Tuesday 21 October 2014

Rockpooling destination: Seapalling July 2014


The shore at Seapalling is influenced by a series of artificial sea defences that have changed the dynamics of the shore to produce multiple bays comprised of mobile sands with shingle berms in between.

The hard substrate is characterised by a barnacle community with periwinkles, limpets, dog whelks and beadlet anemones. The lower edges of the breakwater harbour occasional seaweeds, whilst beneath the sea defences are a network of tidal pools.

Since April certain features of the shore have changed, namely increased ephemeral algae growth.

Habitat classifications:


Substrate
LR (Littoral rock)
LS (Littoral substrate)
Habitat
HLR (High energy littoral rock)
FLR (Features of littoral rock)
LS.LSa (Littoral sand)
Biotope complex
LR.HLR. MusB (Mussel and/or barnacle communities)
Rkp (Rockpools)
Eph.FLR.Eph (Ephemeral green or red seaweed communities
LS.LSa.sh (Shingle and gravel shores)
LS.LSa.MoSa.BarSa (Barren littoral coarse sand)
Biotope


LR.FLR.Eph.EntPor (Porphyra purpurea and Entomorpha spp. on sand scoured lower eulittoral rock)



Below are images of organisms you may see whilst rock pooling in this location:

The sea defences provide an artificial hard substrate amongst the littoral sediments of the shore. Habitat classification: LR.HLR (High energy littoral rock) and LS.LSa.MoSa (Barren littoral coarse sand). 

The littoral sediments surrounding the sea defences continually experience the dynamic forces of erosion and deposition.  At this time sand has been eroded from the base of the defences leaving coarser sediment comprised of sand, shingle and razor shells.

The same location as above but in April  2014,shows how sediment levels have decreased in height and have changed from sand to shingle, sand and razor shells.

The same location as above but in October 2013,shows a sediment type of sand and shingle which is more similar to that observed in July 2014. 
Rocky shore communities have formed on the artificial sea defences; barnacles, limpets and periwinkles occur throughout the shore and characterise the biotope complex LR.HLR.MusB (Mussels and/or barnacles in high energy littoral rock).

Barnacles and periwinkles (Littorina sp)

Barnacles and periwinkles (Littorina sp)

During the summer months ephemeral green algae grows over the barnacles of the lower shore 

Barnacles, ephemeral green algae and periwinkles (Littorina sp)


A limpet

Common limpets (Patella vulgata), barnacles and  periwinkle (Littorina sp)

Ephemeral algae, including Porphyra sp fringe the sand scoured rock of the lower shore LR.FLR.Eph.EntPor (Porphyra purpurea and Entomorpha spp. on sand scoured lower eulittoral rock)



It appears that the erosion of sediments and subsequent increase in available rock substrate that was observed in April 2014, has facilitated the growth of ephemeral seaweeds.

These rocks photographed in  April 2014, have bare bases, caused by recent erosion and it was this event that provided additional surface areas for fast growing ephemeral seaweeds to exploit, as seen in the photograph above from July 2014.

A small rockpool beneath a boulder overhang supports a variety of seaweed species, including Coralline crusts, Ulva sp and reds. Since April there has been an increase in the growth of all species, especially the Ulva sp.

The same rock pool but in April, demonstrates the prolific growth of the green seaweeds in summer.






No comments:

Post a Comment