Abstract

This project identified and enumerated the fossilised remains of pollen, charcoal, diatom algae and crustaceans (cladocera) archived in the sediments of three Gunbower Forest wetlands. The following conclusions are made based on the known ecology and taphonomy of the specimens recorded:
1. The sediment sequence from Black Swamp extends back to, and possibly beyond, the boundary of European settlement;
2. The sediment sequences from Green Swamp and Little Reedy Lagoon appear to extend only as far as the onset of river regulation (c 1940 CE);
3. The relatively short nature of the records suggests that, during indigenous times, these wetlands were dry so frequently (3-7 times/decade) that no net sediment accumulation occurred;
4. The fragmentary nature of the diatom fossils in the lower sediments suggests that, even after regular inundation, the wetlands were shallow or existed as mudflats;
5. The three wetlands were originally clear water systems with some submerged aquatic plants. From c 1960 CE these wetlands transitioned into turbid system dominated by phytoplankton and floating plants;
6. The water quality transitioned from clear, fresh, oligotrophic, slightly acid to circum-neutral water to turbid, fresh, eutrophic, neutral to alkaline water;
7. The modern sedimentation rates are in the order of 3-5 mm/yr which is low relative to other wetlands along the Murray River floodplain;
8. The charcoal record increases in the middle and upper sections. While this may reflect increased post-European burning it may reflect increased transport of charcoal into the wetlands. Irrespective, the concentrations of charcoal are low relative to those documented from wetlands in other Australian biomes.