manthe 1987 aquacultural-engineering

7/28/2019 Manthe 1987 Aquacultural-Engineering

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Aquacu ltural Engineering 6 (1987) 227-236

C h e m i c a l A d d i t io n f o r A c c e l e r a t e d B i o l o g i c a l F i lt e rA c c l i m a t i o n in C l o s e d B l u e C r ab S h e d d i n g S y s t e m s

D on P. M anthe and Ro nald F. M aloneDepartment of C ivil Engineering, Louisiana State University, Ba ton Rouge, Lou isiana70803, USA

A B S T R A C THeavy load ing o f comm erc ia l crab shedding sys tems i s a m ajor prob lemat the beginning o f the softshell crab season if the biological filters are notproperly accl imated. Thus m etho ds that can be use d to accelerate f i l teracclimation b7 a co m m erc ial setting are desirable. Exp erim en tal sheddingsystems with subm erged ro ck f il ters im pacte d by me dia size , com me rcialadditives containing nitrifying bac teria, an d che m ical addition wereexam ined. Filters acc lima ted with crabs took 3 5 days to adjust to base linewater quality conditions. Th e filters d em ons trated the ability to beincreased to fu l l design loading i f accl imated with 25% o f the sheddingsystem d esign . Filter m edia size and addition o f concentrated nitrifyingbacteria d id no t have any significant effect on acclimation tim e o f thenitrif ication beds. Ad dit io n of amrnonia to simu late loading acclimated abiological filter w ithou t the use of animals, but did n ot shorten the accli-ma tion t ime. The mo st prom ising avenue o f research is the addit ion o fammonia and ni tri te in combination to st imulate growth in both specieso f nitrifying bacteria simultaneously. Nitrite addition during startup o f abiological filter redu ced the acclimation pe rio d by 10 days (or 28%).

I N T R O D U C T I O NL o u i s i a n a ( U S A ) r e m a i n s t h e l a r g e s t s u p p l i e r o f s o f t c r a b s t o t h e G u l fs ta te s , b u t r e p o r t e d l a n d i n g s h a v e f l u c tu a t e d w i d e ly . T h e p r o d u c t i o nd r o p i n r e c e n t y e a r s h a s b e e n a t t ri b u t e d t o a n u m b e r o f f a c to r s , in c l u d i n ga dec l i ne i n coas t a l w a t e r qua l i t y , l o s s o f na t u ra l hab i t a t , and d i s e a s ei J aw orsk i , 1971 ; Pe r ry et a l . , 1 9 8 2 ) . T h e f i s h e r y ' s r e g r o w t h a n d e x p a n -s i on i s now be i ng s t i m u l a t ed by t he adop t i on o f c l o sed , r ec i r cu l a t i ngs e a w a t e r s y s t e m s to h o l d a n d s h e d pee l e r c rabs .T h e p o t e n t i a l v a l u e o f u s i n g c l o s e d s y s t e m s f o r s h e d d i n g c r a b s h a sb e e n d e m o n s t r a t e d b y a n u m b e r o f c o m m e r c i a l o p e r a t o r s ( P e rr y et a l . ,227Aquacultural Engineering 0144-8609/87/S03.50-- Elsev ier Ap plied SciencePublishers Ltd. E ngland, 1987. Printed in G reat Britain


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228 D. P . Man the , R . F . M a lon e1 9 8 2 ; M a n t h e e t a l . , 1983) . T he op e ra t ion o f a succes sfu l c losed r ec i r cu -l a ti n g a q u a c u l t u r e s y s t e m d e p e n d s p r i m a r i l y o n m a i n t a i n i n g a c c e p t a b l ew a te r qua l i ty . T h e b io log ica l f i l te r ' s ab i li t y i n c losed sys t ems to conv e r ta m m o n i a (N H 3) , t h e p r i n c i p a l n i t r o g e n o u s e x c r e t o r y m e t a b o l i te o f C r u s -t acea (Ha r t ens t e in , 1970) , t o t he r e l a t ive ly no n tox ic n i t r a t e (NO3) b yb a c t e r i a l n i t r if i c a ti o n is s u m m a r i z e d b y W h e a t o n ( 1 9 7 7 ) a n d S p o t t e(1979) . In c r ab shed d ing sys t ems , n i tr i t e has bee n iden t i f ied as t he m os tt o x ic f o r m o f n i tr o g e n t o c r a b s. C o n c e n t r a t i o n s o f a p p r o x i m a t e l y 2 0 m gl it e r- ~ N O 2 - N a n d a b o v e h a v e b e e n f o u n d t o c a u s e s e v er e m o r t a l it y i ni n t e r m o l t c ra b s . M o r t a l i ty in m o l t in g c r ab s w a s o b s e r v e d a t c o n c e n t r a -t ions as low as 2 mg l i te r -1 NO2_N. Increases" in the n i t r i t e (NO2) con-cen t r a t i ons r e su l t ing f rom the co nv e r s io n o f c r ab w as t es i s t he l imi t ingwa te r qua l i t y pa r am e te r i n t hese sys t ems w here t he b io log ica l f il te r s a r en o t a c c l i m a t e d t o h i g h l o a d in g s ( M a n t h e e t a L , 1984) .D u e t o t h e s e a s o n a l u s e o f t h e c r a b s h e d d i n g s y st e m s ( n o r m a l l y M a yth ro ug h O c tobe r ) , t he b io log ica l f i lt e r s m us t be ac c l ima ted a t the s t a r t o feve ry so f t she l l c r ab season . T rad i t i ona l ly , subm erged b io log ica l f i lt e ra c c l i m a t i o n f o r a q u a c u l t u r e s y s te m s t a k e s f ro m 3 0 t o o v e r 1 0 0 d a y s( H i ra y a m a , 1 9 7 4 ; M e v e l a n d C h a m r o u x , 1 9 8 1 ; M a n t h e e t a l . , 1984) . F i l -t e r s t a r tup usua l ly cons i s t s o f i n t roduc ing in t e rmol t c r abs o r e s tua r inef i sh t o bu i ld up a su f f i c i en t f i l t e r bac t e r i a popu la t ion tha t w i l l accep tpee l e r c r ab load ing to p ro du ce so f tshe l ls . U nfo r tun a t e ly , t h is f il t e r p re -p a r a t i o n m e t h o d o f t e n c o r r e s p o n d s w i th th e s p r in g r u n o f p r e m o l t cr a bs .T he sp r ing run causes t he l a rgest i n f lux o f pee l e r c r abs du r ing the seasona n d c o n s e q u e n t l y is t h e m o s t p r o f i t a b l e ti m e o f t h e y e a r t o t h e s o ft s he l lp r o d u c e r . I f t h e s y s t e m s a r e n o t p r o p e r l y a c c l i m a t e d t o a c c e p t h e a v yc rab load ings , sys t em fa i lu re and pee l e r c r ab m or t a l i ti e s can r e su l t f romdec l in ing w a te r qua l i ty . Th us m e tho ds to de c rease b io log ica l f i lt e r acc l i-m a t i o n t i m e d u r i n g t h i s c r u c i a l p e r i o d s h o u l d i n c r e a s e p r o d u c t i v i t y a sw e l l a s r e v e n u e s a n d p r o v i d e s a fe o p e r a t i o n o f s h e d d i n g s y st em s d u r i n gh e a v y c r a b l o a di n g s.T h i s p a p e r e x a m i n e s f i l t e r a c c l i m a t i o n r e s p o n s e s o f s e v e r a l c r a bs h e d d i n g s y s te m s i m p a c t e d b y d i f f e r e n t m e d i a s i ze a n d c o m m e r c i a l a d d i -t ives con ta in ing n i t r ify ing bac t e r i a , an d iden t if i e s chem ica l add i t i onm e t h o d s t h a t c o u l d b e u s e d t o a c c e l e r at e f il te r a c c l i m a t i o n i n a c o m m e r -cial set t ing.

M A T E R IA L S A N D M E T H O D SSix expe r imen ta l sys t ems were cons t ruc t ed on a 3% sca l e o f succes s fu lc o m m e r c ia l s y st em s d e s c r ib e d a n d m o n i t o r e d b y M a n t h e e t a l . (1983) .


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Bi o l o g i c a l f i l te r a c c f i m a t i o n i n b l u e c r a b s h e d d i n g s y s t e m s 2 2 9E x p e r i m e n t a l t a n k s w e r e m a d e o f p le x ig l as s a n d a ll p l u m b i n g w a s o fp o l y v i n y lc h l o r id e ( P V C ) a n d s im i l a r t o p r e v io u s e x p e r i m e n t a l w o r k( M a n t h e e t a l . , 1 9 8 4 ) . D i m e n s i o n s a n d a s c h e m a t i c o f t h e e x p e r im e n t a ls y s t e m s a r e p r e s e n t e d i n T a b l e 1 a n d F i g . 1 , r e s p ec t iv e l y . T o t a l sy s t e mv o l u m e w a s 2 2 5 l ite r s w it h a m a x i m u m l o a d in g c a p a c i t y o f 2 0 c r a b s .U p p e r t a n k w a t e r l e v e l s w e r e c o n t r o l l e d b y a 5 i n c h ( 1 2 . 7 c m ) s t a n d -p i p e c o n s t r u c t e d o f 1 .5 i n c h ( 3" 8 c m ) P V C p i p e w i th g r a v i ty f e e d t o t h e

T A B L E 1D i m e n s i o n s o f E x p e r i m e n t a l S y s t e m s

D e s cr ip ti on L e n g t h W i d th D e p t h W a t e r A r e a V o l u m e(fi) (ft) (ft) de pt h (fi e) (f t9( f i )

C r a b t a n k 3 2 1 0 . 8 3 8 6 2 - 6 2 5B i o l o g i c a l f i l t e r t a n k 1 " 1 6 7 1 1 .5 1 1 . 1 6 7 1 . 1 6 7M e c h a n i c a l f i l t r a t io n b e d " 1 " 16 7 0 "5 0 -5 - - 0 - 5 8 4 0 " 2 9 2L i m e s t o n e f i l te r b e d " 1 " 16 7 1 0 -5 - - 1 . 1 6 7 0 . 5 8 4S u m p 3 2 1 0 - 7 0 8 3 6 4 . 2 5N o t e : 1 f o o t = 0 . 3 0 4 8 m" S u b c o m p a r t m e n t o f b i o l o g i c al fi l t e r t a nk .

~ , 2 ' - i~ . ~ CRAB TANK II I I - ' 7 , ' - z C - - ~ - "

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! I N t - s -F i g . 1 . C o n f i g u r a t i o n o f e x p e r i m e n t a l u n i t s . ( 1 ' = 3 0 . 4 8 c m ; 1 " = 2 ' 5 4 c m ) .


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2 3 0 D. P. Manthe, R. F. Maloneb io log ica l f il te r . T he d i scha rge no zz l e i n to t he u pp e r t a nk cons i s t ed o f acap ped 0"5 inch (1.3 cm) PVC p ipe w i th two 0 . 125 inch (0 .3 cm) ho le s toas su re ac t ive ag i t a t i on ( ae ra t ion ) i n t he t ank . Crabs were p l aced o n thec l ea n t a n k b o t to m .T h e s u b m e r g e d d o w n f l o w b i o l o g ic a l f i lt e r w a s s u p p o r t e d b y 0 .5 i n c h(1"3 cm) egg -cra te louv er ing ra i sed 2 inch es (5 .1 cm) f rom the f i l te r t ankb o t t o m . D o l o m i t ic l i m e s t o n e w a s c h o s e n a s t h e s in g le m e d i a c o m p o n e n tdue to i t s ava i l ab i li t y and bu f fe r ing capac ity . Th i s subs t r a t e has p rov eni t s e l f i n c o m m e r c i a l o p e r a t i o n s a n d i s r e a d i l y a v a i l a b l e . T h r e e m e d i as izes were u sed in t he s ix sys tems . Sys tems 1 and 6 used l imes tone in the2 - 5 m m s iz e, s y s te m s 2 a n d 5 u s e d 5 - 1 0 m m s i ze a n d s y s te m s 3 a n d 4u s e d m e d i a i n t h e 1 3 - 2 0 m m s i z e . E a c h r o c k b e d w a s 6 i n c h e s ( 1 5 - 2 4c m ) d e e p i n c l u d in g a 1 in c h ( 2. 54 c m ) s u p p o r t b e d o f n o. 6 7 c o m m e r c i a lg r a d e l i m e s t o n e s o t h e s m a l l e r m e d i a w o u l d n o t f a ll t h r o u g h t h e l o u v e r -ing . Mechan ica l f i l t r a t i on boxes f i l l ed wi th aqua r ium f los s were p l acedb e f o r e t h e b i o l o g i c a l f il te r s to a c c o m m o d a t e p r e - f il t ra t i o n o f s u s p e n d e dsol ids .W ate r f low ed by g rav i ty f rom the b io log ica l fi l te r t o t he sum p w hiche v o l v e d i n t h e c o m m e r c i a l sy s te m s t o b u f f e r r a p i d w a t e r q u a l i ty c h a n g es .A 0 . 0 5 h o r s e p o w e r c h e m i c a l s o l u t i o n p u m p ( T e e l , m o d e l n u m b e r1P677) c i r cu l a t ed the f i l te r ed w a te r t h rou gh a ~ inch (1 .6 cm) f l ex ib lep l a s t ic tub ing to t he up pe r t ank ' s sp ray n ozz l e a t a ra t e o f 6 l i te r s m in - tS y s te m w a t e r w a s 1 0 0 % r e c i rc u l a t e d w i th w a t e r a d d i t i o n o n l y f o r e v a -p o r a t i o n a n d s a m p l e l os s.A l l c r a b s u s e d i n t h e s t u d y w e r e i n t e r m o l t ra n g i n g in s iz e a n d w e i gh tf rom 10 to 15 cm ac ros s t he ca rapace ( t op she l l) and f ro m 100 to 150 g ,r e spec t ive ly . Fo l lowing loca l commerc i a l p rac t i ce , c r abs i n t he expe r i -m e n t a l s y s te m s w e r e n o t f e d . M o r t a l it i e s w e r e r e m o v e d c o n t i n u a l l y a n dpop u la t ion s r e s to re d to co ns t an t l eve l s on ce a day . Pe r iod ica l ly , t hee n t i r e c r a b p o p u l a t i o n w a s r e p l a c e d t o p r e v e n t a n i m a l w e a k e n i n g b ys t a rva t ion .T e c h n i q u e s a n d i n s t r u m e n t a t i o n t o m e a s u r e t h e d i s cu s s e d w a t e rqua l i t y pa ra m e te r s a r e l i s ted in Tab le 2 . A l l sys t ems were m on i to red fo rt em pera tu re , s a li n it y , d i s so lved oxyg en (DO) , am m onia , n i t ri t e , and pHe v e r y d a y . D e t e r m i n a t i o n s o f a l k a l in i t y l ev e ls a n d n i t ra t e c o n c e n t r a t i o n sw e r e u n d e r t a k e n o n a w e e k l y ba s is . R o u t i n e l y a 1 li te r sa m p l e o f w a t e rw a s t a k e n f r o m t h e s u m p o f e a c h o f t h e e x p e r i m e n t a l s y s t e m s a n da n a l y z e d i m m e d i a t e l y f o r t h e l a b o r a t o r y d e t e r m i n a t i o n s , p H r a n g e df r o m 7 t o 8 . D O c o n c e n t r a t i o n w e r e m a i n t a i n e d a b o v e 6 m g l i t e r - 1 i n t h ecrab tank and above 4 mg l i te r -~ ex i t ing the f i l t e r , respec t ive ly . Sa l in i tyw a s r e g u la t e d a t 4 % 0 a n d t e m p e r a t u r e r e m a i n e d a t 1 8 + 1C.


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Biological f i lt er acc l imat ion in b lue crab shedd ing sys temsTABLE 2Measurements Taken and Techniques

231

Param eter Ins t rum ent or t es t Re ferenceTotal ammonia as Orion 95-10 Ammonia Electrode/ APHA (1980)NH3-N Orion 701 A Digital lonalyzerNitrite as NO,-N Bausch and Lomb Spectronic 20,Spectrophotometer

Oxygen as O,SalinitypH

Yellow Springs Instrument Co.Dissolved Oxygen Meter, Model 51American Optical RefractometerMini (Model 47) pH meter

Sulfanilamide-basedcoiorimetricreaction, APHA(1980)

R E S U L T SF i l te r m e d i a s i z e

F i g u r e 2 s h o w s t h e a m m o n i a a n d n i t ri te c o n c e n t r a t i o n s f o r sy s te m s 1 - 3d u r i n g t h e s t ud y . E a c h s y s te m w a s s t a r t e d u p w i t h a c o n s t a n t p o p u l a t i o nof fi ve c r abs . F igu re 2 de m on s t r a t e s t he c l a ss i ca l s t a r tup cu rves expec t edi n t h e se s y st em s . A s t h e c r a b s e x c r e te d a m m o n i a ( th e i r p r i m a r y n i t ro g e nm e t a b o l it e ), c o n c e n t r a t i o n s i n c r e a s e d i n t h e s y st em s . A c c o r d i n g t o c o n -ven t iona l t heo ry , as N i t r o s o m o n a s sp. pop u la t ion s i nc reased in t he f i lt e ra n d c o n s u m e d a m m o n i a , c o n c e n t r a t i o n s o f a m m o n i a d e c r e a s e d a n dn i t r it e i nc reased . Syst ems 1 -3 expe r i enced up to 60 % d a i ly m or t a l i t yd u r i n g t h e p e a k n i t ri t e c o n c e n t r a t i o n s ( w h i ch o c c u r r e d b e t w e e n d a y 1 6and day 36). T h i s was a r e su l t o f t he acu te t ox i c it y o f n i t r it e leve ls above2 0 m g l it e r -~ a s p r e v i o u s l y d e s c r i b e d b y M a n t h e e t a l . (1984) . N i t r o -b a c t e r sp. t hen bec am e es t ab l i shed and b egan co nve r t i ng n i t r i te t o t hem uch l es s t ox i c n i t ra t e . B io log ica l f i l te r acc l ima t ion in each sys t em to ok37 days fo r t he f i ve c r ab load ing be fo re t he sys t em s t ab il ized wi th n i t ri t ec o n c e n t r a t i o n s b e l o w 1 m g l i t e r - J

O n d a y 4 3 , s y st e m s 1 - 3 p o p u l a t i o n s w e r e i n c r ea s e d t o 1 0 c r ab s .M i n o r t r a n s i t o r y i n c r e a s e s i n a m m o n i a a n d n i t r i t e r e s u l t e d , b u tq u i c k ly r e t u r n e d t o b a s e l i n e c o n d i t i o n s . O n d a y 5 3 , e a c h s y s te m ' s p o p u -l a t i on was inc reased to 20 c rabs . Ag a in the syst ems r e sp ond ed we l l, w i thon ly m inor i nc reases i n am m on ia and n i t r it e leve ls . As F ig. 2 shows , thesec on da ry t rans itory , peak s inc rease s l igh t ly as the m edia s ize increases .


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232 D. P. Manthe, R. F. Malone

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2 4 S y s t e m 3211 8 ; . , , . . /%1 5 r J " "i Z , , ' , . . ;9 "~ L i m e s t o n e60 " ~ - = " " l I k ' . . . . . . . . . . . ~ ~ " ~ , i '0 4 8 1 2 1 6 2 0 2 4 2 8 3 2 3 6 4 0 4 4 4 8 5 2 5 6

T I M E I N D A Y SFilter acc limationcurves of systems 1-3 using hree different m edia sizes.

B a c t e r ia l a n d c h e m i c a l a d d i t i o nSys t em 4 (F i g . 3 ) w as i n i t ia t ed on da y 12 w i t h the add i t i on o f 250 m l o fc o m m e r c i a l l y a v a i la b l e c o n c e n t r a t e d n i tr if y i n g b a c t e r i a ( M i c r o b e M a s t e rb rand) , w h i ch i s t yp i ca l l y u sed i n indus t r i a l w a s t ew a t e r p l an t s t o a l l ev ia t esho ck l oad i ngs and m ee t d i scha rge r egu l a ti ons . O n d ay 13, f ive c rabsw e r e a d d e d t o t h e sy s te m . T h e c l as s ic a l s t a r tu p c u r v e o c c u r r e d a n d t h es y s t e m r e a c h e d s t a b l e c o n d i t i o n s i n 3 6 d a y s . N o m a r k e d d e c r e a s e i ns t a r t up t i m e w as obse rved us i ng t he i nocu l a t i ng bac t e r i a . Load i ng w asi n c r e a s e d t o 2 0 c r a b s o n d a y 5 3 , w i t h t h e c o r r e s p o n d i n g t r a n s i to r yi n c r e a s e i n a m m o n i a a n d n i t r i t e c o n c e n t r a t i o n s . H o w e v e r , t h e s ei nc reases w ere sm a l l , dem on s t ra t i ng t he sys t em w as w e l l acc l i m a t ed .Sys t em 5 (F i g. 3) s t a r t up began w i t h the ad d i t i on o f 12 m g N l it e r -~ o fa m m o n i a c h l o r i d e ( N H 4 C I ) ( d a y 11 ) a n d 2 5 0 m l o f c o n c e n t r a t e d n i tr if y -i ng bac t e r i a (day 12 ) . Sys t em equ i l i b r i um re su l t ed i n 37 days and d em on-


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Biological f i l ter accl imat ion in blu e crab sh eddin g systems 233

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- , ' " B o c t e r i a ~ Ammonlo and" " " " " ' ' ~ N i t r i t e A d d i t i o n

i D i i i i i i , i i , t~ _~ L ~ i t , . ~ ' ~ . . , , , . J, . ~15 2 0 2 5 3 0 3 5 4 0 4 5 5 0 5 5

T I M E I N D A Y SF i lt e r a c c l im a t i o n c u r v e s o f s y s t e m s 4 - 6 u s i n g c o m m e r c i a l b a c te r ia , an d

a m m o n i a a n d n i tr it e a d d i t io n

s tra ted n o d ecrease i n s tar tu p t i me o f th e b i o l og i ca l f i l t er . T en crab s werei n t r o d u c e d t o s y s t e m 5 o n d a y 5 3 . N i t r i t e c o n c e n t r a t i o n s i n c r e a s e d t on e a r l y 3 m g l i t e r - ~ b e f o r e b a s e l i n e a m m o n i a a n d n i t r i t e c o n c e n t r a t i o n saga i n s tab i l i zed . T h i s b r i e f r i s e i n n i t r i t e wou l d resu l t i n mi n or l o s ses o fm o l t i n g c r ab s i n a c o m m e r c i a l s y s t e m .

S y s t e m 6 ( F ig . 3 ) w a s in t r o d u c e d w i t h 1 2 m g N l i t er - J o f a m m o n i ac h l o r i d e a n d 1 2 m g N l it e r - ~ s o d i u m n i t r it e ( N a N O 2 ) o n d a y 1 1 . O n d a y1 2 , 2 5 0 m l o f c o n c e n t r a t e d n i tr i fy i n g b a c t e r ia w e r e a d d e d . T h e s t a rt u pc u r v e r e s u l t e d w i t h s y s t e m e q u i l i b r i u m o c c u r r i n g i n 2 6 d a y s . B i o l o g i c a lf il te r a c c l i m a t i o n t i m e w a s r e d u c e d b y a f u ll 1 0 d a y s , s u g g e s ti n g t h a t t h ec o m b i n a t i o n o f a r t i f i c i a l a m m o n i a a n d n i t r i t e l o a d i n g w a s b e n e f i c i a l .L o a d i n g w a s i n i t i a t e d w i t h 1 0 c r a b s o n d a y 4 3 . T h e t r a n s i t o r y a m m o n i aa n d n i tr it e c u r v e s r o s e i n t o a m a r g i n a l o p e r a t i o n z o n e ( n it ri te c o n c e n t r a -t io n s a p p r o x i m a t e l y 3 m g l i te r - t) f o r a f iv e d a y p e r i o d b e f o r e r e t u r n in gt o b a s e l i n e c o n d i t i o n s .


8/10

234 D. P. Manthe, R. F. MaloneD I S C U S S I O N

S h o c k l o a d i n g o f c o m m e r c i a l c r a b s y s t e m s p r e s e n t s m a j o r p r o b l e m s a tthe b eg inn ing o f t he so f t she l l c r ab season i f b io log ica l f il te r s a r e no tp ro pe r ly acc l ima ted . In sys tems 1 -5 , t he b io log ica l f il te r s t oo k approx i -m a t e l y 3 6 d a y s t o a c c li m a t e . T h e l e n g t h o f t hi s c o n d i t i o n i n g p e r i o d i sc o n s i s t e n t w i t h t h e o b s e r v a t i o n s o f B o w e r a n d T u r n e r ( 1 9 8 1 ), a n d sig -n i f ic a n t ly s h o r t e r t h a n t h a t o f H i r a y a m a ( 1 9 7 4 ). H o w e v e r , d i f f e re n c e s insa l in i ty , t em pera tu re , a nd load ing r eg imes m ake d i r ec t com par i son s d if fi -c u lt . M a n t h e et aL ( 1 9 8 4 ) o b s e r v e d a n a c c l i m a t i o n t im e o f 3 0 d a y s inexp e r im en ta l c r ab shed d ing sys t ems . Sa l in it ie s and load ing r eg imes w eres im i l ar , b u t t e m p e r a t u r e s r a n g e d f r o m 1 2 t o 2 3 C . F u r t h e r s t u d y o f t em -pe ra tu re e f f ec t s on the b io log ica l f i l te r acc l ima t ion in c r ab shedd ings y s te m s s h o u l d b e u n d e r t a k e n .I n t h is s e r ie s o f e x p e r im e n t s , s y s te m s 1 - 4 d e m o n s t r a t e d t h e a b i li ty o fc r a b s h e d d i n g s y s te m s , o n c e a c c l im a t e d , t o h a n d l e i n c r e a s e d l o a d i n g b y afac to r o f fou r w i th in des ign con s t r a in t s . W i th a des ign capac i ty s l igh t lyl e ss t han 20 c rabs , t he sys t em dem on s t r a t e d the ab i li t y t o acc l ima te t ofu l l de s ign load ing i f a cc l ima ted wi th 25% of t he sys t ems des ign ( f i vec ra b s) . F u r t h e r r e s e a r c h m a y d e m o n s t r a t e t h a t f ew e r a n i m a l s c a n b e u s e di n a c c l i m a t i o n t o a c h i e v e t h e s a m e l o a d i n g p o t e n t ia l .B io log ica l f i lt e r m ed ia s ize h ad no e f f ec t on f i lt e r acc l im a t ion time .Th i s was a s expec t ed by theo re t i ca l cons ide ra t ions a s f i l t e r acc l ima t ionin th is s tage i s limi t ed by bac t e r i a g ene ra t ion t ime r a the r t han ava i l ab l esu r f ace a r ea o f t he med ia . As the sys t ems were l oaded to t he des ignl o a d i n g c a p a c i t y , t h e t r a n s i t o r y a m m o n i a a n d n i t r i t e c o n c e n t r a t i o n sinc reased a s med ia s i ze i nc reased . Th i s s eems to i nd i ca t e t ha t a s c r abload ing r eac hes sys t em des ign , one o f t he f ac to r s l imi t ing bac t e r i a lg rowth r a t e s i s su r f ace a r ea o f t he med ia fo r t he bac t e r i a t o co lon ize .Ho wev er , du r ing f i lt e r s t a r tup , su r f ace a r ea i s no t a cons id e ra t ion .A d d i t i o n o f c o n c e n t r a t e d n i tr if y in g b a c t e r i a d i d n o t h a v e a n y m e a s u r-ab l e e f fec t on acc l im a t ion o f t he shedd ing sys tems . P robab le r ea son s a r eb a c t e r i a l s h o c k d u e t o i n d u c t i o n i n t o a f o r e i g n e n v i r o n m e n t o r t h ei n a p p r o p r i a t e n e s s o f t h e c o m m e r c i a l a d d it iv e b a c t e r i a f o r t h e b i o l o g ic a lf i lt e r i n a c r ab shed d ing sys t em. Th i s is cons i s t en t w i th the o bse rva t ionso f B o w e r a n d T u r n e r ( 1 9 8 1 ) w h o t e s te d t h r e e c o m m e r c i a l a d d i ti v e s a n df o u n d n o a c c e l e r a t i o n i n th e n i t ri f ic a t i o n s e q u e n c e i n n ew s e a w a t e raqua r iums . Se ed ing o f f il te r s wi th subs t r a t e f ro m es t ab l i shed c rab sys t emf il te r s expo sed to s im i l a r s a l in i t ie s is p rob ab ly m ore app ropr i a t e .C h e m i c a l a c c l i m a t i o n w i t h a m m o n i a a d d i t i o n d i d n o t r e d u c e s t a r t u pt ime , b u t d id acc l ima te t he f i l t e r w i tho u t u s ing l ive an ima l s , t hus av o id ingthe h igh mor t a l i t i e s obse rved in t he s t a r tup o f sys t ems 1 -3 . Crab add i -t i ons a f t e r acc l ima t ion demons t r a t e t he ab i l i t y o f t he f i l t e r t o adap t t o


9/10

Bi o l o g i c a l f i lt e r a c c l ima t i o n i n b l u e c r a b s h e d d i n g s y s t e ms 235l o a d i n g u n d e r c o m m e r c i a l c o n d i t i o n s . T h i s is a d v a n t a g e o u s a s th e o p e r a -t o r c a n a c c l i m a t e t h e s y s te m e a r l i e r i n t h e s e a s o n w i t h o u t th e n e e d f o r a na n i m a l su p p ly . F u r t h e r m o r e , c r a b s a r e n o t s u b j ec t e d t o t h e d e t r i m e n t a lw a t e r q u a l i ty c o m m o n l y o b s e r v e d d u r i n g s y s te m a c c l i m a t io n .C h e m i c a l a c c l i m a t i o n u s i n g a c o m b i n a t i o n o f a m m o n i a a n d n i t r i t edec re ased b io log ica l f i lt e r acc l im a t ion t ime by 10 days . In t he sys t emc o n t a i n i n g c h e m i c a l a m m o n i a a n d n i tr it e , t h e b a c t e r ia i n i ti a ll y h a d ac o m p l e t e s u b s t r a t e t o f e e d o n . N i t r o b a c t e r sp . d id no t have to wa i tapp rox im a te ly 10 days t o have enoug h n i t r it e t o i nc rease it s pop u la t ion .T he s l igh t ly h ighe r r e spo nse cu rves o f sys tems 5 and 6 t o s eco nda ry c rabload ings (on days 53 and 43 , r e spec t ive ly ) sugges t t ha t t he sys t ems 'b a c t e r i a p o p u l a t i o n s w e r e d e p r i v e d o f s u b s t r a t e t o o l o n g p r i o r t o c r a bi n t r o d u c t i o n . T h u s t h e s e c o n d a r y p e a k s a r e a n a r t i f a c t o f t h e e x p e r i -m e n t a l d es ig n . T h e a u t h o r s b e l ie v e t h a t if c r a b s h a d b e e n a d d e d i m m e -d i a t e l y f o l l o w i n g a c c l i m a t i o n o f t h e s e s y s t e m s , t h e s e c o n d a r y p e a k sw o u l d h a v e b e e n n e g li gi b le . A d d i t i o n o f n i t ri t e h o l d s g r e a t p r o m i s e t or e d u c e f il te r a c c li m a t i o n t im e i n c r a b s h e d d i n g s y st em s . T h i s w o u l d b em o s t a d v a n t a g e o u s t o a c o m m e r c i a l c r a b s h e d d i n g s y s te m o p e r a t o r d u r -ing the beg inn ing o f t he she dd ing seaso n w hen l a rge pee l e r c r ab ha rves t sa re p rev a l en t . Fu r the r r e sea rch in t he a r ea o f a r t if i ci a l s t a r tup by ch em i -c a l a d d i t i o n i s n e e d e d f o r o t h e r a q u a c u l t u r e a p p l ic a t io n s .

C O N C L U S I O N S1. In t he l oad ing r eg imes t e s t ed , t he r e sea rch t eam has found no s ig -n i f i can t e f f ec t o f med ia s i ze on acc l ima t ion t ime o f t he n i t r i f i ca t ionbeds .2 . T he com m erc i a l add i t i ve con ta in ing n i t r ify ing bac t e r i a had n o s ign if i-

can t e f fec t on the b io log ica l f i l t e r 's ab i l i ty to a cc l im ate a t a fas te r ra te .3 . A m m o n i a a d d i t i o n t o s i m u l a te s y st e m lo a d i n g p r o p e r l y a c c li m a t e dthe b io log ica l f il te r , bu t d id no t sho r t en the acc l im a t ion time p e r iod .4 . T h e a d d i t i o n o f b o t h a m m o n i a a n d n i tr it e t o s ti m u l a te s i m u l t a n e o u sgrow th in bo th spec ie s o f n it r ify ing bac t e r i a ho lds t he mo s t p rom is ingavenue fo r fu tu re r e sea rch . N i t r i t e add i t i on du r ing s t a r tup o f a b io -log ica l f i lt e r r educ ed the acc l im a t ion pe r io d by 2 8% (o r 10 days) .

A C K N O W L E D G E M E N T ST h i s r e s e a r c h w a s s u p p o r t e d b y t h e L o u i s i a n a S e a G r a n t C o l l e g e P r o -g r am . C o l l a b o r a t i v e s u p p o r t w a s p r o v i d e d b y th e M i s s i s s i p p i - A l a b a m aS e a G r a n t C o n s o r t i u m . T h e s e p r o g r a m s a r e e l e m e n t s o f t h e N a t i o n a l S e a


10/10

236 D. P. Manthe, R. F. M aloneG r a n t C o l le g e P r o g r am , u n d e r t h e d i r e c t io n of N O A A , U S D e p a r t m e n to f C o m m e r c e . C r a b s w e r e s u p p l i e d a n d i n v a lu a b l e t e ch n i c a l a d v i ceg i v e n b y M r C u l tu s P e a r s o n t h r o u g h h is c o m m e r c i a l o p e r a t i o n i nL a C o m b e , L o u i s ia n a . D o n a t i o n o f f il te r t a n k s b y P l a n t a t io n F i b e r g l as o fB u s h , L o u i s ia n a , is a c k n o w l e d g e d . L a b o r a t o r y a n al ys is w a s p e r f o r m e db y L o T a n .

R E F E R E N C E SA P H A ( 1 98 0 ). S tandard M e thods fo r t he Ex am ina t ion o f W a ter and W as te -w a te r.15th edn , A m er i can W ater W orks Assoc i a ti on , and W ater Po l lu t ion Cont ro l

Fede ra t i on , A m er i can Publ i c Hea l th A ssoc i a ti on , W ashing ton , DC , U SA .Bow er , C . E . & Turner , D . T . (1981) . A cce le ra ted ni t ri f ica t ion in new seaw atercul ture sys tems: e ffec t iveness of com m erc ia l addi t ives and seed m edia f romestabl i shed sys tems. Aquac u l tu re , 24 , 1 - 9 .Har t ens t e in , R . (1970) . N i t rogen m e tabol i sm in no n- insec t a r t h ropods . In: C o m -parat ive Bioc hem is try o f N i trogen M etabol i sm , Vol . 1 , ed. J . W. Campbel l ,A c a d e m i c Pre ss , pp . 29 9 - 3 72 .Hirayam a, K. (1974) . W ater cont ro l by f i lt ra t ion in c losed sys tems. Aquac u l tu re ,4 ,369-85 .Jaworski , E . (1971) . Decl ine o f the so f t she l l b lue crab f i shery in Louis iana ,En vi ro nm enta l Qu al i ty No te 4 , Texas A & M Univers i ty , Co l lege Sta tion,Texas , USA.M anth e, D. P., M alon e, R. F. & Perry, H. M . (198 3). W ater qual i ty f luctuat ions inre sponse t o va r i ab l e l oad ing in a commerc i a l c losed b lue c rab sheddingfacility. Jou rnal o f She ll fi sh Research , 3 , 1 75 -8 2 .M anthe , D. P ., Malon e , R . E & K um ar (1984) . Lim i t ing fac tors assoc ia ted wi thni t ri f ica t ion in c los ed blu e c rab shed ding sys tems. Aquacul tura l Engineer ing ,3 , 119 - 39 .Mevel , G. & Chamroux, S . (1981) . A s tudy on ni t r i f ica t ion in the presence ofprawns (Penaeus. ]aponicus) in marine c losed sys tems. Aquac u l tu re , 23 ,2 9 - 4 3 .

Perry, H. M . , Ogle , J . T. & Nich olson, L . C . (1982) . T he f i shery for sof t c rabswi th em phas i s on t he de ve lop m ent o f a c losed rec i rcu l a ti ng seawa te r sys t emfor sh edd ing c rabs. In: Proceedings o f the Blue Crab C ol loquium , 1979, e ds H .M. Perry & W. A. Van En gel , Gu l f Sta tes M arine Fisher ies Com m iss ion, No.7 , pp . 13 7-5 0 .Spotte , S. (1979). Fish and Inver tebrate Cul ture , Water M ana gem ent in C losedSystems, 2nd edn , W i ley- In te r sc ience , N ew Y ork , US A.Whea ton , E W. (1977) . Aquacul tura l Engineer ing , Wiley-Inte rsc ience , NewY or k , U S A .

manthe 1987 aquacultural-engineering

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