Rockpooling Destination: Porthgwara, March 2016

The rockyshore comprises sand scoured boulders and bedrock with rockpools. Habitat classification: LR.FLR.Lic (Lichens on supralittoral and littoral fringe rock), LR.HLR.MusB (Mussel and/or barnacles communities), LR.FLR.Rkp (Rockpools) and LS.Sa (Littoral sand).

The rocky shore is comprised of large boulders and bedrock that experience alternating variations in sand scour from the surrounding sandy shore. As a result barnacle cover is low and scour tolerant seaweeds thrive in the shallow sand filled rockpools. Between the boulders are limpets, periwinkles, topshells and dog whelks together with patches of seaweed.

Below are images of some of the organisms you may encounter whilst rockpooling on the shore:

Yellow, grey and black lichens cover the supralittoal and littoral fringe rock. Habitat classification: LR.FLR.Lic (Lichens or small green algae on supralittoral and littoral fringe rock) EUNIS: B3.11.

Much of the rock of the littoral fringe/ upper shore is covered in patches of green algae/lichen that in some instances has overgrown the barnacles. The remainder of the rock is colonised by sparse barnacles, limpets, rough periwinkles and small periwinkles. 

Rough periwinkle (Littorina sp)

Barnacle, seaweed and general epifaunal cover is patchy among the boulders of the shore that are subject to rolling and sand scour; both of which limit the barnacle communities expansion. LR.HLR.MusB (Mussel and/or barnacle communities) EUNIS A1.11.

A limpet is buffeted from the waves by a small outcropping ridge on the boulder.

Seaweeds such as, Cladophora rupestris, Corallinaceae crusts and reds seaweeds occur in shaded damp enclaves between the boulders.

The rockpools of the shore hold the greatest diversity of fauna and seaweeds. Shallow sand filled coralline rockpools are encrusted by coralline seaweeds (Corallinacea crusts and Corallina officinalis), those that are more sheltered have less sand and support more anemones (Actinia equina), china limpets (Patella ulyssiponensis) and thick topshells (Osilinus lineatus) together with sand tolerant seaweed species.

The cover of fucoids and robust red seaweeds increases in and around rockpools and on bed rock of the lower eulittoral. Comprising a red seaweed under-story  of species such as,  Corallina officinalis, Mastrocarpus stellatus and Geldium sp. beneath a fucoid canopy.

A flat periwinkle on Fucus sp

The sand filled rockpools of the lower shore also support a diversity of sand tolerant seaweeds. Habitat classification: LR.FLR.Rkp.SwSed (Seaweeds in sediment filled rockpools) EUNIS: A1.413.

With increased quantities of sand, epifauna decrease and seaweeds, especially sand tolerant species, increase and include Chondrus crispus, Ceranium sp, Clodrophora sp, Sargassum muticum, Bifucaria bifurcata, Rhodothamniella flordula.

Sargassum muticum and sand tolerant seaweeds.

The requirement for seaweeds to withstand smothering is key within these rockpools.