Research

Toxic heavy metals and selenium are being transported from marine and terrestrial sources to freshwater wetlands in North Dakota by a migratory bird. Environmental levels of heavy metals and selenium are a cause for concern because of the potentially toxic effects for humans and wildlife and as such are often regulated and monitored. This study evaluates the role of Franklin’s gull (Larus pipixcan), a bird that migrates long-distances, in moving heavy metal and selenium among aquatic habitats. This is accomplished by estimating organic contributions (e.g., feathers and guano) by Franklin’s gulls to wetlands in North Dakota, via feathers and guano, and measuring heavy metal concentrations in the water, sediment, vegetation, aquatic invertebrates, and eared grebe (Podiceps nigricollis). The focus of this study is on cadmium and selenium concentration in the ecosystem as previous studies in Minnesota found elevated levels of selenium and cadmium in Franklin’s gulls and eared grebes. Of special concern are cadmium levels because it is a known carcinogen. Currently, it is unknown as to whether cadmium levels in Franklin’s gulls are still higher than that of other seabird species or if they have changed from levels found in the historic populations. It is also unknown as the whether historic levels differed between feathers made from South American and North American resources.

We collected feathers from juvenile and adult bird as concentrations of metals vary between life stages (i.e., eggs, juveniles, and adults) and from different breeding populations as metals concentrations also vary by region. We compared heavy metal levels in Franklin’s gull feathers made from North and South American resources and between juveniles and adults. Furthermore, we collected eggs from Franklin’s gulls and eared grebes to compare concentration differences between a species that forages in terrestrial and wetland environments (e.g., Franklin’s gull) and one whose food sources are restricted to within the wetland (e.g., eared grebe). These analyses will complement our current data set of heavy metal levels found in Franklin’s gull eggs. Additionally, we are interested in how the metals move throughout the environment once the feathers are degraded. This will be determined from elemental analysis of water, sediment, vegetation and aquatic invertebrates within the wetlands.

Significance

Previous studies of metals and selenium in Franklin’s gull and eared grebe have documented the concentration in tissues and eggs but have not attempted to use them as sentinels of environmental health. Additionally, by comparing heavy metal and selenium concentrations found in control wetlands to wetlands, we will be able to estimate the allochthonous inputs that is contributed by Franklin’s gulls and determine if the wetland systems where they breed are impaired. Elemental analysis of Typha and aquatic invertebrates will provide information on the level of heavy metal and selenium exposure that occurs in organisms that complete their life-cycle within the wetland.