Rockpooling Destination: Land's End Penisula March 2016 (Part 2)

Continued from the previous blog:

The rocky shore in March, 2016 has changed from that observed in June, 2015 with increased sand deposition and reduced seaweed cover and rockpool abundance.

The habitats encountered are consistent with those previously recorded in September 2015 but the distribution and extent of each habitat has changed.

Habitat classification:

Substrate	LR (Littoral rock)						LS (Littoral Sediments)
Habitat	LR.HLR (High energy littoral rock)	LR.MLR (Moderate energy littoral rock)	LR.FLR (Features of littoral rock)				LS.Lsa (Littoral Sand)
Biotope complex	LR.HLR.MusB (Mussel and/or barnacle communities)	LR.MLR.BF (Barnacles and fucoids on moderately exposed shores)	LR.FLR.Rkp (Rockpools)		LR.FLR.Eph (Ephemeral green or red seaweed communities)	LR.FLR.Lic (Lichens and small green algae on suprallitoral and littoral fringe rock)
Biotope		LR.MLR.BF.Fser.R (Fucus serratus and red seaweeds on moderately exposed lower eulittoral rock)	LR.FLR.Rkp.Cor (Coralline crust dominated shallow eulittoral rockpools)	LR.FLR.Rkp.SwSed (Seaweeds in sediment-floored eulittoral rockpools)

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

Lichens on supralittoral and littoral fringe rock. Habitat classification LR.FLR.Lic (Lichens on supralittoral and littoral fringe rock) EUNIS: B3.11

Green algae surrounds the fresh water falls.

Ephemeral green algae cover upper shore rocks around the stack.

Small and rough periwinkles occur among these boulders.


Rough periwinkle (Littorina sp)

Increased sand deposits have formed a sandy area in the left hand side of the bay's upper shore. Habitat classification: LS.Lsa (Littoral Sand).

The distribution of organisms has changed in response to the sand deposition, with many gastropods taking to the cliff walls and extending further up the cliff than would usually be encountered.

The  rocks to the right of the bay have not experienced the same amount of sand deposition and hence support habitats similar to that observed during previous rockpooling visits. Ephemeral green and red seaweeds cover boulders of the upper to mid shore, with  barnacles throughout. The bedrock also supports ephemeral greens such as Ulva sp and Cladophora sp, especially where influenced by the fresh water runoff from the river. Lastly the patches of the lower shore support a canopy of Fucus serratus under which reds can be found. Habitat classification: LR.FLR.Eph (Ephemeral green or, red seaweeds (Fresh water or sand influenced) EUNIS: A1.45 and LR.FLR.Rkp (Rockpools) EUNIS: A1.41,LR.MLR.BF (Barnacles and fucoids on moderately exposed shores) EUNIS: A1.21 and LR.FLR.Rkp (Rockpools) EUNIS: A1.4.

Coralline rockpools on the stack appear to have been unaffected by the sand deposition on the shore and are continuing their establishment. Habitat classification: LR.FLR.Rkp.Cor (Coralline crust dominated shallow eulittoral rockpools) EUNIS: A1.41.

Bifucaria bifactata is becoming established within the deeper coralline rockpools.

 Scytosiphon lomentaria grows on a china limpet

Barnacles and limpets occur at variable densities across the shore where there are boulders and bedrock. Among the boulders of the lower shore are patches of green algae, Verrucaria mucosa and the occasional dog whelk (Nucella lapillus).

Fucus serratus forms a patchy canopy on the lower shore.

The abundance of F. serratus has reduced with the increased sand deposition which has scoured and buried the seaweeds.

The sand has infilled in the rockpools and covered the bedrock.

 This photograph shows the Cladophora sp that once covered the bedrock together with sandbinder (Rhodothaminiella floridula). Now these seaweeds occur in patches.

Rockpooling destination: Revisit Land's End peninsula, March 2016

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 on the shore host a similar barnacle community plus a variety of seaweeds, including where sand scour is event, ephemeral seaweeds. Rockpools occur sporadically throughout the shore, and a river flows downs from the cliffs.

The bay experiences a dynamic regime, alternating between periods of erosion (stony) and deposition (sandy).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.

Please see previous blog posts:

http://thesaltyscavenger.blogspot.co.uk/2015/10/rockpooling-destination-revisit-to.html

http://thesaltyscavenger.blogspot.nl/2015/07/rockpooling-destination-revisit-lands.html

http://thesaltyscavenger.blogspot.nl/2014/05/revisit-lands-end-peninsular-april-2014.html

http://thesaltyscavenger.blogspot.nl/2014/02/rockpooling-destination-lands-end.html

For the past 18 months the shore has been stony and a series of rockpooling visits has documented the slow colonisation and succession of the sea shore communities of the newly available substrate. Now the shore is experiencing increased sand deposition which is influencing the communities previously documented. Notably, increased sand deposition and reduced seaweed cover, particularly of ephemeral green seaweeds, and the infill of many of the sediment filled rockpools.

Below are images showing the change in sediments and habitats observed since April 2015.

The rocky shore in March 2016 exhibits increased sand deposition, reduced seaweed cover and rockpool occurrence.

The shore in June 2015 is predominantly comprised of bedrock and boulders and has an increased seaweed cover and rockpool occurrence. 

Since April, 2015  the amount of sand deposited on the shore has increased covering the underlying boulders that previously supported a 'newly' colonising fauna of ephemeral green and red seaweeds, limpets, periwinkles and sparse barnacles. Now this area of the shore represent a barren mobile sand habitat.

This photograph taken in April 2015, shows the previous distribution of sediments in this area of the upper shore. 

This photograph taken in September 2015, shows the previous distribution of sediments in this area of the upper shore. 

 

Sand now covers much of the 'central' bay area which was previously boulders and bedrock.

This photograph taken in September 2015 shows the typical Fucoid and ephemeral seaweed communities that covered the bedrock and boulders of the shore which has now mostly covered by sand.

 Increased sand deposition is also evident on the lower shore where it has filled in rockpools and covered bedrock.

The lower shore in 2015

Sand has covered the lower shore bedrock and infilled most of the sediment filled rockpools.

This photograph taken in June, 2015 shows the same area of the shore before the sand was deposited. There distribution of the red seaweed and fucoid and rockpools habitats is now far more limited than at the time of this photograph as such rockpooling at either of this times would provide different data sets for the shore and demonstrates the necessity for long term monitoring to ensure accurate characterisation of rocky shores.

How will the shore look next time? Well I have been down and I will post what I saw soon!

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.