Mud and Sand

Article | Updated 9 months ago

Located between the coral and deep reefs are areas of soft sediment, such as mud and sand. In shallow waters, where there is sufficient light, seagrass meadows grow. In deeper and more turbid (muddy) waters, light penetration is reduced and consequently the number of plants is diminished. Soft sediment areas are dominated by animals that live within or burrow into the sediment (infauna), and those which move over the seabed or anchor themselves in the sediment (epifauna).

Plants and Animals of Mud and Sand Habitats

The organisms that inhabit the sediment have developed adaptations that allow them to survive. Animals that live in the sediment may project specialised body parts above the sand and draw in seawater from which they filter out tiny organisms. Other animals, known as deposit feeders, digest the organic material and bacteria that live on or in the sediment.

Plants and sessile animals that live in the mud or sand must anchor themselves to the seabed. For example, some plants possess large, mound like roots, while animals extend their bodies deep into the soft sediment. Many of the fishes that live in these habitats are dull or uniform in colour, making it difficult for predators or unsuspecting prey to see them.

Methods for Sampling Mud and Sand Habitats

Sampling of organisms that live in or around the sand and mud of the ocean floor is generally carried out with equipment that is lowered from boats. Benthic grabs are used to remove a portion of the upper layer of sediment and the animals that live within it, trawl nets are used to collect the animals that swim above the sediment, and dredges are towed over the ocean floor, collecting the organisms that live on or within the sediment, or are anchored to the sediment or rocks beneath its surface.

When the equipment is brought onto the deck of the boat, the material is washed through sieves, separating the plants and animals from the mud and sand.

Image of a dredge being hauled aboard the research vessel following a trawl run.

A dredge being hauled aboard the research vessel following a trawl run.
Image copyright Melissa Hewitt, WA Museum. 

Image of The flathead, Cymbacephalus bosschei.

The flathead, Cymbacephalus bosschei, is well camouflaged against the sediment.
Image copyright Clay Bryce, WA Museum. 

Image of Ancillista muscae burrowing into sandy sediment.

Ancillista muscae burrowing into sandy sediment.
Image copyright Clay Bryce, WA Museum.