occurred within a relatively short timeframe, leading to a major reduction in infestation of olive hymenachne, water hyacinth and salvina, reappearance of native vegetation, improvements in water quality, and a tripling of fish diversity. Weed abundance and water quality does appear to oscillate however, dependent on summer rainfall, as changes in hydraulic pressure stops or allows tidal ingress (fresh/saline cycling). With an estimated 30% of coastal wetlands bunded in the Great Barrier Reef region, a passive remediation method such as reintroduction of tidal flow by removal of an earth bund or levee could provide a more cost effective and sustainable means of controlling freshwater weeds and improving coastal water quality into the future.
I READ with interest the implication of canine trombiculosis in seasonal canine illness (VR, October 20, 2012, vol 171, p 406). I find it surprising, as we in eastern Scotland have been seeing Trombicula in dogs each autumn for many many years and often see them in large clumps, especially on dogs' feet and up their lower legs and yet we have never seen seasonal canine illness. I therefore suggest that they are an unlikely cause of this new disease and that there is a need to keep looking further for the cause.
(1) Leaf area index and stomatal conductance of the bracken canopy below a pine forest were combined to give canopy conductances. Transpiration from the bracken was calculated using these conductance values and appropriate environmental variables in the Penman-Monteith Equation. (2) Calculated transpiration agreed well with independent values derived by weighing transplanted bracken. (3) During exceptionally warm dry periods, transpiration from the bracken accounted for more than half of the total forest transpiration. More usually, the contribution from the bracken understorey was between 20 and 25% of the total transpiration.
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