Echinoderms (Benthic Ecology)

Question 1

diadema: role in Jamaica

Answer 1

eat algae which increases coral recruitment

competition between coral and algae

Question 2

pisaster: role in upper intertidal pacific coast

Answer 2

eats muscles

more vulnerable to desiccation, can only reach lower muscles

less preferred food: barnacles, chitons, snails
will live in “harmony with these guys if muscles available.

Question 3

Heliaster in Chile

Answer 3

not as limited by desiccation, can eat full muscle bed

Question 4

Pisaster

Answer 4

infrequent, sporadic recruitment

long lifespan

size determined by food source

doesn’t move around much, small terrain barriers can separate populations.

Question 5

Pisaster die-off

Answer 5

probably a virus

west coast

killing >95% of Pisaster (and infectingother species as well)

will have ecological coinsequnces

Question 6

Pacific coast lower intertidal: Pycnopodia and Urchins

Answer 6

Pcynopodia eats/tramples urchins
-also wiped out by an infectious disease

urchins graze on algae

Question 7

Pacific coast subtidal

Answer 7

Top predator (otters or lobsters) > sea urchins > kelp

Question 8

subtidal alaska

Answer 8

presence of appex predator (otters) determines dominace of fish or crustaceans/mollusks at a site

otters = less urchins = more kelp = less wave action = more fish (attracts seals and eagles)

Question 9

Indo-Pacific: Acanthaster

Answer 9

crown of thorns

eats coral, can destroy coral reefs

Hawaii- many Acanthaster but no coral die-off, reason unknown

Question 10

Urchin barrens

Answer 10

large urchin pops. = urchins eat all the kelp

they can survive starving for a long time

sometimes they resort to cannibalism

high density populations also increases URCHIN INFECTIOUS DISEASES

Question 11

Urchin small scale effects (3)

Answer 11

graze mini barrens that corals like to settle in

eat coralline algae (attracts abalone larvae)

large urchins provide protection for smol guys

Question 12

Acanthaster outbreaks (2 major causes)

Answer 12

occur 2-3 years after heavy rains

Why:

• rains wash nutrients into the ocean = increase in phytoplankton
• runoff decreases salinity

both lead to acanthaster larval success boom = in 2-3 they grow into adults

ALSO caused by removal of starfish predators such as Triton snails and Harlequin shrimp

core data shows these outbreaks are normal

Question 13

general ecological effects

Answer 13

predation: starfish
herbivory: urchins