DDT and Other Organohalogen Pesticides in Aquatic Organisms

Organohalogen (OH) compounds are persistent hydrocarbon compounds containing a halogen group, often chlorine or bromine, that substitutes for hydrogen atoms in different positions in the hydrocarbon. They may occur naturally, but this chapter\u27s focus is on synthetically produced compounds, mainly organochlorines, that were produced for use as pesticides. Nine OH compounds (aldrin, chlordane, dichlorodiphenyltrichloroethane [DDT], dieldrin, endrin, heptachlor, hexachlorobenzene, mirex, and toxaphene) are in the top 12 list of particularly toxic and persistent organic pollutants (POPs) identified by the Stockholm Convention treaty implemented in 2004 under the United Nations Environment Program (UNEP). More than 90 countries have signed on to this treaty as Parties. These chemicals became classified as POPs because they may remain in the environment for decades following their use, they accumulate in fatty tissues of exposed organisms, they have a variety of toxic endpoints, and they travel long distances from source areas through atmospheric or aqueous transport

DDT and Other Organohalogen Pesticides in Aquatic Organisms

Organohalogen (OH) compounds are persistent hydrocarbon compounds containing a halogen group, often chlorine or bromine, that substitutes for hydrogen atoms in different positions in the hydrocarbon. They may occur naturally, but this chapter\u27s focus is on synthetically produced compounds, mainly organochlorines, that were produced for use as pesticides. Nine OH compounds (aldrin, chlordane, dichlorodiphenyltrichloroethane [DDT], dieldrin, endrin, heptachlor, hexachlorobenzene, mirex, and toxaphene) are in the top 12 list of particularly toxic and persistent organic pollutants (POPs) identified by the Stockholm Convention treaty implemented in 2004 under the United Nations Environment Program (UNEP). More than 90 countries have signed on to this treaty as Parties. These chemicals became classified as POPs because they may remain in the environment for decades following their use, they accumulate in fatty tissues of exposed organisms, they have a variety of toxic endpoints, and they travel long distances from source areas through atmospheric or aqueous transport

Embryotoxicity of maternally transferred methylmercury to fathead minnows (Pimephales promelas)

Mercury (Hg) is a ubiquitous environmental contaminant and potent neurotoxin. In aquatic environments, Hg can be transformed into methylmercury (MeHg), which bioaccumulates in aquatic food webs, including fish. Methylmercury has been shown to transfer from female fish to developing eggs; however, relatively little is known regarding the effects of maternally transferred MeHg on fish embryos. The present study evaluated the effects of maternally transferred MeHg on fathead minnow (Pimephales promelas) embryos. Embryos were collected from adult fatheads exposed for 30 d to 1 of 3 diets spiked with MeHg: a control diet (0.02 ppm Hg dry wt), a low diet (0.87 ppm Hg dry wt), or a high diet (5.5 ppm Hg dry wt). No effects on spawning frequency, clutch size, or total egg output were observed. In embryos, Hg concentration was a function of female diet and the duration (number of days) of female exposure. Compared with controls, embryos from the low‐diet treatment displayed altered embryonic movement patterns (hyperactivity) and decreased time to hatch. Embryos from the high‐diet treatment had delayed hatching and increased mortality compared with the other treatments. Collectively, these results suggest that maternally transferred Hg may impact survival, behavior, and developmental milestones of the embryo‐larval stages of fish. Environ Toxicol Chem 2016;35:1436–1441. © 2015 SETACPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/144636/1/etc3282.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/144636/2/etc3282_am.pd

Does maternal exposure to an environmental stressor affect offspring response to predators?

There is growing recognition of the ways in which maternal effects can influence offspring size, physiological performance, and survival. Additionally, environmental contaminants increasingly act as stressors in maternal environments, possibly leading to maternal effects on subsequent offspring. Thus, it is important to determine whether contaminants and other stressors can contribute to maternal effects, particularly under varied ecological conditions that encompass the range under which offspring develop. We used aquatic mesocosms to determine whether maternal effects of mercury (Hg) exposure shape offspring phenotype in the American toad (Bufo americanus) in the presence or absence of larval predators (dragonfly naiads). We found significant maternal effects of Hg exposure and significant effects of predators on several offspring traits, but there was little evidence that maternal effects altered offspring interactions with predators. Offspring from Hg-exposed mothers were 18% smaller than those of reference mothers. Offspring reared with predators were 23% smaller at metamorphosis than those reared without predators. There was also evidence of reduced larval survival when larvae were reared with predators, but this was independent of maternal effects. Additionally, 5 times more larvae had spinal malformations when reared without predators, suggesting selective predation of malformed larvae by predators. Lastly, we found a significant negative correlation between offspring survival and algal density in mesocosms, indicating a role for top-down effects of predators on periphyton communities. Our results demonstrate that maternal exposure to an environmental stressor can induce phenotypic responses in offspring in a direction similar to that produced by direct exposure of offspring to predators

Stratigraphy, Taphonomy, and Fauna-Substrate Associations in a Gulf of California Pleistocene Marine Terrace Near Punta Chueca, Sonora, Mexico

A richly fossiliferous Pleistocene terrace located near Punta Chueca, Sonora, Mexico, contains sediments that were deposited at the interface of an alluvial fan and shallow marine environment. Shell beds range from extremely dense fossil concentrations in sand, gravel, and cobble sized sediments to sparsely fossiliferous shell hashes. Three subenvironments were recognized: 1) shallow-subtidal to lower intertidal; 2) mid- to upper intertidal; and 3) supratidal. Shallow-subtidal to lower intertidal facies consist of shell beds with infaunal bivalves in life position, shell beds with fauna not in life position, and a Porites biostrome. Mid- to upper-intertidal facies include shell hash layers, and pebble and cobble lenses that are characterized by abundant autochthonous epi- faunal gastropods (i.e. limpets). Sparsely fossiliferous supratidal sands are overlain by Holocene alluvial fan deposits. Coarse conglomerates were not reworked by marine processes whereas finer conglomerates were, as evidenced by horizontal bedding and segregation of gravel and sand. The coarsest sediments - metamorphic cobbles - are relict and were probably derived from an earlier terrace. The following criteria were used to interpret the mode of shell bed formation: encrustation frequency, valve articulation, bivalve orientation, shell condition, and shell density (hardpart abundance). Storms played a major role in the formation of fossil concentrations. Four shell beds were interpreted as storm beds and one shell bed was interpreted as a condensed bed. Storm beds differ from condensed beds in having lower encrustation frequencies, higher percentages of articulated bivalves, and shells in very good condition. Association of hard-substrate faunas with gravel sediments and of infaunal molluscs with sand substrates suggests that little transport between habitats occurred. The high percentage of articulated valves, unworn appearance of most shells, predominance of concave-up oriented valves, and strong association of fauna with grain size all reflect a generally low energy environment, but one periodically disturbed by storm events.Antevs LibraryThis item is part of the Geosciences Theses collection. It was digitized from a physical copy provided by the Antevs Library, Department of Geosciences, University of Arizona. For more information about items in this collection, please email the Antevs Library, [email protected]