dub-_et_al-2013-integrated_environmental_assessment_and_management

sessment and Management — Volume 9, Number 3—pp. 426–438SpecialSeries

Integrated Environmental As
426 � 2012 SETAC
Accumulated State of the Yukon River Watershed:Part I Critical Review of LiteratureMonique Dube,*y Breda Muldoon,y Julie Wilson,y and Karonhiakta’tie Bryan MaraclezyCanadian Rivers Institute, University of New Brunswick, Alberta, CanadazDirector of Natural Resources, Council of Athabascan Tribal Governments, Fort Yukon, Alaska, USA

(Submitted 28 February 2012; Returned for Revision 16 April 2012; Accepted 21 August 2012)

EDITOR’S NOTEThis paper is 1 of 9 articles in the Special IEAM Series entitled, Watershed Cumulative Effects Assessment (CEA). The

research program emanated from a 4-year Canadian Water Network initiative, ‘‘Development of The Healthy River EcosystemAssessment System (THREATS) for Assessing and Adaptively Managing the Cumulative Effects of Man-made Developmentson Canadian Freshwaters.’’ The objectives were to develop a framework for watershed CEA, implement portions of theframework in multiple river basins across Canada, and to develop legacy tools (i.e., THREATS decision support software) forongoing development, use, and uptake by water stakeholders.

ABSTRACTAconsistentmethodology for assessing theaccumulating effects of natural andmanmade changeon riverine systemshasnot

been developed for a whole host of reasons including a lack of data, disagreement over core elements to consider, and

complexity. Accumulated state assessments of aquatic systems is an integral component of watershed cumulative effects

assessment. The Yukon River is the largest free flowing river in the world and is the fourth largest drainage basin in North

America, draining 855000 km2 inCanada and theUnited States. Because of its remote location, it is consideredpristine but little

is known about its cumulative state. This review identified 7 ‘‘hot spot’’ areas in the Yukon River Basin including Lake Laberge,

Yukon River at Dawson City, the Charley and Yukon River confluence, Porcupine and Yukon River confluence, Yukon River at the

Dalton Highway Bridge, Tolovana River near Tolovana, and Tanana River at Fairbanks. Climate change, natural stressors, and

anthropogenic stresses have resulted in accumulating changes including measurable levels of contaminants in surface waters

andfish tissues, fishandhumandisease, changes in surfacehydrology, aswell as shifts inbiogeochemical loads. This article is the

first integrated accumulated state assessment for the Yukon River basin based on a literature review. It is the first part of a 2-part

series. The second article (Dube et al. 2013a, this issue) is a quantitative accumulated state assessment of the Yukon River Basin

where hot spots and hot moments are assessed outside of a ‘‘normal’’ range of variability. Integr Environ Assess Manag

2013;9:426–438. � 2012 SETAC

Keywords: Cumulative effects assessment Multiple stressors River Water Yukon River

INTRODUCTIONUnderstanding how a river has been cumulatively affected

by natural and anthropogenic stress over broad temporaland spatial scales is an enormous undertaking. A common,integrated, diagnostic process to assess cumulative effectsof watersheds does not exist nor are key elements agreed on(Dube 2003). Development of an approach in Canada hasbeen hindered primarily by 3 factors; historical and arguablyineffectual application of cumulative effects assessment(CEA) under existing legislation (Canadian EnvironmentalAssessment Act), lack of data to conduct such an assessmentat the scales necessary, and lack of a champion entity ororganization to establish on-going practice.

Assessment of watershed CEA includes 3 main compo-nents, regional monitoring, an accumulated state assessment,and development of relationships where development activ-ities are linked to key ecosystem responses (causal associationat landscape scales) (Dube et al. 2013b, this issue). Relation-

* To whom correspondence may be addressed: [email protected]

Published online 24 August 2012 in Wiley Online Library

(wileyonlinelibrary.com).

DOI: 10.1002/ieam.1360

ships that link development activities to indicators of aquatichealth are fundamental to develop modeling tools for land useand watershed planning where different development scenar-ios can be forecasted and decided on.

This article focuses on 1 element needed for effectivewatershed CEA, accumulated state assessments. This assess-ment begins with an understanding of normal or naturalvariability at sites unaffected by development in time or spaceor more commonly at sites unaffected by the developmentunder evaluation (Kilgour et al. 2006). In environmentalstudies that measure change due to stress, the existence of thechange is based on some comparison back to a previous orexpected state. Natural variability is often the benchmarkused to compare to for identification of changes in space(‘‘hot spots’’) and time (‘‘hot moments’’). The change canbe chemical or biological in nature. Chemical examinationoften involves the biogeochemistry (chemical composition)of water whereas biological analysis looks at the healthof aquatic organisms through community, individual, andphysiological response indicators (Dube 2003). Accumulatedstate assessments ideally also include a stressor-based assess-ment to assess changes on the land (Dube 2003). If data ofappropriate scale are available, occurring effects can be usedto determine the state of the watershed and create a

Qualitative Accumulated State Assessment of the Yukon River— Integr Environ Assess Manag 9, 2013 427

benchmark to assess the sustainability of future development(Dube and Munkittrick 2001).

This article assesses the accumulated state of the YukonRiver Basin (YRB) based on a critical literature review ofexisting information. Areas of documented disturbance, asconcluded by the authors of the literature, were cataloguedas hotspots or areas most at risk for accumulating effects andlater verified through quantitative accumulated state analysis(second article in series, this issue). As data availability are acore limiting factor to assessments and very few studies havecollected data in the context of broad accumulated stateassessments, this article intended to illustrate how resultsfrom existing literature could be integrated to identifyhot spots and hot moments as a preliminary, ‘‘first pass’’assessment.

The Yukon River was selected as a model river for thisstudy, as it is the largest free flowing river in the world(Nilsson et al. 2005) and the fourth largest drainage basin inNorth America, draining 855 000 km2 in Canada and theUnited States (Brabets et al. 2000) (Figure 1). Its headwatersbegin in British Columbia (BC) where it flows into the centralYukon curving into Alaska and finally discharging into theBering Sea. Water that flows from the Yukon contributes 8%of water in the Arctic Sea (Brabets et al. 2000). It contributesmost of the freshwater runoff, sediments, and dissolvedsolutes (such as terrigenous dissolved organic C) to the

Figure 1. Map of the Yukon River Basin showing drainage sub basins, Canad

(inset modified from http://www.water.usgs.gov).

eastern part of the Bering Sea (Lisitsysn 1969; Opsahl et al.1999; Hansell et al. 2004). Because of its remote location it isconsidered pristine but little is known about its accumulatedstate.

EFFECTS-BASED REVIEWThis section reviews the literature where different

responses were measured in environmental indicators forthe Yukon River including water quality, quantity, fish tissueburdens, and fish and human disease reports. It summarizesthe indicators that have been measured and documentedchanges and conclusions based on the original authors’articles. It also presents a baseline from these studies in theform of describing expected patterns and trends of indicatorresponses commonly observed in the Yukon River.

Water quality baseline

The water quality of the Yukon River varies seasonally andspatially. From May to September, when the water is ice-free,75% of the annual stream flow runoff occurs (Brabets et al.2008) concurrent with the greatest discharge of organic C,nutrients, and sediments. Dissolved organic C (DOC) hasbeen studied extensively in the Yukon River because of itscomposition and cycle in the environment and the potentialto be influenced by climate change. Loads are generally

a/US border, and location of hotspots identified from the literature review

428 Integr Environ Assess Manag 9, 2013—M Dube et al.

highest in spring during freshet and lowest in winter (Strieglet al. 2005) with 63% exported during ice out (Raymondet al. 2007). Tributaries of the Yukon River surrounded bywetlands, such as the Porcupine River, have the highest DOCloads whereas tributaries surrounded by bare rock, such asthe Tanana River, have the lowest DOC loads (Striegl et al.2005).

The Yukon River is oligotrophic, limiting biological growth(Guo et al. 2004). Additional nutrient loads into the river willalter growth in the system. The major flux of N and P occursduring open water, May to September. The maximumloading of nutrients occurs during spring freshet, May, anddecreases through September. The dominant species areparticulate P (PP) and dissolved organic N (DON) (Guo et al.2004). The source of P and N differs with P coming fromchemical rock weathering, whereas N comes from plantmaterial, land erosion in the spring, leaching of deeper soilhorizons in the summer–autumn, and from groundwater inthe winter (Dornblaser and Striegl 2007). Phosphorus islimited in the system and any increases in P discharge couldimpact aquatic growth and water quality (Guo et al. 2004).

Suspended sediment (SS) in the Yukon River carriesorganic C, nutrients, contaminants, and a full suite of otherminerals to the Bering Sea. Changes in SS concentrations havethe potential to impact aquatic life by interfering with fishrespiration, surface-prey feeding, spawning site availability,and benthic habitats (McLeay et al. 1987; Dornblaser andStriegl 2009). Suspended sediment concentrations of theTanana River and White River contribute the highest SS loadsto the Yukon River (Brabets et al. 2000; Dornblaser andStriegl 2009). Currently 95% of SS discharge occurs fromMay to September (Brabets et al. 2008) although the sourceof the SS deposition changes throughout the seasons. Inspring, sources are from bank erosion and the resuspensionof deposited sediments whereas in the summer–autumn, SScomes from glacial melt (Dornblaser and Striegl 2009).Suspended sediment composition is mostly silt and clay butalso contains carbonate, quartz, and feldspars (Brabets et al.2000; Eberl 2004).

Effects on water quantity and quality

In the interior regions of Alaska, south of the Yukon River,permafrost is warming between 0.3 8C to 1 8C (Osterkamp2005). These authors report that permafrost warming willincrease groundwater runoff consequently altering streamflow. Changes in stream flow have occurred in the YukonRiver at Whitehorse and on the tributaries of the Stewart,Tanana, Takhini, Salcha, and Porcupine Rivers (Table 1:1.12,1.13). Increases in groundwater discharge have also beenobserved through much of the basin over the past few years(Table 1:1.14). These results are supported by Peterson et al.(2002) who showed that freshwater flows from 6 of thelargest Eurasian rivers to the Arctic Ocean (Yenisey, Lena,Ob’, Pechora, Kolyma, and Severnaya Dvina) have increasedas average air temperatures have risen. Increases in freshwaterrunoff are expected to affect ocean stratification, circulation,and even global climate processes through the slowing ofthermohaline circulation (Schiller et al. 1997; Weaver et al.1999; Ottera et al. 2003).

Dissolved organic C loadings are predicted to change, asnorthern regions become warmer, permafrost melts, and riverand groundwater flows are altered. Striegl et al. (2005, 2007)

have predicted that as permafrost thaws DOC yields willinitially increase, as meltwater runoff to the Yukon Riverincreases, but as flow paths deepen DOC will be consumedmore rapidly in the soil and groundwater (Table 1.16).Raymond et al. (2007) are consistent with this predictionstating that warming permafrost will increase stream flowleading to increase DOC loading across the Yukon River Basinas so far that the land has no more DOC to yield to the water(Table 1.17). The discrepancy between the single year resultsshown by Raymond et al. (2007) (a rising trend) and the3-year results shown by Striegl et al. (2005) (a falling trend)illustrate the need for multidecadal monitoring and observa-tion. There is agreement that DOC will increase as temper-atures warm and flows increase but the persistence of theincrease (how long it will occur) is unknown.

Permafrost thaw and consequently a deeper active layerare expected to alter N, P, and SS levels in the Yukon Riverbased on conclusions of Guo et al. (2004), Walvoord andStriegl (2007), McLeay et al. (1987), and Dornblaser andStriegl (2009). Suspended sediment concentrations in theYukon River have increased as water yields have increased(Table 1.18). Increased SS in rivers have affected Arcticgrayling appearance, lowered their food consumption,increased consumption of O2, reduced fish size, and increasedsusceptibility to contaminants (Table 1.9) (McLeay et al.1987). Benthic invertebrate studies in the Yukon Riverhave shown that high SS loads increased the abundance ofpollution tolerant taxa (Table 1.10) (LePage 2009).

Effects—disease and contamination in fish and water

Nearly all village residents of the Yukon River Basin relyheavily on fish and game resources for survival (Kruse 1998;Brabets et al. 2000). All communities along the river obtaintheir drinking water from the Yukon River, its tributaries,or related aquifers and lakes (Roach et al. 1993). In someareas, the water is not treated before being consumed (Roachet al. 1993). Therefore, for many Alaska Natives who rely ontraditional and customary activities any deleterious changes inwater quality could have profound societal impacts (Houseret al. 2001).

Studies on fish from the Yukon River Basin have reporteddetectable levels of contaminants in tissues, some of whichexceed consumption guidelines. In addition, sediment corestaken from Lake Laberge showed residues of contaminantsoriginating from anthropogenic sources (Rawn et al. 2001).Some studies have reported waterborne contaminants insurface waters at concentrations that exceed Canadian and USguidelines for drinking and recreational activities. Recentstudies on salmon have shown them to carry a parasiticdisease known as Ichthyophoniasis that currently threatenstheir migrations from the Bering Sea up the Yukon River(Kocan et al. 2004). The extent and details of these findingsare presented in the sections below.

Trace contaminants

Mercury (Hg) and selenium (Se) have been measuredin fish tissues from the Yukon River at levels exceedingconsumption criteria or toxicity thresholds (Duffy et al. 1998;Jewett et al. 2003; Hinck et al. 2004, 2006). In northern pike,longnose sucker, and burbot, Hg levels (0.08–0.65 mg/g)exceeded toxicity thresholds for all bird and small mammalmodels suggesting a risk to piscivorous wildlife throughout

Table

1.Summary

ofaliterature

review

ofstressorvariablesontheYu

konRiver

Nr

Stress

variable

Effect

measu

red

Reference

1.1

Se

Max:in

maleB(0.85

mg/g)in

TRatFB

.High:inmaleNP(0.66

mg/g),femaleLS

(0.62

mg/g)atC-K

confluence

and

female

LS(0.61

mg/g),female

B(0.69

mg/g)in

TRatFB

andfemale

LS(0.60

mg/g)atDHB

Hinck

etal.2004

Mea

n:(0.72

mg/g)in

PRatFish

HookBen

dandseco

ndhighest(0.61

mg/g)in

TRatFB

Max:

inB(0.85

mg/g)in

TRatFB

Hinck

etal.2006

1.2

Hg

Max:

infemale

NP(0.69

mg/g)atToRatTolovana

Hinck

etal.2004

High:in

femaleandmaleNP(0.46and0.56

mg/g)attheDHB,in

male

B(0.30

mg/g)andfemaleandmaleNP(in

TRatFB

)

Mea

n:(0.41

mg/g)atDHB

0.3

mg/g

inallpikeatDHB,ToRatTolovana,andYRatTanana>0.3

mg/g

inallburbotin

TRatFB

Hinck

etal.2006

THg:Highlevels

inLT

(0.30

mg/g)

Brauneetal.1999

Mea

nTH

g:Highin

NP(1.506

mg/g)andAG

(0.264

mg/g)in

YR

Jewett

etal.2003

Mea

nMeH

g:Highin

NPin

muscle

(1.56

mg/g)andin

liver

(1.20

mg/g)

MeH

g:NPandShee

fish

hadlevelsexceed

ing0.2

mg/g

Duffyetal.1998

MeH

g:Specieswithhighestlevels(0.718

mg/g)wasNP

1.3

PCBs

Max:

inFemale

LS(0.09

mg/g)in

TRatFB

Hinck

etal.2004

Mea

n:atFB

(0.062

mg/g)

Max:

inLS

andB(>

50ng/g)in

TRatFB

Hinck

etal.2006

Max:

levels

ofAroclor1260(0.84

mg/g)andAroclor1254(0.71

mg/g)atFB

Muelle

randMatz

2000

Mea

n:in

B(0.40

mg/g)atFB

andB(3.43

mg/g)from

Lake

Laberge

Mea

n:Allmaxlevelsfoundin

fish

from

Lake

Laberge;

B-liver

(1.267

mg/g),LT-m

uscle

(0.448

mg/g),WF-muscle

(0.061

mg/g),AG

(0.021

mg/g),andNP(0.090

mg/g)

Brauneetal.1999

Max:

inLake

Labergesedim

entco

resample:1964at0.0161

mg/g

dw

Rawnetal.2001

Surface

sedim

entslicein

Lake

Laberge:

1991at0.008

mg/g

dw

1.4

DDT

Mea

n:highest(0.011

mg/g)atFB

Hinck

etal.2004

Max:

inLS

(0.0047

mg/g)andNP(0.009

mg/g)atTR

atFB

Hinck

etal.2006

Max:

levels

ofp0 p-D

DE(0.47

mg/g)andp0 p-D

DD(0.44

mg/g)atFB

Muelle

randMatz

2000

Mea

n:Highestlevelin

B-liver

(3.433

mg/g);alsohighin

LT-m

uscle

(0.448

mg/g)andNP(0.247

mg/g)

Brauneetal.1999

(Continued)


Table

1.(Continued)

Nr

Stress

variable

Effect

measu

red

Reference

MaxDDTin

Lake

Labergesedim

entco

resample:1960at0.0214

mg/g

dw

Rawnetal.2001

DDTdropped

to0.0012–0

.0016

mg/g

dw

insedim

ents

betwee

n1971and1989

1.5

Toxaphen

eMax:

inNP(0.029–0

.034

mg/g)atC-K

confl.andToRatTolovana

Hinck

etal.2006

Max:

alllevels

foundin

fish

from

Lake

Laberge;

B-liver

(2.301

mg/g),LT-m

uscle

(0.344

mg/g),WF-muscle

(0.0338

mg/g),AG

(0.025

mg/g)andNP(0.048

mg/g)

Brauneetal.1999

Highestmed

ian:B-liver

0.14

mg/g

ww

atFB

and0.290

mg/g

ww

atYu

konFlats

Muelle

randMatz

2000

1.6

Enteroco

cci

YRatStevensvilla

geEnteroco

ccilevelsat4980cfu/L

Voyteketal.2005

TRatNen

anaEnteroco

ccilevelsat850cfu/L

1.7

Giardia

cysts

In17%

ofsamplesatWhiteh

orse,

7.5

Giardia

cysts/100Lin

Lake

Labergefrom

surface

water(1992)

Roach

etal.1993

1.8

Cryptosp

oridium

oocytes

Cryptosp

oridium

oocytes:in

5%

samplesatWhiteh

orse,0.3

Cryptosp

oridium/100Lin

Lake

Labergefrom

surface

water(1992)

Roach

etal.1993

1.9

SS

Allunderyearling-AG:exposedto

100mg/L

werepalerin

colorandhadindistinct

parr

marksexp

osed

to300–1

000mg/L:grew

less,co

nsumed

more

oxygen

,decreasedfeed

ingtimes

andresp

onse,andwere

less

distributedwithin

thestream

exposedto

300–1

000mg/L:decreasedtolerance

totoxinpen

tach

lorophen

ol

McLeayetal.1987

1.10

Placerminingim

pacts

Taxo

nrich

ness:

low

atallstations(12to

17taxa)

LePa

ge2009

Dominanttaxo

ngroupsatmined

sites:

chironomids,

olig

och

aetes,andnem

atans

Low

number

ofmayfl

y/stonefl

ytaxa

atmined

sites—

sensitive

toco

ntaminantinputs

1.11

Ichthyo

phoniasis

Infemalesoverallinfectionranged

from

24%–4

0%

(highestin

1999and2000)

Kocanet

al.2004

Inmalesinfectionincrea

sedfrom

20%

in1999to

34%

in2003(pea

k)

1.12

Flow

Annualavg

.flow:low

atPRat10.56km

3/y

(15%<19yaverageof12.4

km3/y)

Striegletal.2007

HighatTR

:8.3%>43yaverage

1.13

Flow

Increa

sesin

winterflow:3%

atStewart

riverto

43%

atWhiteh

orse

Brabets

andWalvoord

2009

Increa

sesin

avg

.Aprilflow:10%

atTakh

iniRiver

to63%

atSalchaRiver

1.14

GW

disch

argech

anges

Largestch

anges

inGW

input:Koyu

kukR.from

1961–1

982(83%),YRatCarm

acksfrom

1952–1

995(58%),

PRnea

rFo

rtYuko

nfrom

1968–2

004(56%),(YRabove

WhiteR.from

1957–2

005(21%),YRatEagle

from

1954–2

005(23%),andTR

atNen

anafrom

1963–2

005(20%)

Walvoord

andStriegl2007

1.15

Open

waterdelta

plain

1985open

waterdelta

plain

was1210km

3,26%

consisted

oflake

sandopen

waterch

annels

Colemanetal.2008

1992open

waterdelta

plain

was2310km

3,48%

consisted

oflake

sandopen

waterch

annels


Table

1.(Continued)

Nr

Stress

variable

Effect

measu

red

Reference

1.16

Averageflow

1978–1

980:avg

.flow

was193�24km

3/a

Streigletal.2005

DOCexport

0.88Tg

C

DOC

2001–2

003:avg

.flow

was212�21km

3/a

DOCexport

0.53Tg

C

1.17

DOCexport

2004:Annualwaterfluxwas183km

/yandannualDOCflux1.21�109kg

/yRaym

ondetal.2007

2005:Annualwaterfluxwas247km

/yandannualDOCflux2.18�109kg

/y

1.18

SS

TRatNen

ana:avg

.annualSSyieldandwateryield1966–1

970:330�120gm

2/a,31.7�5.6

cmDornblaserandStriegl2009

Avg


987:559�93gm

2/a,33.7�2.6

cm

Avg


005:503�58gm

2/a,35.6�1.3

cm

AG¼Arcticgrayling;a

vg.¼

average;B¼burbot;C-K

confl.¼

Charley-KandikRiverConfluence;D

HB¼DaltonHighwayBridge;D

OC¼dissolvedorganiccarbon;FB¼Fairbanks;G

W¼groundwater;LS¼longnose

sucker;LT¼lake

trout;MeH

g¼methylmercu

ry;NP¼Northernpike;

PR¼Po

rcupineRiver;S

S¼susp

endedsedim

ent;TH

g¼totalm

ercu

ry;ToR¼TolovanaRiver;TR¼TananaRiver;TR

atFB¼TananaRiveratFairbanks;WF¼whitefish;Y

R¼Yuko

n

River.


the Yukon River basin (Hinck et al. 2006). Hg concentrationsexceeding 0.3 mg/g w/w have been shown to cause repro-ductive impairment in loons through dietary exposure(Table 1.2) (Hinck et al. 2004, 2006). Jewett et al. (2003)measured methylmercury (MeHg) in muscle (1.56 mg/g) andliver (1.20 mg/g) of northern pike at levels that exceeded Stateof Alaska Epidemiology action levels (1.0 mg/g) (SAE 2001).Duffy et al. (1998) measured 7 species of fish for muscletissue Hg in the Yukon-Kuskokwim Delta Region of Alaskaand compared these levels for individual species to humanand animal critical values established by Yeardley et al.(1998). The critical value of 0.1 mg/g of MeHg is the lowestlegal limit used in the world with 1 of 26 countries surveyedusing this value. Using this value as a reference, 85% of thesites sampled exceeded this value. Mean MeHg concentra-tions in sheefish (0.226 mg/g) and northern pike (0.718 mg/g)exceeded the critical value for both human consumption(0.2 mg/g) and animal consumption (0.1 mg/g) (Table 1.2).Methylmercury is of concern because it biomagnifies throughthe food chain and can cause neurological and developmentaldisorders in humans through indirect dietary exposure(Jewett et al. 2003).

Hinck et al. (2004, 2006) measured several contaminantsincluding Se in northern pike, burbot, and longnose sucker at10 sites in the Yukon River basin. Selenium (0.23–0.85 mg/gwet weight [ww]) concentrations at 4 sites, in all 3 speciesexceeded whole body toxicity thresholds for fish of 0.8 mg/gww (assuming 80% moisture; 4 mg/g dry weight [dw]) and0.6 mg/g ww (3 mg/g dw) for piscivorous wildlife (Table 1.1).These authors concluded that Se was a concern at these sites(Charley-Kandik, AK; Fish Hook Bend, AK; The Bridge, AK;Fairbanks, AK) (Hinck et al. 2004).

Persistent organic pollutants

Persistent organic pollutants (POPs) including polychlori-nated biphenyls (PCBs), DDT, and toxaphene have beenmeasured in water, fish tissues, and sediments in the YukonRiver basin. These contaminants were historically used ascoolants, pesticides, and herbicides but are no longer in use.Braune et al. (1999) measured organochlorines includingPCBs, DDT, and toxaphene in fish tissues from Yukon Lakes.Polychlorinated biphenyls in burbot liver (1267 ng/g), laketrout muscle (448 ng/g), and white fish muscle (61 ng/g)from Lake Laberge (1990–1994) were 25-fold, 128-fold, and610-fold higher, respectively, than levels in the same speciesand tissues in other Yukon regional lakes (Table 1.3, 1.4, and1.5). Mueller and Matz (2000) reported similar results forburbot livers sampled in the Yukon, Koyukuk, and Tananarivers in Alaska (AK). Specifically, they reported concen-trations of PCBs in burbot livers were greater than 0.11 mg/gww with the highest concentrations (1.4 mg/g) in samplescollected near Fairbanks, AK. Sediment PCB concentrationsin Lake Laberge were lower than the levels found in the fishand concentrations have decreased by 50% (from 16.1 ng/g to8.0 ng/g) over the period of 1964 to 1991 (Table 1.3) (Rawnet al. 2001). Hinck et al. (2006) reported PCB concentrationsfrom 0.02 to 0.09 mg/g ww in fish tissue samples collectedfrom 9 stations in the Yukon River basin with the highestconcentration measured in female longnose sucker nearFairbanks. None of the PCB concentrations from the researchof Hinck et al. (2006) exceeded New York State Departmentof Environmental Conservation wildlife guideline for fish of


0.11 mg/g ww. These studies suggest PCB contamination atlocations within the Yukon basin (Lake Laberge, Fairbanks)appears to be decreasing with time and chemical use.

DDT, a persistent organochlorine insecticide, remainspresent in the environment as a result of historical use datingback to the 1960s and 1970s. Hinck et al. (2006) measuredDDT in fish tissues within the basin reporting the highestconcentration in 2002 found in female northern pike(0.009 mg/g ww) and male longnose sucker (0.0047 mg/gww) (Table 1.4). These concentrations were compared tofish and wildlife toxicity thresholds from the literature(wildlife criteria of 0.2 mg/g ww; piscivorous birds of 1–3 mg/g ww; whole body fish criterion of 0.5 mg/g ww) showinglevels in 2002 of low risk to fish and wildlife in the YukonRiver basin. Rawn et al. (2001) have also showed a significantdecrease in DDT in soil samples from 1960 to 1989(Table 1.4).

Hinck et al. (2006), Mueller and Matz (2000), and Brauneet al. (1999) measured toxaphene concentrations in fish in theYukon basin. This contaminant has been classified as themajor organochlorine contaminant in the Canadian Arcticwith concentrations in Lake Laberge burbot livers (2.3 mg/gww) 125 times greater than in other Arctic lakes includingAtlin Lake, Tagish Lake, March Lake, Fox Lake, etc.(Table 1.5) (Braune et al. 1999). Toxaphene was alsodetected in whole body samples of northern pike andlongnose sucker in 2002 (0.012–0.034 mg/g ww) (Hincket al. 2006). Mueller and Matz (2000) measured concen-trations of 0.14 mg/g and 0.29 mg/g in burbot liver inFairbanks and Yukon Flats. As reviewed by Mueller and Matz(2000) and Hinck et al. (2006), acute and chronic effects oftoxaphene on freshwater fish have been observed at wholebody concentrations equal to or greater than 0.4 mg/g ww andfish for human consumption should be below the Health andWelfare Canada residue threshold of 0.1 mg/g. Historically, a‘‘consumption advisory’’ has been in place for areas in theYukon including Lake Laberge due to elevated levels oftoxaphene and other organochlorine contaminates (Diamondet al. 2005).

Bacteriological contaminants

Various waterborne contaminants were detected in surfacewaters of both the Yukon and Alaska in 2 separate studiesin 1993 and 2005 (Table 1.6–1.8) (Roach et al. 1993; Voyteket al. 2005). These contaminants include Enterococci, Giardiacysts, and Cryptosporidium oocytes. In the early 1990s,approximately 1000 Yukon residents required treatment fordiarrheal illnesses due to Enterococcus, Giardia cysts, andCryptosporidium oocytes in their water supply (Roach et al.1993). However, the report rate may be lower than actualdue to underreported cases (Roach et al. 1993).

The biological action of cysts is slowed by cold temper-atures but survival rates are prolonged through drops intemperature (Roach et al. 1993). Two villages in Alaska,Stevens Village and Nenana, reported Enterococci above theUS Environmental Protection Agency (USEPA) and State ofAlaska drinking and recreational water standards of 0 counts/L and 610 counts/L (USEPA 2000) (Table 1.6). The presenceof Giardia cysts and Cryptosporidium oocysts were found insurface waters of Lake Laberge and were measured to be athigher levels than the surface waters in other areas (Table 1.7and 1.8).

Disease and salmon migration failures

Ichthyophonus is a genus of unicellular parasites of fish andwas first identified in Chinook salmon in Alaska in the 1980s(Kocan et al. 2004). Studies show that salmon infected withthe disease ichthyophoniasis present with varying degrees ofwhite spots on their heart, liver, and skeletal muscle. Reportsalso suggest that the disease prevents the salmon from dryingproperly and results in a slight ‘‘fruity’’ smell to thoseconsuming infected fish (Kocan et al. 2004). Infected fishsuffered reduced swimming stamina and growth and maycause early onset of fatigue in migrating Chinook leadingthem to die before they reach spawning grounds (Kocan andHershberger 2006). Table 1:1.11 outlines the infectionprevalence in male and female Chinook salmon duringmigrations from 1999 to 2003. Currently no concrete dataexists on how infection occurs, but it is believed that salmonbecome infected in their time spent in the Bering Sea whilefeeding on other infected organisms (Kocan et al. 2004).

Human cancer in Alaska

Current and historical cancer rates within some areas ofAlaska are higher than seen in other states throughout theUnited States. The incidence of malignant cancer for examplefrom 1996 to 2004 was higher for all years compared to theUS rate (O’Brien and Upton 2008). Cancer incidence (per100 000 people) is significantly higher in the Fairbanks NorthStar Borough with 499 to 727 deaths occurring from 1996 to2004. The most prominent types of cancer in the North StarBorough at that time were prostate cancer and female breastcancer (O’Brien and Upton 2008). The US national cancerincidence rate from 2002 to 2006 was approximately 541 to560 deaths per 100 000 people (CDC 2007). No specificcausality was assigned in these reports. Rather, the dominantrisk factors (including tobacco, adult diet and obesity,sedentary lifestyle) known to contribute to cancer deathswere described.

STRESSOR-BASED REVIEWThe remote location of the Yukon River basin and its

low population density result in anthropogenic sources ofstress being concentrated around cities and villages along theriver and its tributaries including Whitehorse, Dawson City,Fort Yukon, Tanana, and Fairbanks. Anthropogenic stressorswhich may result in environmental changes include thedischarge of wastewater (municipal sewage) from treatmentfacilities, waste disposal, hard rock and placer mining, militaryactivities, and activities associated with oil and gas develop-ment and forestry as described below.

Wastewater treatment

Whitehorse is home to 22 898 people and is the largestsettlement in the Canadian portion of the Basin followed byDawson City with a population of 1327 people (StatisticsCanada 2006). Both communities have, at some point,discharged sewage into the Yukon River. Before 1996,Whitehorse discharged treated effluent into the Yukon Riverfrom the Porter Creek lagoon (Roach et al. 1993). When fecalcoliforms were detected in Lake Laberge surface waters,Whitehorse began an upgrade to a 3-cell lagoon system withassociated groundwater monitoring wells and completionoccurred in 1996 (Roach et al. 1993; Cabott 2007).


In 2003, Dawson City was charged by the YukonTerritorial Court under section 36(3) of the Fisheries Actfor discharging harmful substances into the Yukon River fromtheir wastewater (YG 2009a). Currently, Dawson City hasprimary treatment in place using rotostrainers that removeany solids greater than 0.75 mm (R v. C 2003). There is nodisinfection. Samples taken from the sewage have shown highlevels of ammonia, solids, pathogenic microorganisms, anddetergents (R v. C 2003). From 1983 to 1996, Dawson Cityfailed 25 of 35 LC50 toxicity tests for determining thetoxicity of the effluent to fish (R v. C 2003). Tests were alsofailed in 2000 and 2001 (R v. C 2003). The municipality hasbeen put under court order to build a new wastewatertreatment facility that conducts secondary treatment (YG2009a). The new secondary treatment plant was completed inDecember 2011 (YG 2009a).

Sewage lagoons, outhouses, and ‘‘honey buckets’’ areused extensively by aboriginal communities throughout theYukon River Basin. Many problems exist with these systemsincluding flooding, erosion, and improper maintenanceresulting in sewage discharge into surrounding water bodies(YRITWC 2002). Many communities and First Nationswithin the Yukon River Basin have expressed concern abouttheir sewage treatment and the potential risk it poses to theenvironment and to their communities (YRITWC 2002). TheAlaska Department of Environmental Conservation overseesthe permitting and installation of treatments systems. Ofthe 47 village communities in Alaska there is currently only1 community (Anatuvik Pass) operating under an activedischarge permit. The Department does not have, ormaintain, a current facility list for the 47 village communitiesin the Yukon River Basin. A study by Indian and NorthernAffairs Canada (INAC) assessed 11 wastewater systems inFirst Nation communities in the Yukon (2003). Of thosesystems, 7 had no to minimal problems, 2 needed repairs, and2 systems had potential health and safety concerns (INAC2003).

In Alaska, the only major wastewater treatment facilitywithin the Yukon River Basin is located in the city ofFairbanks. Before the 1970s, there were no wastewatertreatment facilities and in the late 1960s recorded coliformcounts upstream from Fairbanks were 50/100 mL but down-stream they were 500 000/100 mL (Frey et al. 1970). In the1970s, the population of Fairbanks jumped to 17 000 and awastewater treatment system was installed (Pearson andSmith 1975). There were 5 sewage systems in total; 3primary treatment facilities with 1 within the city, 2 at FortWainwright, and 2 secondary treatment facilities at theUniversity of Alaska Fairbanks and the International FairbanksAirport (Pearson and Smith 1975). Currently, a secondarywastewater treatment facility, called The Golden HeartsUtilities Wastewater Treatment Plant, services the city ofFairbanks as well as the University of Alaska Fairbanks, FortWainwright, College Utilities Corporation, and commercialseptage haulers (USAI 2010). It operates under a NationalPollutant Discharge Elimination System (NPDES) permit(USAI 2010).

Waste disposal

A potential source of contaminants within the Yukon Rivermay be from unregulated landfills located along the river thatleach into the groundwater and into the river (YRITWC

2002). Many First Nation communities and villages locatedalong the river have expressed concern over waste disposal intheir area (YRITWC 2002). In 1972 in Fairbanks, Stateauthorities were threatening to shut down the local landfillbecause it did not meet required standards (Pearson andSmith 1975). It is now partially redeveloped and a newregulated landfill has been installed in another area. There arealso several sites in the North where chemicals were disposedof off the record. For example, there is speculation that PCBsmay have been disposed of in the Whitehorse area because ofhigh levels of PCBs detected in Lake Laberge (Hinck et al.2004).

Mining

Mining has been occurring in the basin since the mid-1800sand currently employs thousands of workers in both theYukon and Alaska bringing in significant revenue to theeconomy (YRITWC 2002). The greatest environmentalimpact from mining operations within the Yukon River Basinis from mines that have been abandoned without siteremediation. These mine sites often have elevated levels ofmetals and contaminants that leach into groundwater andrunoff into surface water. In the Yukon, there are manyabandoned mines but the ones of greatest concern are theFaro Mine, Mt. Nansen, and Clinton Creek (YG 2009b). InAlaska alone, there are over 400 abandoned mines. It isunknown how many of these impact water quality, however,the most high-risk mine openings are near Fairbanks (USDOI2009). Two types of mining occur frequently within theYukon River Basin; placer mining and hard rock mining.Mining within Alaska is concentrated between Eagle andTanana with 90% placer mines and 10% lode mines (Hincket al. 2004). The mines are concentrated near Circle,Livengood, Fairbanks, Wiseman, Eagle, and Tanana (Hincket al. 2004).

Placer mining occurs through various techniques ofhydraulically separating large quantities of sediments thatare brought to the surface and discharged back into the streamusually after being discharged into a settling pond (Pentz andKostaschuk 1999). This may increase sediment depositionand affect local habitat (McLeay et al. 1987; Pentz andKostaschuk 1999; Dornblaser and Striegl 2009). In earliertimes, Hg was used to remove impurities from the Au andcreate a Au amalgam but it is no longer used due to its toxiceffects. However, high levels of Hg are still present in fishwithin the Yukon River as summarized above and in Table 1(Hinck et al. 2004). Many operations within Alaska havepermission to discharge effluents into small tributaries of theYukon including the Fortymile, Tolovana, Chatnika, Chena,Tanana, Koyukuk Rivers, Birch Creek and Yukon-CharleyRiver confluence (Hinck et al. 2004). Smaller tributaries oftenhave lower potential to dilute tailings discharges.

Hard rock mining also occurs to a large extent in both theYukon and Alaska. Valuable minerals are removed and wasterock (tailings) remains with some potential for seepage intolocal water sources (i.e., Se, Cd, Cu, and Zn) (Edmonds andPeplow 2000). Acid mine drainage is perhaps the mostsignificant source of mine pollution. Water from precipitationor surface flow becomes contaminated when it comes incontact with mining wastes, including waste rock and tailings.As water filters through the wastes, metallic sulfides in the oreoxidize, dissolve, and release heavy metals, forming a highly


acidic effluent. Effluent that contains mineral processingchemicals such as cyanide may also leak from leach pads, wellseals, and pipes. Seeps from tailings impoundments representanother source of contamination.

Oil and gas development and/or spills

Oil development in Alaska began in the mid-1950s. Whena large supply of oil was found in the North Slope in the1960s, plans to build a pipeline were proposed. The TransAlaska Pipeline System (TAPS) was constructed and com-plete by 1977 and carries oil 800 miles to Valdez, Alaska.It crosses the Yukon River between Stevens Village andRampart and runs south to Fairbanks crossing many of thetributaries including the Koyukuk, Tanana, Tolovana, Chena,Salcha, and Delta Rivers (YRITWC 2002; Hinck et al. 2004).There have been 3 larger oil spills within the Basin from thepipeline; 627 000 gallons at Steele Creek in 1978, 285 000gallons near Livengood in 2001, and several thousand barrelsat pump station 9 in 2010; the latter contained in acontaminant overflow area (Mach et al. 2000; Bohrer 2010).

The Trans Alaska Pipeline was built in 1974 and transportscrude oil from the North Slope of Alaska to Port Valdez inPrince William Sound crossing numerous creeks and largerivers of the Yukon River basin including sensitive terrestrialand aquatic habitats (Hinck et al. 2004). Impacts attributed topipeline operation include oil spills, water discharges, andemissions of volatile organic compounds from valves andpump stations. In December 1997, tribal leaders from theentire length of the Yukon River met in Galena, Alaska todiscuss their concerns over the health of the watershed.Residents of Stevens Village, located 20 miles upstream of theTrans Alaska Pipeline crossing of the Yukon River, expressedconcern about benzene emissions from the pipeline pumpstation (YRITWC 2002). Future plans of a natural gaspipeline do exist (Cooney 2004).

Military

Military presence in the North began growing duringWorld War II with the Japanese invasion of the AleutianIslands. Presence expanded during the Cold War when manyArctic training and air force bases were established. Function-ing bases within the Yukon River Basin currently include FortGreely, Fort Wainwright, and Eielson Air Force Base. All 3are located within the Tanana River basin (Hinck et al. 2004).Historical ‘‘bury it’’ or ‘‘out of site out of mind’’ disposalmethods prevalent during pre-environmental assessment lawresulted in leaching of contaminants from the military sites.Sites like Fort Greely’s antiballistic and cold weather trainingcenter (Walsh et al. 2003) produces concern because theDelta River watershed drains the training grounds into theTanana River. Walsh et al. (2003) found munitions residues,relatively high concentrations of research department explo-sives (RDX), high melting explosives (HMX), trinitrotoluene(TNT), 2,4-dinitrotoluene (DNT) and 2,6-DNT, Cr, Cu, Pb,Zn, and Sb in the soils where the developmental weaponshave occurred. From 1961 to 1971 the Fort Greely nuclearfacility buried waste material and a leak was discovered in1997 with site decommissioning still ongoing by the US Army(Griffeth et al. 2001). Additionally, between 1963 and 1967,a series of open-air tests of chemical and biological warfareagents were performed at the Gerstle River test site (Hummel2005).

The Fort Eielson Air Force Base in 1989 was identified asa federal ‘‘superfund’’ site due to 66 potential sources ofcontamination (Wilkinson et al. 2008). Contaminants inGarrison slough (located within the Tanana drainage)included; trichloroethane, toluene, ethylbenzene, xylene,tetrachloroethene, jet propellant, hydrocarbons, chlorinatedVOCs, and other hazardous wastes (waste oils, solvents, etc.)(Wilkinson et al. 2008). Fish tissues from Garrison sloughshowed elevated concentrations of DDT, DDD, and DDE(Wilkinson et al. 2008). Bioaccumulation in migratory fishposes a potential mechanism for contaminant transport acrossthe basin, particularly through feeding on exposed macro-invertebrates.

The Chena River, which empties into the Tanana River,runs through Fort Wainwright and was placed on the listof ‘‘superfund’’ sites by the USEPA in 1990 (ADEC 2009).Taku Gardens reports 115 000 mg/kg of PCBs, munitionsrelated debris, buried drums, scrap metal, concentratedpetroleum, chlorinated solvents, herbicides, pesticides, diox-ins/furans, Pb, nitroaromatics, and propellants (ADEC 2009).All contaminants are listed as a threat to human andenvironmental health and remediation of the site is inprogress (ADEC 2009).

Historic construction projects and urban development

Expansion during the Au rush and World War II resultedin use of chemicals not previously found in the Yukon.Polychlorinated biphenyls transported during constructionof the Alaska Highway (INAC 2003) resulted in 3840 L ofliquid PCB and 183 200 kg of PCB contaminated soil that wasremoved from the Yukon and disposed at Swan Hills becauseof the risk to human and environment health (INAC 2010).Many First Nation communities express concerns aboutconstruction contaminants, including an old railroad tie plant(Carcross Tagish First Nation), discarded barrels and vehiclesat Johnson Crossing (Teslin First Nation), and barrels filledwith various substances (left by the military in 1950s)scattering the banks of the Yukon River at Galena (YRITWC2002). The significance or potential risk associated with thisstressor source is unknown.

Long range transport and deposition

Atmospheric currents are key pathways for long-rangetransport of contaminants (heavy metals, organic pollutants,radionuclides) from industrial and agricultural sources toArctic regions (Hinck et al. 2004). Global air transport is animportant source of pollutant loadings to the Yukon Riverbasin. Deposition over forming ice creates a storage andtransport mechanism to the aquatic system. Typically thesecontaminants bioaccumulate in organisms and Arctic foodchains. Hg, for example, is a key metal transported throughthe atmosphere to the Yukon and has been quantified insnowmelt and correlated with tissue burdens of Hg innorthern pike and longnose sucker (Hinck et al. 2004).

Forests

Disturbances like forest fires and pest infestation occurfrequently from May to September. In the Yukon Territoryfrom 1992 to 2002, 1463 forest fires occurred in total andover 1.5 million ha burned (YCS 2003). In 2009, approx-imately 3 million acres burned in Alaska (approximately1.2 million ha) (Lamb and Winton 2009). In 2007, a


significant number of Yukon Territory white spruce wereobserved to be dead and dying in areas along the Yukon River(YG 2008). The cause of this initial mortality was determinedto be drought but during the wet summer of 2009 an area ofapproximately 2546 ha along the Yukon River (YG 2008) wasdetermined to be impacted by the Northern Spruce engraverbeetle. In Alaska from 2007 to 2009, white spruce wereinfested with the spruce budworm along the Yukon River atthe Dalton Highway Bridge (Lamb and Winton 2009).Additionally, an infestation of the willow blotch miner wasnoted as one of the most severe infestations in the area (YG2008). Approximately 136 336 ha of willow were attacked bythe willow leaf blotch miner with the mass of infestationoccurring on the Yukon mainstem between Circle and Beaverand along the Tanana River (Lamb and Winton 2009). Forestfires and pest infestations occur commonly through forestecosystems and should be an important stressor to considerin any cumulative effects assessment where causal sources ofenvironmental change require consideration.

Climate change

Increasing temperatures in subarctic and Arctic regionshave resulted in thawing of permafrost, drying of lakes,common infestations of beetles in pine tree stands, increasedfrequency of forest fires, and accelerated shoreline erosion(ACIA 2004; Prowse et al. 2006). These changes willdramatically alter wildlife habitats and threaten traditionallifestyles of Indigenous peoples. Alaska and northwesternCanada, in particular, have been experiencing some of thelargest increases in ambient temperature of any region onthe planet. Evidence suggests that freshwater flow from theArctic’s major rivers is increasing as average air temperaturesrise (Peterson et al. 2002). Alterations in flow is onevulnerability associated with climate change that couldsubsequently alter pH of the Yukon River and its tributaries,influencing the solubility and chemical speciation of thevarious constituents, particularly metals (Environment Yukon2011). Moreover, with increasing permafrost thaw, loads of N(organic and inorganic) may increase.

On the pan-Arctic scale, the Yukon River is fundamental tothe function of the Bering Sea and Bering Strait ecosystems(Lisitsysn 1969; Opsahl et al. 1999; Hansell et al. 2004).Therefore, impacts to the Yukon River have implications forthe circulation and species distribution in the coastal zone ofthe Yukon-Kuskokwim Delta (an area the size of Massachu-setts), and for large-scale fisheries and marine ecosystems inthe Bering Sea, Bering Strait, and Arctic Sea. Increases infreshwater runoff are expected to affect ocean stratification,circulation, and global climate processes through the slowingof the thermohaline circulation (Schiller et al. 1997; Weaveret al. 1999; Ottera et al. 2003).

ACCUMULATED STATE ASSESSMENTAn accumulated state assessment is one element necessary

to conduct a watershed CEA where changes are measured inan aquatic system over time and space. This information iscritical to understand the level of existing environmentaldeterioration. Ideally, this is done quantitatively usingregional monitoring data and statistical determinations ofchange relative to a defined benchmark of ‘‘normal’’ based onnatural variation (Dube et al. 2013a, 2013b, this issue).Regional monitoring databases do not commonly exist but

their importance for CEA is being recognized (Main et al.2011; Wrona et al. 2011). Often for assessments of this kind,integration of many different sources of data are required(Squires et al. 2010). In this article, we illustrate the value ofconducting a literature review as a qualitative accumulatedstate assessment to support more quantitative assessments(see Dube et al. 2013a, 2013b, this issue).

In this light, this literature review has identified a total of7 ‘‘hot spot’’ areas of change in the Yukon River Basin(Figure 1). These areas include Lake Laberge, Yukon River atDawson City, the Charley and Yukon River confluence,Porcupine and Yukon River confluence, Yukon River at theDalton Highway Bridge, Tolovana River near Tolovana, andTanana River at Fairbanks.

Lake Laberge

Lake Laberge was identified as a hot spot because ofhistorical contamination, from the 1940s and 1960s, andwaterborne contamination of surface waters. Since the mid-1990s, levels of contaminants in fish tissues have declined(Hinck et al. 2004) although PCBs, DDT (and derivates), andtoxaphene can still be found in fish tissue and soil aroundthe area (Table 1.3, 1.4, and 1.5). In addition, toxaphenemeasured in burbot liver continues to exceed threshold levelsfor human consumption (Hinck et al. 2004). Risk is increasedby Whitehorse’s action to resume discharge of wastewaterdischarge after Giardia cysts and Cryptosporidium oocyteswere found in the surface waters of Lake Laberge (Table 1.7and 1.8). These studies were conducted in 1993 and it isunclear of the ongoing risk to humans who drink untreatedwater from Lake Laberge in the absence of more recentmonitoring or publications. The Yukon River including LakeLaberge is a location of extensive tourism, kayaking, canoeing,and hiking. The Yukon River Quest and Yukon 1000 canoeand kayak races, for example, are the longest races of theirkind bringing competitors from around the world. In 2010and 2011, Dr. M. Dube, an author of this article, participatedas a scientist during these events and was aggressivelychallenged by guides and journalists who accompanied herwhen she required water treatment for racers as a basic healthand safety consideration in the absence of more recent data(Casey 2011). Clearly the need for accumulated stateassessments has direct relevance to understanding river healthand supporting use of the river watershed for recreation andtourism. Risk cannot be accurately assessed in the absence ofmore recent data to confirm the efficacy of municipal effluenttreatment.

Yukon River at Dawson City

Dawson City is a hotspot along the river because of thequality of effluent discharged from the wastewater treatmentfacility. The city itself is small, and the direct impacts ofthe effluent on the Yukon River are not known. For severalmonths of the year, the effluent fails toxicity tests andelevated bacterial levels exist (R v. C 2003). The newsecondary wastewater treatment facility should produce atreated effluent that meets water quality standards and thisshould be confirmed with follow-up monitoring.

Yukon River near the Charley-Kandik river confluence

The Charley-Kandik (C-K) river confluence location hadSe in fish tissues that exceeded guidelines (0.6 mg/g) for the


protection of piscivorous wildlife (Hinck et al. 2004).Toxaphene was highest in a northern pike and levelsapproached thresholds (35–900 ng/g) for growth and repro-ductive failure in freshwater fish. Toxaphene use as apesticide historically may account for elevated levels althoughlong-range transport may also be a factor. Increased miningactivity between Eagle and Tanana may also be a factorcontributing to increased Se concentrations.

Porcupine and Yukon River confluence

The Porcupine River is one of the few areas within thebasin that is underlain by a continuous layer of permafrost.The permafrost in this area is deteriorating and is accom-panied by thermokarst formation and in some areas surfacewaters underlain with permafrost have drained (Striegl et al.2007). Furthermore, from 2001 to 2005 average annual flowsin the Porcupine River were 15% lower than the 19-yearaverage (Table 1:1.12). Changes in permafrost coverage couldbe affecting groundwater and river flow dynamics therebyaffecting the biogeochemical cycles. Such a change coulddisturb the Yukon River’s productivity through altering C andnutrient cycling.

Yukon River at the Dalton Highway Bridge

The Dalton Highway Bridge is the location where theTrans Alaska pipeline crosses the Yukon River. In 1978,55 gallon oil drums were reported downstream of the bridge ayear after construction was completed (Dapkus et al. 1978).Hinck et al. (2006) found that all pike sampled in this areahad levels of Hg exceeding 0.3 mg/g (Table 1:1.2). Se levelswere also exceedingly high and approached levels dangerousto piscivorous wildlife (Table 1:1.1). White spruce infestationin this area yields an altered forest leading to a modification ofC and nutrient unloading.

Tanana River at Fairbanks and Nenana and Tolovana Riverat Tolovana

The Tanana River is one of the major tributaries of theYukon River and the Tolovana River drains into the Tanana.Military, mining, oil and gas development, and municipalwastewater discharge have affected these rivers and climatechange is altering groundwater inputs and average annualflows (Table 1:1.12, 1.13, and 1.14). High levels of Hg, Se,PCB, and DDT were detected in fish within the Tanana Riverwith the high levels of PCB, DDT, and Se at Fairbanks. TheTolovana River at Tolovana also showed high levels of Hg,toxaphene, and DDT. Elevated cancer rates in FairbanksNorth Star Borough (includes Fairbanks and Tolovanaresidents) were also reported confirming the need for researchto explore potential causal links. Military facilities at FortGreely, Fort Wainwright, and the Eielson Air Force Base havereleased chemicals of concern that remain in soils and surfacewaters in the area. Mining in the area, around Fairbanks andnear Tolovana and effluents discharged into tributaries of theTanana River require monitoring. The Trans Alaska pipelinetraverses through this area as well and 2 significant spills haveoccurred at Livengood near the Tolovana River and Pumpstation 9. The Tanana River is fairly sensitive to climatechange as its headwaters originate in the mountains, in thesouthern portion of the basin, where alpine glaciers andperennial snowfields are receding (Striegl et al. 2007).

Average annual flows have increased over a 4-year periodfrom 2001 to 2005 (Table 1:1.12) and at Nenana ground-water input also increased significantly (Table 1:1.14).Increases in groundwater input and changes in stream flowwill alter sediment discharge rates and biogeochemical cycleswithin this river and the Yukon River.

CONCLUDING COMMENTSThe assessment of cumulative change in river systems has

been significantly affected by a lack of methodology and mostcertainly by a lack of data at the temporal and spatial scalesrequired. To facilitate an accumulated state assessment for theYukon River basin, a critical literature review was conductedand 6 hot spots were identified where further investigation isrequired. Climate change, long-range transport, mining, pastuse of chemicals for pest control, sewage discharges, andmilitary operation have occurred in the basin and contributedto contamination of fish and surface waters, altered hydrol-ogy, and shifted in biogeochemical loads. Although a riverecosystem travels on a geological time scale, impacts fromhuman activities from a short time period can have significantand lasting effects (e.g., spraying in the 1950s continues toaffect chemical levels measured in 2000s) as evidenced in theYukon basin.

Limitation of data and knowledge to assess cumulativechange is currently our most significant challenge. TheIndigenous people of the Yukon River Basin have an extensiveoral history and hands-on experience that encompassesboth the published reports and direct experience. Becauseknowledge transmission, within Indigenous society, occursthrough cultural mediums there exists an unknown amountof information that has never been reported in formalliterature. Our understanding of regional influences onsystem-wide ecological balance does not, or even attempt,to account for Indigenous knowledge of change. Thus,analysis of effects in the Yukon River Basin would greatlybenefit from a mechanism that bridges multiple knowledgesystems (Western and Indigenous).

Acknowledgment—Funding was provided by the CanadianWater Network (Dube). We thank Vince McMullin, ElisePietroniro, and Jeff Lettvenuk.

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