Numerous Sublinear Sets of Holes in Sediment on the Northern Mid-Atlantic Ridge Point to Knowledge Gaps in Understanding Mid-Ocean Ridge Ecosystems

On 13 July 2004, during an expedition exploring biodiversity along the northern Mid-Atlantic Ridge, ROV dive recorded videos of numerous sublinear sets holes in sediment at ca. 2,082 m depth. The location was north Azores. Each set appeared track-like. Lengths individual series ranged from < 1 to many meters. straight or gently curved. Some intersected crossed. Close examination showed them be elongate, with long axis parallel series. were 6 × 1.5 cm, distance between similar hole length. that most recently formed each surrounded by raised sediment. Holes older partly filled and surrounding less obvious. Overall, these lebensspuren created small-scale heterogeneity local soft-bottom benthic ecosystem. source how they constructed is unknown, but may indicate excavation infaunal organism digging removal e.g., a feeding appendage large epifaunal animal. None our closeups any sign living organisms inhabiting holes. Whether connected beneath surface not visible. traces observed are reminiscent ichnofossils reported deep marine facies. We hope future studies we report here will resolve mystery what them.