A NOTE ON THE USE OF C 14 FOR MEASURING CARBON ASSIMILAnON IN EPIPHYTES

A NOTE ON THE USE OF C 14 FOR MEASURING CARBON
ASSIMILAnON IN EPIPHYTES
By
RICH. A. VOLLENWEIDER AND .AMm A. SAMAAN
Institute .1 Hydrobiology and Fisheries, Alexandria U.A.R.

INTRODUCTION
Since the introduction of the Cl4 method by Steemann Nielsen (1952) for
measuring organic production in the sea our knowledge concerning primary production of phytoplankton in the oceans and inland waters has been considerably
improved. However, nothing was done on epiphytic algae although they offer
many interesting aspects from the general point of view in limnoolgy as well as
for practical questions with respect to their value as fish food. Jorgensen (1967)
emphasises the interrelationship between the growth cycles in the phytoplankton
and epiphytic algae. Beside other vegetation, epiphytes grown on stones and
higher water plants are eaten by many herbivorous flshs, as was demonstrated
by Tilapio spp. in Egyptian Delta lakes. In such lakes a complete analysis
of food dynamics involves necessarily a study on the periphyton.
It is tempting to apply the same refined method proposed by Steemann
Nielsen for measuring the primary production of periphytoa. However, the
more heterogenous local distribution of epiphytes demands some modifications
on the original techniques. One modification which permits the study of at
least some aspects was developed by the authors and. was found to give records
within tolerable limits.