Seagrass meadows in sheltered bays show bare patches and long curving scars where boats have anchored. The damage mechanism is mechanical and the recovery is unusually slow.
Seagrass is a rooted plant, not an alga
Seagrasses are flowering plants that colonised the sea, with true roots and horizontal underground stems called rhizomes that spread laterally through the sediment.
The meadow is largely a single connected network beneath the surface, and the visible blades are the smaller part of the organism.
That network stabilises sediment, which keeps the water clear enough for the light the plants require, so the structure maintains its own conditions.
The chain does more damage than the anchor
An anchor cuts a hole when it sets, which is a discrete injury the meadow can grow over in time.
The chain lying on the bottom sweeps a wide circle as the boat swings with wind and tide, and it scours continuously across that arc.
A single overnight stay can therefore clear a circular area many times the size of the anchor itself, and the arc cuts the rhizomes rather than just the blades.
Scars widen before they close
Once a bare patch exists, currents erode the exposed sediment at its edges and undercut the surrounding rhizomes.
Suspended sediment also reduces light reaching adjacent plants, which slows their growth exactly where regrowth would need to begin.
Recovery proceeds by rhizomes extending inward from the edges, which for slower species is a process measured in years rather than seasons.
The loss is not only the plants
Seagrass meadows are nursery habitat for juvenile fish and invertebrates, including species that support commercial fisheries in adjacent waters.
They also hold large quantities of carbon in their sediments, accumulated over long periods, and disturbing that sediment releases part of it.
Shoreline protection is a further function, since the meadow reduces wave energy reaching the beach and traps sediment that would otherwise be carried away.
Moorings solve it where they exist
Fixed moorings with a helical screw anchor and a floating line remove chain contact with the seabed entirely, allowing repeated use of one point with almost no damage.
Mooring fields concentrate boat use in designated areas, which is the same hardening logic used at busy trailheads on land.
Where no mooring exists, anchoring in sand rather than over visible grass, and using enough scope to hold without dragging, limits the area affected.