Kelp & Seaweed Ecosystems
 Seaweed refers to a diverse group of red, green, & brown algae. All
provide the bases for ecosystems among their stipes, holdfasts, &
blades.
 Among these, kelp ecosystems are probably the most diverse.
You find kelp forests globally in cool water. This is because they
require the nutrients found in a cool ocean.
 Kelp forests & other seaweed-based ecosystems are among the
most biologically productive ecosystems.
 Their primary production exceeds the primary productivity of
terrestrial forests & is almost equal to the productivity of coral
reefs.
Kelp & Seaweed Ecosystems
 Because of its dependence on sunlight, cool water, &
nutrients, kelp responds noticeably to environmental changes.
 During ENSO events, for example, the coastal water temperatures
in Southern California rise. This often causes massive die offs of
kelp, disrupting the local ecosystems for a year or more.
 Kelp provides a clear example of why it’s important to
study ecology, not simply individual organisms.
 Until protected, in some areas the sea otter was hunted
nearly to extinction. Amazingly, in these areas the kelp
began to die off rapidly.
Kelp & Seaweed Ecosystems
 It turns out that while very few organisms eat kelp, one that
does is the sea urchin.
 Sea urchins are one of the sea otter’s primary foods, once
the sea otter population declined, the sea urchin population
increased & decimated the kelp population.
 The energy required by marine mammals living in cool
seawater is considerable, so the average sea otter eats a
substantial number of sea urchins.
Kelp & Seaweed Ecosystems
 Killing the sea otters disrupted the kelp forest’s ecological
balance by removing the sea urchin’s chief predator.
 This allowed the sea urchin population to rise relatively
unchecked. More sea urchins meant more grazing on kelp
holdfasts. In the end, the sea urchins ate the kelp faster than
it could grow.
 This is an excellent example of the interdependence that
exists within an ecosystem. It shows that each organism
contributes to a balance that allows life to thrive there.