The effect of nutrient availability and temperature on chain length of the diatom, Skeletonema costatum

We determined the effects of temperature and nutrients on the chain length of a diatom, Skeletonema costatum, in batch culture and enclosure experiments with estuarine water from San Francisco Bay, USA, using the recently developed CytoBuoy flow cytometer. Determination of the number of cells per diatom chain by CytoBuoy flow cytometer and associated software correlated well with but was much more precise and time efficient than microscopic quanhfication. Increa* temperatures (from 6, 8 to 17 degrees C) and nutrient concentrations induced high growth rates and dominance by longer chains in a cultured S. costatum strain that was originally acclimatized to a temperature range of 11-30 degrees C. Similarly, a positive correlation between growth rate and chain length was observed in S. costatum in batch culture and natural communities in enclosure experiments. Maximal chain lengths of S. costatum were greater in natural populations than in the batch culture. Longer chains affect sinking rates and thus likely he the diatom remain suspended in the upper part of the water column where physical and chemical parameters are more favorable for growth.