Curious about Seagrass? 

Seagrass is a marine flowering plant that grows at various locations within the Milford Haven Waterway. Seagrass is native to the UK and, with the right conditions, can form extensive meadows. While they may look similar, seagrasses are very different from seaweeds, which are a type of algae. There are two different species of seagrass found locally: Zostera marina (common eelgrass) and Zostera noltii (dwarf eelgrass).

Benefits of Seagrass

Seagrass meadows are important habitats for many marine species. They provide protection for juvenile fish and as such are important nursery grounds; over fifty different kinds of fish have been found in UK seagrass meadows. Areas of seagrass can also help to spread and reduce water movement and wave energy, improving coastal defenses. Seagrass acts as a ‘filter’ by absorbing nutrients, chemicals and even bacteria resulting in improved water quality. 

Seagrass bed in Dale Bay

In 2020, following work with the local community and users in Dale and after consultation for the statutory marine licence processes, two hectares (approximately two rugby pitches) of seagrass (over one million seeds) were planted in Dale Bay as part of the first major seagrass restoration project in the UK. Annual monitoring has taken place since the planting, along with supplementary planting over this time, trialling new techniques and equipment.

The Seagrass Ocean Rescue Dale pilot project was a joint venture between Sky Ocean Rescue, WWF, and Swansea University, with engagement support from Pembrokeshire Coastal Forum and the Pembrokeshire Marine Special Area of Conservation (SAC) Officer.

Dale Bay was selected due to the features that seagrass requires to grow; it is a sheltered bay, with the right water quality, seabed conditions, depth, and sufficient light. Unlike other locations in the Waterway, it does not suffer from nitrate pollution at a level that would significantly impact seagrass growth. It is believed that the Bay was likely to have been home to a large seagrass meadow in the past – a small patch of naturally growing seagrass was found there in 2017, and there are a number of records in the literature of the presence of seagrass in Dale bay in the 1950’s. Some observations note that this had disappeared by the 1960’s. In fact, it is thought that the Haven Waterway has lost several historic seagrass meadows due to intensive human activity, particularly through war time and in the 1950s, which damaged them beyond repair resulting in the current fragmented patches. The plants need a critical mass to enable recovery; they need extra seeds to be planted if seagrass is to be self-sustaining, and the Dale restoration project intends to demonstrate the capacity for restoration in UK waters.

The planted seagrass area is marked with buoys. There are two green signage buoys on the Eastern boundary closest to the beach and three yellow visitor moorings on the Western boundary out near the outer pontoon. These are available as a facility for visiting boat users and are suitable for use by vessels up to a maximum length of 40 feet and maximum weight of 10 tonnes. Users are encouraged to make a donation (suggested £10 per night).

Seagrass meadows absorb carbon, storing it in their extensive root and rhizome (plant stem) systems.

Dale Seagrass Stakeholder Group members (including local community, users and statutory organisations) guide the management of the seagrass. Monitoring and planting is now undertaken by Project Seagrass and the Pembrokeshire Marine SAC Officer, with funding from the National Lottery Heritage Fund.

Human impacts on Seagrass

Seagrass is impacted by high levels of nutrients and increased sedimentation (turbidity) that reduces light levels.

Any activity that results in physical disturbance of the root system can cause long-term damage. This includes dredging and trawling and intertidal digging. Anchoring and mooring is known to impact seagrass roots and can contribute to seabed patchiness and deterioration.

An example of scouring in seagrass around moorings on the Isle of Wight (Photo credit: Anouska Mendzil)

Bottom set ropes, lines and nets can pull off seagrass shoots that become entangled, but the impact is far less than that created by chains and anchors.

UAV imagery depicting mooring scars within seagrass meadow at Seaview, Isle of Wight. (Photo credit: Anouska Mendzil)

More information

For more information on seagrass visit the Project Seagrass website www.projectseagrass.org

For more information on the wildlife of the waterway and management of the Pembrokeshire Marine Special Area of Conservation see www.pembrokeshiremarinesac.org.uk