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Submitted 15 March 2017Accepted 19 July 2017Published 16 August 2017

Corresponding authorDeborah A Lichtilichtid12studentsecuedu

Academic editorKristin Hamre

Additional Information andDeclarations can be found onpage 22

DOI 107717peerj3667

Copyright2017 Lichti et al

Distributed underCreative Commons CC-BY 40

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Changes in zooplankton community andseston and zooplankton fatty acid profilesat the freshwatersaltwater interface ofthe Chowan River North CarolinaDeborah A Lichti1 Jacques Rinchard2 and David G Kimmel13

1Department of Biology East Carolina University Greenville NC United States of America2Department of Environmental Science and Biology State University of New York College at BrockportBrockport NY United States of America

3Alaska Fisheries Science Center National Oceanic and Atmospheric Administration Seattle WAUnited States of America

ABSTRACTThe variability in zooplankton fatty acid composition may be an indicator of larvalfish habitat quality as fatty acids are linked to fish larval growth and survival Wesampled an anadromous fish nursery the Chowan River during spring of 2013 inorder to determine how the seston fatty acid composition varied in comparison withthe zooplankton community composition and fatty acid composition during the periodof anadromous larval fish residency The seston fatty acid profiles showed no distinctpattern in relation to sampling time or location The mesozooplankton communitycomposition varied spatially and the fatty acid profiles were typical of freshwaterspecies in April The Chowan River experienced a saltwater intrusion event duringMay which resulted in brackish water species dominating the zooplankton communityand the fatty acid profile showed an increase in polyunsaturated fatty acids (PUFA) inparticular eicosapentaenoic acid (EPA) anddocosahexaenoic acid (DHA) The saltwaterintrusion event was followed by an influx of freshwater due to high precipitation levelsin June The zooplankton community composition once again became dominated byfreshwater species and the fatty acid profiles shifted to reflect this change however EPAlevels remained high particularly in the lower river We found correlations betweenthe seston microzooplankton and mesozooplankton fatty acid compositions Salinitywas the main factor correlated to the observed pattern in species composition andfatty acid changes in the mesozooplankton These data suggest that anadromous fishnursery habitat likely experiences considerable spatial variability in fatty acid profilesof zooplankton prey and that are correlated to seston community composition andhydrodynamic changes Our results also suggest that sufficient prey density as well asa diverse fatty acid composition is present in the Chowan River to support larval fishproduction

Subjects Aquaculture Fisheries and Fish Science Biochemistry Zoology Freshwater BiologyKeywords Zooplankton Fatty acid Estuarine systems Freshwater Seston Community

How to cite this article Lichti et al (2017) Changes in zooplankton community and seston and zooplankton fatty acid profiles at thefreshwatersaltwater interface of the Chowan River North Carolina PeerJ 5e3667 DOI 107717peerj3667

INTRODUCTIONEstuaries are considered important nursery habitat for many ecologically and commerciallyimportant fish and invertebrates (Beck et al 2001 Boesch amp Turner 1984 Sheaves et al2015 Sheaves 2016) Estuaries function as fish nurseries because they are highly productivesupport large planktonic populations across multiple size ranges and fish within estuariesgenerally have higher growth rates compared to other habitats (Beck et al 2001) Hencemany fish have evolved life-history strategies whereby larvae and juvenile stages haveresidency periods in estuaries (McHugh 1967 Boehlert amp Mundy 1988 Beck et al 2001Able 2005Walsh Settle amp Peters 2005)Beck et al (2001) defined nursery habitat as an areathat contributes to higher production of individuals thatmove to juvenile habitat comparedto other areas Higher growth rates of larval fish are possible because of zooplankton preythat are present during their critical transition from yolk sac to free-living feeding larvae(Hjort 1914 Mullen Fay amp Moring 1986 Rulifson et al 1993 Cooper et al 1998 Martinoamp Houde 2010 Binion 2011) However spatial and temporal overlap between predatorsand prey does not completely explain how fish nurseries function mechanistically Thequality of prey can play a major role in determining the effectiveness of a nursery for earlystages of fish

The quality (chemical composition) of zooplankton prey can influence fish growthdevelopment and survival (Fraser et al 1989 Webster amp Lovell 1990 Copeman et al2002 Rossi et al 2006Malzahn et al 2007 Paulsen et al 2014) Fatty acids are chemicallydiverse often incorporated into organisms unmodified and different organisms havedistinct profiles (Dalsgaard et al 2003) Fatty acids are one class of compounds foundin lipids that are particularly important impacting neural and vision development infish (Gulati amp Demott 1997 Muumlller-Navarra et al 2000 Kainz Arts amp Mazumder 2004Masclaux et al 2012) Fatty acids may act as both dietary tracers in the food web andindicators of overall food quality (Iverson et al 2004) The majority of organisms needspecific dietary fatty acids for somatic development and fitness (Masclaux et al 2012)These fatty acids 183ω-3 α-linolenic acid (ALA) and 182ω-6 linoleic acid (LA) arelabeled essential fatty acids because they cannot be directly synthesized by heterotrophicorganisms and must come from the diet (Arts Brett amp Kainz 2009) Polyunsaturated fattyacids (ie 205ω-3 eicosapentaenoic acid (EPA) 226ω-3 docosahexaenoic acid (DHA)and 204ω-6 arachidonic acid (ARA)) are required for all organisms and play a role inhealth and cell function (Dalsgaard et al 2003) Thus an organismsrsquo fatty acid signaturemay indicate dietary consumption and nutritional quality of its prey (Goncalves et al 2012)

Fatty acids are present in estuaries as a result of de novo synthesis by phytoplankton andthe delivery of detrital material of plant origin (Dalsgaard et al 2003) The free-floatingportion of organic and inorganic particles is termed seston (Postel Fock amp Hagen 2000)The organic portion of seston is important because it forms the origin point for thepropagation of fatty acids through the pelagic food web Zooplankton assimilate fattyacids from the seston through direct consumption of phytoplankton cells detritus andorconsumption of microzooplankton that graze phytoplankton or detritus (Wacker amp VonElert 2001 Kainz Arts amp Mazumder 2004 Vargas Escribano amp Poulet 2006) To date

Lichti et al (2017) PeerJ DOI 107717peerj3667 228

studies of the relationship between seston and zooplankton fatty acid composition haveshown variable patterns Persson amp Vrede (2006) demonstrated in laboratory studies thatbroad zooplankton taxonomic groups (cladoceran vs copepods) have different fatty acidprofiles independent of the food source The seston has been correlated to the fatty acidprofile of zooplankton in situ as well (Goulden amp Place 1990 Brett et al 2006 Taipale etal 2009 Gladyshev et al 2010 Ravet Brett amp Arhonditsis 2010) The mismatch of fattyacids in seston to zooplankton has also been shown in many studies (Desvilettes et al 1997Persson amp Vrede 2006 Rossi et al 2006 Smyntek et al 2008) Most marine zooplanktonspecies cannot convert precursor fatty acids and only obtain longer-chained fatty acidsfrom their diet compared to freshwater zooplankton species that can convert precursorfatty acids (Rossi et al 2006 Persson amp Vrede 2006) However it is clear that the fattyacid composition of the seston changes as a result of local conditions eg the salinityand temperature nutrient concentration and the degree of autotrophy or heterotrophyin the system (Farkas amp Herodek 1964 Desvilettes et al 1997 Wacker amp Von Elert 2001Goncalves et al 2012) Therefore combined knowledge of the changing nature of sestonfatty acid composition zooplankton community composition changes and fatty acidprofiles forms a useful base for assessing the quality of fish nursery habitat

Zooplankton community composition in estuaries has been intensely studied andabiotic factors are thought to structure zooplankton communities (Ambler Cloernamp Hutchinson 1985 Orsi amp Mecum 1986 Cervetto Gaudy amp Pagano 1999 Mouny ampDauvin 2002 Kimmel amp Roman 2004 Lawrence Valiela amp Tomasky 2004 Islam Ueda ampTanaka 2005) Zooplankton community composition in temperate estuaries is dominatedby crustaceans in general and copepods and cladocerans in particular (Tackx et al2004 Marques et al 2006 Winder amp Jassby 2011 Chambord et al 2016) Cladoceransare characterized by high levels of EPA and ARA and this is thought to be related to alife history strategy focused on high rates of somatic growth (Persson amp Vrede 2006) Incontrast copepods have higher relative DHA levels because this fatty acid is critical fornervous systemdevelopment (Arts Brett amp Kainz 2009) Copepods featuremore developednervous systems compared to cladocerans and this is a function of active hunting of preymate location and predator avoidance (Dalsgaard et al 2003) Carnivorous crustaceanzooplankton have shown to be richer in PUFAs and this is thought to be related to theirfood source (rotifers and smaller bodied cladocerancopepods compared to phytoplankton)(Arts Brett amp Kainz 2009)

Here we explore the species composition and variability in fatty acid composition of thelower foodweb at the freshwatersaltwater interface of an estuarine fish nursery theChowanRiver North Carolina USA The Chowan River is considered a critical habitat for larvaland juvenile blueback herring (Alosa aestivalis) alewife (A pseudoharengus) collectivelyknown as river herring (NCDMF 2007) The river herring are of interest because theyhave been severely overfished and a moratorium on harvest is in place at various locationsalong the eastern United States including North Carolina (ASMFC 2012) The ChowanRiver also serves as a nursery habitat for American shad (A sapidissima) and striped bass(Morone saxatilis) however the status of the habitat for the latter species is unknown(Greene et al 2009)


The overall goal of our study was to determine if species and fatty acid compositionof the lower food web could be used to indicate habitat quality of an estuarine fishnursery In order to achieve this goal we examined the spatial and temporal variability inspecies composition of microzooplankton and mesozooplankton as well as the fatty acidcomposition of the seston microzooplankton and mesozooplankton during the period oflarval fish residency in the Chowan River Our specific objectives were to determine (1)if differences in the species composition and fatty acid composition were present in thesystem (2) if so were there patterns in species composition and fatty acid composition intime and space (3) if particular species were related to the species composition patterns andif particular fatty acids were related to the fatty acid composition patterns (4) if changesin species and fatty acid composition were related to changes in salinity dynamics (5) ifpatterns in fatty acid composition correlated across trophic levels We hypothesized thatspecies composition would be related to salinity and that fatty acid profiles of micro- andmesozooplankton would relate to species composition and would reflect that of the sestonIf supported this would suggest that the quality of the larval fish forage based on fattyacids could be used to assess fish nursery quality

MATERIALS AND METHODSStudy siteThe Chowan River is one of the largest tributaries that drains into the Albemarle Sound(Figs 1A and 1B) and is the 12th largest river basin in North Carolina (NCDENR 2006)It is mainly a freshwater estuary that experiences intermittent salinity intrusion mainlyin the winter months (Leech Ensign amp Piehler 2009) The Chowan River was classified aslsquolsquonutrient sensitive watersrsquorsquo in 1979 (NCDENR 2006) and has routinely experienced algalblooms and low dissolved oxygen levels (lt30 mg Lminus1) The entire river is classified asa Strategic Habitat Area for larval and juvenile river herring (NCDMF 2007) Samplingtook place south of Holiday Island on a 34 km transect of Chowan River (Fig 1C) Sevenlocations (4 km apart) were sampled between Holiday Island and the river mouth (Fig1C) Sampling occurred on 10ndash11 April 31 May and 25 June 2013 dates that span theresidency for larvae of alewife blueback herring and striped bass For our study we dividedthe river into three sections upper middle and lower The main differences among thesesections were (1) the distance from the Albemarle Sound and (2) the potential influence ofsalinity

Sample collectionWater column properties Vertical profiles of temperature (C) and salinity were measuredwith a conductivity temperature and depth sensor (CTD Yellow Springs InstrumentsCastaway) Water samples were collected at a depth of 3 m with a Niskin water sampler

Zooplankton Water depths ranged from 527 to 756 m during zooplankton samplingTwo horizontal net tows weremade with 05m diameter nets of two differentmesh sizes (60and 200 microm) Two mesh sizes were used in order to generate an adequate representationof the zooplankton for the size range gt60 microm The zooplankton samples between 60 and


Figure 1 The overview of Albemarle Sound in North Carolina (A) The close up view of the locationfor twomain tributaries (Chowan and Roanoke Rivers) and the Albemarle Sound in North Carolina(B) The three sections used to collect zooplankton on the Chowan River (C) Map data ESRI HEREDeLorme MapmyIndia OpenStreetMap contributors GIS user community


200 microm are designated microzooplankton and the gt200 microm zooplankton samples aredesignated mesozooplankton throughout the remainder of the paper The zooplanktonnet was towed obliquely through the water for 1 min (species composition) and 2 min(fatty acid composition) at an average boat speed of 075 m sminus1 The volume filteredwas calculated using the volume of a cylinder (V = πr2L) where r was the radius ofthe plankton net (025 m) and L was determined using the boat speed (m sminus1) and thetow time (s) Each identification and count sample depending on mesh size was filteredthrough a 60 or 200 microm filter and zooplankton for composition were preserved in a 120mL glass jar with 10 ml of 10 buffered formaldehyde sucrose and filtered water Theaddition of sucrose to the formalin helps to reduce ballooning of cladoceran bodies andinflation of their carapace (Haney amp Hall 1973) The 60 microm sample had a half tablet ofAlka Seltzer added to keep rotifers from pulling in critical body parts (legs and arms) toease identification (Chick et al 2010) The zooplankton samples for fatty acid analysis werecollected at seven sites on the Chowan River for April and June and three sites in MayDue to limitations related to sampling preparation in May a subset of the field sites wassampled for fatty acid analyses The zooplankton samples for fatty acids were placed in a1000 mL plastic container on ice and processed in the laboratory

Laboratory processingZooplankton identification Samples were filtered through a sieve (60 or 200 microm) toremove the sugar formalin solution and then added to a beaker with a known volume ofwater A total of three subsamples (2 mL per subsample for microzooplankton and 5 mLper subsample for mesozooplankton) were analyzed for community composition usinga Hensen-Stempel pipette Organisms were identified using a dissecting microscope andenumerated using aWard counting wheel The zooplankton were identified to genus exceptfor the freshwater copepods that were identified to order Copepod nauplii were groupedtogether because identification can be difficult at this stage (Johnson amp Allen 2012) If aspecies in a subsample comprised greater than 500 individuals then that species was notcounted for the other two subsamples Species abundances (A) were determined using theequation A=As(VtVminus1s ) where As is the number of individuals in the subsample Vt isthe total volume of water in the beaker and Vs is the volume of the subsample

Lipid and fatty acid samples The water samples (300 mL) were concentrated on a 07 micromWhatmanTM GFF filter (47 mm diameter) and stored at minus80 C until ready to processwhich constituted the seston material The zooplankton samples were filtered through60 and 200 microm sieves stacked to collect species based on size Each sample was visuallyanalyzed to determine the dominant species with a dissecting microscope and detritus andphytoplankton were removed The samples were concentrated on a GFF filter (47 mmdiameter) by mesh size (60 200 microm) and stored at minus80 C until ready to process

Total lipids were extracted with chloroform-methanol (21 vv) containing 001butylated hydroxytoluene as an antioxidant (Folch Lees amp Sloane Stanley 1957) Theorganic solvent was evaporated under a stream of nitrogen and lipid concentrationdetermined gravimetrically Transmethylation of fatty acids was done according to the


method described byMetcalfe amp Schmitz (1961) A known amount of nonadecanoate acid(190) dissolved in hexane at a concentration of 8 mg mlminus1 (Nu Check Prep Inc) wasadded as internal standard The fatty acid methyl esters (FAME) were separated by gaschromatography (Agilent 7890A Gas Chromatograph Agilent Technologies Inc SantaClara CA USA) using a 7693mass spectrometer detector (Agilent Technologies Inc SantaClara CA USA) a capillary column (OmegawaxTM 250 fused silica capillary column 30mmtimes 025 mm and 025 mm film thickness Supleco Rcopy) and a 7890A autoinjector (AgilentTechnologies Inc) Helium was used as the carrier gas at a flow of 13 ml minminus1 and theinjection volume was 2 mL Initial temperature of the oven was 175 C for 26 min whichwas increased to 205 C by increments of 2 C minminus1 then held at 205 C for 24 minThe source and analyzer for the mass spectrometer was set at 230 C The individualfatty acid methyl esters were identified by comparing the retention times of authenticstandard mixtures (FAME mix 37 components Supleco) and quantified by comparingtheir peak areas with that of the internal standard (Czesny amp Dabrowski 1998) The resultsof individual fatty acid composition are expressed in percentage of total identified FAME

Statistical analysis We performed a series of multivariate analyses to address our specificobjectives We used PERMANOVA a part of the PRIMER 6 statistical software package(Clarke amp Gorley 2006) to test for overall differences between the microzooplanktonand mesozooplankton community composition and fatty acid profiles of sestonmicrozooplankton and mesozooplankton PERMANOVA is a non-parametric techniquerelated to ANOVA but uses permutations and fewer assumptions compared to thetraditional ANOVA approach (Anderson 2001) As such it is particularly well suited tomultivariate data sets that violate the traditional assumptions of ANOVA and also havelow sample sizes as was our case (Anderson 2001)

If PERMANOVAdetected differences we then generated separate Bray-Curtis similaritymatrices for microzooplankton species composition (60 microm mesh) mesozooplanktonspecies composition (200 microm mesh) seston fatty acid composition microzooplanktonfatty acid composition and mesozooplankton fatty acid composition A separate clusteranalysis was performed using PRIMER 6 in order to reveal patterns over time and spacefor each similarity matrix Each individual sample was associated with a location in theriver (upper middle lower) and month (April May June) and these labels were used forvisualization of samples in the cluster dendrogram Next a similarity percentage analysis(SIMPER) test was used to compare similarities within groups and determine the speciesor fatty acids that contributed to each grouping from the cluster analysis (Clarke amp Gorley2006) The SIMPER test was set at 70 cumulative contribution

We then wanted to determine if salinity and temperature were related to the observedpatterns andwe used redundancy analysis for this purpose (Legendre amp Legendre 1998) Theredundancy analysis was carried out in the R environment (R v323 R Core DevelopmentTeam 2015) using rda function in the vegan package (Oksanen et al 2017) Finally weused a Mantel matrix comparison to correlate fatty acid profiles between the three groups(seston microzooplankton and mesozooplankton) The mantelrtest function in the ade4


Table 1 Results of SIMPER analysis for each group all the zooplankton species that contributed com-munity composition and their corresponding values in are givenDash marks represent species thatwere not included in the contribution of 70

Microzooplankton Mesozooplankton

Group 1 Group 2 Group 3 Group 4 Group 5

Overall similarity 9118 8018 8439 5716 5252

Species Percent composition Percent composition

Bosminidae ndash ndash 1726 3425 1220Leptodora spp ndash ndash ndash ndash 2180Calanoida ndash ndash ndash 3332 2609Cyclopoida ndash ndash ndash 1024 907Acartia spp ndash ndash 7466 ndash ndashCopepod nauplii 1060 4161 ndash ndash ndashRotifer 8647 5046 ndash ndash ndash

package (Oksanen et al 2017) in the R environment (R v323 R Core Development Team2015) was used

RESULTSSalinity and temperatureSalinity was near zero (002ndash004) throughout the river in April During May salinities inthe upper river remained low (007) but the water column became stratified in the middleand lower river with salinities ranging from 028ndash166 The river returned to freshwater(004ndash008) again in June due to a tropical storm that brought heavy rains for a two-weekperiod North Carolina experienced the second wettest June since 1895 with rainfall thatranged from 152 to 1905 cm in the study area (Hiatt 2013) Water temperatures increasedduring the study period April (157plusmn 11 C)May (240plusmn 10 C) and June (262plusmn 03 C)

Zooplankton community compositionThere were significant differences between the overall microzooplankton and mesozoo-plankton community composition (PERMANOVA p= 0001) Microzooplankton couldbe separated into two distinct groups by cluster analysis at 65 similarity (Fig 2A) Group1 consisted of the vast majority of the samples collected across April May and Junethroughout the river (Fig 2A) Group 2 consisted of two samples collected in the middleand lower river in June (Fig 2A) Both groups were dominated by rotifers and copepodnauplii but group 2 had a higher contribution of copepod nauplii (Fig 2B and Table 1)

Three groups of mesozooplankton were differentiated at 50 similarity using clusteranalysis (Fig 3A) Group 3 consisted of samples from the May collection only Group4 consisted of a mixture of April and June samples in primarily the upper and middleriver and Group 5 consisted of one April upper site May upper river section and Junesamples throughout the river (Fig 3A) Group 3 mesozooplankton percent compositionwas dominated by Acartia spp with a minor contribution by Bosminidae Group4 consisted primarily of equivalent percentages of Cyclopoida and Bosminidae and


Figure 2 The twomicrozooplankton community composition groups from cluster analysis (A) at 65similarity The meanmicrozooplankton community composition (plusmnSD) for the two groups fromcluster analysis (B)


Figure 3 The three mesozooplankton community composition groups from cluster analysis (A) at50 similarity The meanmesozooplankton community composition (plusmnSD) for the three groupsfrom cluster analysis (B)


Table 2 Results of SIMPER analysis for each group the fatty acids that contributed to the differences in fatty acid profile and theircorresponding values in are givenDash marks represent fatty acids that were not included in the contribution of 70 Group G had a samplesize lt2

Seston Microzooplankton Mesozooplankton

Group A Group B Group C Group D Group E Group F Group G Group H Group I Group J

Overall similarity 6640 7232 6434 8488 9249 8105 NA 8142 8942 8489

Fatty acids Percent composition Percent composition Percent composition

161ω-7 312 653 ndash ndash ndash 798 ndash 953 ndash 851181ω-9 704 227 242 3163 1346 ndash 1701 1058 ndash ndash182ω-6 ndash ndash ndash 1215 ndash ndash ndash ndash ndash ndash183ω-3 (ALA) 237 ndash 333 ndash 843 680 ndash 614 1065 ndash184ω-3 ndash ndash ndash ndash 1029 ndash ndash ndash 705 ndash205ω-3 (EPA) ndash 155 244 ndash 1172 991 ndash 1124 1384 1640226ω-3 (DHA) ndash ndash 187 ndash ndash 945 ndash ndash 1011 1658

Group 5 mesozooplankton percent community composition was characterized by higherpercentages of Leptodora spp and Calanoida (Fig 3B and Table 1)

Fatty acid compositionA total of 24 specific fatty acids were found in all samples (Tables A1ndashA3) Fatty acidswere first separated into broad categories saturated fatty acids (SFA) monounsaturatedfatty acids (MUFA) and polyunsaturated fatty acids (PUFA) (Fig 4A) Seston had ahigher percent of SFA and lower percent of MUFA and PUFA compared to micro- andmesozooplankton (Fig 4A)Mesozooplankton andmicrozooplanktonhad a similar percentcomposition of SFA MUFA and PUFA (Fig 4A) There were eight dominant fatty acidsfound in all the samples but the percent composition varied (Fig 4B) The most commonSFA was palmitic acid (160) the most common MUFAs were palmitoleic acid (161ω-7)and oleic acid (181ω-9) and the most common PUFAs were ALA 184ω-3 EPA andDHA (Fig 4B Tables A1ndashA5) A comparison of MUFAs and PUFAs among the seston andzooplankton showed that seston had the lowest overall percentages of MUFAs and PUFAs(PERMANOVA p= 0001 Fig 4B) There was a difference between the microzooplanktonfatty acid profile and the mesozooplankton fatty acid profile (PERMANOVA p= 0025)The microzooplankton fatty acid profile was characterized by a higher percentage of181ω-9 compared to the other MUFAs and PUFAs In contrast the mesozooplankton hadthe highest percent composition attributed to two PUFAs EPA and DHA (Fig 4B)

SestonThree groups were designated at 60 similarity using cluster analysis for the seston fattyacid composition (Fig 5A) The groups showed no distinct pattern in terms of samplingtime or location (Fig 5A) Seston fatty acid composition of Group A was characterizedby 181ω-9 161ω-7 ALA and EPA Group B by 161ω-7 181ω-9 182ω-6 and EPAand Group C had similar percentage composition of MUFAs and PUFAs except 182ω-6(Fig 5B and Table 2)


Figure 4 The mean (plusmnSD) saturated (SFA) monounsaturated (MUFA) and polyunsaturated (PUFA)fatty acid composition () for the seston microzooplankton andmesozooplankton (A) The meanfatty acid composition (plusmnSD) for the seston microzooplankton andmesozooplankton (B)


Figure 5 The three seston fatty acid composition groups from cluster analysis (A) at 60 similarityThe mean seston fatty acid composition (plusmnSD) for the three groups from cluster analysis (B)

MicrozooplanktonThree groups were designated at 70 similarity using cluster analysis for themicrozooplankton fatty acid composition (Fig 6A) The groups segregated temporallywith Group D and E consisting of April samples only and Group F consisted of May andJune samples only (Fig 6A) The Group D fatty acids were dominated by 181ω-9 and toa lesser extent 182ω-6 Group E showed similar percent composition among the fattyacids with higher percentages of 181 ω-9 and EPA and Group F also had similar percent


Figure 6 The three microzooplankton fatty acid composition groups from cluster analysis (A) at 60similarity The meanmicrozooplankton fatty acid composition (plusmnSD) for the three groups fromcluster analysis (B)

composition of fatty acids however the PUFAs EPA and DHA had significant contribution(Fig 6B and Table 2)

MesozooplanktonFour groups were designated by cluster analysis at 77 similarity for the mesozooplanktonfatty acid composition (Fig 7A) Groups G and I consisted of April samples only whereasGroup J consisted of May and June samples only (Fig 7A) Group H showed spatial


Figure 7 The four mesozooplankton fatty acid composition groups from cluster analysis (A) at 60similarity The meanmesozooplankton fatty acid composition (plusmnSD) for the four groups fromcluster analysis (B)

separation consisting of primarily upper river locations across all of the months (Fig 7A)The Group G and H fatty acids were dominated by 181ω-9 Group 8 by 161 ω-7 181ω-9and EPA Group I had similar percentages of fatty acids with ALA DHA and EPA havinghigher percentages and Group J had DHA and EPA as dominant components of the fattyacids (Fig 7B and Table 2)

Redundancy analysis and Mantel matrix correlationsSalinity was the main factor found to be correlated to observed patterns in the speciescomposition of both microzooplankton and mesozooplankton (Redundancy p= 0004)


However salinity was not correlated to changes in the seston (Redundancy p= 0490) ormicrozooplankton (Redundancy p= 027) fatty acid profiles Salinity was associated withthe changes in the mesozooplankton fatty acid profiles (Redundancy p= 0034) Sestonfatty acid profiles were correlated to the microzooplankton fatty acid profiles (p= 0013)based on the Mantel matrix comparison but not correlated to the mesozooplankton fattyacid profiles (p= 0340) The microzooplankton fatty acid profiles were correlated to themesozooplankton fatty acid profiles (Mantel p= 0059)

DISCUSSIONWe found temporal and spatial differences in the species and fatty acid composition of thelower food web that were mainly related to a salinity intrusion that occurred during thestudy period duringMay Prior to the salinity intrusion larval fish would have encountereda freshwater plankton assemblage that was dominated by rotifers Bosminidae and cylopoidcopepods throughout the river This assemblage was proportionally higher in EPA relativeto DHA During the salinity intrusion the microzooplankton remained dominated byrotifers however the mesozooplankton community became dominated by the copepodAcartia spp Concurrently the proportion of DHA increased and remained elevated intoJune particularly in the middle and lower river The intrusion of saline water increasedthe overall proportion of omega-3 fatty acids in the river presumably due to the increasedfraction of micro- and mesozooplankton feeding on a more marine-like phytoplanktonbased food web and this signal propagated through the food web Additionally we observedthat FA appeared to be incorporated relatively unchanged inmicro andmesozooplankton interms of relative composition however MUFA and PUFA percent compositions increasedin zooplankton relative to seston This suggested thatMUFA and PUFA are bioaccumulatedat higher trophic levels as seen in other studies (Persson amp Vrede 2006 Gladyshev et al2010 Ravet Brett amp Arhonditsis 2010 Burns Brett amp Schallenberg 2011) Overall the FAcomposition of the food web indicated that the Chowan River is likely to provide nutritionin terms of FA composition for larval fish growth and development This is based on thepresence of higher chain (gt20 carbons) PUFAs present in themesozooplankton throughoutthe nursery

The seston fatty acid composition consisted mainly of saturated fatty acids Seston fromfreshwater and estuarine systems typically has a large percentage of SFA and this fractionhas been attributed to detrital input as opposed to originating from phytoplankton(Persson amp Vrede 2006Gladyshev et al 2010 Ravet Brett amp Arhonditsis 2010 Burns Brettamp Schallenberg 2011 Goncalves et al 2012) Muumlller-Navarra et al (2004) and Bec et al(2010) analyzed seston and found phytoplankton only explained 27 of variance in FAcomposition and concluded that detritus and heterotrophic organisms also needed tobe considered Bec et al (2010) therefore concluded that the seston can affect the fattyacid profiles of higher organisms but may not relate individual groups of phytoplanktonor microzooplankton This agreed with our findings as seen in the reduced correlationsbetween seston and the mesozooplankton

We did not examine the seston composition directly by counting phytoplankton cellsor examining pigment concentrations thus we were unable to attribute the origin of


particular fatty acids to phytoplankton or other sources However we were able to usethe available literature to identify potential indicators of fatty acid origin The top fourfatty acids by percent composition varied by group but 161ω-7 181ω-9 182 ω-6 andALA were the most prevalent Potential phytoplankton sources for these fatty acids may bediatoms which have been shown to have increased 161ω-7 and EPA in both freshwaterand marine systems (Napolitano et al 1997 Dalsgaard et al 2003 Boschker Krombamp ampMiddelburg 2005 Arts Brett amp Kainz 2009 Bec et al 2010) and we observed this occurredin May and June coincident with the salinity increase Green algae (Chlorophytes) havebeen shown to possess higher proportions of 182ω-6 and ALA and 184ω-3 (Ahlgren etal 1990 Dalsgaard et al 2003 Boschker Krombamp ampMiddelburg 2005 Masclaux et al2012 Strandberg et al 2015) Fatty acids corresponding to these phytoplankton groupswere observed during April throughout the river and June in the middle and upper riverOne other source of seston FA may have been present pine pollen which is found inlarge quantities during spring Pine pollen is transported to freshwater systems via aerialdeposition and floats at the surface and the pine pollen fatty acid profile has a high percentcomposition of 181ω-9 and 182ω-6 (Masclaux et al 2013) which can be observed in oursamples Obviously seston FA are a mixture of multiple sources thus the variability seenacross the groups identified by the cluster analysis would be expected

The microzooplankton fatty acid profiles were different throughout the samplingperiod with a change from decreased omega-3s to increased omega-3s in the system Thissuggests a switch in microzooplankton diet had occurred over the sampling period andtwo pathways appear to be present during the study The April microzooplankton fattyacid profiles for all river sections had a high percentage of 181ω-9 and 182ω-6 suggestingthat the microzooplankton could be consuming either terrestrial material or chlorophytesduring this time Two sites in April had an increase in omega-3 fatty acids (ALA 184 ω-3EPA DHA) and this would suggest a different dietary pathway that was reduced in SFAperhaps consisting of either smaller microzooplankton such as ciliates or phytoplanktonsuch as diatoms andor dinoflagellates (Park amp Marshall 2000 Gladyshev et al 2010) Thecommunity was dominated by rotifers during this time and communities high in rotiferabundance have been shown to closely reflect the seston composition (Gladyshev et al2010) Themicrozooplankton fatty acid profiles inMay and June at all river locations had anincrease in 161ω-7 and omega-3s (ALA EPA and DHA) These changes can be correlatedto the likely increase in diatoms and dinoflagellates from the saltwater intrusion event Thechanges in June could be the increase in copepod nauplii of Calanoid copepods and thepresence of dinoflagellates and diatoms even when the system returned to freshwater Ourresults are similar to systems where the phytoplankton composition was represented bydiatoms and dinoflagellates by having increased 161ω-7 and PUFAs (Muumlller-Navarra etal 2000 Dalsgaard et al 2003 Gladyshev et al 2010 Ravet Brett amp Arhonditsis 2010)

The mesozooplankton fatty acid profiles throughout the river in April and in the upperriver in May and June were defined by higher percentages of 161ω-7 181ω-9 ALAEPA and DHA and mixed mesozooplankton community consisting of cladoceran andcopepods These fatty acids profiles are similar to those found in freshwater systems thathave a mixed zooplankton composition (Persson amp Vrede 2006 Arts Brett amp Kainz 2009


Kainz et al 2009 Gladyshev et al 2010 Burns Brett amp Schallenberg 2011 Masclaux et al2012) Cladocerans have low or no DHA compared to copepods and high EPA levelshave been shown to correlate with the high somatic growth rates of cladoceran (Persson ampVrede 2006) A saltwater intrusion changed the mesozooplankton species composition inMay resulting in numerical dominance by Acartia spp in the lower and middle sectionsof the river Acartia spp is the dominant copepod species in temperate estuarine systems(Ambler Cloern amp Hutchinson 1985 Orsi amp Mecum 1986 Cervetto Gaudy amp Pagano1999 Mouny amp Dauvin 2002 Kimmel amp Roman 2004 Lawrence Valiela amp Tomasky2004 Islam Ueda amp Tanaka 2005) The mesozooplankton fatty acid profiles in May wererepresented by 161ω-7 EPA and the highest observed percentages of DHA This is clearlya reflection of the dominance of Acartia spp in the system and a diet primarily consistingof marine algae higher in omega-3 FAs (Stottrup Bell amp Sargent 1999 Persson amp Vrede2006 Arts Brett amp Kainz 2009 Kainz et al 2009 Gladyshev et al 2010 Masclaux et al2012) Mesozooplankton fatty acid percent composition in June at the lower and middlesite remained similar to that observed in May despite the species composition havingreturned to a mix of cladocerans and copepods This suggests that physical shifts in thesystem that result in seston changes may persist in the system despite shifts in zooplanktoncommunity composition

The relevance of the food web fatty acid composition can be determined by examiningthe potential feeding behavior of larval fish within the Chowan River nursery Alewife andblueback herring start feeding on smaller cladocerans and copepods at about 6 mm totallength (Mullen Fay amp Moring 1986) Binion (2011) reported that river herring at 6 mmnotochord length had a maximum gape width of 400 microm and estimated maximum preysize of 200 microm which would result in mesozooplankton being an important food resourceIn the Connecticut River the diet for blueback herring were dominated by rotifers for fish5ndash12 mm Bosminidae for fish 12ndash16 mm and cyclopoid copepods for fish gt16 mm intotal length (Crecco amp Blake 1983) Based on these dietary studies the larval and juvenileriver herring would be feeding across the size range of zooplankton prey that we sampledhowever fish would be consuming primarily microzooplankton early in the year (April)and mesozooplankton later in the season (May and June) In April two pathways for FApropagation were present in themicrozooplankton Thus fish feeding during this timemayexperience variability in the quality of the microzooplankton prey in terms of percentage ofPUFAs Larval fish need PUFAs (ALA EPA and DHA) for growth visual acuity survivaland development of normal pigmentation (Bell et al 1995 Bell amp Sargent 1996 RainuzzoReitan amp Olsen 1997 Sargent et al 1999 Rossi et al 2006) The shift to larger prey laterin the year (May and June) resulted in a change in prey quality as the relative percentageof EPA and DHA increased This was the result of a salinity intrusion into the middle andlower reaches of the estuary that was associated with dominance of the cladoceran Acartiaspp and a significant increase in DHA and EPA This could allow larval and juvenile fishto consume prey with a higher proportion of PUFAs It is unknown if river herring canelongate precursor FA into PUFAs Even if fish can convert precursor FA larval fish couldnot receive all nutritional need for those fatty acids (Agaba et al 2005) The larval fishwould not have to use energy for the conversion and could continue to put energy into


growth (Wacker amp Von Elert 2001 Rossi et al 2006) This allows the larval fish to surviveand grow past the critical period

The fish nursery present in the lower Chowan River may undergo significant changesduring the critical time of larval fish growth and our results demonstrate how changes inthe seston community may propagate through the food web The results also highlight thatadditional information concerning the fatty acid composition of the zooplankton prey basefor larval fish can provide insight into habitat quality our stated goal Sheaves et al (2015)pointed out the need to expand the nursery habitat concept to include relevant ecosystemprocesses particularly resource dynamics This research begins to explore the mechanismsthat allow nursery habitat to function We plan further research to investigate the linkagebetween the seston community fatty acid composition the zooplankton community fattyacid composition and larval fish to determine how lower food web variability relates tolarval fish condition and survival

ACKNOWLEDGEMENTSI would like to thank S Lichti C Krahforst J Osborne A Powell M Baker and E Diaddoriofor help in the field collection I would like to thank L Stratton C Kolb and R Pattridgefor help in Dr Jacques Rinchardrsquos lab in processing my fatty acid samples I would like tothankDr Ariane Peralta for help with the improved statistical analysis and two anonymousreviewers for comments which helped to improve the manuscript

APPENDIX

Table A1 Mean fatty acid composition (plusmnstandard deviation) (percentage of total fatty acidsdetected) of seston from the Chowan River by group

Seston group

A (8) B (5) C (4)

140 66plusmn 18 112plusmn 51 76plusmn 10150 15plusmn 15 13plusmn 04 17plusmn 03160 477plusmn 55 540plusmn 51 508plusmn 44170 23plusmn 04 27plusmn 07 26plusmn 02180 142plusmn 56 97plusmn 12 114plusmn 25200 04plusmn 03 03plusmn 01 04plusmn 02sum

SFA 727 792 740161ω-9 12plusmn 10 13plusmn 06 16plusmn 07161ω-7 31plusmn 19 63plusmn 33 21plusmn 19181ω-9 70plusmn 18 23plusmn 08 24plusmn 03181ω-7 03plusmn 02 01plusmn 02 01plusmn 01201 01plusmn 00 01plusmn 00 02plusmn 01sum

MUFA 117 101 64

(continued on next page)


Table A1 (continued)

Seston group

A (8) B (5) C (4)

182ω-6 29plusmn 42 06plusmn 06 08plusmn 12183ω-3 24plusmn 14 09plusmn 05 33plusmn 13184ω-3 07plusmn 11 01plusmn 01 17plusmn 14202ω-6 05plusmn 04 02plusmn 02 07plusmn 05203ω-6 04plusmn 01 04plusmn 03 03plusmn 02204ω-6 09plusmn 06 08plusmn 04 08plusmn 05203ω-3 06plusmn 03 04plusmn 03 11plusmn 06204ω-3 06plusmn 14 05plusmn 03 23plusmn 19205ω-3 16plusmn 11 16plusmn 04 24plusmn 17225ω-6 07plusmn 05 08plusmn 08 12plusmn 06225ω-3 08plusmn 06 07plusmn 06 12plusmn 07226ω-3 14plusmn 11 11plusmn 06 19plusmn 10sum

PUFA 135 81 177

NotesSFA saturated fatty acids MUFA monounsaturated fatty acids PUFA polyunsaturated fatty acids

Table A2 Mean fatty acid composition (percentage of total fatty acids detected) of microzooplankton(lt60microm) from the Chowan River by groups

Microzooplankton Groups

D (5) E (2) F (8)



MUFA 354 173 166182ω-6 122plusmn 16 69plusmn 09 28plusmn 12183ω-3 29plusmn 13 84plusmn 13 70plusmn 17184ω-3 32plusmn 23 103plusmn 15 28plusmn 07202ω-6 04plusmn 01 05plusmn 01 03plusmn 01203ω-6 01plusmn 01 01plusmn 00 02plusmn 01204ω-6 06plusmn 07 04plusmn 01 32plusmn 05





D (5) E (2) F (8)

203ω-3 03plusmn 01 10plusmn 02 04plusmn 01204ω-3 13plusmn 04 28plusmn 01 21plusmn 03205ω-3 50plusmn 20 117plusmn 14 99plusmn 20225ω-6 02plusmn 02 10plusmn 01 23plusmn 09225ω-3 02plusmn 02 02plusmn 01 19plusmn 11226ω-3 21plusmn 15 56plusmn 03 98plusmn 32sum

PUFA 285 489 427


Table A3 Mean fatty acid composition (plusmnstandard deviation) (percentage of total fatty acidsdetected) of mesozooplankton from the Chowan River by group

Mesozooplankton groups

G (1) H (5) I (5) J (5)

140 45 54plusmn 09 52plusmn 11 51plusmn 11150 11 11plusmn 04 07plusmn 00 09plusmn 01160 297 244plusmn 26 195plusmn 13 220plusmn 15170 13 14plusmn 04 10plusmn 01 14plusmn 03180 112 77plusmn 12 51plusmn 03 68plusmn 07200 04 02plusmn 00 02plusmn 01 01plusmn 01sum

SFA 482 402 317 363161ω-9 03 09plusmn 02 09plusmn 04 08plusmn 04161ω-7 41 95plusmn 22 62plusmn 22 86plusmn 22181ω-9 170 106plusmn 43 64plusmn 12 40plusmn 14181ω-7 21 39plusmn 17 24plusmn 04 30plusmn 11201 03 01plusmn 01 03plusmn 01 02plusmn 01sum

MUFA 238 250 162 166182ω-6 42 30plusmn 09 51plusmn 06 22plusmn 07183ω-3 29 61plusmn 21 107plusmn 15 51plusmn 19184ω-3 14 24plusmn 08 71plusmn 12 22plusmn 04202ω-6 02 02plusmn 01 04plusmn 01 02plusmn 00203ω-6 01 01plusmn 00 01plusmn 00 01plusmn 00204ω-6 37 42plusmn 15 21plusmn 06 25plusmn 12203ω-3 02 02plusmn 01 05plusmn 03 02plusmn 01204ω-3 08 06plusmn 03 12plusmn 06 08plusmn 03205ω-3 59 112plusmn 24 138plusmn 09 162plusmn 06225ω-6 04 04plusmn 02 08plusmn 02 18plusmn 08225ω-3 04 03plusmn 02 04plusmn 02 06plusmn 03226ω-3 73 57plusmn 29 101plusmn 28 151plusmn 73sum

PUFA 275 344 523 470



ADDITIONAL INFORMATION AND DECLARATIONS

FundingThis work was funded by NSF Grant DEB-0951414 to DG Kimmel The funders had norole in study design data collection and analysis decision to publish or preparation of themanuscript

Grant DisclosuresThe following grant information was disclosed by the authorsNSF DEB-0951414

Competing InterestsThe authors declare there are no competing interests

Author Contributionsbull Deborah A Lichti conceived and designed the experiments performed the experimentsanalyzed the data contributed reagentsmaterialsanalysis tools wrote the paperprepared figures andor tablesbull Jacques Rinchard conceived and designed the experiments performed the experimentscontributed reagentsmaterialsanalysis tools reviewed drafts of the paperbull David G Kimmel conceived and designed the experiments analyzed the datacontributed reagentsmaterialsanalysis tools reviewed drafts of the paper

Data AvailabilityThe following information was supplied regarding data availability

The raw data has been supplied as a Supplementary File

Supplemental InformationSupplemental information for this article can be found online at httpdxdoiorg107717peerj3667supplemental-information

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Goncalves AMM Azeiterio UM Pardal MA De TrochM 2012 Fatty acid profilingreveals seasonal and spatial shifts in zooplankton diet in a temperate estuaryEstuarine Coastal and Shelf Science 10970ndash80 DOI 101016jecss201205020

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Greene KE Zimmerman JL Laney RW Thomas-Blate JC 2009 Atlantic coast diadro-mous fish habitat a review of utilization threats recommendations for conservation


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Gulati RD DemottWR 1997 The role of food quality for zooplankton remarks onthe state-of-the-art perspectives and priorities Freshwater Biology 38753ndash768DOI 101046j1365-2427199700275x

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Hiatt A 2013 Climate Summary June 2013 State Climate Office of North CarolinaAvailable at httpnc-climatencsuedu climateblogid=28 (accessed on 15 September2013)

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KainzM Arts MT Mazumder A 2004 Essential fatty acids in the planktonic food weband their ecological role for higher trophic levels Limnology and Oceanography491748ndash1793 DOI 104319lo20044951784

KainzMJ PergaMT Arts Mazumder A 2009 Essential fatty acid concentration ofdifferent seston sizes and zooplankton a field study of monomictic coastal lakesJournal of Plankton Research 31635ndash645 DOI 101093planktfbp015

Kimmel DG RomanMR 2004 Long-term trends in mesozooplankton abundance inChesapeake Bay USA influence of freshwater inputMarine Ecology Progress Series26771ndash83 DOI 103354meps267071

Lawrence D Valiela I Tomasky G 2004 Estuarine calanoid copepod abundance inrelation to season salinity and land-derived nitrogen loading Waquoit Bay MAEstuarine Coastal and Shelf Science 61547ndash557 DOI 101016jecss200406018

Leech D Ensign S Piehler M 2009 Zooplankton Assessment Project (ZAP) reassessingprey availability for river herring in the Chowan River Basin- Year 2 North CarolinaSea Grant Report FRG 08-EP-06 09-EP-03

Legendre P Legendre L 1998Numerical ecology 2nd edition Amsterdam ElsevierMalzahn AM Aberle N Clemmesen C BoersmaM 2007 Nutrient limitation of

primary producers affects planktivorous fish condition Limnology and Oceanography522062ndash 2071 DOI 104319lo20075252062

Marques SC Azeiteiro UMMarques JC Neto JM Pardal UM 2006 Zooplankton andicthyoplankton communities in a temperate estuary spatial and temporal patternsJournal of Plankton Research 28297ndash312


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Masclaux H Bec A KainzMJ Perriere F Desvilettes C Bourdier G 2012 Accumula-tion of polyunsaturated fatty acids by cladocerans effects of taxonomy temperatureand food Freshwater Biology 57696ndash703 DOI 101111j1365-2427201202735x

Masclaux H PergaME KagamiM Desvilettes C Bourdier G Bec A 2013Howpollen organic matter enters freshwater food web Limnology and Oceanography581185ndash1195 DOI 104319lo20135841185

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Muumlller-Navarra DC Brett MT Park S Chandra S Ballantyne AP Zorita E GoldmanCR 2004 Unsaturated fatty acid content in seston and tropho-dynamic coupling inlakes Nature 42769ndash72 DOI 101038nature02210

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Webster CD Lovell RT 1990 Response of striped bass larvae fed brine shrimp fromdifferent sources containing different fatty acid compositions Aquaculture 9049ndash61DOI 1010160044-8486(90)90282-R

Winder M Jassby AD 2011 Shifts in zooplankton community structure implicationsfor food web processes in the upper San Francisco Estuary Estuaries and Coasts34675ndash690 DOI 101007s12237-010-9342-x


INTRODUCTIONEstuaries are considered important nursery habitat for many ecologically and commerciallyimportant fish and invertebrates (Beck et al 2001 Boesch amp Turner 1984 Sheaves et al2015 Sheaves 2016) Estuaries function as fish nurseries because they are highly productivesupport large planktonic populations across multiple size ranges and fish within estuariesgenerally have higher growth rates compared to other habitats (Beck et al 2001) Hencemany fish have evolved life-history strategies whereby larvae and juvenile stages haveresidency periods in estuaries (McHugh 1967 Boehlert amp Mundy 1988 Beck et al 2001Able 2005Walsh Settle amp Peters 2005)Beck et al (2001) defined nursery habitat as an areathat contributes to higher production of individuals thatmove to juvenile habitat comparedto other areas Higher growth rates of larval fish are possible because of zooplankton preythat are present during their critical transition from yolk sac to free-living feeding larvae(Hjort 1914 Mullen Fay amp Moring 1986 Rulifson et al 1993 Cooper et al 1998 Martinoamp Houde 2010 Binion 2011) However spatial and temporal overlap between predatorsand prey does not completely explain how fish nurseries function mechanistically Thequality of prey can play a major role in determining the effectiveness of a nursery for earlystages of fish

The quality (chemical composition) of zooplankton prey can influence fish growthdevelopment and survival (Fraser et al 1989 Webster amp Lovell 1990 Copeman et al2002 Rossi et al 2006Malzahn et al 2007 Paulsen et al 2014) Fatty acids are chemicallydiverse often incorporated into organisms unmodified and different organisms havedistinct profiles (Dalsgaard et al 2003) Fatty acids are one class of compounds foundin lipids that are particularly important impacting neural and vision development infish (Gulati amp Demott 1997 Muumlller-Navarra et al 2000 Kainz Arts amp Mazumder 2004Masclaux et al 2012) Fatty acids may act as both dietary tracers in the food web andindicators of overall food quality (Iverson et al 2004) The majority of organisms needspecific dietary fatty acids for somatic development and fitness (Masclaux et al 2012)These fatty acids 183ω-3 α-linolenic acid (ALA) and 182ω-6 linoleic acid (LA) arelabeled essential fatty acids because they cannot be directly synthesized by heterotrophicorganisms and must come from the diet (Arts Brett amp Kainz 2009) Polyunsaturated fattyacids (ie 205ω-3 eicosapentaenoic acid (EPA) 226ω-3 docosahexaenoic acid (DHA)and 204ω-6 arachidonic acid (ARA)) are required for all organisms and play a role inhealth and cell function (Dalsgaard et al 2003) Thus an organismsrsquo fatty acid signaturemay indicate dietary consumption and nutritional quality of its prey (Goncalves et al 2012)

Fatty acids are present in estuaries as a result of de novo synthesis by phytoplankton andthe delivery of detrital material of plant origin (Dalsgaard et al 2003) The free-floatingportion of organic and inorganic particles is termed seston (Postel Fock amp Hagen 2000)The organic portion of seston is important because it forms the origin point for thepropagation of fatty acids through the pelagic food web Zooplankton assimilate fattyacids from the seston through direct consumption of phytoplankton cells detritus andorconsumption of microzooplankton that graze phytoplankton or detritus (Wacker amp VonElert 2001 Kainz Arts amp Mazumder 2004 Vargas Escribano amp Poulet 2006) To date












































































APPENDIX


Seston group

A (8) B (5) C (4)



MUFA 117 101 64




Seston group

A (8) B (5) C (4)


PUFA 135 81 177




D (5) E (2) F (8)








D (5) E (2) F (8)


PUFA 285 489 427




G (1) H (5) I (5) J (5)




PUFA 275 344 523 470



















































































































































































APPENDIX


Seston group

A (8) B (5) C (4)



MUFA 117 101 64




Seston group

A (8) B (5) C (4)


PUFA 135 81 177




D (5) E (2) F (8)








D (5) E (2) F (8)


PUFA 285 489 427




G (1) H (5) I (5) J (5)




PUFA 275 344 523 470










































































































Seston group

A (8) B (5) C (4)


PUFA 135 81 177




D (5) E (2) F (8)








D (5) E (2) F (8)


PUFA 285 489 427




G (1) H (5) I (5) J (5)




PUFA 275 344 523 470











































































































D (5) E (2) F (8)


PUFA 285 489 427




G (1) H (5) I (5) J (5)




PUFA 275 344 523 470









































































































changes in zooplankton community, and seston and zooplankton … · 2017. 8. 16. · 1 department...

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