The productivity of the large brown alga Phyllogigas grandifolius (A. & E.S. Gepp) Skottsb. has been studied over a period of 2 1⁄2 years. This alga is endemic to the Antarctic and circumpolar in distribution. Photosynthesis was measured in situ using SCUBA, Uptake of 14C-labelled sodium bicarbonate was used to obtain values for gross photosynthesis throughout the year, and by monitoring respiration at the same time using the Winkler technique a value for daily accretion could be found. The curves for daily accretion showed only one mm maximum per season, that at the deeper of the two sites occurring later than at the shallow site, as the light levels reaching the deeper algae continued to increase. Positive accretion expressed in mugC. cm-2.d-1 was observed only during the summer months. Maxima in 1974 were 70 mugC. cm-2.d-1 at the shallow site and 56 at the deep site. Respiration was low throughout the year as a result of the small annual range of water temperature (+1.5°C to -2°C). The mean respiratory rate was found to be 1.55 mugC. cm-2.h-1 Variation in the rate was observed along the length of the frond with the maximum occurring in the region of the meristem about 10cm. above the base of the frond. In situ studies of frond growth showed a complete cessation of growth during the winter months but recommenced before the departure of the sea-ice. This and day length appear to be the two main limiting factors of growth. Mean growth rate: 8.0mm. wk-1. With the growing season restricted, to 6 months, the mean productivity for that season was found to be 2.4 g C.m-2.d-1, with a photosynthetic efficiency of 14%. In the winter this efficiency drops to 1%. These figures were obtained from bomb calorimetry studies. Mannitol, the main storage product and primary respiratory substrate showed summer maxima of around 18% dry weight, falling to 2% during the winter. Due to the irregular distribution of the alga, biomass estimates are rather subjective. One of the denser 'stands' of Phyllogigas gave a figure of 0.813 kg. m-2 and a Leaf Area Index of 4.5. Other LAI values were as low as 0.0028. The mean SLA was 0.075. The net annual primary productivity was found to be 15.3 metric tons, hectare-1 year-1.

Graduation date: 2001

No description available.

No description available.

Experiments were carried out in fall and winter, 1990 and spring and summer, 1991 , to determine growth and mortality of juvenile Pacific oysters {Crassostrea gigas) in effluent from cultured coho salmon {Oncorhynchus kisutch) , and effluent from salmon in which the red macroalga Palmaria mollis was cultured. Ambient sea water from Yaquina Bay was used as a control. Juvenile Manila clams {Tapes japonica) were also tested in summer, to compare the growth response of clams with that of Pacific oysters. Measured growth parameters included: increase in mean individual live weight, specific growth rate (% increase of mean live weight per day) and mean individual organic (ash-free) weight. Temperature, chlorophyll a, phaeopigment, carbon and nitrogen concentrations and C/N ratio for all treatments were also recorded during spring and summer, 1991. The oysters grew significantly faster in effluent from salmon and salmon conditioned by macroalgae than in the control during the Fall Experiment (September 7- 0ctober 31, 1990). Mean water temperature was 13-16°C. Growth rates were significantly greater in oysters cultured in salmon effluent than in the control during the Winter Experiment (December 7, 1990-February 15, 1991). However, growth was very poor due to low water temperatures (7-10°C). Growth of oysters was significantly greater in the control than in effluent from salmon and salmon conditioned by macrolagae in the Spring Experiment (March 7-May 24, 1991). Mean water temperature was 12°C. In the Summer Experiments, (June 3-July 4 and July 19-August 17, 1991) growth of oysters was more rapid in treatments with macroalgae as compared to treatments without macroalgae Comparative experiments with juvenile Manila clams gave similar results. Percentage mortality for both oysters and clams ranged from 0 to 5% and was highest during winter and lowest during summer. Mean chlorophyll values ranged from 1 μg/1 in spring, 1991 to 11 μg/1 summer, 1991. / Graduation date: 1992