Lecture 7 ROCKY INTERTIDAL

RELATIVE TIDE LEVELS

-EFFECT OF SLOPE MHWS MHWN MTL MLWN MLWS ZONES CAN BE SEVERAL TENS OF METRES WIDE ZONES CAN BE LESS THAN A METRE WIDE

RELATIVE TIDE LEVELS -EFFECT OF SLOPE

Slope and Substrate SSlope Substrate Size Wave Action If you know any two factors, you can determine the third.

Slope and Substrate Steep slope Strong wave action Coarse substrate Water drains at low tide Gradual slope Weak wave action Fine substrate Water retained at low tide

Slope and Substrate Decreasing sediment size

Slope and Substrate High wave/ steep slope

Slope and Substrate Low wave/ gentle slope

Stephenson and Stephenson Classification of Rocky Intertidal Shores EHWS ELWS Infralittoral Upper limit - Laminaria Mytilus Ascophyllum Barnacles Upper limit - Barnacles Upper limit - Littorina Infralittoral fringe Midlittoral Supralittoral fringe Supralittoral After Stephenson & Stephenson (1949)

Stephenson and Stephenson Classification of Rocky Intertidal Shores a. Supralittoral Zone Xanthoria

Stephenson and Stephenson Classification of Rocky Intertidal Shores b. Supralittoral Fringe Calothrix Verrucaria Littorina

Stephenson and Stephenson Classification of Rocky Intertidal Shores b. Supralittoral Fringe Bottom of zone Fucus spiralis Semibalanus balanoides

Stephenson and Stephenson Classification of Rocky Intertidal Shores c. Midlittoral - begins at upper limit of barnacles

Stephenson and Stephenson Classification of Rocky Intertidal Shores c. Midlittoral 4 dominant species Semibalanus balanoides -northern rock barnacle Ascophyllum nodosum - knotted wrack

Stephenson and Stephenson Classification of Rocky Intertidal Shores c. Midlittoral 4 dominant species Mytilus edulis -blue mussel Fucus vesiculosus - bladder wrack

Stephenson and Stephenson Classification of Rocky Intertidal Shores c. Midlittoral Other common species Acmaea -limpet Littorina littorea -periwinkle

Stephenson and Stephenson Classification of Rocky Intertidal Shores c. Midlittoral Other common species Thais -whelk

Stephenson and Stephenson Classification of Rocky Intertidal Shores c. Midlittoral On stalks of Ascophyllum Sertularia Flustrellidra Polysiphonia

Stephenson and Stephenson Classification of Rocky Intertidal Shores c. Midlittoral Lower midlittoral Porphyra Palmaria

Stephenson and Stephenson Classification of Rocky Intertidal Shores d. Infralittoral Laminaria - kelp

Stephenson and Stephenson Classification of Rocky Intertidal Shores d. Infralittoral Strongylocentrotus droebachiensis Ulva

Stephenson and Stephenson Classification of Rocky Intertidal Shores d. Infralittoral Asterias vulgaris

Critical Tide Levels (Doty, Ecology 27: ) Length of maximum submergence Tide level Critical tide levels

(Doty, Ecology 27: ) Doty – Algal distributions

Druehl & Green, Mar.Ecol. Prog Ser. 9: 163 More realistic data on submergence

Druehl & Green, Mar.Ecol. Prog Ser. 9: 163

Next time Intertidal Zonation – Physical Factors