ch14 - 14-The TidelandsRocky Shores Soft-Substratum...

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Unformatted text preview: 14-The TidelandsRocky Shores, Soft-Substratum Shores,Marshes, Mangroves, and EstuariesNotes for Marine Biology:Function, Biodiversity, EcologyBy Jeffrey S. Levinton©Jeffrey S. Levinton 2001ZONATION-universal feature of rocky shores, also true of soft sediments but not as distinct (3-dimensional nature, owing to presence of burrowing organisms and others within the ZONATION-universal feature of rocky shores, also true of soft sediments but not as distinct (3-dimensional nature, owing to presence of burrowing organisms and others within the sediment)2 SPATIAL GRADIENTS:• Vertical• Horizontal - changing wave exposureVertical gradient• Heat Stress, Desiccation• Gas Exchange - dissolved oxygen• Reduced feeding time• Wave shock• Biological interactions - competition,predationHeat Stress/Desiccation• Varies on small spatial scales• Body size, shape are both important -reduction of surface area/volume reducesheat gain and water loss• Evaporative cooling and circulation of bodyfluids aids in reduction of heat loss• Well sealed exoskeletons aid in retardingwater loss (acorn barnacles, bivalves)Vertical Gradients•Higher intertidal organisms - more resistant toheat and desiccation stress than lowerintertidal organisms•Higher intertidal - less time to feed. Sessileforms therefore grow more slowly than lowerintertidal organisms•Mobile carnivores can feed only at high tide,usually feed more effectively at lower tide levels,which are immersed a greater proportion of thedayOxygen consumption•Intertidal animals usually cannot respire attime of low tide•Respiratory organs (gills of polychaetes,bivalves) must be moist to acquire oxygen, andtherefore are usually withdrawn at low tide•Some animals - reduce metabolic rate at time oflow tide•Some high intertidal animals can respirefrom air (e.g., some mussels) even at lowtide, as long as air is not too dryWave shock•Abrasion - particles in suspension scrapedelicate structures•Pressure - hydrostatic pressure of breakingwaves can crush compressible structures•Drag - impact of water can exert drag, whichcan pull organisms from their attachments tosurfaces, erode particles from beaches andcarry organisms from their burrows or livingpositionsCauses of Vertical Zonation•Physiological tolerance of different species atdifferent levels of the shore•Larval and adult preference - larvaemay settleat time of high tide at high levels, mobilejuveniles/adultshave a series of behavioralresponses that keep them at certain levels ofshore•Competition - species may be capable ofexcluding others from certain levels of theshore•Predation - mobile predators more effectiveusually on the lower shore: affects distributionsof vulnerable prey speciesInterspecific Interactions andZonation•Why are there vertical zones, withdominance often of single sessile specieswithin a zone?Interspecific Interactions andZonation 2• Why are there vertical zones, withdominance often of single sessile specieswithin a zone?within a zone?...
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This note was uploaded on 09/09/2008 for the course BIO 353 taught by Professor Levinton during the Spring '08 term at SUNY Stony Brook.

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ch14 - 14-The TidelandsRocky Shores Soft-Substratum...

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