Macroinvertebrate sampling is a core part of Georges Riverkeeper’s water quality monitoring and River Health Report Card program. Each sampling season is a busy one, split between early mornings in the field and long, careful hours back in the lab.
For our Environmental Project Officer, Phuong To, it’s also one of the most rewarding parts of her role. Here, Phuong offers an insight into what this work looks like on the ground, from muddy riverbanks to microscopes, and explains why these small creatures tell such a big story about the health of the Georges River.
Out in the field
Macroinvertebrate sampling is split over spring and autumn. And each season, the river tells a slightly different story. With nets, trays and sample jars packed, Phuong moves between monitoring sites across the catchment, from natural upstream reaches to more urbanised sections downstream. While the sampling method stays the same, no two sites are ever alike. Phuong explains that as soon as you step into the water the differences are obvious. "Flow, riverbed composition, riparian vegetation and surrounding land use all influence what lives in the water, and experiencing it firsthand gives us a clear picture of how each site functions," she says.
Working alongside a university intern this year has added another layer to the fieldwork. Sharing the physical tasks, comparing observations and discussing what they see helps deepen understanding of the catchment as a whole.
Equally valuable are the conversations with locals. Phuong says, "People walking dogs, fishing, paddling or simply passing by often stop to ask what we’re doing. Others share memories of how a creek looked years ago, or what they’ve noticed changing over time, clearer water, fewer fish, more vegetation, or sometimes the opposite." These local observations don’t replace the data, but they add context and remind us that the river is deeply woven into everyday community life.
Sampling macroinvertebrates is hands-on and often muddy work. It involves disturbing the riverbed with a kick-net, and transferring the collected material into buckets, spreading it onto sorting trays, then carefully preserving samples for later analysis. Phuong says, "There’s always a moment of anticipation when the samples are tipped onto the tray. That first glimpse of what’s living there offers early clues about how that site might be functioning."
From the river to the lab
Back in the lab, the work continues. Samples are preserved and identified, usually to family level, sometimes to order. Under the microscope, the river’s hidden life becomes clear, and patterns emerge.
Phuong explains: "So we’re seeing clear contrasts between sites in good ecological condition and those that are more impacted. Healthier sites tend to support a wider range of sensitive macroinvertebrates, such as mayflies, stoneflies and caddisflies. These species rely on clean, well-oxygenated water and relatively stable habitats. In more impacted areas, communities often shift toward more tolerant species like mosquito larvae and segmented worms, organisms that can persist under environmental stress."
These observations feed into SIGNAL 2 scores, taxon richness and biodiversity indices, forming the foundation of the River Health Report Card. Because many macroinvertebrates spend months or years in the river, they provide insight into water quality over time, not just on the day of sampling.
Learning, patterns and what comes next
During recent sampling, Phuong has also been mentoring a senior high school student completing a Science Extension project. Sorting and identifying real samples together has been a great way to share skills, build confidence, and transform field collections into meaningful ecological data.
While much of the spring sampling is complete, there’s still more sampling to do once Autumn arrives. Each remaining sample adds another piece to the picture of how the Georges River is responding to pressures and protection efforts across the catchment. These small organisms may go unnoticed by most river users, but together, they tell a much bigger story about the river’s health.
Learn more about our River Health and Research Program here.
