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

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dc.contributor.authorTrowbridge, Cynthia D.
dc.contributor.authorLittle, Colin
dc.contributor.authorPlowman, Caitlin Q.
dc.contributor.authorWilliams, G. A.
dc.contributor.authorPilling, G. M.
dc.contributor.authorMorritt, D.
dc.contributor.authorRivera Vázquez, Y.
dc.contributor.authorDlouhy-Massengale, B.
dc.contributor.authorCottrell, Dylan M.
dc.contributor.authorStirling, Penny
dc.contributor.authorHarman, Luke
dc.contributor.authorMcAllen, Rob
dc.contributor.funderNational Parks and Wildlife Serviceen
dc.contributor.funderNational Science Foundationen
dc.date.accessioned2019-08-30T14:49:19Z
dc.date.available2019-08-30T14:49:19Z
dc.date.issued2019-06-25
dc.date.updated2019-08-30T14:37:11Z
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.en
dc.description.sponsorshipNational Parks and Wildlife Service of Ireland and the U.S. National Science Foundation (under Grant No. 0211186 and 1130978-OISE)en
dc.description.statusPeer revieweden
dc.description.versionAccepted Versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.articleid106271en
dc.identifier.citationTrowbridge, C. D., Little, C., Plowman, C. Q., Williams, G. A., Pilling, G. M., Morritt, D., Rivera Vázquez, Y., Dlouhy-Massengale, B., Cottrell, D. M., Stirling, P., Harman, L. and McAllen, R. (2019) 'No ‘silver bullet’: Multiple factors control population dynamics of European purple sea urchins in Lough Hyne Marine Reserve, Ireland', Estuarine, Coastal and Shelf Science, 226, 106271 (20 pp). doi: 10.1016/j.ecss.2019.106271en
dc.identifier.doi10.1016/j.ecss.2019.106271en
dc.identifier.eissn1096-0015
dc.identifier.endpage20en
dc.identifier.issn0272-7714,
dc.identifier.journaltitleEstuarine and Coastal Shelf Scienceen
dc.identifier.startpage1en
dc.identifier.urihttps://hdl.handle.net/10468/8424
dc.identifier.volume226en
dc.language.isoenen
dc.publisherElsevieren
dc.relation.urihttp://www.sciencedirect.com/science/article/pii/S0272771419300769
dc.rights© 2019, Elsevier Ltd. All rights reserved. This manuscript version is made available under the CC BY-NC-ND 4.0 licence.en
dc.rights.urihttps://creativecommons.org/licenses/by-nc-nd/4.0/en
dc.subjectParacentrotus lividusen
dc.subjectSea urchinsen
dc.subjectMass mortalityen
dc.subjectMarine reserveen
dc.subjectMarthasterias glacialisen
dc.subjectHypoxiaen
dc.titleNo ‘silver bullet’: multiple factors control population dynamics of European purple sea urchins in Lough Hyne Marine Reserve, Irelanden
dc.typeArticle (peer-reviewed)en
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