Burrowing behaviour of the Baltic clam Macoma balthica: effects of sediment type, hypoxia and predator presence

Burial in sediment-dwelling clams is affected by morphological features, su ch as shell shape and size, but also by biotic and abiotic factors, such as predator presence, oxygen deficiency and sediment characteristics. In the Baltic Sea, oxygen deficiency is a severe problem not only in the deep basi ns, but also in the shallow coastal areas, due to eutrophication. In the sp ecies-poor Baltic Sea, the bivalve h Macoma balthica (L.) is a key species in both shallow and deep bottoms. This paper analyzes the impact of biotic and abiotic factors on the burrowing behaviour of M, balthica. Experiments were conducted to study the importance of sediment type, hypoxia, predator presence and algal mats on the burrowing behaviour (start of burial and bur ial velocity) of M. balthica. Results show that sediment type and the prese nce of the predatory isopod Saduria entomon did not affect the burrowing be haviour of M, balthica. In contrast, the burrowing behaviour was negatively influenced by hypoxia and drifting algae. Physical disturbance and oxygen decifiency are important forces that may displace M. balthica in the sedime nt and make it susceptible to predators at the sediment surface. Burial in the sediment is the only way in which infauna bivalves may escape predators , and this study shows that burrowing capability can be affected by poor en vironmental conditions.