Wednesday, 20 July 2016

Rockpooling Destination: Revisit Lands End Peninsula, June 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:

For the past 21 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 and the infill of many of the sediment filled rockpools.

Below are images showing the change in sediments and habitats observed since April 2015/ March 2016.

 The shore in June 2016, shows an increased fucoid and ephemeral seaweed cover since March, 2015.

The rocky shore in March 2016 exhibits increased sand deposition, reduced seaweed cover and rockpool occurrence since June 2015.

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

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  been mostly covered by sand.
Rather than fucoid seaweeds ephemeral seaweeds are now the dominant seaweed on this section of the shore.

This photograph taken in June, 2015 shows an area of the shore before the sand was deposited. 
Now sand has covered much of this habitat.

Sand continues to be deposited on the shore, covering the fucoid habitat.

Ephemeral seaweeds such as Porphyra sp cover rocks of the lower shore.