Tegneretal97 Small Scale, Low Frequency Oceanographic Effecs on Kelp Forest Succession

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122 Mar Ecol Prog S er 146: 117- 134, 1997

2.5Macrocvs t i s pyr i fera - 8m Central- 5m Central- 2m Central- 8m North

--b 18m South

1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

l 0 1 18m Central

1.0:

15m Central

1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

r 2 5--01

22.0

1.5

1 .o 12m Central

0.5

0.0

1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

1.0-

1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

18m South

Fig. 3. Macrocy stispyrifera . Density of adult (defin ed as 4 or more stipes, Dayton et al. 1992) giant kelp de termined quarterly at

the long-term study sites. 1983 to 1995. Error bars represent *l SD

s to rm s of 1982-1983 a n d 1988 . Be c a us e bo th e ve n ts conspec if ics . At th e 3 sites w h e r e recruitment

w e r e ca tas trophic in te rm s of the ir des truc tion of occurred immedia te ly after t h e dis turbances (1 8 mgia n t ke lp popu la t ions , t h e first pos t-dis turbance Sou th be c a m e a n urchin ba r re n after th e 1988 storm

cohorts faced little competi t ion from exis t ing a du l t a n d 12 m Ce nt ra l w as initially dom ina te d by Des-



Tegner et al.: Oceanographic effects on kelp forest succession 125

Fig. 6 . Macrocystis pyrifera. Changesin the mean numbe r of stipes (growth)

per plant and stipe density (carryingcapaci ty) as functions of pla nt densityat (A ) 18 m Central and (B ) 15 m

Central, 1983 to 1995



12 6 Mar Ecol Prog Ser 146 : 117-134, 1997

7 1 A. P t e r v q o ~ h o r a c a l i f o r n i c a

--C 15mCer.:ral

+ 2m Central

U 8rnNonh

+ 8m South

40 1 B. L a m i n a r i a f a r l o w i i

Fig. 7. Changes In (A ) dens ity of

understory kelp Pterygophora

californica, an d (B ) percent

cover of understory kelp Lamj-

nan d farlorvi!, 1983 to 1995 at

1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 th e 5 permanent sites

permanent sites (except 18 m South du e to sea urchin

grazing in 1986). The very cold La Nina conditionsafter the 1988 storm were associated with extraordi-

nary M. pyrifera growth and declines in L. farlowii

percent cover to zero at all sites between 1989 and

1991. L , farlowili was a bsen t for Interv als of 1 to 3 yr

until th e decline of local M. pyrifera stands allowed

for new recruitment.

Other algae

The other algal groups showed several patterns. The

annual Desmarestia spp. responded to storm and graz-

ing disturbances with short-term bursts in percent

cover (dat a not shown) . Cystoseira osmundacea also

recruited at some sites after each major disturbance,

but only persisted at trace levels in both the 1980s andthe 1990s; his is consistent with the low survivorship of

cohorts of this species obser ved in the 1970s (Dayton et

al. 1984). Coralline alga e (Fi g. lOA), well kno wn for

their de ep distributions (e. g. Lobban et al. 1985),

showed no evidence of response to the different tem-

perature/Macrocystis pyrifera regimes nor to the 1988

storm. Foliose red al gae, although they expen enced

major recruitment peaks at some sites during the

1983-1984 El Nino, were generally similar to coral-

lines. Brown turf (Dictyotaceae) persistence, however,

followed a patte rn very similar to tha t of th e understory

kelps; these recruited strongly after both major distur-

bances at 18 and 15 m Central, persisted at low levels

until the 1988 storm, virtually disappeared from mid



T e g n e r e t a1 . Oceano graphic e f fec ts on ke lp fores t succession 12 7

0. 5 18m C e n t r a l o 25

0. 4+ acrocystis 0 20- terygophora

0. 3 0 15

0 2 0.10

0.1 0.05

0.0 0.00

1 9 8 3 1 9 8 4 1 9 85 1 9 8 6 1 9 8 7 1 9 8 8 1 9 8 9 1 9 9 0 1 9 9 1 1 9 9 2 1 9 9 3 1 9 9 4 1 9 9 5 1 9 9 6

1 o15m C e n t r a l 6 o

0.8

4.00.6

0 42.0

0. 2

0 .0 00 p

-mX 3 .0 80 L0)z a

c1 6.0

, 2.0 .-m.-mC

4.0D

d 1.0

V)2 0.- 0

.c

0 .0 00 21 9 8 3 1 9 8 4 1 9 8 5 1 9 8 6 1 9 8 7 1 9 8 8 1 9 8 9 1 9 9 0 1 9 9 1 1 9 9 2 1 9 9 3 1 9 9 4 1 9 9 5 1 9 9 6 ?

90

18 m Northc

I C

Flg 8 Macrocys t i spynfe ra an d Pterygophora californica. Cha nges in ke lp dens i t i e s a t each of t he pe rm anen t s i te s , 1983 to 1995.

Error ba rs repres ent * l SD. Note sca l e changes a mon g s pec ies and s i t e s

1989 through 1992, an d then reapp eared as pos t-1988- sen ce of s tress , an ecosys tem achiev es a higher leve l of

s torm M. pyrifera cohorts dec lined (Fig. 1 0 B ) . orga n iz a tion , whe re a s in the p re s e nc e of s e v e re s t r e ss ,

the process of organiza tion is like ly to be s lowed an d

the u l t im a te s tea dy s ta te tha t m igh t be r e a c he d would

DISCUSSION be a t a lower leve l of orga n iz a tion . T urk ing ton e t a l .

(1993) , es t in g the hypo thes is tha t the e ffec ts of inte r-

Odu m (1981) comp ared the diffe rent tra jec tor ies of spec if ic competi t ion would dec lin e a long gradient s ofs uc c es s ion in e nv i ronm e nts w i th a nd w i thou t s e ve re de c re a s ing nu t r i e n t s a nd inc re a s ing d i s tu rba nc e

e nv i ronm e nta l s t r e s s. He s ugge s te d tha t , in the a b - a m on g pa s tu re p la n t s , de m ons t r a te d tha t nu t r i e n t s



12 8 Mar Ecol Prog Ser 146: 117-134, 1997

0.518m Centra l

30

0.4- E Macrocystis- aminaria

0.320

0.210

0

0.0 0

1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

U mm 'EL 3.0a 12m Centra l 6 .$a- E2 2.0.-U) ;C

m

10

.-2 g- U

2

0 0.0 0 :

1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 l994 1995 1996 gI" a

18m North

0.518m South

4

0.43

0.3

2

0.2

01

0.0 0

Fig. 9 . Changes In Macrocystispyrdera dens i ty an d Lamjnarja farlowii percen t cover at each of the perm anen t s i tes , 1 .983 o 1995.E rro r bars rep resen t t SD Note sca le changes amon g spec les and s i t es

and disturbance interact to determine community

structure. Here we compared succession after 2 cata-

strophic disturbances under contrasting oceano-

graphic regimes, the nutrient-stressed El Nino condi-

tions of 1983-1984 and , on the opposite end of the

spectrum, the very cold, nutrient-rich La Nina condi-tions of 1988-1989. These different oceanographic

regimes had different effects on succession, notably on

the performance of the competitive dominant itself and

on its competitors. In both cases the unusual oceano-

graphic conditions lasted for about 2 yr, but the appar-

ent effects on community structure persisted for the life

of the post-disturbance Macrocystis pyrifera cohorts,

despite relatively normal oceanographic conditionsfrom 1985 to 1987 and relatively warm waters in recen t

years.



Tegner et al.. Oceano graphic effects on kelp forest succession 129

A. Articulated Coral l ines

I 18mCenlral

1 15mCenlral- 2m Cenlral

5 2 0l8m Nonh

LQ)

5 - 8m South0

0

ad

C

a,

2 1 0a

a

0

B. Brown Turf (Dictyotaceae)

Fig. 10. Chan ges in pe rcen t cover of (A ) articulated corallines an d (B ) brown turf algae (Dictyotaceae) at the 5 permanen t sites,

1983 to 1995

MacrocystispyrLfera performance varied considerably

over the study period. Intense recruitment followed bothmajor disturbances, but there the similarities ended.

Giant kelp plants that survived the 1982-1983 storms

formed a sparse canopy in late spring, but the canopy be-

gan to deteriora te in summer, and by October, the tallest

plants were 6 to 8 m below the surface; there was also

subst antia l mortality of plan ts that survived the storms

(Tegner&Dayton 1987).New cohorts of adu lts recruited

in summer and fall 1983, but these had poor growth

(Dayton & Tegner 1984) and survival relative to post-

disturbance cohorts in 1988 (Fig. 5) . Canopy area was

very low in 1983-1985 before it began to recover; 1986

and 1987 were relatively normal years in terms ofcanopy coverage and oceanography (Fig. 2). Excellent

growth conditions in 1988 were reflected in the more

rapid post-storm recovery of the canopy an d the better

survival of initial post-disturbance cohorts (Fig.5) .SomeM.pyrifera plants that had lost all their stipes in the 1988

storm produced new stipes and lived several months

longer, whereas the nutrient-stressed plants damaged

by the 1982-1983 storms generally had very poor sur-

vival and no recovery was observed of plants tha t had

lost all their sti pes (Dayton et al. 1992). Two years of

anomalously cold water resulted in peak s in both canopy

area and kelp harvest in 1990 (Fig. 2). The post-1988-

storm M.pyrifera cohorts showed their sensitivity to the

relatively warm water, inte rmittent El Niiio conditions of

1991-1993 with reductions in harvest and canopy area ,

poor growth in stipe number, and reduced carryingcapacity, but appa rently not throu gh mortality (Figs. 2 , 3

& 6).



134 Mar Ecol Prog Ser 146: 117-134, 1997

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This article was submitte d to the editor

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Manuscript first received: May 28, 1996

Revised version accepted: October 14, 1996

Tegneretal97 Small Scale, Low Frequency Oceanographic Effecs on Kelp Forest Succession

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