DLR Biodiversity Marine Project

Our Reef Surveys

Reefs are rocky marine habitats or biological concretions that rise from the seabed. These range from vertical rock walls to horizontal ledges, sloping or flat bed rock, broken rock, boulder fields, and aggregations of cobbles.

They can occur in the subtidal (under seawater) but may extend into the intertidal zone, where they are exposed to the air at low tide.

Reefs are characterised by communities of attached algae such as seaweeds (where there is sufficient light – on the shore and in the shallow subtidal) and invertebrates, usually associated with a range of mobile and sessile animals, including invertebrates and fish such as starfish and sponges.

Reefs are very variable in form and in the communities that they support. Two main types of reef can be recognised: those where animal and plant communities develop on rock or stable boulders and cobbles, and those where structure is created by the animals themselves (biogenic reefs).

The reef areas in our seawaters were surveyed in 2021 and 2022 by marine biologists as part of our actions of our DLR County Biodiversity Action Plan 2021 – 2025. The reefs that stretch along our coastline are significant, especially in the context of the relatively low extent of this habitat on the east coast of Ireland and very low level of detailed surveys previously carried out.

The surveys indicate that a significant area of the EU Annex I (1170) reef habitat is present off the coastline of Dún Laoghaire Rathdown County Council with an interesting and diverse suite of faunal and algal communities.

During the reef surveys our marine biologists encountered lots of marine creatures including a grey seal and pup playing in the water. Please read the reef report below.