Introduction
This page is dedicated to rockpool survey results carried out for ‘Pembrokshire Scientific Rockpools Surveys’, and ‘The Rockpool Project’ ( https://www.therockpoolproject.co.uk/ ). The purpose of these surveys is to monitor fluctuations and possible longer term changes in variety and abundance of species.
Photo-mosaics are used to record the rockpool at the time of each survey. The variety and abundance data were obtained using these photo-mosaic images rather than directly in the field (this is an experimental approach). The complete high resolution photo-mosaics can be viewed by clicking on the individual images in ‘Monthly photo-mosaics’ section below. (Further examples illustrating this technique are available on this website here. )
The specific type of rockpool selected for these surveys is described below.
The rock pool
The rockpool lies in Pwllaelod bay on the north Pembrokeshire coast. It is typical of a lot of pools in this area insofar as it is an striking pink colour. This colouration is due to a pink covering on the rocks below the water line and the presence of pink-red seaweeds within the pool itself.
Different types of rock pool provide distinct habitats and many of those around the coast of the UK and Ireland, have been classified by the Joint Nature Conservation Council (JNCC).
Under the JNCC scheme these characteristically pink rockpools are classified as;
“Coralline crusts and Corallina officinalis in shallow eulittoral rock pools”
This name is also designated, using the JNCC hierachical nomenclature, as LR.FLR.Rkp.Cor.Cor, which means; a habitat defined by Coralline crusts and Corallina officinalis (Cor.Cor) which appear as Features of Littoral Rock (FLR) in Rockpools (Rkp) in Littoral Rock (LR) (littoral rock includes bedrock, boulders and cobbles).
The key to this designation is therefore the presense of the two pink-red elements ‘Coralline crust’ and ‘Corallina officinalis’. Coralline crust is an encrusting red algae and Corallina officinalis’ a calcareous red seaweed. Both these elements are shown in Figure 2.
This type of rockpool is typically shallow and sunlit. The table below, which was taken from the JNCC website, lists some of the flaura and fauna typical of these rockpools and their relative abundances.
| Taxon | Relative importance of taxon for defining this community (%) | Typical abundance – SACFOR scale | % of core records where taxon was recorded |
|---|---|---|---|
| Corallinaceae | 27 | Abundant | 81-100% |
| Corallina officinalis | 24 | Common | 81-100% |
| Ceramium nodulosum | 7 | Frequent | 41-60% |
| Littorina littorea | 7 | Common | 41-60% |
| Patella vulgata | 7 | Frequent | 41-60% |
| Actinia equina | 4 | Occasional | 41-60% |
| Mytilus edulis | 3 | Occasional | 21-40% |
| Mastocarpus stellatus | 2 | Occasional | 21-40% |
| Ulva lactuca | 2 | Occasional | 21-40% |
| Semibalanus balanoides | 1 | Occasional | 21-40% |
| Chondrus crispus | 1 | Occasional | 21-40% |
| Cladophora | 1 | Occasional | 21-40% |
| Nucella lapillus | 1 | Occasional | 21-40% |
Rockpool N1
The specific rockpool, designated N1 (North 1), lies at the mid-shore level of the north of the bay. It is the larger of a cluster of similar pools as shown in shown in figure 3 below.
Results
Species counts from monthly survey are presented in Table 2 below along with corresponding image mosaics and more general observations and notes.
Summary
| Species | 20/07 | 08/08 | 29/08 | 01/10 | 12/10 | 12/11 | 06/12 | 01/01 | Mar | Apr | May | Jun |
| Littorina littorea | 70 | 43 | 36 | 48 | 20 | 21 | 24 | 31 | ||||
| Patella vulgata | 50 | 49 | 48 | 40 | 44 | 41 | 42 | 42 | ||||
| Actinia equina | 15 | 8 | 7 | 8 | 8 | 7 | 7 | 9 | ||||
| Gibbula umbilicalis | 3 | 5 | 9 | 3 | 0 | 2 | 1 | 0 | ||||
| Corallinaceae | ||||||||||||
| Corallina officinalis | ||||||||||||
| Ceramium nodulosum | ||||||||||||
| Mytilus edulis | ||||||||||||
| Mastocarpus stellatus | ||||||||||||
| Ulva lactuca | ||||||||||||
| Semibalanus balanoides | ||||||||||||
| Chondrus crispus | ||||||||||||
| Cladophora | ||||||||||||
| Nucella lapillus | ||||||||||||
| Aulactinia verrucosa | ||||||||||||
| Cereus pedunculatus | ||||||||||||
Monthly photo-mosaics
Notes:
01/10/22
- Mosaic processing error – additional photographs used for counts.
- Storm or rough weather since previous survey – rockpool cleaned and scoured of epiphytic growth on, e.g. coral weed. Colonies of daisy anemones visible again.
- Lots of red seaweed and laminaria strewn along beach and in rockpool. Large areas of bryzoan.
- Reduction in limpets seems to be real (e.g. reduced numbers along bottom shore)
- Questions:
- Is the scouring action of rough weather a requirement of the eco-system, i.e. like fire ir strong winds in forest habitats?
- Ho do daisy anemones attach to the rockpool bottom when covered in gravel?
Jon James 