Pollutants are substances that negatively impact water quality. Some are naturally occurring but become pollutants when their concentrations increase above normal levels and become harmful to water quality and aquatic species.

In the kanamaluka / Tamar estuary and catchment area, pollutants include nutrients (phosphorus and nitrogen), pathogens (enterococci), and suspended solids, which enter the waterways by running off the land with rainfall, or directly from a point source (e.g. from sewage treatment plants or other outfalls).

Rainfall off the land is the dominant source of pollutants in the kanamaluka / Tamar estuary and Esk rivers catchment area. Urban areas contribute a substantially higher pollutant load relative to their land area due to large areas of sealed surfaces and high populations. Launceston’s combined sewage and stormwater system discharges a mix of sewage and urban stormwater into the estuary during high rainfall events, contributing to pathogen pollution on less frequent occasions. Upgrades are being made to the system as part of the River Health Action Plan.

Monthly water samples are tested for nutrient levels – that is, checking how much nitrogen and phosphorus is present. While nutrients are important, too much can be damaging to the ecosystem.

Both nitrogen and phosphorus encourage algal and aquatic plant growth, which provides food for fish and other organisms. However, if nutrient levels are too high, algae/plant growth can increase so much that they use up all the oxygen in the water. This can have severely negative health impacts on other organisms in the ecosystem.

Excess nutrients can enter waterways from the land, running off farmland and urban areas in animal waste and fertilizers, as well as coming from sewage treatment plants.

Pathogens are organisms that can cause disease. The monthly water samples collected by the TEER Program are analysed for a specific pathogen, enterococci, which is a type of bacteria.

Sediment is a naturally occurring solid material that is broken down and can be moved to another location. Sedimentation is the process of sediment moving to a location and building up there, and is a natural process in the upper kanamaluka / Tamar estuary.

Fine silts are carried in freshwater flows, from the catchment and into the estuary, where they meet salt water and clump together (called floculation). This makes the sediments heavier and causes them to settle out of the water column. Flows and the outgoing tide move them downstream, and the incoming tide carries them back upstream where they deposit in mudflats in the upper estuary.

Heavy metals are metals that have a relatively high density compared to water and are toxic even in small concentrations. Heavy metals can come from natural sources (like volcanic eruptions); however, their concentrations can be increased by human activities such as mining and metal smelting works.

The TEER Program monitors for heavy metals in the kanamaluka / Tamar estuary each month, measuring concentrations of seven heavy metals including mercury, arsenic, and lead.

Thankfully, since monitoring began in 2010, the concentrations of dissolved metals within the estuary have been consistently low, at levels considered to be good in terms of ecosystem health.