Delving into effects of anchors on seabeds

SCIENTISTS from the University of Wollongong in Australia are undertaking a study on the effects that anchors and anchor chains have of the habitat of the natural seabed.

The study is taking place on the ocean floor near several Australian ports including Townsville on the edge of the Great Barrier Reef.

It includes preliminary mapping and 3D imaging of the sea floor which have revealed anchor chains of up to 250m which are being dragged across the seabed.

Marine biologist Professor Andy Davis said the anchoring of ships, especially on reefs, might well have damaging environmental impacts on important habitat-forming marine species with implications for fish populations. Efforts would be directed at identifying areas of high conservation value and how they could best be conserved.

It was pointed out that, depending on ocean currents and wind, ships might swing around the point at which the cable rose from the seabed, causing widespread scour.

This could be exacerbated by what was described as a “pack mentality” by ships’ masters having confidence in anchoring near other vessels already at anchor.

Habitat

There were other factors potentially affecting the habitat apart from physical damage to the seabed. These included light “spill” from ships at night, engine or generator noise, engine emissions, shading in the substratum and aesthetic considerations when numbers of vessels were at anchor.

According to Davis, there is a huge knowledge gap about the impact of deep-water vessels on habitats. “Even the shipping industry’s code of practice fails to recognise anchor scour as an important environmental threat… as each region is different, the impact on the ocean floor may vary dramatically from port to port.”

He described the project as the first of its kind to research the impact of anchors on the marine environment, with the aim of creating sustainable anchoring practices throughout the world. Davis hopes to work closely with the shipping industry to achieve this goal.

South African ports such as Durban and Richards Bay have had up to 40 ships at anchor outside at any given time. Ships also anchor outside ports such as Algoa Bay and Table Bay.