Accumulation of organochlorine contaminants in double-crested cormorants

Avian eggshell thickness in relation to egg morphometrics, embryonic development, and mercury contamination

Eggshell thickness is important for physiological, ecological, and ecotoxicological studies on birds; however, empirical eggshell thickness measurements for many species and regions are limited. We measured eggshell thickness at the equator and the egg poles for 12 avian species and related eggshell thickness to egg morphometrics, embryonic development, egg status, and mercury contamination. Within an egg, eggshells were approximately 5.1% thicker at the equator than the sharp pole of the egg, although this difference varied among species (0.6%-9.8%). Within Forster's tern (Sterna forsteri), where eggshell thickness was measured at 5 equally spaced positions along the longitude of the egg, eggshell thickness changed more rapidly near the sharp pole of the egg compared to near the blunt pole of the egg. Within species, eggshell thickness was related to egg width and egg volume for six of the 12 species but was not related to egg length for any species. Among species, mean eggshell thickness was strongly related to species mean egg width, egg length, egg volume, and bird body mass, although species mean body mass was the strongest predictor of species mean eggshell thickness. Using three species (American avocet [Recurvirostra americana], black-necked stilt [Himantopus mexicanus], and Forster's tern), whose nests were carefully monitored, eggshell thickness (including the eggshell membrane) did not differ among viable, naturally abandoned, dead, or failed-to-hatch eggs; was not related to total mercury concentrations of the egg content; and did not decrease with embryonic age. Our study also provides a review of all existing eggshell thickness data for these 12 species.

Connecting breeding and wintering habitats of migratory piscivorous birds: implications for tracking contaminants (Hg) using multiple stable isotopes

Contaminant concentrations in migratory species are complicated by differential accumulation and elimination among geographically separated biomes. Double-crested cormorants ( Phalacrocorax auritus ) are used as monitors of Hg in North America; however, migration from northern breeding colonies to southern marine, freshwater, and aquaculture systems exposes individuals to spatiotemporal variations in contaminant uptake. We used stable isotopes (δ(34)S, δ(13)C, δ(15)N, δ(2)H) in primary feathers and a combined Bayesian assignment and isotopic threshold model to identify feather origins and the potential winter use of aquaculture (δ(34)S < 10‰, δ(13)C > -14‰), freshwater (δ(34)S < 10‰, δ(13)C < -20‰), and marine habitats (δ(34)S > 10‰). This approach allowed us to contrast body burden Hg derived from the breeding and wintering grounds, as well as from marine and freshwater habitats. We found feathers grown on Lake Winnipeg had greater Hg concentrations (mean = 4.26 ± 1.47 μg/g fresh weight; n = 20) than winter-grown feathers (3.19 ± 1.64 μg/g; n = 19), but Hg in winter-grown feathers was not related to any specific habitat. Isotopic assays of tissues of migratory birds allowed the source and degree of contaminant exposure to be identified throughout the annual cycle.

The incidence of polychlorinated biphenyl and organochlorine pesticide residues in the eggs of the cormorant (Phalacrocorax carbo sinensis): an evaluation of the situation in four Greek wetlands of international importance

This study contributed to identifying the current levels of organochlorine pollutants in four Greek wetlands of international importance (the Evros and Axios Deltas, and Kerkini and Prespa Lakes), using the cormorant Phalacrocorax carbo sinensis as a suitable bioindicator in a region where such information is scarce. Residue levels of eight polychlorinated biphenyl (PCB) congeners and 13 organochlorine pesticide (OC) compounds were measured in cormorant eggs. Most PCBs and OCs (except dieldrin and endrin) were found in at least some of the study areas. Median concentrations of five PCBs (IUPAC 8, 20, 52, 138, 180) and of six OCs (alpha-BHC, beta-BHC, lindane, heptachlor, 4,4'-DDE and 4,4'-DDT) differed significantly among the areas. The median totals of the PCBs were highly significant among the areas, being unexpectedly highest in Prespa Lake (68.43 ppb), despite its remoteness, and lowest in Evros Delta samples (12.17 ppb). Aldrin that was found in samples from Evros, Axios and Prespa probably accumulated in wintering grounds. In all of the areas, the relative proportions of alpha-BHC and 2,4'-DDD were the highest of all OCs. Fingerprint and cluster analyses illustrated overall differences in the PCB patterns, being greatest between the deltas than between the lakes, but, inversely, for OCs the differences were smaller in the deltas. Differences were attributed to large variations in the cormorants' diet between areas and different regimes of pollutant management in the two types of wetland. Correlations of pollutants varied considerably among areas and they were more diverse in OCs. The sum of OCs/ sum of PCBs ratio indicates agrochemical pollution in all areas. An important finding was that levels of both pollutant groups were too low to have any biological implications on the cormorants and, additionally, suggest that they have a negligible impact on the environment of the wetlands studied.

Organochlorine contamination in bird's eggs from the Danube Delta

In this study we report the levels of organochlorine compounds in eggs of aquatic birds from the Danube Delta, a major European wetland. The eggs were collected in 1997 and belonged to the following species: the mallard (Anas platyrhynchos), the greylag goose (Anser anser), the mute swan (Cygnus olor), the coot (Fulica atra), the glossy ibis (Plegadis falcinellus), the spoonbill (Platalea leucorodia), the little egret (Egretta garzetta), the night heron (Nycticorax nycticorax), the grey heron (Ardea cinerea), the great white egret (Egretta alba), the red-necked grebe (Podiceps griseus), the Dalmatian pelican (Pelecanus crispus), the Pygmy cormorant (Phalacrocorax pygmaeus) and the common cormorant (Phalacrocorax carbo). Dichlorodiphenyltrichloroethane (DDT) levels were higher in eggs of the little egret, the great white egret, the cormorant and the Pygmy cormorant with respect to the other species (48,399, 13,613, 12,400 and 10,417 ng/g dry wt., respectively). Hexachlorobenzene (HCB) levels were lower than 1393 ng/g dry wt. in all species while polychlorinated biphenyl (PCB) concentrations in the Pygmy cormorant (2565 ng/g dry wt.) were higher than in the other species. The toxicity evaluation was based on 2,3,7,8-TCDD toxic equivalent factors (TEF) and non-ortho PCB congeners contributed much more than mono-ortho PCBs in most of species. A further aim of this study was to evaluate the possible differences of organochlorine levels in bird eggs collected in the same area in 1982 and in 1997; generally speaking the levels detected in the latter period were lower than those detected in the earlier one.

Organochlorine pesticides in wolves from Galicia

Levels of seven organochlorine pesticides (heptachlorepoxide, dieldrin, endrin, p,p'-DDE, o-p'-DDT, p,p'-DDT, and methoxychlor) and DDE/DDT ratios were determined in spleen, liver, muscle, kidney and suprarenal from 12 wolves from three provinces of Galicia (eight male and four female). Analysis was carried out by GC-ECD. Heptachlorepoxide was in found only 25% of samples, while p,p'-DDE was the most dominant of the organochlorine compounds analyzed. DDE/DDT ratios higher than 1 were found in liver and muscle.

Persistent organochlorine residues in fish and water birds from the Biobio river, Chile

Concentrations of polychlorinated biphenyls (PCBs), DDT and its metabolites, HCH isomers and hexachlorobenzene (HCB) were determined in fish and birds from different locations in the Biobio river basin (central Chile). Samples collected near the mouth of the river contained high concentrations of PCBs, reflecting the massive use of these xenobiotics in the urban and industrial areas of Concepcion and Talcauano. Samples collected in the central part of the basin contained very high concentrations of lindane that coincide with the widespread use of lindane-based pesticides (purified γ-HCH) in this area. DDT was distributed homogeneously throughout the basin, except at Laguna Icalma, the source of the river in the Andes. Most PCB residues in fish and birds consisted of congeners between penta- and hepta-chlorobiphenyls. In fish, the predominant congeners were the pentachlorobiphenyl 23'44'5 (IUPAC number 118) and the hexachlorobiphenyl 22'344'55' (PCB-153); in birds 22'44'55' (PCB-180) prevailed.

Reduced breeding success of Cormorants (Phalacrocorax carbo sinensis) in relation to persistent organochlorine pollution of aquatic habitats in The Netherlands

Cormorants (Phalacrocorax carbo sinensis) breeding in the heavily contaminated sedimentation area of the rivers Rhine and Meuse have a severely reduced breeding success as compared to several other Dutch colonies. A detailed analysis of reproductive performance in combination with chemical analysis of eggs and food from colonies in differently contaminated aquatic habitats is presented. The differences in breeding success between colonies are caused mainly in the egg-stage of breeding. Eggshell thinning and increased embryonic mortality cause the differences in hatching success. The observed effects seem to be related to chlorinated hydrocarbons. Significant correlations are found for concentrations of DDE with eggshell thinning and for concentrations of PCBs with hatching and breeding success. The correlations between concentrations of chlorinated hydrocarbons in eggs and biological effects measured in the field are established both on colony and individual clutch level.