Rates of phytoplankton cell division in the fib iron enrichment experiments

• Main Author: Karl Banse
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Pacific; Subarctic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.570.2318; http://www.aslo.org/lo/toc/vol_36/issue_8/1886.pdf

Increases in chlorophyll with time for contained coastal plankton, expressed as daily division rates, are on average about as high as rates for nutrient-replete cultures at similar temperatures, when daylength is considered. In offshore areas with persistent high nutrients but low chlorophyll, division rates from increased chlorophyll and cumulative NO, uptake in the controls of Fe en-richments are on average also high and do not suggest marked Fe deficiency. The normally observed phytoplankton growth in the controls is interpreted as due to release from grazing. Addition of Fe in the treatments leads to blooms and exhaustion of NO,. Differences between controls and treat-ments in rates of chlorophyll increase and NO, removal, however, as well as shifts in species composition toward rare species in the treatments, also indicate direct effects of Fe on phytoplank-ton. To clarify the issues, especially in respect to medium- and large-celled phytoplankton, I recommend measurements of species-specific division rates. In the large offshore areas of the subarctic Pacihc, the eastern equatorial Pacific, and the subantarctic, circumpolar Southern