The incidence of microplastics in marine environments has been increasing over the past several decades. The objective of the present study was to characterize the size- and shape-dependent effects of microplastic particles (spheres, fibers, and fragments) on the adult daggerblade grass shrimp (Palaemonetes pugio). Grass shrimp were exposed to 11 sizes of plastic: spheres (30, 35, 59, 75, 83, 116, and 165 μm), fragments (34 and 93 μm), and fibers (34 and 93 μm) at a concentration of 2000 particles/400 mL (= 50 000 particles/L) for 3 h. Following exposure, grass shrimp were monitored for survival, ingested and ventilated microplastics, and residence time. Mortality ranged from 0% to 55%. Spheres and fragments 50 μm ranged from 5% to 40%. Mortality was significantly higher in the exposure to 93-μm fibers than other sizes tested (p < 0.001). The shape of the particle had a significant influence on the number of particles ingested by the shrimp (p < 0.001). The residence time of particles in the gut ranged from 27 to 75 h, with an average of 43.0 ± 13.8 h. Within the gills, the residence time ranged from 27 to 45 h, with an average of 36.9 ± 5.4 h. The results suggest that microplastic particles of various sizes and shapes can be ingested and ventilated by adult daggerblade grass shrimp, resulting in acute toxicity. Environ Toxicol Chem 2017;36:3074-3080. © 2017 SETAC.

Size- and shape-dependent effects of microplastic particles on adult daggerblade grass shrimp (Palaemonetes pugio)

Triclosan, a commonly used antimicrobial compound, has been measured in aquatic systems worldwide. This study exposed marine species to triclosan to examine effects primarily on survival and to investigate the formation of the degradation product, methyl-triclosan, in the estuarine environment. Acute toxicity was assessed using the bacterium Vibrio fischeri, the phytoplankton species Dunaliella tertiolecta, and three life stages of the grass shrimp Palaemonetes pugio. P. pugio larvae were more sensitive to triclosan than adult shrimp or embryos. Acute aqueous toxicity values (96 h LC50) were 305 μg/L for adult shrimp, 154 μg/L for larvae, and 651 μg/L for embryos. The presence of sediment decreased triclosan toxicity in adult shrimp (24 h LC50s were 620 μg/L with sediment, and 482 μg/L without sediment). The bacterium was more sensitive to triclosan than the grass shrimp, with a 15 min aqueous IC50 value of 53 μg/L and a 15 min spiked sediment IC50 value of 616 μg/kg. The phytoplankton species was the most sensitive species tested, with a 96 h EC50 value of 3.55 μg/L. Adult grass shrimp were found to accumulate methyl-triclosan after a 14-day exposure to 100 μg/L triclosan, indicating formation of this metabolite in a seawater environment and its potential to bioaccumulate in higher organisms. Triclosan was detected in limited surface water sampling of Charleston Harbor, SC at a maximum concentration of 0.001 μg/L, substantially lower than the determined toxicity values. These findings suggest triclosan poses low acute toxicity risk to estuarine organisms; however, the potential for chronic, sublethal, and metabolite effects should be investigated. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008.

Toxicity of the antimicrobial compound triclosan and formation of the metabolite methyl-triclosan in estuarine systems

Mosquito repellents: An insight into the chronological perspectives and novel discoveries.

Complex factors have contributed to the decline of aquatic populations worldwide. Among these factors are intensification of agriculture, including the application of fertilizers and agents of crop protection, and loss of habitat. Various developmental abnormalities in natural populations of aquatic vertebrates have been documented, and agricultural pesticides are considered by many to be one of the important factors that cause such abnormalities. Amphibians may potentially be a target of environmental stressors and toxicants as a result of their biphasic life cycles and skin permeability. In this chapter, the role of oxidative stress in the teratogenic action of pesticides is reviewed and addressed, with special attention given to non-target aquatic organisms such as amphibians, fish, and invertebrates. The review of available literature indicates that many pesticides enhance oxidative stress in aquatic organisms, and such stress may be linked to developmental alterations, including reproductive effects, embryotoxicity, and/or teratogenicity.

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L. Serrano

Papers

Effects of the insecticide permethrin on three life stages of the grass shrimp, Palaemonetes pugio.