Rockpooling destination: Revisit Seapalling, April 2014

The shore at Seapalling is influenced by a series of artificial sea defences that have changed the dynamics of the shore to produce multiple bays comprised of mobile sands with shingle berms in between.

The hard substrate is characterised by a barnacle community with periwinkles, limpets, dog whelks and beadlet anemones. The lower edges of the breakwater harbour occasional seaweeds, whilst beneath the sea defences are a network of tidal pools.

Since February certain features of the shore have changed, namely reduced strandline, decreased sand height and increased ephemeral algae.

Habitat classifications:

Substrate	LR (Littoral rock)			LS (Littoral substrate)
Habitat	HLR (High energy littoral rock)	FLR (Features of littoral rock)		LS.LSa (Littoral sand)
Biotope complex	LR.HLR. MusB (Mussel and/or barnacle communities)	Rkp (Rockpools)	Eph.FLR.Eph (Ephemeral green or red seaweed communities	LS.LSa.sh (Shingle and gravel shores)	LS.LSa.MoSa.BarSa (Barren littoral coarse sand)
Biotope			LR.FLR.Eph.EntPor (Porphyra purpurea and Entomorpha spp. on sand scoured lower eulittoral rock)

Below are images of organisms you may see whilst rock pooling in this location:

The sea defences provide an artificial hard substrate amongst the littoral sediments of the shore. The defences take the brunt of the waves.   Habitat classification: LR.HLR (High energy littoral rock) and LS.LSa (Littoral sand).

The sea defences comprise large rectangular boulders that have relatively shear faces which support rocky shore communities comprised of barnacles, limpets and periwinkles. Habitat classification:  LR.HLR.MusB (Mussels and/or barnacles in high energy littoral rock).

The littoral sediments surrounding the sea defences continually experience the dynamic forces of erosion and deposition.  Since February there has been deposition of finer sediment at the base of the sea defences at this location.

The same location as above but a few months previous shows how the sediment distributions have changed since February.

Other locations have experienced increased erosion reflected in the distribution of the barnacles. Erosion of sediment has provided new areas for settlement, resulting in a distinct barnacle size distribution. With a band of more recently settled and smaller barnacles on the recently available substrate below the more established barnacle community above. 

Variability in barnacle size gives an indication of the changing availability of substrate on the shore. Smaller, younger barnacles mark out those areas previously under sand.

The white tests of dead barnacles mark a previous height of the sand. 

Rocks covered in the dead tests of barnacles indicate that the sand was previously at a higher level, and their distribution suggest that the sand is lower than it had been when they originally colonised the rock.

Spiral wrack (Fucus spiralis) has experienced regrowth since February (see image below).

Spiral wrack (Fucus spiralis) in February.

Ephemeral seaweeds have increased in abundance and cover many of the lower shore rocks. Habitat classification: LR.FLR.Eph.EntPor (Porphyra spp.and Entomorpha spp. on sand scoured lower eulittoral rock)

Porphyra spp. occur on the sand scoured lower shore rocks.

A small coralline rockpool within the sea defences supports a number of seaweeds, limpets, and a serpulid polychaete all of which are subject to the dynamic nature of the shore at Seapalling. Habitat classification:  LR.FLR.Rkp (Rockpools).

This photo from February shows the same rock pool full of sand. 

A beadlet anemone (Actina equina) within its tentacles out within a rock pool.

A beadlet anemone (Actina equina) within its tentacles withdrawn to conserve water whilst exposed to the drying air.

A common star fish (Asterias rubens)

Examples of high energy littoral rock habitats:

In high energy littoral rock habitats organisms experience the continual pounding of waves and/or strong currents that could dislodge them at any time. Only those that are adapted to with stand the waves and resist dislodgment by strong ‘anchors’ be it large muscular feet of periwinkles or, strong holdfasts and stunted growth in seaweeds can survive. Barnacles with their own special like cement securing them to the rocks thrive and cover the available hard substrate. These barnacles are the characteristic species of high energy environments. Other organisms such as periwinkles, limpets, small mussels and the odd robust seaweed are confined to crevices or, if large enough the old test of a barnacle which provides shelter from the wave exposure.

Below are images of high energy littoral rock habitats and characteristic organisms:

High energy littoral rock can become dominated by barnacles.

 Organisms such as these limpets, periwinkles, small mussels and robust seaweeds are confined to crevices that provide shelter from the dislodging power of waves.

Limpets and mussels seek refuge within a crevice.

Small and rough periwinkles seek refuge within a crevice.

Small periwinkles seek refuge within a crevice.