DIFFERENTIAL EFFECTS OF CORAL REEF HERBIVORES 

 ON ALGAL COMMUNITY STRUCTURE AND FUNCTION 



Robert C. Carpenter 

 Insti tute of Ecol ogy 

 University of Georgia 

 Athens, Georgia 30602 



ABSTRACT 



Fu 

 i n t e n 

 remov 

 algal 

 revea 

 herbi 

 speci 

 forms 

 of pr 

 those 

 algal 

 to su 



n c t i o 

 si ty 

 al , s 



comm 

 led d 

 vores 

 es co 



domi 

 imary 



i n n 



comm 

 bsequ 



nal 



and 



peci 



unit 



iffe 



ran 

 mpos 

 na ti 



pro 

 on-u 

 unit 

 ent 



herbivore groups were categorized according to the 

 frequency of disturbance resulting from feeding. Biomass 

 es composition and primary productivity of experimental 

 ies subjected to herbivory by each functional group 

 rences among groups. Combined removal of biomass by all 

 ged from 32 to 84% of daily algal production. Algal 

 it ion varied according to grazing regime, with crustose 

 ng the most intensely grazed treatments. Specific rates 

 duction of urchin grazed treatments were 2 to 4 times 

 renin grazed treatments. Species composition of reef 

 ies is affected differentially by herbivores, which leads 

 changes in community metabolism. 



INTRODUCTION 



C 

 prod 

 orga 

 free 

 nota 

 alga 

 herb 

 reef 

 Carp 

 comm 

 and 

 such 

 the 

 thei 

 whi c 

 diff 



T 

 the 

 reef 

 desc 



orSl re 

 u c t i o n 

 n i s m s . 

 -living 

 bly i nc 

 1 commu 

 i v o r e s 



algae 

 enter, 

 unities 

 support 



i n t e n s 

 s tructu 

 r m a g n i 

 h such 

 erent g 

 his pap 

 effects 



algal 

 r i p t i o n 



ef communitie 

 that supports 

 The majority 



algal compon 

 onspicuous wh 

 nities such a 

 has been repe 

 (Stephenson a 

 1981 ) . The pr 



invites spec 

 ed by the app 

 e disturbance 

 re of the al g 

 tude and mode 

 removal takes 

 roups of herb 

 er reports so 



of different 

 community str 



of methods a 



s are ch 

 an abun 

 of this 

 ent (Mar 

 en compa 

 s kelp f 

 atedly s 

 nd Sear! 

 edomi nan 

 u 1 a t i o n 

 arently 



( herbi v 



al commu 



of b i o m 



place, 



i v o r e s . 



me p r e 1 i 



f uncti o 



ucture a 



nd resul 



arac 



dant 



prod 



sh , 



red 



ores 



hown 



es , 



ce o 



on h 



spar 



ory) 



nity 



ass 



the 



t e r i z 



and 

 u c t i o 

 1976) 

 to ot 

 ts. I 

 to 1 

 1960; 

 f sue 

 ow su 

 se al 

 may 

 . Bee 

 remov 

 ef f ec 



ed by 

 diver 

 n i s 

 ; how 

 her h 

 ntens 

 i m i t 



Samm 

 h her 

 ch bi 

 gal c 

 have 

 ause 

 al an 

 ts ma 



a hig 

 se ass 

 accomp 

 ever, t 

 i g h 1 y 

 e graz 

 the st 

 arco, e 

 b i v o r e 

 omass 

 ommuni 

 s i g n i f 

 h e r b i v 

 d the 

 y not 



h 1 evel 

 embl age 

 1 i s h e d 

 his com 

 product 

 ing pre 

 a n d i n g 

 t aj_. , 

 s in re 

 can be 

 ty. In 

 i c a n t e 

 ores d i 

 f requen 

 be the 



of primary 



of 

 by the 

 p o n e n t is 

 i v e marine 

 ssure by 

 crop of 

 1974; 

 ef 



achieved 

 addition, 

 ffects on 

 f f e r in 

 cy with 

 same for 



minary results of a study to quantify 

 nal groups of herbivores on shallow 

 nd function. A more detailed 

 ts will be presented elsewhere. 



MATERIALS AND METHODS 



Functional herbivore groups were categorized using two criteria: 

 the size of patch (disturbance) created per feeding bout, and the 

 probability (frequency) of regrazing the same patch on a subsequent 

 feeding bout. The former is mainly dependent on the size of the 

 feeding apparatus and foraging behaviors such as the number of bites 

 in a particular feeding bout. The second criterion depends on the 

 mobility of the organism as well as on behaviors which determine the 

 size of the foraging range (i.e., homing). These groups cross 



113 



