2131 Environmental Toxicology and Chemistry, Vol. 27, No. 10, pp. 2131–2135, 2008  2008 SETAC Printed in the USA 0730-7268/08 $12.00 + .00 ACUTE LETHAL AND TERATOGENIC EFFECTS OF TRIBUTYLTIN CHLORIDE AND COPPER CHLORIDE ON MAHI MAHI (CORYPHAENA HIPPURUS) EGGS AND LARVAE RACHEL ADEMA-HANNES* and JONATHAN SHENKER Department of Biological Sciences, Florida Institute of Technology, Melbourne, Florida 32901 USA ( Received 18 June 2007; Accepted 3 April 2008) Abstract—Acute and chronic bioassays were used to evaluate the lethal and sublethal effects of copper chloride and tributyltin chloride on mahi mahi (Coryphaena hippurus) embryos, a pelagic life stage often found in the surface microlayer where anthro- pogenic contaminants can accumulate. Acute bioassay testing determined the median lethal concentration (LC50) for the test organism after 48 h of exposure. Chronic toxicity tests were used to determine the measurement of sublethal parameters, such as developmental abnormalities after 72-h exposures to the toxicants. Embryos were collected 4 h postfertilization and subsequently exposed to 1, 5, 25, 50, and 100 g/L of copper chloride and 3, 10, 20, 30, and 50 g/L of tributyltin chloride. Analysis of hatch rate percentage determined that the mean 48-h LC50 of copper chloride and tributyltin chloride was 32.8 and 16.7 g/L, respectively, based on the pooled data of four experiments with four replicates for each metal. Consistent abnormalities, such as yolk sac swelling, spinal deformities, and decreased hatch rates, were observed for each metal. Teratogenic responses to copper chloride and tributyltin chloride demonstrate the need to investigate further the impacts of pollution in the open oceans to a species indigenous to, and commercially important to, the Florida (USA) coasts. This information could then lead to the future development of a surface microlayer bioassay using mahi mahi embryos. Keywords—Sea-surface microlayer Coryphaena hippurus Tributyltin Copper INTRODUCTION The sea-surface microlayer (SMIC) is known to concentrate many natural and anthropogenic chemicals, particularly those that are surface active [1]. Egg and larval stages of many important fish use this microlayer. Thus, concern exists that anthropogenic contamination of the SMIC can impact the health of biological communities inhabiting this microlayer. Contamination of the SMIC with chemicals has been shown to be toxic to many organisms. Laboratory experiments using microlayer samples collected from several sites in Puget Sound (WA, USA) produced an increase in embryo and larval mor- tality and hatching time of the sand sole (Psettichthys melan- ostictus) and the English sole (Parophrys vetulus) compared to bulk-water samples [2,3]. Toxicity tests have been con- ducted using SMIC samples collected by standard screen or drum methods [4]. Experiments revealed an array of toxic effects to floating fish eggs and larvae, including increased mortality, growth inhibition, decreased hatching, developmen- tal, and chromosomal aberrations [5–7]. Results of investigations in the surface microlayer of the North Sea showed that between 5 and 26% of the embryos of plaice (Pleuronectes platessa), cod (Gadus morhua), and whiting (Merluccius merlangus) exhibited abnormal devel- opment [5]. These studies, however, have focused solely on inshore, cold-water marine fishes, and little information is available regarding the effects of toxicants on warm-water species that use the SMIC. Because of its beauty and fighting ability, the mahi mahi (Coryphaena hippurus) is one of the most popular sport fish globally. Its meat is prized for its flavor * To whom correspondence may be addressed (rachel.adema-hannes@mohawkcollege.ca) The current address of R. Adema-Hannes is Department of Nursing, Mohawk College, 1400 Main Street, W. Hamilton, Ontario L8S 1C7, Canada. Published on the Web 4/17/2008. and firm texture, and commercial harvesting has been suc- cessful both in the wild and in aquaculture. Taken together, these factors make the mahi mahi a suitable potential candidate for a warm-water toxicity monitor. This species releases pe- lagic eggs that float at or near the surface of the sea, and because to our knowledge no studies using this species are available for bioassay work, it is an ideal organism. Mahi mahi is a pelagic species that is cosmopolitan in trop- ical and subtropical seas [8]. Spawning in the region of the Florida (USA) current is concentrated in April and May [8]. Eggs are approximately 1 mm in diameter, and embryonic development takes approximately 40 h. The eggs hatch into relatively undeveloped yolk sac larvae, which lack a functional mouth, eye pigment, and differentiated fins. The buoyancy of their yolk sacs causes them to float upside down at the surface of the water column, in contact with the SMIC under very calm conditions. Minor turbulence under laboratory conditions mixes the eggs below the SMIC, so realistic exposure scenarios would include sub-SMIC waters. Numerous studies have defined the levels of copper that are sufficient to pose a threat, such as decreased survivorship, growth retardation, and observance of skeletal deformities, affecting different stages of some fish species and sea urchins [9–12]. Levels of copper in the environment are rising sig- nificantly as a result of human activities, such as mining or industrial activities, automotive emissions, use of chemical fertilizers, farm manure, sewage sludges, and wastewater ir- rigation [13]. Tributyltin (TBT) was chosen as a second toxicant because of its use as an antifouling agent in numerous formulations of marine paints. In October 2001, the International Maritime Organization introduced a global ban on the application of TBT paints to ships by January 2003, with a complete pro- hibition on the presence of TBT on ships by January 2008.