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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Sandy Shores: sandy beaches
Muddy Shores: mud flat
The intertidal zone is the zone between the highest and lowest tides
Length of maximum submergence (hours)
Rocky Shore Ecology
Factors affecting zonation
Physical Environmental Conditions
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.
Wave action and tidal range
reduced feeding time
DO and gas exchange
Intra- and interspecific competition
Predation and grazing
Physiological tolerance and adaptation
behavioral pattern, mobility
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
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.
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.
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.
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.
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.
Sandy and Muddy Shores
1. Shape up of beaches
3. Sediment movement
4. Physical conditions of intertidal flats
5. Biogeochemical conditons
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
Water drains out at low tide
Water retained at low tide
Surface stability of particulate shores. Surf causes a suspension of the particles. Waves 1m in height disturb the sediments to a depth of 8 cm. Burrowing in this shifting substrate is difficult.
A common sense, all public recreational beaches are usually sandy shores.
Sandy shores are usually exposed, poor in nutrients and therefore organisms.
Muddy shores usually associated with estuaries and salt marshes, enclosed bays, lagoons, harbours,
Protected from open ocean wave action
Near sources of fine sediments
Subsequent morphology changes- To burrow deeper, the clam Tivela stultorum developed heavy shell and long siphons; - To burrow fast, raxor clams of the genus Siliqua have very smooth shells, special ridges on the shell to grip the sediment to aid in penetrating into the substrata, sand dollars have much reduced spines to allow them to burrow them into the sand; sand crabs have a short body with limbs highly modified to dig quickly into wet sand;sand dollars Dendraster excentricus accumulate iron compounds in a special area of their digestive tracts, which serve as a weight belt to keep them down in the presence of wave action.
Adaptation of organisms of sandy beach
Developed special structures to prevent clogging of respiratory surface--intake siphons of sandy beach clams are often fitted with various screens; the antennae of sand crabs held together form a tube to surface through which water enters the branching chamber--densely clothed with closely spaced hairs designed to prevent entrance of sand.
Upper limit of wave spray and splash
Types of organisms
Flora: plant community
Fauna: animal community
Epifauna: animals dwelling on the surface of sediment
Infauna: animals dwelling below the surface of sediment
Microfauna: organisms < 0.1 mm
Meiofauna: 0.062 mm - 0.5 mm
Macrofauna: > 1 mm
Burrowing: to construct by tunneling, or digging, e.g. polychaetes,
Tubes: siphon tube, large clams-long siphons to prevent clogging respiration pathway, heavy shell to prevent storms
Mobile: move quickly with passing wave, commonly employed by many annelid worms, small clams, and crustaceans. Eg. Sand crabs populate the world beaches, have a short body with limbs highly modified to dig quickly into wet sand. As soon as they are freed from the substrate by a passing wave, they reburrow quickly again before wave motion carries them offshore
Benthic algae (microalgae-diatoms, macroalgae-red algae, green algae, seagrass)
Detritus: small debris of organic matter, from dead organisms
Deposit feeders (by deposit feeding):
Surface deposit feeders
Burrowing deposit feeders
Suspension feeders: filter feeders
Adaptations of organisms
Types of organisms
RPD layer—- reduces compounds diffuse upward from below and as soon as oxygen is available, bacteria oxidize these compounds and the oxidized end products including CO2, NO3 and SO4, in turn are incorporated into bacterial biomass and form the basis of new food chains, some compounds diffuse downward below the RPD zone and utilized by the anaerobic bacteria. These bacteria in turn produce more reduced compounds, which complete the cycle; - chemoautotrophic bacteria in the RPD zone oxidize the reduced compounds and fixing CO2 and produce more organic materials.
Aerobic: a condition with oxygen for organisms, Oxic
Anaerobic condition: a condition depleted of oxygen, Anoxic.
Redox Potential: reduction-oxidation potential, measured by an electrode. It is positive, meaning oxidizing condition; negative-reduction condition
RPD: redox potential discontinuity
RPD layer: a transition zone between the upper aerobic layer and the lower anaerobic layer, characterized by a rapid change from a positive redox potential (Eh) to a negative potential.
Decomposition of organic matter is:
by aerobic bacteria above RPD
by anaerobic bacteria below RPD
Chemoautotrophic bacteria: obtain energy through the oxidation of a number reduced compounds like H2S to produce organic matter. They are primary producers.
Diagrammatic representation of the physical and chemical characteristics of sediments across the redox discontinuity layer and the biological processes occurring in each
Physical factors of sandy beach
Two common polychaete worms of mud flats: Arenicola (right) in its U-shaped burrow, and Capitella (left) burrowing through the substrate.
What a mess!
So guess who is who in terms of feeding types?
Surface deposit feeders:
A: spionid polychaete
E: spionid polychaete
Burrowing deposit feeders:
C: paraonid polychaete
H: syllid polychaete
I: orbiniid polychaete
J: Nephtyid polychaete
G: venerid bivalves
F: haustorid amphipod
K: haustorid amphipod