selenium concentrations were higher in Orkney samples than Faroese, and the concentrations of cobalt and copper, were lower in Orkney birds than Faroese.
Practical Project Report 2006/2007 School of Biological Sciences
Intraspecific and geographical variation in heavy metal profiles in the Northern Fulmar Fulmarus glacialis
Sjurdur Hammer
Supervisors: Prof. Paul Thompson Prof. Andrew A. Meharg
Work completed in partial fulfilment of the requirements for a degree in Honours Biology
Abstract
82 samples of kidney and bone tissue were taken from culled northern fulmar Fulmarus glacialis in the Faroe Islands. Additionally 24 blood samples from the Faroes were compared with 15 blood samples taken on Eynhallow, Orkney. The samples were analysed for their content of arsenic, cadmium, cobalt, copper, lead, selenium and zinc. The aim of the study was to find any variation between, age, sex or location. Significantly higher levels of arsenic, cadmium, and selenium were found in adult bone and kidney samples, and zinc was also higher in kidney samples. Males had significantly higher concentrations of arsenic in their kidney tissue than females, and lower concentrations of selenium than females. The blood samples had higher concentrations of arsenic in males than females. Arsenic and selenium concentrations were higher in Orkney samples than Faroese, and the concentrations of cobalt and copper, were lower in Orkney birds than Faroese. Several element correlations were found, and correlations between cadmium, and also selenium bone and kidney levels. The concentration of cadmium in the kidney found in this study are within the range of what has been found to be potentially damaging in other studies. Although the specimens sampled in this study were apparently healthy when caught, the possibility remains that these birds experience a sub lethal effect caused by a heavy load of cadmium and arsenic. This has further consequences, with the realisation that this load may be sex-biased, but this would require a better understanding of fulmar diet on a temporal scale.
I hereby declare that this thesis is my own work. Where I have used the work of other persons or quoted the work of other persons the sources of the other work or information have been detailed explicitly in the presentation
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Contents:
Page no:
1. Introduction…………………………………………………………………………………..4 2. Methods and materials 2.1. Field work……………………………………………………………………………….9 2.2. Dissection……………………………………………………………………………....10 2.3. Laboratory work………………………………………………………………………..12 2.3.1. Quality control…………………………………………………………………..13 2.4. Statistical analysis………………………………………………………………………15 3. Results 3.1. Quality control………………………………………………………………………….16 3.2. General Linear Model…………………………………………………………………..21 3.3. Spearman’s Rank Correlation…………………………………………………………..22 3.4. Principal Component Analysis…………………………………………………………24 4. Discussion 4.1. Methodology and data validation………………………………………………………28 4.2. Age specific difference………………………………………………………………....29 4.3. Inter population difference……………………………………………………………..33 4.4. Inter Sexual difference…………………………………………………………………33
Acknowledgements References Appendix I-V Risk assessment
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1. Introduction Marine birds have been used as proxies for estimating fishing populations, and the use of animals as indicators of level of pollution in the environment has long been a supplement to chemical and environmental monitoring, because of its ecological relevance, and the ability to locate long-time exposure of a compound which might be undetectable otherwise. In the marine environment mammals occupy relatively high trophic layers and this is also true for most marine birds. Some of the highest accumulations of toxic metals mercury (Hg) and cadmium (Cd) have been found in marine birds (Osborn, 1979). The pelagic bird northern fulmar Fulmarus glacialis is examined in this study. It is from the order Procellariiforms in the family Procellariidae. The fulmars from an Orkney-based study, showed to have a mean life expectancy 33.9 years for males and 35.5 years for females, which makes them suitable models for investigating chronic low-level exposure (Dunnet & Ollason, 1978).
Both sexes of fulmar have similar plumage, but they are dimorphic in size (Prince & Morgan, 1987). Such is the difference that bill and head size has become a widely used statistical predictor of fulmars’ and many other seabirds’ sex (van Frakener & ter Braak, 1993; Cramp & Simmons, 1983). Sexual dimorphism has been found to affect where northern giant petrels Macronectes halli feed and their diet (González-Solís et al., 2002). Unlike other kinds of sexual dimorphism, the dimorphism seen in northern giant petrels was found to be more due to ecological causation than sexual selection and possibly this is true for the fulmar as well (González-Solís, 2004; Owens & Hartley, 1998). To which degree sexual dimorphism impacts feeding and foraging behaviour in fulmar is unclear, but it appears to have a clear impact on their survival rate (Dunnet & Ollason, 1978). By using and comparing accumulations of different compounds, we can
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estimate if the cause of the uneven survival rate is related to accumulation of polluting elements through the diet.
Several studies have been made on the diet of northern fulmar (Furness & Todd, 1984; Cherel et al. 2001; Barret et al. 2002; Garthe et al. 2004). Because the fulmar is a generalist feeder, studies have shown a great geographic and temporal variability reflecting the availability of prey. This is thought to be one of the secrets to its successful expansion throughout the North Atlantic and North sea (Fisher, 1952). The increase of discards generated from industrial whaling and later fisheries was correlated to the expansion of fulmar populations Fisher (1952) concluded, and recent studies suggest that fish offal is still an important part of fulmar diet in some locations particularly during breading season (Philips et al. 1999). In some populations fish, often sandeels, constitute the main food source, and in others it might be crustaceans or squid. There are currently no detailed data on the fulmar diet in the Faroe Islands, but a study is underway. It is not vital for this study, but the lesson is that there is great variation of diet in space and time, so predictions about a sexual difference due to diet, should not be extrapolating further than a given time and place.
Many, both experimental and field studies have been made on the distribution of the toxic elements in different tissues of pelagic seabirds (Osborn et al. 1979; Osborn, 1979; Borga et al. 2006; Furness et al. 1994; Kim et al. 1998; Kim et al. 1996; Nicholson et al. 1983; Nicholson & Osborn, 1983; Dam et al. 2004; Harris & Osborn, 1981; Osborn et al. 1984; Bull et al. 1977). In toxicological research, Arsenic (As), Cd, Hg, and lead (Pb) are often the main elements of interest, as these are usually related to anthropogenic pollution. But elemental and isotope ratios in marine birds have the potential to provide other information about their ecology. Using stable 5
isotopes δ13C and δ15N ratios, Cherel et al. discovered a difference in the wintering areas of 4 sub-Antarctic petrel taxon (2006). δ13C gives an indication of latitudinal gradient or an inland/oceanic gradient (Cherel et al., 2000) and δ15N is an indicator of which trophic level of the consumer occupies (Hobson & Welch, 1992). Expanding this further, δ13C and δ15N can provide a method of examining diet shifts and resource acquisition, (Phillips & Eldridge, 2006; Cherel et al. 2005) trophic segregation by sex and age, (Forero et al. 2005) and moulting and breeding origins of seabirds (Cherel et al. 2000).
In migratory birds or long-range foraging birds such as fulmars (Burg et al. 2003), it is possible to determine geographic variation from Pb isotopes
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Pb,
206
Pb,
207
Pb,
208
Pb. Atmospheric Pb
partly originates from the local geological features, but the dominant signature results from combustion of leaded fuels (Bollhöfer & Rosman, 2001). This has made geographic ‘fingerprinting’ possible as Pb, although it is non-essential, is biologically active and organisms will therefore reflect the isotopic composition of any local pollution (Emsley, 2001; Meharg et al. 2002; Scheuhammer & Templeton, 1998).
In a similar way as with stable isotopes, González-Solís et al. have used different metal concentrations and selenium (Se) to determine geographic and trophic segregation in a pelagic seabird (2002). Although many physiological features will play a role in which metals and elements accumulate in which tissues, and there is temporal variation, we aim in this study to establish the concentrations of various elements, and to discuss which ecological reasons might be the cause of the intraspecific variation.
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In this study, different tissues from 82 fulmars from the Faroe Islands were analysed for concentrations of 4 essential elements, cobalt (Co), copper (Cu), Se and zinc (Zn), and 3 nonessential elements: As, Cd and Pb. Some of the element concentrations will assumingly show intraspecific variation between age and sex, and also some predictable correlations between the different elements e.g. between Zn – Cd, and between tissues. This can be compared to other similar studies (Osborn et.al. 1979, Kim et.al. 1998, Borga et.al. 2006). Of the 82, blood samples were only taken of 24 individuals. This was used for comparison of 15 blood samples from Orkney. Comparison studies regarding diet have been done between fulmar populations, but a metal-level comparison study has to our knowledge not been done on fulmar populations before.
What makes this study unique is that sampling has been undertaken on culled Faroese birds, which in contrast is not always an option where there is no tradition of fowling marine birds. The alternative to culling the bird, is blood and feather samples which are commonly used in these kinds of studies. Feather samples have the advantage of giving a good temporal picture of element acquisition or pollutant exposure because of the predictable nature of feather moulting (Cherel, et.al. 2000). The disadvantage with using feather samples is that they have a high risk of external contamination, and do not give a precise correlation with food chain pollution (Furness & Camphuysen, 1997). In some studies, feathers of museum specimens have been analysed, as an indicator of historical exposure to pollution (Furness & Camphuysen, 1997). Museum specimens are especially prone to environmental contamination or from pesticide treatment, which highlights the need in similar studies to examine more than one type of tissue for comparison.
The significance of the atypical method of sampling, is that the data extracted from these samples can be said to be a good representation of the present state of fulmars, because the tissue samples 7
are all from apparently healthy birds rather than beached birds, or accidental casualties in fishery, which can have numerous confounding factors and biases. This is not to say that any confounding factors are eliminated in this study, the ecology of fulmar populations in the Faroes is not nearly well enough understood to make confident connections between toxicological and ecological factors.
Although there at present time exists at great amount of material on concentrations of different elements/contaminants in marine birds, few examine how the different elements are interconnected, and even fewer integrate biological variables such as sex, age and location. For this correlation calculation is used to examine the different element concentrations, and the multivariate principal component analysis is used to determine how the element concentrations relate to biological factors of age and sex. Although the fulmar is a fairly well studied marine bird, this study is unique in examining a relative large sample size for a relatively large number of different elements.
The aims of this study can be summarized in 3 main questions: 1. Is there a significant intraspecific difference in element levels in different tissues between sexes and age-groups?
2. Is there correlation between certain elements in kidney, bone and blood tissues?
3. Is there a significant difference in metal levels in blood of adult Faroese fulmar and adult Orkney fulmar?
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2. Methods and materials: 2.1 Field work: The tradition of fowling in the Faroes is mainly for juvenile fulmar. When the juveniles leave their nests (late August to early September) there is a period of a few days where they are too heavy for flight, so they swim around, and at this time they are very easy to catch.
The main part of the field work involved catching and dissecting a sample of fulmars (Fulmarus glacialis) in the Faroe Islands in June - Sept 2006. By joining forces with locals, primarily from the village of Eiði, much of the sampling was out-sourced in the
Figure 2.1 Map over the Faroe Islands, showing the sampling locations with red marks. Copyright Google Maps
sense that I was not an active participant in all cases. However, there is little risk of bias because the fowling practice is very uniform from person to person, and participants were instructed to be non-discriminatory in regard to size particularly. A total of 82 birds were caught, providing an equally weighted sex ratio. Samples were taken from 4 different sites in the northern region of the Faroes (fig. 2.1), some from land (62°30’N 7°11’W), but mostly from boat/ship (62°31’N, 5°39’W; 62°18’N, 7°07’W; 62°22’N 6°53’W). As mentioned in the introduction, some aspects of the fowling practice, also ensure that individuals are caught from different age-groups. The adult birds were caught from sea and on land using a ‘fleygingarstong’ which is a ten-foot long pole with a triangular net on the end. A great number of fulmars are attracted to boats and ships in the
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prospect of getting fish offal, so catching them is easy, and is a common practice. All the juvenile birds were caught on one excursion on August 31st, whereas the others were caught on 3 excursions between June 22nd and August 28th.
Blood samples were taken from a number of live birds on the field, but this was not possible for all the birds. Most of the Faroese blood samples were retrieved from dissection. 15 Figure 2.2 Map showing the Orkney islands, with Eynhallow marked Copyright Google Map
Blood samples were also taken between April and August 2006
by Prof. Paul Thompson on Eynhallow on Orkney (59°08’N; 3°07W) for comparison. The fulmar chicks hatch in June but do not mature and leave the nest until late August (Joensen, 1966), so since the fulmars taken in Orkney were taken in flight, the assumption was that they were adult (either breeding or non-breeding). The number of samples taken in the Faroes and Orkney is shown in Table 2.1 a,b,c.
2.2 Dissection: The procedures used for dissection were adopted from the Save the North Sea Fulmar-Litter EcoQO Manual (SNS) (van Franeker, 2004). The standard SNS dissection form (Appendix I) was customized to suit this project. Measurements such as head and wing length, bill depth were taken to 1 decimal point of a millimetre. The weight was also measured to 1 decimal point of a
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gram. A condition index was also calculated based on 0-3 scores of different 3 characters: breast muscle, subcutaneous fat, intestinal fat (Appendix II). A sexual maturity index was also derived. For male birds, this was length multiplied by width of the testis, and for the females a score was given for the oviduct multiplied with diameter of the largest follicle. The sexual maturity indices provided the basis for the age-groups displayed in table 2.1, juvenile (
