Rock Pooling: Littorina compressa var. nigrolineata

Wednesday, 29 July 2015

Rockpooling destination: Pendeen, Cornwall April 2015

The shore comprises a sandy bay flanked by outcropping bedrock and cliffs.

The exposed shore is characterised by an extended lichen zone that reaches up the cliffs to form distinct bands of yellow and grey lichens and below the black, tar lichen. Periwinkles occur across the shore and barnacle communities dominate scour free rocks of the mid and lower shore, whilst sand scoured rocks are barren or, support organisms within the rock crevices.

Habitat classification:

Substrate	LR (Littoral rock)				LS (Littoral substrate)
Habitat	LR.HLR (High energy littoral rock)		FLR (Features of littoral rock)		LS.LSa (Littoral sand)
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 rock)
Biotope			LR.FLR.Lic.Ver (Verrucaria maura on littoral fringe rock)	LR.FLR.Lic.YG (Yellow and grey lichens on supralittoral rock)

Below are images of organisms you may encounter whilst rockpooling within these habitats:

The shore comprises sand flanked by bedrock outcrops and cliff. Habitat classification: LS.LSa (Littoral sand) EUNIS A2.2 and LR.HLR (High energy littoral rock) EUNIS A1.1.

High wave exposure leads to an extended splash zone enabling lichens to colonise further up the cliffs. Two distinct bands of differing lichen communities can be seen. At the highest position on the supralittoral are yellow and grey lichens, whilst on the littoral fringe below black tar lichen (Verrucaria maura) covers the bedrock. Habitat classification: LR.FLR.Lic.YG (Yellow and grey lichens on supralittoral rock) EUNIS: B3111 and LR.FLR.Lic.Ver (Verrucaria maura on littoral fringe rock) EUNIS: B3.113.

Rough periwinkles (Littorina spp) are the dominant motile species of the Verrucaria maura biotope.

Littorina spp

A turf forming Rhodophyta

Sand scour tolerant ephemeral green and red seaweeds occur sporadically at the rock bases.

Small periwinkle (Melarhaphe neritoides)

Rough periwinkles (Littorina spp) and Small periwinkles (Melarhaphe neritoides)

Patella vulgata

Patella vulgata huddle in the leeward corner of the rock.

Barnacles occur at low abundance on the upper shore.

Barnacles and Small periwinkles (Melarhaphe neritoides).

Barnacles

Barnacle abundance increases on the mid and lower shore. Note that on these sand surrounded boulders, sand scour prevents further downward colonisation of barnacles. Habitat classification: LR.HLR. MusB (Mussel and/or barnacle communities) EUNIS A1.11.

Barnacles of the mid shore.

Common blue mussels (Mytilus edulis) occur within rock crevices.

The rough periwinkle, Littorina compressa var. nigrolineata occurs amongst the barnacles of the mid and lower shore.

Barnacles and M. neritoides

Else where sand scour is too prolific to enable sessile organism to grow.

In such conditions, organisms are restricted to the crevices.

M. edulis and robust fucoids grow within boulder crevices.

Barnacles, P. vulgata and M. edulis.

M. edulis

Serrated wrack (Fucus serratus) and red seaweeds grow from crevices of the lower shore boulders. Habitat classification: LR.HLR.FR (Robust fucoid and/or red seaweed communities) EUNIS: A1.12.

F. serratus

Below the F. serratus understory are a variety of robust red seaweeds.

Mastrocarpus stellatus and F. serratus

A boulder of the lower shore has become covered by sand, to reveal just the tops of the F. serratus.

Thursday, 2 July 2015

Rockpooling Destination: Revisit Land's End Peninsular April 2015 - Littoral fringe, barnacle communities and coralline rockpools

Steep cliffs surround the bay, the lower craggy edges covered in lichens. The cliff bases and steeper bedrock transition between the lichen and barnacle communities with limpets, periwinkles and whelks. Boulders and bedrock of the mid and lower shore host a similar barnacle community plus a variety of seaweeds, including where sand scour is event, ephemeral seaweeds. Rockpools occur throughout the shore, and a river flows downs from the cliffs.

The bay experiences a dynamic regime, alternating between periods of erosion and deposition. The underlying substrate is boulders and bedrock, however, variable amounts of sand may be deposited on top, sourced from the sand bar situated offshore. The communities encountered reflect the alternation between these regimes.

The shore alternates between periods of deposition, sandy and erosion, stony.

April 2015

September 2013 January 2014
The overlaying sand has been eroded to reveal the boulders beneath.

At the time of visitation the cove was comprised of boulders and bedrock with an occasional thin veneer of sand.

Habitat classification:

Substrate	LR (Littoral rock)
Habitat	LR.HLR (High energy littoral rock)	LR.MLR (Moderate energy littoral rock)		LR.FLR (Features of ilttoral rock)
Biotope complex	LR. HLR.MusB (Mussels and/or barnacles on high energy littoral rock)	LR.MLR.BF (Barnacles and fucoids on moderately exposed shores)		LR.FLR.Lic.(Lichens on supralittoral and littoral fringe rock).	LR.FLR.Rkp (Rockpools)		LR.FLR.Eph (Ephemeral green or red seaweed communities		LR.FLR.CvoV (Littoral caves and overhangs).
Biotope		LR.MLR.BF.Fser (Fucus serratus on moderately exposed eulittoral rock)	LR.MLR.BF.Rho (Rhodothamniella floridula on sand scoured lower eulittoral rock)	LR.FLR.Lic.Ver (Verrucaria Maura on littoral fringe rock)	LR.FLR.Rkp.Cor (Coralline crust-dominated shallow eulittoral rockpools)	LR.FLR.Rckp.SwSed (Seaweeds in sediment- floored eulittoral rockpools).	LR.FLR.Eph (Ephermeral green or red seaweeds (Fresh water or sand influenced)	LR.FLR.Eph.EntPor (Porphyra purpurea and Entomorpha spp. on sand scoured mid to lower eulittoral rock)
Sub Biotope		LR.MLR.BF.Fser.R (Fucus serratus and red seaweeds on moderately exposed lower eulittoral rock)			LR.FLR.Rkp.Cor.Cor (Corallina officinalis and coralline crusts in shallow eulittoral rockpools)

Bedrock and boulders of the upper shore. A year ago theses were covered by sand, now they are slowly being colonized by fauna, many of whom appear to have moved down from the previously bare rock. Small periwinkles (Melarhaphe neritoides), Rough periwinkles (Littorina sp) and limpets occur on bedrock outcrops, whilst rockpools and boulders are becoming colonised by ephemeral greens.

The assignment of habitats to such shores can be difficult as the species present represent transitional communities that have not yet attained a stable species/ abundance relationship upon which classical biotope classification systems are based. This highlights the importance of long term monitoring of shores when conducting phase 1 habitat surveys, as the habitats found can change.

Below are images of organisms you may encounter whilst rockpooling within the littoral fringe and upper to mid shore habitats:

These photographs show the increase in ephemeral green algae cover on rocks between October 2014 and April 2015.

Periwinkles occur on the shore and are one of the most prominent mobile fauna of the littoral fringe and upper shore.

Melarhaphe neritoides

Littorina spp and M. neritoides and sparse barnacles on the littoral fringe cliff edge.

Rough periwinkles (Littorina spp) and limpets (Patella vulgata) have begun to recolonise upper shore boulders that were previously covered by sand.

Similarly upper shore bed rock is being recolonised by limpets (Patella vulgata)

The cliff bases enable organisms to move up and down in response to the sediment regime and sand scour, as a result they support more stable barnacle communities with limpets, periwinkles, mussels and whelks. In the case of limpets the spray from the waves of this high energy shore, enable them to live far up the cliff base.Habitat classification: LR.HLR.MusB (Mussels and/or barnacles on high energy littoral rock) EUNIS: A1.11.

The base of the cliffs are hollowed by the grinding of the boulders. An indication of the high wave exposure experienced by organisms on this shore.

Barnacles and small periwinkles (Melarhaphe neritoides) cover the bases of the cliffs.

The cliff bases hold a number of small coralline rockpools that support corallinaceae crusts, limpets and red seaweeds. Habitat classification: LR.FLR.Rkp.Cor (Coralline crust-dominated shallow eulittoral rockpools) EUNIS: A1.411

A coralline rockpool with red seaweeds and limpets.

The distribution of fauna in the upper and mid shore is influenced by wave exposure, subtidal sand scour, fresh water runoff and desiccation. Where the upper shore is not influenced by fresh water run off, barnacle communities similar to that of the cliff bases cover the boulders. Habitat classification: LR.HLR.MusB (Mussels and/or barnacles on high energy littoral rock) EUNIS: A1.11.

Barnacles

A limpet (Patella spp)

Barnacles and Littorina compressa var. nigrolineata.

Dog whelks (Nucella lapillus), Limpets (Patella spp) and barnacles.

Barnacles and Patella depressa

Verrucaria mucosa

Some boulders are smooth and uncolonised by fauna.

Rock Pooling Etiquette

Rock pooling is a fun and fascinating activity and it is important to respect the marine organisms you encounter.

The best time to go rock pooling is at low tide when the intertidal zone is exposed. The intertidal zone is the area of the shore that is covered and exposed by the sea as it rises and falls. It experiences daily fluctuations in environmental conditions and the creatures that live there will have
positioned themselves to reduce the extremes they must endure. Therefore it is important to return creatures to the place that you found them and to return any boulders or seaweeds you may have overturned in your pursuit.