Seaweeds of the Southern Irish Coast - By J. Michael Campbell - Harmful Algae
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Seaweeds of the Southern Irish Coast
By J. Michael Campbell
January 19, 2021
When I had first arrived in the coastal town of Dungarvan in Ireland’s County Waterford on Easter
Sunday in April 2012, my expectations of what the most interesting creatures that I would see were
centered on vascular plants. My first glimpse of the “Emerald Isle” as my plane landed along the
southern coast at Cork had been filled with the golden yellow blaze of gorse (Ulex europaeus) on the
hedges and hillsides, and I saw much more of that shrub on my bus ride east to Dungarvan. What I had
not anticipated was what met my eyes as soon as I disembarked from the bus by Davitts Quay at the
edge of Dungarvan Harbor, and began a short walk to the Park Hotel along the Colligan River mouth.
Gorse along the Colligan River walk (left) and seaweeds just below the high tide line at Davitts Quay (right)
Even though it was close to high-tide, I could see that the harbor-side faces of the squared limestone
walls and steps built nearly 200-years previously were gleaming with seaweed! About half of the first
twenty photographs that I took during my adventure in Ireland were of algae, not flowering plants.
Later, and as my Plant Ecology field course unfolded over four weeks, we visited beaches and rocky
shorelines, where I was delighted to find an unexpected diversity of seaweed species representing
green, red and brown algae – which were an excellent bonus to our studies of Ireland’s plant diversity.
This report contains a summary of the places visited and seaweeds found as students and I explored the
southeastern coast of Ireland during course field trips. I have had little training in marine phycology, but
have done my best to provide species identifications for the seaweeds that I photographed. My hope is
that anyone who visits these sites in the future will find the seaweeds as colorful and fascinating as I did.
For each location reported here, the seaweed pictures are organized beneath associated site
photographs according to the three main taxonomic categories of macroalgae (green - Chlorophyta,
brown – Phaeophyta, and red - Rhodophyta). I have also provided a map from Google Earth showing
the site locations, and an illustration that portrays the typical vertical zonation that seaweeds exhibit in
coastal habitats of northwestern Europe, which exemplifies how physical factors differentially affect the
microhabitats of seaweeds.
Ireland’s rich diversity of macroalgae is well
documented, thanks to the large body of
work of Dr. Michael Guiry and the National
Biodiversity Data Centre of Ireland. Guiry
(2020) maintains an excellent online
information source focusing on marine
algae, providing details about Irish and
global seaweed biodiversity and uses.
Guiry’s site provides photos and detailed
descriptions of the 250 larger macroalgae
species of the north-eastern Atlantic on the
coasts of Norway, Britain, Ireland, France,
Spain, and Portugal. The web-site also offers
a catalogue of seaweeds of New Zealand!
Area of detail
The map on the right (also a Guiry product) in Google
shows records of the number of seaweed Earth image
species reported for 10x10-km National
Biodiversity Data grid squares around the
Irish coast, with orange-red colors indicating
areas where hundreds of different species of
seaweeds are known to occur. This puts into
perspective the meager two-dozen seaweed
species represented in this report, observed
The British Phycological Society, Seaweeds of Ireland, National Biodiversity Data
during my four weeks in the country. Centre, Ireland, image, accessed 17 January 2021,
https://maps.biodiversityireland.ie/Dataset/TerrestrialSpeciesDistributionMapPrintSize/45
The habitats that I visited with my Mercyhurst students included harbor areas at Dungarvan, and sandy
beaches and rocky shores west of Tramore along the “Copper Coast.” Sites 4 & 5 are located in a gap in
5
4
3
Seaweed observation areas:
1 – Dungarvan harbor and mouth
of Colligan River
1 2 2- Clonea Beach and rocky shore
3 – Stradbally Cove beach and
rocky shore
4 – Bunmahon beach and rocky
Scale (red line) = 20 km. shore
visited were within 10x10-km grid areas included in the National Biodiversity DataCove
5 – Killmurrin map; Theand
beach Bunmahon
site lies in a gap along the southern coast where seaweed records are apparently not available in the
rocky shore
the National Biodiversity database (area of detail on map). Our seaweed sampling was not a formalized process, but more of a “random walk” along rocky shores and beaches at publicly accessible locations. At the Dungarvan Harbor/Colligan River Mouth site (site #1), the harbor wall areas were visited on multiple occasions between April 9 and 29, representing different periods in the daily tidal cycle. Site #1: Dungarvan harbor wall on the east side of the mouth of the Colligan River, south of stone bridge, showing close-up of vertical zonation of brown algae species. Photographs by J.M. Campbell. The vertical zonation of brown algae evident in the photographs from Dungarvan Harbor is consistent with the “eulittoral zone” species distribution found on the coast of Norway (see diagram below). Diagram representing of depth zonation of various species of brown (and one green) algae on the coast of Norway. Image source: Kleiven, W. 2014. Elemental Composition in various Marine Brown, Green and Red Macroalgae with respect to Season and Tissue-Age. Norwegian University of Science & Technology https://core.ac.uk/download/pdf/52102499.pdf).
1 2
3
4 5
From the upper-to-lower elevation on the wall, the seaweed species found in Dungarvan Harbor were 1- Ulva lactuca
(Chlorophyta), and brown algae (Phaeophyta) species 2- Fucus spiralis, 3- Fucus vesiculosus, 4- Ascophylum nodosum, and 5-
Fucus serratus.
On the outer harbor wall, two additional species of macroalgae were found -- both branched
filamentous forms. One was a green alga (Chlorophyta) named Cladophora rupestris, and the other was
a red algae (Rhodophyta) named Polysiphonia. These were both found in the upper littoral zone area.
Branched filamentous algae found in the outer harbor area at Dungarvan included the green alga Cladophora rupestris (left) and red (Rhodophyta) alga Polysiphonia stricta (right), growing attached to larger fronds of brown seaweed. I took hundreds of photographs of animals living in the seaweed-dominated ecosystem of Dungarvan Harbor and other sites visited on the Copper Coast. A few of my favorite big ones are shown below. A gray heron searching for fish at low tide amid seaweed (left) and pair of harbor seals (right) loafing on an exposed sand flat in the Colligan River mouth. The second site where my class observed seaweeds was on the beach and rocky intertidal zone at Clonea (Site #2). At low tide during our visit, the shallow pools in spaces between boulders on the beach were found to contain many colorful macroalgae representing all three major groups. Some macroalgae were out of the water, allowing us to see and photograph their simple root-like holdfast structures. The beach and rocky area at Clonea on the coast east of Dungarvan Bay, where students and I explored for marine life.
1 2
3 4
5 6
7 8
1- Typical Clonea low-tide pool with mixed seaweed species, 2 – Enteromorpha flexuosa (Chlorophyta), 3-8 all Phaeophyta:
3 – Laminaria digitata and holdfast (4), 5 – Fucus spiralis and holdfasts (6), 7 – Sacchoriza polyschides and warty holdfast (8).
Red algae (Rhodophyta) found at Clonea: left – Corallina officinalis, right – Polysiphonia fucoides We visited another Gold Coast location – Stradbally Cove (#3) – a few hours after the stop at Clonea. The cove is located where the Stradbally River enters the sea, and the canyon walls have sea caves! Left - Stradbally River flowing on east side of cove (past sea cave) into the ocean; right -sandy/rocky beach on west side. Additional seaweed species found at the cove included two species of brown algae and one red algae. The very long fronds of the brown algae Alaria esculenta are edible and a traditional food along the coasts of Greenland, Iceland, Scotland and Ireland. Edible brown alga (Phaeophyta) Alaria esculenta found at Stradbally Cove.
Stradbally Cove seaweeds: left – Halidrys siliquosa (Phaeophyta) and Palmaria palmata (Rhodophyta) The beach and rocky shore at Bunmahon (#4) had marine habitats similar to what we had found at Clonea and Stradbally Cove. In addition to bands of brown algae sprawled along the edge of the sandy beach exposed by the fallen tide, we discovered shallow pools of crystal-clear water amid the boulders on the shore, which seemed to favor various species of red algae dominated by Corallina officinalis. The rocky intertidal pools were rich with invertebrate life, including sea anemones and periwinkle snails (see inset photo of rocky intertidal pool below and close-up photos of rocky shore invertebrates on next page). Seaweeds are the primary producers providing organic matter for all of the life in this food web.
Corallina officinalis
Sea
anemones
Littorina
snails
Close-up photograph of red algae and invertebrates found in rocky intertidal pools at Bunmahon beach.
Encrusting invertebrates on rocks of the upper littoral zone observed at Bunmahon: Left – barnacles Balanus crenatus with a
periwinkle snail Littorina littorea, Right - common mussel Mytilus edulis, and Middle – limpets Patella vulgata
1
2
3
4
5
5 6
7
Bunmahon brown algae (Phaeophyta): 1-Laminaria saccharina, 2-Petalonia fascia, 3-Scytosiphon lomentaria, 4–Spongonema
tomentosum; red algae (Rhodophyta): 5 – Chondrus crispus, 6- Ceramium nodulosum, 7 – Nemalion helminthoides. The green
alga (Chlorophyta) Enteromorpha flexuosa is also visible in photographs 5, 6 and 7.Our last stop long the southern Irish coast was Kilmurrin Cove (#5). This was a spectacular site, with
steep cliffs and sea caves in addition to the sandy beach and rocky areas.
We found many of the same seaweed species at this location that have been reported for the other
sites. New seaweeds encountered here that we could identify included two species of red algae
(Rhodophyta). The rocky intertidal pools here contained some forms of macroalgae that I was not able
to identify, but I have included photographs of those on the final pages of the report, since they were so
beautiful. I am pleased to end this Irish seaweed story in some colorful mystery!
Kilmurrin Cove Rhodophyta: Dilsea carnosa (left) and Delessaria sanguinea (right) found plastered to a rock.
Next page: the diverse habitats and
seaweeds of Kilmurrin Cove……Seaweed “soup” in a
rocky intertidal pool
at Kilmurrin Cove
References:
Guiry, M.D. (2012). A catalogue of Irish seaweeds. Gantner Verlag: Ruggell. ISBN 978-3-905997-10-1. 250
pp.
Guiry, M.D. (2020). The Seaweed Site: Information on Marine Algae. https://www.seaweed.ie/index.php
Mac Monagail, M., & Morrison, L. (2020). The seaweed resources of Ireland: a twenty-first century
perspective. Journal of Applied Phycology, 1-14. https://link.springer.com/article/10.1007%2Fs10811-
020-02067-7
Citation for this report: Campbell, J.M. 2021. Seaweeds of the southern Irish coast.
January 19, 2011: 11 pp. accessed at http://harmfulalgae.com/You can also read
