| Toxicological studies have long been used as tools to assess the affects of chemicals and pollutants on Daphnia and Chironomus . However, few studies have focused on sub-lethal responses in the exposed organisms throughout their life history. Understanding how organisms respond or adapt to sub-lethal exposure is crucial not only for toxic pollutants such as arsenic, but also for materials intended to have beneficial effects such as aluminum sulfate (alum). Our research has demonstrated the ability of Daphnia pulex to evolve adaptive life history strategies with pre-exposure to sub-lethal concentrations of alum. These strategies include higher survivorship, higher fitness, and larger adult and juvenile body sizes when compared to D. pulex with one-time alum or no-alum exposure. Our research also found that C. tentans experienced no delays in growth or development when raised in sediment containing alum. Although the larvae did experience higher deformity rates when compared to control larvae, this finding cannot conclusively demonstrate the deformities were a result of alum, because other metals including zinc, lead, and copper were found in the lake sediments. Finally, we found that arsenic can induce smaller body sizes, smaller head widths, slower development, and higher deformity rates in C. tentans larvae especially at medium and high arsenic concentrations. |
