Edited sentences: modifies, approximately

Living infaunally within the uppermost sediment horizon M. senhousia profoundly modifies the physical environment because it lives inside byssal cocoons which may fuse to extended mats when approximately 60% of the available sediment surface are occupied by byssal bags.

M. senhousia profoundly modifies the physical environment
M. senhousiaは物理的環境を大きく改変する

approximately 60% of the available sediment surface are occupied
利用のできる底質の約60%が覆われている