The effects of toxicants on early developmental stages of two marine organisms: Giant kelp, Macrocystis pyrifera, and California mussels, Mytilus californianus

Early developmental events of the reproductive (gametophytic) stage were the focus of assessment of toxicant effects on Macrocystis pyrifera. Developing gametophytes were exposed to produced water (PW), an aqueous waste from oil production activities, and two common metal contaminants of coastal environments, arsenic (As) and copper (Cu). The developmental processes assessed were zoospore germination, germ tube elongation, and nuclear migration (determined by epifluorescence microscopy and the DNA fluorochrome, Hoechst 33342). Nuclear migration, encompassing replication and division of nuclear material into two nuclei with subsequent translocation of one of the nuclei, was determined to be the process most responsive to the toxicants.; To further explore the role of metabolism and pH in the completion of early nuclear events, developing M. pyrifera gametophytes were exposed to arsenic (sodium arsenate) and CCCP (carbonyl cyanide m-chlorophenylhydrazone) as well as a permeant weak acid and weak base. Exposure to As at time points coincident with DNA synthesis and nuclear division/translocation followed by assessment of DNA levels and nuclear translocation showed that both DNA synthesis and nuclear division/translocation were inhibited. Amelioration of As effects by phosphate enrichment was also observed, lending support to the hypothesis that As, as arsenate, disrupts energy metabolism in cells due to competition with phosphate. Both CCCP and the permeant weak base, {dollar}{bsol}rm NH{bsol}sb4Cl,{dollar} inhibited nuclear division/translocation, suggesting that intracellular alkalinization inhibits this microtubule-mediated process.; In an investigation of the effects of PW on a representative invertebrate species, California mussels (Mytilus californianus) were placed at 1, 10, 100, and 1000 m distances from the outfall of an oil processing plant to determine growth and reproduction in exposed adult mussels as well as effects on their offspring. Adult shell growth and gamete integrity (frequency of abnormal egg chromosome arrangement and fertilization rates) appeared to be negatively impacted at sites within the discharge plume. Spawning rates were highest in adult mussels nearest the outfall and embryos from these adults exhibited a greater tolerance to subsequent PW exposure. Larval shell development was more sensitive to perturbation by PW than development to the veliger stage.