Shallow Subtidal Sandy Community:Zuma Beach

Jon Kastendiek, Ph.D.

Dendraster Community – Zuma Beach

Dendaster – Suspension feeder - aboral

Dendaster – Suspension feeder - aboral

Astropecten – Predator of Renilla

Renilla kollokeri – suspension feeder

Armina – Predator of Renilla

Dendraster Community – Zuma Beach

Wave Zone

WINTER

Renilla<2cm

Renilla and Armina

Dendraster

Astropecten and Renilla>4cm

Wave Zone

SUMMER

Wave Zone

WINTER

Factors affecting distributions

• Physical factors– Surge/downwelling– Substrate type– Depth

• Biological factors– Predation– Competition– Symbioses

Experimental Manipulations

Physical factors

Wave Zone

SUMMER

Wave Zone

EXPERIMENT:

Transplant Dendraster

Wave Zone

EXPERIMENT:

Transplant Astropecten

Wave Zone

EXPERIMENT:

Remove Dendraster

Wave Zone

EXPERIMENT:

Transplant

Renilla>2cm

Wave Zone

EXPERIMENT:

Transplant Armina

Experimental Manipulations

Biological factors

Armina, Astropecten and Renilla feeding predation synergy

Feeding synergy between Armina and Astropecten on Renilla (<4cm rachis diam.)

Wave Zone

EXPERIMENT:

Dendraster removal; Renilla transplant

Competition Experiments

Controlled Field Experiments (Manipulations)

Wave Zone

WINTER

Renilla<2cm

Renilla and Armina

Dendraster

Astropecten and Renilla>4cm

Wave ZoneEXPERIMENT:

Result of Dendraster removal

Wave Zone

EXPERIMENT:

Dendraster removal; Renilla transplant

No further removal of Dendraster

Renilla excluded

Wave Zone

EXPERIMENT:

Dendraster removal; Renilla transplant

Continuous removal of Dendraster

Renilla persists

Wave Zone

WINTER

Renilla<2cm

Renilla and Armina

Dendraster

Astropecten and Renilla>4cm

Conclusions

• Upward distribution bound of Renilla, Astropecten and Dendraster dictated by physical factor of current/surge

• Astropecten distribution also lower due to competition for space with Dendraster

• Only large Renilla (>4cm) found below Dendraster due to Astropecten predation

• Small Renilla (>2cm) have refuge from predators in upper area due to surge

Wave Zone

SUMMER

Wave Zone

WINTER

END