Freshwater and Riparian Ecology


Freshwater Microbiology

Microbes are everywhere and are central to the functioning of every organism on this planet. Despite their recognised importance, we have merely glimpsed into their roles in ecosystems. By gaining better understanding of microbes, we are able to more clearly understand and predict how our world operates and how it might change. This project is multifaceted and examines how anthropogenic disturbance (i.e., land use change, riparian clearing) alters ecosystem function from a microscale.  Understanding how microbes interact with changing environmental conditions can help us understand and restore freshwater ecosystems. So far we have uncovered several novel findings including:

  • Leaf litter from invasive tree species can alter the micro-ecosystem and microbial decomposition processes of native plant litter in streams. Further, reductions in water quality due to urbanisation can increase this impact (in prep).
  • The fringe of remnant riparian zones maintains suitable soil conditions (via diverse vegetation structure and periodic saturation) to support putative N cyclers, which could amount to higher potential for N removal.

Biogeochemistry

Globally, streams and rivers are increasingly vulnerable to environmental perturbations associated with changing land use and hydrologic regimes. In urban and agricultural landscapes, stream ecosystems are often stressed (altered hydrology, land clearing, increased inputs of nutrients) which in turn can result in poor water quality, eutrophication and reduced biodiversity. However, management of stream nutrient and carbon concentrations can reduce negative anthropogenic impacts on ecosystem functioning (e.g., primary production,me- tabolism, food webs). Determining where best to focus management efforts to reduce stream nutrient and carbon concentrations across urban and agricultural regions requires a strong understanding of biogeochemical processes. This research has contributed to the management of freshwater ecosystems impacted by urbanisation and improved knowledge in this area, including:

  • The quality and quantity of dissolved organic matter in streams is strongly impacted by landuse change and interacts with seasonal hydrologic regimes; ultimately changing DOM bioavailability, food web dynamics and biogeochemical cycling.
  • Planting woody vegetation can reduce nitrogen concentrations in surface water and fluvial sediments of urban and agricultural streams. Showing that local riparian restoration can be a cost-effective strategy for managing excess nutrients and carbon in flat and permeable urban land- scapes, particularly during low flow periods.

Invertebrate Ecology

Understanding responses of freshwater invertebrate communities to different anthropogenic disturbances can guide best management practices. This project evaluated the relative influence of local-scale riparian characteristics and catchment-scale imperviousness on the macroinvertebrate assemblages of streams in the flat, permeable urban landscape of Perth, Western Australia. So far we have found:

  • For urban streams in sandy geological regions, local-scale riparian restoration can influence the structure of macroinvertebrate assemblages to a greater degree than managing the influences of catchment-scale imperviousness.