Plastic resin pellets are not readily observed or found. First they are very small and look very much like similar sized natural debris on the beach such as shell, pumice grains, sargassum floats and large grains of quartz. They are opaque and blend into the sandy background. Pellets can also appear seasonally, showing up for example on the West coast of West Australia after the first cold fronts in winter and slowly disappearing in late spring as the beach conditions change. Equally they are not an every day object and to observe them you need to tune in to their appearance.
Season’s for Marine Debris
In some regions plastic resin pellets appear and disappear on a seasonal basis. The Onshore Season defines the time when predominant wind and surface water movement moves debris into the coast and strong sustained winds drive it onshore. On the West coast of Western Australia this happens in winter and early spring. The Offshore Season defines the time of year when the predominant wind and surface water movements tend to move marine debris away from the coast. On the West coast of Western Australia this happens in summer and autumn. Coasts which are not west facing and regions other than temperate regions will have additional and or different onshore and offshore conditions related to the movement of marine debris. We hope to be able to provide information about other coasts and regions as the programme develops.
Where to Look for Plastic Resin Pellets
- Tidemarks (Tide lines or strand lines) when these are populated with natural debris and some seaweed. Older tidemarks especially higher up on the beach are worth checking. Checking the newest tidemark will indicate whether pellets are being washed ashore.
- Seaweed wracks when cast ashore can contain significant hidden debris including pellets. When the wrack breaks down the debris is exposed. Remnant wracks are worth checking.
- Rubble deposits caught between rocks or in depressions often contain pellets.
- Vegetation at the base of dunes and within the range of the wave reach will trap pellets and larger debris.
- Drain and creek entry points on the beach will trap rubble amongst the vegetation along their sides during high tides and heavy swell and can hold pellets.
- Favourable beach conditions include flat low energy beaches having some direct exposure to the onshore wind and water conditions.
- Rocky features or more significant geographical features which interrupt the longshore movement of water and debris can form pockets where significant amounts of debris are trapped. When this happens consistently from year to year these are termed marine debris hotspots. Plastic resin pellets can occur in these sites in high numbers.
Marine Debris Hotspots
These are sites which accumulate significant amounts of marine debris every year. Common items in large numbers found at these sites are plastic fragments, plastic lids and plastic resin pellets – items which are more mobile and hence not held easily on long open beaches. This debris has generally migrated both from another part of the coast and from offshore. Hotspots are small beach areas facing upstream to the longshore movement and are formed by rocky features, heads, headlands etc jutting out from the beach. Hotspots can also occur in small bays which are situated to trap incoming debris.
Marine Debris Rafts
Marine debris can become concentrated in gyres and eddy’s which form in nearby ocean currents such as the Leeuwin Current off Western Australia. Rafts of this debris can break free of the current and remain intact as it is blown ashore. A large deposit of marine debris on a rocky or open sandy beach is likely to be a raft which has come ashore. Contact us if you come across one of these as they represent an accurate sample of open ocean debris and are worth sampling.