An urchin barren is an area of the shallow part of the ocean where the population growth of sea urchins has gone unchecked, causing destructive grazing of kelp forests.
Sea urchins eat kelp holdfasts.[1] This can be caused by a lack of sea otters or other predators in the area,[2] which makes it extremely important to protect the ecological balance in a kelp forest. Keystone species such as the sea otter help maintain healthy kelp communities; however, likely because of increased killer whale predation, their numbers are in decline in areas of Western Alaska.[3] Off the California coast, storm runoff, erosion and polluted water allow less light to penetrate, weakening the kelp.[4] Sea urchins then can move in and settle.[5]
Despite their name, urchin barrens are usually abundant with marine invertebrate life, echinoderms in particular.[6] Species such as the sunflower starfishes, brittle stars, and the purple sea urchin are common. Although macrofauna such as these are aplenty, there is little primary productivity among microorganisms.[7] This makes it difficult for newly settled sea urchins (juveniles) to survive, making barrens more dangerous for juveniles than for adults.[8] Once having wiped out a kelp forest, the environment becomes unsupportive of new sea urchin settlement and adults are forced to find a new resource.
Shift theories
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.[9] The continuous phase shift is widely accepted. This describes a transition from one ecosystem state to another where the threshold for the forward shift is at the same level as the threshold for the reverse shift back to the previous state. In other words, a kelp bed can re-establish itself when urchin grazing intensity decreases to the threshold density triggering the initial shift.
Alternatively, another theory posits that both sea urchin barrens and kelp-beds represent alternative stable states, meaning that an ecosystem can exist under multiple states, each with a set of unique biotic and abiotic conditions (i.e. barren except for urchins or flourishing with kelp). Those who argue for this theory propose several criteria: that different self-replacing communities dominate the site; each state exists longer than one complete turnover of the dominant community or species; and that following a disturbance (e.g. a storm), the system returns to the previous state.
Impacted areas
Over the past four decades, barrens have been reported along coastlines around the world, everywhere from Nova Scotia to Chile. They can either span over a thousand kilometers of coastline or occur in small patches.[10]
^Stewart, NL; Konar B (2012). "Kelp Forests versus Urchin Barrens: Alternate Stable States and Their Effect on Sea Otter Prey Quality in the Aleutian Islands". Journal of Marine Biology. 2012: 1–12. doi:10.1155/2012/492308.
^Estes, J. A.; Tinker, M. T.; Williams, T. M.; Doak, D. F. (1998-10-16). "Killer Whale Predation on Sea Otters Linking Oceanic and Nearshore Ecosystems". Science. 282 (5388): 473–476. Bibcode:1998Sci...282..473E. doi:10.1126/science.282.5388.473. ISSN 0036-8075. PMID 9774274.
^Barboza, Tony (2013-08-16). "Purple sea urchins spoiling kelp forest". Los Angeles Times. Retrieved 2015-12-04 – via SFGate.
^"Plague of purple sea urchins ravages California's offshore ecosystem, heads to Oregon". Associated Press. 2019-10-24. Retrieved 2019-10-26 – via Los Angeles Times.
^Archived at Ghostarchive and the : Army of Sea Urchins? | Planet Earth | BBC. YouTube.
^FilbeeDexter, Karen; Scheibling, Robert E. (2014-01-09). "FEATURE ARTICLE: REVIEW Sea urchin barrens as alternative stable states of collapsed kelp ecosystems". Marine Ecology Progress Series. 495: 1–25. doi:10.3354/meps10573.
^Rowley, R.J. (1990). "Newly settled sea urchins in a kelp bed and urchin barren ground: a comparison of growth and mortality". Marine Ecology Progress Series. 62: 229–240. Bibcode:1990MEPS...62..229R. doi:10.3354/meps062229.
^FilbeeDexter, Karen; Scheibling, Robert E. (2014-01-09). "FEATURE ARTICLE: REVIEW Sea urchin barrens as alternative stable states of collapsed kelp ecosystems". Marine Ecology Progress Series. 495: 1–25. doi:10.3354/meps10573.
^Stewart, Nathan L.; Konar, Brenda (2012-02-28). "Kelp Forests versus Urchin Barrens: Alternate Stable States and Their Effect on Sea Otter Prey Quality in the Aleutian Islands". Journal of Marine Biology. 2012: 1–12. doi:10.1155/2012/492308.
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An urchin barren is an area of the shallow part of the ocean where the population growth of sea urchins has gone unchecked causing destructive grazing of kelp forests An urchin barren in formation Contents 1 Process 2 Shift theories 3 Impacted areas 4 ReferencesProcess EditSea urchins eat kelp holdfasts 1 This can be caused by a lack of sea otters or other predators in the area 2 which makes it extremely important to protect the ecological balance in a kelp forest Keystone species such as the sea otter help maintain healthy kelp communities however likely because of increased killer whale predation their numbers are in decline in areas of Western Alaska 3 Off the California coast storm runoff erosion and polluted water allow less light to penetrate weakening the kelp 4 Sea urchins then can move in and settle 5 Despite their name urchin barrens are usually abundant with marine invertebrate life echinoderms in particular 6 Species such as the sunflower starfishes brittle stars and the purple sea urchin are common Although macrofauna such as these are aplenty there is little primary productivity among microorganisms 7 This makes it difficult for newly settled sea urchins juveniles to survive making barrens more dangerous for juveniles than for adults 8 Once having wiped out a kelp forest the environment becomes unsupportive of new sea urchin settlement and adults are forced to find a new resource Shift theories EditAn 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 9 The continuous phase shift is widely accepted This describes a transition from one ecosystem state to another where the threshold for the forward shift is at the same level as the threshold for the reverse shift back to the previous state In other words a kelp bed can re establish itself when urchin grazing intensity decreases to the threshold density triggering the initial shift Alternatively another theory posits that both sea urchin barrens and kelp beds represent alternative stable states meaning that an ecosystem can exist under multiple states each with a set of unique biotic and abiotic conditions i e barren except for urchins or flourishing with kelp Those who argue for this theory propose several criteria that different self replacing communities dominate the site each state exists longer than one complete turnover of the dominant community or species and that following a disturbance e g a storm the system returns to the previous state Impacted areas EditOver the past four decades barrens have been reported along coastlines around the world everywhere from Nova Scotia to Chile They can either span over a thousand kilometers of coastline or occur in small patches 10 References Edit Planet Earth 2006 TV series 2006 Shallow Seas Television production BBC Natural History Unit Stewart NL Konar B 2012 Kelp Forests versus Urchin Barrens Alternate Stable States and Their Effect on Sea Otter Prey Quality in the Aleutian Islands Journal of Marine Biology 2012 1 12 doi 10 1155 2012 492308 Estes J A Tinker M T Williams T M Doak D F 1998 10 16 Killer Whale Predation on Sea Otters Linking Oceanic and Nearshore Ecosystems Science 282 5388 473 476 Bibcode 1998Sci 282 473E doi 10 1126 science 282 5388 473 ISSN 0036 8075 PMID 9774274 Barboza Tony 2013 08 16 Purple sea urchins spoiling kelp forest Los Angeles Times Retrieved 2015 12 04 via SFGate Plague of purple sea urchins ravages California s offshore ecosystem heads to Oregon Associated Press 2019 10 24 Retrieved 2019 10 26 via Los Angeles Times Archived at Ghostarchive and the Wayback Machine Army of Sea Urchins Planet Earth BBC YouTube FilbeeDexter Karen Scheibling Robert E 2014 01 09 FEATURE ARTICLE REVIEW Sea urchin barrens as alternative stable states of collapsed kelp ecosystems Marine Ecology Progress Series 495 1 25 doi 10 3354 meps10573 Rowley R J 1990 Newly settled sea urchins in a kelp bed and urchin barren ground a comparison of growth and mortality Marine Ecology Progress Series 62 229 240 Bibcode 1990MEPS 62 229R doi 10 3354 meps062229 FilbeeDexter Karen Scheibling Robert E 2014 01 09 FEATURE ARTICLE REVIEW Sea urchin barrens as alternative stable states of collapsed kelp ecosystems Marine Ecology Progress Series 495 1 25 doi 10 3354 meps10573 Stewart Nathan L Konar Brenda 2012 02 28 Kelp Forests versus Urchin Barrens Alternate Stable States and Their Effect on Sea Otter Prey Quality in the Aleutian Islands Journal of Marine Biology 2012 1 12 doi 10 1155 2012 492308 This oceanography article is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Urchin barren amp oldid 1121123820, wikipedia, wiki, book, books, library,
