What lies under the Sea? An update from Wicklow Aquanauts

CPFJ2W Elegant Anemone (Sagartia elegans), nice white anemone with many tentacles and brownish background, St Abbs, Scotland, UK

Report for 2020 Wicklow Aquanauts scuba diving club  Greystones as part of the National Citizen Science Marine Monitoring Scheme. This scheme has been in operation since May 2016 and Wicklow Aquanauts have now completed 69 survey dives 43 in site A,(Greystones Harbour) and 26 in site B, (Carrig Eden Bay). These records are available online at http://maps.biodiversityireland.ie/.


Scroll to the end to download a photo  guide to the marine biodiversity of Greystones produced by Wicklow aquanauts

Greystones Harbour

The biodiversity is still developing in the harbour after its reconstruction. We have as in previous years, seen top predators ,seals and conger eels. There is now a fishing boat operating out of the marina and maybe these species are supplementing their diet by scavenging bits that get dropped during unloading or washing decks. Further down the food web there is a good range of fish species represented ,dragonet, plaice, bib, ballan wrasse and  sand gobies. Crustaceans are also present and include lobsters, crabs and prawns. We were pleased this year to find a new species of sea squirt, the red sea squirt in the recesses of the harbour walls. This sea squirt attaches itself  to the wall along one side of its body. Other species commonly seen are starfish, limpets, barnacles, keel worm and the seaweeds, wracks  in abundance and feathery brown and red seaweeds. Also encrusting algae and encrusting sponges are becoming more common.

The invasive seaweed Sargassum muticum (Wireweed) has been present on the south slipway for two years and is colonising the beach. However its progress is not  as vigorous as expected as it appears it does not like warmer temperatures and  it dies back as the summer progresses. It produces large numbers of spores which drop off  and very quickly grow into new plants in spring. This plant is dense and fluffy and seems to be a good shelter for small fish. In the Wadden sea (which is off Holland) it has been planted to provide a habitat for pipe fish where sea grass has declined. We saw one pipe fish in May with what appeared to be about ten young  and then another  single adult in September .

In June we met up with the Phycology(seaweed) department of NUI Galway as part of a study on Kelp forests .We have kelp along from The Men’s to Carrig Eden and in the harbour, Due to conditions on the day the only site diveable  was the harbour where a new type of kelp was identified, wakame. This seaweed can be used in Chinese cookery.


Carrig Eden.

As yet ,we have not seen the return of scallops to this site since the scallop boats in 2018 destroyed the sea bottom with dredging.  Again as  was the case in the previous  year there was an abundant growth of feathery seaweeds in Carrig Eden bay as the summer progressed. This means that there may be some underestimation of the numbers of species present because they are hidden by the seaweed. The dahlia and beadlet anemones are still present on the rocks near the steps. A new species the elegant anemone was seen in July. This site has abundant species of crab including, hermit crabs, edible and velvet swimming crabs and occasionally a large spider crab. The commonly seen fish are bib, wrasse, plaice and dragonet, similar to what is seen in the harbour. Dog fish eggs,(mermaids purses) were seen in May. An injured dogfish was also seen in May and three healthy adults in July. A tompot blenny was seen in September.


* fewer fish in both sites than there used to be

*a reduction in the number of whelks

*brittle stars have not been seen for several years

*the shelter of the harbour has encouraged 3 species of sea squirt and occasionaly a visiting octopus.

*invasive wireweed is not as abundant as expected and provides a nursery for small fish

*LITTER, plastic bottles, drinks cans, crisp papers, plastic bags?


Ann McAvoy(BSc Applied Biology)

Scubadiver, Wicklow Aquanauts. Greystones. 05/11//2020


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