title: The calcareous brown algaPadina pavonicain southern Britain: population change and tenacity over 300 years.
abstract: Understanding long-term persistence and variability in species populations can help to predict future survival, growth and distribution; however, sustained observations are exceedingly rare. We examine and interpret a remarkable record of the calcareous brown algaPadina pavonica(Phaeophyceae) at its northern limit on the south coast of England (50°N, 1-3°W) from 1680 to 2014, which is probably the longest compilation and review of any marine algal species. Over this period, which extends from the middle of the Little Ice Age to the present, there has been considerable variability in temperature and storminess. We identified a significant number of site extinctions in the second half of the nineteenth century, which coincided with cooler conditions and stormier weather. To interpret these changes, we measured recruitment, growth and production of tetraspores at sheltered and exposed sites in 2012-2014, years which had low and high spring temperatures. Potential spore production was greater at the sheltered site due to a longer growing period and survival of larger fronds. Delayed growth in the cooler spring resulted in smaller fronds and lower potential production of tetraspores by early summer. Yet in the warmer year, rapid initial growth caused higher sensitivity to damage and dislodgement by summer storms, which also limited potential spore production. Antagonistic responses to multiple stressors and disturbances make future predictions of survival and distribution difficult. Fronds ofPadinapavonicaare sensitive to both temperature and physical disturbances, yet vegetative perennation appears to have enabled population persistence and explained the longevity of remaining populations.
authors.affiliation: Faculty of Science and Technology, Department of Life and Environmental Sciences, Bournemouth University, Talbot Campus, Fern Barrow, Poole, Dorset BH12 5BB UK.
authors.forename: Roger J H
authors.initials: RJ
authors.lastname: Herbert
authors.affiliation: Faculty of Science and Technology, Department of Life and Environmental Sciences, Bournemouth University, Talbot Campus, Fern Barrow, Poole, Dorset BH12 5BB UK.
authors.forename: Lisha
authors.initials: L
authors.lastname: Ma
authors.affiliation: Isle of Wight Local Records Centre, Seaclose Offices, Fairlee Road, Newport, Isle of Wight PO30 2QS UK.
authors.forename: Anne
authors.initials: A
authors.lastname: Marston
authors.affiliation: Institute of Marine Sciences, School of Biological Sciences, Portsmouth University, Ferry Road, Eastney, Portsmouth, PO1 2DY UK.
authors.forename: William F
authors.initials: WF
authors.lastname: Farnham
authors.affiliation: The Natural History Museum, Cromwell Road, London, SW7 5BD UK.
authors.forename: Ian
authors.initials: I
authors.lastname: Tittley
authors.affiliation: Climatic Research Unit, School of Environmental Sciences, University of East Anglia, Norwich, UK.
authors.forename: Richard C
authors.initials: RC
authors.lastname: Cornes