Electronic Supplementary Material: S.D. Ling et al. Global regime shift dynamics of catastrophic sea urchin overgrazing

Table S1. Summary of correlative databetween percent ‘landscape’ cover (%) of macroalgal canopy formers and sea urchin biomass (grams. m-2) for 13 regions worldwide. Where required, conversion of macroalgal abundance to % Cover was based only on large canopy-forming adults where data sets split abundance or biomass estimates by life-history stages. For sea urchins, biomass (grams wet weight) was calculated using allometric conversion of TD (Test Diameter in mm) to biomass where individual sea urchin test diameters were recorded; else an average individual biomass of sea urchins was estimated for particular regions.

Macroalgal canopy cover / Sea urchin abundance
# / Hemisphere / Region / Sites / Spatial extent (km) / n / Year sampled / Dominant genera / Quadrat scale (m) / % Cover / conversion / Dominant genera / Quadrat
scale (m) / Biomass (B, grams)
1 / Southern / Australia -Tas/NSW / 164 / 1,500 / 5,264 / 2001-2008 / Ecklonia / 5x1 / Direct measure / Centrostephanus / 5x1 / B=0.0106(TD)2.2319
2 / Southern / Australia – Tas/Vic / 37 / 500 / 628 / 2001-2013 / Ecklonia / 5x1 / Direct measure / Heliocidaris / 5x1 / B=0.0014(TD)2.668
3 / Southern / New Zealand / 165 / 2,000 / 642 / 1999-2003 / Ecklonia / 1x1 / % Cover=8.92ln(biomass) +2.29 / Evechinus / 1x1 / B=0.000843(TD)2.8288
4 / Southern / Chile / 4 / 400 / 511 / 2012 / Lessonia / 1x1 / Morphometric scaling:
Lessonia canopy area =
pi*(3.5*individ. holdfast radius)2 / Tetrapygus / 1x1 / B= 298g. individ.-1
[Individual holdfast diameter measured in situ]
5 / Southern / South Africa / 6 / 100 / 162 / 1988/89,2001/05-06 / Ecklonia/ Laminaria / 1x1 / % Cover= 0.1432(biomass) + 5.518 / Parechinus / 1x1 / B= 27.5g.Individ.-1
6 / Northern / Nova Scotia / 2 / 100 / 115 / 1992-1993 / Sacharrina/ Laminaria / 1x1 / Direct measure / Strongylocentrotus / 1x1 / Direct measure
7 / Northern / Gulf of St.Lawrence / 18 / 100 / 157 / 2011 / Sacharrina/ Laminaria / 0.5x0.5 / Direct measure / Strongylocentrotus / 0.5x0.5 / B = 0.0007(TD)2.8539
8 / Northern / Norway / 51 / 1,000 / 1,025 / 2007-2012 / Sacharrina/ Laminaria / 0.5x0.5 / Direct measure / Strongylocentrotus / 0.5x0.5 / B= 0.0007(TD)2.8539
9 / Northern / Canary Islands / 125 / 500 / 800 / 2001-2004 / Lobophora/ Cystoseira / 0.5x0.5 / Direct measure / Diadema / 5 x 4 / B=0.0008(TD)2.8941
10 / Northern / California / 11 / 250 / 581 / 2001-2012 (annually) / Macrocysits / 20x2 / %Cover to Stipe Count (SC): / Strongylocentrotus / 3x1 / B=0.0499(TD) + 0.0019
Laminaria / Macrocystis; %Cover=3.77*SC
Pterygophora / Eisenia; %Cover=8.98*SC
Eisenia / Pterygophora; %Cover=2.23*SC
Laminaria; %Cover=0.89*SC
11 / Northern / British Columbia / 8 / 250 / 161 / 2012 / Nereocystis/ / 1x1 / Morphometric scaling: / Strongylocentrotus / 1 x 1 / S.franciscanus:
B=0.0005*(TD)2.9572;
Laminaria / Genus %Cover of 1m2/individ.
Nereocystis 100 / S. purpuratusB=0.0005*(TD)2.9598
Cymathere 25
Costeria 21
Alaria 20
Laminaria 16
Saccharina 15
Pterygophora 7
Eisenia 2
12 / Northern / Mediterranean / 6 / 2 / 278 / 1999 / Cystoseira / 1x1 / Direct measure / Paracentrotus / 1 x 1 / B=0.00319(TD)2.479
13 / Northern / Japan / 1 / 1 / 320 / 2013 / Eisenia/ Saccharina / 1x1 / Direct measure / Strongylocentrotus / 1 x 1 / B= 79g.individ.-1
/ Undaria

1

Electronic Supplementary Material: S.D. Ling et al. Global regime shift dynamics of catastrophic sea urchin overgrazing

Table S2. Summary of observational and manipulative experiments detailing the magnitude and directional response of macroalgal habitat (both forward and reverse regime shifts) following change in sea urchin abundance. Studies were included if stated magnitudes in themacroalgalresponse and sea urchin abundance could be standardized as percentage cover (%) for macroalgaeand biomass(grams. m-2) for sea urchins respectively. Experiments involved sudden changes in urchin biomass density between “Start” & “End”: experimenters either reduced or increased urchins to a target density; or in the case of observational studies, either disease (reverse shifts) or local aggregation (forward shifts) also caused sudden change in urchin density. But see exception (study #43) in footnote below.

# / Hemisphere / Region / Experiment / Regimeshift
direction / Urchin biomass
Start (g.m-2) / Urchin biomass
End (g.m-2) / Urchin density end
(individ. m-2) / % Cover canopy macroalgae start / % Cover canopy macroalgae end / % Cover canopy macroalgae loss/gain / Duration of response (months) / Source
1 / Northern / New England / Observational / Fwd / 0 / 12,228 / 280 / 100 / 0 / 100 / 3 / Witman, 1985
2 / Southern / Australia / Manipulation / Fwd / 0 / 7,767 / 90 / 55 / 7 / 48 / 7 / Wright et al 2005
3 / Southern / Australia / Manipulation / Fwd / 932 / 6,136 / 80 / 60 / 0 / 60 / 4 / Wright et al 2005
4 / Northern / British Columbia / Observational / Fwd / 5,770 / 5,770 / 322 / 39 / 1 / 38 / 11 / Foreman 1977
5 / Southern / Australia / Manipulation / Fwd / 0 / 3,107 / 40 / 68 / 37 / 30 / 7 / Wright et al 2005
6 / Southern / Australia / Manipulation / Fwd / 0 / 2,535 / 10 / 95 / 20 / 75 / 5 / Hill et al 2003
7 / Northern / California / Observational / Fwd / 1,246 / 1,246 / 7 / 38 / 8 / 30 / 3 / Dean et al 1984
8 / Southern / Australia / Manipulation / Fwd / 1,162 / 1,162 / 4 / 71 / 12 / 58 / 6 / Strain & Johnson 2009
9 / Southern / Australia / Manipulation / Fwd / 0 / 1,014 / 4 / 95 / 70 / 25 / 5 / Hill et al 2003
10 / Northern / Nova Scotia / Manipulation / Fwd / 0 / 883 / 34 / 98 / 0 / 98 / 3 / Johnson & Mann 1990
11 / Northern / Nova Scotia / Observational / Fwd / 691 / 691 / 120 / 20 / 0 / 20 / 24 / Miller 1985
12 / Northern / Nova Scotia / Observational / Fwd / 667 / 667 / 93 / 84 / 0 / 83 / 1 / Scheilbling et al 1999
13 / Southern / Australia / Manipulation / Fwd / 581 / 581 / 2 / 71 / 23 / 47 / 6 / Strain & Johnson 2009
14 / Southern / Australia / Manipulation / Fwd / 0 / 507 / 2 / 95 / 70 / 25 / 5 / Hill et al 2003
15 / Northern / Nova Scotia / Observational / Fwd / 233 / 233 / 32 / 79 / 0 / 78 / 3 / Scheilbling et al 1999
16 / Northern / Canary Islands / Manipulation / Fwd / 27 / 210 / 7 / 54 / 12 / 42 / 6 / Hernández et al. unpub. data
17 / Northern / Canary Islands / Manipulation / Fwd / 9 / 150 / 8 / 85 / 0 / 85 / 9 / Hernández et al. unpub. data
18 / Northern / Nova Scotia / Manipulation / Rev / 804 / 0 / 0 / 0 / 59 / 59 / 4 / Johnson & Mann 1990
19 / Northern / Alaska / Manipulation / Rev / 3,506 / 0 / 0 / 0 / 100 / 100 / 12 / Duggins 1980
20 / Southern / Australia / Manipulation / Rev / 464 / 0 / 0 / 0 / 100 / 100 / 6 / Kriegisch et al. unpub. data
21 / Southern / New Zealand / Manipulation / Rev / 2,261 / 0 / 0 / 0 / 12 / 12 / 10 / Shears & Babcock 2002
22 / Southern / Australia / Manipulation / Rev / 1,057 / 0 / 0 / 0 / 93 / 93 / 18 / Ling 2008
23 / Southern / Australia / Manipulation / Rev / 559 / 0 / 0 / 0 / 78 / 77 / 18 / Ling 2008
24 / Southern / Australia / Manipulation / Rev / 401 / 0 / 0 / 0 / 37 / 37 / 18 / Ling 2008
25 / Southern / Australia / Manipulation / Rev / 757 / 0 / 0 / 0 / 92 / 92 / 18 / Ling unpub. 2008-2011
26 / Southern / Australia / Manipulation / Rev / 456 / 0 / 0 / 0 / 91 / 91 / 18 / Ling unpub. 2008-2011
27 / Southern / Australia / Manipulation / Rev / 2,535 / 0 / 0 / 0 / 48 / 48 / 18 / Andrew & Underwood 1993
28 / Southern / Australia / Manipulation / Rev / 1,521 / 0 / 0 / 0 / 30 / 30 / 18 / Andrew et al 1998
29 / Southern / Australia / Manipulation / Rev / 1,014 / 0 / 0 / 0 / 28 / 28 / 5 / Hill et al 2003
30 / Southern / New Zealand / Manipulation / Rev / 912 / 0 / 0 / 0 / 28 / 27 / 18 / Andrew & Choat 1982
31 / Southern / New Zealand / Manipulation / Rev / 912 / 0 / 0 / 0 / 42 / 42 / 18 / Andrew & Choat 1982
32 / Northern / British Columbia / Observational / Rev / 2,900 / 0 / 0 / 0 / 100 / 100 / 72 / Watson & Estes 2011
33 / Northern / British Columbia / Observational / Rev / 4,579 / 0 / 0 / 0 / 100 / 100 / 12 / Watson & Estes 2011
34 / Southern / Australia / Observational / Rev / 2,317 / 0 / 0 / 0 / 88 / 88 / 20 / Andrew 1991
35 / Northern / New England / Manipulation / Rev / 4,673 / 0 / 0 / 0 / 100 / 100 / 25 / Witman 1987
36 / Northern / Nova Scotia / Observational / Rev / 1208 / 0 / 0 / 0 / 100 / 100 / 36 / Scheibling, 1986
37 / Southern / Australia / Manipulation / Rev / 191 / 0 / 0 / 0 / 52 / 52 / 13 / Strain & Johnson 2013
38 / Northern / Nova Scotia / Observational / Rev / 480 / 5 / 0.5 / 0 / 100 / 100 / 33 / Miller & Colodey 1983
39 / Northern / British Columbia / Observational / Rev / 2,198 / 15 / 0.1 / 0.3 / 100 / 100 / 12 / Watson & Estes 2011
40 / Northern / Nova Scotia / Observational / Rev / 201 / 18 / 15 / 0 / 25 / 25 / 21 / Miller 1985
41 / Northern / California / Manipulation / Rev / 1,254 / 25 / 0.1 / 0 / 22 / 22 / 8 / Cowen et al 1982
42 / Northern / Newfoundland / Manipulation / Rev / 413 / 41 / 3 / 0 / 9 / 9 / 10 / Keats et al 1990
43 / Southern / New Zealand / Manipulation / Rev / 635 / 70 / 0.5 / 2 / 50 / 48 / 300* / Shears & Babcock 2003
44 / Northern / British Columbia / Observational / Rev / 2,314 / 76 / 0.3 / 0 / 100 / 100 / 24 / Watson & Estes 2011
45 / Southern / Australia / Manipulation / Rev / 581 / 79 / 0.5 / 0 / 25 / 25 / 12 / Ling et al 2010
46 / Northern / California / Observational / Rev / 623 / 89 / 0.5 / 0 / 100 / 100 / 12 / Pearse & Hines 1979
47 / Northern / Nova Scotia / Manipulation / Rev / 2,200 / 102 / 13 / 0 / 26 / 26 / 23 / Himmelman et al 1983
48 / Northern / Nova Scotia / Observational / Rev / 128 / 128 / 24 / 0 / 90 / 90 / 19 / Schielbling et al 1999
49 / Southern / Australia / Manipulation / Rev / 1,521 / 254 / 1 / 0 / 30 / 30 / 18 / Andrew et al 1998
50 / Northern / Norway / Manipulation / Rev / 1,388 / 324 / 6 / 0 / 95 / 95 / 36 / Leinass & Christie 1996
51 / Northern / Canary Islands / Manipulation / Rev / 112 / 0 / 0 / 17 / 46 / 29 / 12 / Ortega-Borges et al 2009
52 / Northern / Mediterranean / Manipulation / Rev / 208 / 5 / 0.2 / 0 / 41 / 41 / 16 / Bendetti-cecchi et al 1998
53 / Northern / Mediterranean / Manipulation / Rev / 231 / 5 / 0.2 / 2 / 54 / 52 / 18 / Bulleri et al 1999
54 / Northern / Canary Islands / Manipulation / Rev / 185 / 12 / 0.5 / 0 / 54 / 54 / 6 / Hernández et al. unpub. data
55 / Northern / Mediterranean / Manipulation / Rev / 336 / 19 / 1 / 0 / 70 / 70 / 48 / Hereu 2004
56 / Northern / Canary Islands / Manipulation / Rev / 170 / 20 / 1 / 0 / 85 / 85 / 10 / Hernández et al. unpub. data
57 / Northern / Canary Islands / Manipulation / Rev / 150 / 57 / 2 / 0 / 54 / 54 / 6 / Hernández et al. unpub. data

*Note that for purposes of calculating an average time for macroalgae recovery once urchin abundance falls below the critical reverse-shift threshold, the long-term recovery of macroalgae observed inside the Leigh Marine Reserve over 25 years (300 months) was excluded given the long lag times involved in the re-establishment of functional urchin predators and ultimately reduction in urchin abundance (Shears & Babcock 2003).

Fig. S1. Example images of alternative macroalgal bed and grazed sea urchin barren states of rocky reef systems worldwide. Red arrows indicate the forward-shift caused by sea urchin overgrazing from macroalgal dominated to urchin dominated barrens; blue arrows indicate the reverse-shift from urchin barrens back to macroalgal habitat once grazing pressure is alleviated. Dominant macroalgal and barrens-forming sea urchin species are listed respectively - photographic credits are given in square brackets: Northern Hemisphere systems, a.) Nova Scotia (SaccharinalatissimaStrogylocentrotusdroebachiensis[by Scott Ling]), b.) British Columbia(NereocystisluetkeanaS. franciscanus[by Mark Wunsch], c.) California (Pterygophoracalifornica [by Alejandro Perez-Matus] & S. franciscanus plus S. purpuratus [by Scott Ling], d) Japan (Saccharina japonicaS. nudus [by Daisuke Fujita]), e) Mediterranean (CystoseirabalearicaParacentrotuslividus [by BernatHereu]), f) Canary Islands (LobophoravariegataDiademaafricanum [by Scott Ling]); Southern Hemisphere systems, g) Australia (EckloniaradiataHeliocidariserythrogramma [by Scott Ling] - for images of Australian urchin barrens formed by Centrostephanusrodgersii - see Ling & Johnson 2012; Ling 2013), h) New Zealand (E.radiataEvechinuschloriticus [by Nick Shears], i) Chile (LessoniatrabeculataTetrapygusniger [by Alejandro Perez-Matus]), j) South Africa, Ecklonia maxima and Laminariapallida [by Rob Tarr] & Parechinusangulosus [by Rob Tarr]).

Fig. S2.Map showing the 13 globally representative temperate rocky reef systems known to occur as algal bed or urchin barrens states (temperate zones encapsulated by dotted lines within each hemisphere; equator is shown as dash-dot line). Ordered west to east from Northern to Southern Hemispheres, the representative reef systems covered 11 regions: 1. British Columbia (Gulf of Alaska, NE Pacific); 2.California (NE Pacific); 3.Nova Scotia (NW Atlantic); 4.Gulf of St. Lawrence (NW Atlantic); 5.Canary Is. (NE Atlantic); 6.Norway (Norwegian Sea, NE Atlantic); 7.Mediterranean (Mediterranean Sea, NE Atlantic); 8. Japan (NW Pacific); 9.Chile (SE Pacific); 10.South Africa (W Indian); 11.Victoria (SE Australia, SW Pacific); 12.Tasmania (SE Australia, SW Pacific); 13. New Zealand (SW Pacific Ocean). Refer to Fig. S1 for particular sea urchin and macroalgal species occurring within each reef system.

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