Red Seaweed Identification

A diverse array of red seaweeds occur within the intertidal many of which require specialist terminology and equipment to identify them. 

The following posts include images of common red seaweed groups and seaweeds that can be identified in the field.

The first step in identifying red seaweeds is to be able to recognize the major groups, then try to recognize the family and note the habitat in which the seaweed is found. 

The most commonly recorded red seaweeds belong to the following orders:

Ahnfeltiales, Bangiales, Bonnemaisoniales, Ceramiales, Corallinales, Gigartinales, 

Gelidiales, Palmariales, Plocamiales,  Nemaliales and Rhodymeniales.

The orders Ceramiales, Corallinales, Gigartinales and Rhodymeniales contain the highest 
 number of common intertidal red seaweeds.

A tree weed - Washed up onto the shore at Great Yarmouth, Norfolk December 2014

Rockpooling destination: Revisit Hemsby, Norfolk, July 2015

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



Strong winds and waves resulted in the erosion of the finer sediments to reveal a pebble bed below, but what was astonishing was that barnacles and polychaete worm tubes were among the cobbles, even though the substrate had not long been exposed.....

Erosion of the finer sediments, have left coarser sediments exposed. Habitat classification: LS.Sa (Littoral sand) EUNIS A2.2 and LS.LCS (Littoral coarse sediments) A2.1 

Polychaete worm tubes occur amongst the coarser sediments of the lower shore.

Polychaete worm tubes occur amongst the coarser sediments of the lower shore.

The occurrence of the polychaete worm tubes is quite extensive.

There are even barnacles on the cobbles!

This is quite intriguing as the shore is so variable and the coarser sediments are often covered as shown below.

The shore in December, 2014.

The shore in Summer, 2014

The shore in September, 2012



Rock Pooling Destination: Porth Seal, Isles of Scilly, UK. April 2013

The rock pools at Porth Seal vary with those in the upper shore characterized by the green seaweeds Cladophora and Ulva spp; whilst mid shore pools are dominated by encrusting coralline algae and a variety of red and brown seaweeds; further down the shore brown seaweeds, such as Bifurcaria bifurcata and Himanthalia elongata, become more prolific within the coralline pools with red seaweeds occupying the understory. Above the pools is a mosaic of fucoids, osmundea, grazing molluscs and barnacles.


Spring storms had washed large quantities of seaweed up onto the shore where it formed mounds marking the successive strand lines and filled many of the higher to mid shore pools. The presence of the decomposing seaweed in the pools caused the water to become de-oxygenation and stagnant. The spring storms also deposited sand into many of the higher and mid shore pools that formed a thick layer over the pre-existing coralline algae and facilitated the growth of ephemeral green seaweeds such as Cladophora spp. In comparison to April 2012 these pools appeared to contain less mobile fauna (fewer gastropods and no sea hares were observed).

Below are photographs of some of the organisms in these pools:


                                        

Spring storms had washed large quantities of seaweed on the shore.

The washed up seaweed filled many of the higher to mid shore pools.

 The presence of the decomposing seaweed in the pools caused the water to become de-oxygenation and stagnant.

The rocky shore is comprised of bed rock and boulders interspersed with rockpools and gullies. Biotope classification:  LR.MLR (Moderate energy littoral rock).

 The mid and upper shore is charecterised by mosaics of barnacles and fucoids.

Barnacles

The shallow rock pools of the upper and mid shore that have not been smothered by sand or seaweed are charecterised by corallinacea crusts. Biotope classification:   

LR.FLR.Rkp.Cor (Coralline crust-dominated shallow eulittoral rockpools).

A corallinacea crust dominated rock pool with Coral weed (Corallina officinalis), Beadlet anemone (Actinia equina), Topshell (Gibbula umbilicus) and a blenny. 

A beadlet anemone (Actinia equina)

A mussel (Mytilus edulis)

A coralline pool dominated by ephemeral green seaweeds; coralline crusts can still be seen beneath the sand.

Sand covers the Corallinacea crust and the pool is dominated by ephemeral green seaweeds.

Mid shore pools are less effected by the deposition of seaweed and contain more seaweed species.

Coral weed (Corallina officinalis) 

Ceramium Spp 

Codium fragile 

Codium fragile on the mid shore.

 Bushy rainbow wrack (Cystoseira tamariscifolia).

Cladophora rupestris

Calliblepharis jubata

Polychaetes

Daisy anemone (Cereus pedunculatus)



Gem anemone (Aulactinia verrucosa)

  Bifurcaria bifurcate dominates certain pools of the lower shore. Biotope classification: LR.FLR.Rkp.Cor.Bif Bifurcaria bifurcata in shallow eulittoral rockpools.

Serrated wrack (Fucus serratus) dominates the lower shore with red seaweeds beneath its understory. Biotope claasification: LR.MLR.BF.Fser.R (Fucus serratus and red seaweeds on moderately exposed lower eulittoral rock).

Red seaweeds form mosaics amongst the serrated wrack (Fucus serratus). Sand binder (Rhodothamniella floridula) forms a truf whilst Osmundea spp occurs within crevices and cracks of the boulders.

Osmundea spp

A limpet (Patella vulgata) and barnacles

Grape pip weed (Mastocarpus stellatus)

Corallinacea crust, Corallina officinalis , Bifurcaria bifurcata, The limpet Patella vulgata and snakelocks anemone (Anemonia viridis) occur on a boulder amongst Serrated wrack (Fucus serratus).

Corallinacea crust occurring on the lower shore.

Coral weeds (Corallina spp ) form dense turfs on the lower shore.

Dahlia anemone (Urticina felina)

Purse sponge (Grantia compressa)

Further down the shore Thong weed (Himanthalia elongata) occurs amongst red seaweeds.

Hemsby, Norfolk September 2012

Rock pooling destination: Hemsby, Norfolk, September  2012

The stretch of beach at Hemsby alternates between swathes of sand and shingle.  It has a gently sloping profile. When the tide is in, currents run across the beach, forming shingle berms.

The shore is barren of life due to the mobile nature of the sediments and its inability to hold water within the interstitial spaces of the pebbles whilst the tide is out.

Insects such as flies and beetles occur amongst the upper shore and organisms are found washed up amongst the strandline.

On this occasion strong weather had washed up many empty razor shells, shore crabs and rhodophyta marine algae, amongst which could be found small gastropods.

The habitats present come under two classifications: LS.LSa (Littoral Sand) and LS.LCS.sh.BarSh (Barren littoral shingle).  

Below are photographs of some of the organisms encountered whilst rock pooling in this habitat.

Habitat Classification: LS.LSa (Littoral Sand).

When the tide is in, currents run across the beach, forming shingle berms. Habitat Classification: LS.LCS.sh.BarSh (Barren littoral shingle). 

Razor shells washed up on the strand-line.



Shore crab (Carcinus maenas) washed up on the shore.

Razor shells washed up on the strand-line.

Red seaweeds (Rhodophyta) washed up from cobbles off shore.