Primary productivity of reef-building algae was studied by putting samples from the reef in a closed system and measuring oxygen exchange in the light and in the dark. Gross productivity determined for 32 samples in full sunlight had a mean value of 0.048 mg 0 2 cm-2 hr-1. Photosynthesis was found to increase with the logarithm of light intensity up to 1,000 ft-c and was constant between 1,000 and 8,000 ft-c. Rates of gas exchange in flowing water showed no correlation with water velocity but were greater than rates in still water.Daily patterns of photosynthesis were calculated for populations of calcareous algae living on the submarine faces of the windward sides of atolls. During most of the daylight hours light is probably not a limiting factor for photosynthesis in these populations.Calculated productivity of various calcareous algal zones indicates that these zones do not contribute significantly to overall reef production on atolls of the northern Marshall Islands. Island reefs are less productive than previously studied inter-island reefs.

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Cpr6 and Cpr7, the Saccharomyces cerevisiae homologs of cyclophilin-40 (CyP-40), were shown to form complexes with Hsp90, a protein chaperone that functions in several signal transduction pathways. Deletion of CPR7 caused severe growth defects when combined with mutations that decrease the amount of Hsp90 or Sti1, another component of the Hsp90 chaperone machinery. The activities of two heterologous Hsp90-dependent signal transducers expressed in yeast, glucocorticoid receptor and pp60(v-src) kinase, were adversely affected by cpr7 null mutations. These results suggest that CyP-40 cyclophilins play a general role in Hsp90-dependent signal transduction pathways under normal growth conditions.

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