The effects of sudden sediment burial on juvenile green-lipped mussels

Accelerated human-driven sedimentation is a significant stressor for bivalves and has been implicated in the lack of recruitment and recovery of New Zealand green-lipped mussels (Perna canaliculus). In June 2024, the short-term effects of sediment burial on juvenile green-lipped mussel behaviour, growth, and survival were assessed. Juvenile mussels (1.4 ± 0.01 mm shell length) provided by SpatNZ Ltd were buried with a 1 mm layer of < 63 μm silt–clay sediment for 4–8 days. Mussel crawling behaviour, growth, and survival were compared with non-buried control mussels. Movement away from the starting position was more common in smaller mussels, and very few left the sediment substrate (5%) in either treatment. Sediment burial impacted the ability of mussels to grow, with significantly lower mean growth in the buried mussels (1.90 ± 0.02 mm) compared with non-buried mussels (2.10 ± 0.02 mm) after 8 days. On average, the burial-related mortality of juvenile mussels reached 41.5 ± 3.2% after only 4 days in the burial treatment, significantly higher than in the control (32.5 ± 2.2%). Overall, the mortality was more pronounced among smaller mussels, a difference that increased with burial duration. This study demonstrates that juvenile green-lipped mussels are intolerant of high-sediment environments relative to other bivalves, which may help explain the low settlement and recruitment currently observed in coastal New Zealand.