J. Great Lakes Res. 24(1):3-11Internat. Assoc. Great Lakes Res., 1998

Organochlorines, Mercury, and Selenium in Great Blue Heron Eggs fromIndiana Dunes National Lakeshore, Indiana

Thomas W. Custer1*, Randy K. Hines1, Paul M. Stewart2,

Mark J. Melancon3, Diane S. Henshel4, and Daniel W. Sparkss

I United States Geological SurveyBiological Resources Division

Upper Mississippi Science CenterPO. Box 818

La Crosse, Wisconsin 54602

2United States Geological SurveyBiological Resources Division

Lake Michigan Ecological Research Station1100 N. Mineral Springs Road

Porter, Indiana 46304

3United States Geological SurveyBiological Resources Division

Patuxent Wildlife Research CenterLaurel, Maryland 20708

4School ofPublic and Environmental AffairsIndiana University

Bloomington, Indiana 47405-2100

5u.S. Fish and Wildlife ServiceBloomington Ecological Field Office

Bloomington, Indiana 47403

ABSTRACT. In 1993, 20 great blue heron (Ardea herodias; GBH) eggs (one per nest) were collectedfrom a colony at the Indiana Dunes National Lakeshore, Indiana (INDU). The eggs were artifIcially incu­bated until pipping and were then analyzed for organochlorines, mercury, and selenium. Livers ofembryos were analyzed for hepatic microsomal ethoxyresorufln-O-dealkylase (EROD) activity. Brainswere measured for asymmetry. Egg-laying began in early April and the mean clutch size was 4.2 eggs perclutch. Organochlorine concentrations were generally low (geometric mean p,p'-DDE = 1.6 f.lg/g wetweight; polychlorinated biphenyl [PCB] = 4.9 f.lg/g); however, one egg had elevated concentrations ofp,p' -DDE (13 f.lg/g) and PCBs (56 f.lg/g). EROD activity in the embryos analyzed from INDU was not ele­vated. The frequency (II %) ol brain asymmetry was low. Eggshells averaged 3.4% thinner than eggshellscollected prior to the use of DDT. Mercury (geometric mean = 0.9 f.lg/g dry weight) concentrations inGBH eggs were within background levels. Selenium (4.0 f.lg/g dry weight) concentrations in eggs wereabove background levels, but below a concentration threshold associated with reproductive impairment.

INDEX WORDS: Organochlorines, great blue herons, PCB congeners, mercury, selenium, IndianaDunes National Lakeshore.

"Corresponding author. E-mail: tom_w_custer@nbs,gov

3

4 Custer et al.

minant exposure of GBHs nesting in INDU by de­termining contaminant concentrations in eggs col­lected from the GBH colony.

FIG. 1. Map of northwest Indiana showing loca­tion of the great blue heron colony in relationshipto municipal landfills, incinerators, superfundsites, and Comprehensive EnvironmentalResponse, Compensation, and Liability Informa­tion System (CERCLIS) sites. Adapted with per­missionfrom PAHLS (1993).

METHODS

On 28 April 1993, 20 GBH eggs (one egg pernest) were collected from the INDU colony locatedin Porter County, Indiana (Fig. 1; 41 N 30'43", 86W 52.5'33") under appropriate state and federalpermits. A professional tree climber ascended two30 m beech trees (Fagus grandifolia) and used a 2to 8 m extendable pole with a nylon stocking cupattached to the end of the pole to collect eggs thatwere out of reach (Hines and Custer 1995). Aftercollection, the eggs were placed in foam-lined con­tainers, lowered to the ground, placed in a tempera­ture-controlled (37°C) portable incubator, and thentransported to the Upper Mississippi Science Cen­ter, LaCrosse, Wisconsin. Eggs were then candledfor viability, randomly placed on shelves in an incu-

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INTRODUCTION

The northwest corner of Indiana is an areaformed by the recession of glacial Lake Michiganand includes the significant ecological resources ofthe Indiana Dunes National Lakeshore (INDU) andIndiana Dunes State Park (Fig. 1). The INDU in­cludes over 6,800 hectares of dune and swaletopography that contain over 1,300 species of vas­cular plants (PAHLS 1993). INDU provides astopover for more than 330 species of migratorybirds and is summer residence to over 110 speciesof breeding birds. It also serves as a natural transi­tory stopover for spring and fall migrants (Brock1986). The northwest corner of Indiana is also anarea of poor air, water, and sediment quality (Fig. I;PAHLS 1993, Indiana Department of Environmen­tal Management 1988). Contaminants have been re­leased from municipal, industrial, and non-pointdischarges, including persistent organochlorines,petroleum products, heavy metals, and sewage ef­fluents (Hoke et al. 1993, International Joint Com­mission 1985).

Few data exist on environmental contaminantlevels in the wildlife that inhabit INDU. Steffeck(1989) found elevated levels of mercury (0.354f.,lg/g wet weight) in snapping turtles (Chelydra ser­pentina) and elevated selenium levels (2.0 f.,lg/g wetweight) for earthworms (Lumbricus rubellus andDendrobaena octaedra) collected within INDU. El­evated contaminant concentrations in fish popula­tions have resulted in fish consumption advisoriesfor polychlorinated biphenyls (PCBs) and mercuryfor Lake Michigan and inland tributaries (IndianaState Department of Health 1997). No data areavailable on contaminant levels in birds from theINDU.

A breeding colony of approximately 120 pairs ofgreat blue herons (Ardea herodias; GBH) occurs onthe INDU (Randy Knutson, Park Resource Manage­ment, INDU, personal communication, Fig. 1). Thecolony has been active since the early 1950s (Tay­lor et al. 1982). GBHs in other portions of theirrange accumulate residues (Custer et al. 1997) andare sensitive to environmental contaminants. Con­centrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin,the most toxic of the polychlorinated dibenzodiox­ins, observed in GBH embryos from the Strait ofGeorgia, British Columbia, were correlated withethoxyresorufin-O-dealkylase (EROD) activity(Bellward et al. 1990), depressed embryonic growth(Hart et al. 1991), and brain asymmetry (Henshel etal. 1993). Our objective was to evaluate the conta-

Contaminants in Great Blue Heron Eggs 5

bator (37.5°C, 60-65% humidity), and checked atleast daily for signs of pipping.

At pipping, the embryos in all viable eggs wereremoved from the shells, examined for deformities,and weighed (± 0.1 g). Immediately followingdeath by decapitation, the liver was removed andweighed (± 0.001 g). Portions « 1 g) of the liver ofall embryos were placed into two cryotubes, quickfrozen in liquid nitrogen, stored in a Revco UltraLow Freezer at -85°C, and within 6 months ana­lyzed for cytochrome P450-associated monooxyge­nase activities.

Eggs were randomly divided into two groups; 10eggs for chemical analyses and 10 eggs were usedfor anatomical measurements of embryos. Contentsof eggs that did not pip in the anatomical subsampleand all embryos and egg contents in the chemicalanalysis subsample were placed in chemically cleanjars and frozen at -20°e. Samples within the chemi­cal analysis group included the entire contents ofeggs, except that livers were removed from embryosat pipping. Within the anatomical subsample, em­bryos that survived to pipping were decapitated.After decapitation, the skull caps of the heads in theanatomical group were opened and the heads placedin a 10% buffered formalin solution and refrigerated.

Date of egg-laying for eggs in 16 nests was esti­mated based on pipping date. In order to estimatethe date when the eggs were laid, day of laying wasassigned day 0, day of pipping was day 27, and dayof hatching was day 28 (Pratt 1970). Estimates forfledging (first flight) were made by adding 60 daysto the hatching date based on a California studyshowing the youngest age at which GBHs flew(Pratt 1970).

Eggshell thickness was measured to the nearest0.01 mm with a micrometer after the shells haddried at room temperature for at least 1 month. Amean thickness value was derived from three mea­surements taken at the equator of each egg and in­cluded the shell and shell membranes.

The following organochlorines were analyzed inGBH eggs by Mississippi State Chemical Labora­tory, Mississippi State University, Mississippi State,Mississippi: aldrin; a-, 13-, y- and D-benzene hexa­chloride (HCH); a- and y-chlordane; oxychlordane;cis-nonachlor; trans-nonachlor; dieldrin; endrin;hexachlorobenzene (HCB); heptachlor epoxide;mirex; toxaphene; o,p' -DDD; o,p'-DDE; o,p'-DDT;p,p'-DDD; p,p'-DDE (DDE); p,p'-DDT; total PCBs;and PCB congeners with Ballschmiter-Zell (BZ)numbers 77, 105, 114, 118, 126, 156, and 169. TotalPCBs were estimated based on Aroclor equivalents.

Concentrations of PCB 118 may be overestimatedbecause it coeluted with PCB 106. Samples werehomogenized, mixed with sodium sulfate, and soxh­let extracted with hexane. After the percent lipidwas determined, lipids were removed by Florisilcolumn chromatography and the eluate was sub­jected to further cleanup on a silicic acid column toseparate PCBs from other polar organochlorines.Following silicic acid column chromatography, pes­ticides and total PCBs were determined by electroncapture gas chromatography. Samples for specificPCB congeners were prepared as above, but thePCB fraction from the silicic acid column was fur­ther fractionated using an AX-21 carbon on an acti­vated silica gel column to isolate non-ortho andmono-ortho PCBs. PCB congeners were analyzedby electron capture detection. The nominal limits ofdetection for organochlorines were 0.0001 flg/g wetweight for PCB congeners, 0.05 flg/g wet weight fortotal PCBs and toxaphene, and 0.01 flg/g wet weightfor the remainder of the organochlorines. Duplicateanalyses, spikes, blanks, and GC/Mass Spectrometryconfirmation analyses were conducted on 10% ofthe total number of samples analyzed.

Egg contents were analyzed for mercury and se­lenium at Research Triangle Institute, Research Tri­angle Park, North Carolina. Samples werefreeze-dried for determination of moisture and thenground prior to nitric acid digestion in a cappedTeflon vessel using a CEM microwave oven. Sele­nium concentrations were determined usinggraphite furnace atomic absorption with either aPerkin-Elmer Zeeman 3030 or 4100ZL atomic ab­sorption spectrometer. Mercury concentrations weredetermined using cold vapor atomic absorption witha Leeman PS200 Hg analyzer. Nominal limits ofdetection were 0.1 flg/g dry weight mercury and 0.5flg/g dry weight selenium. Duplicate analyses,spikes, and blanks were conducted on 10% of thetotal number of samples analyzed. Two standardreference materials, dogfish liver and dogfish mus­cle, were analyzed concurrently for concentrationsof mercury and selenium. All results for mercuryand selenium are reported on a dry weight basis.Mean moisture content was 83.7%. Quality assur­ance and quality control of the organochlorine andtrace element analyses were approved by the Patux­ent Analytical Control Facility, U.S. Fish andWildlife Service, Laurel, Maryland.

The toxic potency of the aryl hydrocarbon-active(Ah-active) PCB congeners relative to 2,3,7,8-tetra­chlorodibenzo-p-dioxin (TCDD) was estimated foreach sample by summing the products of the mea-

6 Custer et al.

sured concentrations and TCDD toxic equivalencyfactors (TEFs) as suggested by Kennedy et al.(1996) and Safe (1990). These two methods wereselected in order to make comparisons with earlierstudies (Rattner et al. 1994, Custer et al. 1997). TheTEFs of Kennedy et al. (1996) are based uponEROD activity measured in cultured chicken em­bryo hepatocytes. The Safe TEFs are based upontoxic responses in mammals. Estimated toxicity isexpressed as toxic equivalents (TEQs, pg/g ofsample).

Cytochrome P450-associated monooxygenase ac­tivities were assayed at Patuxent Wildlife ResearchCenter, Laurel, Maryland. Methods are described indetail in Melancon (1996). Individual liver sampleswere homogenized and hepatic microsomes wereprepared by differential centrifugation. CytochromeP450-associated monooxygenase assays includedthe fluorometric determination of EROD. ERODactivity in GBH embryos in this study was com­pared to values from a reference colony locatednear MacDougall, Minnesota (Custer et al. 1997).Eggs from the MacDougall colony had the lowestPCB concentrations (geometric mean = 1.0 Ilg/gtotal PCBs) among ten colonies on the Upper Mis­sissippi River. Embryo livers in this study and thosefrom the MacDougall colony were assayed concur­rently for EROD activity.

Measurements of brain morphometry were madeas described in Henshel et al. (1993, 1995). Thewidth, angle, height, and depth of the right and leftside of each brain were measured using an engi­neering ruler with 0.5 mm gradations. If the twosides of the brain had the same measurement, thesample was classified as symmetrical. If the twomeasurements differed by 0.25mm or more thebrain was classified as asymmetrical.

Contaminant concentrations were log transformed,using base 10 logarithms, in order to make the datacomparable with earlier reported measurements(Custer et al. 1997). Means were calculated onlywhen half or more of the samples had detectableconcentrations. For purposes of analysis, samplesbelow the detection value were given one-half thedetection limit for use in calculation of the means.

RESULTS

Oxychlordane, cis-nonachlor, trans-nonachlor,dieldrin, heptachlor epoxide, p,p' -DDE, total PCBs,and PCB congeners 105, 114, 1181106, and 156were detected in all ten samples from INDU (Table1). Endrin, hexachlorobenzene, mirex, toxaphene,

p,p'-DDD, p,p'-DDT, and PCB congener 126 weredetected in five or more samples, while f)-HCH,a-chlordane, and PCB congeners 77 and 169 weredetected in less than half of the samples. The fol­lowing organic compounds were not detected:a-, y-, and b-HCH; b-chlordane; o,p'-DDD; o,p'­DDE; and o,p'-DDT. Mean concentrations of p,p'­DDE and PCBs were 1.6 and 4.9 Ilg/g, respectively(Table 1). One egg had elevated p,p'-DDE (13.0Ilg/g) and PCB (56 Ilg/g) concentrations.

The geometric mean toxic equivalents were 465pg/g (arithmetic mean = 958 pg/g) based on Safe(1990) TEFs and 929 pg/g (arithmetic mean =2,147 pg/g) based on Kennedy et al. (1996) TEFs(Table 1). The seven PCB congeners measured hereaccounted for 8.0 percent of the total PCBs.

Mercury and selenium were detected in all ten ofthe eggs analyzed. Concentrations of mercury aver­aged 0.91 Ilg/g dry weight and one sample reached4.6 Ilg/g dry weight (Table 1). Selenium concentra­tions averaged 3.98 Ilg/g dry weight. All seleniumsamples exceeded 2.0 Ilg/g dry weight, with six outof ten exceeding 4.0 Ilg/g dry weight.

Eggshells of INDU herons (mean = 0.380 mm± 0.007 SE [range 0.303-0.420], Table 2) were3.4% thinner than eggs collected pre-1947 fromsouthern Canada (mean =0.393 mm; Anderson andHickey 1972). EROD activity in livers from em­bryos in this study was not significantly different(F = 1.08, df = 1, P =0.31) than a value from a ref­erence location in MacDougall, Minnesota (Table2). The width, angle, and depth of 1 of 9 (11 %) em­bryo brains were asymmetrical (0.25 mm); none ofthe brains were asymmetrical for height.

Sixteen of the 20 eggs (80%) survived until pip­ping and no abnormal embryos were observed.Eggs hatched in the field (n = 1) and in the labora­tory incubator (n = 15) between 29 April and 17May; the median date of pipping was 6 May. We es­timated that egg-laying in 16 clutches began be­tween 1 and 19 April; the median date of first egglaid was 8 April. Estimated fledging (first flight)dates of the 16 eggs varied from 31 May through 18June with a median fledgling date of 7 June. Clutchsize varied from 3 to 5 eggs per nesting attempt andaveraged 4.2 eggs (four with 3 eggs, eight with 4eggs, and eight with 5 eggs).

DISCUSSION

Total PCB concentrations in GBH eggs (geomet­ric mean =4.9 Ilg/g) collected from INDU were in­termediate compared to those found in GBH eggs

Contaminants in Great Blue Heron Eggs 7

TABLE 1. Concentrations of organochlorines,mercury, and selenium in 10 great blue heroneggs from Indiana Dunes National Lakeshore,1993.

Concentration (flg/g)a

Geometric

TABLE 2. Ethoxyresorufin-O-dealkylase activityin great blue heron embryos from a referencelocation (MacDougall, Minnesota) and the Indi­ana Dunes National Lakeshore, 1993.

Ethoxyresorufin-O-dealkylase activity(pmol/min/mg protein)

1988, Blus et at. 1980, Elliott et at. 1989), UpperMississippi River (UMR, Custer et at. 1997), andthe Gulf coast of Texas (King et at. 1978). How­ever, egg PCB concentrations were lower than thosefound in eggs collected from the Tennessee Valley(Fleming et al. 1984), Quebec (Laporte 1982), Nue­ces Bay, Texas (Mitchell et al. 1981), and the GreatLakes and north Atlantic regions (Ohlendorf et al.1979). These values are only somewhat comparablebecause organochlorine concentrations in bird eggshave declined over the past 20 years (Custer et at.1997).

Mean PCB concentrations in GBH eggs in thisstudy (geometric mean =4.9 flg/g) were lower thanthe levels reported to affect reproduction in othercolonial waterbird species. Concentrations of 14flg/g PCBs in double-crested cormorant (Phatacro­corax auritus) eggs were associated with 15% eggmortality (calculated from Tillitt et at. 1992). How­ever, concentrations of 20 to 40 flg/g PCBs inCaspian tern (Sterna caspia) eggs did not seem toreduce productivity (Struger and Weseloh 1985).Also, GBHs nesting in Nueces Bay, Texas hadhigher mean concentrations of PCBs in eggs (geo­metric mean = 6.2 flg/g PCBs) than found in thisstudy and fledged 1.6 young per nest (Mitchell etal. 1981), a value within the range reported for sta­ble populations elsewhere (Pratt 1970, Henny andBethers 1971, BIus et al. 1980).

The calculated toxicity of PCBs in our GBH eggs(arithmetic mean = 958 pg/g TEQs based on Safe[1990] TEFs) was intermediate to other locationswhere PCBs are dominant relative to TCDD. Toxicequivalents in GBH eggs collected from 10 loca­tions on the Upper Mississippi River were about30% as high (292 pg/g TEQs based on Safe [1990]TEFs) and were not associated with cytochromeP450 induction or embryo deformities (Custer et at.1997). In contrast, the toxicity of PCBs in black­crowned night-heron (Nycticorax nycticorax) eggs

Chemical mean Range

f3-benzene hexachloride - b 9NDc-0.08a-chlordane 7ND-0.03Oxychlordane 0.07 0.02-0.45Cis-nonachlor 0.07 0.01-0.48Trans-nonachlor 0.19 0.03-1.10Dieldrin 0.26 0.05-0.76Endrin 0.01 5ND-0.01Hexachlorobenzene 0.01 4ND-0.02Heptachlor epoxide 0.08 0.02-0.46Mirex 0.01 2ND-0.17Toxaphene 0.3 2ND-6.4p,p'-DDD 0.03 2ND-0.40p,p'-DDE 1.58 0.23-13.00p,p'-DDT 0.02 3ND-0.12Total PCBs 4.9 0.8-56.0PCB Congener: 77 7ND-0.0027

105 0.0871 0.0096-0.830114 0.0057 0.0008-0.089118/1 06 0.2647 0.0350-1.399126 0.0005 2ND-0.012156 0.0349 0.0054-0.460169 8ND-0.00 12

Safe TEQsd 0.000465e 0.000051-0.004066Kennedy TEQsd 0.000929 f 0.000088-0.009715Mercury 0.908 0.33-4.64Selenium 3.976 2.72-5.17

aOrganochlorines are presented in flg/g wet weight andmercury and selenium in flg/g dry weight.

bDashed lines indicate that no mean was calculated, be­cause more than half of the values were below the levelof detection.c ND = not detected; number preceding "ND" is thenumber of samples not detected.d Toxic equivalents of PCB congeners relative to2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) were esti­mated by summing the products of the measured concen­trations and TCDD toxic equivalency factors suggestedby Safe (1990) and Kennedy et ai. (1996). PCB con­geners measured include numbers 77, 105, 114, 118,126,156,169; (congener 118 coeluted with 106).e Arithmetic mean was 0.000958 flg/g.f Arithmetic mean was 0.002147 flg/g.

from other locations in North America. PCB con­centrations found in eggs collected in this studywere higher than those found in GBH eggs from thenorthwest U.S. and British Columbia (Fitzner et al.

Location

ReferenceIndiana Dunes

n Mean ± SE Range

II 12.9 ± 2.3 1.7-29.316 16.6 ± 2.5 5.0-41.0

8 Custer et al.

from Green Bay, Wisconsin, was three times greaterthan our samples (2,997 pg/g TEQs based on Safe[1990] TEFs [Rattner et al. 1994]) and was associ­ated with cytochrome P450 induction (Rattner et al.1994). Black-crowned night-herons embryos froman earlier collection in Green Bay demonstrated cy­tochrome P450 induction and increased percentageof abnormal embryos (Hoffman et al. 1993).

Total PCBs and toxic equivalents in eggs fromIndiana Dunes were apparently not sufficiently highto induce EROD activity. Even though total PCBswere qualitatively higher in this study (geometricmean = 4.9 flg/g) than reference samples from theUpper Mississippi River (geometric mean = 1.0flg/g, MacDougall, Minnesota, colony, Custer et aI.1997), EROD activity (mean = 16.6 pmollminute/mg microsomal protein) was not significantlyhigher than reference samples (mean = 12.3pmollminute/mg microsomal protein).

The lower frequency of brain asymmetry in GBHembryos at INDU (11 % INDU vs 47% Upper Mis­sissippi River) and the associated higher total PCBs(4.9 vs 3.0 flg/g) and TEQs (929 vs 540 pg/g) sup­port earlier results (Custer et al. 1997) which sug­gested that PCBs were not correlated with brainasymmetry in GBHs. In that study (Custer et aI.1997), EROD activity was higher in GBH embryoswith asymmetrical brains than symmetrical brains.However, because total PCBs and TEQs were notcorrelated with EROD activity, no relationship be­tween brain asymmetry and PCBs or TEQs was ap­parent. It should be noted that direct comparisonsbetween PCBs and brain asymmetry could not bemade, because PCBs were not measured in embryosselected for brain measurements.

It is possible, as mentioned earlier (Custer et al.1997), that a chemical or chemicals not measuredon the Upper Mississippi River and not present atINDU was responsible for the higher frequency ofasymmetry on the Upper Mississippi River. It isalso possible that the stress of the 1993 flood event(Custer et al. 1996) on GBHs nesting on the UpperMississippi River, regardless of contamination, mayhave influenced EROD activity and brain asymme­tryon the Upper Mississippi River. The GBHs nest­ing in the more flooded areas of the UpperMississippi River delayed nesting and had smallerclutch sizes compared to areas less affected by theflood (Custer et aI. 1996). On the other hand, thesample size of brains measured for symmetry atINDU (n = 9) may have been too small for an accu­rate evaluation of the percent that were asymmetri­cal. Further studies on asymmetry in GBH embryos

are obviously required to test these varioushypotheses.

Based on the high concentrations of PCBs intheir eggs (15 and 56 flg/g) , two female GBHs inthis study were probably feeding at PCB contami­nated sites. It is uncertain whether these contami­nants were obtained in Indiana near the nestingcolony or prior to the nesting season at some otherlocation. Local exposure could be determined bymeasuring accumulation of organochlorines (flg/d)in heron chicks (Custer and Custer 1995) or by ana­lyzing prey items obtained from the chicks oradults. Fish tissue data collected by the IDEM fromLake Michigan, Trail Creek, and Little and GrandCalumet rivers have concentrations of PCBs suffi­ciently elevated to warrant fish consumption advi­sories (Indiana State Department of Health 1997).Portions of these waterbodies are within the forag­ing range of this heron rookery.

Although p,p'-DDE concentrations (geometricmean = 1.6 flg/g) in GBH eggs from INDU weregenerally equal to or lower than at other locationsand times (King et aI. 1978, Ohlendorf et al. 1979,Blus et al. 1980, Mitchell et aI. 1981, Laporte 1982,Elliott et aI. 1989, Custer et aI. 1997), one of theten eggs had an elevated concentration of p,p'-DDE(13 flg/g) that could have caused reproductive im­pairment. P,p'-DDE concentration> 10 flg/g in eggswere correlated with decreased reproductive suc­cess in other heron species (Custer et aI. 1983,Henny et al. 1984, White et al. 1988).

Eggshell thickness was comparable to that re­ported at other locations in recent times (Custer etal. 1997) and does not seem threatening to GBHsnesting success on the UMR. Eggshells from INDUaveraged 3.4% thinner than eggshells collectedprior to 1947, but not nearly as much as the 15 to20% thinning associated with population changes(Anderson and Hickey 1972).

Mercury concentrations in our study (mean =0.15 flg/g wet weight, maximum = 0.76 flg/g; con­verted from dry weight using 83.7% moisture) weresimilar to or lower than those reported in GBHs atother locations (Custer et aI. 1997) and probably donot constitute a threat to GBHs. The concentrationof mercury associated with reproductive failurevaries by species (Ohlendorf et al. 1978) and a crit­ical mercury level in eggs has not been determinedfor any heron species. However, mean mercuryconcentrations in our study were generally belowthe concentrations reported to affect reproductionof ring-necked pheasants (Phasianus coIchicus;0.5 flg/g wet weight; Fimreite 1971), mallards

Contaminants in Great Blue Heron Eggs 9

(Anas ptatyrhynchos; 0.85 f.lg/g; Heinz 1979),common terns (Sterna hirundo; 1.0 f.lg/g; Connorset at. 1975), or herring gulls (Larus argentatus;> 16 f.lg/g; Vermeer et at. 1973).

Selenium concentrations in eggs in this study(mean 4.0 f.lg/g dry weight) were above the upperboundary of "normal" selenium concentrations inwaterbird eggs (3.0 f.lg/g dry weight) (Skorupa andOhlendorf 1991). However, selenium concentra­tions (mean = 0.65 f.lg/g wet weight, maximum =0.84 f.lg/g wet weight; converted from dry weightusing 83.7% moisture) were below the 3.0 f.lg/g wetweight threshold for causing reproductive impair­ment (Heinz 1996).

The timing of nesting was very similar to that re­ported at the same colony in 1981 (Taylor et at.1982). The first evidence of incubation (3 April),date of first hatching (3 May), and first fledging(2 July) recorded in 1981 were all within the peri­ods observed in 1993.

Nest initiation in this study (median first egg laid= 10 April) was also comparable to that on theUMR in 1995 (median = 5 to 9 April) and in un­flooded portions of the UMR in 1993 (median = 13April, Custer et at. 1997). Nest initiation seemeddelayed in flooded reaches of the UMR in 1993(median =29 April).

Mean clutch size at this colony in 1993 (4.2 eggsper clutch) was somewhat lower than reported in1981 (5.0 eggs per clutch, Taylor et al. 1982) butcomparable to clutch sizes of GBHs from elsewherein the North America (varied from 3.2 to 5.0 eggsper clutch; Custer et at. 1997). In contrast, abnor­mally small clutches (mean = 2.2-2.9 eggs perclutch) were observed in flooded portions of theUMR in 1993 (Custer et at. 1997).

Our results suggest that the GBH colony at INDUis not threatened by organochlorines, mercury, orselenium. With minor exception, concentrations ofthese environmental contaminants in GBH eggswere at background levels. Relatively low levels ofEROD activity, the low frequency of brain asym­metry, and the information on nest initiation, andclutch size support this contention. On the otherhand, few data on contaminant exposure of otheravian species are available in this area and the po­tential exists for elevated levels of PCBs or othercontaminants to cause localized problems.

The exposure of GBHs at the Indiana Dunes Na­tional Lakeshore colony to petroleum contamina­tion, a major contaminant in areas surrounding theheron colony (Hoke et at. 1993), requires furtherevaluation. We did not attempt to measure poly-

cyclic aromatic hydrocarbons (PAHs) in the eggcontents, because PAHs quickly metabolize in eggsduring incubation (Naf et at. 1992) and thereforeare unlikely to be detected. Because induction canbe correlated with PAH exposure (Lee et at. 1986),the lack of significant induction in livers of our em­bryos suggests that PAH exposure may not be ofconcern. Concentrations of PAHs in fresh eggs orchicks from this colony and a reference locationwould be useful in evaluating PAH exposure at thislocation.

ACKNOWLEDGMENTS

We thank Indiana Dunes National Lakeshore foraccess to their properties, Jason Butcher for prepar­ing the figures, Randy Knutson, Ralph Grundel, andAl Parker for technical and field assistance, andChristine Custer, J. Christian Franson, John P.Giesy, Fred Meyer, and one anonymous reviewerfor comments on the manuscript. This project wasfunded by the U.S. Fish and Wildlife Service, Divi­sion of Environmental Contaminants.

REFERENCESAnderson, D. W., and Hickey, J. 1. 1972. Eggshell

changes in certain North American birds. Proe. Inter.Ornitho!. Congr. 15:514-540.

Bellward, G. D., Norstrom, R., Whitehead, P. E., Elliot,J. E., Bandiera, S. M., Dworschak, C., Chang, T.,Forbes, S., Cadario, B., Hart, L. E., and Cheng, K. M.1990. Comparison of polychlorinated dibenzodioxinlevels with hepatic mixed-function oxidase inductionin great blue herons. 1. Toxieol. Environ. Health30:33-52.

BIus, L. J., Henny, C. J., and Kaiser, T. E. 1980. Pollu­tion ecology of breeding great blue herons in theColumbia Basin, Oregon and Washington. Murrelet61:63-71.

Brock, K. J. 1986. Birds of the Indiana Dunes. Bloom­ington Indiana: Indiana Univ. Press.

Connors, P. G., Anderlini, V. C., Risebrough, R. W.,Gilbertson, M., and Hays, H. 1975. Investigations ofheavy metals in common tern populations. Can.Field-Nat. 89: 157-162.

Custer, T. W., and Custer, C. M. 1995. Transfer andaccumulation of organochlorines from black-crownednight-heron eggs to chicks. Environ. Toxieo!. Chern.14:533-536.

__, Hensler, G. L., and Kaiser, T. E. 1983. Clutchsize, reproductive success, and organochlorine conta­minants in Atlantic coast black-crowned night-herons.Auk 100:699-710.

__, Hines, R. K., and Custer, C. M. 1996. Nest initia­tion and clutch size of great blue herons on the Mis-

10 Custer et al.

sissippi River in relation to the 1993 flood. Condor98:181-188.

__, Hines, R. H., Melancon, M. J., Hoffman, D. J ..Bickham, J. W., Martin, J. W. and Henshel, D. 1997.Contaminant concentrations and biomarker responsein great blue heron eggs from 10 colonies on theupper Mississippi River, USA. Environ. Toxicol.Chem. 16: 260-271.

Elliott, J. E., Butler, R. W., Norstrom, R., and White­head, P. E. 1989. Environmental contaminants andreproductive success of great blue herons Ardea hero­dias in British Columbia, 1986-87. Environ. Pollut.59:91-114.

Fimreite, N. 1971. Effects of dietary methylmercury onring-necked pheasants. Can. Wildl. Ser., Occ. Papers9.

Fitzner, R. F., Blus, L. J., Henny, C. J., and Carlile, D.W. 1988. Organochlorine residues in great blueherons from the northwestern United States. Colon.Waterbirds 11 :293-300.

Fleming, W. J., Pullin, B. P., and Swineford, D. M.1984. Population trends and environmental contami­nants in herons in the Tennessee Valley, 1980-81.Colon. Waterbirds 7:63-73.

Hart, L. E., Cheng, K. M., Whitehead, P. E., Shah, R.M., Lewis, R. J., Ruschkowski, S. R., Blair, R. W.,Bennett, D. C., Bandiera, S. M., Norstrom, R., andBellward, G. D. 1991. Dioxin contamination andgrowth and development in great blue heron embryos.J. Toxicol. Environ. Health 32:331-344.

Heinz, G. H. 1979. Methylmercury: Reproductive andbehavioral effects on three generations of mallardducks. J. Wildl. Manage. 43:394-401.

___. 1996. Selenium in birds. In Environmental Cont­aminants in Wildlife, Interpreting Tissue Concentra­tions, eds. W.N. Beyer, G.H. Heinz, and A. W. Red­mon-Norwood, pp. 447-458. Boca Raton, FL: LewisPublishers.

Henny, C. J., and Bethers, M. R. 1971. Population ecol­ogy of the great blue heron with special reference towestern Oregon. Can. Field-Nat. 85:205-209.

__, Blus, L. J., Krynitsky, A. J., and Bunck, C. M.1984. Current impact of DDE on black-crownednight-herons in the Intermountain West. 1. Wildl.Manage. 48:1-13.

Henshel, D. S., Cheng, K. M., Norstrom, R., Whitehead,P., and Steeves, J. D. 1993. Morphometric and histo­logical changes in brains of great blue heron hatch­lings exposed to PCDDs: Preliminary analysis. InASTM STP#1179: First Symposium on EnvironmentalToxicology and Risk Assessment: Aquatic, Plant, Ter­restrial, eds. W. Landis, J. S. Hughes and M. A.Lewis, pp. 262-277. American Society for Testingand Materials.

___, Martin, J. W., Norstrom, R., Whitehead, P.,Steeves, J. D., and Cheng, K. M. 1995. Morphometricabnormalities in brains of great blue heron hatchlings

exposed in the wild to PCDDs. Environ. Health Per­speet. 103:61-66.

Hines, R. K., and Custer, T. W. 1995. Evaluation of anextendable pole-net to collect heron eggs in thecanopy of tall trees. Colon. Waterbirds 18:120-122.

Hoffman, D.J., Smith, G. J., and Rattner, B. A. 1993.Biomarkers of contaminant exposure in commonterns and black-crowned night herons in the GreatLakes. Environ. Toxicol. Chem. 12: 1095-1103.

Hoke, R. A., Giesy, J. P., Zabik, M., and Unger M. 1993.Toxicity of sediments and sediment pore waters fromthe Grand Calumet River-Indiana Harbor, IndianaArea of Concern. Ecotoxicol. Environ. Safety26:86-112.

Indiana Department of Environmental Management.1988. Northwest Indiana Environmental Action Plan.Draft Area of Concern Remedial Action Plan. IndianaDepartment of Environmental Management, Indi­anapolis, IN.

Indiana State Department of Health. 1997. 1997 IndianaFish Consumption Advisory. Indianapolis, Indiana.

International Joint Commission. 1985. Report of GreatLakes Water Quality. International Joint Commission,Great Lakes Water Quality Board, Kingston, Ontario,Canada.

Kennedy, S. W., Lorenzen, A., and Norstrom, R. 1996.Chicken embryo hepatocyte bioassay for measuringcytochrome P4501A-based 2,3,7,8-tetrachloro­dibenzo-p-dioxin equivalent concentrations in envi­ronmental samples. Environ. Sci. Technol.30:706-715.

King, K. A., Flickinger, E. L., and Hildebrand, H. H.1978. Shell thinning and pesticide residues in Texasaquatic bird eggs, 1970. Pest. Monit. Journal12: 16-21.

Laporte, P. 1982. Organochlorine residues and eggshellmeasurements of great blue heron eggs from Quebec.Colon. Waterbirds 5:95-103.

Lee, Y. Z., O'Brien, P. J., Payne, J. F., and Rahimtula,A. D. 1986. Toxicity of petroleum crude oils and theireffects on xenobiotic metabolizing enzyme activitiesin the chicken embryo in Ovo. Environ. Res.39:153-163.

Melancon, M. J. 1996. Development of CytochromesP450 in Avian Species as a Biomarker for Environ­mental Contaminant Exposure and Effect: Proce­dures and Baseline Values. In ASTM STP#1306: Envi­ronmental Toxicology and Risk Assessment:Biomarkers and Risk Assessment, eds. D. A.Bengston, and D. S. Henshel, pp. 95-108. AmericanSociety for Testing and Materials.

Mitchell, C. A., White, D. H., and Kaiser, T. E. 1981.Reproductive success of great blue herons at NuecesBay, Corpus Christi, Texas. Bull. Texas Ornithol. Soc.14:18-21.

Naf, C., Broman, D., and Brunstrom, B. 1992. Distribu­tion and metabolism of aromatic hydrocarbons

Contaminants in Great Blue Heron Eggs 11

(PAHs) injected into eggs of chicken (Gallus domesti­cus) and common eider duck (Somateria mollissima).Environ. Toxico!. Chem. II: 1653-1660.

Ohlendorf, H. M., Risebrough, R. W., and Vermeer, K.1978. Exposure of marine birds to environmentalpollutants. U. S. Fish Wild\. Ser., Wild\. Res. Rep.No.9.

__, Klaas, E. E., and Kaiser, T. E. 1979. Environ­mental pollutants and eggshell thickness: Anhingasand wading birds in the eastern United States. U. S.Fish and Wild\. Ser., Spec. Sci. Rep.-Wild\. No. 216.

PAHLS, Inc. 1993. The Environment of' Northwest Indi­ana. 102 N. Morgan Blvd., Valparaiso, IN 46383.

Pratt, H. M. 1970. Breeding biology of great blue heronsand common egrets in central California. Condor72:407-416.

Rattner, B. A., Hatfield, J. S., Melancon, M. J., Custer,T. W., and Tillit, D. E. 1994. Relation amongcytochrome P450, AH-active PCB congeners anddioxin equivalents in pipping black-crowned night­heron embryos. Environ. Toxico!. Chem.13: 1805-1812.

Safe, S. 1990. Polychlorinated biphenyls (PCBs),dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs),and related compounds: Environmental and mechanis­tic considerations which support the development oftoxic equivalency factors (TEFs). Crit. Rev. Toxico!.21:51-88.

Skorupa, J. P., and Ohlendorf, H. M. 1991. Contami­nants in drainage water and avian risk thresholds. InThe Economics and Management of Water and

Drainage in Agriculture, eds. A. Dinar and D. Zilber­man, pp. 345-368. Boston, MA: Kluwer Academic.

Steffeck, D. W. 1989. A survey for contaminants in biotanear the Midco I, Midco fl, and Ninth Avenue dumphazardous waste sites in Gary, Lake County, Indiana.U.S. Fish and Wildlife Service, Bloomington, IN.

Struger, 1., and Weseloh, D. V. 1985. Great LakesCaspian terns: egg contaminants and biological impli­cations. Colon. Waterbirds 8:142-149.

Taylor, T. M., Reshkin, M., and Brock, K. 1. 1982.Recreational land use adjacent to an active heronrookery: A management study. Ind. Acad. Sci. 91:226-236.

Tillitt, D. E., Ankley, G. T., Giesy, J. P., Ludwig, J. P.,Kurita-Matsuba, H., Weseloh, D. V., Ross, P. S.,Bishop, C. A., Sileo, L., Stromborg, K. L., Larson, J.,and Kubiak, T. J. 1992. Polychlorinated biphenylresidues and egg mortality in double-crested cor­morants from the Great Lakes. 1992. Environ. Toxi­col. Chem. 11:1281-1288.

Vermeer, K., Armstrong, F. J., and Hatch, D. M. 1973.Mercury in aquatic birds at Clay Lake, WesternOntario. J. Wild!. Manage. 37:58-61.

White, D. H., Fleming, W. J., and Ensor, K. L. 1988.Pesticide contamination and hatching success ofwaterbirds in Mississippi. 1. Wildl. Manage. 52:724-729.

Submitted: 21 June 1997Accepted: 26 October 1997Editorial handling: Peter F. Landrum