The Sea Journal of the Korean Society of Oceanography Vol. 12, No. 3, pp. 125 132, August 2007 z to Œ n } qsp* x r t r~ ~d s 1 t 2 2 (v) nl Šn 1r m 2d p dn Interaction between Invertebrate Grazers and Seaweeds in the East Coast of Korea J. W. YOO*, H. J. KIM, H. J. LEE, C. G. LEE, C. S. KIM, J. S. HONG 1, J. P. HONG 2 AND D. S. KIM 2 Korea Institute of Coastal Ecology, Inc., Incheon 402-835, Korea 1 Department of Oceanography, Inha University, Incheon 402-751, Korea 2 East Fisheries Research Institute, NFRDI, Kangnung 210-861, Korea se- s qnp r o l 12sp sel l ~ p e (PCGR, per capita grazing rate, g seaweeds/individual/day)p, sp ep r p p l. sep ~ r PCGRp power curve(y=0.2310x 0.3290 )l r l p rp 0.8864m. p sep PCGR p ~ pp, e pp ~ o l p v k p Žkl. s ~ r PCGRp r m, qp ~ sp prp eqp p r. e k ~ qn(grazing impact, mg/m 2 )p, sql q m p ~p (Aplysia kurodai, k 2,513 mg/m 2 )p p ˆ, pp (Strongylocentrotus nudus, k 1,500 mg/)m (S. intermedius, 733 mg/m 2 ) p p ˆ. n o r 4,000 ~ pp ˆmn, Elasmopus sp.m 2,000 ~ pp eovmnp, Jassa falcatap ep 3.435m 1.697 mg/m 2 /dayp p ˆ. ll r se vp s s e p qnp p 5,045 mg/m 2 /dayp p ˆ. e l m nl rqp qnp p p p s sl v ppp r pl. p n 3 ~/m 2 p el ep } kelp s (k 5 ton/ha)p p ml. le p ek sl e v rqp ( s p k 16%)p p ml. sq l e sep ll p sr ppp k, lm se qnl pp (lp )p sql ƒ o p qqp v p m. We estimated the distribution of predator-prey interaction strengths for 12 species of herbivores (including amphipods, isopods, gastropods, and sea urchins) and made a regression model that may be applicable to other species. Laboratory experiments were used to determine per capita grazing rate (PCGR; g seaweeds/individual/ day). Relationship between the biomass of individual grazers and fourth-root transformed PCGR was fitted to power curve (y=0.2310x 0.3290, r=0.8864). This finding supported that the grazing efficiency was not even as individual grazers increase in size (biomass). Therefore, the biomass-normalized PCGR was estimated and revealed that smaller size herbivores were more effective grazers. Grazing impact considering density of each taxon was calculated. The sea hare Aplysia kurodai had greatest grazing impact on the seaweed bed and the sea urchin Strongylocentrotus nudus and S. intermedius were ranked in descending order of the impact. The amount of seaweed grazed by the amphipod Elasmopus sp. (>4,000 ind./m 2 ) and Jassa falcata (>2,000 ind./m 2 ) were 3.435 and 1.697 mg/m 2 /day respectively. The combined grazing amount of herbivores was 5,045 mg/m 2 /day in the seaweed bed. Although sea hare and sea urchin had strong impacts on seaweeds, the effects of dense, smaller species could not be seen as negligible. Surprisingly, the calculated grazing potential of sea urchins with a mean density of 3 ind./m 2 exceeded the mean production of seaweed cultured in domestic coastal waters in Korea (ca., *Corresponding author: jwyoo@coastkorea.com 125
126 oqoë vëp rëp}ë}ë që r Ë 5 ton/ha). Small crustaceans were also expected to consume up to 16% of the seaweed production if their densities were rising under weak predation conditions. Considering that the population density of herbivores are strongly controlled by fish, human interference like overfishing may have strong negative effects on persistence of seaweeds communities. Keywords: Macroalgal Bed, Herbivore, Seaweed-Grazer Interaction, Grazer Impact, Per Capita Grazing Rate sq(macroalgal bed)p lklp p kp ov l l, k rl vp, om r l oq koqp r, pl p 2 p lklp pp v l t n l p (Steneck et al., 2002). qvp ll l klp sep sql ƒ m p v, sq (p p)p tn np n v p(estes et al., 1998; Dean et al., 2000; Duffy and Hay, 2000). r n p(m l, ENSO event rr m )l p sq lrp, v p v kp l, m p se ekl p p n krrp, m v p vp(steneck et al., 2002). lklp pp p vm k s l e k rp. lkl p tp n lkl pp ql p p p. p r p, pr kp re o sel p ekl ~rp k r n, q l p r r l(, 2001; o, 2004)p sq. Duffy and Hay(2000)l p nl k sp, q p ~ mesograzer mesoherbivore( copepod size 2.5 cm, p t se; Brawley, 1992)l p ek le e tp k p r. k ~ ekl r o l tnp. sl v se p ekp ˆ o e- e plv p(-)p qn(negative interaction)p p. Sala and Graham(2002)p s p r p q~ p e r l l se s 1 ~ qnp (per capita interaction strength) r m. pp r qnp sp sl r (%, se m se sq/q e q~p p ) sep ~ r (v, Michaelis-Menten function) p p ˆ. lvp k sep ~p r ~ qnp r p, rr qpp e p rr p ~ e(per capita grazing rate)p m le p m. Sala and Graham(2002)p p s qnp r m p p (1) v l t r l p sp mkl Žk (2) edšp kr n l r p p m t p l n tn pp p l p. k l rr p ~ ekp m p v, lm l l lql p ek l m vep r, lklp sqp s l pl tn r r pp p. l p se ekl r q kvv kp se p edš l l p k s p sep rr e m ~p r edš qnp ˆ r p Žk l np t pp p. l (1) t ˆ e (mesocosm experiment)p l 12sp ~ 1p e(per capita grazing rate, g seaweeds/individual/day, p PCGR)p r p ˆp s PCGRp m p r, (2) r p r l e np se qnp rl n, (3) sq edš se s qnp m p Žk p trp. m m e sep l~ sp 8s, p 1s, 2s p 1s 12spl. e sp, sp (Aplysia kurodai), (Barleeia sp.), l(cantharidus callichroa), (Chlorostoma argyrostoma turbinata), Žk(Homalopoma sangarense), r(nordotis discus), (Omphalius rusticus), (Turbo sp.)m p e q(dynoides dentisinus) p mn(amphithoe spp.), (Caprella spp.) p (Strongylocentrotus nudus) pl. se p e e r 7p pl o } l q }v p, }v v q d pn l lv nl. lp s el e vrv e p, s l ˆ v k m. se p ~p l v t, v t se (,, s ) se(, s ) l. pl p p. t sep n p el sp e(laminaria japonica) m, 2005 6o 9ol sp
k se } s qn 127 (Pachymeniopsis elliptica) sp (Ecklonia stolonifera) pn l e m. sep n, op sm s nl l(undaria pinnatifida)p q(sargassum fulvellum) p sm sp n(gelidium amansii) p m. se p s lp, t se tl sp 500 ml, se tl sp 20 lp o nl sm l e p m. p o n 1 mm p }p p s m 24e k l e p m. ms ep rr qnp rp o l p s pn l t ˆ e s( sp t l p eq ˆ sp p r ) l e m. e p 2005 4o(m e ), 5o, 6o, 7o, 9o 11o p 6 l ~ e 24e k p e qpp e l. e k lp s l r m p - o 2005 4op 11.2 C 7op o 18.7 o C m, 2005 4o 11ov r rp r ˆl. m e e rp plvv kkp, l p r op k sqp lk rr 4()m tv lk rr 5(l nq )l r m ql p - o 32.89-34.33 p 1.5 pmp e l por m p r k p Ž m. o n l se ~ sm l 24 e s dt p r mp, r ˆ e (blank, s l o n)p pm, r m. sp dtp p el p ˆ l e m p tnpp p p Žl. e rl m e p l 4 sp dt p 30 p r pp el rp mp, dtp 0.05±0.03%(n=52) p ˆ. e el 30 pl r dtp r, p 3 l r p ˆe l r m. o n p sep ~ o 1~14~m. ~ 2005 11ol e s, Barleeia sp.p pl. l ~p o nl p po pp s ep p ml p. p sp 2005 10 o qll }v e(l. japonica) 13.369 gl 7~ p (e 2 g k 1 ~ e, 1 ~ ~ 0.001 g )lp, k 6 gp e p e p s 1 g k 2 ~m. ql p m ~ ~ tp pr p o n l s qp o r v k k. n p ep ~ l 24e kp 1 ~ ep ˆl. e e p ~ 2~3p o n n l ep r m. 2005 4o 11ovp e p k sep p PCGRp r p pn l s ~ dt PCGR r m. p PCGRp p Ž p l r (4th root transformation, )p m. r p p t p, p qr, v, p Ž p p rp se t, p p p p o l ˆt r p ov. dtp, PCGRp s ql (y=a+bx) p Michaelis-Menten function(saturation growthrate model, y=ax/(b+x)) power function model(y=ax b )p rn mp, r Š l ˆ p r m. l e p v kkp, r p qlp l PCGRp ~, ~ m pp p p p psp r pp p Ž m. m r, l, pp p l p r e q~ dtp m/rr v kp pp rr p, lqp p rp ˆ l r p p p rp p Ž m. e, rr e el n p r p ln p m mp, p / p r dtp p p j n p v, n~ ep le e p p n pp t p v kpp ve p km. se e p pp s o l ~ p r PCGR(biomass-normalized PCGR, v, se 1g 1p s e, p ~ r PCGR)p r m. p p ~ slp s el p sq o p. ~ r PCGRp s ~p op sq v Ž k o l Pearson n m. l k sqp o r se ~ ~ ~ q( 29s) n l ~ p vp 1p e(grazing impact, mg/m 2 /day) p r m. sep rm ~ ~p v k~(1999)m l(2002, 2005)p q s m. r r l o l em ~p pnlk p p r p ql e el p p Œplk. r r s om e p n lp r,, l r p lp p p p p. o z PCGR Table 1p sep r PCGR(g seaweeds/individual/
128 oqoë vëp rëp}ë}ë që r Ë Table 1. Comparison of linear/non-linear fitting results on the relationship between grazer biomassg (wet weight) and 4th root transformed PCGRG(per capita grazing rate, g seaweeds/individual/day) Model type Equation Standard error Correlation Linear Fit y=0.279+0.010x 0.130 0.919 Saturation Growth-Rate Model (Michaelis-Menten Model) y=1.453x/(14.881+x) 0.183 0.833 Power Fit y=0.231x 0.329 0.153 0.886 Fig. 1. Relationship between the individual biomass(g) and 4th root-transformed PCGR(g) data fitted by non-linear model(power curve fit). day) ~(dt, g WWt/individual) ql rn v p p v ppp lt p. n p q p (r=0.92)p ˆ. v p yrp 0.27923p p r l ~p 0p k 0.006gp e p ml, p 0p lk se ~ PCGR rr p Žl. p ˆ p v v n r n p power curve (0.89 vs. 0.83)pl. Fig. 1p power curvel p r ˆ p, ~ r (y=0.2310x )p t 0.3290 ep vrp p ˆ. z o PCGR op r sep PCGRp ~ r l pp,, ~ o l, e pp p v kp p Žkl. Fig. 2 ~ r PCGRp r, s s nv m l p. m e p rn 2005 5o 11ovp l 2 p e p s(12s n 5s) p n m. sp (Aplysia kurodai), r(nordotis discus), Žk (Homalopoma sangarense), (S. nudus), mn (Amphithoe spp.) pl. Fig. 2 sp (A. kurodai) (S. nudus)v ~ r PCGRp ±0.007 g p p p ˆ. Fig. 2. Comparions of biomass-normalized PCGR among species. Cha, Ch. argyrostoma turbinata; Ak, A. kurodai; Or, O. rusticus; Nd, N. discus; Hs, H. sangarense; Cc, C. callichroa; Sn, S. nudus; Dd, D. dentisinus, As, Amphithoe spp.; Bs, Barleeia sp.; Cs, Caprella spp.; Ts, Turbo sp. (S. nudus)p n 5o, 7o, 9o 11ol e p lp 0.006 0.026 gp o( 0.015±0.007 g) p ˆ. mn, Amphithoe spp.p n 5o, 6 o 11ol e p lp 0.198 0.346 gp o (, 0.253±0.081 g) p ˆ. ~ r PCGRp s ~ l op sq p Ž pl(n=36, Pearson s r = -0.307, p-value = 0.068). o z sm mk }o r PCGR s p p ~ e n l ~ qn(grazing impact, mg/m )p 2 m(table 2). sql q m p ~p (A. kurodai, k 2,513 mg/m )p p 2 ˆ, pp (S. nudus, k 1,500 mg/m )m 2 (S. intermedius, 733 mg/m 2 ) p p ˆ. (S. nudus)p e 2 ~/m p p 2 rlp, p Sala and Graham(2002) p Strongylocentrotus purpuratusp e p 1.463 o tp. ~ 0.005 g p p ~ dtp p ˆ. p n o r 4,000 ~ pp ˆmn(Elasmopus sp.)m 2,000~ pp eovmnp(jassa falcata)p ep 3.435m 1.697 mg/m /dayp p 2 ˆ. ~ ep p 5,045 mg/m /dayp p 2 rl.
k se } s qn 129 Table 2. Average biomass, density, PCGR and impact of grazers on seaweeds Taxa Scientific name Biomass (g/ind.) Density (ind./m 2 ) PCGR (mg/ind./day) Impact (mg/m 2 /day) MPo Acanthochiton spp. 0.0300 28.3 0.0282 0.800 CAm Aorcho sp. 0.0010 77.8 0.0003 0.025 CAm Aorides sp. 0.0005 67.8 0.0001 0.009 CAm Amphithoe spp. 0.0050 191.3 0.0027 0.511 MGs Aplysia kurodai 30.0785 10.0 251.2949 2512.949 MGs Barleeia sp. 0.0040 25.6 0.0020 0.051 MGs Cantharidus callichroa 0.0560 40.9 0.0642 2.628 CAm Caprella spp. 0.0020 423.5 0.0008 0.339 MGs Chlorostoma argyrostoma turbinata 28.1190 1.0 229.9757 229.976 CAm Ceradocus sp. 0.0010 1.1 0.0003 <0.001 CAm Corophium spp. 0.0005 57.5 0.0001 0.007 CIs Dynoides dentisinus 0.0040 17.8 0.0020 0.035 CAm Elasmopus sp. 0.0020 4296.0 0.0008 3.435 CAm Ericthonius brasiliensis 0.0030 579.7 0.0014 0.790 CAm Gammaropsis spp. 0.0020 478.9 0.0008 0.383 MGs Homalopoma sangarense 0.0260 498.6 0.0234 11.658 CAm Hyale spp. 0.0050 207.2 0.0027 0.553 MPo Ischinochiton comptus 0.0490 10.0 0.0538 0.538 CAm Jassa falcata 0.0020 2122.5 0.0008 1.697 MPo Lepidozona spp. 0.0120 23.8 0.0085 0.201 MGs Littoraria strirata 0.0080 167.8 0.0050 0.832 CAm Maera serratipalma 0.0030 128.9 0.0014 0.176 MGs Nordotis discus 5.9190 0.4 29.5849 11.834 MGs Omphalius rusticus 2.7200 3.0 10.6336 31.901 CAm Podocerus inconspicuus 0.0020 364.2 0.0008 0.291 CAm Stenothoe sp. 0.0002 588.6 0.0000 0.023 EEc Strongylocentrotus nudus 69.0558 2.0 750.2220 1500.444 EEc Strongylocentrotus intermedius 136.1680 0.4 1833.3626 733.345 MGs Turbo sp. 0.0006 1.0 0.0002 <0.001 CAm, Amphipoda; CIs, Isopoda; MGs, Gastropoda; MPo, Polyplacophora; EEc, Echinoidea }om m l PCGRp 1~ 1p s e p t mp, (1) ~ l s ql p l, (2) eq l ekp m p r, (3) e e pp qp pp l s pp rr mp p 1p e(maximum per capita grazing rate) p ˆ (Sala and Graham, 2002). se ~-PCGR p rl pl r (y=0.2310x )p tep vrp p 0.3290 ˆ. k e(v, e ep k m s)p p lpl lvp ˆ p p p lvp el rr ~ pl p l v k rp ˆ ppp ˆ p p. p sl se p qnp ~ power curvep p k plp, m k pl. y l ~ ekp r l p k kl e (S. nudus)p n pl r p pl. ql e}l nˆ e (enclosure experiment)p o (2004)p 2002 8 ol 0.160, 10ol 0.025, 0.002 g seaweeds/g sea urchin/dayp r mp, el e p (2001)p n 3sp (Hemicentrotus pulcherrimus, S. nudus, S. intermedius)p 2001 3o 9o e ep 0.083-0.184, 0.072-0.102 g seaweeds/g sea urchin/dayp p rl. o (2004)p 8o 10o e r p p rrp Ž p sp pl p p k. l p p r el lp 0.062 g seaweeds/g sea urchin/dayp p ˆ. l p p 0.015 g seaweeds/g sea urchin/day 4 p Fig. 3p rrp m p o(mg-g)m o tl p plp, ˆp p Ž pl. k l m p, Sala and Graham(2002)p e l se q~ qnp p Michaelis-Menten
130 oqoë vëp rëp}ë}ë që r Ë Fig. 3. Frequency distribution of grazing impact of 29 populations. l r p ˆ. p p rp v s p Ž p p, p r p q~ p p ~ se p pr ep p l p sekp p (size refuge) p l p o p r v p l m. sp m~ n l l p sekp p (size refuge) ll ll power curve ˆp r p r p pp o (q~ m~) rp, e se ~l e pl r p p ppp ve p p Žl. Sala and Graham(2002)p e rl r q~l v p(-)p qnp r p rn o s m~ l rn lv sp m~ p lp t k ˆ r p l ~ m~l se p impact r l pn pp p. s ~ r PCGRp Fig. 2 sp 7 ~p n p tplp, np e q(dynoides dentisinus), mn(amphithoe spp.), (Caprella spp.) s Barleeia sp., Turbo sp. l o p p l. pp sl sl ~p qp s p. ~ r PCGRp s ~ s qp np sp s prp eqp p r plv p. s mkm j qk l re ~ qnp p 5,045 mg/m /dayp p 2 ˆ. p se vp s p p o r k 5gp s l ep p p. pm p r p p rp er qp m p pp p m p. ~w, ll r PCGRp, k l m p, eq ps qqp p l p l s p l n p Ž pl. w, ~p 1m l 2 Table 2p p s e pp p n. p ~(m l ˆ mn(elasmopus sp.), spmn(hyale spp.) p n e} p tep sl n~ v s p e}l p n p p rl. w, dp p sp m (epiphytes) s e qep, lp r pp sp e nl p. p rp ql e}l se ~p qn r p p 5g p p Ž p. vp ~ qnp vp s m ˆ p n tn l. sql e Table 2p 29 se ~p p s PCGR ~p qn r rp k qnp sp n mp pp qnp p ˆ(Fig. 3). p e r l Žk edš ~ qnp l l m o p. m l Paine(1992)p Berlow(1999) m p lqp ˆ p ~ (per capita effect) k qnq ol p qnqp sq Ž p p r k m. p pr l(m l, May, 1973)p p edšp qn n edšl p psl krp p p m p. Berlow(1999)p ll p k qnqp p kr l noise-dampening rolep p ˆp, p po pp p ql ˆp vl ƒ o p p m m. qv sq l kl m p qnql rp lr plp, sm p k qnql l r p p. pm, nl l lql p pp qqr p pv srnpl l p (Duffy and Hay, 2000; Christie and Kraufvelin, 2003). k qnq l sq edšp krp l p p o e r l n p. m m omi i sq ˆl e k sep er p n p, kvv pl p s p. lp s rp p m rp sqp sep sl qqr p p m pl. e p sql v p(-)p qn n m ~ p qnql p p p v p ˆp p nl sl p p s pp p l p rqp qnp v pp, prp ep p r pl. e Sala and Graham(2002)p e p o prp, sqp l rrp m p p l q~p pl rp qp ~ qnqp e l p p
k se } s qn 131 m pl. kl o (2004)p e l p q q l sqp (S. nudus)p em ~p 3 ~/m 2, 69.417 g/~, 1 ~/m 2, 95.905 g/~m. l p p rn l r p q ql sqp qnp 2266.19m 1155.87 mg/m 2 pl. p ha l ep, 8.3 4.2 ton/ha/yearpl. 2005 p } kelll p sp p rp k 5 ton/ha(, 621,156 ton, } kell r, 124,668 ha; k, http://www.momaf.go.kr)pp k 3 ~/m 2 p(k 210 g)p e tp s p pl v p p p p v. p (S. nudus) 1m 2 200 g p e n s e p m p p ˆ ž(2001)p e m o tp p. qp ~ qnq n p ep sql e sep ek ol r p t l p ˆ. p ~p e ~ qnp r l tn m p pp p ˆ p p. Christie and Kraufvelin(2003)p t ˆ e l porp s p ek s (p Carcinus maenasm p Asterias rubens, m l )l m 2l t sep e l 500,000~2,000,000 ~/8 m p ˆ. k l m p, erp p lp m e r (k 10,000 ~/m ) n ek r 2 8.3 10-3 g/m 2 /daym. k p ek s l pp 25 r v pl p ekp k 0.21 g/m 2 / day, 0.8 ton/ha/yearl p. 2005 p } kelll p sp (5 ton/ha) p e l tp. ql sq edšp ll p ep } p e sr l tn l p (Christie and Kraufvelin, 2003). ol l se n l ekp pp e l m p t, rp sqp o ppp p l lqp q kr p (o, 2004; McClanahan and Muthiga, 1989; Sala and Zabala, 1996; Estes et al., 1998). qv kv pp eq, s,, l(u,,,, l ) p p(o, 1996; o, 2004; McClanahan and Muthiga, 1989; Sala and Zabala, 1996). le ll p vtrp pn p tn pop p p o n l q k r pp( l, 2002, 2005;, 2003), p ~ p l eql p prp sr p p(fjφsne and Gjφsæter, 1996; McCurdy et al., 2005). o (2004)p eq-se- sq e sr(topdown control) p r mp, Estes et al.(1998)p k l p p p. Christie and Kraufvelin(2003)p e l p tp mkm ~l se ~p n pp mp p l e e sr(bottom-up control)p p p p r p p. p ekp k npl p o eq s p p t l l p m p p p lpp k p pp v ol p p. k m p e- e p m e srp p rr p qo p sel v ekp p, pp e p v eˆ p. l p p sql ƒ oeˆ p qqp v p mp rk l p }p p. p r p s k s l rp plv p, n lk p sqp l on n p e p, r r l p v p. m l 2005 op sq s r se ˆ l p p p ld. p Š l np te t) lk ˆlp rdo lo op o. p e e l vrp te } p eoo. y o, 1996. e-r36 ( ). o, 780 pp. l, 2002. sq se l( s). o l, 163 pp. l, 2005. sq s r se ˆ l. o l, 115 pp. p, 2003. p} rp vsm p. p p o, 273 pp. n, 2001. k sq s ep. k p o sq s o, v o l, pp. 1 9. oqo, n, p}, r, }, }, m,, q, 2004. k } l e, Strongylocentrotus nudusp m e Ž. k v,, 9: 40 49. v k~, 1999. Žr q m s. v k~, 176pp. ÓÔÇ Ô -³Â ÄÔ -. ɪ. žé³, 2001. Berlow, E.L., 1999. Strong effects of weak interactions in ecological communities. Nature, 398: 330 334. Brawley, S.H., 1992. Mesoherbivores. In: Price, J.H., D.M. John, S.J. Hawkins (eds.), Plant-animal interactions in the marine benthos. Systematics Association Special Volume 46. Clarendon Press, Oxford, 235 263.
132 oqoë vëp rëp}ë}ë që r Ë Christie, H. and P. Kraufvelin, 2003. Mechanisms regulating amphipod population density within macroalgal communities with low predator impact. Scientia Marina, 67: 1 10. Dean, T.A., J.L. Bodkin, S.C. Jewett, D.H. Monson and D. Jung, 2000. Changes in sea urchin and kelp following a reduction in sea otter density as a result of the Exxon Valdez oil spill. Mar. Ecol. Prog. Ser., 199: 281 291. Duffy, J.E. and M.E. Hay, 2000. Strong impacts of grazing amphipods on the organization of a benthic community. Ecological Monograph, 70: 237 263. Estes, J.A., M.T. Tinker, T.M. Williams and D.F. Doak, 1998. Killer whale predation on sea otters linking oceanic and nearshore ecosystems. Science, 282: 473 476 Fjφsne K. and Gjφsæter J., 1996. Dietary composition and the potential of food competition between 0-group cod (Gadus morhual.) and some other fish species in the littorial zone. ICES Journal of Marine Science, Volume 53, Issue 5, pp 757 770. May, R.T., 1973. Stability and complexity in model ecosystems. Princeton Univ. Press, Princeton, NJ. McClanahan, T.R. and N.A., Muthiga, 1989. Patterns of predation on a sea urchin, Echinometra mathaei (de Blainville), on Kenyan coral reefs. J. Exp. Mar. Biol. Ecol., 126: 77 94. McCurdy, D.G., M.R. Forbes, S.P. Logan, D. Lancaster, S.I. Mautner, 2005. Foraging and impacts by benthic fish on the intertidal amphipod Corophium volutator. Journal of Crustacean Biology, 25(4): 558 564. Paine, R.T., 1992. Food-web analysis through field measurement of per capita interaction strength. Nature, 355: 73 75. Sala, E. and M.H. Graham, 2002. Community-wide distribution of predator-prey interaction strength in kelp forests. PNAS, 99: 3678 3683. Sala, E. and M. Zabala, 1996. Fish predation and the structure of the sea urchin Paracentrotus lividus populations in the NW Mediterranean. Mar. Ecol. Prog. Ser., 140: 71 81. Steneck, R.S., M.H. Grahan, B.J. Bourque, D. Corbett, J.M. Erlandson, J.A. Estes and M.J. Tegner, 2002. Kelp forest ecosystems: biodiversity, stability, resilience and future. Environmental Conservation, 29: 436 459. 2007 1o 15p or 2007 3o 15p r }ˆ voo: e