Historical Reconstruction of Phytoplankton Compositionin Estuaries of Fiordland, New Zealand: the Application of PlantPigment Biomarkers

Susanne E. Schüller & Thomas S. Bianchi & Xinxin Li &Mead A. Allison & Candida Savage

Received: 12 August 2013 /Revised: 2 January 2014 /Accepted: 4 January 2014# Coastal and Estuarine Research Federation 2014

Abstract Phytoplankton pigments in sediment cores from fourNew Zealand fjords were quantified to investigate communitycomposition and primary production in this pristine and remoteregion. Downcore sediment records from Doubtful Sound,Fiordland, were also compared with phytoplankton pigmentsin sediment traps to investigate pathways of phytodetritus fluxfrom the upper water column to the sediment. Historic primaryproduction was estimated using downcore chlorophyll a (Chl a)and β-carotene as proxies for total algal biomass. SedimentaryChl awas similar across Fiordland (p=0.09), butβ-carotene wassignificantly different in Broughton Arm (Kruskal–Wallisp<0.01). Dominant transformation products of Chl awere sterylchlorin esters and carotenol chlorin esters, indicating the impor-tance of grazing as a sink for phytoplankton in Fiordland.Carotenoids indicative of diatoms and dinoflagellates were re-covered in the sedimentary records of Doubtful Sound. Pigmentbiomarkers were observed in higher quantities in the sediment

traps than in the surface sediment. In particular, grazing bio-markers were abundant in the sediment, highlighting the impor-tance of fecal pellet export in phytodetritus preservation. Phyto-plankton pigment preservation in Fiordland sediments is good asindicated by little variation in Chl a/pheopigment ratios through-out the cores. This research supports other new work, which hasshown that carbon preservation in southern hemisphere fjordecosystems is more efficient than previously thought.

Keywords Fjord ecosystem . Historic primary productivity .

Biomarkers . Grazing . Paleoproxies . Pigment degradation

Introduction

Phytoplankton are the basis of coastal food webs (e.g., Jeffreyet al. 2011; Paerl 2006) and play an important role in the

Communicated by James L. Pinckney

Electronic supplementary material The online version of this article(doi:10.1007/s12237-014-9771-z) contains supplementary material,which is available to authorized users.

S. E. Schüller (*) :C. SavageDepartment of Marine Science, University of Otago,310 Castle Street, Dunedin 9010, New Zealande-mail: suse.schuller@gmail.com

T. S. Bianchi :X. LiDepartment of Oceanography, Texas A&M University,College Station, TX 77843-3146, USA

M. A. AllisonInstitute for Geophysics, Jackson School of Geosciences,University of Texas, Austin, TX 78758-4445, USA

C. SavageDepartment of Biological Sciences and Marine Research Institute,University of Cape Town, Rondebosch 7700, South Africa

T. S. BianchiDepartment of Geological Sciences, University of Florida,Gainesville, FL 32611-2120, USA

X. LiGeochemical and Environmental Research Group,Texas A&M University, College Station, TX 77845, USA

M. A. AllisonThe Water Institute of the Gulf, Baton Rouge, LA 70825, USA

M. A. AllisonDepartment of Earth & Environmental Sciences, Tulane University,New Orleans, LA 70118, USA

Estuaries and CoastsDOI 10.1007/s12237-014-9771-z

biological carbon pump, making nutrients biologically avail-able to higher trophic levels in the form of organic matter(OM) (e.g., McLeod and Wing 2007; Paerl 2006; Pinckneyet al. 2001). Cellular excretion, aggregate formation, andgrazing incorporate phytoplankton into the food web andfacilitate its transport through the water column and into thesediment through aggregations or zooplankton fecal pellets(e.g., Chester and Larrance 1981; Smetacek et al. 1978; Turn-er 2002). Pulses of phytoplankton detritus provide an impor-tant input of OM to the sediment in coastal and estuarineecosystems, including fjords (Bianchi 2007 and referenceswithin).

Biomarkers in sediments are commonly used to reconstructpast ecological conditions (e.g., Bianchi and Canuel 2011;Reuss et al. 2005; Villanueva and Hastings 2000) and areparticularly valuable where long-term records are lacking(e.g., southern hemisphere; see Fig. 1 in Batchelder et al.2012). High-performance liquid chromatography (HPLC) isan effective method for examining pigments as biomarkers ofphytoplankton in estuarine and coastal waters (e.g., Bianchi2007; Jeffrey et al. 1997, 2006; Roy et al. 2011). In particular,sedimentary algal pigments have been used to documentchanges in water column primary production (Guilizzoniet al. 1983), phytoplankton community composition(Bianchi et al. 2000b), and light penetration (Leavitt et al.1997) in aquatic ecosystems. Comparison of sedimentarypigment records with historical water column data (Bianchiet al. 2000a, 2002) and models (Cuddington and Leavitt 1999)have verified the use of carotenoids and chlorophyll pigmentsas paleoproxies in aquatic ecosystems. Therefore, fossil phy-toplankton pigments offer a great opportunity to investigatehistorical phytoplankton composition and primary productiv-ity in remote areas where long-term observational records arenot available.

Fjords are ideal estuaries for investigating phytoplanktonpigments in sedimentary records as they generally have deepbasins and limited water exchange (e.g., Syvitski et al. 1987),which reduces sediment resuspension and creates low bottom-water oxygen conditions. In New Zealand fjords, there is apaucity of current phytoplankton research apart from DoubtfulSound, which is mainly dominated by diatoms in modernphytoplankton communities (Goebel et al. 2005) and likelyhas been for the last about 400 years (Schüller et al. 2013).Investigations of phytoplankton composition in the other south-ern fjords, besides Doubtful Sound, have been limited to oneinvestigation in late-autumn when marine flagellated phyto-plankton, were dominant (Goebel 2001). Flagellated phyto-plankton (especially dinoflagellates) are often common infjordic environments during non-bloom conditions (Eilertsenand Frantzen 2007; González et al. 2010; Montero et al. 2011).

A key question in New Zealand’s southern fjords is if theyare mainly dominated by flagellated phytoplankton year-round or do they exhibit similar seasonal changes in

community composition as in Doubtful Sound in northernFiordland. The main flux of phytoplankton detritus and OMto the seabed in Doubtful Sound is largely determined byagglomeration at the end of phytoplankton blooms (S.R.Wing, personal communication) as well as zooplankton graz-ing (Schüller et al., in preparation). Furthermore, novel inves-tigations into OM and carbon transport of phytodetritus aswell as terrestrial input in Fiordland have revealed the closebenthic-pelagic coupling (McLeod and Wing 2007, 2009;McLeod et al. 2010) as well as a good preservation environ-ment for terrestrial carbon in the fjords (Smith et al., inreview).

This study investigates the sedimentary pigment record(chlorophylls and carotenoids) as part of a larger researchprogram to better understand carbon cycling and the relativecontribution of terrestrial (lignins and stable isotopes, Smithet al. 2010; Smith et al., in review) and marine OM inputs(Schüller et al. 2013) in New Zealand fjords. Analysis ofsedimentary records was conducted in four southern hemi-sphere fjords in Fiordland, New Zealand, to evaluate thehistorical phytoplankton record and to extend the current,limited knowledge of phytoplankton communities in southernFiordland. Variations in fossil pigment records are explored inrelation to possible mechanisms (e.g., grazing by zooplank-ton) to understand factors that influence settlement ofphytodetritus and incorporation into the sediment record inpristine estuarine environments. This study also presents nov-el information on sedimentary pigments for New Zealandfjords and thus contributes to the limited knowledge of carboncycling in estuarine systems in the southern hemisphere.

Material and Methods

Site Description

Fiordland, on the west coast of the South Island, NewZealand, provides an ideal coastal systemwith strong physicalgradients to investigate phytoplankton sedimentary pigmentrecords in a pristine environment. Anthropogenic impact isminimal, with an intact watershed of 2.6 million ha of tem-perate rainforest (McLeod et al. 2010). The 14 fjords encom-pass a latitudinal distance of 1°40′ (185 km) and cover a rangeof geomorphologic and physicochemical variations. The av-erage inclination of the northwest facing fjord walls generallydecreases from north to south (∼86° inMilford Sound, ∼56° inChalky Sound, approximate steepness calculated using thehighest peak on the northwestern fjord side and its distanceto the fjord using nautical charts, Goebel 2001). Consequently,irradiance in the northern fjords is seasonally more variablethan in southern fjords (Wing et al. 2004). Furthermore, thereis a decrease in annual rainfall from the north to southernfjords (8,000 to 2,200 mm annually, Sansom 1984), which can

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influence run-off and input of chromophoric dissolved organicmatter (CDOM) to the water column (Gonsior et al. 2008) andconsequently water transparency. The exceptionally high an-nual rainfall (>6,000 mm, Sansom 1984) creates a low salinitysurface layer in the fjords, which is enriched in silicic acid anddepleted in macronutrients (Goebel 2001; Peake et al. 2001).Mixing of the low salinity layer with marine water createsestuarine circulation (Stanton and Pickard 1981) and promotesphytoplankton primary production and the formation of threeseasonal phytoplankton blooms at the mixing interface(Goebel et al. 2005). Furthermore, the fjords are characterizedby shallow entrance sills and discrete deep basins with limitedwater exchange and renewal (Pickrill 1987, 1993; Stanton andPickard 1981), making them efficient traps for sediment andleading to potential hypoxic/anoxic conditions that are favor-able for algal pigment preservation. The sediment load enter-ing New Zealand fjords is considerably lower (<0.5 mg L−1)than the glacially influenced watershed of the West Coast,New Zealand, north of Fiordland (5–25 mg L−1) and morecomparable to open ocean conditions (Pickrill 1993). The lowsuspended particulate matter load in Fiordland waters iscaused by the dense temperate rainforest growing on a thintopsoil layer overlying resistant gneiss and granite rock(Pickrill 1987, 1993). An exception to this is the infrequentbut periodic occurrence of mainly earthquake-triggered land-slides. These can cause local pulses of sediment load, whichare clearly identifiable in cores by visual and radiometricsediment analysis.

Modern phytoplankton communities in the New Zealandfjords are considered to be dominated by marine flagellatedphytoplankton (e.g., Gyrodinium, Dinophysis, Euglena,Prorocentrum, Alexadrium, and Oxytoxum spp.) (watersamples taken at 1, 3, and 9 m at the head of each fjord,Goebel 2001); however, this is based on one sampling occa-sion in May 1999 only (Goebel 2001). The exception isDoubtful Sound (Fig. 1), where diatom abundance comprisesup to 76 % of the phytoplankton community (based onsamples collected over two annual cycles, Goebel 2001).Phytoplankton biomass on the other hand is similar amongthe fjords, ranging from 1 to 16 mg Chl am−2, except in LongSound (Preservation Inlet, Fig. 1) where, on average, it is morethan twofold greater (28.3 mg Chl a m−2, n=3 (May 1998,May and December 1999), Goebel 2001). Long Sound hasbeen described as dominated by dinoflagellates (mainlyCeratium sp.) based on counts of water samples (Goebel2001).

We chose four southern fjords that represent a variety ofecosystems (Table 1). Malaspina Reach (MR) in DoubtfulSound, which is the deepest basin in Fiordland at >400 m.Another deep basin (370 m) was sampled in Long Sound(LS). Long Sound has the highest amount of incident annualirradiance at the fjord head (Wing et al. 2004), highest levelsof CDOM (measured in 1999 (n=2), Goebel 2001) and

phytoplankton biomass and the lowest total annual precipita-tion (Sansom 1984) compared to the other New Zealandfjords. Finally, two sites, Broughton Arm (BA) in BreakseaSound and Supper Cove (SC) in Dusky Sound, which aregeographically close to each other and have the same basindepth (∼170 m), were sampled to evaluate differences in fossilphytoplankton pigments in close proximity basins within thelarger seascape of a highly variable environment.

Sediment Sampling and Geochronology

Cores were collected in the four study fjords in June 2007using a piston corer (i.d. 4.4 cm; Table 1 and Fig. 1). Theywere visually inspected for the presence of a fluffy layer toconfirm the surface of the cores was intact. Cores were sec-tioned into 2-cm intervals and frozen at −20 °C until analysis.CTD casts were taken at all sites at the time of coring.Anchored sediment traps (i.d. 10 cm, 5:1 aspect ratio) withoutpreservatives were deployed at 5 m near Espinosa Point (EP)in Doubtful Sound during summer (December 2007–March2008; Fig. 1). The site where the traps were deployed has amixed-layer depth of 5–10 m and the photic zone extends to3–6 m (Goebel, 2001). The trap material was collected monthly,filtered onto precombusted GF/F filters, and stored at −20 °C inthe dark until analysis.

The geochronology for the cores was determined from theactivity of 210Pb (22.3 year half-life) with depth measuredwith a Canberra low energy, intrinsic Ge γ-spectrometer (welltype). Freeze-dried intervals were ground, packed in 60-mmlong test tube vials, sealed to prevent 222Rn loss, and allowedto in-grow to secular equilibrium for 210Pb for at least 3 weeks.Samples were then counted for 1–2 days. Total Pb activity wasdetermined using net peak area for γ photopeaks at 46.5 keV(210Pb). Excess 210Pb was calculated using the differencebetween the total 210Pb activity and the 226Ra-supported210Pb activity obtained using the averaged activity of 226Radaughters at 295 and 351.9 keV (214Pb) and 609 keV (214Bi).Detector efficiency at each energy level was calibrated using anatural sediment standard (IAEA-300 Baltic Sea) and wascorrected for self-absorption using the method of Cutshallet al. (1983). A best-fit linear regression of the natural log ofexcess 210Pb with depth below any surface mixed layer ofhomogenous activity was used to determine the sedimentaccumulation rate (mm year−1) for the past about 120 years(five half-lives) in the cores (Nittrouer and Sternberg 1981).

Pigment Extraction and Analysis

Pigments were extracted from freeze-dried homogenized sam-ples kept under a N2 atmosphere following the protocol de-scribed in Chen et al. (2005). In brief, sediment aliquots (0.5–1 g) were added to 100 % acetone (3 ml), sonicated in an ice-bath for 1 min, capped, and stored overnight at −20 °C. The

Estuaries and Coasts

sample was centrifuged, and the supernatant was filtered witha nylon syringe filter (0.2 μm) and blown dry with N2 in thedark. Prior to HPLC analysis, acetone (100 μl) was added toredissolve the residue.

Quantitative analysis of the pigments was conducted with aWaters HPLC 600E multisolvent delivery system with anonline Waters 996 photodiode array detector (PDA) and fluo-rescence detector (Shimadzu RF 535), with excitation at440 nm and emission at 660 nm. The injector was connected

via a guard column to a reversed phase Alltech AdsorbosphereC18 column (5 μm particle size, 250×4.6 mm i.d.). Thesolvent gradient system used followed that described byWright et al. (1991) and Bianchi et al. (1996) as modified byChen et al. (2001) to enhance pigment separation.

Chromatograms were integrated and peak areas calculatedusing the Empower 2 Chromatography Data Software (WatersCorporation). The pigments within chromatograms were iden-tified by comparison of retention time and PDA absorption

Fig. 1 Piston core (filled circle)and sediment trap (filled triangle)locations in Fiordland, NewZealand (MRMalaspina Reachand EP Espinosa Point, inDoubtful Sound; BABroughtonArm in Breaksea Sound; SCSupper Cove in Dusky Sound andLSLong Sound in PreservationInlet)

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spectra of individual peaks with pigment absorption spectrareported in the literature (Chen et al. 2003a,b; Jeffrey et al.1997; Louda et al. 2000) and authentic pigment standards(DHI Water and Environment, Denmark), which were runindividually and as mixed standards for determination ofretention times and individual pigment absorption spectra.The pigment standards used within this study were Chl a,pheophorbide a, pheophytin a, chlorophyllide a, α-carotene, β-carotene, diadinoxanthin, diatoxanthin, fucoxanthin, lutein,peridinin, alloxanthin, antheraxanthin, violaxanthin, zeaxanthin,neoxanthin, and lycopene. Peak areas of these pigment standardswith known concentrations were used to calculate responsefactors after Bianchi and Findlay (1991). Response factors wereused together with correction for dilution and extraction efficien-cy to calculate pigment concentrations. The response factors ofthe parent pigment was used for pyro-derivatives of pheophor-bide aand pheophytin a. For chlorophyllone a, CCEs, and SCEs,the response factors of pheophytin awas applied due to similarabsorption spectra. Allo- and epimers of Chl pigments are pre-sented as one pigment.

Data Analysis

Differences in pigment composition among the four studysites were compared using pigment inventories. This approachhas been used successfully to examine degradation pathwaysby comparing the relative contribution of different Chl adegradation products (Chen et al. 2003a,b) and carotenoids(Hodgson et al. 2003, 2005; Tani et al. 2009; Vinebrooke et al.

1998) to overall pigment concentrations in sediment cores.Specifically, the relative abundance of Chl a and its majordegradation products (chlorophyllone a, pheophytin a, andpyro-pheophytin a), grazing biomarkers (SCEs and CCEs)and minor degradation products (chlorophyllide a, pheophor-bide a, and pyro-pheophorbide a) are calculated as percentagecontributions (Chen et al. 2003a,b; Hodgson et al. 2003, 2005;Szymczak-Zyla et al. 2008). Similarly, carotenoids and theirdegradation products are expressed as percent contributions tothe overall carotenoid pigment record. To compare amongsites where different intervals were analyzed, the mean pig-ment concentrations [nanomoles of pigment per gram of drysediment (nmol gds−1)] are summed and standardized by thetotal number of samples analyzed per core.

The ratio of labile Chl a to stable pheopigments(pheophytin a, pheophorbide a, pyro-pheophytin a, pyro-pheophorbide a, SCEs and CCEs) was calculated to describethe extent of pigment preservation (Zhao et al. 2012) and thelevel of refractory material within the phytodetritus(Schönfeld and Numberger 2007). To test for significant dif-ferences among the cores, ANOVAs with type III errors forunbalanced designs were performed on log-transformed pig-ment data and Tukey’s multiple comparison tests were run.When assumptions for ANOVA were not met, the non-parametric Kruskal–Wallis (K-S) test (noted as p*) andWilcoxon rank sum test were performed. Furthermore, two-sample student’s t tests were done to compare pigments insediment traps to surface sediments. All statistical analyseswere performed using R (R Development Core Team 2011).

Table 1 Location of piston cores in Fiordland, length of core recovered (cm), sound depth (m) at the coring site, and literature environmental parameters

Malaspina Reach Broughton Arm Supper Cove Long Sound

Abbreviation MR BA SC LS

GPS position 45°18.1′ S 166°57.92′ E 45°33.59′ S 166°54.69′ E 45°43.67′ S 166°55.85′ E 45°59.05′ S 166°48.58′ E

Core length (cm) 69 114 116 90

Recovery depth (m) 407 168 168 370

Rainfall (mm)a ∼6,400 >6,400 6,400>4,800 2,243

Irradiance (Wh m−2 day−1)b 5,745.53 5,055.18 5,575.32 5,581.62

Northern wall steepness (°)c 70 75 72 68

TC/FAd 8.0 5.1 6.0

Estimated inflow (m3 s−1)d,e 573.3f 301.6d 185.6

Mean surface salinity (PSU)d,g 28.67 30.38d 32.39

CDOM (g440m−1)c ∼0.5 ∼0.6 ∼0.65 ∼1.25

aMean annual rainfall, source, Sansom (1984)b Extracted from Fiordland data system; source, Wing et al. (2003, 2004, 2005)c Source, Goebel (2001)d Source, Stanton and Pickard (1981); TC total catchment area (km2 ), FA fjord area (km2 )e Based on TC/FA ratiof 459.3 m3 s−1 HEP, 113.5 m3 s−1 natural freshwater inflowg For measurements within upper 10 m of water column

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Mean first order decay rate constants (k, year−1) in thesediment were calculated following Leavitt and Carpenter(1990) for the Malaspina Reach core. Only sediment intervalsfrom the MR-core that could be dated (210Pb) reliably (i.e.,down to 12–14-cm interval; Schüller et al. 2013) were used inthe analysis. Decay rate constants were calculated using:

k ¼

X ln Pi=Ptð ÞΔt

� �

n

where Pt is the pigment concentration (nmol gds−1) at time t, Pithe initial pigment concentration in the surface interval,Δt theage of the sediment at the interval Pt, and n the number ofindependent estimates. The decay rate constant (k) is negativewhen pigments decay within the core and positive if theyaccumulate, the latter indicating good pigment preservation.While this provides information on relative decay rates ofpigments, this approach does not account for changes in algalproductivity.

Results

Geochronology

The surface sediment in Doubtful Sound had a surface excess210Pb activity ranging from 17.6 decays per minute (dpm)g−1

at MR to 1.51 dpm g−1 at SC (Fig. 2a). Accumulation rate,determined using a constant rate of supply (CRS) model, was0.49±0.80 mm year−1 for MR, 0.38±0.03 mm year−1 forBroughton Arm (BA), 0.12±0.00 mm year−1 for SC, and0.75±0.45 mm year−1 at LS (Fig. 2b). The CRS model as-sumes a steady state supply of 210Pb to the surface sedimentfrom the atmosphere and overlying water column; thus, anyvariation in excess Pb activity with depth is a function of decay(e.g., age). CRS-derived ages of sedimentary layers at depthare calculated based on the linear sediment accumulation rate,with the fit of the data influenced by the number of points used(i.e., positive excess 210Pb values) (Fig. 2b). Due to the paucityof data points for the SC (r2=1, n=2) and BA (r2=0.99, n=3)cores, sediment ages are interpreted with caution.

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Fig. 2 Geochronology of Fiordland. a Excess 210Pb counts [decay per min (dpm)×1000 kg−1] from Malaspina Reach (MR), Broughton Arm (BA),Supper Cove (SC), and Long Sound (LS) piston cores. b linear regression analysis of log-transformed excess 210Pb decay [ln (dpm kg−1)]

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Chloropigments

The dominant transformation products of Chl a in the sedi-ments were two stable grazing biomarkers, SCEs (24.6–32.2 %) and CCEs (8.4–44.5 %); and chlorophyllone a(11.2–29.5 %; Fig. 3). The relative concentration of the parentmolecule, Chl a, was low and ranged from 4.3 to 4.9 %. Otherpigments detected in the long-term record were pyro-pheophytin a (8.4–17.1 %) and pheophytin a (0.3–9.1 %),but concentrations were also generally low. Pheophytin aconcentration was below detection limits for most intervalsin the BA core. Chlorophyllide a was recovered in only verylow concentrations (<1.9 %) across all fjords.

Downcore concentrations of Chl a ranged from 0.18 to1.33 nmol gds−1 and were stable through time in the fourcores (Fig. 3). In BA, CCEs were the dominant degradationproduct, particularly in the lower part of the core (below60 cm). Similarly, the amount of CCEs increased with depthin the LS core, from >10 to 35 %. By contrast, CCEs wereconsistently <20 % of the total pigment inventory in the MRand SC sediment cores. The relative concentration of SCEswas similar across all cores and least variable through time in

the LS core. Not surprisingly, the medium—to very stable Chldegradation products (pheophytin a, pyro-pheophytin a,SCEs, CCEs, and chlorophyllone a) dominated the downcorerecords, while labile pigments (chlorophyllide a, pheophor-bide a, and pyro-pheophorbide a) contributed <20 % of thetotal inventory (Leavitt and Hodgson 2001) in all four sedi-ment cores.

Total biomass (Chl a) in the four sediment cores was0.48±0.15 nmol gds−1 at SC, 0.54±0.25 nmol gds−1 at LS,0.56±0.18 nmol gds−1 at MR, and 0.67±0.31 nmol gds−1atBA. Differences in Chl a concentrations among the sedimentcores were not significant (p=0.10, F=2.19).

Standardized Chl pigments (standardized to the number ofintervals analyzed per core; N−1) confirmed that SCEs werethe most abundant pigments in the four cores (Fig. 4), with thehighest concentration in MR (4.24 nmol gds−1 N−1) and thelowest in SC (2.73 nmol gds−1 N−1). CCEs were elevated inthe BA core (7.03 nmol gds−1 N−1) and to a lesser extent in theLS core (2.90 nmol gds−1 N−1). In comparison, the averageconcentration of CCEs per interval was a third less in the MRand SC cores (1.16 and 1.42 nmol gds−1 N−1, respectively;Fig. 4). The CCE concentrations in BA and LS were

Chl aChlide a Phide a pPhide a Phytin a pPhytin a

Chlones

SCEs

CCEs

Chl a Chlide a Phide a

pPhide a Phytin a

pPhytin a

Chlones

SCEs

CCEs

Fig. 3 Relative concentration of Chl a and derivatives in cores (fromwhite to black: Chl a →chlorophyllide a (Chlide a) →pheophorbide a(Phide a)→pyro-pheophorbide a (pPhide a)→pheophytin a (Phytin a)→

pyro-pheophytin a (pPhytin a)→chlorophyllone a (Chlone a)→SCEs→CCEs). The x-axis labels indicate the depth interval of the sample

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significantly different from each other and the other two cores(p<0.01; Fig. 4). Chlorophyllone a was also an abundantdegradation product with concentrations significantly differ-ent among the four sites (p<0.01; Fig.4).

Chlorophyllide a, pheophorbide a, and pheophytin a, andpyro-derivatives of the latter two pigments, had low concen-trations (<2.5 nmol gds−1) in the sediment cores. Concentra-tions of chlorophyllide a and pheophytin a differed signifi-cantly among the fjords (p=0.01 and p*<0.01, respectively;Fig. 4). Chl a/pheopigment (Chl a/pheo) ratios were similarthroughout the fjords (0.07±0.01 for MR, 0.05±0.01 for BA,0.06±0.02 for SC, and 0.06±0.03 for LS), with no significantdifferences (p>0.05) among the sediment cores.

Carotenoid Pigments

Neoxanthin (green algae/euglenophytes, minor in higherplants) was the dominant carotenoid at SC (49–86 %) andwas also abundant in all sediment cores, ranging from 5.2 to85.9 %. Within the other three sediment cores (MR, BA, andLS) β-carotene (3.4–40.3 %, total algal biomass) was thedominant carotenoid. α-Carotene (0.0–39.2 %, chlorophytes,prasinophytes, and cryptophytes), and lutein (1.1–21.3 %,green algae, minor in higher plants) (Fig. 5) were also

prevalent. Total biomass (β-carotene) in the four sedimentcores was 2.50 ± 5.56 nmol gds−1 at SC, 7.00 ±12.90 nmol gds−1 at MR, 7.42±18.88 nmol gds−1 at BA,and the highest biomass was observed at LS with 10.56±12.93 nmol gds−1. All pigments with known standards weredetected within at least one sediment interval at MR; however,alloxanthin (cryptomonads) was below detection levels at SC,BA, and LS. Similarly, diatoxanthin (diatoms/dinoflagellates)was not detected in the SC and BA cores, and peridinin(dinoflagellates) and fucoxanthin (diatoms) were absent fromSC and LS sediment records and was only recovered withinthe surface sediment interval at MR. PDA spectrum analysisof chromatograms obtained from the four sediment cores werenot conclusive for the presence of antheraxanthin (Fig. S1).Despite the large peak area of the unknown peak 1, potentiallyantheraxanthin (Fig. S1), only low concentrations of Chloro-phyta, which contain antheraxanthin were observed within thewater column of Fiordland in a previous phytoplankton study(Goebel 2001) and therefore have not been quantified.

Downcore concentrations of the ubiquitous algal biomassbiomarker, β-carotene, was stable through time and<2 nmol gds−1 in all cores, with the highest concentrationsobserved at BA (2 nmol gds−1) and the lowest in LS(0.17 nmol gds−1). The BA sediment core exhibited the

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Fig. 4 Mean concentrations of Chl aand Chl adegradation products with1 SD [grazing indicators: pyro-pheophytin a (pPhytin a), SCEs, CCEs,chlorophyllone a (Chlone a); senescence indicators: pheophorbide a(Phide a), pyro-pheophorbide a (pPhide a), pheophytin a (Phytin a)];grazing/senescence chlorophyllide a (Chlide a) for each core (unit:

nanomoles of pigment per gram of dry sediment per number of sampleinterval). The significance of the differences between the sediment coresfor each pigment are indicated and if they are significant the result of theTukey’s multiple comparisons test is shown. The scales of the y-axis aredifferent between individual pigments

Estuaries and Coasts

greatest variability in downcore pigment distributions, particu-larly for lutein (15.1±7.0 %), zeaxanthin (10.0±7.6 %), and α-carotene (11.3±6.8 %) (Fig. 5). In general, downcore concen-trations of phytoplankton pigments exhibited small variabilitythrough time, with the exception of lutein (chlorophytes andprasinophytes) and α-carotene at BA (Fig. 5).

Standardized carotenoid concentrations (standardized tothe number of intervals analyzed per core; N−1) confirmedthat on average β-carotene was the most abundant carotenoidin the fossil records (Fig. 6), with highest concentration at BA(0.83±0.43 nmol gds−1 N−1) and lowest at MR (0.63±0.20 nmol gds−1 N−1). By contrast, neoxanthin dominated atSC (8.32±3.01 nmol gds−1 N−1) and its concentration wassignificantly different (p*<0.01) to all other cores (Fig. 6). Ingeneral, K-S tests (for all pigments failing the Leveene’s testfor homogeneity) were significant (p<0.05), indicating thatthe pigment distribution differed significantly among thefjords. Specifically, BAwas significantly different to the otherthree cores in terms of all concentrations of carotenoids ana-lyzed (Fig. 6), with the exception of alloxanthin where MRwas significantly different due to the absence of this pigmentin the other sediment cores.

Decay Rate Constants (MR core only)

Phytoplankton pigment decay rates for Chl a, Chl a degrada-tion products, and carotenoids were calculated up to the reli-able sediment accumulation depth of the MR core (i.e., 12–14 cm interval) (Schüller et al. 2013). Chlorophyllide a hadthe fastest decay constant (−0.007 year−1; Table 2) of thepigments analyzed, while SCEs, pyro-pheophorbide a andpheophytin a, exhibited a slower decay constant in the sedi-ment (−0.002 year−1, −0.002 year−1 and −0.003 year−1, re-spectively). CCEs and pheophorbide a had decay constants of−0.004 year−1 and −0.003 year−1 , respect ively.Chlorophyllone a, a stable end product, was the only pigmentthat accumulated with depth in the core at a rate of0.001 year−1 (Table 2). The decay constant of Chl b is−0.001±−0.005, three times less than that of Chl a.

Carotenoids in Doubtful Sound exhibit lower decay con-stants than chlorophylls (−0.0008 year−1 (neoxanthin) to0.0001 year−1 (alloxanthin); Table 2). Generally, carotenoidswith four oxygen atoms (e.g., prasinoxanthin, neoxanthin, andviolaxanthin) had higher decay constants than those withfewer oxygen atoms in their carbon skeleton (e.g., alloxanthin,

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Fig. 5 Relative concentration of carotenoids in cores [from white toblack: β-carotene (β-car)→α-carotene (α-car)→zeaxanthin (zea)→violaxanthin (viol)→prasinoxanthin (pras)→peridinin (perid)→neoxanthin (neo)→lycopene (lyco)→lutein (lut)→fucoxanthin (fuco)→

diatoxanthin (diato)→diadinoxanthin (diadino)→alloxanthin (allo)→antheraxanthin (anth)]. The x-axis labels indicate the depth interval ofthe sample

Estuaries and Coasts

diatoxanthin, lutein, zeaxanthin, α-carotene, and β-carotene).However, no decay constants could be calculated for fuco-xanthin and peridinin since their concentrations were belowdetection limits below the surface sediment interval (Fig. 5).

Sediment Trap Pigments

The SCEs were the dominant Chl-derived pigments in theDoubtful Sound sediment traps during summer (Fig. 7a). TheSCE concentration at 5 m (78.6±13.9 nmol gds−1) was ele-vated relative to the surface sediment concentration (5.3±0.6 nmol gds−1). Similarly, high concentrations of Chl a(65.6 ± 39.6 nmol gds−1 at 5 m) and CCEs (67.9 ±34.8 nmol gds−1 at 5 m) occurred in the traps vs. the surficialsediment. By contrast, chlorophyllide a, pheophorbide a, andpyro-pheophytin a were recovered in greater concentrationsfrom the surface sediment relative to the traps (Fig. 7a).

In contrast to the downcore sediment record (at MR) whereβ-carotene was the dominant preserved carotenoid, fucoxan-thin (48.2±15.9 nmol gds−1) dominated in the sediment trapduring the summer in Doubtful Sound (Fig. 7b). By contrast,only 0.02±0.01 nmol gds−1 of fucoxanthin was measured inthe surface sediment at MR. Besides fucoxanthin, neoxanthin(23.6±9.4 nmol gds−1) and alloxanthin (3.8±5.4 nmol gds−1)were the most common pigments in the sediment traps(Fig. 7b). Similarly, neoxanthin (0.63±0.09 nmol gds−1) and

β-carotene (0.54±0.29 nmol gds−1) were the carotenoid pig-ments with the highest concentrations in the surface sedimentat MR. Generally, concentrations of carotenoid pigments wereelevated in the sediment trap relative to the surface sediment.It is interesting to note that lycopene and peridinin were notobserved within the sediment trap material, however, weremeasured at low concentrations within the surface sediment(0.18±0.01 nmol gds−1 and 0.02±0.004 nmol gds−1, respec-tively; Fig. 7b).

Discussion

Sediment Accumulation Rate

Sediment accumulation rates of the study cores were low andvaried between 0.12 and 0.75 mm year−1, in agreement withreported values for New Zealand fjords (Table 3; Glasby1978; Pantin 1964; Pickrill 1987, 1993; Schüller et al.2013). In the southern hemisphere, comparable sediment ac-cumulation rates have been reported for Chile, with a rate of0.80–1.2 mm year−1 for the Jacaf channel (Rebolledo et al.2008), while higher rates of 2.50–7.40 mm year−1 were re-ported for the Puyuhuapi Fjord (Sepúlveda et al. 2005).Villanueva and Hastings (2000) recorded an accumulationrate of 8.50±4.00 mm year−1 for Saanich Inlet (Canada),

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Fig. 6 Mean concentrations of carotenoids with 1 SD (for abbreviations,see Fig. 5) for each core (unit: nanomoles of pigment per gram of drysediment per number of sample interval). The significance of the differ-ences between the sediment cores for each pigment are indicated (single

asterisk denotes K-S test) and if they are significant the result of theTukey’s multiple comparisons or Wilcoxon rank sum test is shown(**p<0.05). The scales of the y-axis are different between individualpigments

Estuaries and Coasts

while Norwegian fjords vary from 0.10 to 100 mm year−1

(Syvitski et al. 1987). By contrast, in Alaskan fjords, sedimentaccumulation rates range from 450 to 9,000 mm year−1. Com-pared with most fjords worldwide, accumulation rates for theNew Zealand fjords are low due to little to no glacial sedimentinput (with the exception of the Cleddau River in MilfordSound) and low concentration of suspended particulate OM(retained in lakes before enteringwater courses into Fiordland,Pickrill 1987).

Sedimentary Pigment Profiles

Pigment composition in sediment records was similar acrosssouthern Fiordland, with β-carotene the dominant carotenoidin three out of four sediment cores and neoxanthin mostabundant at SC. Neoxanthin is likely derived from greenfilamentous algae since siphonein was also identified (butnot quantified) from PDA absorption spectra (Jeffrey et al.1997) (Fig. S1). Generally, carotenoid concentrations do notvary markedly in the downcore records in southern Fiordland(Fig. 5), indicating similar preservation conditions throughtime. Higher concentrations of green algal biomarkers

(neoxanthin and lutein) and diatom and dinoflagellate bio-markers (diadinoxanthin, fucoxanthin, and peridinin) are pre-served in the upper sediment of MR. This is likely due toincreased silica input into Doubtful Sound from the hydro-electric power station initiated in 1969, which has also beenassociated with a marked increase in the relative abundance ofsedimentary limnic diatoms (from 24 to 52.6 %) in the innerbasin (Schüller et al. 2013). Similarly, the relative concentra-tion of diadinoxanthin increased in the surface interval (0–2 cm, 3.63 %) in comparison to the remainder of the sedimentcore (1.61±0.24 %; Fig. 5). These changes in fucoxanthin anddiadinoxanthin in the MR record were not observed in theother three fjords, suggesting that the recent increase in silica-rich diatoms is a local phenomenon and likely due to theinfluence of the hydro-electric power station. This requiresfurther investigation using high-resolution sediment records.The pigment record in BA had the best preservation of labilepigments typical of dinoflagellates and diatoms (e.g., fuco-xanthin: 0.09±0.07 nmol gds−1 and peridinin: 0.03±0.04 nmol gds−1), suggesting that BA is a good sink forphytodetritus.

Historical Algal Biomass

Total algal biomass (Chl a and β-carotene) (e.g., Jeffrey et al.1997; Leavitt 1993) in Fiordland was reasonably constantthrough time at the four sites (Figs. 3 and 5). Chl a, which ismore labile than β-carotene (Leavitt and Hodgson 2001), wasnot significantly different among the fjords (p=0.09, F=2.71),suggesting similar long-term total algal biomass (Figs. 3 and4). Thismay reflect either constant Chl a input to the sediment,or variable Chl a input but greater degradation during higheralgal biomass periods. Chl a concentrations measured inter-mittently in the water column were highest in LS (36 mg Chl am−2, n=3) with the other fjords ranging between ∼5.5 and∼9.3 mg Chl am−2 (n=3) (Goebel 2001). However, no long-term annual averages of water column Chl a exist, and con-sequently, no significant correlation between water columnChl a (Goebel 2001) and average sediment Chl a (Spearman’sr=−0.63, p=0.73) and β-carotene (Spearman’s r=−0.64,p=0.76) concentrations were observed in Fiordland. Similardiscrepancies between water column and sedimentary Chl ahave been reported in other aquatic systems and have beenattributed to the labile nature of the Chl amolecule (Vinebrookeet al. 1998) and the lack of regular water column monitoring(Reuss et al. 2005). Lack of correlation between sediment andwater column Chl a concentrations in Scandinavian estuarieswhere reliable records exist has been attributed to the alloch-thonous origin of phytoplankton preserved in sediments(Himmerfjärden, Sweden) and discrepancies in eutrophicationstatus between sediment and water column samples (MariagerFjord, Denmark) (Bianchi et al. 2002; Reuss et al. 2005). Bycontrast, water column Chl a and sedimentary β-carotene have

Table 2 First-order decay rate constant (k) (year−1) with 1 SD for Chl a, itsdegradation products, as well as carotenoids from the MR sediment core

Pigment ka

Chl a −0.004±−0.003Pheophytin a −0.003±−0.003Pyro-Pheophytin a −0.004±0.012Pheophorbide a −0.003±−0.001Pyro-pheophorbide a −0.002±−0.005Chlorophyllide a −0.007±−0.007Chlorophyllone a 0.001±−0.006SCE −0.002±−0.004CCE −0.004±−0.006Chl b −0.001±−0.005Neoxanthin −0.0008±−0.1500Prasinoxanthin −0.0007±−0.0128Violaxanthin −0.0007±−0.0128Diadinoxanthin −0.0007±−0.0132Alloxanthin 0.0001±0.0011

Diatoxanthin −0.0001±−0.0019Lutein −0.0003±−0.0064Zeaxanthin −0.0002±−0.0030Lycopene −0.0005±−0.0100α-carotene −0.0002±0.0024β-carotene −0.0002±0.0031

aNegative values of k indicate decay and positive values of k a gain of theindividual pigment over the length of the sediment core analyzed (12–14-cm interval) which was determined by the maximum reliable age of thesediment as indicated by 210 Pb geochronology

Estuaries and Coasts

been correlated in Canadian lakes (r=0.33, p<0.001)(Vinebrooke et al. 1998), which have regular long-term recordsand a more closed ecosystem than coastal fjords. While regular

water column measurements would be preferable to correlatewith sedimentary phytoplankton records in remote areas suchas Fiordland, sedimentary pigment records still provide

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Table 3 Range of sedimentationrate values reported for fjordbasins in other studies conductedin Fiordland, New Zealand

a Sediment accumulation rateestablished from earthquake in1826/1827 and the overlyingamount of material (see Pantin1964)

Location Accumulation rate(mm year−1)

Method Source

Milford Sound 9.65–11.68 a Pantin 1964

Nancy Sound 0.83–4.29 14C Glasby 1978

Bradshaw Sound 0.77–0.85 14C Pickrill 1993

Thompson Sound 0.24–1.33 14C Pickrill 1993

Doubtful Sound 0.49–0.99 210Pb Schüller et al. 2013

0.88–2.31 14C Schüller et al. 2013

Preservation Inlet 0.54–1.27 14C Pickrill 1993

Estuaries and Coasts

valuable insights on past phytoplankton composition and pro-cesses where observation records are lacking.

Pre- and Postpigment Decay

In addition to Chl a, the sediment trap material in DoubtfulSound was dominated by products indicative of grazing, suchas CCEs and SCEs, and also the oxidized form of 132,173-cyclopheophorbide-a-enol, chlorophyllone a (Fig. 7). CCEindicates diatom herbivory (Goericke et al. 1999), whichagrees with the prevalence of diatoms in modern phytoplank-ton assemblages in Doubtful Sound (Goebel et al. 2005).Furthermore, the concentration of SCEs (another grazingbiomarker; King and Repeta 1994) in the sediment traps,reveals that herbivory is an important factor that influencesChl a degradation in the upper 5 m of the water column inDoubtful Sound (Goericke et al. 1999). Grazing experimentswith copepods fed cultured and natural phytoplankton fromMR indicate a large proportion of intact Chl a (64.32±6.05%;similar to the Chl concentrations in the sediment traps of thisstudy; Fig. 7) and pheophytin a (23.78±7.12 %) and smalleramounts of SCE (1.55±0.23 %) and CCE (1.75±9.56 %) infecal pellets (Schüller et al., in preparation). The prevalence ofgrazing biomarkers in the sediment and significant reduction inpigments in the surface sediment compared to the trap material(total Chl p=0.01, t=2.91; carotenoids p=0.04, t=2.21) in anenvironment with low sediment accumulation rates (Fig. 2)indicates that both sinking algal blooms and fecal pellets pro-vide efficient pathways to deliver phytodetritus to the sedimentin Doubtful Sound (Turner 2002). Studies in both the Gulf ofMexico and the East China Sea shelf have linked the sedimen-tary presence and dominance within the chloropigment inven-tory of SCEs and also CCEs to grazing activity in the watercolumn and consequent transport by fecal pellets to the sedi-ment (Li et al. 2013; Sampere et al. 2008; Zhao et al. 2012).

The substantial loss (∼99 %) of fucoxanthin between theupper water column (sediment trap) and surficial sediment islikely due to its partial transformation into CCEs (Goerickeet al. 1999) through zooplankton grazing (Schüller et al., inpreparation). Further destruction of fucoxanthin throughchemical oxidation during flux through the water column(407 m) at MR is likely (Cuddington and Leavitt 1999).However, more labile carotenoids, which are part of thephoto-protective xanthophyll cycle, such as diadinoxanthin(diatoms) and violaxanthin and (chlorophytes, prasinophytes,and terrestrial material) (Hager 1980), were generally wellpreserved within the sediment trap and the surface sediment(Figs. 5 and 7) at MR, suggesting incorporation into fecalpellets or terrestrial origin. Indeed, these pigments were pre-served in all surface sediment samples analyzed (Fig. 5), withpreservation likely enhanced by the CDOM-rich waters ofFiordland (1 % surface irradiance at 3–29 m; Goebel 2001),which limits photo-oxidation in the upper water column.

Once incorporated into the sediment, the relative stabilityof the different pigments followed previous published studies.For example, SCEs and pyro-pheophorbide a were the moststable pigments (Chen et al. 2003b; Soma et al. 2001) andexhibited the slowest Chl decay constants in this study. CCEsand pyro-pheophytin a had similar decay constants to theparent molecule Chl a with an intermediate decay constant(Table 2). The Chl a decay rate for freshly deposited phyto-plankton material was generally greater in the oxic surfacesediment (k=0.05 day−1, Bianchi et al. 2000b) than in the topintervals of the MR core, which is expected since phytoplank-ton pigments degrade more slowly once incorporated into thesediment record (Leavitt 1993). Conversely, the decay con-stants for carotenoids at MR were highly dependent on thechemical structure, the number of oxygen atoms, and thepresence of 5,6-epoxy groups (easily oxidized under changingredox conditions) (Repeta 1989; Repeta and Gagosian 1987;Sinninghe Damsté and Koopmans 1997). The most stablecarotenoids had less oxygen atoms and 5,6-epoxy groups(Table 2, Repeta 1989). To date, carotenoid decay constantshave been established for freshly deposited material (HudsonEstuary, Bianchi and Findlay 1991), recently deposited mate-rial (East China Sea shelf, Li et al. 2013) or laboratory exper-iments (e.g., Nelson 1993), which have reported faster decayrates than those observed in Doubtful Sound, which has lowerprimary production than other fjords (e.g., Burrell 1988;Goebel 2001; Pizarro et al. 2000; Timothy and Soon 2001;Wassmann 1991).

Degradation Mechanisms and Preservation Conditions

Grazing is likely an important process that influences sedi-mentary pigment records in Fiordland. Comparison of pig-ments extracted from the sediment trap at MR and the sedi-mentary records suggest that zooplankton grazing degradesphytoplankton Chl a (pyro-pheophytin a, SCEs and CCEs,min. 37–73 % of Chl a inventory; Fig. 3), with up to 13 % ofphytoplankton standing stock removed daily through copepodherbivory in Doubtful Sound (Schüller et al., in preparation).Similar contributions of zooplankton grazing biomarkers havebeen found in more river-dominated margins such as theLousiana Shelf and the East China Sea shelf, where SCEsand CCEs contributed large proportions to the overall Chl ainventory (up to 72%) (Sampere et al. 2008; Zhao et al. 2012).Predepositional degradation of algal Chl a in Doubtful Soundis also evident from the low Chl a/pheo ratios in all fjords,with ratios indicating older refractory phytodetrital material(MR, 0.07±0.01) and a combination of older refractoryphytodetrital and terrestrial material (BA, 0.05±0.01; LS,0.06±0.03; SC, 0.06±0.02) preserved in the sediment(Schönfeld and Numberger 2007). The Chl a/pheo ratiosobserved in Fiordland are on average lower than those ob-served on the East China Sea shelf (up to ∼0.38) and more

Estuaries and Coasts

similar to lower sediments within the Louisiana Shelf (Zhaoet al. 2012), highlighting the refractory nature of the phyto-plankton material upon reaching the fjord sediments. Howev-er, there was no significant difference in the Chl a/pheo ratioamong fjords (r2=0.25, p>0.05), suggesting a similar degreeof degradation in the water column prior to incorporation intothe sediment across all fjords.

Sedimentary concentrations of Chl a and Chl a/pheo ratioswere similar among fjords, indicating that once pigment ma-terial (phytoplankton and terrestrial matter) is buried in thesediments, degradation by bioturbation and/or chemical oxi-dation is minimal in Fiordland. By contrast, some variation inChl a/pheo ratios in river-delta estuaries has been associatedwith minimal postdepositional reworking of the sediment(Zhao et al. 2012), and changes in the ratio due to eutrophi-cation can be discarded (Schönfeld and Numberger 2007;Zhao et al. 2012) since New Zealand fjords are pristine andshow no sign of eutrophication (Goebel 2001; McLeod et al.2010). All sediment cores were clearly anoxic during visualinspection upon retrieval (personal observation), suggestingfavorable pigment preservation conditions with fewbioturbators that can alter the sediment record. Furthermore,210Pb profiles (Fig. 2a) do not indicate sediment mixing andwater column oxygen profiles taken during sampling demon-strate anoxic bottom water (e.g., <5 ml l−1 below 93 m waterdepth at SC, min. 0.50 ml l−1 at 166 m depth), supportingearlier observations of anoxia (Stanton and Pickard 1981) andunfavorable conditions for bioturbators (Szymczak-Zyla et al.2011). By contrast, bottom-water oxygen levels at LS wereadequate (>5 ml l−1) for the presence of benthic fauna and theexponential decay of the radioisotopes was slightly less pro-nounced than in the other cores (Fig. 2a), indicating potentialbioturbation in the upper sediment. Below 12-cm depth, how-ever, no bioturbation is evident in the LS core as also support-ed by the Chl a/pheo ratio (0.06±0.03).

In summary, the phytoplankton detritus reaching the deepbasins is partly degraded (low Chl a/pheo ratio) throughzooplankton grazing, and possibly algal senescence; however,the extent of degradation is similar among fjords, makingcomparisons of sediment records possible. Once phytoplank-ton detritus reaches the sediment, preservation of algal pig-ments in southern Fiordland’s deep basins is good as indicatedby little variation in the Chl a/pheo ratio.

Conclusions

The current study described pigments in sediment recordsfrom four remote New Zealand fjords, adding to the verylimited knowledge on productivity and carbon burial in thisgeographical region. This study also presents new informationon the role of various physicochemical processes on thepreservation of organic carbon in sediments. For the first time,

sediment accumulation rates for Broughton Arm and DuskySound were determined and advanced understanding of thewide range of sedimentation regimes in Fiordland, NewZealand. Historical phytoplankton biomass among the fourfjords varied according to the biomarker proxy. Concentra-tions of Chl a were similar among fjords (p=0.09), whereasconcentrations of β-carotene varied, with BA being signifi-cantly different from all other fjords (p<0.01). Grazing pres-sure in Fiordland was demonstrated by the high proportion ofgrazing biomarkers (pyro-pheophytin a, SCEs, and CCEs)preserved in both sediment traps in Doubtful Sound and thefossil pigment record (all fjords; Fig. 5). Due to grazing andother processes such as senescence, phytodetritus that reachesthe sediment is quite degraded as indicated by the low Chl a/pheo ratios. However, this ratio does not vary through time,indicating good preservation conditions within the sediment,possibly due to anoxic bottom waters and negligible or nobioturbation. Therefore, the fjords provide good preservationconditions for biogenic carbon derived from phytoplankton,supporting recent studies on the preservation of terrestrialorganic carbon in fjord sediments by Smith et al. (in review).

Acknowledgments We would like to thank the captain and crew of theRV Polaris II for support in the field. We are grateful for financial supportfromUORG and PBRF funds (C.S.), NewZealand International DoctoralResearch Scholarship and a University of Otago Publishing Bursary(S.E.S.), and the Chinese Scholarship Council (X.L.). The manuscriptbenefited from comments by Jun Zhao and two anonymousreviewers.

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