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A sequential procedure for the extraction of iron hydroxides and the associated phosphate in estuarine seston is proposed. The procedure which uses a citrate-dithionite-bicarbonate (CDB) reagent has been chosen among five commonly used methods. It makes it possible to distinguish four statistically different modes of association between P and Fe based on the (Fe/P)$ sb{ rm CDB}$ values. The extraction sequence is applied to suspend particulate matter and to surface sediments of the Saint-Lawrence Upper Estuary. The intensity and the position of the core of its maximum turbidity zone is determined by sediment exchanges between the channel and large intertidal flats. These exchanges are controlling seasonal fluctuations observed in the estuarine phosphorus geochemistry: The fresh to salt water early transition zone is the main site for the flocculation and deposition of river derived colloids, mainly as surface coating on particle, a process which results in phosphate adsorption on the suspended matter; After this process has reached equilibrium in the water column, partial desorption occurs on the flats as the particles settle temporarily in spring and summer. The P-depleted solids are returned to the estuary when the marsh vegetation is destroyed in the fall by migrating snow geese. Laboratory experiments with natural materials confirm the equilibrium level of P-adsorption observed in situ, and evidence its reversibility under the low reducing conditions typical of marsh surface sediments.

A comparative study of breeding ecology in Parakeet Auklets (Cychlorrhynchus psittacula (Pallas)), Crested Auklets (Aethia cristatella (Pallas)), and Least Auklets (A. pusilla (Pallas)) was conducted on St. Lawrence Island, Alaska, in 1966 and 1967. Emphasis was placed upon the climatic conditions which prevailed throughout the breeding seasons and their effects on timing of breeding in auklets. The pre-egg stage, egg-laying and incubation, hatching, growth of young, and departure of chicks were studied in both seasons; 1966 was a late year and 1967 was an early year. It was found that (1) Parakeet Auklets appear to have a more extensive migration than Aethia spp. , (2) arrival of adults back on the breeding grounds in spring occurs at approximately mid-May each year, (3) the pre-egg stage is prolonged but the post-breeding dispersal of adults and young from the nesting slope is rapid, (4) breeding does not take place at the same time each year, (5) Cychlorrhynchus breeds a few days later than Aethia spp., (6) a change in diet accompanies the onset of the chick-rearing period in Aethia spp. but not in Cychlorrhynchus, (7) patterns and rates of growth of A. pusilla chicks and possibly chicks of Cychlorrhynchus and A. cristatella differ according to time of hatching, (8) chicks of these auklets are well-adapted to early life, (9) predation upon auklets is low in the Sevuokuk colony, and (10) molt of adults overlaps the breeding effort in Aethia spp. but not in Cychlorrhynchus. Ecological and behavioral specializations in the annual cycles of these auklets revealed close synchronization and shortening of breeding events necessary for breeding in the short Arctic summer. It appears that these auklets are faced with two problems in timing their breeding cycles. Breeding must take place within a period which is largely dictated by climate and they must make best use of the food supply. / Science, Faculty of / Zoology, Department of / Graduate

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Note: Some illustrations out of order in manuscript.

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