title: Projecting effects of climate change on marine systems: is the mean all that matters?
abstract: Studies dealing with the effects of changing global temperatures on living organisms typically concentrate on annual mean temperatures. This, however, might not be the best approach in temperate systems with large seasonality where the mean annual temperature is actually not experienced very frequently. The mean annual temperature across a 50-year, daily time series of measurements at Helgoland Roads (54.2° N, 7.9° E) is 10.1°C while seasonal data are characterized by a clear, bimodal distribution; temperatures are around 6°C in winter and 15°C in summer with rapid transitions in spring and autumn. Across those 50 years, the temperature at which growth is maximal for each single bloom event for 115 phytoplankton species (more than 6000 estimates of optimal temperature) mirrors the bimodal distribution of the in situ temperatures. Moreover, independent laboratory data on temperature optima for growth of North Sea organisms yielded similar results: a deviance from the normal distribution, with a gap close to the mean annual temperature, and more optima either above or below this temperature. We conclude that organisms, particularly those that are short-lived, are either adapted to the prevailing winter or summer temperatures in temperate areas and that few species exist with thermal optima within the periods characterized by rapid spring warming and autumn cooling.
authors.affiliation: Biologische Anstalt Helgoland, Alfred-Wegener-Institut, Helmholtz Zentrum für Polar- und Meeresforschung, Postfach 180, Helgoland 27483, Germany University of Bremen, Bremen, Germany maarten.boersma@awi.de.
authors.forename: Maarten
authors.initials: M
authors.lastname: Boersma
authors.affiliation: Institute of Virology, University Hospital Essen, University of Duisburg-Essen, Hufelandstrasse, Essen 45122, Germany.
authors.forename: Nico
authors.initials: N
authors.lastname: Grüner
authors.affiliation: Biologische Anstalt Helgoland, Alfred-Wegener-Institut, Helmholtz Zentrum für Polar- und Meeresforschung, Postfach 180, Helgoland 27483, Germany.
authors.forename: Natália
authors.initials: N
authors.lastname: Tasso Signorelli
authors.affiliation: Biologische Anstalt Helgoland, Alfred-Wegener-Institut, Helmholtz Zentrum für Polar- und Meeresforschung, Postfach 180, Helgoland 27483, Germany.
authors.forename: Pedro E
authors.initials: PE
authors.lastname: Montoro González
authors.affiliation: Institute for Hydrobiology and Fisheries Science, University of Hamburg, Olbersweg 24, Hamburg 22767, Germany.
authors.forename: Myron A
authors.identifier: http://orcid.org/0000-0001-7423-1854
authors.initials: MA
authors.lastname: Peck
authors.affiliation: Biologische Anstalt Helgoland, Alfred-Wegener-Institut, Helmholtz Zentrum für Polar- und Meeresforschung, Postfach 180, Helgoland 27483, Germany School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, Bremen 28759, Germany.
authors.forename: Karen H
authors.initials: KH
authors.lastname: Wiltshire
mesh_terms: D000818:Animals; D057231:Climate Change; D017753:Ecosystem; D008954:Models, Biological; D009792:Oceans and Seas; D010507:Periodicity; D012621:Seasons; D013696:Temperature
keywords: Helgoland Roads; North Sea; climate; distribution; global change; temperature optimum