Bioassay of lower Narragansett Bay waters during the 1972‐1973 winter‐spring bloom using the diatom Skeletonema costatum1

Samples collected biweekly from lower Narragansett Bay from December 1972 through March 1973 were bioassayed with Skeletonema costatum at nine different enrichments with nutrients equivalent to f/25‐Tris medium. In early December growth rates were low in all treatments relative to complete enrichment; thereafter there was no evidence of nutrient limitation until late February. During this period of the winter–spring bloom growth was limited by the omission of NO3, SiO3, and PO4; deletion of vitamins and trace metals was less important. The addition of EDTA alone increasingly suppressed growth as the bloom developed; lysis was observed during late March.