Wednesday, 9 November 2016

Rockpooling destination: Revisit West Penwith, June 2016

The rocky shore is comprised of boulders and bedrock with rockpools, crevices and gullies. Habitat classification: LR.HLR (High energy littoral rock) EUNIS: A1.1 , LR.FLR.Rkp (Rockpools) EUNIS:A1.41 and LR.FLR.Lic.(Lichens on supralittoral and littoral fringe rock) EUNIS: B3.11

The rocky shore is a high energy environment comprised of boulders and bedrock with rock pools, crevices and gullies.

The high energy environment of the shore leads to an extended lichen zone, that descends over much of the boulder field, which apart from Littorinids is relatively barren. Patches of lichens extend further down into the barnacle communities, which dominate from the upper to lower shore, inter-dispersed by shallow coralline rockpools in the mid shore, and deeper cobble filled rockpools on the lower shore. As the low tide mark is reached wave tolerant seaweeds lace the gullies.

Habitat classification:

LR (Littoral rock)
LR.HLR (High energy littoral rock)
LR.FLR (Features of littoral rock)
Biotope complex
LR.HLR. MusB (Mussel and/or barnacle communities)
LR.HLR.FR (Robust fucoid and/or red seaweed communities)
    LR.FLR.Lic.(Lichens on supralittoral and littoral fringe rock).
LR.FLR.Rkp (Rockpools)
LR.HLR.MusB.Cht (Chthamalus sp on exposed upper eulittoral rock)
LR.HLR.MusB.Sem (Semibalanus balanoides on exposed to moderately exposed or vertical sheltered eulittoral rock)

LR.FLR.Lic.Ver (Verrucaria Maura on  littoral fringe rock)
LR.FLR.Lic.YG (Yellow and grey lichens on supralittoral rock)
LR.FLR.Rkp.Cor (Coralline crust dominated shallow eulittoral rockpools)
Below are images of the organisms you may encounter in these habitats:

Among the mobile boulders and bedrock of the littoral fringe are populations of rough and small periwinkles with occasional limpets on the lower littoral. In this high energy environment organisms are confined to crevices and nooks, where they are buffeted from the full force of the waves and potential dislodgement. Habitat classification:  LR.FLR.Lic.(Lichens on supralittoral and littoral fringe rock) EUNIS: B3.11

During winter storms slabs of granite were broken away from the bedrock. Now in June this rock has not yet been colonised. 

The same area of bedrock in March 2016.

The exposed uppershore bedrock is covered in dense barnacles, with crevices jammed by mussels, anemones and coralline seaweeds. Small periwinkles occur among the barnacles, seeking shelter within the dead barnacle tests. The black lichen Lichina pygmaea forms tufts on the upper rock. All these organisms are characteristic of the biotope: LR.HLR.MUSb.CHT (Chthamalus sp on exposed upper eulittoral rock) EUNIS: A1.112. Darted among this habitat are small coralline rockpools. Habitat classification: LR.FLR.Rkp.Cor (Coralline crust dominated shallow eulittoral rockpools) EUNIS:A1.411.
Lichina pygmaea forms tufts of varying density

During the summer months rockpools experience prolific growth of ephemeral green seaweeds.
 The distribution of the ephemeral green seaweeds can be patchy.

In many cases the ephemeral green seaweeds dominate the coralline rockpools.

Ephemeral green seaweeds come to dominate many of the shallow rockpools during the summer months.

The coralline rockpools of the mid and lower eulittoral support a greater diversity of seaweeds than the upper, including Bifurcaria bifurcata, Corallina officinalis, coralinaceae crusts and ephemeral green seaweeds, along with beadlet anemones, china limpets, flat topshells and thick topshells. Habitat classification: LR.FLR.Rkp.Cor.Bif (Bifurcaria bifurcata in shallow eulittoral rockpools) Eunis A1.4113

Bifurcaria bifurcata in a shallow coralline eulittoral rockpool

Compared to March there are a greater diversity of  ephemeral and seasonal seaweeds, including Scytosiphon lomentaria.

On the sections of moderately exposed lower shore the diversity of seaweeds on the exposed bedrock also increases.
In these areas the abundance of barnacles is lower and the abundance of topshells, anemones, limpets, fucoids and red seaweeds increase. Habitat classification: LR.MUSb.Sem (Semibalanus balanoides on exposed to moderately exposed or vertical sheltered eulittoral rock) EUNIS: A1.113.

Red seaweed 'turfs' form between damp crevices and beneath overhangs.

The highest diversity of life is still found within the rockpools and on the lower shore were there is an explosion of seaweeds!

As the subtidal pools are reached the abundance of red seaweeds and kelp increase.

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