Science - USA (2021-10-29)

table S1). We compared these biogeographic
patterns on the basis of the similarity in as-
semblage proportions across stations (figs.
S7 and S6D and materials and methods).
Eukaryotic plankton groups vary along two
main axes reflecting the strength and the
nature of their biogeographic patterns (Fig. 2,
fig. S8, and materials and methods). The group
position on the first axis is tightly correlated to

short-distance spatial autocorrelation [Pearson

correlation coefficient (rP)=0.91atthesur-

face; fig. S9A] and anticorrelated to the Shannon

entropy of assemblage proportions (fig. S9, C

to F). Groups that score low on this axis are

thus characterized by many coexisting assem-

blages and strong local variation, or“patchi-

ness,”whereas those that score high have

clearer, more-structured biogeographic pat-

terns, which are characterized by a small

number of dominant assemblages and sim-

ilar composition in nearby communities. The

group position on the second axis is positively

correlated to the scale of biogeographic orga-

nization, which we measured as the character-

istic distance at which spatial autocorrelation

vanishes (rP= 0.54,P= 10−^6 at the surface)

(fig. S10A) and which ranges from ~7000 to

SCIENCEscience.org 29 OCTOBER 2021•VOL 374 ISSUE 6567 595

Parasites

Phagotrophs

Assemblages

at the surface

Dissim. in OTU composition Group contribution to assemblage

Diplonemida

Arthropoda

Chordata

Cnidaria

Chaetognatha

Mamiellophyc.

Collodaria

Acantharea

Spumellaria

Cryomonadida

Dinophyceae

MALV I

MALV II

Ciliophora

Apicomplexa

Bacillariophyta

MAST 3,12

MAST 4,6– 11

Haptophyta

Others

0.95 0.90 0.85 0.80 0.75

26°

22°

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

High Lat.

Low Lat.

Intermediate Lat.

33°

38°

36°

24°

14°

9°

6°

19°

20°

28°

73°

70°

58°

58°

Assemblages

Groups

Assemblages

A

B

Phagotrophs

Metazoans

Phototrophs

Phagotrophs

Mixotrophs

Mixotrophs

Parasites

Phagotrophs

Phototrophs

Phototrophs

Ecology

Fig. 1. Global surface biogeography of all eukaryotic plankton OTUs.
(AandB) Biogeography is characterized by 16 assemblages of co-occurring
OTUs that are identified by color [in (A) and left side of (B)] and a number from
1 to 16 [in (B)]. Shown in (A) are the relative contributions of assemblages to surface
plankton communities, which are represented as pies on the map and as stacked
bars ordered by latitude on the left-hand side. Most communities are dominated
by one of three assemblages: parasite-rich assemblage 1 (dark red), which is globally
ubiquitous except in the Arctic, and high-latitude, diatom-rich assemblages 13
and 15 (cyan and marine blue), with the transition occurring around the shift
between cold and warm waters in the North and South Atlantic (subtropical
fronts, at about 45°). Shown on the left in (B) is a dendrogram of assemblage

dissimilarity with respect to their OTU composition (Simpson dissimilarity), where

the mean absolute latitude of each assemblage is indicated. Assemblages form three

main clusters that correspond to high, intermediate, and low latitudes (with

approximate boundaries at 45° and 20°), although three assemblages (10, 11, and

12) cluster apart. Shown in the box on the right is the contribution of the 19 major

eukaryotic groups tallying more than 1000 OTUs to assemblages, grouped by

phylogenetic relatedness. The dominant ecological function is indicated for each

group. Assemblages 11 and 12 capture outlier stations, which are, respectively,

Chordata enriched (likely linked to tunicate blooms) and Diplonemida enriched (likely

linked to deep water influxes). See supplementary text S1 for more detail. MALV,

marine alveolates; MAST, marine stramenopiles.

RESEARCH | REPORTS