Patel et al.

carbohydrates, proteins, amino acids, and phenols. where

content of the cells, which was found significant after

P <0.05 was considered as significant.

4 days of treatment. The effect of Acenapthene on

total chlorophyll, carotenoids and phycobiliproteins in

Results and Discussion

both microalgal species is shown in (Fig. 1a). Highest

The toxicity is influenced by viscosity and surface tension,

treatments of Acenapthene reduced total chlorophyll in

meteorological conditions, ecosystem, methods, other

C. vulgaris by 31% and 81%, while in D. subspicatus

environmental conditions (Gunkel and Gassmann, 1980).

reduced by 31% and 77% and 9% to 93% in Scytonema sp .

The effect of crude oil and other contaminants on marine

respectively after 4 and 16 days. The results were highly

microalgae can be assayed by growth measurements

indicative of their inhibitory effects on photosynthetic

(Atlas et al. , 1976 and Ukeles, 1965) or metabolic or

activities of the cells. Corresponding to total chlorophyll,

photosynthetic activities (Gordon et al., 1973, Soto

carotenoids

and

phycobiliproteins

decreased

with

1975 and Kusk 1978). We report herein on the effects of

increasingAcenapthene treatments. The reduction of 83%,

Acenapthene on the metabolic response of two different

97% and 96% was recorded in carotenoids content of the

microalgea and one cyanobacteria.

respective organisms after PAH treatment after 16 days.

(Fig. 1b) Fall of carotenoids of the microalga explained

Photosynthetic pigments and Metabolites

that the PAH not only accelerated the degradation but

also blocked their pigment synthesis.

Nevertheless, it must be taken into account that some

crude oils have been shown to be nontoxic to algae

Phycobilin contents of the cells ceased significantly by

(Coffey et al., 1977), whereas others are toxic (Kauss

95%, 89% and 84% in presence of Acenapthene on C.

et al., 1976) to various degrees depending on the species

vulgaris , D. subspicatus and Scytonema sp. after 16

studied and experimental conditions. Growth stimulation

days. (Fig. 1c, d, e) These water-soluble pigments were

or inhibition depends on PAHs concentration. Toxicity

found to degrade at a faster rate than those of total

was increased with higher concentrations, and longer

chlorophyll and carotenoids. The degradation of these

extension of the lag phase and lower cellular density in

photosynthetic pigments (phycocyanin, allophycocyanin

the stationary phase occurred. However, PAHs toxicity

and phycoerythrene) could be also attributed to the

level for microalgae may not be a reliable indication of

PAHs-thylakoid membrane negative interaction. The

what may happen in the natural environment.

findings are also in agreement with Mostafa et al. (2002)

who suggested that drop in chlorophyll-a, carotenoid and

In our study, Acenapthene treatments at various

phycobilinprotein contents might be ascribed due to the

concentrations caused reduction in the total chlorophyll

inhibition of pigment synthesis directly by the insecticide.

Fig. 1a: Variation in Chlorophyll content of algea treated with different doses of Acenapthene with increasing time.

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