The shelf substrate varies greatly across the ecoregion. While sand and muddy-sand areas dominate in the Bay of Biscay, the Cantabrian Sea and Galician shelf are covered by fine sediments with isolated rocky areas in the coastal- and inner‑shelf areas, and by sand and mud in the mid- and outer-shelf. The western Iberian Shelf is characterized by sand‑sized sediments, with fine sediments forming significant mud bodies on the mid-shelf off the main rivers. In the Gulf of Cadiz, the inner shelf is covered by a sandy sediment belt with local gravels and rocky outcrops, and muddy patches in the proximity of the most important river mouths that also cover most of the mid- to outer shelf. The Gulf of Cadiz continental slope is dominated by muddy and sand sediments, depending on the intensity of the current above the seabed (Figure 9).
Figure 9: Major substrates on the shelf of the Bay of Biscay and Iberian coast (as compiled by EMODNET seabed habitats; www.emodnet-seabedhabitats.eu). Click to enlarge image.