A variety of contaminants find their way to the marine sediments from different sources, and these contaminants can pose serious risks to the natural marine flora and fauna. For example, pyrethroids, which are a potent pesticide family, are often used in agriculture fields worldwide, and these find their way into the marine environment through run off. Further, pyrethroids are used in farmed Atlantic salmon cages in Chile, Great Britain and Norway. Ammonia is another contaminant that is used in agriculture in form of ammonia-rich fertilizer and can be carried during run-offs to localized rivers and streams. Ammonia is also detectable after emission of effluents from sewage treatment plants and industrial plants like oil refineries and meat processing plants. Contaminants may have short and long term effects on non-target organisms living in the water column or in the marine sediment. Importantly, the sediment ecosystem houses a variety of plants, animals and crustaceans, including the American lobster Homarus americanus. Lobster is the most fished crustacean in New Brunswick and Quebec and its resale and exportation produced over $1.6 billion in 2011. Due to its economic and environmental importance, it is essential to study the effects of contaminants present in its ecosystem. Sediment samples are often used as pollution markers during toxicity testing due to their tendency to accumulate hydrophobic contaminants. To better understand the possible effects of contaminants in sediment, a total gene expression study was developed using the marine amphipod Eohaustorius estuarius. A 10 day spike-in exposure was performed using ammonia and two pyrethroids, namely cypermethrin and deltamethrin. As pyrethroids and ammonia are known to have vastly different mechanisms of action in living organisms, we compared global gene expression patterns following exposure to ammonia against the patterns observed following exposure to pyrethroids. Total gene expression was measured by oligonucleotide microarray. The expression of five genes of interest involved in different biological processes such as metabolism, transcription, translation, immunity and stress, which were found to be differently expressed by microarray, was validated by RT-qPCR. A set of genes was identified that showed differential expression levels in a treatment-dependent manner, thus further highlighting the different mechanisms of action of ammonia and pyrethroids in the marine sediment. This study provides a proof of concept for the use of DNA microarrays with model crustaceans for the study of marine sediment contaminants.
Overall design: This specific study is aimed at evaluating the effect of ammonia and pyrethroid exposure on E.estuarius and to identify possible biomarkers of these exposures.
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