Following reports of dead and dying beach worms in June, laboratory testing of beach worms, pipis, sea water and sand from this location has found no evidence of pesticide, disease or algal toxins.

Concerns were raised that this incident had resulted from recent aerial herbicide spraying of the weed bitou bush by NSW National Parks and Wildlife Service (NPWS).

According to a NPWS spokesperson there was no evidence beach worms were affected or contaminated by herbicide spraying.

Additional investigations by the Department of Planning Industry and Environment and the University of NSW concluded the beach worms were affected by a combination of beach erosion and significant fresh groundwater outflows into the beach intertidal zone.

Since the start of the year the region has experienced higher than average rainfall.

The Tarbuck Bay rain gauge (close to Yagon Beach) recorded 850mm in March alone.

The rain caused extensive flooding in the Myall Lakes and the highest water levels recorded since 1927.

Storms in late May caused extensive erosion to Yagon Beach, removing 20-25m of beach width and 2-3m of beach depth.

Following the storm, the lowered beach surface was subsequently closer to the fresh groundwater table, exposing the saltwater-dependent beach worms to large amounts of freshwater flowing across the sand surface.

YOU MAY ALSO LIKE: MidCoast Council adopts climate change strategy

Adult beach worms do not move around the beach in any significant way and under normal conditions the fresh groundwater flows are well below the depth of sand they inhabit.

Beach worms are unable to regulate their internal fluids and so, when in contact with freshwater, the water moves through their skin into their bodies and disrupts internal processes eventually killing the worms.

A team of University of NSW engineers examined Yagon Beach, finding large amounts of freshwater flowing across the beach face at low tide.

Excessive rainfall had occurred in the area over the previous six months.

During the fieldwork no beach worms were found where freshwater was discharging across the beach at low tide however, healthy worms were found in adjacent areas with normal ocean salinity.

The work also concluded that the beach worm deaths occurred during a period of reduced wave and tide effects in June, meaning freshwater flows onto the beach were less affected by ocean wave action, exposing beach worms to freshwater flows which killed them.

YOU MAY ALSO LIKE:

Our journalists work hard to provide local, up-to-date news to the community. This is how you can continue to access our trusted content: