Dr Pat Hutchings loves worms. "Polychaete" worms. But far from being shy about her passion for sea grubs, Pat has been telling the world. As principal research scientist for the Australian Museum's worm section, she has spent decades researching, publishing and speaking internationally on the importance of polychaete worms (long segmented sea worms) and other marine invertebrates for coral reef eco-systems. It is a little known subject that together with Pat's studies on marine algae, is helping her assess the impact of human activity on the Great Barrier Reef.

"Coral reefs are dynamic systems characterized by a delicate balance between reef growth and reef destruction," says Pat. "Reef eaters" - including sea worms and other species such as certain kinds of molluscs and crustaceans, sponges, soft corals and fish - wear down the reefs. They secrete acids, graze and/or bore into the coral substrates as part of a process known as "bioersosion".

This essential process of natural degeneration is disturbed when populations of reef eaters are damaged.

"Some species will disappear," says Pat, "while others, like the crown-of-thorns starfish, multiply unchecked. We are worried that human activity is causing this kind of damage."

Pat suggests the main source of man-made problems include coastal deforestation, harmful agricultural run-off, construction works, anchor damage, and the removal of fish populations and other reef animals.

"While the effects are often not immediate," she explains, "Over time the reef may not recruit new colonies of certain animals and fish; algae may overgrow areas where corals once lived; and the underlying skeletal structure of the reef can be weakened."

According to Pat, in some places where the balance has been significantly damaged by human activity, once rich coral reefs have been replaced by rocky fields of murky algal growth.