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Article: No ‘silver bullet’: multiple factors control population dynamics of European purple sea urchins in Lough Hyne Marine Reserve, Ireland

TitleNo ‘silver bullet’: multiple factors control population dynamics of European purple sea urchins in Lough Hyne Marine Reserve, Ireland
Authors
KeywordsParacentrotus lividus
Sea urchins
Mass mortality
Marine reserve
Marthasterias glacialis
Hypoxia
Issue Date2019
PublisherAcademic Press. The Journal's web site is located at http://www.elsevier.com/locate/ecss
Citation
Estuarine, Coastal and Shelf Science, 2019, v. 226, article no. 106271 How to Cite?
AbstractTwo-decade-long monitoring studies at Europe's first statutory marine reserve—Lough Hyne in SW Ireland—indicate that benthic communities are rapidly changing. Populations of the ecologically important purple urchin (Paracentrotus lividus) have fluctuated widely, most recently with a population boom in the late 1990s, followed by a mass mortality that persists to the present day. Eight general hypotheses have been proposed to account for the urchin decline including cold temperature limiting reproduction, ephemeral algal exudates disrupting urchin fertilization, low larval availability (due to over-harvesting and/or episodic recruitment), high mortality of settlers and juveniles due to hypoxia, hyperoxia, or predation (a trophic cascade hypothesis), and increased mortality due to pathogens (stress hypothesis). The cold-temperature and the trophic cascade hypotheses appear unlikely. The remaining hypotheses, however, all seem to play a role, to some degree, in driving the urchin decline. Ulvoid exudates, for example, significantly reduced urchin fertilization and few larvae were found in plankton tows (2012–2015), indicating low larval availability in summer. Whilst settling urchins regularly recruited under shallow-subtidal rocks until 2011, no settlers were found in these habitats from 2011 to 2014 or in field experiments (2012–2018) using various settlement substrata. Seawater quality was poor in shallow areas of the lough with extreme oxygen fluctuations (diel-cycling hypoxia), and 1-day experimental exposures to DO values < 1 mg L−1 were lethal to most juvenile urchins. Multiple increases of the predatory spiny starfish (Marthasterias glacialis) population in recent decades may also have contributed to the demise of the coexisting juvenile urchins. Finally, urchins of all sizes were seen suffering from dropped spines, tissue necrosis, or white-coloured infection, suggestive of stress-related pathogen mortality. There was a paucity of broken tests, indicating limited predation by large crustaceans; the large number of adult urchins ‘missing’ and few P. lividus tests on the north shore points to possible urchin removal by poachers and/or starfish predation. While these ecological, environmental, and anthropogenic processes occur on open coast rocky shores, many are exacerbated by the semi-enclosed nature of this fully marine sea lough due to its limited flushing. Multiple factors, including low larval availability and rapidly expanding starfish populations, coupled with degraded habitat quality (ephemeral algal mats and extreme oxygen fluctuations), indicate that the purple urchin populations will not recover without an improvement in the water quality of Lough Hyne Marine Reserve, the restocking of urchins, and protection from poaching.
Persistent Identifierhttp://hdl.handle.net/10722/276032
ISSN
2023 Impact Factor: 2.6
2023 SCImago Journal Rankings: 0.760
ISI Accession Number ID

 

DC FieldValueLanguage
dc.contributor.authorTrowbridge, CD-
dc.contributor.authorLittle, C-
dc.contributor.authorPlowman, CQ-
dc.contributor.authorWilliams, GA-
dc.contributor.authorPilling, GM-
dc.contributor.authorMorritt, D-
dc.contributor.authorRivera Vázquez, Y-
dc.contributor.authorDlouhy-Masassengale, B-
dc.contributor.authorCottrell, DM-
dc.contributor.authorStirling, P-
dc.contributor.authorHarman, L-
dc.contributor.authorMcAllen, R-
dc.date.accessioned2019-09-10T02:54:33Z-
dc.date.available2019-09-10T02:54:33Z-
dc.date.issued2019-
dc.identifier.citationEstuarine, Coastal and Shelf Science, 2019, v. 226, article no. 106271-
dc.identifier.issn0272-7714-
dc.identifier.urihttp://hdl.handle.net/10722/276032-
dc.description.abstractTwo-decade-long monitoring studies at Europe's first statutory marine reserve—Lough Hyne in SW Ireland—indicate that benthic communities are rapidly changing. Populations of the ecologically important purple urchin (Paracentrotus lividus) have fluctuated widely, most recently with a population boom in the late 1990s, followed by a mass mortality that persists to the present day. Eight general hypotheses have been proposed to account for the urchin decline including cold temperature limiting reproduction, ephemeral algal exudates disrupting urchin fertilization, low larval availability (due to over-harvesting and/or episodic recruitment), high mortality of settlers and juveniles due to hypoxia, hyperoxia, or predation (a trophic cascade hypothesis), and increased mortality due to pathogens (stress hypothesis). The cold-temperature and the trophic cascade hypotheses appear unlikely. The remaining hypotheses, however, all seem to play a role, to some degree, in driving the urchin decline. Ulvoid exudates, for example, significantly reduced urchin fertilization and few larvae were found in plankton tows (2012–2015), indicating low larval availability in summer. Whilst settling urchins regularly recruited under shallow-subtidal rocks until 2011, no settlers were found in these habitats from 2011 to 2014 or in field experiments (2012–2018) using various settlement substrata. Seawater quality was poor in shallow areas of the lough with extreme oxygen fluctuations (diel-cycling hypoxia), and 1-day experimental exposures to DO values < 1 mg L−1 were lethal to most juvenile urchins. Multiple increases of the predatory spiny starfish (Marthasterias glacialis) population in recent decades may also have contributed to the demise of the coexisting juvenile urchins. Finally, urchins of all sizes were seen suffering from dropped spines, tissue necrosis, or white-coloured infection, suggestive of stress-related pathogen mortality. There was a paucity of broken tests, indicating limited predation by large crustaceans; the large number of adult urchins ‘missing’ and few P. lividus tests on the north shore points to possible urchin removal by poachers and/or starfish predation. While these ecological, environmental, and anthropogenic processes occur on open coast rocky shores, many are exacerbated by the semi-enclosed nature of this fully marine sea lough due to its limited flushing. Multiple factors, including low larval availability and rapidly expanding starfish populations, coupled with degraded habitat quality (ephemeral algal mats and extreme oxygen fluctuations), indicate that the purple urchin populations will not recover without an improvement in the water quality of Lough Hyne Marine Reserve, the restocking of urchins, and protection from poaching.-
dc.languageeng-
dc.publisherAcademic Press. The Journal's web site is located at http://www.elsevier.com/locate/ecss-
dc.relation.ispartofEstuarine, Coastal and Shelf Science-
dc.subjectParacentrotus lividus-
dc.subjectSea urchins-
dc.subjectMass mortality-
dc.subjectMarine reserve-
dc.subjectMarthasterias glacialis-
dc.subjectHypoxia-
dc.titleNo ‘silver bullet’: multiple factors control population dynamics of European purple sea urchins in Lough Hyne Marine Reserve, Ireland-
dc.typeArticle-
dc.identifier.emailWilliams, GA: hrsbwga@hkucc.hku.hk-
dc.identifier.authorityWilliams, GA=rp00804-
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1016/j.ecss.2019.106271-
dc.identifier.scopuseid_2-s2.0-85068376775-
dc.identifier.hkuros303180-
dc.identifier.volume226-
dc.identifier.spagearticle no. 106271-
dc.identifier.epagearticle no. 106271-
dc.identifier.isiWOS:000482495700032-
dc.publisher.placeUnited Kingdom-
dc.identifier.issnl0272-7714-

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