Welsh Journals

RESULTS AND DISCUSSION The analyses of foliage (Table 1) show that the calcium levels are low, although the magnesium levels appear to be satisfactory. These calcium levels would be in keeping with the underlying structure of the rock on the island. The higher calcium levels in the Red Fescue (F. rubra) samples from the Lantern may reflect the influence of Herring Gulls (Larus argentatus). These Gulls were nesting in the area and their droppings could have added considerably to the calcium level in soil. The lead levels in all samples are about the same as those found in samples collected at the same time of year in the Gower Peninsula. The levels of zinc and copper are about double those in the Gower samples. The calcium levels in the Gower samples were more than 4500 p.p.m. dry weight. The effect of different levels of calcium on the absorption by plants of other metals has been observed by Lounamaa (1956). The elevated levels of zinc and copper in the Skomer samples could reflect the naturally low levels of lead and calcium in the soil, rather than elevated levels of zinc and copper. TABLE 1 Mean values of samples p.p.m. dry weight Zn Cu Cd Pb Ca Mg Festuca rubra (Lantern) 122.3 21.4 1.5 11.7 1875 2771 Festuca rubra (Farm) 106 17.7 1.3 10.1 804 2394 Endymion non- scriptus 179.6 27.6 1.0 9.7 1101 3488 The results of animal analyses are shown in Table 2. This shows that the level of all the metals investigated is highest in the flat bones taken from the roof of the skull. If the level of metal intake is low, excretion from the body can be effected by the intestine and kidneys. If the level of intake is higher than the body requires and the excretory systems can manipulate, the surplus metal in the blood is removed and stored in the bones. By doing this the metal is effectively separated from the rest of the body tissues. Schroeder & Tipton (1968) found that 90 per cent. of the mean body burden of lead in human subjects was present in the skeleton. The higher levels of lead and other metals in flat bone, compared with long bone, reflects the greater density of the flat bones. The lead levels in these specimens from Skomer Island are higher than those found in similar animals from Gower. A possible explanation for this is that the level of calcium in the foliage is low. Calcium competes with other metals for absorption in the intestine, and the reduced levels of calcium may result in the greater absorption of other metals from the food. This situation could apply in the case of lead in both the species investigated.