Assessing the water fertility and toxicity of north-west part of lake Manzala (Egypt)‎ by an algal growth potential test

Abstract EN

Water fertility and toxicity of north-west pan of Lake Manzala in Egypt were investigated bimonthly from May.

1991 10 March.

1992.

Nutrient enrichment biotests to define algal growth limiting nutrients, their bioavailability and the heavy metal toxicity of the sampled water were achieved using Selenastrum capricornutum Strain NIVA-CHL I.

Maximum algal growth of the test alga was usually much higher than 10 mg dry WI L- I indicating the hypereutrophic conditions of the: investigated water and its undesirable: quality .

Algal growth potential test (AGPT) exhibited results ranging from 30.60 mg L- 1• to 1228.78 mg L- 1 algal dry weight .

The algal growth was mainly limited by N.

heavy metal toxicity and in few cases by P.

The: observed ChI.

a (phytoplankton chlorophyll a) was significantly lower than the expected ChI.

a.

No consistent interrelationship was found between the observed and the expected ChI.

a values.

The N:P weight ratio is a pertinent parameter for determining growth limiting nutrient.

The relationships belween the chemically analyzed nutrients (P and N) and their bioavailable concentrations were greatly affected by the N:P ratio and heavy metal toxicity.

Generally, the results of AGPT revealed that this technique is good.

effective and sensitive tool to assess the fertility.

nutrient bioavailability and toxicity of the lake Manzala waters.