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Intertidal Ecology. Rocky Shores Sandy Shores: sandy beaches Muddy Shores: mud flat. Divisions of Ocean environment. Where? Who? What are they doing there?. Why did these students have to stand in water to do the work?. Mixed, semidiurnal, and diurnal tide curves. Intertidal Ecology.
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Intertidal Ecology Rocky Shores Sandy Shores: sandy beaches Muddy Shores: mud flat
Why did these students have to stand in water to do the work?
Mixed, semidiurnal, and diurnal tide curves. Intertidal Ecology
The intertidal zone is the zone between the highest and lowest tides Highest tide Lowest tide Intertidal Flat Subtidal zone
Characteristics of the intertidal zones • Flood and ebb tides • Water-air alternative exposure • Rhythmic • Rich diversity and density within a small area
Rocky Shore Ecology Zonation Factors affecting zonation Physical Environmental Conditions Biological Interactions
Typical Rocky intertidal zonation patterns(Pacific)Zonation: Predictable distinctive distribution pattern of marine organisms through intertidal zone
Zonation of major species on rocky shores. The figure is a general scheme of common animals and algae found in eastern North America. Details will differ for specific locations.
Classification of zones in all habitat type (Ricketts et al., 1985) • Zone 1: uppermost horizon: Highest reach of spray and storm waves -- the mean of all high tides: the splash, spray, supralittoral, or Littorina zone • Zone 2:high intertidal: Mean high water -- a bit below mean sea level: the home of barnacles and other animals tolerating more air than water • Zone 3: Middle intertidal: about mean higher low water -- mean low water • Zone 4:Low intertidal: normally uncovered by minus tides only. This zone can be examined during only a few hours in each month
Abiotic Wave action and tidal range Desiccation Heat stress Salinity reduced feeding time DO and gas exchange Biotic Larval settlement Intra- and interspecific competition Predation and grazing Physiological tolerance and adaptation behavioral pattern, mobility Factors modifying zonation of Rocky shore
Exposure-shelter diagram for Hong Kong shores. The range of the six litterine species are superimposed. 1. Nodilittorina pyramidalis; 2. Nodilitorina millegrana; Peasiella sp.; 4. Littorina brevicula; 5. Littorina scabra; 6. Littorina melanostoma.
Physical conditions of rocky intertidal areas Tides-Periodical change the organisms' living environments Temperature-desiccation (could be fatal), particular in tropic region Wave action--exerts the most influence on organisms and communities
Physical conditions of rocky intertidal areas (con’t) • Wave action (con’t) • mechanical effect--smash and tear away objects; • acts to extend the limits of the intertidal zone by throwing water higher on the shore (splashing allows the marine organisms to live higher in exposed wave-swept areas than in sheltered areas within the same tidal range • change the topography of intertidal area by move substratum around • mix atmospheric gases into the water--increasing the oxygen content
Physical Conditions of Rocky intertidal areas (con’t) • Salinity-the intertidal may be exposed at low tide and subsequently flooded by heavy rains or runoff from heavy rains --- either would sense severe problems • Substratum topography - grain size would change • pH and nutrients (not very important)
General distribution patterns • Random distribution: distribution of organisms can be explained by random chance • Even distribution: organisms occur in an even manner • Patchiness: Organisms occur in isolated groups within a larger contiguous suitable habitat
Adaptation • Adaptation to desiccation (water loss) • Move to moist place or under the moist cover (crabs & snails) • Tolerate high % water loss (Fucus, Porphyra, Enteromorpha, up to 60-90%) • Reduce water loss by close shells (snails, barnacles, limpets’ home scar) • Build shield to cover up (sea anemone or sea urchin covered with shell fragments)
Changes in the extent of vertical zonation with change in exposure to wave action.
Diagrammatic representation of the adaptations to water loss in intertidal organisms.
Many snails of the genus Littorina live high in the intertidal zone. When exposed, the snail protects itself from desiccation by pulling back into the shell and covering the opening with the operculum. First it secretes a mucous thread that attaches the shell to the rock.
Adaptation • Adaptation to high temperature (heat) • Temperature shock can • affect, metabolic and biochemical processes, such as enzyme function and oxygen demands. • retard cellular activities, such as ciliary motion. • inhibit behavioural activities, such as feeding & protection against predators. • inhibit reproductive behaviour, such as egg laying and copulation.
Adaptation • Adaptation to high temperature (heat) • Reduce heat gain from the environment. • Have a relatively large body size (less surface area relative to volume and less area for gaining heat, taking longer to heat up). (Littorina spp larger at high tidal zone) • Reduce the area of body tissue in contact with the sbustrate (difficult to achieve – swept off by waves) • Increase heat loss from the body • Elaborated shell ridges & sculptures acting as heat radiators (snails) • Light-colored body (gain and lost heat slowly) • Water evaporation (holding extra water in mantle cavity of barnacles, limpets– exceeds the amount the animal needs to survive desiccation)
Differences in heat absorption between smooth, dark shells and sculptured, light shells.
Adaptation • Adaptation to wave action (smashing and tearing effects) • Limitation of size and shape (relatively small, squat bodies with streamlined shapes to minimize the exposure to the lift and drag of wave forces) • Flexible and bending (seaweed) • Firm attachment by holdfast (algae), cemented shell • Temprary attachments by byssal threads (which can be borken and remade) • Thick shells, no delicate sculpturing • Large foot to clamps to the substrata • Seek shelters (crabs)
The distribution of barnacles from shelter to exposure (from Tain Tam to Cape D’Aguilar). 1. Balanus tintinnabulum volcano; 2. Tetraclita squamosa; 3. Pollicipes mitella; 4. Balanus variegatus variegatus; 5. Balanus amphitrite amphitrite; 6. Balanus albicostatus albicostatus; 7. Euraphia withersi. A detail of the numbers and fusion of the valves of the principal genera are also given.
Adaptation • Respiration (gills highly susceptible to desiccation in air) • Enclose in a protective cavity to prevent them from drying (molluscs) • Reduction of the gill and formation of a vascularized mantle cavity • Mantel tissue act as lung for aerial respiration (barnacles) • Close up (operculum) or clamp down (chitons and Limpets) to reduce gaseous exchange • Remain quiescent druing low tide to conserve oxygen and water
Adaptation • Salinity (flood by fresh water or expose to extremely high salinity) • Osmoconformers: organisms without mechanisms to control the salt content of their body fluids – using same adaptation as to prevent desiccation. • Osmoregulators: organisms with physiological mechanisms to control the salt content of their internal fluids
Causes of patchiness in algae on rocky shores. (A) Sweeping action of algal fronds. (B) Irregular spatial and temporal distribution of grazers. (C) Fluctuations in recruitment. (D) Refuge from grazing provided by pits and cracks in rock. (E) Escape of spoelings from grazers.
Biological factors controlling rocky intertidal zonation • Competition (barnacles as examples) • Predation (starfish, mussels, and barnacles) • Grazing (sea urchin on seaweed) • Larval settlement • Interaction among the controlling factors – community ecology
Biological factors controlling rocky intertidal zonation • Competition (barnacles as examples) • Predation (starfish, mussels, and barnacles) • Grazing (sea urchin on seaweed) • Larval settlement • Interaction among the controlling factors – community ecology
Interspecies competition Intertidal zonation as a result of the interaction of physical and biological factors.The larvae of two barnacles, Chthamalus stellatus and Balanus balanoides, settle out over a broad area. Physical factors, mainly desiccation, then act to limit survival of B. balanoides above mean high water of neap tides. Competition between B. balanoides and C. stellatus in the zone between mean tide and mean high water of neap tides then eliminates C. stellatus.
Effect of desiccation and competition on two species of intertidal barnacles
Controlling factors • High tidal zone • Chthamalus stelatus settled here • Semibalanus balanoides have no sufficient tolerance to drying and high temperatures. • Mid tidal zone • Chthamalus stelatus settled here but was overgrew, uplifted or crushed by Semibalanus balanoides
The main groups of algal grazers at different intertidal zones in temperate and tropical systems. Grazing
Effect of sea urchin removal on kelp growth on the Isle of Man, Great Britain. Grazing
Interaction of predation and physical factors in establishing the zonation of the dominant intertidal organisms on the rocky shores
Interactions among mussels (Mytilus), barnacles, and their predators on the northwester Pacific coast of North America, which allow barnacles to persist in the intertidal zone. Predation/competition
Succession in a northwest Pacific coast intertidal mussel bed in the absence of Pisaster.
Sandy and Muddy Shores Sandy Muddy 1. Shape up of beaches Larger • Sediment size • Wave action • Slope Stronger Slopy Exposed 2. Surroundings • Exposed vs protected • Oceanic vs semi-enclosed waters, estuaries or wetlands • Seasonal vs non-seasonal Oceanic Seasonal 3. Sediment movement • Swash and backwash • Longshore transport Applicable
Sandy Muddy Larger 4. Physical conditions of intertidal flats • Grain size • Interstial space • Pore water • Water retention Larger Greater Fluctuation Weaker ShallowerAnoxic 5. Biogeochemical conditons • Oxygen • Organic matter • RPD Rich Strong, Shallower 6. Organisms High • Diversity • Abundance • Production Large High
Longshore Transport Processes So sand downcast in a zigzag path Path of sand on beach returns straight down the beach Water moves on shore at an angle Net Transport of sand Shoreline Surf zone Longshore current Longshore transport
Some terms • Swash: water running up a beach after a wave breaks; this action carries particles with it, which may cause accretion of the beach if the particles remain there • Backwash: water flowing back down the beach; this action removes particles from the beach, depending on the particle size • Slope: the slope of a beach is the result of the interaction between particle size, wave action, and the relative importance of swash and backwash water. • Dissipative beach: occurs where wave action is strong but the wave energy is dissipated in a broad, flat surf zone located some distance from the beach surface (gentle swash, fine sediments, gentle slope • Reflective beach: occurs where wave action impinges directly on the beach face and the sediment is coarse (no offshore surf zone, wave produce large swashes up the beach face, steep slop). Backwash and swash collide to deposit sediment and wave energy is directed against the face of the shore and reflected off the surface.
