Rockpooling Destination: Revisit Hemsby, March 2016

The intertidal sediments experience periods of erosion and deposition which in turn influence the sediments and organisms found or washed up on the shore.



In March the strandlines separate in to an upper, comprised of bryozoa (predominantly Flustra foliacea) and a lower, comprised of red seaweeds (predominantly combweed, Plocamium sp).

The sediments of the shore in March, comprise coarser elements than during the summer.

March 2016

The shore in Summer, 2014



Characterising species of the littoral fringe rock

           

The littoral fringe zone occurs between the supralittoral and eulittoral zones and in some cases is considered a terrestrial habitat i.e. within the EUNIS classification it is placed with the coastal habitats and the supralittoral and littoral fringe lichen communities come under the one broad habitat complex, Lichens or small green algae on supralittoral and littoral fringe rock B3.11. 

The littoral fringe receives the salt spray from the waves, as such, those shores experiencing greater exposure and salt spray from waves have larger littoral fringe zones. Rock altitude, angle, shade and local climate also influence the extent of the zone. These factors also effect the distinction between the supralittoral and littoral fringe communities so that sometimes they are distinct or are intermingled.

The littoral fringe zone is often characterised by rocks covered in the black tar lichen (Verrucaria maura), rough periwinkles, channel wrack, ephemeral seaweeds, sparse barnacles and pools with variable salinity and temperatures. 

Other organisms that come under the broad lichen habitat complex (LR.FLR.Lic) that are also characteristic of littoral fringe communities are green seaweeds such as Blidingia sp, Ulothrix sp and Urospora sp that can characterise areas of littoral fringe soft rock or vertical rock where there is fresh water run off. 

The organisms living in this zone are highly specialized to endure variable salinity and extended periods of air exposure.  

The littoral fringe can often be discernible from a distance by the presence of the black tar lichen (Verrucaria maura) that covers the rock, above which the rocks of the supralittoral appear light grey whilst below the rocks of the eulittoral appear beige.

High wave exposure leads to an extended splash zone enabling lichens to colonise further up the cliffs. In the photograph above 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 V. 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.

Variations in rock altitude can lead to a mosaic like distribution of the supralittoral and littoral fringe lichen communities. Also at this altitude on the shore fluctuating temperatures and salinity lead to prolific growth of Ulva spp (formally Entomorpha spp) in some of the rockpools. Habitat classification: LR.FLR.Lic.YG (Yellow and grey lichens on supralittoral rock) EUNIS: B3111, LR.FLR.Lic.Ver (Verrucaria maura on littoral fringe rock) EUNIS: B3.113 and  LR.FLR.Rkp.G (Green seaweeds (Entomorpha spp. and Cladophora spp.) in shallow upper shore rock pools) EUNIS: A1.421. 

The lichen communities are not always present on unstable rock substrates, and this can make the distinction between the the supralittoral and littoral fringe difficult. On the shore above the supralittoral and littoral fringe rock is distinguishable by its 'white colour' as these boulders do not experience daily submergence. The yellow and grey lichens of the supralittoral are able to grow on the boulders of the most upper shore that have been thrown up during storms and are only rolled during the most extreme storms, however the remaining boulders of the supralittoral and littoral fringe are rolled just enough during periodic storms to prevent their growth.

On the shore above the boulders are larger and more stable allowing for a more established and diverse lichen community to develop. The black tar lichen (V. maura) is still absent from many of the boulders that would occupy the altitude of the littoral fringe but does occur on the bedrock of this height. On the boulders where the V. maura is absent the littoral fringe is identified by the presence of other organisms, including rough (Littorina saxatilis) and small periwinkles (Melarhaphe neritoides) and sparse barnacles. The ineffective application of the JNCC and EUNIS habitat classification to the littoral fringe boulder habitat is rectified by the much broader 1993 phase 1 habitat classification which seems to capture these environments under the boulder habitat classification which is in turn listed under the EUNIS website as comparable to the habitat classification supralittoral rock (lichen or splash zone).

On stable bedrock the black lichen, V. maura is one of the most characteristic species of the littoral fringe. Living among this lichen you may also encounter L. saxatilis, ephemeral seaweeds and sparse barnacles. Because of the extended period of exposure the organisms tend to aggregate in crevices or shaded areas in order to reduce desiccation. The rockpools of the littoral fringe are species poor. Fluctuating temperatures and salinity lead to prolific growth of Ulva spp (formally Entomorpha spp) in some of the rockpools whilst others support the occassional amphipod. Habitat classification: LR.FLR.Lic.Ver (Verrucaria maura on littoral fringe rock) EUNIS: B3.113 and  LR.FLR.Rkp.G (Green seaweeds (Entomorpha spp. and Cladophora spp.) in shallow upper shore rock pools) EUNIS: A1.421. 

A characteristic species of the lower littoral fringe rock of some shores is channel wrack (Pelvetia canaliculata) and on moderately exposed shores an accompanying spare barnacle community. Habitat classification: LR.MLR.BF.PelB (Pelvetia canaliculata and barnacles on moderately exposed littoral fringe rock) EUNIS: A1.211.

P. canaliculata cover increases on sheltered shores and the there is no associated barnacle community. Habitat classification: LR.LLR.F.Pel (Pelvetia canaliculata on sheltered littoral fringe rock) EUNIS: A1.321.

Rockpooling destination: Hemsby, March 2016

During the months of February and March the eggcases of a variety of rays, skates and catshark are washed up onto the Norfolk shores. Common eggcases that can be found include the Thornback and Spotted ray and the curly ended eggcases of the catshark. Sometimes you can find the larger Blonde ray eggcases.

A walk along the shore turned up some nice mermaid purses and lots of the bryozoan, Flustra foliacea.

Unexpected creatures of the intertidal: Featherstar

A video of a featherstar (Antedon bifida) found on the intertidal of St. Martins, Isles of Scilly.

Characterising species of the supralittoral zone

The supralittoral zone marks the upper extent of the intertidal and in some cases is considered a terrestrial habitat i.e within the EUNIS classification it is placed with the coastal habitats.

The supralittoral or 'splash zone' is the area at the top of the shore that receives the salt spray from the waves, as such, those shores experiencing greater exposure and salt spray from waves have larger supralittoral zones. Rock angle, shade and local climate also influence the extent of the zone.

The supralittoral zone is characterised by rocks covered in lichens, salt tolerant angiosperm and pools with variable salinity and temperatures. The organisms are highly specialized to endure variable salinity, periods of exposure and occasional immersion during storms. 

Lichens are one of the characteristic species of the supralittoral and often come to dominate the available rock. Concordantly the presence of lichens is a key component in the habitat classification of supralittoral rock and is captured by the habitat description: LR.FLR.Lic.YG (Yellow and grey lichens on supralittoral rock) EUNIS: B3.111.

One of the few mobile species to extend up into the supralittoral from the intertidal is the rough periwinkle (Littorina saxatilis).   

A variety of grey and yellow lichens can be found in the supralittoral.

The seaslater (Ligia oceanica) can also be observed.

Salt tolerant plants can also occur.

The distinction between the lichen and plant communities of the supralittoral and the terrestrial vegetation is often unclear. 

Rockpools within the supralittoral experience variable salinity and temperature making them inhospitable for many species. Habitat classification: EUNIS A1.42 (Communities of rockpools in supralittoral zone).

In this example tadpoles are found in the supralittoal rockpools of the shore.

An introduction to zonation on intertidal shores

Where the land meets the sea two worlds join, one or air and the other of sea water.

As the tide rises and falls this stretch of land, refereed to as the intertidal zone, alternates between being exposed to the air and covered by sea.

The relative environmental pressures of submergence and exposure change retrospectively throughout the intertidal zone in relation to altitude from the low water mark. Other factors such as predation and competition also act to influence the communities found. 

The combination of all these factors can often result in repeated and definable communities of species at certain altitudes and/or exposures across the intertidal zone.

Such distributions of communities in relation to altitude or, height on the rocky shore is often referred to as zonation. Zonantion is often discussed in terms of dominant seaweeds present and is best exemplified on sheltered rocky shores. 

Zonation is not always clear cut (see previous blog post: http://thesaltyscavenger.blogspot.co.uk/2014/08/rockpooling-destination-mousehole-may.html) and is affected by factors for which altitude on the shore is often correlated. 

The following posts look at some of the characterising species of the general shore 'zones'; although these can be found else where, they are often characteristic of a particular zone of the shore.

Below are images of some of the different intertidal zones found on UK rocky shores.

The different zones of the intertidal rocky shore in relation to altitude.

The communities on this exposed rocky shore in Shetland exhibit distinct distributions in relation to rock altitude and exposure. Yellow and grey lichens occur at the highest elevation of the rock and mark the supralittoral zone. Below, the rocks of the littoral fringe appear black, from the tar lichen (Verrucaria maura) which is overgrown on the more sheltered vertical rock, by a fringe of the brown channel wrack (Pelvetia canaliculata); the rocks of the upper shore become increasingly grey due to the barnacle communities which are inter-dispersed by patches of the black, Lichina pygmaea.  Habitat classification: LR.FLR.Lic.YG (Yellow and grey lichens on supralittoral rock) EUNIS: B3.111, LR.FLR.Lic.Ver (Verrucaria maura on littoral fringe rock) EUNIS: B3.113 and LR.HLR.MusB.Cht (Chthamalus spp on exposed upper eulittoral rock) EUNIS: A1.112.

The communities on this sheltered rocky shore in Shetland exhibit distinct distributions in relation to rock altitude. Yellow and grey lichens occur at the highest elevation of the rock and mark the supralittoral zone. Below, the rocks appear black, from the tar lichen (Verrucaria maura) and the eulittoral is characterised by fucoids with a green patch of ephemeral greens marking fresh water run off entering the shore. Habitat classification: LR.FLR.Lic.YG (Yellow and grey lichens on supralittoral rock) EUNIS: B3.111, LR.FLR.Lic.Ver (Verrucaria maura on littoral fringe rock) EUNIS: B3.113, LR.LLR.F (Fucoids on sheltered marine shores) EUNIS: A1.31 and  LR.FLR.Eph (Ephemeral green seaweed communities - Fresh water influenced) EUNIS: A1.45.

Regional names of common shore species

The marine animals of the shore often have a common name in addition to their Latin name. These common names can vary around the UK. 

Below are some examples:

Generic common name: Common Whelk – Shetland common name: Buckie – Latin name: Buccinum undatum

Generic common name: Three spot cowrie – Shetland common name: Grotti Buckie – Latin name: Trivia monacha

Generic common name: Edible Periwinkle – Shetland common name: Black Whelk – Latin name: Littorina litorea

Generic common name: Goose barnacles – Shetland common name: Claiks – Latin name: Lepatidae

Generic common name: Razor Shell – Shetland common name: Spoot – Latin name: Ensis sp

Generic common name: Seaslater – Cornish common name: Grammercel – Latin name: Ligia oceanica

Because of the variance in common names recorders log the organisms of the shore by their Latin names which do not change regionally.

Washed up Silver Birch is referred to as gooniemans candle is Shetland