Trace Elements in Clutches of Yellow-Legged Gulls, Larus cachinnans, from the Medes Islands, Spain

Temporal and Spatial Distribution of Mercury in Gulls Eggs from the Iberian Peninsula

“…Concentrations in Medes were significantly lower than those at the other two northern sites and were similar to those found in the more southern colonies (Fig. 2b) and also to those recorded in 1992 (0.52 ± 0.29 µg/g dw) at the same location (Sanpera et al 1997). Although there is some evidence that Atlantic fauna accumulate less Hg compared with biota from the Mediterranean (Renzoni et al 1998), the mean Hg residues in eggs from the two Atlantic colonies generally fell between the values recorded in eggs from the NM and SM colonies (Fig.…”

“…It also followed the recommendations of the United Nations Environment Programme and OSPAR for sampling and processing of biota samples (OSPAR Commission 2007; UN Environment). We collected the first layed egg, because it typically contains the highest within-clutch contaminant concentration, resulting from transfer from female to eggs (Sanpera et al 1997). The contents of 12 eggs from each subcolony were pooled.…”

“…Therefore, eggs appear to be good indicators of localised and contemporary environmental exposure. In Spain, Hg concentrations have been reported in the eggs of common terns ( Sterna hirundo) (Guitart et al 2003) and of Audouin’s gulls ( Larus audouinii ) from the Ebro Delta (Morera et al 1997; Garcia-Tarrason et al 2013), in Andouin’s gull eggs from Chafarinas Islands (Sanpera et al 2000), and in yellow-legged gull ( Larus michahellis ) eggs from the Medes Islands (Sanpera et al 1997).…”

Interspecific Differences in Egg Production Affect Egg Trace Element Concentrations after a Coal Fly Ash Spill

“…Other studies have suggested that laying order effects were more difficult to detect at low contaminant concentrations , and studies on waterbirds have reported more pronounced laying order effects at higher Se 23 and Hg 19 concentrations. Other studies that have examined the effects of laying order on the deposition of Se and other trace elements in avian eggs have found that trace elements may increase, decrease, , or not change with laying order. ,,− The inconsistency of laying order effects among studies may be due to differential availability of contaminants during egg production, ,, differences among contaminants in how they are incorporated into maternal tissue and eggs, or interactions among co-occurring contaminants. , Other studies indicated that small clutch sizes seem more likely to produce a laying order effect than large clutches. , When and if stored resources are utilized in egg production may also affect contaminant deposition and produce laying order effects . Methodological differences among studies may have contributed as well, because some of these studies inferred laying order or only sampled a portion of the clutch. , Many of the differences we detected occurred only between the first eggs and the last eggs laid and would have been missed had we examined only a portion of the clutch.…”

“…Furthermore, studies of maternal transfer often examine the contaminant contents of single eggs − or pooled egg samples and assume they are representative of the entire clutch. Studies demonstrating laying order effects on egg contaminant concentrations in birds suggest that this assumption is not always valid. − Within-clutch variation in egg contaminant concentrations could be the result of dietary shifts caused by heterogeneity in prey availability or nutritional needs, foraging across areas with heterogeneous contaminant “hot spots”, or interspecific variability in egg production. , Because maternally transferred contaminants can strongly impact reproductive success, understanding how among-species differences in egg production arise and affect embryonic exposure is critical for assessing health risks in vertebrate assemblages exposed to bioaccumulative contaminants.…”