GeorgeT.Mccabe,Jr., Susan A. Hinton,and Robert L. Emmett
F sli EcorogyDlvlslonNorth\,!es1
F sheres Sc ence CenterNatona N4arine
F sheres Service.
Natona Oceanc and Atrnospher
c Adm n stfaton 2725[4ontake Bo! evardEast,Seatie Washnqton 981]2 zA,Jf
BenthicInvertebrates
and SedimentCharacteristics
in a Shallow
NavigationChannelof the LowerColumbiaRiver,Beforeand After
Dredging
Abstract
L i t t l e i \ k n o \ t n a b o u tl l r cj n r p a c ro f d r e d g i r ! o n b e n t h i ci n \ e r r e b r a r ci n
s n . r \ i g a r i o nc h n n e l so f i h e l o l l e r C o l u n b i a R i v e r .T o h e l p
iill rhi\ inforrratio.al !ord. rc conductedbenthic invertebratcand scdil1lcrr\tudies in .Lshxlloll na\'igati()l1channel in the dler
b e l b r e . r n da i i e r d r e d g i g . B c n l h i ci n v e r t e b r a tren d s e d i J n e nsta n r p l c s$ c r c c o l l e c t e d$ i t h x 0 . 1 l r l r v i n \ t c n g f t b s a n r p l e xf r
sevenstrtrons in lhe Wahki.1kurnCoLrnt)Fe[) Ch.rnnel.Wxshington(Ri\cr Kiluneter 70). lnd ar an npstrca|r rcierencerrer in
1 q g i 1 9 9 5 . N o s i g n i l i c a n le i t e c t \ ( P > 0 . 0 5 ) o i r h e l e f f f c h r L n n edlr e d g i n gp r o i c c l o r C . r b i . u l t l l l u n r i t l e u C
. !'raloposonidrc
lur\ re. Col./t,n,n sff., or total bcnthic inlcflebrute den\iIies \refe detectedin lhc nldstic.rl anxhsis. lhhough bcnlhic iD\ erteb f a l ed e n \ i I i e \q , e f es i g n i i l c a n t l rd_i l l c r c n t( P < 0 . 0 5 ) b e t $ e e ns u l \ e \ ' sa n dn r c . r sl o r \ o m e o r g . r n i \ m \ . D u r j n g a l l c i g h r s u r v e r - \ .
Con,nllL1]1unuk11'(i,|",rl,'\pp.andCerat(rgr3onid.reiDip!era)lar!ac\!eIegenefl1l\thenlostcollnonbcnlhi0in\efe.
b|.rlesinboththciin.}clrannc].rndiherle|enceli|el'T$'omcaSurL'\ol.co
$,efe cai.ulated ibr cach rrc.r lor erch sune)- No significanr cllict\ {P>0.051 ofthe t_errychanncl drcdling project on rhe
b e n t h i L ' r . \ ' c n c b r ! tcco m n u n i t ! \ t r r r r u f e . . r \ m e a \ u r e dh ) l l a r d E . \ \ e r e d e t e c t e dN
. o s i g n i i i c a ncr f l i c l s ( P > 0 . 0 5 )o f d r e r n n . l
chxnnel dfedging projccl ()lr scdiment median grrin \i7e or perccnl \olarile solids $efe detected. Rc\ulr\ lioln rhis stud) |\ill
pfo\ ide infofmation lrr aqualic .csoLrce.r,rencicsthrt as\es\ Ihe porc.rial cn\ ironmentrl eftectsof dredgingin similar h.rbitatsof
t h e l o $ e f C o l u m b i aI t i \ e r .
lntroduction
The lower ColumbiaRiver from thc mouth to
Porlland.Oregon.is an irnponantnavigationchaD
nel that is traintaincdio a depthof 12.2m bv
dredging.ln adclition.variousshallowersecondary
n i g l t i , ' r rc h u r r r r eiln. t h c l o u e r r i r e r l r r n t r i r r tainedthroughdredging. Little is knorvnrbout
the impact of drcdgin-eon benthjc invertebrates
in thc lorverColumbiaRiver. To help lill this
infbrrnational
void. we conductcdbenthicinver
tebrate and sedimcnt studies in the \\'ahkiakun
Countl FerryChannel.rrvashingtol(RiverKilomeler (RKm) 70.).betbreand after dredgingof
the channel.
Thc \\ahkiakum CountvFen1.rvhichis ownecl
ud operatedby WahkiakumCounty and subsi
dized by the State of \\'ashirgton, operatesbct\\,ccn\restpoft. Olegon,ald Pugetlsland.Washington.Priorto our sun'eys.shoalingin theterry
channelbetweenPugetlslandandthe marnnavrgationcharnelof thc ColunrbiaRiverlorcedthe
ttr) 1()opcratert one-half capacity during parr
ol the;-ear(U.S.Army Corpsof EngineersJ9921.
Clanshell clrcdgingu'asconductedin about2.1.1
nr
ll6
N o r t h w e sSt c i e n c cV, l i . 7 2 , N o . 2 . 1 9 9 E
.i L')llh\ rlrc\.nnL.!\ti.nrtii.\s..LdnrL
\lt.LhL.tir\r1t
of the f'errvchannellion 24 Januarvto l7 Feb
ruary 199.1.About l.+.258mr ol sedinettswere
rcmovedlioor the chalnel and disposedof at an
in-waterdisposalsiteabout4km do\r,nstrermfiom
the feII] channel.Althoughthe ferry channelis
about 579 m long. oniy about 2.+'lm htrd to be
dredged.as Lhercrnainderof the channelis naturally deep.Thc dredgedporlionof thefen y channel
is 6l m widc andauthoizedto a dcpthof 2.7 m.
{ l t h o u g ht h er r e r , ' l t h cJ r e J g i n ;p r r , j er. s r .
small,there$as conccmthatbenthicinvenebrates,
pafticularLythe amphipodsCorolthiunt spp. lC.
.salnoni:stnd C. spirlconre). would be adversely
inrpacted. Coro2lririrnspp. are liequentll' found
in intertidaland shallou subtidalhabitatsof thc
ColumbiaRiver estuarl,andare seasonallyimportart il] the dietsofjuvcnile salmolids andothcr
tishes(McCabeet al. I983. 19ti6:Kirnetal.l986:
Muir ct al. 19881.Corophfumsdlm(nit xnd C.
spinicornewere the doninant prev firr jurenile
salmonidscollectedduringthe springof l9E;l at
BonnevilleDam. the lowennostdam on the Co
lumbiaRiver(Muir and Enrmcltl98E).
The goalsof the prescnlsludywere l) to describebenthicinverteblatecommunitiesin thc
dredgedportion of the ttrry channelbefore and
recolonization
bv
atierdrcdgingand 2) to assess
benthic in\,ertebratesin the dredgedporlion of
the ferry channel.We collectedsrmplesin a refercncc arealocatedabout 3.2 knr upslrcamfrorn
fte ferry,charnelto helpasscsstheeffectsofdredging. Specitically.we assessed
benthicinvcrtcstandingclops.diverbratespeciescompr)sition.
sitl', rnd cquitability in both the lerry channcland
the upstreamreferenccarea. Resultsliom this
studyrvill pror ide infonnationto i,rqurticrcsource
the potentialcnvironmental
agcnciesthat assess
effectsofdredgingin sinrilarhabitatsofthe lou'er
ColumbiaRivcr.
Methods
Samp ing
Benthicinvertebrate
and sedimentsanrplcswere
collectedat sevel stationseachin the \Vahkiakum
rclerence
Count;-Felry Cihanncland an Lrpstream
arcain Oclober1993:Januarl.Fcbruary.April.
Jull', and Octobcr 1994:and Jaluar-vand April
1995(Figurel). Samplingin Ocbber 1993aDd
Jaluary 199,1wasconductedplior to dredgingin
the ttrry channel.and sanpling in FebruaryI 99,1
was conducted6 days attel clrcdgingwas com
pleted. Mean waterdcplhs.by surve!. in the terr)
channcl ancl referencearea ranged fion 2.0 to
3.8 m and 2.3 t{).1.7m (meanlowel low rvater),
rcspccli\ely.Sanpling stationswcrc locatedLrs
andthe GlobalPositioning a radarrangc-finder
i n g S l s l c m( G P S ) .
At each of Lhe1,1stations,a 0.I -nrr Vrn Vccn
trab samplerrvasusedto collecttour samples:three
u'erernalyzedfirrbenlhicil'rvertebrates
andonefor
scclinenttype. Each benthic invcncbralesample
was initialll prcsen'edin a bufferedlbrmaldehydc
solution(>.17.)contrining rosebcngal,an organic
staiD.Later eachbenthicinvenebratesanple was
$ashedwith walertluougha 0.5-mmscreen.A11
benthicinvefiebntesweresodedtiom cachsample,
identifled to the lo$est practicaltaxon, countecl.
and storedin 70'l. ethanol. The sedimcntsample
fiom each stationwas placedin a labeledplastic
bag.refrigerated,and nalyTedti)r grain size.per
centsilt/c]a,"-,
andpcrcenn'olatilesolidsby theU.S.
Arnr_vCorpsof Engineels.Norlh Pacific Division
MaledalsLaboratory.Troutdlle, Orcgon.
DataAnayses
Benthicinvcncbratedatawere analyzedby stadensities
tion to determinespeciescomposilioD,
(b) taxol and total), and communitvstructure
(diversityandequitabilitl). Thc ShannonWiener
tunction(H) wasuscdto determinediversity(Krebs
1978),which wasexplessed
rs:
.i
H=-Ilpr(togp)
;-t
rvhercp, = nr/N (n, is the numberof individuals
of the ith taxonin the samplc,and N is the total
lurnber of all individualsin the sample)and
s = numberoftaxa.Equitability(E) wasthe second community str-uctureindex dctcrmined: E
measuresthe proportionalabuDdances
amongthe
varioustaxain a sample(Krebs197IJ)andranges
from 0.00to 1.00.with 1.00indicating all taxr in
the sanplearenumericallyequal.Equitabilityis
expressed
as:
E = H/log.s
=Dun
rvhereH= Shannon-Wienerfunclionimds
ber of taxa. Both H rnd E werc calculatedfor
each sampling station.
TotalbeDthicin\'efiebratedensities.Coiblcrrla
lhrnirtea, Co ropli tan spp..and Ceratopogonidre
(Diptera)larval densitics.H. ard E rvereeach
comparedbetweenareas(i.e.. thc fcrr) channel
and referencearea)and surveys using 1$o way
analysisofvadance(ANOVA) (CruzcandHartzell
l99l). Resultsliom thetrvo-wayANOVAs were
uscdto detemine signiticant(P < 0.05) inrpacts
ol the dred-qingpro.jecton benthic invertebrate
dersities.H. and E. Becauscsanplingwascon
Jtretedin theterl r'hrnnelrntl rclcrcnierreuprior
to and aftel dredging,we rvercablc 1odetemine
any significant impactsof the drcdging b5'using
theinteractionterm (sun'eyx area)in thcANOVA.
A significantintemctionindicateda statistically
significant eft'cctof the dredging. Inrertebrate
densities
weretestedtbr normality,and,ifneces
sary. transtbrnred(1og,u)prior ltl performing
ANOVA. Normality was testedby calculaling
normal scoresof the data.then conductinga cor
relationtest bet$eenthe nomal scoresand the
data(Cruzeand Hafizell l99l). Mcan dersities
of inveftcbrabsftom individual samplingstrtions
p n r ri L l e Lt hl eJ . r l rf o r \ t r t i . t i c . rllc s t . .
in a ShallowNavisiltionChannel 111
BenthicInveftebrates
.=
.=
a
.=
-
j
J
?.
7 !
a.-
Ec
-a
..-!
118
McCabe,Hinton.and Emmett
Mediangrain sizeand pcrcentvolatilesolids
of the sedimentsanples u'ere each compared
bct\r-cenareas(i.e..the ttrrv channeland refererce arer) anclsulve,vsusing two-wa1-ANOVA
(CruzeandHartzell 199 I ): mediangrain sizeand
percentvolatilcsolidswere testedti)r nomtality
and transformed (logr.) prior Lo pelformilg
ANOVA. Onelow outlyingraluelbrmediangrrin
size(StationW3, Jul.v199,1)was renrovcdpriol
1i)r
k) usingANOVA. No statislicalcomparisons
percent silt/clay were made bccauseof the
nonnortrraldistribution of the data and the lack
da|atranstbrmation.
of an adecluaLc
Results
BenthicInvertebrates
During all cight surve-vs.
Corbiculu.fluninea,
Corc4thiuttspp..tnd Ccratopogoridaelarvaewcrc
generall),thc most commor benthicinvcrtebrates
i r r h l t l r t h e l c n l e h l n n e lr t t d t l t ut e l e r c n c rcr e . '
(Tablel). Il both arcas,thesethreetaxa reprcsented90% or more of the total benthicinverte
bratedensities
d!.ing all surveys,excepttheJuly
199,1suncy in lhe relelencearea. In bolh areas,
Ootttphiun spp. werc generall,vthe most abundaot benthicinve ebntes (Figufe2). We esti
matedthatabout98% ofthe CoroTrhiri,rspp.were
C-.srrlrpnls andthe renraindcrC. spinicot'rte.The
f r o p o r t i L r n i.rrlh u n J r n c c9s1 1 , , 7 6 1 7 ' l r r. rprpr r ri t t
the ferry channelrangediiom 59% in Jul.v1994
to 93% in January1995:in the relerenccarea.
thc propofiional abundancesrangeclfrom 2.1%in
199.1.
July l994 to li57r in Januar,v
collccted
The totirl numbcrsof taxa./categories
in theterrychannelandrelerencearca(datacom
bincdforbothareas)rangedfrom I I irApril 1994
to 27 in October199:1.Mean numbersof tirxa/
categories(b1'survey)in thc ferr,rchamel and
referenceareawcre similal. ranging front 6 to I I
(Table2).
Thc differencesbetweenilreas for Corbit:ulct
lan'ae.Cotp,4ltaz spp.,
JlLt ineo. Ceri\tepoyonidae
andtotrl bcnthic invefiebratedensiticsandH and
E did not changeoverthesurveys.indicatingthat
the dredgingdid not havea statisticallysignifi
(Tablc3).
cant(P < 0.05)effecton theseparameters
All inteftctiontenlrs(sunel x arca)in theanalyses
wcrenonsignillcant(P > 0.05),indicatingno etfect ofthe dredging.Althoughue could not de
tect statistically signitlcant ef'tbctsof the dredg
ing on belthic invefiebrate densities.there ap
pearedto be a potential dampcningetTecton invertebratesinrmcdiately aftel the dredging
(Table1). The dredgirgin the ferry channcldid
not appearto have any obviousimpacton less
comnoD taxa lbund in the channel.
larvae.
eu,Ceratopog()nidac
Corb icukt.fltLmirt
and total bcnthic ir'rvefiebntedensitieswcrc sig
niticaltly differentbetweensurvcysand areas
(ANOVA,P < 0.05).with densities
beingsignitiareathan
cantlyhigher(P < 0.05)in thereference
in the ttrD' channel(Tables I and 3). In the ref
erenccarea.[lean tota] benthic invcrtcbrateden
sities(by survey)mngedfiom 2.291organisms/
in April
mr in Jul1 199'1to 25,266organisms/mr
1994 (Table l). Mean total benthic invefiebrate
densities(by survey) in thc ferry channelmnged
from 2.004 organisms/mrin Februar-) 199,1to
23,79.1organisms/mrin Januarl'1995. Mean
in thcrclcrencearea
Corbia aflumineudensities
in April 1995to
rangcclfrom 631 organisms/mr
2,765 organisms/mrin April 199,1(Table I ). and
mcan densitiesin the ferry channelrangedlion
19.1organisms/mrin Fcbruary1994to 1.360organisms/nr:in October 1994. In the reterencc
area.trlcan densitiesof Ceratopogonidaelarlae
in July 199'1to
rangcdliom 52l organisms/mr
2.159organisms/mr
in October199,1(Tablel).
larvaein the
Meanclcnsities
of Ceratopogoniclac
ferry channelranged from 396 organisns/mr in
Fcbruary 199'1to I, I 16 organisms/n']in January
199'+.
Corcplt[un spp.dcnsities.H. and E u'ere signiticantly ditl'ercnt between surveys (ANOVA.
P < 0 . 0 5 ) . b u t n o t b e t w e e na r e a s( A N O V A ,
P > 0.05) (Table 3). ln the leferencearea.mean
densitiesof Corophfunspp.(by survel) rangcd
July 199.1to 19.888
tiom 542 organisns/m'?in
organisns/m2
inApril 1994(Tublc1). MeaDden
sities in the terry channclrangedfrom l,36'1 orgadsms/mrin Fcbruaryl99.1to 22.157organisns/m'in January199-5.Mean H values(by
suney) in the rcfcrencearearangedfiom 1.02 in
January199:1to 2.22in July l99rt (Table2). In
thet'en1channel.meanHvalues(by sunc)) ranged
tiom 0.8,1inApril 1995ro I .ll5 in July 199,1.Mean
E values(by surve)')in the referencearearanged
liom 0.34 in OcLober199:1to 0.70 in July 199,1
(Tabie2). ln the feny channei,meanE valucs
(by survey)rangedfrom 0.30in October1994Lo
0 . 6 1i n J u l y 1 9 9 , 1 .
Benthicln\efiebratesin a ShallowNavigationChannel l t 9
T A B L E l . \ { c a n d e n \ i I i e s( n u n r b c r / r r ror tf b e n i h j ci . ! c n c b r a t e sc o l l e c t c dd u r m g e i g h r s u r \ c - - si n \ \ ' r h k i a k u n C o u n t ! F c n . }
(lhanncl \\ra\hingtm. arrda rclerence.r|ea. 1993 1995 The ttrr\ channeli\.r\drcdgcdrliertheJrnu|1ry
t99,1suNey
a n dp f i o r t o l h c f e b r u r r ! 1 9 9 . 1 s n r \ c ! .
,,Ltuhur
Trxon/crtegor!
IJnL.rr\
t99l
1991
Aprii
199.1
F eh Lu J r- " -
199:l
Jul)
199.1
Ocbbef
199.1
January
1995
Apfil
1995
FERRY CH,\\\EI2
(l
0
Turbelhfia
0
0
15
0
0
l-)
0
i06
0
)
0
l:
0
0
I
<l
Poh chaelil
N', rlt(s IitIul I)l0
t)
Oligochreta
21
Casrrop0dr
{)
0
0
21
0
0
l
0
510
0
0
l9l
0
1l
0
L l m n . r e i d a (! 'L r n i d e nlti.m p e t l
f'lut " it it t) lLtI it.n\
Bi\rl\ ir
Cothit Lhflut
ined
Ostmcoda
0
0
2
u
0
l2l
0
l-)
)
19
0
0
8|
1l
t.07'1
0
l
I
l:0
0
3.1.1
t99
U
0
[0
tl
0
I9.+
0
:Ll5
0
3
0
0
r98
I
0
189
0
1
l
0
t.ld)
2
)
2
612
r\nrphip0dtr
Cot?phit"t:pp.
l.l,ll
E.565
0
l
1.,t:l
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0
l-)
0
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0
(l
L)
0
l)
0
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t)
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l)
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(l
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Ra,k lIorit ,tdr s oftqon.nli\
)
0
Prtur4nrtu ltL^i
Gt tot itnosphu ron d o rc4 tt tnsi t
l{up.rcticoid.r
H)dmcarina
C o l l e J r b o l a. r d u l t
0
<t
0
Plccoplcr.tn) mph
Eph.meroptem nylnplr
3.816
t)
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I ' t ) nr l l n \ t t b t r
(irtcpodi
1.36,1
0
0
Rtln1!| h,su,t Drd rus spp.
0
0
Odon.Lr.L
ntnrph
Hemiplcra
Trichoptera larrac
li
Coleoprcrr lttr\rLe
(
J
{)
0
16,509
(
l
:
22.t51
12.t11
.1
23
l
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0
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t)
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l
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0
N I i \ c e l l a n e o ulsl i p t c r r
C h i f o n o n r i d a lc. r \ e
C h i r o . o r D i d a pe u p a e
( crrbposonida.- larv.r
Tolri nunber/m'
l0
l,l
l
u
1.076
5.0r2
r . 1 t6
10.I8-.
0
196
r.001
5/
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5,.1.1,1
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3,1
160
2.11I
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10.390
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C o n t i r e d .n e \ ( p a g e
120 McCabe.Hintorr.rnd Enmctr
'IABLF
I ContiDued
'llrion/c.1tcg()r
y
Ocbbcr
I99l
l.rDu.rf]
r99,1
Februarl
April
lrrl
l99l
July Ocrobcr
199.1 l99t
Jrnu.rry
1995
April
t995
RI'T'ERENCEAREA
0
Turbcllalir
l
0
0
<l
Lr
87
tl
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Oiieochaetil
|]9
l7l
Chsrr0podrL
1
0
0
N t a n t h t sl u n n i n l a
L ) n r n a c i d a c( L r n i d e nlti.m p e r )
nLt"tutitoltl \'iftn\
B i \ ' a l \i a
( otl,kutti fl ni a1
0
78
0
o
t .t 6 0
0
0
I l,l
0
1.897
0
<1
l)
0
u
l)
8.1
<1
(
2.159
0
i)
536
{
l
t)
78
,
0
U
:.765
0
66
{)
2
11
29
0
1
0
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1)3
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19-.
)
259
0
0
l.ll
0
671
t
t9t
112
0
l
0
0
318
13r
)
t.568
0
1.783
0
0
.13
0
6lt
0
0
Alnphipod.r
(ItrtilltLult \pp.
t.'u8
Ratrrclloru ndn6 spp.
l
Rdti eI I o'!anLntunt\ . ^'gattot si:i
0
H\tl.lla
0
u-t!ru
hnt0t)0tia
l'i)\i
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{)
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Gu, it,o\phaoo n oftso"ensis
Poftcllio:cdlJer
CopepodrL
H.lrprcticoida
Hldracirilra
0
t)
C o l l c m b o l ar d u l t
L)
0
0
0
<l
0
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<l
l)
{l
3
0
Ephemer(rplcranylnpll
0
0
Odon|tuLn!nph
l)
(_)
0
0
Trichoptera lana!'
0
0
0
Colcoplcru lar!ae
0
0
0
0
0
Plecoptcm nlmph
llcmipteru
il
0
0
0
0
0
0
0
0
0
0
0
0
Miscell.rneousl)jplcr!
C h i r o l l o m i d . rleI r \ a e
Chironomidae tupae
Cer.itl:)poconidae
larrnc
Toul nulnber/ml
-|
l
l.'189
5.lll
93
0
l.3rl
2-r.,ll8
lJo
<l
-r29
0
1.131 1.656
19.097 15.266
20
26
21
I
521
2.159
2,291 2l.50it
1l
0
LI22
t0 371
16
<l
980
11.286
BenthicInvertebrates
in a ShallowNavisalionChannel I21
l i 0- 5
;
,l<
ER r_ -o
a
z
J
Oct 1993 Jar 1994
Feb 1994
AV 1994
Jul 1994
Oct 1994
Jan 1995
Apr 1995
Oct 1994 Jan1995
Apr 1995
Ferry Channel
30
j
s - -
=
s
Ocr1993 Jan1994
Feb1994 Apr 1994
Jul1994
ReferenceArea
of organismy# I
ffiffi M"- to.a number
Meannumber
of Carophiunspp
.lrr?
Figurc 2. NIcandcn\itics of bcnllic in\erlebrutes(totrl) and C.r/r/r//'r? spp. in \\rahkiakumCount] l-err! Channcl.\\hshirgton.
nd r feference.re.r. l99l-1995. The ferry channellvasdredgedaiier thcJanuar! 199:lsurvcy andprior to the Februr0
1991sufvei.
Sed ments
Although median grain sizc was si-qnificantly
smallerin the lenv channelthan in the reference
area (ANOVA, P = 0.00), no eftect of the ferry
.hirnned
l r c d g i n gp r o j e c tn r r n e d i a ng r r i n . i z e
rvasdetectedin the statisticalanalysis.as indicatedby the nonsignitlcant
interaction(P = 0.88)
bet$een survey and area in the ANOVA. The
ovelall n.reansfor median grain sizesin the lerry
channeland referenceareawere 0.29 and 0.37
(Table,l). Mediangrain sizcs
mm, respectively
were not signiticantlydiflerentbetweensuneys
122
McCabe.Hinton,rnd Emmett
(ANOVA, P = 0.l8). Mean mediangrain sizes
in thc fcrry channelrangedtiom 0.24 mm in Juh
199.+to 0.32 mm in January1994,whcrcasin the
referencearea. oreanmedian grain sizesrangccl
frorr 0.33 mnr in January1995to 0.'+0mm in
October1993(Table,1).
The overall meansfor percentssilt/clay in the
len1,channclandrcfcrcnceareawere2.Eand I . I 7r.
respectively(Table,1). Tnthe leny channel,mean
percentssilf/clayrangedfron 0.1%in January1994
to 8.67cin July 199,1.Mean percentssilt/clay in
the referencearea rangedliom 0..17r,in October
l993 andJanuary1994to2.1Vo
inApril 1995.
T A B L [ ] . \ { e r l n n u m b e N o fb e n t h i ci n v e r t e b r a rrca r a / c l t e g o r i eisd e n t i f l e d . r n m
d e a nd i l c r s i t i c s( H l a n d D r e r ne q u i t l b i l i t i c s( E )
c a l c u l a l c di b r b e n $ i c i r \ e f t e b r a t es r m p l e sc o l l c c t c dd u r i n g e i g h t s u r v e ] si n \ \ a h k i a k u n C l o u n t rF e f r ] C h a n n e l .
\ \ a s h i n g t o n a. n da r c l c r c n c c. r r e . l1. 9 q 3 - 1 9 9 5T. h e f e r r yc h a n n c l $ r l sd r c d s e da t i e r i h eJ a n a r y l 9 9 , l s u l r c v a r d p r i o r
k) the February 199.1sunc\'.
Oclobcr
1993
H
I]
1
l.t.l
0..19
No. oftr\r
H
L
1
1.58
0.51
Jrnuu)199.1
Febfuary
199.1
t'
1.07
0.Jl
April
1991
Jul)
JanLrar,"1995
Octobef
199.1
F}]RRY CHANNEL
6
6
1.25
1.26
0.17
0.50
April
1995
8
1.85
0.6r
1.03
0.lt)
9
r.0l
0.38
1
0.8.1
0.31
9
).22
0.10
1.07
0.1.1
li
l.l3
0.38
1
Ll8
0.,1.1
l l
REFERENCEAREA
'L\
7
r.02
0.38
8
1.0-r
0.17
7
126
0,ll
tsL E L Rcsull\ o I I $ o wtr,,_
antrl)si\ of v.rriancefor selectcdbcnthic invertebrutepafametefsmeasrLrcd
in Wahkiakum Counry
Ferrv Channcl. \Ushi.gln. and I referencearea. l99l 1995. Rc\ull! lron eight sur\'el''\ Ocrober I991. Janu r).
Februar,v-,
April. Julv, and Oct(rbcr 199,+.and Jruluar] andApril 1995 $'crc uscd in the anallses. r\ significanr
d i l l c r c n c e( P < 0 . 0 5 ) i \ i n d i c a t e d\ \ ' i t ha . ' ! ' .
Dcgreesof lieedonr
Bcnfiic invertebfrte
d e n s i r r( l o g . 1 .
(xrl
1
Suney r area
lbtal (lcg. riccdoln)
('t,bi(utd lt ttiitrcd
d e . s r q( l o g , )
alrrqtri,,r
(los ,)
stp. den,,it]
Surve) x area
Tdal (deg. freedo )
Sur\ev
Total kleg. freedom)
Cerrtopogonidre
la|lae
'lbtal
ldcg. lrccdont
l ) i \ c r s i l _ "( H
" )
'Ibli1l (dcg.
E q i r a b i l i t , (\ E l
liccddrl
S u ne )
Surve) x.Lre.r
Tot.rl (deg. lieedont
No el'fectofthc ferrv channeldredgingprojecr
on percentvolatilesolidswas detcctcd.as indicatedby thenonsignificant
interaction(P = 0.-56)
between survey ard area in the ANOVA. Per
ccntsvolatilesdids werenot significantlydiff'erentbetweenarcas(ANOVA. P = 0..15)and.over-
I
'I
1 1 1
1
l
1
111
1
I
1
111
I
I
I
l l l
,7
1
l l l
1
1
1
P value
5..10
6.21
1.90
0.000,1,
0.01.1"
0.07E
2.19
|].07
r.03
0.o27'.
0.000'
0. 5
5.01
0.:5
l.5l
0.000*
0.615
0.166
3..19
22.12
1.65
0.003i
0.000*
0 .t 2 9
I1.76
1.0,+
1.00
0.000,!,
0.156
0.138
6.21
0.15
0.8l
0.000*
0.55.1
0.579
all, averaged0.6% in eacharer (Table:l). Percentsvolatilcsolidswere sigDificantlydifTerent
bet*'eensurveys(ANOVA, P = 0.01). In the fen_a'
channcl.meanpercentsvolatilesolidsrangedlionl
0.5rlcin January 1994 to 0.8c/riin April 199.1
(Table4). In the refercncearea. meanpercents
BenthicInvertebrates
in a ShallowNavigationChanncl
123
l l U I - F - . 1 .l \ { e a nm e d i a ng r a i ns i z e s( m m ) .p e r c e n tssi l t / c l a , a
v .n dp e r c e n t!s( n a l v o l a t i l seo l i d so f s e d i en t ss a r r p l c dj n W a h k i r k u n
Count,v Fefry Chrnnel. \\rashingt()n,and a feference afea. 1993-1995. The r-er] channel $rs dfedged aiier thc
J l l n u l t r )1 9 9 . 1 s u I \ e )a n dp r i o r t o t h c F c b r u r r y 1 9 9 . 1 ! u r ! c r " .
Ocrobef
1993
C r x i l l s i T e( ' n ' n )
Silt.h] (.t )
\i)1.rolid\ (? )
t).1r
0.1
Gr.ri'1size onm)
S i l r / c l a )( ? )
Vol. solid\r't)
0.,t0
J.rnu.rry
199,1
0.tl
l).I
Febru i
1991
Apn'
199.1
FERRY CHA\\EI0.ll
0.29
t 3
1.7
0.5
0.-rl
REFERENCEAREA
0.39
0.38
t.1
0.6
volatile solidsrangedtiom 0.5% in October l99.,1
and January1995to 0.E'/rin ApriJ 1994. Sedimentsfrom the fenl channelwere testedfor con
taminantsplior to the dredgingprojectand were
(JonGornick,U.S.
founclto be uncontaminated
Arn)'Corys of Engineers,Potland District. PO.
Box 2946.Potland. OR 97208. Pers.commun.
26 Februar"-1996).
Discussion
The el'fectsof dredging on benthic invefiebrale
comnunitiesvan widelv. Moton (1977).who
conducteda literaturereviervof the ecological
cll'cctsofdrcdginganddrcd-scspoildisposal,notcd
that initial ellects can range liom negligible to
sc!crcandimpactsrangeli(nn shonto long tenn.
Basedon his literaturereview,Morton (1977)
concludccl
thal sho -term.small-scale
dredging
anddredgespoildisposalproiectsinpactedbenthic
c o m m u n i t i e sl e s st h a n l o n g - t e r m l.a r g e - s c a l e
projccts.
Wc u,crc unablc to dctect any signilicant effectofthe clamshelldredgingprojecton thestanding crops ol benthic invertebraLes
in Wahkiakun
CountyFen-yChrnnel. Apparently.benthicinvcrtcbratcsin thc drcdgccllrca werc ablc to recolonizethe areaquite rapidly'.after dredging. Lr
a study of the ellects of dredgingon benthic
macroinvcficbratcs
in a SouthCitrolrnacstuary.
Van Dolah et al. (198.1)roted sholt term eflects
of a drcdgingprojcct,with substantial
recovery
within 3 months. They attributedmuch of the
rapidrecolonizationto inlmigration\ ia sediments
of the slumping channelrvalls.which were srmr
lrr to the sedimentsremovedduring dredging.
Bcnthicinvcmebrates
living in thc slumpingchanncl
12.1 McCabe.Hinton.andEnmett
Julr"
Ociobef
1991
Jrnuar]
1995
r\pril
1995
0.21
8.6
0.7
0.29
2.1
0.27
5.0
o.'7
0.10
2.6
f).'1
0.39
0.36
0.5
0.5
0.33
0.35
2.1
0.7
0.6
0.5
walls adjacentto WahkiakumCounty Fcrry Channel coulcl have centributed to the rapjd re
colonization of the dredgedarea by bcnLhicinvertebrates.Althoughthe sedimentsoutsideof
the ferry chaDnelwere not sampled,\!c assumc
that they were similar to thoseremovedfrom the
ferry channel.Ifthe sedirnents
in slumpingchannel
walls had beenconsiderablydiflercnt than those
removedfiom the channel.then the benthosin
the fen)' channelnlay not haverccoveredasrapidly.
Corupltiuntsulmonismay also have migrated
into the dredgedchannelfrom areasmore distant
than the slumpingchannel*alls. Davis (1978)
obseruedthat C. srrlnronisactively nigratecl into
the water colunn in the Columbia River estuary.
Cotophitun rolutator, a related Atlantic species,
hasbcenlbund to swim abovcthebottonrduring
pat ofits life (Hughes1988).lf C'.srl,roals populatiors in the reach of the Columbia River near
the Wahkiakurn County Fetry Channel exhibit
similar behavior,they couldhavebeencaried into
the len1 channelby dver cun'ents.Muir(1990)
lound thatC sahiorrlsrvasoneofthe threemost
abundantorganisnrs
collcctcdin the drifi along
the bottom of the dvel dorvnstreamfi on B onncvillc
Dam.
No si-qnificant
changcsoccurrcdin thebenthic
invcrtebrateconmunity slruclurc.asmcasuredby
H and E. in Wahkiakum CounLyFcrry Channel
as a lesult of the dredgiDgproject. ldeally. all
benthicorganisms
shouldhavebeenidentifiedto
the samctaxonomiclcvcl. pret'erablyspecies.tirr
the comn-runitystructureassessments;
howcvcr,
this was not practicill or ieasiblegiven Lhcfinancial constraintsofthe study.EventhoughdilTcrent
taxonomic levels of identilication were uscd in
calculatingboth H and E. \\'e belie\'eour statlstl
c . r cl o t n p l t i r o r tr 'r c r r r l i rsl i n .e s i m i lr,rl i r x o l o r n i c
ievelswere usedthroughoutthe study.
Our study clearlvdemonstrates
the needfor
al lcasLone relerencearea in environmenlalas\e\\rnenru
\ l d t e d g i l gp | o j e e t . .A l r o . i t i . i m portart to conductsamplingpriof to dredgingin
boththe inpactcd andref'erence
areas.Undenr,'ood
(1992)gocsonc steptirnherand statesthe need
for multiple rcltrcnce rreas in environnental as
\fith samplingbetbreandafter in both
sessrnents.
the impacl and relerenceareas.It is not plactical
or ccononricrllyleasibleto establishmultiplc
referenceareasin nost benthicinveftebrate
studies.
\i'ithout thedatalronl thc rct'erence
area,\\'e\\'ould
not havebeenablc to make accurateconclusions
r r g u r d t n gt h c i n r p i r c,t, 1I h e L l f e d l i n Fl r o i ( ( l o n
tl'rebentl]osin thc Icrry channel. Srnrplescol
lected in the rcfcrcncc area provided a neans of
asscssingnatural variation in the stalding crops
andcommunity stmctule of benthicinvcrtebrates
in a specificreachof the loucr ColunrbiaRiver.
Other researchcrshave noted that benthic inver
tebratepopulalionsin otherreachesof the lower
(Holtonet al. I 98:1.
ColumbiaRivervilr1 scasonallv
\{cCabe and Hinton 1993.Hinton et al. 1995).
In Grals Bay lRKnr 37), Holton et al. (1984)
obsen'ecl
thatCorcplrfurrsa/aronisdensitiesrangcd
from.1,l22orgarisms/nrin July 1gliI to 31.75.1
organisrns/mr
in Februarl'19111.Hinton et al.
Literature Cited
C r l u e . 8 . . a n d U . I I a i . , c l l . 1 i ) q l . V n r n r L bf e f e f e n . em a n L r a l .
PC \ cr\ir)n. relea\e8. Quic k\et Inc.. Ro\emont. Pcnn
D r v i s . J . S . 1 9 1 8 .I ) i e l a c ( i \ i ( ) o l b c n t l i c c N S r | c e n s i n t h e
C o l L r n r b iR
. ri \ e f e d u r f ) . N , l . S l. h c s i s .O r c g o nS l l t t e
L . i \ . . C o n r l l i \ . 1 7 0p p .
H i n t m . S . A . , G . ' 1 l l c c a b e . . l r . . a r x l R . 1 - .E l n m e t t . 1 9 9 5 .
1 $ a l c r r c \ t o r u t i N b e 6 \ e e n N l i l l e fS r n d sx n d P i l l a r
Rock l\land. Co[nnbja Ri!cr: cn\ ironnent|l sur! e)-s.
i 9 9 : - 9 3 . L r . S .D e p . C o n r e r . .\ O A A T c c h .\ { e l n o .
Nllls N\\ FSC-23 -17ft.
H o l l o n .R . L . . D . L . H i g l e i , N L A . B f z e z i n s k i .K . K . J o n e s .
a n d S . l - . \ \ ' i l s o n . l 9 E - 1 .B c n t h i ci r f | u n a o f r h e C o l u n b i r R n e f e s t u r D . F i n a lr e p o n o . t h c b c n f i i c i n
launi sor k Lrnilof lhe ColLrlnbi.rRi\ef Estulr,v Data
De\elopnenl Pfogram. Orcgol Slalc Univ..Cor\ llis.
1 7 9p p . p l u st l p p e n d i c e \ .
HuShe\.It.a;. l9EE. I)j\pcr\Nb
l y b c n l h i ci e n e b f r t e \ : d r e
,r rirr \$imJrlng bchi\iour oi thc anphipod
Cohit)hi Llt |oluitbj.
.1.lVrr. Biol. Assoc. UniLcd
K i l l g d o ' n6 i t : 5 6 55 7 9 .
(1995)notedsignificant(P < 0.05)temporaldif'fcrencesin standingcropsofbenLhicinvertebntes
(total). including C.rro]rllrrrr spp.,in a studv area
belwecn Miller Sandsand Pillar Rock Islancl,
ColumbiaRiver estuarl,(RKrn.10-.12).In our
sludy. densitiesol Corophiwn spp. fluctuated
durilg the cight surveys,rl'ith the lovest overall
densityin July 199,1.
In conclusion,rve detcctcdno signitrcantel
fects (P > 0.05) of the terry channeldrcdging
l r j c \ ' tr r r h e r r t h iicn re r t c b r l t rd: L . n . i l i (o. r c o n t
munity structurctiom the statisticalanalyscsof
the data;however.there appcaredto be a poten
tial dampeningeftect on inveflcbratesin the tery
channelimmcdiatelyatterthe dredging.lnaddi(P > 0.05)
tion.we detected
no signiticanteff'ects
ofthc drcdgingprojecton sedinentnedian grain
sizeor percentvolatilesolids.
Acknowledgements
We thank LawrenceDavis, Roy Pettil. Dcnnis
Umphfies. Donald Grubcr and NathanCook lbr
thcirassistance
in collectingbenthicsanrples
during
this study. Benjanin Sandtirrdprovided advice
on thc statisticalanalysisof the data. Wc thank
R , ' b e r tH o i l r n a nl o r r c r r . u i r r gt h e m l n u . c r i p t .
\!'c appreciatethe cooperationof thc operators
ofthe WahkiakumCountyFenJ dulingour sampling elIbrts.The U.S.Army Corpsof Engineers
provided most of the llnding for this snrd1,.
K l r n . R . r \ . . R . D . t - c d g e r l v o o dr L. n d
A . L . J e n s e n .1 9 8 6 .D i e t
of sublearling chinook s llnon (Ond,th\tuhut
t s h a t \ \ ' 1 ! . h a )i n t h e C o l u m b i a R i \ e r e s t L r . r f a
! nd
changeseffected b! dre 1980 cruplion ol Nlount St.
H e l e n s N o r t h $ . S c i .6 0 ( 3 ) : l 9 i 1 9 6 .
K r c b s .C l .J . 1 9 7 8 . E c o l o g y : t h e e x p c r j n r c l r t ar n
l rly\is of
di\lnbution.rnd rbundamce.Haryer .lnd R,i:trr.\.$
York. 678 pp.
Nlccrbe. G. T. Jr. R. L. Emmeil. \V. D. \,luir. rnd T. H. Blahnr
1 9 8 6 . U l i l i z a t i o no I t h e C o l u m b i aR i l e r c n u , r r ) b l
subvearlrng chirook s.rlnon
\onhr.
Sci.
6i)(l):l l3 I2.1.
\ , l c c a b e .G . T . .J r . .a n dS . A . H r n t o n . 1 9 9 3 .B e n t h i ci n \ e f i e
bmtes and sedimentsin \cgcllted und nonreseiated
h,rbitatsrt three inlenidalareasolthc ColulnbirLRivef
estuary.1992. fir.rl Rep to U.S. Aflnt Corps ol lng
b I L l . S .N a i l . \ 4 a r F i s h .S c r \ . . S e r t t l e .\ \ ' a s h i n g t o.
37 pp.
\4ccabe.Cl.T.. Ji.W D. N,luir.R. L. Em'nert.anclJ.T. Durkin.
I 9 8 3 . I i t c r e l . r t i d s h i p s h e t $ e e nj u v e n i l c\ a l n o n i d s
a.d nonsalmonidlish ir the Columbia llivcr csturry.
F i \ h .B u l l . .t i . S . 8 l ( . 1 ) : 8 1851 6 .
Benthic Invertebratesin a Shrllow Navigation Channcl
125
Nlorlon.J.W 1977.Ecolosicaletlectsof dfedging xnd dredge
s p o i l d i s p o s a l :a l i t c r a r u r er c v i e \ \ . L r . S .F i s h \ \ i l d l .
S e | v . l e c h . P a p . 9 , 1 .l - l p p .
N{un. W D. 1990. N{xcroinlerr.bralc drili abund.rncebcl o $ B o n n e ! i l l eD r m . r n d i r sr e l a l i o nt o j L r \ c | i l cs r l m L )
n x l l o o d h . r b i t s . \ 1 . S . T h e s i \ . P o r t l a n dS l a t c U n i ! . .
Poil.rnd, Oregon. l0 pp.
M u n . \ \ i D . , a n d R . L . E n m e i t . 1 9 8 8 . F o o dh a b i t so f l n i
gfating \alnlonid smolts pas\ing Bonnc!ille Dal1l in
t h e C o i u m b i aR i ! e r . 1 9 8 . 1 .R . g u l . R r ! c r ! : R e s .a n d
NIanrse.2:1 0.
\ l u i r . w ' D . . R L l l n m e t t . a n dR . J . M c c o n n e l l . 1 9 8 8 .D i c r
oi Juvenrl!'and subrdLrltrlite sturleon 1nthe lolver
Columbia Ri\.'crand it\ csluury. Calif. Fish .Lndcame
7.1(I ):19 5,1.
Received28 October1997
AtceptedJor publit:(rtion2 Mdrch 1996
1 2 6 V c C r h e ,H i n t o n l,n d t r r r m . ' t t
l - r n d e r \ r o o dA. . J . 1 9 9 2 . B e r o n d B A C I : d r e d c t c c t i o no l '
e n ! i f o n m e n l arl p a c t so n p o p u l a t i o n isn t b e r e a l ,b u !
\ a i t r b l e . w o r l d .J . E x p .N { a r B i o l . E c o l .l 6 l : 1 ' 1 5 1 7 8 .
li.S.Ann\ Corp.,ol Lnginee$. 1992.\\tstport, Orcgor Pugcl
Isl.rnd \\rashington.WahkiakumCounty Ferry alhan
nel dfati det.Liledproject fepofl. ScclioD 107 stud!.
U.S.Afnr) Cofps ofEngi ecr\. PoalandDistrict. PO.
Bor 29.16.Ponhnd, Oregon. 33 pp. plus rppeDdices.
V a n l ) o l a h .R . f . . D . R . C l d e r ,a n dD . N : . K n o ( . 1 9 8 . 1E
. Ilecrs of drcdgiis ard open-$rrer disfosal oll benthic
nucminveftebratesln a Soulb C.rrolir.r esturrv. ts
r ! L a r i c7s( 1 ) : 2 8 ' 3 7 .