May arsenic pollution contribute to limiting Artemia franciscana invasion in southern Spain?

Limited information exists regarding complex interactions between biological invasions, pollution, and climate change. Most studies indicate that pollution tends to favor invasive species. Here, we provide evidence that arsenic (As) pollution may contribute to limit the invasion of the exotic brine shrimp Artemia franciscana. We tested As toxicity in natural populations of Artemia parthenogenetica (native) and A. franciscana from high and low As contaminated environments in southern Spain, under current temperature conditions and as per a future climate scenario (i.e., an increase of 4ºC). Acute toxicity was estimated on the basis of the median lethal concentration (at 24h), and chronic toxicity (at 26 days) was evaluated by measuring Artemia survival and growth under sublethal exposures. At 25ºC native A. parthenogenetica from the highly polluted Odiel and Tinto estuary was much more resistant to acute As stress (LC50-24h, 24.67 mg L-1) than A. franciscana (15.78 mg L-1) and A. parthenogenetica populations from unpolluted sites (12.04 mg L-1) - suggesting that local adaptation to polluted conditions may occur. At 29ºC, resistance of A. parthenogenetica from Odiel decreased significantly, and there were no statistical differences in sensitivity between the three species/populations, suggesting that climate change may enhance the probability of invasion. Resistance increased with developmental stage from nauplii to adults, and was extremely high in cysts which still hatched at As concentrations of up to 6400mg L-1. Under sublethal chronic exposure A. franciscana performed better (survival and growth) than A. parthenogenetica, and both species experienced a faster growth when exposed, compared with unexposed (control) individuals, probably due to the hormesis. We discuss the ecological implications of our results.