Rotting seaweed on Warnbro Sound foreshore poses no health risks despite smell, says City of Rockingham


Seagrass built-up on Safety Bay Beach.
Seagrass built-up on Safety Bay Beach.

CITY of Rockingham has allayed residents’ concerns about rotting seaweed potentially emitting hydrogen sulphide, saying it is an important part of the local marine ecology.

At this time of the year, sea grass deposits, known as wrack, accumulate along the Warnbro Sound foreshore across many hundreds of square metres and occurs in long, thin, low-lying piles.

“In a few areas, the accumulation is larger, particularly along the northern third of the beach,” a City spokesman said.

“The City is aware of community and residents’ concerns regarding the possibility of hydrogen sulphide being generated by the wrack and the potential for it to impact on health.

“Hydrogen sulphide can be smelled at very low levels, well below the level where it causes any health effects, so simply smelling it is not a health issue.

“Based on the volume of wrack usually present in Warnbro Sound, the maximum level of hydrogen sulphide generated is extremely unlikely to pose any risk to human health.”

The City acknowledged that the naturally occurring odours of decomposition had an impact on the amenity of the beach and recognised it was inconvenient for beach users and residents.

However, the spokesman said these odours were a short term problem which resolve quickly and were not detrimental to health.

“Wrack is an important element in the marine environment,” he said.

“Research confirms the significant benefits created by the decomposing materials to a range of marine creatures, including amphipods, worms, bivalves, crabs, sea cucumbers and sea urchins.

“These creatures are critical to the environment and food chain.

“An additional benefit is that wrack creates a barrier to waves generated by winter storms.

“The wrack protects the beach and dunes from excessive erosion that may otherwise occur.

“Removing wrack would create significant and long lasting flow-on impacts to the Shoalwater Marine Park.

“Removal would also impact the wider community including the recreational and commercial fishing industry, divers, environmentalists and tourists.

“These impacts would be long lasting and might not be able to be corrected.”

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