Lebensspuren and mullspuren: Drifting plastic bags alter microtopography of seafloor at full ocean depth (10,000 m, Philippine Trench)

Tracks, trails, burrows, faecal castings and other sedimentary structures made by organisms on the deep-seafloor, known as Lebensspuren, form a natural and significant component of the microtopography at the sedimentwater interface. These structures are often more conspicuous than the errant organisms responsible for them, particularly at hadal depths (>6000 m). Recent explorations of the deepest places in the oceans have revealed the occurrence of long, often parallel tracks running in unnaturally straight lines along the trench floors, erasing lebensspuren. During a crewed submersible dive to 10,000 m deep in the Philippine Trench (west Pacific Ocean), the source of these features was confirmed to be the result of plastic bags drifting in the near-bottom currents. During the 90 min transect of the trench floor, nine individual bags were observed compared to only one benthic holothurian. Assuming the bags are drifting at similar speeds to the current, these tracks, documented here for the first time, that we have coined mullspuren are forming up to 12 times faster than hadal holothurians create lebensspuren. The area affected is also much larger as the tracks laid down by plastic bags often consist of multiple, parallel gouges with smoothed intermediate sediment. The ecological effects of particle perturbation and the erasing of lebensspuren is unknown but is becoming ubiquitous at the deepest points in our oceans.

Automated summary

Recent studies have found long, parallel tracks running along the trench floors in the deepest places of the ocean, caused by drifting plastic bags, referred to as mullspuren. These tracks created by plastic bags are forming up to 12 times faster than those created by hadal holothurians, with a larger affected area.