Introduction 

Marine debris consists of discarded or lost unnatural objects that enter coastal and marine environments and persist over time, where they can affect marine life and accumulate on beaches. Debris commonly found in northern Australian marine waters includes plastic bags, bottles, ropes, fishing gear, medical waste, aluminium cans, buoys and thongs. The majority of this debris comes from the land via water runoff or stormwater drains, or has been blown or washed in from coastal areas. The remainder comes from garbage illegally disposed of at sea. Oceanic currents cycling waters from nearby fishing areas make northern Australia particularly vulnerable to the impacts of marine debris. Marine debris is recognised as a Key Threatening Process affecting biodiversity conservation in Australia. In the Northern Territory it is an issue of concern for six threatened marine turtle species and at least three local dolphin species. Nets lost from fishing vessels, known as ghost nets, are a particularly serious problem and are covered in a separate management profile.

Marine debris

Photo: © Jane Dermer

Impacts

Marine debris is a problem for all marine life, including numerous threatened species. Its main impacts are though entanglement and ingestion. Marine animals, including turtles, cetaceans, dugongs, crocodiles, fish and sea birds can become ensnared in fishing lines and nets, and this can cause restricted mobility, starvation, amputation or drowning. Seabirds, marine turtles and sharks can confuse floating plastic objects for prey and ingest them, resulting in blockages in their digestive systems and internal injuries. Marine debris that washes ashore can interfere with nesting sea turtles.

Management

Marine debris is a global problem that requires constant attention. We can all play a role in its prevention by minimising use of plastic bags and disposable products, and recycling or disposing of them responsibly, particularly when boating, fishing or at the beach. People can also participate in clean-up days or just pick up rubbish wherever they see it. The remoteness of many of the coastal areas in the Top End where marine debris accumulates makes management difficult. Several sea ranger groups across the Northern Territory coast are actively surveying and cleaning up marine debris. Marine debris cleanups are coordinated by several organisations, including GhostNets Australia, Conservation Volunteers Australia, OceanWatch Australia and the Australian Quarantine Inspection Service. It may be possible for volunteers to assist on some of these clean ups.