Departmental Reports


Title:

Monitoring of Fish-Food Micro- and Macroorganism Production in the Forest Tent Caterpillar Pilot Project
on Mobile DeIta



Author(s):

Lawrence, J. and D. Bayne



Date: 1975



Funding Agency: U. S. D. A.



Keywords: mobile delta, alabama, fish food, productivity, limnology, water quality caterpillar control



Category: Domestic Funded Research Report



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Summary/Recommendations/Objectives:

This study of micro- and macro-aquatic organisms in a forested region of
the Mobile Delta was dcsigned to detect any effect the Dylox or Dipel treatment
used on the Forest Tent Caterpillar Pilot Project might have upon fish-food
organism populations. This Delta region was subjected to exi:ensive flooding
throughout the study period.
Three areas (2 were treated and one served as a control), each approximately
I, 000 acres in size, were utilized in this Project. Within each of these areas 4
·sampling sites were established. Pre-treatment sampling for water quality,
phytoplankton, and zooplankton was conducted on all sites on March 5, 1975.
Post-treatment sampling of the Dylox treated area and 2 sites within the control
area was accomplished on April I, 1975, and on the Dipel treated area and other
half of control area on April 8, 1975. Plate samplers to collect macroinvertebrates
were set in all areas on March 5. Post-treatment collection of plate samplers
from the Dylox and half of control area was made on April 1, and for Dipel and
other half of control area on April 8.
Comparisons of pre- and post-treatment data on phytoplankton populations
did not reveal any differences that could be attributed to either Dylox or Dipel
treatments. There was evidence that the extensive flooding within the area had
depressed the normal spring "bloom" of phytoplankton.

Pre- and post-treatment comparisons of zooplankton popnlations did not
reveal any effects that could be attributed to either Dylox or Dipel treatments.
It

 

was evident that the zooplankters had been able to increase their population


numbers under the adversities of flooding,
Comparisons of Dylox-control populations of macroinvertebrates did not
indicate any differences in numbers that could be attributed to the Dylox treatment.
Comparisons of the Dipel-control macroinvertebrate populations did
indicate a reduction in numbers of chironomids in the Dipel treated area. However,
these data are limited and additional studies will be needed to determine
if

 

Dipel exerts larvacidal effects upon aquatic Diptera larvae.


Water quality throughout the study period were adequate to support aquatic
life.

 

It was evident from these water samples that the river was transporting a


considerable quantity of suspended soil colloids.

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