Organochlorine pesticides and PCBs in a southern Atlantic coastal lagoon watershed, Argentina.

There recently have been increasing interest in South America on organic pollutants from the coastal marine environment. This study intended to seek out the occurrence and distribution of persistent organochlorine compounds in the Mar Chiquita coastal lagoon watershed. The levels were measured in sediments and associated crabs. Though a significant number of PCBs (mainly penta- and hexachlorinated congeners) were detected, the concentrations were very low (in the order of ppbs), indicative of an estuarine environment with little industrial development. On the other hand, pesticide residues were higher than PCBs in one or two orders of magnitude, as a result of the important agricultural activities in the area. Heptachlor epoxide, DDT and its metabolites, and gamma-HCH were the predominant OC pesticides in sediments as well as in crabs. Significant differences among geographical areas: Channel 5 and Vivoratá Creek (northern and southern sampling sites, respectively) contained detectable pesticide concentrations (heptachlor epoxide, DDE, DDD, and mirex).

PCBs and organochlorines in tissues of silverside (Odontesthes bonariensis) from a coastal lagoon in Argentina.

A freshwater fish species, silverside (Odontesthes bonariensis) from Mar Chiquita coastal lagoon, Argentina, was analyzed for concentrations of several organochlorine pesticides (OCs) and polychlorinated biphenyls (PCBs) in liver, gonads, mesenteric fat and muscle, and the contents of the digestive tract over several stages of sexual maturation. PCBs and OCs were detected at ng/g concentrations (wet weight) in pooled samples, with levels generally in the order of fat > liver > gonad > muscle, reflecting the differences in tissue lipid content. Lipid-normalized concentrations of the analytes were relatively consistent among tissues, except for significantly higher concentrations of PCBs (e.g., 447.7 ng/g lipid wt) in the ovaries of female silverside. DDT and its metabolites, gamma-HCH, and several insecticides from the cyclodiene class, including endosulfan and endosulfan sulfate, were the predominant OCs in fish tissues and the contents of the digestive tract, reflecting recent and past pesticide use in this region. The ratio of OCs to PCBs in all tissues was >1; consistent with contamination of the region with OC pesticides. However, PCBs were dominated by penta- and hexachlorobiphenyls, which is consistent with direct (i.e. , nonatmospheric) inputs. Biomagnification of penta- and hexachlorobiphenyl PCB congeners was noted in fish tissues relative to the contents of the digestive tract. Total OC and PCB concentrations in the ovaries and muscle of silverside were below concentrations associated with reproductive impairment in fish or the limits for human consumption, respectively.

Fatty acid metabolism in the calanoid copepod Paracalanus parvus: 1. Polyunsaturated fatty acids.

The metabolic fate of radioactive linoleate and alpha-linolenate administered to the South Atlantic copepod Paracalanus parvus was studied. The wild copepod was able to incorporate the labeled acids dissolved in seawater. The radioactive linoleate was elongated to 20:2omega6 and 22:2omega6 and desaturated by a delta6 desaturase to 18:3omega6. alpha-Linolenate was also desaturated by a delta6 desaturase to 18:4omega3 and elongated to 20:3omega3. The copepod was able to convert alpha-18:3 to 20:5omega3 and 22:6omega3.

Fatty acid metabolism of the calanoid copepod Paracalanus parvus: 2. Palmitate, stearate, oleate and acetate.

The de novo biosynthesis of fatty acids in the wild, calanoid copepod Paracalanus parvus was studied. The incubation of labeled acetate proved the de novo biosynthesis of saturated and monounsaturated even fatty acids from 14 to 20 carbons and the 22:1 acid. Saturated and monounsaturated uneven fatty acids from 15 to 21 carbons were also synthesized. The copepod could not synthesize linoleic and alpha-linolenic acids. By administration of [1-14C]palmitate, [1-14C]stearate and [1-14C]oleate, it was possible to elucidate the general pattern of the de novo biosynthesis of fatty acids in the wild P. parvus.

Lipid metabolism of the yellow clam, Mesodesma mactroides: 3-saturated fatty acids and acetate metabolism.

The fate of labeled palmitate, stearate, and acetate administered to the yellow clam, Mesodesma mactroides, was investigated. 1(-14)C palmitic and 1(-14)C stearic acids were oxidized to CO2 to a limited extent. They were mainly incorporated in diacylglycerols and triacylglycerols and were converted to higher homologs. After administration, palmitic acid was converted to stearic and oleic acids, whereas administered stearic acid was converted to 18:1, 18:2, 20:1, and 20:2 acids. Labeled acetate was readily included by the clam in 12:0, 14:0, 14:1, 15:0, 16:1, 16:1, 16:2, 18:2, 18:1, 18:2, 20:1, 20:2, and 20:3 acids.

Lipid metabolism of the yellow clam, Mesodesma mactroides: 2-polyunsaturated fatty acid metabolism.

The fate of labeled linoleic, alpha-linolenic, and higher homologs of alpha-linolenic acid administered to the yellow clam, Mesodesma mactroides, was investigated. It was found that the clam incorporated the acids dissolved in sea water and converted 18:2 (n-6) into 20:2 (n-6) and 18:3 (n-3) into 18:4 (n-3) and 20:3 (n-3). The addition of casein hydrolysate to the sea water increased the desaturation capacity of the calm and allowed the conversion of 18:2 (n-6) into 18:3 (n-6) to be demonstrated. An enhanced desaturation of 18:3 (n-3) into 18:4 (n-3) was also demonstrated. After 12 hr admininistration of the acid, no radioactivity was found in arachidonic, 20:5 (n-3), or 22:6 (n-3). Feeding the clams a culture of Phaeodactylun tricornutum previously incubated with 1-14C-alph-linolenic acid demonstrated that all the homologs of the alpha-linolenic series were found in the clam without any important changes. Six hour administration of labled linolenic acid resulted in the incorporation of the acid into diglycerides and phospholipids.

Lipid metabolism of the yellow clam, Mesodesma mactroides: I. Composition of the lipids.

The lipid composition of the yellow clam, Mesodesma mactroides, that lives in the northern beaches of the Buenos Aires province of Argentina was studied. The main nonpolar lipids are triglycerides and alkoxyglycerides. Phosphatidyl choline, phosphatidyl ethanolamine, and phosphatidyl serine are the main phospholipids. The predominant fatty acids are 16:0, 16:1omega7, 18:0, 18:1omega9, 20:5omega3, and 22:6omega3. They are mainly provided by the clam's food and stored in the hepatopancreas. The content of polyunsaturated acids increases in summer together with an increase in nonpolar lipids and is correlative with an increase in phytoplankton in the sea water. Sexual maturity modifies the lipid composition of gametes.