Vol. 193: 241-249.20OOMARINE ECOLOGY PROGRESS SERIES

Mar Ecol Prog SerPublished February 28

Bio-mineralogy as a structuring factor for marineepibenthic communities

G. Bavestrellol'*, C. N. Bianchi2, B. Calcinai3, R. Cattaneo-Vietti3, C. Cerranos,C. Morri3, S. Puce3, M. Sarà3

rlstituto di Scienze del Mare, Università di Ancona, Via Brecce Bianche, 60131 Ancona, Italy2Marine Environment Research Centre, ENEA Santa Teresa, PO Box 316, 19100 La Spezia, Italy

3Dipartimento per lo studio del Territorio e delle sue Risorse, Università di Genova, Viale Benedetto XV 5,16132 Genova, I ta lv

ABSTRACT: The mineralogical features of the substrate were generally considered a minor factor instructudng marine benthic communities. The aim of this work is to verify whether the presence ofquartz minerals in rock may explicate differences, usually explained in terms of substrate roughness orother factors, in epibenthic communities. Laboratory tests on the hydroid Eudendrium glomeratumshowed that its planulae settle preferentially on carbonatic, rather than quartzitic, substrates. To testthe influence of quartz on established communities, we analysed the species composítion and quanti-tative structure of sublittoral sessile assemblages on different rocks in several localities of the Ligurianand Tyrrhenian seas. The observed differences appeared to be related to the presence of quartz in thesubstrate rock. The interactions between organisms and minerals (bio-mineralogy) might play a signif-icant role on benthic communities, affecting not only the initial colonlsation, but also later assemblages.This potential role has been largely neglected to date and further studies are needed to prove its impor-tance.

KEY WORDS: Substrate colonisation Mineral comoosition Marine benthos distribution . Hardsubstrates . Bio-mineralogy

INTRODUCTION

The spatial distribution and structure of marine ben-

thic communities are due to numerous abiotic and

biotic factors which, in turn, are influenced by thepresence of the organisms, in a mutual exchange ofinputs. Among the abiotic factors, the mineralogical

features of the substrate were generally considered of

scarce importance, but recent studies by Cerrano et al,(1998) have shown that the presence of quartz in the

sand may affect the initial steps of infauna colonisa-

t ion. Cerrano et al. (1998) introduced the term bio-min-

eralogy to explicate the interrelationships between

biological systems at different hierarchies (cell, organ-ism, species, community) and minerals.

Bio-mineralogy could influence hard-bottom assem-

blaqes and explain some 'anomalies' in the structure of

' E-mail: bave@promix.it

@ Inter-Research 2000

Resale of full article not permitted

communities growing on rocks of different nature. A

species assemblage, which may be slightly more

attracted to a particular substrate, could affect succes-

sion by its subsequent interaction with later assem-

blages. A similar effect was evidenced in the colonisa-

tion of artificial substrates, with respect to both species

composition and abundance (Anderson & Underwood

1994, Holm et al, 1997). Less information is avai lable

for natural substrates (McGuiness 1989), but i t is com-

mon knowledge that the softness and asperity of a rock

can favour or hamper biotic colonisation through selec-

tive larval settling, retention of water (in the littoral)

and organic matter, and provision of refuges from pre-

dation or grazing (Den Hartog 7972, Levinlon 1982,

Walters & Wethey 1996).

More is known about the influence of substrate mrn-

eraÌogy on bioboring, which is prevented by high

percentages of quartzitic or pelitic components in

the rock. Sublittoral endolitic communities are charac-

242 Mar Ecol Prog Ser 193:241,-249,2O0O

Fig. 1. Subtittoral rock showing differences in the distribution of borers due to themineral composition of the substrate. The white calcitic vein is widely bored by thesponge Cliona celata which is absent on marl limestone (grey). Herein only the date-

mussel Lithophaga lithophaga is able to penetrate (arrows)

terlsed mainly by clionid sponges and bivalves. Clionidsponges use hatching cel l pseudopodes and the pro-duction of carbonic acid to penetrate limestone (Rùt-zler & Rieger 1973, Pomponi 1979), but Cl iona celataGrant preferentially bores, in the Mediterranean Sea,substrates richer than 60%, in carbonates (unpubl.obs.). Bivalves, such as species oî Lithophaga, borewith the help of sulphuric acid and/or neutral muco-proteins (Russo & Cicogna 1992), and are also able topenetrate marl limestone, which is impenetrable bycl ionids (unpubl. obs., Fig. 1). AII this has importantconsequences on the rock texture and roughness and,ultimately, on the community structure.

To check the influence of substrate mineralogy on thelarval settling, a series of laboratory tests was conductedusing planulae of the hydroid Eudendrium glomeratum(Picard), a very common species of the sublittoral Med-iterranean zoobenthos (Boero et al. 1986). In order toseek a relation between the mineralogy of natural sub-strates and the structure of sessile epibenthic communr-t ies, the specles composit ion and percent cover of as-semblages living on different kinds of rock in thewestern Mediterranean Sea were comoared.

during November 1998 at 20 to25 m depth. The fertilised eggsdevelop in verticils of 5 to 10 fixedto a rudimentary polyp, the blas-tostyle, deprived of mouth andtentacles. Each egg is envelopedby a non-branched spadix. Theverticils of eggs were mechani-cally detached from the mothercolony and placed in 250 ml cupsfilled with filtered natural seawater at a temperature of 15'C.

Cerrano et al. (1997) demon-strated that light exposure is nec-essary to trigger egg hatching andtherefore we reared the eggs inIit conditions for 3 d. New re-leased planulae were divided into4 stocks of 60 specimens and eachstock was placed for 12 d in anexperimental Petri dish in com-plete darkness to avoid problems

related to their very high pho-

totrophy. Petri dishes were pre-pared by sticking a uniform layer

of sand grains with Eukitt; half of the surface was cov-ered by quartz sand, and half by sand derived fromCarrara marble. The 2 sand types have the same gran-ulometric (725 to 250 pm) and morphological features(roundness, 0.35 to 0.7; project ion of spherici ty, 0.8 to

MATERIAL AND METHODS

Laboralory. Planulae of the hydroid Eudendriumglomeratum were obtained from female colonies col-lected on the rocky cliff of the Portofino Promontory

Fig. 2. Geographic layout of theurian and Tyrrhenian seas

field-study sites in the Lig-(NW Mediterranean)

Bavestrello et al.: Structurinq of marine epibenthic communities 243

Table 1. Localities for field studies on sublittoral rocky bottoms

Locality Contrasted mineralogies Depthrange (m)

No. ofstatrons

No. ofspecres

Ligurian Sea

Giglio Island

Northeast Sardinia

Quartzite(Gallinaria Island)

Granite (most ofthe island)

Granite (most of thecoast and small islands)

V S Puddingstone, marllimestone and sandstone

(Portofino region)

Limestone (western partof the island)

Limestone-dolomite(Tavolara Island)

5-7

6 - 1 0

1B-34

l 4 60

r t ) 54

20 44

0.9). Both kinds of sand were previously stored at

100"C for 24 h, which enabled us to obtain an artificial

hard bottom on the entire Petri dish surface, with very

simiÌar physical features but with 2 different mineralo-

gies.

Field. The data matrices were produced using un-

published data sets on subtidal epibenthic communi-

ties of the Ligurian Sea (Gallinaria Island and Portofino

region) and Tyrrhenian Sea (Giglio Island and north-

east Sardinia) (Fig. 2). The data sets were chosen in

order to be able to contrast communities from an equal

number of stations on rocks rich in quartz, such as

quartzite and granites, or deprived of that mineral

(Table 1). All data sets consist of percent cover data of

conspicuous species (Hiscock 1987), derived from

underwater visual inventories by SCUBA divers using

quadrats (Bianchi et al. 1991). Cover data for a total of

96 species (Table 2) were available, but each data set

was analysed separately according to depth zone and

geographical location, so that communities only

showed differences in the mineralogical nature of the

substrate and possibly exposure. To avoid the influ-

ence of sedimentation, which may alter the effects

of mineralogical composition at the rock surface

(Bavestrel lo et al. 1995a), vert ical stat ions (70 to 95"

sÌope) were selected. Matrices of species cover data

were compared by correspondence analysis (Legendre

& Legendre 1998), and species numbers and total

cover by 1-way ANOVA. Prior to analysis, percentage

cover values were arcsine transformed to meet the

assumption of homogeneity of variances (Underwood

1997).Field-study sites. The Ligurian Sea data derive from

surveys carried out in shallow water at Gallinaria

Island in the summer oÎ 1991 and in the region of

Portofino Promontory in the summer of 1993. The

Tyrrhenian Sea data include information taken at

infralittoral depths around Giglio Island in September

of 19BB to 1991 and at circalittoral depths in north-

eastern Sardinia in June 1990 lTable 1ì.

The Ligurian Sea has been the object of much

research in marine biology, and many studies have

taken into account the epibenthic communities on the

rocky bottom (Bianchi et al. 1987, Cattaneo-Vietti et al.

19BB). One of the most studied sites is the region

around Portof ino (Tortonese 1958, 1962, Morri et al.

19BB), but recent research has also been done on the

Island of Gall inaria (Balduzzi et 41. 1994). These stud-

ies underlined that epibenthic communities on sublit-

toral rocks at Portofino are dominated by flourishing

gorgonian populations, whereas at Gallinaria, gor-

gonians are scarce and sponges dominate. From a min-

eralogical point of view, Gallinaria Island is exclusiveÌy

quartzit ic (Orsino 1975), whereas the coast around

Portofino is characterised by puddingstone, marl lime-

stone and sandstone, none of which has a significant

quartz component (Boni et al. 1969).

The Giglio Island is included in the southern group

of the Tuscan Archipelago, at the border between Lig-

urian and Tyrrhenian seas. Its rocky coast is mostly

granite, but a small portion on the western side is com-

posed of limestone (Alvisi et al. 1994). The subtidal

epibenthic communities of Giglio Island were first

described by Balduzzi et al. (1996).

The northeast corner of Sardinia is mostly composed

of granite. A striking exception is the Tavolara Island

made by a gigantic limestone-dolomite slab (Lorenzoni

& Chiesura-Lorenzoni 1973). Together with Molara,

Molarotto and other minor islets and rocks (all granitic),

Tavolara forms a small archipelago, the epibenthic

communities of which have been studied by Navone et

a l . (1992) .

RESULTS

Laboratory

After hatching, th.re Eudendrium glomerafum planulae

crawled on the bottom of culture vessel for 2 to 3 d. Then,

they fixed to the substrate by the anterior pole and meta-

morphosed into a planulary polyp, Data showed that

crawling planulae had a strong selectivity for the sub-

strate, being always about 5 times more abundant on the

244 Mar EcoÌ Prog Ser 1,93:241,-249, 2OO0

Table 2. List of the species in inventories of field studies on sublittoral rocky bottoms. Species codes are those used in Figs. 4,6 &7

Code Species,/familyname Phylum Code Species/familyname Phylum

Aab Acetabularia acetabulum(Linnaeus)

P, C. Silva

Aac Acanthella acufa Schmidt

Acr AmphiroacryptarthrodiaZanardini

Ada Axinella damicornis (Esper)

Ali Arbacia lixula (Linnaeus)

Aor Agelas oroides (Schmidt)

Ari Amphiroa rjErjda Lamouroux

Ave Axinella verrucosa (Esper)

Beu Balanophyll iaeuropaea(Risso)

tspo Bd ldnus per lo ra lus Brugu ière

Cad Codium adhaerens C. Agardh

Cbo Caberea boryr (Audouin et Savigny)

Cbu Codium bursa (Linnaeus) C. Agardh

Ccl Clathrina clathîus (Schmidt)

Cco ClathrinacontoÍta(Bowerbank)

Ccr Crambe c.ambe (Schmidt)

Cde Clavelina dellavallei(Zirpolo)

Cel Corallina elongata Ellis et Solander

Cfi Cellaria fistulosa (Linnaeus)

Cfr Codium fragile (Suringar) Hariot

Cgr Corallina granifera Ellis et Solander

Cin Caryophyll iainornata(Duncan)

Cla Cladophora sp.

Cln Clionidae spp,

Cmu Cutleria multifida (Smith) Greville

Cni Cliona nigricans (Schmidt)

Cnu Chondrilla nucu.la Schmidt

Cpa Chartella papyrea (Pallas)

Cpr Cladophora proltferd (Roth) Kùtzing

Cre Chondrosia renrTormis Nardo

Csp Cladostephusspongiosus(Hudson)

C. Agardh

Czo Cystoseirazosteroides(Turner)

C. Agardh

Ddi Dictyota dichotoma (Hudson) Lamouroux

Dpo Dictyopteris polypodioides (De Candolle)

Lamouroux

Dve Dasycladusvermicularis(Scopoli) Krasser

Dvr Dudresnaia vertici l lata(Withering)

Le Jolis

Hco Hemimycalecolumella(Bowerbank)

Hdi Halopteris drapàana (Heller)

Hfi Halopteris filicina (Grateloup) Kiitzing

Hpa Halocynthia paptllosa (Linnaeus)

Htu Halimeda funa (Ell is et Solander)

Lamouroux

hyd Unidentif iedhydroids

Eca Eunicella cavo.lmiì (Koch) CnidariaEra Eudendrium racemosum lGmelin) CnidariaEsr Eunicella sìngularis (Esper) CnidariaFpe Flabellia petiolata (Turra) Nizamuddin ChÌorophytaFru 'Fa lkenberg ia ru fo lanosa ' (Harvey) Schmi tz Rhodophyta

Gob Galaxaura oblungata (Ell is et Solander) Rhodophyta

Lamouroux

Ior lrcinia oros (Schmidt)

Irc fcrria sp.

Iva Ircinia variabil is (Schmidt)

Jru Jania rubens (Linnaeus) Lamouroux

Lfr Lithophyllum frondosum (Dufour) Furnari,

Cormaci et Alongi

Lin LithophyllumjncrustansPhil ippi

Lob Laurencia obfusa (Hudson) Lamouroux

Lpr LeptopsammiapruyofiLacaze-Duthiers

Lva Leucosoleniavariabil isHaeckel

Mli MesophyÌLum lichenoides (Ellis) Lemoine

Mtr Myriapora fruncafa (Pallas)

Mvu Microcosmus vulgaris Heller

Pax Parazoanthusaxinellae{Schmidt)

Pcl Paramuricea clayata (Risso)

Pco Parerythropodiumcoralloides(Pallas)

Pcr Palmophyllumcrassum(Naccari)

Rabenhorst

Pfa Pentapora fascia.lis (Pallas)

Pfi Petrosia ficiformls (Poiret)

Pft Phorbas fictitius (Bowerbank)

Pfu Pseudochlorodesmisfurcellata

(Zanardini) Borgesen

PIi Paracentrotusliyldus(Lamarck)

Pne Phyllophora neruosa (De Candolle)

Grevil le ex J. Agardh

Ppa Padina pavonica (Linnaeus) Lamouroux

Psq Peyssonneliasquantaria(Gmelin)

Decaisne

Pte Phorbas tenacior (Topsent)

Ptr Pomatocerosfriqueúer(Linnaeus)

Ptu Protula tubularia (Montagu)

Rfu Reniera fulva Topsent

Rhy Rhyncozoon sp.

Rvi Reptadeonellaviolacea(Johnston)

Sar Serpulorbisarenafia(Linnaeus)

5Ìau Schizomavella auriculata(Hassall)

Sce Smittina cervicornjs (Pallas)

Sco Sphaerococcuscoronopifolius

(Goodenough et Woodward) C. Agardh

Scu SpirastrellacuncfafrixSchmidt

Sdy Salmacina dysfed (Huxley)

Se1 Sertularella e.llisli (Deshayes et

Milne-Edwards)

s e r U n r d e n t j f i e d s e r p u l i d s

Sla Savignyella.lafonfìi(AudouinetSavigny)

S1o SchizoporellalongrirosfrisHincks

spi Unidentif iedspirorbids

Ssc Stypocaulon scoparium (Linnaeus) Kùtzing

Sse SertellaseptentrionafisHarmer

Svc Serpu la vermicu ld r is L inndeus

Svu Sargrassurn yuÌgrare C. Agardh

Vst Vermiliopsisstriaticeps(Grube)

Vut Valonia utriculadsl (Roth) C. Agardh

Wpe Wrangelia penicillata C. Agardh

Chlorophyta

Porifera

Rhodophyta

Porifera

Echinodermata

Porifera

Rhodophyta

Porifera

Cnidaria

Arthropoda

Chlorophyta

Bryozoa

Chlorophyta

Porifera

Porifera

Porifera

Chordata

Rhodophyta

Bryozoa

Chlorophyta

Rhodophyta

Cnidaria

Chlorophyta

Porifera

Phaeophyta

Porifera

Porifera

Bryozoa

Chlorophyta

Porifera

Phaeophyta

Phaeophyta

Phaeophyta

Phaeophyta

Chlorophyta

Rhodophyta

Porifera

Porifera

Porifera

Rhodophyta

Rhodophyta

Rhodophyta

Rhodophyta

Cnidaria

Porifera

Rhodophyta

Bryozoa

Chordata

Cnidaria

Cnidaria

Cnidaria

Chlorophyta

Bryozoa

Porifera

Porifera

Chlorophyta

Echinodermata

Rhodophyta

Phaeophyta

Rhodophyta

Porifera

Annelida

Annelida

Porifera

Bryozoa

Bryozoa

Mollusca

Bryozoa

Bryozoa

Rhodophyta

Porifera

Annelida

Cnidaria

Annelida

Bryozoa

Annelida

Phaeophyta

Bryozoa

Annelida

Phaeophyta

Annelida

Chlorophyta

Rhodophyta

Porifera

Cnidaria

Phaeophyta

Chordata

Chlorophyta

Cnidaria

carbonatic sediments (Fig. 3a). During the experimentaìt ime (11 d), about one-third of the planulae metamor-phosed and the number of planulary polyps reflected thenumber of planulae present in the different sections of

the dishes (Fig. 3b). The rat io between metamorphosed(settled) and crawling planulae was not significantlydif ferent in the 2 sections (43.3 r 14.6 and 45.6 + 6./" forquartz and carbonate respectively).

Bavestrello et al.: Structurinq of marine epibenthic communities 245

Aab

ACr

60È* s oo

: 4 0o

8 s o", zog

F 1 0

0

hyd pI cel cro

fru Cru S.,Dd, s n,. lor

w7e cre P ^-s ln

^", cpr cDo

Lob t *, tíi' rr."ir, I l#"t

F* , FP, ,r,

t"f Q

o'

Hlu Cc

"'rî'n ML ,,, 0", t'

iro ,,"jfax

Sco

20

R 1 8: 1 5go, tl

8 1 28 1 0l o a9 e. 9 4= 2

0

Arn | (30 90 %)

Fig. 4. Correspondence analysis on sublittoral rocky bottom

data in the Ligurian Sea (Portofino region and GallinariaIsland). The variance fraction explained by the first 2 axes is

indicated. Station points are identified by bold capital letters

according to the nature of the rock. Q: quartzite; S: sandstone;ML: marl limestone; P: puddingstone, Species points are iden-

tified by codes as in Table 2

Ligurian Sea N Tyrrhenian Sea NE Sardinia

Fig. 5. Mean (+1 standard deviation) number of species (a)

and total substratum cover (b) of the epibenthic assemblagesin the 3 study sites, according to rock mineralogy. For eachsite, quartz-rich rocks (quartzìte or granites) (tr), and rocks

poor in or deprived of quartz (8) are represented

HuC c o ̂.

LCt

An . . ChA0a

Pfi

Cnulrc

Rvi

Cad

Sar

Rhv

sprMtr

l i igwa-s*]

6 8 1 0 ' t 2

Days

Fig. 3. Response oî Eudendrium glomeratum planuÌae to dif-ferences in the mineral composition of the substrate. (a) Num-ber of crawÌing planulae on marble (o) and quartz (r) sands,(b) Number of metamorphosed planulae on the same sub-

strates. Data are the means + SE of 4 replicates

Field

The first 2 axes extracted from the correspondence

analyses on the 3 data sets were significant in all cases

(p < 0.05 according to the tables of Lebart 1975). The

fraction of the total variance represented on the plane

formed by the first 2 axes was 45.73 7o for the Ligurian

Sea data set, 43.84 % for Gigl io Island, and 32.00 % for

northeast Sardinia.

Correspondence analysis on Ligurian Sea infralit-

toral epibenthic communities showed, along the 1st

axis, a clear-cut separation of the stations of Gallinaria

Island from those of the Portofino region, the first site

being mainly characterised by quartzitic rock and the

second by dif ferent rock types (Fig. ) . AÌong the 2nd

axis, the station points of Portofino region tended to

spread around according to the nature of their rocky

bottoms, marl limestone separating at one extreme and

sandstone at the other. This last arrangement might

also reflect an exposure gradient, sandstone stations

being located at more exposed sites that the limestone

ones. However, there were station points of equally

exposed sites of Gallinaria, all on quartzitic rock,

which remained well separated from the correspond-

ing ones of Portof ino. Mean species r ichness on the

quartzitic rocks of Gallinaria was lower than on the

non-quartzit ic rocks of the Portof ino region (Fig. 5a):

!' so+l

? z s

xó 2 0

o

I 1 5

i r oo

ì 5

E s oo

o40

246 Mar Ecol Prog Ser 193:247 249,2O0O

S/aHfi P,,

Mvu

uSau Beu

cspSse

vutYsl G

I Lra

L ftel AabCbu

It

Rví QS/o

Aris | (25.74 %)

Fig. 6. Correspondence analysis on sublittoral rocky bottomdata at Giglio Island (northern Tyrrhenian Sea). The variancefraction explained by the first 2 axes is indicated. Stationpoints are identified by bold capital letters according to thenature of the rock. G: granite; L: Iimestone. Species points are

identified bv codes as in Table 2

this difference is significant (1-way ANOVA, p =

0,024), On the contrary, total substratum cover (Fig. 5b)was not signif icantly dif ferent (p = 0.119).

Results from correspondence analysis on infralit-

toral communities of Giglio Island showed a separa-tion of stationpoints along the 1st axis that was consrs-tent with the mineralogical nature of the rock,opposing l imestone to granite (Fig. 6). On the 2ndaxis, limestone station points were closely grouped,

whereas granite station points were more scattered.Looking at the species points (see Table 2 for decod-ing species names), the 2nd axis opposed encrustinginvertebrates to algae and erect or massive inverte-brates: the first assemblage was considered the resultof excess sea-urchin grazing by BaÌduzzi et al. (1996).

Both the number of species (Fig. 5a) and total cover(Fig. 5b) were severely reduced on granite as com-pared with l imestone ( l-way ANOVA, p < 0.001 in

both cases).Correspondence analysis on circalittoral epibenthic

communities of northeastern Sardinia (Tavolara andMolara Archipelago) showed again the separationbetween carbonate (limestone-dolomite) and granite

station points (Fig. 7). On the contrary, no relationshipwas evident with depth, notwithstanding the compara-tively great range investigated (18 to 34 m). Also in thiscase, the number of species on granite was lower thanon limestone-dolomite (Fig. 5a) and, although small,the difference was significant (1-way ANOVA, p =

0.043). In contrast, no dif ference was found for totalcover (p = 0.717).

Lpl

LDLD

I

îfiL D -

LD

Pco

Pla

Dve A0r G

Pcllor

tu is l (18.57 %)

Fì9. 7. Correspondence analysis on sublittoral rocky bottomdata in northeastern Sardinia (Tavolara and Molara Archipel-ago). The variance fraction explained by the first 2 axes isindicated. Station points are identìfìed by bold capital lettersaccording to the nature of the rock. G: granite; LD: limestone-dolomite. Species points are identified by codes as in Tabìe 2

DISCUSSION

The structure of hard bottom communities has been

traditionally interpreted as mainly the result of com-plex biotic interactions within adult assemblages(Connell 1983, Schoener 1983). Only in the last

decade has the importance of external factors, such asphysical processes and recruitment vagaries, beenful ly recognised (Barry & Dayton 1991, Bingham 7992,

Bianchi 1997, Guichard & Bourget 1998, Smith & Wit-man 1999). However, our knowledge about the role ofthe nature of substratum remains anecdotal. Manygeneral papers on marine ecology report on the influ-

ence of hard substratum surface texture and physico-

chemical properties upon community composition and

structure (Den Hartog 1972, Levinton 1982), but stud-ies providing direct evidence are scarce. Comparing

the epibiotic communities of different types of sub-

stratum, Connell & Glasby (1999) found differences in

the identity of species and the abundance of individ-

ual taxa. The same authors observed that the charac-

teristics of the substratum surface were an importantdeterminant in the structure of assemblages and thatcertain physical or chemical properties (e.9. alkalin-ity) may affect the settlement, growth or survival of

organisms. On the other hand, Caffey (1982) found no

effect of rock types on the settlement or survival of

the intertidal barnacle Tesseropora rosea (Krauss).

Our experiments with the subtidal hydroid Euden-

drium glomeratum suggest that the larvae of benthic

organisms could be selected, other environmental con-

ClnCni

C n t nLD '"

LD HPaMtr LD S/o Ddi

INE Sard in ia ]

Cclt,

* " G

Rhvy udiDdi CcrPtu

Eca tttu ,"" G Ave

Foe Aac G ^ùce _-,,,.' l Ada u^ .r,

,n .L q ^ U a , , ' , C b u^ U u P D a

LD G " ,u, G;l' ?r,pht î^^ 56v Pne

vyo Aab

G

. 4

- . C n i,et

, lL . ì , 1

1 Lfrn,,. Goó" ' "

Pf t IMIi t,.

npaCel

Aor 1VC

Pca4

L

Pfl

AN

L

Ada

I PPa

I utuCgt Atib F p e IPIi L

6 l o r lPax

Goó |oft Pli

lva

He

'Ip la ollarlsa^pg) suipro zupnb a^lossrp pup lrallor ol

alqp sr srurtoluat prsoJpuotD a6uods aurJprrr aq] ssal-ar{uo^aN u^\ou{ lou sr esrlrs alelncrlred Jo soouodsÀq e>1e1dn aql pup uorlnlossrp oql 6ur^,\olle rusru€qJoru

IpJrruar{Jorq aql /alpp o1 salnrrds pue sruolprp paluau-rpas pup slood aq1 Jo ruolloq aql Jo pups cqrzlrenb

aqJ sr oornos ecqrs À1uo oql lplrqpq s1t{l uI 'urpr aarJ-€Jr-1s À1e1e1duroc Àq Àpo pelp; slood re1e.r,t Àrerodruol ur

salncrds IpruJou ecnpord so6uods rolp,^ r{soJJ upr1rzerg:luaruuoJr^uo Iernlpu e ur uoururoJ osle sr uouaurou-aqd srql lpql surplurpur ('ururoc srad) orraqrg-raru{lo^'(7761 uesueOrol) aornos pJrlrs sp ruolloq runrrpnbpaql uo ur op prel soJeJr1rs Jo spurl luara;pp 6ursn

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lsurebe ap^rpl prorpÀq Jo aJror{J 6uor1s p olprlsuouapaurrJ JSrrJ aql roJ plpp rno (7661 rarutuog) suorldacxa

1ou Àlqeqord arr.- urnupuapng p saroads pup (966I

seqbng € IIID) slsrlprauab alprJsqns are sprorpÀq 1so1,1'relncrlred ur zlrenb yo ecueserd aql ,(q pup alprlsqnsaql Jo uorlrsoduroc leraurur aql ^q '1enba 6uraq suorlrp

LVZsarJrunururoJ rrqluaqrda aurJpru ;o 6ur:n1;rn.r15 : lp ]a ollarlsa^eg

248 Mar Ecol Prog Ser 1,93:247-249, 20O0

1995b), probably due to a considerable product ion of

ascorbic acid (Cerrano et a l . 1999).

The results of this study and the above considera-

tions suggest that bio-mineralogy is likely to play a

major role on benthic communities, selecting the biota

and affecting not only the initial colonisation, as seen

in the experiment of Eudendrium settlement, but also

Iater assemblages, as apparent from our field data.

This potentiaÌ role has been largely neglected to date

and further studies are needed to prove its importance.

Acknowledgemenfs. This research was financially supportedby MURST Italian funds. Field activity received support fromENEA. Many thanks are due to all colleagues that helpedduring underwater work.

LITERATURE CITED

Abbiati M, Bianchi CN, Castelli A (1987) Polychaete verticaÌzonation aÌong a littoral cliff in the West Mediterranean.PSZN I : Ma r Eco Ì B (1 ) : 33 -48

Abbiati M, Bianchi CN, Castellì A, Giangrande A, Lardicci C(1991) Distribution of polychaetes on hard substrates ofthe midlittoral-infralittoral transition zone, western Med-i terranean. Ophel ia 5(suppl) :421-432

Alvisi M, Bianchi CN, Colantoni P (1994) Le grotte sommersedel1o Scoglio della Cappa (Isola del Giglio). Mem Ist ItalSpeleoiogia Ser I I 6:25-30

Anderson MJ, Underwood AJ (1994) Effects of substratumon the recruitment and development of an intertidalestuarine fouling assembÌage. J Exp Mar BioÌ Ecol 184:21.7,236

Balduzzi A, Bianchi CN, Cattaneo-Vietti R, Cerrano C, CocitoS, Cotta S, Degl'Innocenti F, Diviacco G, Morgìgni M,Morri C, Pansini M, Salvatori L, Senes L, Sgorbini S,Tunesi L (1994) Primi lineamenti di bionomia benticadell'Isola Gallinaria (Mar Ligure). In: AlberteÌÌi G, Catta-neo-Viet t i R, Piccazzo M (eds) At t i del 10" Congressodell'Associazione Italiana di Oceanologia e Limnologia(AIOL), Genova, p 603-617

Balduzzi A, Bianchi CN, Burlando B, Cattaneo-Vietti R, Man-coni R, Morrl C, Pansini M, Pronzato R, Sarà M 11996)Zoobenthos di substrato duro delle isole di Capraia e delGiglio (Arcipelago Toscano). Atti Soc Toscana Sci NatMem Se r A 102 (Supp Ì ) ( 1995 ) : 124 -135

Barry JP, Dayton PK (1991) Physical heterogeneity and theorganization of marine communities. In: KoÌasa J, PickettSTA (eds) Ecological heterogeneity. Springer Verlag, NewYork, p 270-320

Bavestrello G, Cattaneo-Vietti R, Cerrano C, Danovaro R,Fabrano M (1995a) Annual sedimentation rates and role ofthe resuspension processes along a vertìcal cliff (LigurianSea, I ta ly) . J Coastal Res 11(3):690-696

Bavestrello G, ArilÌo A, Benatti U, Cerrano C, Cattaneo-ViettiR, Cortesogno L, Gaggero L, Giovine M, Tonetti M, SaràM (1995b) Quartz dissolution by the sponge Chondrosiareniformis (Porifera, Demospongiae), Nature 378:374 376

Bianchi CN (1997) Climate change and biological response inthe mar ine benthos. ln: Piccazzo M (ed) At t i del 12' Con-gresso dell'Associazione Italiana di Oceanologia e Lim-noÌogia (AIOL), Vol 1. Genova, p 3-2O

Bianchi CN, Morr i C, Peirano A, Romeo G, Tunesr L (1987)Bibliografia ecotipologica suÌ Mar Ligure. Ente per Ìe

nuove tecnologie, 1'energie e I'ambiente, ColÌana di studiambientali, Roma

Bianchi CN, Coci to S, Morr i C, Sgorbin i S (199i) Ri levamentobionomico subacqueo. In: Abbiati M (ed) Lezionr del corsoformativo per ricercatore scìentifico subacqueo. Interna-tional School for Scientific Diving, Pisa, p 67-83

Bingham BL (1992) Life histories in an eprfaunal community:coupling of adult and larval processes. Ecology 73:2244 2259

Boero F, Balduzzi A, Bavestrello G, Caffa B, Cattaneo Vietti R(1986) Population dynamics oî Eudendrium g)omeratum(Cnidaria, Anthomedusae) on the Portofino Promontory(Ligur ian Sea). Mar Bio l 92:81-85

Boni A, Braga G, Cont i S, Gelat i R, Marchet t ì G, Passer i LD(1969) Note illustrative della carta geologica d'ItaÌia.FogÌio 83, Rapallo. Foglio 94, Chiavari. Servizio Geologicod'Italia, Roma

Cabioc'h J, Floc'h JY, Le Toquin A, Boudouresque CF,Meinesz A, Verlaque M (1992) Guide des algues des mersd'Europe. Delachaux et Niestlé, Neuchàtel

Caffey HM (1982) No effect of naturally-occurring rock typeson settlement or survival in the intertidal barnacle,Tesseropora rosea (Krauss). J Exp Mar Biol Ecol 63:119-1.32

Cattaneo-Vietti R, Sirigu AP, Tommei A (1988) Sea of Liguria,2nd edn. Research Centre of the Union of Ligurian Cham-ber of Commerce, Genoa

Cerrano C, BavestreÌ Ìo G, Cattaneo-Viet t i R (1997) L ightinfluence on planulae emission and settlement in Euden-drium glomerafum fCnidaria, Hydrozoa). Biol Mar Medit4 ( 1 ) : 3 0 3 3

Cerrano C, Arillo A, Bavestrello G, Benatti U, Calcinai B, Cat-taneo-Viet t i R, Cortesogno L, Gaggero L, Giovine M, PuceS, Sarà M (1998) Organism-quartz interactions in structur-ing benthic communities: towards a marine bio-mìneral-ogy? Ecol Let t 2:1-3

Cerrano C, Bavestreilo G, Arillo A, Benatti U, Bonpadre S,Cattaneo-Viet t i R, Gaggero L, Giovine M, Leone L, Luc-chetti G, Sarà M (1999) Calcium oxalate production in themarine sponge Chondrosia reniformis. Mar Ecol Prog Ser179:297-3O0

ConneÌl JH (1983) On the prevalence and relative importanceof interspecific competition: evidence from field experi-ments. Am Nat 122:661 696

Connel l JH, Slayter RO (1977) Mechanisms of succession innatural communities and their roÌe in community stabilityand o rgan i za t i on . Am Na t 111 :1119 1144

Connell SD, Glasby TM (1999) Do urban structures influencelocal abundance and diversity of subtidal epibiota? A casestudy from Sidney Harbour, Australia. Mar Environ Res47:373-387

Den Hartog C (1,572) Substratum. In: Kinne O (ed) MarineEcology, Vol 1, Part 3. Wiley-lnterscience, p 1277-.1289

Fanel l i G, Pira ino S, Belmonte G, Geraci S, Boero F (1994)Human predation aÌong Apulian rocky coasts (SE Italy):desertification caused by Lithophaga lithophaga IMoL-lusca) f isher ies. Mar Ecol Prog Ser 110:1-8

Glli JM, Hughes RG (1995) The ecology of marine benthichydroids. Oceanogr Mar Biol Annu Rev 33:357-426

Guichard F, Bourget E (1998) Topographic heterogeneity,hydrodynamics, and benthic community structure: ascale-dependent cascade. Mar Ecol Prog Ser 177:59-70

Hiscock K (1987) Subtidal rock and shallow sediments usingdiving. In: Baker JM, WoÌff WJ (eds) Biological surveysof estuaries and coasts. Cambridge University Press, Cam-bridge, p 198-237

HoÌm ER, Cannon G, Roberts D, Schmidt AR, Sutherland JP,

Bavestrello et al.: Structuring of marine epibenthic communities 249

Rittschof D (1997) The influence of initial surface chem-istry on development of the fouling community at Beau-fort, North Caroiina. J Exp Mar Biol Ecol 215:lB9-2O3

Johnson CR, Lewis TE, Nichols DS, Degnan BM (1997) Bacte-riaÌ induction of settlement and metamorphosis in marineinvertebrates. In: Lessios HA, Maclntyre IG (eds) proceed-ings of the 8th International Coral Reef Syrnposrum,Smithsonian Tropical Research Institute, panama, 2:7279-1.224

Jorgensen CB (1944) On the spicule-formation of Spongilta,lacusfris (L.). 1. The dependence of the sprcule formationon the content of dissolved and solid silicic acid of themilieu. Det Kgl Dansk Vidensk Selsk Biol Medd 19:2_45

Langer AM, Nolan RP (1986) Physicochemical properties ofquartz controlling biological activity. In: Goldsmith DF,Winn DM, Shy CM (eds) Silica, silicosis, and cancer: con-troversy in occupational medicine. Praeger, New york

Lebart L (1975) Vatidité des résultats en analyse des données.Centre de recherches et de documentation sur la consom-mation, Paris, Lllcd No 4465

Legendre P, Legendre L 11998) Numerical ecology. SecondEnglish edition. Dev Environ Model 20:1 853

Levinton JS (1982) Marine Ecotogy. Prentice-Hall, EnglewoodCliffs, NJ

Lorenzoni GG, Chiesura-Lorenzoni F (1973) Considerazioniconservazionistiche sulle isole di Tavolara, Molara,Molarotto e relativa costa sarda. In: Scalera-Liaci L ledìAtti deÌ III simposio nazionaÌe sulla conservazione dellanatura, Vol 2. Cacucci , Bar i , p 409-435

Marasas LW, Harington JS (1960) Some oxydative andhydroxylative action of quartz: their possible relationshipto the development of silicosis. Nature l8B:I1.73_�t174

McGuiness KA (1989) Effects of some natural and artificialsubstrata on sessile marine organisms at Galeta Reef,Panama. Mar Ecol Prog Ser 52:201,-2O8

Morri C, Bianchi CN, Damiani V, Peirano A, Romeo G, TunesiL (1988) L'ambiente marino tra Punta della Chiappa e Ses-tri Levante (Mar Ligure): profilo ecotipologico e propostadi carta bionomica. Boll Mus Ist Biol Univ Genova 52(Supp l ) : 213 -231

Navone A, Bianchi CN, Orrù P, Ulzega A (1992) Saggio dicartografia geomorfologica e bionomica nel parco marinodi Tavolara-Capo Coda Caval lo. Oebal ia 17(2)(Suppl) :465-478

Orsino F (1975) Flora e vegetazione delle isole Gallinara eBergeggi (Liguria occidentale). Webbia 29:595 644

Pomponi SA (1979) Ultrastructure of celÌs associated with

Editorial responsibility : Otto Kinne (Editor),Oldendorf/Luhe, Germany

excavatÌon of calcium carbonate substrates by boringsponges. J Mar Biol Assoc UK 59:777-784

Russo GF, Cicogna F (1992) Exploitation of the date mussel,Lithophaga lithophaga: problems and prospects. Boll MusIst Bio l Univ Genova 56-57 (1990-1991):184-194

Rútzler R, Rieger G (1973) Sponge burrowing: fine structureoî Cliona lampa penetrating calcareous substrata. MarBro121:144-1,62

Schoener TW (1983) Field experiments on interspecific com-petition. Am Nat 722:24O 285

Shi X, Dalal NS, Vallyathan V (1988) ESR evidence for thehydroxyl radical formation in aqueous suspension ofquartz particles and its possible significance to lipid per-oxidation in silicosis. J Toxicol Environ Healt]n 25:237 245

Sìmboura N, Zenetos A, Thessalou-Legaki M, pancucci MA,Nicolaidou A (1995) Benthic communities of the infra-littoral in the N. Sporades (Aegean Sea): a variety ofbiotopes encountered and anaÌysed. PSZN I: Mar Ecol16 f 4 ) : 283 -306

Smith F, Witman JD (1999) Species diversity in subtidal land-scapes: maintenance by physical processes and larvalrecrui tment. Ecology 80(1):5 1-69

Sommer C (1992) Larval biology and dispersal oî Eudendriumracemosum (Hydrozoa, Eudendriidae). In: Bouillon J,Boero F, Cicogna F, Gili JM, Hughes RG (eds) Aspects ofhydrozoan biology. Sci Mar 56:2O5-21,7

Sousa WP (1984) The role of disturbance in natural commum-t ies. Annu Rev Ecol Syst 15:353-39i

Tortonese E (1958) Bionomia marina della regione costiera fraPunta de11a Chiappa e Portofino (Riviera ligure di levante).Archo Oceanogr L imnol 11(2):167 -2 lO

Tortonese E (1962) Recenti ricerche sul benthos in ambientiIltorali del Mare Ligure. Pubbl Staz Zool Napoli 32(Suppi) :99-11t i

Underwood AJ (1997) Experiments in ecology. CambridgeUniversity Press, Cambridge

Vallyathan V, Shi X, Dalal NS, I W, Castranova V (1988) Gen-eration of free radicals from freshly fractured silica dust:potential role in acute silica-induced lung injury. Am RevRespir Dis 1,38:121,3 -7219

Wahl M (1989) Marine epibiosis. 1. Fouling and antifouling:some basic aspects. Mar Ecol Prog Ser 58:175-189

WaÌters LJ, Wethey DS (1996) Settlement and early post-set-tÌement survivaÌ of sessile marine invertebrates on topo-graphically complex surfaces: the importance of refugedimension and aduÌt morphology. Mar Ecol prog Ser 137:1 .61 - t 71 ,

Submitted: February 26, 1999; Accepted: September 21, lgggProofs received from author(s): February 14, 2000