Study finds lugworm to be low on energy
Microplastic particles, measuring less than 5mm in size, have been accumulating in the oceans since the 1960s and are now the most abundant form of solid-waste pollution on Earth.
Two U.K.–based studies published in the journal Current Biology looked at whether these near–invisible, microscopic plastics that sink into mud and sand in high concentrations are causing harm to species at the base of the food chain that ingest this sediment during feeding, and play a key ecological role as a source of food for other animals.
Using the lugworm as an indicator species, the first study, from the University of Exeter, found that worms feeding in highly contaminated ocean sediment ate less and had lower energy levels. The second study, from Plymouth University, has established for the first time that ingesting microplastics can transfer pollutants and additives to worms, reducing health and biodiversity.
Ingestion of microplastics by species at the base of the food web is a cause for concern as little has been known about its effects until now. Many other organisms that have a similar feeding behaviour, such as starfish, sea cucumbers and fiddler crabs, may be similarly affected.
Lugworms are common invertebrates found widely found across the north Atlantic, living in burrows in the sand of beaches. They eat sand particles, digesting any micro–organisms and nutrients and passing the sand as waste through their tail, leaving a distinctive trail or “cast” on the beach. The worm can make up about 30 per cent of the biomass of an average sandy beach, making it an important source of food for wading birds and flatfish.
The “earthworms of the sea”, lugworms provide another important ecosystem service by turning over large volumes of sand, replenishing organic material and oxygenating the upper layers to keep the sediment healthy for other animals and microorganisms.
Microplastics can be made from polyethylene, polyethylene terephthalate, PVC or polystyrene. They are too small to be captured through existing treatment process, and wash straight into the ocean. They fall into three categories: the raw material called “nurdles” that are melted down to make larger plastic items or used as exfoliating beads in cosmetic products, or larger pieces of plastic that have degraded and broken down into smaller particles over time. Microplastics are also found as fibres and have been traced back to synthetic textiles like polyester that are used to make clothes, which can release up to 1,900 tiny fibres per garment every time they are washed.
Microplastics carry a complex mix of chemicals which have the potential to harm the worms, the research showed. Many plastics contain chemical additives, such as plasticisers, dyes, and antimicrobials, which can leach out into sediments and seawater. Microplastics also concentrate water–borne chemicals on their surfaces, such as pesticides and detergents.
There has been much campaigning around the impact of larger marine plastic pollution, with widely documented instances of fish and bird entanglement, ingestion and suffocation. But particles of this microscopic size are available to a much broader range of marine organisms, who ingest and retain these tiny plastic particles and act as prey for larger species.
The first study, by Stephanie Wright from University of Exeter, put worms into laboratory tanks of varying levels of plastics contamination for up to one month, measuring their growth, physiology, survival and ability to gain weight.
Reduced feeding also means the sediment is being reworked less, the research found. The condition of the sediment could fall, leading to a decline in the communities which live in it. A separate report, from Dr Mark Anthony Browne on work performed at Plymouth University, showed microplastics can transfer harmful chemicals to lugworms. Due to its role as a prey species, lugworms could pass these chemicals up the food chain to top predators such as fish. – © Guardian Newspapers Limited, 2013
Instances of fish and bird entanglement Lugworms can pass chemicals up the food chain
Instances of fish and bird entanglement
Lugworms can pass chemicals up the food chain