Lecture 17 ROCKY SUBTIDAL

Substrate Types CobbleWalls Horizontal bedrock Sandy

ZONATION CHART DATUM infralittoral fringe littoral About 200 m Infralittoral Circalittoral Adequate light for photosynthesis Infralittoral + Circalittoral = Subtidal

ZONATION CHART DATUM infralittoral fringe littoral Upper infralittoral Lower infralittoral Upper circalittoral Lower circalittoral Laminaria forest + foliose algae + few animals Foliose algae + few animals Few foliose algae + many animals No algae many animals

Rocky Subtidal - Zones 1) Sublittoral fringe Laminaria Bryozoan Anemone (Metridium)

Rocky Subtidal - Zones 2) Infralittoral Laminaria Anemone (Metridium) Strongylocentrotus droebachiensis Urchin barrens

Rocky Subtidal - Zones 3) Circalittoral Anemone (Metridium) tunicates Sea stars Lamp shells

Determinants of Zonation Slope HorizontalVertical

Determinants of Zonation Slope Differences in species’ patterns 1. Higher light levels on horizontal surfaces 2. Higher sedimentation on horizontal surfaces 3. Photonegative larvae select walls/overhangs 4. More shelter from disturbance

Determinants of Zonation Depth Density Depth 33 m42 m % Cover Depth 28 m45 m Brachiopods Sponges

Local Processes Affecting the Community Temperature Maine (Machias Seal Is) Aug Galapagos (May1999)

Local Processes Affecting the Community Temperature Internal wavesUpwelling

Physical Disturbance Depth LowHigh

Physical Disturbance

Creation of Patches Type I Disturbance -death of some residents -patch surrounded by survivors Type II Disturbance -widespread destruction Recovery - vegetative growth & asexual budding Recovery - long distance dispersers -more stochastic

Physical Disturbance Creation of Patches Wittman (‘98) Patch of anemones Predation by nudibranchs Got Type I patches

Physical Disturbance Creation of Patches Wittman (‘98) ExpectGot Recruitment of planktonic bryozoans, polychaetes and ascidians Asexual/vegetative growth of neighbours

Physical Disturbance Flow Patterns - Reidl ‘71 Primary - effect of flow directly on organisms Secondary - effect of flow on transport of nutrients, gasses, foods Tertiary - effect of flow on substrate

Physical Disturbance Flow Patterns cm/s Minimum Maximum DepthDepth

Physical Disturbance Sedimentation Sedimentation rate = 1/flow

Light Depth Percent surface light Turbid coastal water Clear open ocean water Limit for Laminaria Limit for foliose algae

Rocky Subtidal - communities Terebratulina septentrionalis Community Terebratulina septentrionalis Chiton

Rocky Subtidal - Communities Crustose coralline algae Community Terebratulina septentrionalis Chiton Bryozoans

Rocky Subtidal - Biotic Factors

Biotic Factors on the Subtidal Predictions: 1. Predation - reduced in harsh environments 2. Biotic factors set lower distribution limits 3. Physical factors set upper distribution limits

Biotic Factors on the Subtidal 1. Predation - reduced in harsh environments LowHigh Predator pressure

Biotic Factors on the Subtidal 1. Predation - reduced in harsh environments PREDATOR SURVIVAL Number of waves Time (Months) Denny et al, 1985 Survivorship L r /2 LrLr 2L r L r /2 LrLr 2L r Colisella digitalis

Predator density Galapagos Seychelles Gulf of Maine Biotic Factors on the Subtidal 1. Predation - reduced in harsh environments Absence of predators

Biotic Factors on the Subtidal 1. Predation - reduced in harsh environments minuteshoursdays Birds Crabs/lobster Snails/urchins /seastars Impact of predator on prey (per capita prey removal rate) Return time of limiting stress

Biotic Factors on the Subtidal 1. Predation - reduced in harsh environments New Zealand

Biotic Factors on the Subtidal 1. Predation - reduced in harsh environments urchins, sea stars, lobsters freshwater mussels New Zealand

Biotic Factors on the Subtidal Predictions: 1. Predation - reduced in harsh environments 2. Biotic factors set lower distribution limits 3. Physical factors set upper distribution limits √

Biotic Factors on the Subtidal Predictions: 1. Predation - reduced in harsh environments 2. Biotic factors set lower distribution limits 3. Physical factors set upper distribution limits

Biotic Factors on the Subtidal 2. Biotic factors set lower distribution limits Anderson Ledge, New Hampshire Laminaria - limit dictated by urchin grazing Urchins - stay near bottom of Laminaria - physical stress too high to go shoreward Mytilus - colonized areas grazed by urchins Sea stars - prevent Mytilus recruitment lower in subtidal

Biotic Factors on the Subtidal 2. Biotic factors set lower distribution limits Scheibling et al, 1999 Mill Cove Little Duck Island

Biotic Factors on the Subtidal 2. Biotic factors set lower distribution limits Strongylocentrotus droebachiensis Laminaria longicruris

Biotic Factors on the Subtidal 2. Biotic factors set lower distribution limits Scheibling et al, 1999 kelp grazed edge

Biotic Factors on the Subtidal 2. Biotic factors set lower distribution limits Scheibling et al, 1999

Biotic Factors on the Subtidal 2. Biotic factors set lower distribution limits But …. within limits set by physical factors Vadas & Steneck, depth greater without grazers

Biotic Factors on the Subtidal 2. Biotic factors set lower distribution limits But …. within limits set by physical factors Miller and Hay, 1996 Oculina

Biotic Factors on the Subtidal Predictions: 1. Predation - reduced in harsh environments 2. Biotic factors set lower distribution limits 3. Physical factors set upper distribution limits √ (with qualifications)

Biotic Factors on the Subtidal Predictions: 1. Predation - reduced in harsh environments 2. Biotic factors set lower distribution limits 3. Physical factors set upper distribution limits √ (with qualifications)

Biotic Factors on the Subtidal 2. Competition LowHigh Competition for space

Biotic Factors on the Subtidal 2. Competition Competition for space (among algae) a. allelopathy

Biotic Factors on the Subtidal 2. Competition Competition for space (among algae) b. overgrowth

Biotic Factors on the Subtidal 2. Competition Competition for space (among algae) c. overtopping

Biotic Factors on the Subtidal 2. Competition Competition for space (among algae) d. Algal whiplash

Biotic Factors on the Subtidal 2. Competition Competition for space e. Aggression (Cnidaria) acrorhagi

Biotic Factors on the Subtidal 3. Recruitment LowHigh % space covered

Biotic Factors on the Subtidal 3. Recruitment LowHigh % space covered effect of predators

Biotic Factors on the Subtidal 3. Recruitment Osman & Whitlach, 1995 Mitrella Anachis Without predators With predators

Mesoscale Processes High flow Low flow km’s

Other mesoscale processes Disease Productivity Thermoclines