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This study tested the influence of system complexity on the environmental assessment of a chemical. Marine microcosms were perturbed with a phthalate ester, di(2-ethylhexyl) phthalate (DEHP). Concentrations of 1, 10, and 100 µg of DEHP per litre were added to the water-column subsystem of marine microcosms for 30 days during the summer (18°C) and winter (1°C) seasons. Significant portions of the DEHP losses from the water-column subsystem during the experiments were due to the complete breakdown of the parent compound to carbon dioxide (CO2). In the benthic subsystem, DEHP concentrations in the sediment were increased by more than 50 and 250 times the concentration in the water column during the winter and summer seasons, respectively. Statistically significant (α = 0.05) reductions in the fluxes of ammonia (NH3) from the benthic subsystem were observed in microcosms receiving 100 µg of DEHP per litre during the summer. Concentrations of DEHP in selected bivalves ranged from 174 to 229 000 µg of DEHP per wet kilogram, depending upon the water column exposure concentrations and the season of the year.

1977. Temperature, photoperiod, and water-electrolyte balance in rainbow trout, Sulmo gairdneri. Can. J. Zool. 55: 1377-1388. The influence of temperature and photoperiod upon water-electrolyte balance was considered in animals acclimated to four combinations of two temperature (2, 18°C) and photoperiod (18 h light4 h dark, 6 h light-18 h dark) regimes through evaluation of Na, K, Ca, Mg, and C1 levels in plasma, skeletal, and cardiac muscle and liver. Water content and distribution and approximate cellular ion levels were estimated for skeletal muscle and liver. Evidence of significant influence upon water balance was obtained in one-half of the analyses performed, with effects being particularly pronounced in cold-acclimated, 'winter'-photoperiod specimens. Temperature effects were observed in two-thirds of the comparisons made with respect to electrolyte levels. These were not biased in relation to photoperiod. Most significant photoperiod-correlated variations in electrolyte levels (over one-half of the total considered) were observed at low ternperature. These observations are discussed in relation to compensation of rainbow trout for ternperature perturbation of the osmoregulatory and ionoregulatory systems, and the possible basis of photoperiodic influence upon these responses. MURPHY, P., et A. H. HOUSTON. 1977. Temperature, photoperiod, and water-electrolyte balance in rainbow trout, Salmo gairdneri. Can. J . Zool. 55: 1377-1388. On a analyse I'influence de la temperature et de la photoperiode sur I'equilibre hydrique et ionique chez des animaux acclimates a quatre combinaisons de temperature (2, 18°C) et de photoperiode (I8 h lumiere4 h obscurite, 6 h lumiere-18 h obscurite); les concentrations de Na, K , Ca, Mg et CI dans le plasma, dans les muscles squelettiques et cardiaque et dans le foie ont ete evaluees. On a estime le contenu et la repartition de I'eau, de mime que les concentrations approximatives d'ions dans les cellules, dans les muscles squelettiques et dans le foie.L'influence de la temperature et de la photoperiode s'est rnanifestee dans la moitie des experiences, particulierement chez les poissons acclimates au froid, a la photoperiode d'hiver. Les effets de la temperature sur les concentrations d'electrolytes se sont produits dans les deux tiers des cas; la photoperiode ne change rien dans ces cas. C'est a basse temperature que la photoperiode influence le plus les concentrations d'ions (chez plus de la moitie des poissons). On discute de ces resultats en fonction des mecanismes de compensation utilisks par la truite arc-en-ciel lors de perturbations de temperature des systemes osmoregulateur et ionoregulateur; on croit a I'influence possible de la photoperiode sur ces rnecanismes.[Traduit par le journal]