Post on 01-Jan-2016
Lecture 9 –INTERTIDAL ZONATIONBIOLOGICAL FACTORS
reproductive mode
competition larval settlement
predation
survival
grazing
BIOLOGICAL FACTORS
1. Grazing
-growth of Laminaria- zone ends abruptly
Why?
1. Grazing
Experiment done in New South Wales, Australia
Underwood (1980 Oecologia 46:201)
Used exclusion cages
1- Open 2 - Fence 3 - Roof 4 - Cage
Grazers excluded Grazers excludedGrazers inGrazers in
Normal ShadeShadeNormal
1- Open 2 - Fence 3 - Roof 4 - Cage
Grazers excluded Grazers excludedGrazers inGrazers in
Normal ShadeShadeNormal
No growth or recruitment
Recruitment but poor growth
No growth or recruitment
Recruitment and growth to nearly adult size
Therefore - upper limit dictated by exposure + grazers
2. PredationPisaster ochraceous on Mytilus californianus
R. Paine
2. PredationPisaster ochraceous on Mytilus californianus
2. PredationPisaster ochraceous on Mytilus californianus
Time (Years)
0 2 4 6 8 10
Height above chart datum
1.5
1.0
0.5
Pisaster removal begins Pisaster removal ends
3. Competition
Chthalamus Semibalanus
3. Competition
Millport, Isle of Cumbrae
3. Competition
EHWS
MTL
ELWS
Chthalamus zone
Semibalanus zone
3. Competition
EHWS
MTL
ELWS
Chthalamus zone
Semibalanus zone
Remove Semibalanus
3. Competition
EHWS
MTL
ELWS
Chthalamus zone
Semibalanus zone
Remove Chthalamus
3. Competition
Lifted Smothered Crushed ??
100
50
0
Source of Mortality
3. Competition
MHWS
MTL
MHWN
MLWN
MLWS
Larval settlement Effects of physical factors Competition
Chthamamus
Semibalanus
Distribution of Semibalanus and Chthalamus
Wethey 1983. Biol.Bull. 165:330
Semibalanus
Chthalamus
Wethey 1983. Biol.Bull. 165:330
Nahant, Mass.No Chthalamus
Guilford & Horse Island, Conn.Semibalanus & Chthalamus coexist
Distribution of Semibalanus and Chthalamus
Perc
ent c
over
by
each
spe
cies
100
50
100
50
100
50
Tidal Height
MHWN MLWN
Vertical-North
Vertical-West
10º Slope-South
ChthalamusSemibalanus
Wethey 1983. Biol.Bull. 165:330
Distribution of Semibalanus and Chthalamus
100
50
100
50
ChthalamusSemibalanus
Drip
DryPe
rcen
t cov
er b
y ea
ch s
peci
es
Tidal Height
MHWN MLWN
Wethey 1983. Biol.Bull. 165:330
Distribution of Semibalanus and Chthalamus
Wethey 1983. Biol.Bull. 165:330
Perc
ent c
over
by
each
spe
cies
Tidal Height
MHWN MLWNChthalamusSemibalanus
Increasing sun exposure
Distribution of Semibalanus and Chthalamus
Wethey 1983. Biol.Bull. 165:330Tidal Height
MHWN MLWN
Vertical-North
Vertical-West
10º Slope-South
ChthalamusSemibalanus
Set
tlem
ent d
ensi
ty (
no.
/cm
2
1.0
0.5
2.0
1.0
1.0
0.5
Distribution of Semibalanus and Chthalamus
4. Larval Settlement
Generalized life cycle for marine invertebrates
Dispersing larva (planktonic)
settle
juvenileadult
egg
4. Larval Settlement
Larval settlement Final distribution pattern
happens because of
1. Indiscriminate settlementand high mortality
2. Discriminate settlementand low mortality
4. Larval Settlement
Flustrellidra lives on Ascophyllum
Distribution of Bryozoans
Hurlbut 1991. J.Exp. Mar. Biol. Ecol. 147:103
4. Larval Settlement
Hurlbut ‘91 - Distribution of Bryozoans
Alcyonidium
Chondrus
FucusRock
Geukensia
Hurlbut 1991. J.Exp. Mar. Biol. Ecol. 147:103
4. Larval Settlement
Hurlbut 1991. J.Exp. Mar. Biol. Ecol. 147:103
4. Larval Settlement
Hurlbut ‘91 - Distribution of Bryozoans
FlustrellidraAscophyllum
Hurlbut 1991. J.Exp. Mar. Biol. Ecol. 147:103
4. Larval Settlement
Results
Flustrellidra
- larvae selectively settle on Ascophyllum- greater survivorship on Ascophyllum
Alcyonidium
-larvae show preferential settlement on Fucus and Chondrus - most adult colonies occur on rock
Hurlbut 1991. J.Exp. Mar. Biol. Ecol. 147:103
Summary
Observed distribution andabundance
temperaturedesiccation ice
wave exposure
reproductive modecompetition
larval settlementpredationsurvival
grazing