Lough Foyle Sea Grass found in Pilot survey, but extend and health are of concern
Karin Dubsky Coastwatch coordinator, with members of Celebrate Water and Foyle Rowing Club
As part of biodiversity week 2012 a volunteer search for sea grass (Zostera species) was undertaken
on Saturday 26th May around Moville Co Donegal in NW Lough Foyle. Sea grass meadows are very
valuable habitats and used as feeding and hiding place as well as fish nursery by many species.
There were old records of sea grass meadows in the area but locally only 3 people knew it.
One sea grass bed was located in 1 – 1.4 m of low water at Carnagarve, North of Moville. There were
also grass fragments seen floating on the water as signs of a possible second sea grass bed approx. 1
km south of Moville pier, just south of the viaduct . As this second site was already in the shadow of
the high wooded banks a close search will have to wait until the Foyle sea celebration in mid-June
when a second outing is planned.
Event summary
More than 30 volunteers gathered on Moville pier shortly before low tide for introductory
information about Zostera, a now scarce group of flowering grasses which live on sandy mud in the
intertidal and well lit clean shallow waters. Then 3 large rowing boats were taken out by the Foyle
Rowing Club and joined by a rib. The enthusiastic and well equipped search party ranging in age
from 9 to 70 + divided between the boats, with one group setting off as shore walkers n a northerly
direction towards the lough mouth. The water was clear with ground visibility down to 1.5 m. Those
in boats looked for sea grass fragments floating on water and into the water for signs of the bright
green grass. William Mc Elhinney, Robert Kelly and Peter White lead groups to areas where they
remembered swimming or fishing around the grass. As sea grass stands tend to be very long lived,
such known locations of sea grass meadows are the first locations to check. Stands can be monitored
over time. The rib lead the search with fast travel to historic sites, while the rowing boats did a more
systematic sweep of the whole band. Shore walkers were looking for the short Zostera noltii which
looks like a wet lawn when exposed at low tide. They also searched the tide mark for blades of the
long Zostera marina sea grass, which soon changes colour from green to shiny black when drying
out.
Results:
By the end of the event a core group of over 30 volunteers had seen the grass and could identify it as
well as the type of conditions where they might find more.
Intertidal Findings: There was no memory of the short Zostera moltii sea grass in the intertidal area
north of Moville and this was confirmed again in the 1 km searched on this biodiversity event.
Sublittoral Findings: A band of approx. 5 km near shore shallow water was searched over 2 hours by
volunteers in 4 boats working as a team. Zostera marina, the now rare long seagrass was found at
the North end of a bathing cove known locally as Carnagarve close to shore (N 5511 732 W 00700
423) This area was also teeming with small fish.
While William remembered this as a long band of ‘grass forest’ stretching parallel to the bathing
beach, the bed now located in the pilot survey was only a few meters long with more found in
patches. And it wasn’t just quantity, the state was disturbing as the long bright green grass blades
seen under water from the boats, appeared to be smothered by a Ectocarpus like seaweed. When
Brian Wingham dived down to get a sample, the brown filamentous seaweed strands were not only
growing between, but also on top of sea grass blades. This type of fast growing slimy seaweed
carpet is often associated with nutrient enrichment, e.g. at Dollymount beach in Dublin Bay.
Historic context: According to several knowledgeable locals there used to be three Zostera marina
meadows in the area searched and a further bed further towards the middle of the lough between
sandbanks. While time of decline wasn’t known, definite large scale presence was remembered on
an occasion 20 years ago. Better information on the one bed where we found the plants struggling
through the filamentous seaweed mats is available from the record of the field survey carried out by
Natura to locate the position of a sewage treatment plant outfall for Moville in 2006 (see map
appendix 1 , where they shaded an area of > 200 m .
Conclusions:
Seagrass is still present but extend and health have declined greatly in this area. Sea grass is a water
quality indicator under the water framework directive and it is important that causes for the decline
are identified and dealt with. One possible reason is nutrient enrichment. Research elsewhere has
shown that apart from physical disturbance, even moderate nutrient enrichment can cause sea grass
dieback. (Hauxwell et al., 2003) If action was taken to reduce nitrate and phosphate inputs, the
grass meadows might flourish again as research in Corsica has shown where seagrass meadows
recovered after environmental conditions improved (Agostini et al., 2002) In that context sewage
treatment is overdue and a sea outfall well outside the lough would make the largest difference.
Follow up Action: Immediate proposals:
1. Carry out a more thorough investigation of Zostera distribution in Lough Foyle, with public
participation and authorities.
2. Return to the Carnagarve bed to confirm size and status with exact measurements - possibly
during the Foyle Celebrate Water festival June 22-23. Maps and Coastwatch hand outs with
recording sheets to be distributed.
3. Identify the encroaching sea weed on the Carnagarve bed and carry out a small controlled
clearing trial, pulling the brown encroaching seaweed back by hand from an area of sea
grass1. Record method and monitor the result, with view to possible repeat or extension if
the seagrass growth is noticeably better than in algae smothered controls during 2012.
4. Research and address causes of this decline. Information on official monitoring in the Foyle
watershed has been sought. As seagrass is so close to shore and local sewage treatment is
still in the planning stage, nutrient enrichment could be one cause. Irrespective of whether it
is or just may be a factor, nutrient inputs into the lough should be controlled anyway and
run off buffers created/maintained. Nitrate sticks for members of the public to check
stream and small discharge water quality could be made available at the Water Celebration
in June.
1
This is assuming there is still local willingness to do this as I can’t see authorities allocating
manpower to it at this short notice. Permit for trial needs to be checked. I can do that with
NPWS. Is L Agency needed too?
Acknowledgements
This event was organised locally by Rose Kelly with help from Lucy White, Coastwatch
Donegal branch and the Foyle Boat Club. A very special thanks to all including the volunteers
for their survey and rowing work and the super rib scouting work by Danyy Farren and
Brian Wingham on the rib. The map appendix 1 sent by Enda Craig is greatly appreciated.
Coastwatch would like to thank the Notice Nature Fund of the National Parks and Wildlife
Service for a grant towards this biodiversity event which covered travel of the Coastwatch
coordinator, information materials and printing of the Seagrass ID and record sheets and
poster. All organised, worked and participated as volunteers.
REFERENCES
Agostini, S., Marchand, B., Pergent, G., 2002. Temporal and spatial changes of seagrass meadows in
a Mediterranean coastal lagoon. Oceanologica acta 25 (6), 297-302.
Hauxwell, J., Cebrian, J., Valiela, I., 2003. Eelgrass Zostera marina loss in temperate estuaries:
relationship to land-derived nitrogen loads and effect of light limitation imposed by algae. Marine
Ecology Progress Series 247, 59-73.
UK Technical Advisory Group on the Water Framework Directive. 2003. Guidance on
Typology for Coastal and Transitional Waters of the UK and Republic of Ireland (Final).
UKTAG 2003 WP2a (02), Marine typology Final (P2v12- 14-4-04), 28 October 2003.
Vincent, C., Heinrich, H., Edward,s A., Nygaard, K., Haythornthwaite, J. 2002. Guidance on
typology, reference conditions and classification systems for transitional and coastal waters:
CIS Working Group 2.4 (Coast). Common Implementation Strategy of the Water Framework
Directive, European Commission, 119p.
Water Framework Directive 2000/60/EC. European Communities Official Journal L327
22.12.2000, 73p.
Appendix : Natura habitat mapping at proposed sewage outfall option 2006, showing Zostera bed
then.