Intertidal Monitoring Report – Sea Point, Dublin

Intertidal Monitoring Report – Sea point, Dublin

Shihan Gong

1.?? Background information of the study area

The location of study area is southeast of Dublin, close to black rock and Dun Laoghaire. I searched the satellite image, which shows two different textures of intertidal areal, rocky on the left and sandy on the right. (Google Maps, no date)

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It is a special area of conservation (SAC). The sea point is at the tail area of the conservation site, code 000210, shown in Figure 3. (NPWS, 2022)

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May observe lugworms (Arenicola marina) and cockles (Cerastoderma edule) and other bivalves, which are relatively common in the sandy flats. Additionally, other annelids and bivalves may also occur in the sandy environment of the area (NPWS, 2015).

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In the rocky areas of South Dublin Bay, a variety of brown algae mainly grow in the intertidal zone of the rocky shore, such as Fucus spiralis, F. vesiculosus, F. serratus, Ascophyllum nodosum, and Pelvetia canaliculata, are typically found. Apart from brown algae, other seaweeds and green algea suitable for rocky coastlines may also be present. Moreover, the rocky areas may harbor certain mollusks and organisms adhering to the rocks (NPWS, 2015).

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2.?? The description of Field work

We placed quadrats at three locations along the rocky shore: low shore, mid shore, and upper shore. Additionally, we positioned cores at low shore, mid shore, and upper shore of the sediment shore. At each location, we sampled five times using a circular array method.

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At Seapoint Beach, the western side is characterized by a rocky intertidal zone that grades into more rocky area with lager size of bedrock near the water. The higher intertidal zone includes patches of sand and pebbles, over which a substantial coverage of seaweed is established. This seaweed coverage contains scattered pools that support various marine organisms, indicative of regular tidal submersion. The eastern side features a sedimentary shore composed predominantly of fine sand and mud. This site, located on the southeastern margin of Dublin Bay near Dún Laoghaire Harbour, has a bathing area with reduced wave action, conducive to water-based activities.

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On the field trip conducted on March 4th, the observed tidal range with a high tide of 3 meters and a low tide of 1.7 meters, resulting in a tidal range of 1.3 meters. The dominant wind direction within Dublin Bay, illustrated in Figure 4, is responsible for a fetch of approximately 7700 mm, as shown in Figure 5. A freshwater outflow into the bay was also documented, albeit with minimal discharge volumes. This outflow may be partially attributed to recent precipitation events. The concrete pathway beneath the dam is overgrown with moss, indicating that the area is routinely moistened by freshwater.

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3.?? The Survey

Our three quadrats were set at elevations of 0m, 0m, and -0.45m, as displayed in Figure 6. The dominant habitat encountered during our survey on the beach was very sheltered mid eulittoral rock with a prominent presence of Ascophyllum nodosum.

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The upper shore quadrat shows in figure 8, located at coordinates 53.298352, -6.161115, has a substrate composed of a mix of rocks and pebbles. Approximately 50% of the observed coverage here consists of brown algae adhering to the rocks.

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The mid-shore quadrat shows in Figure 8. It was positioned at coordinates 53.2983892, -6.1610559. It was almost covered by the algae adhering to the rocks and pebbles.

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The lower shore quadrat, shown in Figure 9, was positioned at coordinates 53.2987541, -6.1609221. It has algae attached to the large bedrock, visually estimated to cover about 30%. The occurrence of small stones and grains of sand here is noticeably less than on the upper shore.

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4.?? The Laboratory

For the Gammarus locusta identification, we began by classifying the sample shows in figure 10 within the Arthropoda phylum due to its jointed appendages and then more narrowly within the Amphipoda order, characterized by small, laterally compressed bodies and a seven-paired-legged thorax. Observing that the creature’s eyes were proportionally small, its first and second uropods lacked significant apical partitions, we categorized it as a Gammaridea. Specific traits such as the relative size of the third uropod’s inner branch and its distinctive kidney-shaped eyes, along with the features of the seventh pereopod, led us to identify it as Gammarus locusta (Hayward and Ryland, 2017).

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Figure 10. The sample of Gammarus locusta

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In the case of Actinia equina, we identified the sample shows in figure 11 as part of the Anthozoa class, known for their fixed presence on hard surfaces and tentacle arrangement around a central mouth. Further analysis within the Hexacorallia subclass, which are solitary organisms with a single type of tentacle, allowed us to classify it as part of the Actiniaria order. The absence of a hard skeletal structure, the solitary nature of the polyp, and the three rings of tentacles helped narrow the identification. The specific number of unmarked tentacles, the blue acrorhagi at its base, along with the size and smoothness of the column were key in confirming it as Actinia equina, commonly known as the beadlet anemone also has other color as blue grey (Hayward and Ryland, 2017).

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The identification of Ascophyllum nodosum shows in Figure 12 was achieved with the help of the Seasearch Guide to Seaweeds of Britain and Ireland (Bunker et al., 2010), specifically within the Phaeophyceae, or brown algae, section. The process began by considering a variety of algae species, then meodically eliminating those that didn't match the observed characteristics. The key identithfying features focused on were its size, with lengths between 30 to 150 cm and width up to 1 cm, the presence of irregular dichotomous branching, distinctive bladders, a leathery texture, and an olive coloration.

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5.?? Data processing

The rocky shore at our study site within Dublin Bay has been classified as littoral rock (and other hard substrata) due to the presence of large bedrock and pebble environments. This location is characterized by low wave exposure, leading us to categorize it as a low-energy littoral rock area.

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JNCC Classification:

In a one-square-meter quadrat of the upper shore, we observed a diverse biota including Fucus spiralis at 27.8% coverage, Ascophyllum nodosum at 26.4%, Ulva intestinalis commonly at 11%, frequent sightings of Littorina littorea, and the presence of Gammarus locusta. The substrate in this area is composed of a mix of large rocks and small pebbles. Consequently, we have delineated the area surrounding the quadrat (Figure 13) as divided between Fucus spiralis on sheltered upper eulittoral rock (LR.LLR.F.Spi) and Ascophyllum nodosum on very sheltered mid eulittoral rock (LR.LLR.F.Asc).

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The mid shore quadrat has the same physical environment with the upper shore quadrat. We found Ascophyllum nodosum (91.5%) shows in Figure 14, Ulva intestinalis (12% - Common), Rhodothamniella floridula (2% - Occasional), Semibalanus balanoides (Common), Patella vulgata (Abundant), Actinia equina (Frequent), Littorina littorea (Frequent), Nucella lapillus (Frequent) in this quadrat. So, we identify the area surrounded this quadrat as Ascophyllum nodosum on very sheltered mid eulittoral rock (LR.LLR.F.Asc).

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In the lower shore zone (Figure. 15), we discovered substantial bedrock and boulders. Moreover, in the assessment of the lower shore quadrat, we identified a 67.6% coverage of Fucus spiralis. Beneath it, there are some small pounds have some creatures in it, and we found Rhodothamniella floridula (5% - Frequent), Polysiphonia lanosa (2% - Occasional), Patella vulgata (Abundant), Actinia equina (Common), Semibalanus balanoides (Super-abundant), Littorina littorea (Common), and Nucella lapillus (Frequent). Consequently, we classified the area around the lower shore quadrat as Fucus vesiculosus on moderately exposed to sheltered mid eulittoral rock.

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Color-coded map:

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https://earth.google.com/earth/d/1RhZwV9xYvsUmiVBlPEogI3x1oo8ee-vr?usp=sharing

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6.?? Bibliography:

Bunker, F.S.D. et al. (eds) (2010) Guide to seaweeds of Britain and Ireland. s.l: Marine Conservation Society (Seasearch guide).

Dublin 2022, ?NPWS (Ecological Data Management) (2022) The Status of EU Protected Habitats and Species in Ireland, ArcGIS StoryMaps. Available at: https://storymaps.arcgis.com/collections/1a721520030d404f899d658d5b6e159a (Accessed: 8 March 2024).

Google Maps (no date) Google Maps. Available at: https://www.google.com/maps/@53.2983084,-6.1590799,528m/data=!3m1!1e3?entry=ttu (Accessed: 8 March 2024).

Hayward, P.J. and Ryland, J.S. (eds) (2017) Handbook of the Marine Fauna of North-West Europe. Oxford University Press. Available at: https://doi.org/10.1093/acprof:oso/9780199549443.001.0001.

Seapoint, Dublin, Ireland Wind, waves and weather forecast (no date) WINDY.APP. Available at: https://windy.app/zh/forecast2/spot/570917/Seapoint+Dublin+Ireland (Accessed: 9 March 2024).

‘SITE SYNOPSIS.pdf’ (no date). Available at: https://www.npws.ie/sites/default/files/protected-sites/synopsis/SY000210.pdf (Accessed: 8 March 2024).