Copper toxicity to microscopic stages of giant kelp Macrocystis pyrifera:interpopulation comparisons and temporal variability

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Abstract
Experiments were conducted to evaluate temporal and geographic variation in sensitivity of microscopic stages of giant kelp Macrocystis pyrifera to copper. Spores from kelp sporophylls collected from different locations and at different times of the year were exposed to series of copper concentrations following a standard toxicity test procedure. After 48 h static exposures, toxicity was determined by measuring 2 test endpoints: germination success and growth of germination tubes. The sensitivity of these endpoints to copper was also compared with the sensitivity of longer-term reproductive endpoints: sporophyte production and sporophyte growth. No significant differences in response to copper were found among spores from different collection sites. Variability between 4 tests conducted quarterly throughout the year was greater than that between 3 tests done consecutively within 1 mo, indicating temporal variability in response to copper. Long-term reproductive endpoints were more sensitive to copper than were short-term vegetative endpoints, with No Observed Effect Concentrations of < 10 .mu.g l-1 for sporophyte production, 10 .mu.g l-1 for sporophyte growth, 10 .mu.g l-1 for germ-tube growth, and 50 .mu.g l-1 for germination inhibition.

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