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An area of the subtidal where the population growth of sea urchins has gone unchecked causes destructive grazing of kelp beds or kelp forests (specifically the giant brown bladder kelp, Macrocystis). The transition from kelp forest to barren is defined by phase shifts in which one stable community state is shifted to another. [2]
In Alaskan kelp forest ecosystems, sea otters are the keystone species that mediates this trophic cascade. In Southern California, kelp forests persist without sea otters and the control of herbivorous urchins is instead mediated by a suite of predators including lobsters and large fishes, such as the California sheephead.
Urchins have hurt both species, though giant kelp forests have fared better. Some believe the only way to restore kelp is to reduce the purple urchins, which can go dormant for years only to ...
With high sea otter densities the herbivory of sea urchins in these kelp forest was severely limited, and this made competition between algal species the main determinant in survival. However, when sea otters were absent, herbivory of the sea urchins was greatly intensified to the point of decimation of the kelp forest community.
The purple sea urchin, along with sea otters and abalones, is a prominent member of the kelp forest community. [18] The purple sea urchin also plays a key role in the disappearance of kelp forests that is currently occurring due to climate change; [19] when urchins completely eliminate kelp from an area, an urchin barren results.
These days, long-spined sea urchins are known as the gardeners of the sea. They tend the algae on the coral reefs they call home, making sure it never overwhelms their hosts. Spotting one on the ...
One of the sea otters’ primary food sources is the sea urchin. When hunters caused sea otter populations to decline, an ecological release of sea urchin populations occurred. The sea urchins then overexploited their main food source, kelp , creating urchin barrens, areas of seabed denuded of kelp, but carpeted with urchins.
For marine scientists, it was deja vu: Another die-off swept through the region in the 1980s and slashed sea urchin populations by around 98%. Mystery solved: Scientists ID Caribbean sea urchin killer