Endosulfan is a commonly used organochlorine in Durham Region, Ontario Canada which has known toxic effects on non-target organisms including fish. This research investigated the effects of endosulfan on Florida flagfish (Jordanella floridae), using both continuous and pulse-exposure. The 96 hour continuous exposure LC50 in larval flagfish was 4.35 μg/L; sub-lethal observations included hyperactivity, convulsions, and some axis malformation. The effects of a 4 hour endosulfan pulse-exposure on 7-8 day-old larval growth, reproduction, and survivability were investigated over one full life-cycle. The 4 hour pulse-exposure LC50 value for larval flagfish was 49.7 μg/L; there were no growth or reproductive effects of endosulfan pulse-exposure up to the highest exposure concentration of 10 μg/L. Thus, the life-cycle 4-h pulse-exposure no observed effect concentration (NOEC) and lowest observed effect concentration (LOEC) were 3.2 and 10 μg/L endosulfan, respectively, due to significantly higher mortality.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are a class of drugs prescribed to relieve pain, fever and inflammation, and are among the most commonly consumed medications in Ontario. Approximately 70% of the ingested dose is excreted unchanged or as an active metabolite, much of which reaches the surface waters of lakes and rivers. NSAIDs function through the inhibition of cyclooxygenase (COX), an enzyme present in two isoforms in the body; the constitutively expressed COX-1 and the inducible COX-2. Traditional NSAIDs like ibuprofen inhibit both isoforms with little selectivity while newer variants such as naproxen preferentially inhibit COX-2. Both COX isoforms share a high similarity between humans and fish creating a potential for off target effects to exposed aquatic organisms. This research investigated the chronic effects of waterborne exposure to 0, 0.1, 1, 10 and 100 μg/L of a nonselective and selective NSAID (ibuprofen and naproxen, respectively) on Florida flagfish (Jordanella floridae) over one complete life-cycle. Chronic exposure concentrations were selected by performing a short term experiment which examined the hatchability of flagfish eggs using continuous semi-static exposure conditions. Growth, survivability and reproductive endpoints were assessed in the life-cycle study. A concentration-response relationship for both NSAIDs was detected during the first 28 days post-hatch, resulting in increased body length for F1 fish and their offspring with increasing concentrations. Exposure to 0.1 μg/L of both ibuprofen and naproxen resulted in a decrease in egg fertilization providing an experimental LOEC (lowest observable effect concentration) of 0.1 ug/L and NOEC (no observable effect concentration) of < 0.1 ug/L for both ibuprofen and naproxen based on the reproductive endpoint. This indicates that either NSAID has the potential to affect the reproductive success of flagfish at concentrations at or below those commonly found in the environment. / UOIT