Coastal Ecology

1. Varieties and Conditions of the Seashore

Hurker’s Haven, Berwickshire

Lamberton Beach, Berwickshire (Rock Platform)

Burnmouth, Berwickshire

Lawrencetown Beach, Nova Scotia (Cobbles)

Aldburgh, Suffolk (Shingle)

Druridge Bay, Northumberland (Sand)

Sand Dunes at Bamburgh, Northumberland

Saltmarsh at Alnmouth, Northumberland

Saltmarsh at Alnmouth, Northumberland

Sea Braes at Berwickshire

Seaweeds 1: Red

Seaweeds 2: Brown

Seaweeds 3: Green

Marine Animals 1: Sea Anemones

Marine Animals 2: Annelids

How we normally see Arenicola

Marine Animals 3:Molluscs

Marine Animals 4: Echinoderms

Marine Animals 5: Echinoderms

Sea Urchins in a less-usual setting

Marine Animals 6: Crustaceans

Factors influencing organisms

• Substratum

• Light

• Desiccation

• Pollution

• Exposure

• Salinity

• Temperature

• Grazers and Predators

Substratum

• Rocky shores and sandy shores have different fauna.• Seaweeds need a firm substratum on which to become

attached (which, in the case of wracks for example, they do within an hour of fertilisation).

• Seaweeds are adapted to their environment – they are not just tolerating it.

• Individual species of seaweed have specific environmental requirements.

• Detached plants and algae in the drift on the strandline are dying or dead.

• Plants don’t ‘make a choice’: their spores settle and, if conditions are satisfactory, the plant will develop – if they are not it will die.

Nature of substratum

• All solid substrata are colonisable by algae.• Chemical nature is irrelevant.• Texture i.e. roughness/smoothness may affect

attachment of species.• Unstable substrata, such as shingle and sand

are generally of no use to seaweeds (exceptions are that there is a filamentous red seaweed which binds sand and the brown seaweed Desmarestia viridis will grow subtidally on shingle).

Sand bound by Audouinella floridula

Desmarestia viridis

Light

Action spectrum for Chlorophyll a

This shows that most photosynthesis takes place in red light and some in blue light. Chlorophyll reflects (and therefore cannot utilise) green light – which is why it appears green.

Desiccation and Zonation

Adaptations to desiccation

• Thick cell walls in species found higher on the shore.

• Mucilage to prevent drying out in cell walls (Brown algal cell walls are composed of a fibrillar polysaccharide called alginic acid together with cellulose and an amorphous polysaccharide called fucoidan).

• Early stages in development of Pelvetia are retained in mesochiton (vestige of structure in which eggs are produced).

• Plants may dry out but may rejuvenate when wetted.

Photosynthesis and desiccation

• There is some evidence in some species, for example of Fucus, that photosynthesis ceases when the plant is uncovered at low tide and only resumes when the plant is recovered. This means, of course, that the plant can only produce sugars when high tides occur during daylight, and the higher a plant is on the shore the shorter its photosynthetic activity.

Problems with silt

• Produces an unstable substratum.

• Reduces light for photosynthesis.

• Causal factor in absence of Himanthalia from Durham coast (work by Moss et al 1973) and affecting distribution of Fucus in the Baltic (2003).

Pollution

• Pollution can be visible (such as silt, oil spills, non-biodegradable plastic) or invisible (such as chemicals from agricultural run-off, bacteria from sewage).

Surf Scoter in San Francisco Bay, 2007

Rubbish on beach at Curacao

Exposure

• By and large, most seaweeds do not like extremes.

• Very exposed shores tend to be clear of macroalgae, which are replaced by mussels and barnacles. One exception is the filamentous red seaweed Ceramium shuttleworthianum which grows in mussel beds.

• Some species characteristic of fast flowing currents e.g. Alaria esculenta.

Ceramium shuttleworthianum

• Very delicate, striped, spiny species of Ceramium.

Alaria esculenta

Fucus vesiculosus and exposure

• Direct link between number of number of air bladders and degree of exposure – in sheltered habitats get colossal number of air bladders.

Brown algae and exposure

• In fast moving currents bladders are absent from bladder wrack (if that is not a contradiction in terms) – form evesiculosus.

• Work in Norway in the late 1960s/early 1970s demonstrated that the degree of digitation in the kelp Laminaria digitata is directly related to exposure.

Ascophyllum nodosum

• Characteristic of sheltered shores – particularly abundant on the west coast of Scotland where it is harvested.

Effects of salinity

• Seawater is made up of roughly 35 parts per thousand salt.

• Freshwater – rivers/streams or rain – reduces salinity.

• Evaporation – for example in rock pools – increases salinity.

• Seaweeds are either adapted to these variations or don’t survive.

Estuaries

• Green seaweeds are more tolerant of reductions in salinity than other groups (red seaweeds are least tolerant).

• Working up an estuary from the coast, you will find that red seaweeds die out first (very close to the estuary mouth), brown seaweeds will persist somewhat further, green ‘seaweeds’ extend into freshwater.

Fucus vesiculosus/ceranoides

• Fucus vesiculosus (bladder wrack) is a coastal seaweed.

• In estuaries this is replaced by Fucus ceranoides.

• A transect up the estuary would show Fucus vesiculosus on the coast, then a mixture of both species, then Fucus ceranoides alone (and then, ultimately, no Fucus species at all).

Fucus vesiculosus/ceranoides

• Recent experimental work has demonstrated that Fucus ceranoides grows as well in seawater as it does in reduced salinities; its absence from the shore generally is due to it being a poor competitor with Fucus vesiculosus.

• Fucus ceranoides predominates in estuaries because Fucus vesiculosus doesn’t tolerate reductions in salinity so well. (Confusingly, in local estuaries, Fucus ceranoides is absent from the River Tyne and Fucus vesiculosus penetrates up the estuary to Gateshead).

Fucus ceranoides

• More delicate and ‘filmy’ than Fucus vesiculosus with pointed apices.

Temperature

• Being fixed to one spot, seaweeds have to tolerate the ambient temperature.

• Species distributions are strongly influenced by temperature: for example, Bifurcaria bifurcata will grow in Devon but not in Northumberland; Lithothamnion glaciale will grow in Northumberland but not in Devon. Tropical species distinct from temperate ones

• ‘Enteromorpha’ seems to tolerate just about anything – hence its success as a ship-fouling organism.

Bifurcaria bifurcata

Lithothamnion glaciale

Being eaten alive: the world of grazers

• Variety of animal grazers from sea slugs, limpets and sea urchins to fishes.

• This causes tissue damage and can be sufficiently common to affect species’ growth on the shore.

• Filter feeding animals such as mussels ingest algal spores as part of their diet.

• This can, of course, influence settlement and growth of algal populations.

Blue-rayed limpet

Diadema (Tropical sea urchin)