Rockpooling Destination: Revisit to Lands End Peninsula Sept 2015

Below are images of some of the organisms seen whilst rockpooling around the Land's End peninsula in September 2015:

Small and rough periwinkles together with sparse barnacles on the larger boulders of the upper shore.

Springtails investigate a crack in the shell of a rough periwinkle. 

Thick topshells (Osilinus lineatus) among the boulders  and cobbles.

Osilinus lineatus

Osilinus lineatus

The habitats of the shore are influenced by wave exposure, sand scour, fresh water run off and desiccation. The result is a patchwork of biotopes that are not distributed evenly down the shore. In general boulder tops are covered  by fucoids and/or barnacles, whilst ephemeral green seaweed lace the diluted sandy rockpools and lastly sand scour tolerant seaweeds occur in scoured rockpools and boulders of the lower shore. Habitat classification: LR.MLR.BF (Barnacles and fucoids on moderately exposed shores) EUNIS: A1.21, LR.FLR.Eph (Ephemeral green or, red seaweeds (Fresh water or sand influenced) EUNIS: A1.45 and LR.FLR.Rkp (Rockpools) EUNIS: A1.41.

Porphyra spp

Ulva spp

 LR.MLR.BF (Barnacles and fucoids on moderately exposed shores) EUNIS: A1.21.

Some areas of the shore are showing seasonal die back of fucoids.

Fucus spp (Fucus vesiculosus var. nana?)

Fucus spp (Fucus vesiculosus var. nana?)

Understory reds.

A dog whelk (Nucella lapillus) 

Verrucaria mucosa

Limpets (Patella sp) and beadlet anemones (Actinia equina)

The seaweed communities on the lower shore  are comprised of fucoids, robust reds and sand tolerant seaweeds. Habitat classification: LR.MLR.BF.Fser.R (Fucus serratus and red seaweeds on moderately exposed lower eulittoral rock) EUNIS: A1.2141.

Fucus serratus, Mastrocarpus stellatus and ephemeral greens.

Fucus serratus, Mastrocarpus stellatus, Rhodothaminiella floridula and ephemeral greens.

Mastrocarpus stellatus

Gigartinales

Cladophora rupestris

Ulva spp in a sediment filled rockpool. Habitat classification: LR.FLR.RKP.SwSed (Seaweeds in sediment floored eullitoral rockpools) EUNIS: A1.413.

Sand tolerant seaweeds in a sediment filled rockpool.

Phyllophoracea

Hypoglossum hypoglossoides

Rhodothaminiella floridula

Porphyra spp

Black scour weed (Ahnfeltia plicata)

Gigartinales

Gigartinales

Gigartinales

Gigartinales

Gigartinales

Cystoclonium purpureum

Ceramium spp

Asparagopsis armata

Corallina sp form turf in the lower shore rockpools.

Corallina officinalis

Corallina spp

There were no signs of the tube dwelling amphipods among the seaweeds of the sediment filled pools, only the cases of thier tubes remained.

In June, 2015 there were a number of amphipods encased within tubes that were in turn enveloped among the green seaweed.

Asteria rubens

'

Barnacle communities cover more exposed rocks of the lower shore. Habitat classification: LR.HLR.MusB (Mussel and/or barnacle communities).

Barnacles

Rockpooling Destination: Revisit to Lands End Peninsula Sept 2015

As seen in the previous post the bay has experienced some recent changes in deposition and erosion, resulting in the formation of a strandline and winnowing of finer material from the uppershore cobble beach. However, these are not the only changes to have occurred as this post will reveal...

As seen in the previous post a strandline has formed on the upper extent of the cobble beach. The newly formed strandline is important as it provide a resource for food and shelter, on an otherwise barren upper cobble and boulder beach.

This photograph taken in June, 2015 shows the absence of a strandline on this section of the shore. See post http://thesaltyscavenger.blogspot.co.uk/2015/08/rockpooling-destination-revisit.html 

This photograph taken in June, 2015 shows much of the upper shore bedrock and boulders covered by seaweed. See post http://thesaltyscavenger.blogspot.co.uk/2015/08/rockpooling-destination-revisit.html

However, by September, 2015 the percentage cover of seaweed on upper shore boulders and bedrock has reduced. 

Bedrock that was covered in ephemeral green seaweeds are now bare, whilst the Fucus sp is reduced to stumps.

There is a distinct lack of 'green' in this photograph compared to the photograph below that was taken in June, 2015.

Fucus sp cover the boulders, whist ephemeral green seaweed lace the diluted and sand scoured rockpools. June, 2015. See post http://thesaltyscavenger.blogspot.co.uk/2015/08/rockpooling-destination-revisit.html

What could have caused this change? Abrasion from the winnowed sediment? Seasonal die back or grazing? Since June there has been an increase in limpet abundance, c. Could their grazing be accountable?

Limpet density is higher than in June, could it be that individuals moved with the changing season. Seasonal migrations are noted in limpet species of British species (http://www.marlin.ac.uk/biotic/browse.php?sp=4220) or, were  the limpets swept in with  the fronds of the strandline , as noted for limpets in Advances in Marine Biology vol 16 or, maybe population abundance has peaked as a feature of the limpet life histories?

Topshell density had also increased behind the stack.

There were no signs of the tube dwelling amphipods among the seaweeds of the sediment filled pools, only the cases of thier tubes remained.

In June many amphipods were observed occupying tubes which were in  turn enveloped among the green seaweed. See post http://thesaltyscavenger.blogspot.co.uk/2015/08/rockpooling-destination-revisit.html

All other seaweeds except the fucoids exhibited no or little seasonal die back at this time and the remaining habitats remained largely unchanged since June, 2015.