Survey
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Rocky Shores Abiotic Factors and Zonation • All ocean shores are exposed to tides • Intertidal zone or littoral zone – zone between high and low tide marks • Conditions are always changing • When the tide is high, it is covered in water • When the tide is low, it is moist and salty • Those that are in the upper region experience the sun and drying wind the longest time • The littoral zone has several zones within it • Rocky shores show the greatest variation, so they have the widest variety of habitats for algae to live and animals can feed • Rocky shores have three main zones: • Intertidal zone – covered and exposed by water, throughout the day • Spray zone is above it • Below it is the sublittoral zone or ocean ocean • The zones are quite similar throughout the world • Rocky shores can have steep cliffs or be flat • May have crevices and gullies • Waves erode rocky shores • Tide pools are water-filled depressions that are present on rocky shores when the tide recedes Section Review • What is the intertidal or littoral zone? • Which organisms in the intertidal zone experience the greatest changes in abiotic factors? Why? • What causes the zonation within the littoral zone? • What is a tide pool? • What are the three main zones of a rocky shore? Zonation • Conditions are always changing • Exposed to sunlight, rain, wind, and temperature changes • Tides and waves bring changes in salinity, temperature, and light • Dessication is a loss of moisture and is a big problem – some bury themselves, some move with the tide, and others have adapted to prevent dessication • Six subzones: – – – – – – Black zone Barnacle zone Rockweed zone Irish moss zone Blue mussel zone Kelp zone Black Zone • Calothrix is often present • Upper most of the zones • Every two weeks the spring tides cover this zone • Also gets wet from waves and spray • Blue-green algae and lichens live here, and give the rocks their black colour Calothrix Black Zone • Calothrix: • Consists of filaments of microscopic cells • Filaments are surrounded by sticky gelatinous sheath • This allows it to stick to the surface, protects it from drying out, and protects it from changing salt levels • “fixes nitrogen” so lack of nutrients is not a problem Black Zone • Rough periwinkle • Main herbivore • Eats Calothrix for its nitrogen content • Shell is thick and has a small opening to prevent water loss • Can seal itself to a rock with mucus if it gets too dry Barnacle Zone • Covered and uncovered daily by the tides • Barnacles are crustaceans • Live stuck to the rocks and depend on tides for food • Barnacles open up during high tide and sweep microscopic organisms such as diatoms and dinoflagellates into it • They close during low tide to prevent water loss Barnacle Zone • Limpets, dog whelks, periwinkles, and blue mussels may be found here • Limpets scrape algae from rocks • Dog whelks eat barnacles, mussels, and periwinkles • Blue mussels will be small, and are filter feeders Rockweed Zone • Brown algae called rockweeds live here • Usually 30-40cm long • Bladder rockweed is very common on the east coast • Thick cell walls to prevent water loss • Air bladders help it float • It sticks to a rocky surface with a holdfast • Smooth periwinkle is a characteristic animal of this zone • Graze on rockweeds • Move under the rockweeds when the tide is out to retain moisture • Limpets are found here as well, feeding on the rockweed • (Limpets are like a snail) Irish Moss Zone • Chondrus crispus is a red algae (known as Irish Moss) • With Gigartina stellata form a spongy carpet • Zone can be purple, or green and yellow • Out of the water for a few hours a day • Not tolerant of temperature extremes or dryness • Algae retain their water at low tide Chondrus crispus Irish Moss Zone • Isopods, amphipods and decapods live here • Irish moss contains carrageenin – which forms a gel; used in ice cream, toothpaste, chocolate milk, evaporated milk, and body lotions Blue Mussel Zone • May overlap the Irish moss zone • May sometimes go up to the bottom of the barnacle zone • Can be tightly packed • Attach to rocks with threads made of protein • Mytilus edulis is very common Mytilus edulis Blue Mussel Zone • Underwater most of the time, or waves will be covering it • Mussels are filter feeders – their respiration passes water over the gills, the gills filter out food particles (phytoplankton, bacteria, detritus) • Main predators are whelks, starfish, and humans • Whelks bore through their shells and removes the interior of the mussel • Starfish pry open the shell, and releases its stomach through its mouth and into the mussel, then takes its stomach back Kelp Zone • Lowest zone • Brown algae, Laminaria • May be uncovered once every two weeks during spring tide, but waves may keep it covered • Kelp provides food and habitat • Limpets, mussels, isopods, amphipods, crabs, and starfish live here • Starfish move from kelp beds to mussel zone during high tide Kelp Zone • Kelp and other brown algae are collected for food • Used to provide iodine • High protein and vitamin content • Feed for domestic animals • Ground to make fertilizer • Alginic acid is used as a stablilizer in ice cream and some paint; and found in some antibiotics