Plants were harvested on October 1, 2007, after eight
weeks’ growth in the experimental aquaria. Material harvested
from the mixed culture treatments was separated
according to species. The plants were washed over a
1 mm mesh sieve to remove attached sediment, debris,
and epiphytes. Plant tissues from all nine aquaria were
separated into two parts: aboveground and belowground.
The plant tissues were oven-dried at 80°C to constant
weight for about 12 hr and their dry mass recorded. The
plant material was then ground into fine powder in a
pestle and mortar for chemical (P) analysis. All samples
were digested with a mixture of H2SO4·H2O2 and tissue
phosphorus concentrations were analyzed by colorimetry.
The phosphorus concentration was expressed as mg phosphorus
per gram dry weight and total stored phosphorus
was calculated by multiplying concentration (mg P/g) by
plant biomass (g).