Virginie Debacker

Tuna and Dolphin associations in the North-east Atlantic : Evidence of different ecological niches from stable isotope and heavy metal measurements

Associations of tunas and dolphins in the wild are quite frequent events and the question arises how predators requiring similar diet in the same habitat share their environmental resources. As isotopic composition of an animal is related to that of its preys, stable isotope ( 13 C/ 12 Ca nd 15 N/ 14 N) analyses were performed in three predator species from the North-east Atlantic: the striped dolphin, Stenella coeruleoalba, the common dolphin Delphinus delphis and the albacore tuna, Thunnus alalunga, and compared to their previously described stomach content. Heavy metals (Cd, Zn, Cu and Fe) are mainly transferred through the diet and so, have been determined in the tissues of the animals. Tuna muscles display higher d 15 N than in common and striped dolphins (mean: 11.4 vs. 10.3‰ and 10.4‰, respectively) which reflects their higher trophic level nutrition. Higher d 13 C are found in common ()18.4‰) and striped dolphin ()18.1‰) muscles than in albacore tuna ()19.3‰) probably in relation with its migratory pattern. The most striking feature is the presence of two levels of cadmium concentrations in the livers of the tunas (32 mg kg ˇ1 dry weight (DW) vs. 5 mg kg ˇ1 DW). These two groups also diAer by their iron concentrations and their d 15 N and d 13 C liver values. These results suggest that in the Biscay Bay, tunas occupy two diAerent ecological niches probably based on diAerent squid inputs in their diet. ” 2000 Elsevier Science Ltd. All rights reserved.

Heavy Metals, Organochlorines and Polycyclic Aromatic Hydrocarbons in Sperm Whales Stranded in the Southern North Sea During the 1994/1995 Winter

Seven male sperm whales stranded on the southern North Sea coast during the 1994/95 winter were analysed for stable pollutant concentrations in muscle, liver, kidney and blubber: heavy metals (total and organic Hg, Se, Zn, Pb, Ni, Cd, Fe, Cr, Cu and Ti), organochlorines (PCBs and pesticides) and polycyclic aromatic hydrocarbons (PAHs). High concentrations of Cd (up to 300 μg/g dw in kidney), Hg (up to 130 μg/g dw in liver) and PCBs (up to 5 μg/g dw in blubber) were detected, but not considered as the direct cause of mortality, while their possible indirect influence on the health status and/or behaviour of the North Atlantic sperm whale population is discussed.

Influence of Age, Sex and Body Condition on Zinc, Copper, Cadmium and Metallothioneins in Common Guillemots (Uria aalge) Stranded at the Belgian Coast.

The common guillemots, Uria aalge, found stranded at the Belgian coast, display high levels of Cu in both liver and kidneys. The condition index of the animals, defined as the ratio of liver to kidneys mass (Wenzel & Adelung, 1996, The suitability of oiled Guillemots (Uria aalge) as monitoring organisms for geographical comparisons of trace element contaminants. Archives of Environmental Contamination and Toxicology, 31, 368-377), influences both the metal concentration and its binding to metallothioneins (MT): the lower the condition index, the more emaciated the animals, and the higher the total Cu concentration and the concentration of Cu bound to MT. In less robust individuals, our results suggest that Cu could displace Zn from MT, rendering the Zn ions available to induce a new MT synthesis. Sex-related effects also emerged as significantly higher hepatic MT as well as Cu- and Zn-MT concentrations were found in emaciated male guillemots compared to females. In both organs, Cd concentrations remained low and typically demonstrated an age-dependent renal accumulation, with no noticeable effect of the condition index. As a whole, these results suggest that, for guillemots found stranded at the Belgian coast. Cu binding to hepatic and renal MT could function as a protective mechanism, rendering the metal ions unavailable to exert any cytotoxic activity.

Combined effects of experimental heavy-metal contamination (Cu, Zn, and CH3Hg) and starvation on quail's body condition: parallelism with a wild common guillemot (Uria aalge) population found stranded at the Belgian coast.

Combined effects of heavy-metal contamination (Cu, Zn, and CH3Hg) and starvation were tested on common quails (Coturnix coturnix japonica) and used as a model for comparison with a wild common guillemot (Uria aalge) population found stranded at the Belgian coast. Appropriate heavy-metal levels were given to the quails to obtain concentrations similar to those found in the seabirds’s tissues. The contaminated animals were then starved for 4 d to simulate the evident malnutrition symptoms observed at the guillemot’s level. In such conditions, food intake and total-body weight are shown to decrease in contaminated individuals with simultaneous significant hepatic and renal increase of the heavy-metal concentrations. Like guillemots, higher heavy-metal levels were observed in those contaminated quails that had also developed a cachectic status characterized by a general atrophy of their pectoral muscle and complete absence of subcutaneous and/or abdominal fat depots. Although likely the result of a general protein catabolism during starvation, it is suggested that these higher metal levels could as well enhance a general muscle wasting process (cachectic status).

Role of metallothioneins in metal regulation by the guillemot Uria aalge

Guillemots, like other seabird species living in the North Sea, appear to be heavily contaminated by copper. Metallothioneins are present in both liver and kidney but, at least in the specimens stranded along the Belgian coast, fail to maintain constant the copper, zinc and cadmium load of the high molecular weight soluble proteins of both organs, stressing the potential toxic role of these metals, mainly copper.