The feeding association between Queen conch, Strombus gigas, and epibiont
!"#$%&'()*+,%--#&&*#&*%./*01213/*T. testudinum beds have declined due to anthropogenic factors including excess nutrients and destruction of suitable habitat
$4#*&(*')5"#%6#$*5(%6&%.*$#7#.(!8#)&*+94-:#6*#&*%./*
011;3*%)$*')5"#%6#$*:48%)*&"%8!.')-*+<5="'5:*%)$*
9(.8>4'6&*01113/
Previous studies on S. gigas have primarily
?(546#$*()*&:#*8'-"%&'()*+9#66#*2;@;A*B&()#"*%)$*
B%)$&*2;;0A*B&()#"*%)$*C%D*2;;E3F*:%G'&%&*46#F*%)$*
biology of S. gigas*+B&()#"*%)$*H%'&#*2;;1A*I%"'6*#&*
%./*011E3/*J:#"#*'6*7#"D*.'&&.#*=)(K)*"#-%"$')-*&:#*
diet of S. gigas* 6!#5'L5%..D* ')* T. testudinum beds.
Daily movement through sea grasses or similar 64G6&"%&#*'6*.'8'&#$*&(*M1N211*8*%*$%D*+9#66#*2;@;3/*
O47#)'.#6*%"#*-#)#"%..D*?(4)$*%&*2NP*8*$#!&:F*K:'.#*
adult S. gigas are usually found between depths (?* PN;* 8* +Q(#""* %)$* 9'..* 011@3/* R$4.&6F* K:'.#*
commonly found in areas with more macroalgae ()*:%"$*64G6&"%&#*+Q(#""*%)$*9'..*011@3F*:%7#*G##)*
?(4)$*%&*$#!&:6*(?*S1NE1*8*()*&:#*"##?*+B&()#"*%)$*
H%'&#* 2;;13/* H:'.#* )(&* !"(7#)F* &:#* 5()5.46'()6*
of these studies suggest an ontogenetic migration which begins in shallow habitats, and ends in deeper :%G'&%&6/* T?* &:#* %)'8%.* 46#6* $'??#"#)&* :%G'&%&6* %&*
different life stages, then it is logical to propose that the dietary composition of S. gigas evolves as the animal migrates.
The importance of feeding by adults on 8%5"(%.-%#N5(7#"#$* :%"$* 64G6&"%&%* :%6* !"#7'(46.D*
been determined through stomach content analysis +B&()#"*%)$*H%'&#*2;;13/*9(K#7#"F*'&*'6*5()7#"6#.D*
argued that organic detritus is a major component of the diet of S. gigas*+9#66#*2;@;A*9%D6*011M3/*T&*
'6*%.6(*!"(!(6#$*GD*.(5%.*L6:#"8%)*%)$*)%&4"%.'6&6*
+!#"6/* 5(88/* U("#8%)F* 93* &:%&* #!'G'()&6* -"(K')-*
on T. testudinum are a major component of S. gigas diet. Both detritus and epiphytic macroalgae are present in T. testudinum G#$6*+9(K%"$*2;VMA*9%D6*
011M3/**
The failure of several S. gigas populations to recover and the further decline of other populations :'-:.'-:&* %* )##$* ?("* '88#$'%&#* %5&'()F* 6!#5'L5%..D*
research that would allow innovative conservation 8#&:($6/* 9%G'&%&* .(66* 5()&"'G4* &(* &:#* ?4"&:#"*
decline in population of S. gigas (Stoner and Ray 2;;EA* 94-:#6* #&* %.* 011;3/* J:#* "#64.&6* ?"(8* &:'6*
study could be used to further support management and conservation plans for both S. gigas and T.
testudinum habitats.
The purpose of this study was to compare epibiont abundance on T. testudinum blades in areas where S. gigas were present to places where they were absent as an assessment of the dietary trends of S. gigas, 6!#5'L5%..D*')*T. testudinum meadows.
Thus, differences in epibiont abundance were used to assess the dietary preferences of S. gigas towards epibionts in the T. testudinum :%G'&%&/* T&*
was hypothesized that S. gigas choose feeding sites
in T. testudinum meadows based on higher epibiont abundances.
Materials and methods
Lac Bay, the area of study, is a Ramsar site on the eastern coast of Bonaire, Dutch Caribbean +W'-/*23/*T&*'6*()#*(?*%*5(..#5&'()*(?*')&#")%&'()%..D*
acclaimed and protected wetlands. Research in the L#.$* (554""#$* $4"')-* &:#* 8()&:6* (?* X5&(G#"* %)$*
Y(7#8G#"*(?*0121F*$4"')-*$%D.'-:&*:(4"6/*
Study sites throughout Lac Bay were selected using GPS coordinates of a previous conch survey performed in the area (pers. comm. Engel, S). Out (?* &:#* ("'-')%.* M2* ZIB* 5(("$')%* "#5#'7#$* 01*
were selected using a random number generator.
At each site a 200 m transect tape was laid out at
%* )("&:* 5(8!%66* :#%$')-/* C#6#%"5:#"6* 6)("=#.#$*
to conduct a visual survey of the area that spanned 0/M*8*()*#%5:*6'$#*(?*&:#*&"%)6#5&/*J:#*%"#%*5(7#"#$*
GD* %* 6')-.#* &"%)6#5&* 64"7#D* K%6* 2111* 82. When an S. gigas* K%6* ?(4)$F* %* M1 58* [* M1* 58* >4%$"%&F*
K:'5:*K%6*$'7'$#$*')&(*&K#)&DNL7#*21*58 [*21*58*
>4%$"%)&6F*K%6*.%'$*()*&:#*G#)&:(6*6(*&:%&*&:#*8'$$.#*
>4%$"%)&*K%6*!.%5#$*(7#"*&:#*%)'8%./*
Four random number generated points for the ')&#"'("* (?* &:#* >4%$"%&* K#"#* 8%"=#$* 46')-* !.%6&'5*
\'!N&'#6/* J:#6#* !(')&6* ')$'5%&#$* K:'5:* 6#%* -"%66*
6%8!.#6*K#"#*&(*G#*&%=#)/*,.%$#6*(?*6#%*-"%66*K#"#*
collected by hand at the closest point to the benthos.
,#)&:'5*64G6&"%&#*5(7#"#$*GD*&:#*>4%$"%&*K%6*)(&#$/*
R..*5(..#5&#$*G.%$#6*(?*-"%66*K#"#*-#)&.D*6:%=#)*&(*
dislodge any loose sediment or other particles and then placed in a gallon sized Ziploc bag which was
=#!&*')*%)*'5#*5:#6&*?("*&"%)6!("&*&(*&:#*.%G("%&("D*?("*
further analysis.
Fig. 1*T8%-#*(?*]%5*,%DF*,()%'"#/*J:'6*'6*&:#*%"#%*
(?*6&4$D**,.%5=*$'%8()$6*"#!"#6#)&*&:#*01*"%)$(8.D*
selected points where transects were laid (Google
<%"&:*01213
57
For comparison, control samples were only
!"#$%& "'!$(& "%& "%)*"+& ,"-& './%01& 2.& .3!")%& !4)-&
5.%!(.+&-"*6+$7&"&89&*&!("%-$5!&,"-&+")0&./!&,)!4&"&
5.*6"--&4$"0)%:&.'&;9!, with the end of the transect touching the 200 m transect where an animal had 3$$%&0)-5.<$($01&24$&"($"&,4$($&!4$&89&*&!("%-$5!&
ended was the closest point to the original 200 m transect from which a control sample was allowed to 3$&!"#$%1&24)-&0)-!"%5$&,"-&0$!$(*)%$0&3"-$0&.%&!4$&
fact that S. gigas&"($&.%+=&#%.,%&!.&!("<$+&"&0)-!"%5$&
.'&>9?@99&*&)%&"&AB&4&6$().0&CD$--$&@;E;F1&24$&89&
m transect was used based on time restrictions, but was the minimum starting distance away from the A99&*&!("%-$5!1&G%5$&!4$&89&*&!("%-$5!&,"-&+")0&./!7&
"%& "($"& .'& @9& *& H& @9& *& ,"-& <)-/"++=& -/(<$=$0& !.&
ensure the area was free of S. gigas. After the area was deemed to be clear of S. gigas7& !4$& I/"0("!&
,"-&6+"5$0&)%&!4$&*)00+$&.'&!4)-&@9&* H&@9&*&"($"1&
J"*6+$-&.'&:("--&,$($&"5I/)($0&'.++.,)%:&!4$&-"*$&
protocol employed to collect blades in the presence of S. gigas1&D.,$<$(7&)'&*.($&!4"%&.%$&"%)*"+&,"-&
0)-5.<$($0&,)!4)%&>&*&.'&$"54&.!4$(&"+.%:&!4$&A99&
*&!("%-$5!&+)%$7&.%+=&.%$&5.%!(.+&-"*6+$&,"-&!"#$%&
"%0& 5.*6"($0& !.& "++& !4$& -"*6+$-& !"#$%& '(.*& !4$&
)%0)<)0/"+&I/"0("!-&.'&S. gigas.
K%& !4$& +"3.("!.(=& '.(5$6-& ,$($& /-$0& !.& 4"%0+$&
the blades of sea grass as to prevent damage to the
$6)3).%!-1&24($$&@&5*&5+)66)%:-&,$($&.3!")%$0&'(.*&
$"54& 3+"0$L& !,.& 3$:)%%)%:& @& 5*& ","=& '(.*& $"54&
end of the blade, and one straddling the midpoint of the blade. Each set of clippings was mounted on the same microscope slide.
Using a compound microscope, each slide ,"-& .3-$(<$0& "!& @9M& "%0& !4$& "3/%0"%5$& .'& 3.!4&
heterotrophic and autotrophic epibionts growth was recorded. Both sides of each slide were observed and the total epibiont abundance was accumulated '.(&$"54&.'&!4$&@A&5+)66)%:-&'(.*&!4$&-"*$&I/"0("!1&
Abundance for both sides of each clipping were all added together so each blade had a total abundance, an autotrophic abundance and a heterotrophic abundance.
The abundance of heterotrophic, autotrophic, and total epibionts were compared between sites where S. gigas was present and absent through /-$&.'&)%0$6$%0$%!&!,.&!")+$0&!?!$-!-1&G%$&!$-!&,"-&
performed for each of three groups: autotrophic epibiont abundance cm?A, heterotrophic epibiont abundance cm?A and total epibiont abundance cm?A.
Results
Throughout the total 20 000 m2&"($"&-/(<$=$07&@;&S.
gigas were found. Eighteen seagrass samples were
!"#$%&'(.*&"($"-&0)($5!+=&-/((./%0)%:&S. gigas (study -)!$-F&"%0&@@&-"*6+$-&,$($&!"#$%&'(.*&"($"-&,$($&S.
gigas were absent (control sites). The inconsistencies in number of samples can be explained due to one individual found in the sand, and thus no seagrass
3+"0$-&5./+0&3$&!"#$%1&D.,$<$(&"&5.%!(.+&,"-&-!)++&
.3!")%$01&K%&"%.!4$(&5"-$7&"%&S. gigas was found in a small patch of seagrass surrounded by sand and thus no control was obtained. Also, in several cases, multiple S. gigas&,$($&'./%0&)%&!4$&-"*$&>&*&+$%:!4&
of the transect tape, so only one control site sample was obtained to compared to these individuals.
The heterotrophic, autotrophic, and total epibiont abundance cm?A was compared between the areas where S. gigas were present and where S. gigas ,$($&"3-$%!1&24$($&,"-&%.&-):%)N5"%!&0)''$($%5$&)%&
the mean total abundance cm?A& C!O@188E7& %O8@P7&
6O91@QA7& R):1& A"F& .(& *$"%& "/!.!(.64)5& "3/%0"%5$&
cm?A& C!O?9199>7& %O8@P7& 6O91;;P7& R):1& A3F& 3$!,$$%&
sites where S. gigas was present and where S.
gigas&,$($&"3-$%!1&D.,$<$(7&!4$($&,$($&-):%)N5"%!&
differences in mean heterotrophic epibiont abundance cm?A&C!O@1;Q7&%O8@P7&6O919B;7&R):1&A5F7&
with the higher mean abundance in areas where S.
gigas was present.
Discussion
This study compared epibiont abundance on T.
testudinum blades in sites where S. gigas are present to sites where individuals are absent in order to assess the dietary trends of S. gigas in T. testudinum
*$"0.,-1& 24$($& ,"-& %.& -):%)N5"%!& 0)''$($%5$&
between mean autotrophic epibiont abundance .(& *$"%& !.!"+& $6)3).%!& "3/%0"%5$1& D.,$<$(7&
"& -):%)N5"%!& 0)''$($%5$& .'& *$"%& 4$!$(.!(.64)5&
58
Fig.2&S.*6"()-.%-&.'&T$"%&CU&JVF&"3/%0"%5$&5*?@&
of a) Total epibionts b) Autotrophic epibionts and 5F&D$!$(.!(.64)5&$6)3).%!-&3$!,$$%&Strombus gigas present study sites and S. gigas absent control sites.
J):%)N5"%5$&"!&919>W7&%-&0$-):%"!$-&%.&-):%)N5"%5$
0 50 100 150 200 250
Present Absent
Mean Abundance of Total Epibiont ± SD (cm^-2)
0 50 100 150 200 250
Present Absent
Mean Abundance of Autotrophic Epibionts ± SD (cm^-2)
0 50 100 150 200 250
Present Absent
Mean Abundance of Heterotrophic Epibionts ± SD (cm^-2)
a)
b)
c)
ns
ns
W
abundance between sites was discovered .
!"# $%# &'()*+,# "-*# *.+("# /$*"+,0# 1+2*# &3# 45# S.
gigas in T. testudinum meadows, yet the results support the hypothesis that S. gigas choose feeding sites in T. testudinum meadows based on higher epibiont abundances. These results also support
"-*#6'/$'7%#45#8"4'*,#*"#+)9#:;;<#+'/#=+77*""#*"#+)9#
>?:?9#@-*%*#%"&/$*%#3,434%*/#"-+"#7,+A$'7#*55*("%#45#
S. gigas# -+B*# +# %$7'$6(+'"# *55*("# 4'# T. testudinum epibiont community structure. That is to say that S. gigas choose areas to feed in T. testudinum meadows which have higher abundances of heterotrophic epibionts, and as a result, S. gigas may -+B*#+#%$7'$6(+'"#*55*("#4'#"-*#*3$C$4'"#(411&'$"0#
structure of T. testudinum.
Stomach content analysis may be the most accurate practice to assess dietary composition, and D+%#&%*/#C0#8"4'*,#+'/#8+'/"#$'#:;;>#"4#/*"*,1$'*#
that macroalgae is the dominant dietary component 45#)+,7*#+/&)"%#$'#/**3#,**5#-+C$"+"%9#E4D*B*,F#1+'0#
$'/$B$/&+)%#D4&)/#-+B*#"4#C*#%+(,$6(*/#$'#4,/*,#"4#
gain the data needed to determine the exact dietary 1+2*# &3# 45# S. gigas in the different habitats it is found in. Current population trends would not be +C)*#"4#D$"-%"+'/#5&,"-*,#/*()$'*#GH4%+/+#*"#+)9#>??IJ#
Paris et al. 2008) so it would be best to postpone stomach content analysis until the population begins to increase.
!'# 4,/*,# "4# 3,4"*("# S. gigas and reverse the declining population trends currently observed G8"4'*,#+'/#K+0#:;;LJ#H4%+/+#*"#+)9#>??IJ#H+,$%#*"#
al. 2008), efforts need to include an understanding of migration, habitat use, breeding and feeding behaviors. The results from this study suggest that heterotrophic epibionts living on T. testudinum may play a role as a dietary component to juveniles found in T. testudinum meadows. Since T. testudinum areas +,*#+)%4#%&55*,$'7#-+C$"+"#)4%%#+'/#/*%",&("$4'#GM(2,$(-#
+'/#E4)1N&$%"#>???O#%3*($+)#*13-+%$%#'**/%#"4#C*#
placed in setting aside T. testudinum meadows in the conservation plans of S. gigas9#!"#$%#+)%4#34%%$C)*#
that by conserving S. gigas populations, that their possible consumption on epibionts may in turn lead to higher rates of photosynthesis in T. testudinum +'/# -$7-*,# C$4/$B*,%$"0# 45# *3$C$4'"%# GE+0%# >??<J#
P4,)*""#+'/#Q4'*%#>??IOF#"-&%#(4'",$C&"$'7#"4#-$7-*,#
productivity of T. testudinum.
Acknowledgements
83*($+)# "-+'2%# "4# R,9# S+,$+# P9# T0+,,+# 54,# */$"$'7#
this manuscript and providing guidance throughout the research period, Daniel Sternberg and Paul H+"$"%+%#54,#"-*$,#-*)3#$'#(4))*("$'7#/+"+F#8@!UVHV#
for allowing this research to be conducted within the
=4'+$,*#1+,$'*#3+,2F#+'/#"4#P!MM#,*%*+,(-#%"+"$4'#
Bonaire Faculty for extensive logistical support throughout the research process.
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=+77*""#WHF#E*(2#Q,#XWF#Y,+'24B$(-#@VF#V,1$"+7*#
VKF# Y4&,N&,*+'# QZ# G>?:?O# U&",$*'"#
enrichment, grazer identity and their effects on
*3$3-0"$(#+)7+)#+%%*1C)+7*%[#6*)/#*.3*,$1*'"%#
in subtropical turtle grass Thalassia testudinum 1*+/4D%9#S+,#M(4)#H,47#8*,#\?L[]]^\<
P4,)*""#EF#Q4'*%#=#G>??IO#M3$3-0"*#(411&'$"$*%#4'#
Thalassia testudinum from Grand Cayman,
=,$"$%-# Z*%"# !'/$*%[# @-*$,# (4134%$"$4'F#
structure and contribution to lagoonal
%*/$1*'"%9#8*/$1*'"+,0#_*4)#:;\[>\<^>L>
R4*,,#QPF#E$))#KW#G>??`O#V#3,*)$1$'+,0#+'+)0%$%#45#
habitat use, movement and migration patterns of Queen conch, Strombus gigas, in St. John, T8a!F# &%$'7# +(4&%"$(# "+77$'7# "*(-'$N&*%9#
H,4(**/$'7%# 45# "-*# L?th Gulf and Caribbean Y$%-*,$*%# !'%"$"&"*F# UbVV# Y$%-*,$*%# 8*,B$(*F#
Southeast Fisheries Science Center, Galveston W+C4,+"4,0F#_+)B*%"4'F#33#<?;^<:<
M(2,$(-# PMF# E4)1N&$%"# Q_# G>???O# @,+13)$'7# $'# +#
seagrass assemblage: direct effects, response of associated fauna, and the role of substrate (-+,+("*,$%"$(%9#S+,#M(4)#H,47#8*,#>?:[:;;^>?;
E+,)$'F# SS# G:;I<O# M3$3-0"*%^-4%"# ,*)+"$4'%# $'#
%*+7,+%%#(411&'$"$*%9#VN&+"#=4"#:[:><^:]:
E+0%# P_# G>??<O# M55*("# 45# '&",$*'"# +B+$)+C$)$"0F#
grazer assemblage and seagrass source population on the interaction between Thalassia testudinum (Turtle grass) and it’s +)7+)#*3$3-0"*%9#Q#M.3#S+,#=$4)#M(4)#]:\[<]^L`
E*%%*# Xb# G:;I;O# S4B*1*'"# +'/# 1$7,+"$4'# 45# "-*#
Queen conch, Strombus gigas#$'#"-*#@&,2%#+'/#
P+$(4%#!%)+'/%9#=&))#S+,#8($#>;[]?]^]::
E4D+,/# KX# G:;`<O# S*+%&,*1*'"%# 45# %-4,"^"*,1#
turnover of epifauna within seagrass beds using an insitu staining method. Mar Ecol Prog Ser
>>[:L]^:L`
E&7-*%#VKF#Z$))$+1%#8WF#R&+,"*#PSF#E*(2#Q,#XWF#
Z+0(4""# S# G>??;O# V%%4($+"$4'%# 45# (4'(*,'[#
declining seagrasses and threatened dependent
%3*($*%9#Y,4'"#M(4)#M'B$,4'#I[>\>^>\L
E&1+''# HVF# R*)4+(-# UM# G>??]O# K**5# (4,+)#
$/*'"$6(+"$4'[# Y)4,$/+F# P+,$CC*+'F# =+-+1+%9#
U*D#Z4,)/#H&C)$(+"$4'%#!'(F#YW
H+,$%#P=F#V)/+'+^V,+'/+#RF#H*,*A#H*,*A#SF#X44)#Q#
(2008) Connectivity of the Queen conch, Strombus gigas, populations from Mexico.
H,4(**/$'7%# 5,41# "-*# ::th# !'"*,'+"$4'+)# P4,+)#
80134%$&1#Y"9#W+&/*,/+)*F#YWF#33#\];^\\]
H4%+/+#QSF#8"4'*,#VZF#8&))$B+'#8*+)*0#XF#V'"(A+2#
VF#8(-+3$,+#RF#@4,,*%#KF#S4'"+'4#!F#K+0#P&)3#
SF#V)/+'+#V,+'/+#R#G>??IO#K*7$4'+)#$'$"$+"$B*#
for the evaluation of Queen conch (Strombus gigas) exploitation under an historical 3*,%3*("$B*9# H,4(**/$'7%# 45# "-*# <Ith Gulf and P+,$CC*+'#Y$%-*,$*%#!'%"$"&"*F#UbVV#Y$%-*,$*%#
Service, Southeast Fisheries Science Center,
59
!"#$%&'()*+",(-"'(-./*00*12345*
6-'7*89/*:")*;()'<-")&*9*=>?@2A*B0C07.'%&3*&%"D-"&&*
relationships with emphasis on the role of ECF-(D-"GC)DH*"*-%$C%IJ*KLM"'*N('J>@H*243O?
8(&%*PQ/*Q"I%&*P9*=>???A*B<<%F'&*(<*F(EEM)C'.*
structure on the seagrass Thalassia testudinum.
;"-*BF(#*R-(D*S%-J*>@2H*@43?T
SF7"0C-"* Q/* ;()'")(* UK/* K)'FG"V* K/* R(&"W"* 9;*
=155?A* X&C)D* &7%##* ECWW%)&* '(* "&&%&&* %<<%F'&*
(<* Y&7C)D* ()* ZM%%)* F()F7* =Strombus gigas) 0(0M#"'C()&* C)* +(&* 8(LM%&* K-F7C0%#"D(*
["'C()"#* R"-V/* :%)%GM%#"J* ;"-* NC(#* >TOH\@\3
\?T
S'()%-*K]/*8".*;*=>??OA*ZM%%)*F()F7/*Strombus gigas/* C)* Y&7%W* ")W* M)Y&7%W* #(F"'C()&* (<* '7%*
N"7"E"&H* %<<%F'&* (<* "* E"-C)%* Y&7%-.* -%&%-$%*
on adults, juveniles, and larval production. Fish NM##*?2HTT>3TOT
S'()%-* K]/* 8".* ;/* ]"C'%* 9;* =>??TA* B<<%F'&* (<
a large herbivorous gastropod on macrofauna communities in tropical seagrass meadows.
;"-*BF(#*R-(D*S%-J*>1>H>1T3>4\
S'()%-*K]/* S")W'* :9* =>??1A* R(0M#"'C()* &'-MF'M-%/*
seasonal movements and feeding of Queen conch, Strombus gigas/* C)* W%%03I"'%-* 7",C'"'&*
(<*'7%*N"7"E"&J*NM##*;"-*SFCJ*T>H1@\3455 S'()%-* K]/* ]"C'%* 9;* =>??5A* QC&'-C,M'C()* ")W*
behavior of Queen conch Strombus gigas relative to seagrass standing crop. Fish Bull
@@HT\43T@T