title: The annual cycles of phytoplankton biomass.
abstract: Terrestrial plants are powerful climate sentinels because their annual cycles of growth, reproduction and senescence are finely tuned to the annual climate cycle having a period of one year. Consistency in the seasonal phasing of terrestrial plant activity provides a relatively low-noise background from which phenological shifts can be detected and attributed to climate change. Here, we ask whether phytoplankton biomass also fluctuates over a consistent annual cycle in lake, estuarine-coastal and ocean ecosystems and whether there is a characteristic phenology of phytoplankton as a consistent phase and amplitude of variability. We compiled 125 time series of phytoplankton biomass (chlorophyll a concentration) from temperate and subtropical zones and used wavelet analysis to extract their dominant periods of variability and the recurrence strength at those periods. Fewer than half (48%) of the series had a dominant 12-month period of variability, commonly expressed as the canonical spring-bloom pattern. About 20 per cent had a dominant six-month period of variability, commonly expressed as the spring and autumn or winter and summer blooms of temperate lakes and oceans. These annual patterns varied in recurrence strength across sites, and did not persist over the full series duration at some sites. About a third of the series had no component of variability at either the six- or 12-month period, reflecting a series of irregular pulses of biomass. These findings show that there is high variability of annual phytoplankton cycles across ecosystems, and that climate-driven annual cycles can be obscured by other drivers of population variability, including human disturbance, aperiodic weather events and strong trophic coupling between phytoplankton and their consumers. Regulation of phytoplankton biomass by multiple processes operating at multiple time scales adds complexity to the challenge of detecting climate-driven trends in aquatic ecosystems where the noise to signal ratio is high.
authors.affiliation: John Muir Institute of the Environment, Tahoe Environmental Research Center, University of California, One Shields Avenue, Davis, CA 95616, USA. mwinder@ucdavis.edu
authors.forename: Monika
authors.initials: M
authors.lastname: Winder
authors.forename: James E
authors.initials: JE
authors.lastname: Cloern
mesh_terms: D001267:Atlantic Ocean; D018533:Biomass; D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D057231:Climate Change; D017753:Ecosystem; D010839:Phytoplankton / Q000254:growth & development*; D012621:Seasons; D058067:Wavelet Analysis
chemical_list: D002734:Chlorophyll; D000077194:Chlorophyll A
references.citation: Philos Trans R Soc Lond B Biol Sci. 2010 Oct 12;365(1555):3247-60
references.pmid: 20819816
references.citation: Ecol Lett. 2008 Dec;11(12):1294-303
references.pmid: 18793308
references.citation: Proc Natl Acad Sci U S A. 2008 Dec 9;105(49):19108-13
references.pmid: 19060207
references.citation: Science. 2005 Jun 10;308(5728):1621-3
references.pmid: 15947186
references.citation: Oecologia. 1993 Mar;93(2):276-284
references.pmid: 28313618
references.citation: Nature. 2003 May 22;423(6938):398-9
references.pmid: 12761538
references.citation: Nature. 2004 Aug 19;430(7002):881-4
references.pmid: 15318219
references.citation: Proc Biol Sci. 2002 Feb 22;269(1489):391-5
references.pmid: 11886627
references.citation: Science. 1990 Nov 16;250(4983):967-70
references.pmid: 17746921
references.citation: Int J Remote Sens. 2009 Jul;30(13-14):3291-3314
references.pmid: 25937680
references.citation: Science. 2008 Apr 4;320(5872):57-8
references.pmid: 18388279
references.citation: Nature. 2006 Dec 7;444(7120):752-5
references.pmid: 17151666
references.citation: Ecol Lett. 2007 Nov;10(11):1066-74
references.pmid: 17727665
references.citation: Proc Biol Sci. 2005 May 7;272(1566):887-95
references.pmid: 16024342
references.citation: Trends Ecol Evol. 2005 Jun;20(6):337-44
references.pmid: 16701390
references.citation: Proc Natl Acad Sci U S A. 2009 Jan 6;106(1):197-202
references.pmid: 19109431
references.citation: Proc Natl Acad Sci U S A. 2007 Nov 20;104(47):18561-5
references.pmid: 18000053
references.citation: Science. 1998 Jul 10;281(5374):237-40
references.pmid: 9657713
references.citation: Nature. 2008 Feb 14;451(7180):822-5
references.pmid: 18273017
references.citation: Proc Biol Sci. 2009 Aug 22;276(1669):2871-80
references.pmid: 19474038
references.citation: Trends Ecol Evol. 2007 Jul;22(7):357-65
references.pmid: 17478009
references.citation: Ecology. 2006 Nov;87(11):2895-904
references.pmid: 17168033
references.citation: Philos Trans R Soc Lond B Biol Sci. 2010 Oct 12;365(1555):3227-46
references.pmid: 20819815
references.citation: Science. 2001 Oct 26;294(5543):793-5
references.pmid: 11679652
references.citation: Oecologia. 1979 Dec;44(1):1-7
references.pmid: 28310454