Seagrass blamed for poor Eastern Beach water quality

DECOMPOSING seagrass has been weeded out as the culprit behind an unusual spike in poor water quality at Eastern Beach.

There were three unexpected incidents of high bacterial readings in routine water sampling at the beach between December 28 and January 24, and the Environmental Protection Authority (EPA) Victoria began an investigation.

“The results didn’t match the usual cause – rainy weather that washes pollution into waterways and the bay from the surrounding land – so we stepped up the sampling regime and called in some help,” EPA program co-ordinator for beach reports Darren Cottam said.

EPA took water samples and worked with the City of Greater Geelong to gather information on sources and activities on the Geelong Waterfront and in the catchment, and Barwon Water ran extra checks of its systems, looking for possible leaks.

The authority also warned the public by issuing a swim advisory and SMS alerts, and lowered the daily Beach Report water quality forecast to “fair” during the length of the investigation.

“Back in the office we were looking at more suspects including catchment rainfall, and incidents of high winds or increased wave activity, but there was nothing that pointed to a likely source,” Mr Cottam said.

“Eastern Beach has generally good water quality and is often one of the best performing beaches in the bay, so there had to be a hidden factor causing the problem.”

In the end, EPA’s proactive collection of water samples across the waterfront investigating different potential sources was the factor that cracked the case.

“We had eliminated the likely human causes of raised bacterial levels, and a natural cause became our number one suspect,” Mr Cottam said.

Sampling indicated the spikes may have been associated with areas of dead, decomposing seagrass and related sediment containing bacteria, which can get resuspended in the water by tides and winds but is considered a low risk to public health.

Seagrass has been linked to spikes of high enterococci in previous years at beaches, such as The Dell at Clifton Springs, Mentone and Altona.

The blackened seagrass can be found on the sand bed or floating in the water at both ends of Eastern Beach.

In the meantime, Eastern Beach has returned to its usual state – the past six water samples have met standards for swimming during dry weather and the forecast has been returned to “good”.

As a precaution, a water quality alert is still on EPA’s website advising beachgoers to avoid coming into contact with blackened, dead seagrass, and water quality monitoring along the Eastern Beach waterfront continued through February.

For the EPA’s daily Beach Report, head to epa.vic.gov.au/for-community/summer-water-quality/beach-report