Supporting Online Material for

Transcription

1 Supporting Online Material for Coherent Sign Switching in Multiyear Trends of Microbial Plankton William K. W. Li,* W. Glen Harrison, Erica J. H. Head *To whom correspondence should be addressed. Published 24 February 2006, Science 311, 1157 (2006) DOI: /science This PDF file includes: Materials and Methods Figs. S1 to S3 Table S1 References

2 S2 Materials and Methods Analytical methods Seawater samples were collected by Niskin bottles mounted on a CTD rosette. At most stations, 11 depths were sampled starting at the sea surface, thence every 10 m thereafter down to 100 m (S1). Chlorophyll a was measured in acetone extracts of particulate matter collected on Whatman GFF filters using a Turner Designs fluorometer (S2). Bacterioplankton were fixed in 1% paraformaldehyde, quick frozen in liquid nitrogen, and stored at -80 o C. Thawed samples were stained with SYBR-Green 1 and counted by flow cytometry (S3). At station HL2, microphytoplankton (diatoms and dinoflagellates) were fixed in acid Lugol s solution, settled in Utermöhl chambers and enumerated by phase contrast microscopy (S2). Remote sensing Semi-monthly composite images of surface chlorophyll for the entire northwest Atlantic (39 o o north latitude, 42 o -71 o west longitude) are produced at the Bedford Institute of Oceanography from the Sea-viewing Wide Field-of-view (SeaWiFS) satellite sensor. Image products are freely available ( Chlorophyll estimates are extracted from the composites for selected sub-regions and fixed stations using a box (ca 5x5 km) centered on the station location. Statistical analysis Areal standing stocks of chlorophyll (mg m -2 ) and bacterioplankton abundance (cells m -2 ) were computed from discrete depth measurements using trapezoid integration. Both variables have lognormal distributions (15). Analysis of covariance and linear regression were performed on log areal standing stocks versus year using BIOMstat version 3.3 (Exeter Software, New York, 1999). References S1. W.K.W. Li, W.G. Harrison, Deep-Sea Res. II 48,2271 (2001) S2. M.R. Mitchell et al., Can. Tech. Rep. Hydrogr. Ocean Sci. 223, 1 (2002) S3. W.K.W. Li, P.M. Dickie, Cytometry 44, 236 (2001)

3 S3 Figure S1. Station map of the northwest Atlantic Ocean. 65 Greenland 60 Labrador Sea Latitude (North) Labrador 45 Scotian Shelf Longitude (West) WSS (Western Scotian Shelf): Browns Bank Line stations 1-7 CSS (Central Scotian Shelf): Halifax Line stations 1-7 ESS (Eastern Scotian Shelf): Louisbourg Line stations 1-7 LS (Labrador Shelf): WOCE AR7W stations 1-10 LB (Labrador Basin): WOCE AR7W stations GS (Greenland Shelf): WOCE AR7W stations 24-28

4 S4 Figure S2. Historical and recent spring phytoplankton indexes of the Scotian Shelf extracted from Bedford Institute of Oceanography archives. (A) Surface (<10 m) chlorophyll concentration. (B) Green colour index from Continuous Plankton Recorder. Box-and-whiskers plots indicate 10, 25, 50, 75 and 90 percentiles; dotted lines indicate mean values. A log Surface chlorophyll (mg m -3 ) Spring period B 0.8 Phytoplankton colour index Spring period

5 S5 Figure S3. Relationship between areal chlorophyll concentration and water column stratification. Stratification index is the difference in density (kg m -3 ) between seawater at depth (100 m) and near the surface (5-10 m) divided by the depth difference (m). Code for symbols as in Fig log Chlorophyll (mg m -2 ) Stratification index (kg m -4 )

6 S6 Table S1. Statistical analysis of multiyear change in biological variables on the Scotian Shelf and Labrador Sea. ANCOVA ANCOVA LINEAR REGRESSION Differences among adjusted means Differences among slopes Location Season X Y Fs p Fs p Fs p n Slope SE of Slope % change per year CSS Spring Year log CHL CSS Spring Year log BACTERIA CSS Spring Year log SeaWiFS CHL CSS HL2 Spring Year log CHL CSS HL2 Spring Year log DIATOM CSS HL2 Spring Year log DINOFLAG CSS Fall Year log CHL CSS Fall Year log BACTERIA CSS Fall Year log SeaWiFS CHL CSS HL2 Fall Year log CHL CSS HL2 Fall Year log DIATOM CSS HL2 Fall Year log DINOFLAG ESS Spring Year log CHL ESS Spring Year log BACTERIA ESS Spring Year log SeaWiFS CHL ESS Fall Year log CHL ESS Fall Year log BACTERIA ESS Fall Year log SeaWiFS CHL WSS Spring Year log CHL WSS Spring Year log BACTERIA WSS Spring Year log SeaWiFS CHL WSS Fall Year log CHL WSS Fall Year log BACTERIA WSS Fall Year log SeaWiFS CHL LS Spring Year log CHL LS Spring Year log BACTERIA LS Spring Year log SeaWiFS CHL LB Spring Year log CHL LB Spring Year log BACTERIA LB Spring Year log SeaWiFS CHL GS Spring Year log CHL GS Spring Year log BACTERIA GS Spring Year log SeaWiFS CHL