Rocky Shore Ecology
Upper Shore
Middle Shore
Low Shore
Ecosystems on rocky shores have bands of different species across the intertidal zone. The distribution of different species across the rocky shore is influenced by biotic and abiotic factors from above high tide to the sub-tidal zone.
Problems of living on a rocky shore
Abiotic Factors
• Wave action• Water loss and desiccation• Temperature fluctuations• Salinity fluctuations• O2, CO2, pH fluctuations• Range of illumination• Immersion / emersion cycle• Pollution
Biotic Factors
• Predation and competition
• Reproduction
Wave Action Tidal Cycles
Entrance to Baltimore Harbour
January 2014
Near Oregon Institute of Marine Biology,
USA
Lewis’ Classic Zonation Description
Highly exposed Semi-exposed
Highly sheltered 1) Seaweed Cover
2) Shore aspect
Ballantine Scale
• Retreat to sheltered areas• Protective cover• Internal gill• Strong adhesive power (byssus threads,
muscular foot)• Flattened body• Red pigment in algae for deep water
illumination
Against desiccation, wave and salinity
Some common seaweeds on rocky
shores
Primary Producers/Autrophs - algae, phytoplankton and seaweeds
Primary Consumers - grazers and filter-feeders
Secondary Consumers-carnivores e.g. dogwhelks
Tertiary Consumers e.g. birds
Predation
Food Web
Low shore
Kelp - Laminaria
Fucus serratus
Mid-shore
Bladder wrack (Fucus vesiculosus)
(Sheltered shores only)
Cladophora(Tufted) (usually near /in rockpools)
High Shore
Channel wrack -
(Pelvetia canaliculata)
Gut weed -Enteromorpha intestinalis
Opportunistic – grows near FW runoff
Pink Encrusting Seaweeds Lithophyllum spp. &Lithothamnion spp.
Found across the zones
Phytoplankton
Common animals on rocky shores
•Periwinkles or sea snails – Littorina spp. mainly
•Graze on algal biofilms
•Different spp. at different shore heights – look at operculum (opening) shape – not colour!!
•Can be very small at high shore
Periwinkles Littorina spp
Common periwinkle Littorina littorina
• Pronounced tooth or notch on aperture.
• Shell has up to 6 whorls.
• Shell dark green, grey or black with brown or red zigzag markings
• Underside pearly-white
Purple/flat Topshell Gibbula umbilicalis
• Small topshell 1.6 cm high, 2.2 cm across.
• Large round umbilicus.
• Dull greenish grey in colour with reddish-purple broad diagonal stripes.
Thick/toothed Topshell Osilinus lineatus
•Filter feed using cirri so need water movement
•Only sedentary crustacean – not a mollusc!!
•Close up operculum when tide is out
•Lifespan of 5 to 10 years
•Penis size relative to body
Barnacles
https://www.youtube.com/watch?v=DTfkSr4GAXo
Barnacles exhibit phenotypic plasticity, meaning that they can change their penis size depending on competition and environment.
Barnacles living in gentle waters have long, thin penises best equipped for maximum reach. But those animals living in rough waters have shorter, stouter penises that are better able to withstand strong waves.
Montagu's stellate barnacle (Chthamalus montagui)
Acorn Barnacle (Semibalanus balanoides)
Austrominius modestus
Invasive species
• Limpets (2 species) – Patella species• Graze on biofilms• Look at foot colour (green or orange)• Shell shape and height – look at apex of shell• Make a home scar to maintain position
Limpets
Some species of limpets return to the same spot on the rock known as a "home scar" just before the tide ebbs.
All shore heights Low shore & rock pools only
Patella vulgata Patella ulyssiponensis
A keystone species is a plant or animal that plays a unique and crucial role in the way an ecosystem functions.
A keystone species is a species that has a disproportionately large effect on its environment relative to its abundance.
Without keystone species, the ecosystem would be dramatically different or cease to exist altogether.
Keystone species
•commensalism: occurs when an individual obtains a benefit from a different species without damaging it.
•mutualism: occurs when an individual obtains a benefit from another species and, at the same time, the second species obtains a benefit from the first one. Mutualism is not obligated, which makes it different from symbiosis.
•symbiosis: species benefiting one another but also depending on one another. If one of the symbiotic individuals dies, the other also dies by losing the source from which it was obtaining a benefit.
•Bivalves
•Filter feeders – use siphons to suck in water
•Close up when tide is out
•Form dense beds attached by byssus threads
Mussels Mytilus edulis
•Predator on barnacles and mussels
•Different shell shapes depending on factors
Dog Whelks Nucella lapillus
In evolutionary biology, an evolutionary arms race is a struggle between competing sets of co-evolving genes, traits, or species, that develop adaptations and counter-adaptations against each other, resembling an arms race. These are often described as examples of positive feedback.
Guild, in ecology, a group of species that exploits the same kinds of resources in comparable ways.
Beadlet Anenome Actinia equina
• They are able to move
• 92 tentacles are arranged in six
circles
• Brood their young (viviparous
reproduction)
• Very aggressive
Bits and Bobs
Empty egg cases of the Dog Whelk
Mermaid purse
Skate Rabbitfish Sharks
Gooseneck Barnacles
By the wind sailor - Velella velella
Sea Potato Echinocardium cordatum
Portuguese man of war
Is a siphonophore, an animal made up of a colony of organisms working together.
Whale vomit - Floating Gold
Used in the manufacture of perfume
Ambergris