Uptake of lead (pb) and cadmium (cd) by two species of mangrove (rhizophora apiculata and avicennia alba) grown hydroponically and in field conditions
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Date
2006
Authors
Irnasari
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Abstract
Mangrove ecosystems act as buffer zones for heavy metal mobilization before these
reach the off shore areas. Therefore, evaluation of the uptake of some heavy metals by
mangrove species is important. In natural conditions, uptake of metals by mangrove
plants is controlled by physicochemical conditions in mangrove sediments that are rich
in organic matter. Thus, to exclude these physicochemical effects, a hydroponic
method was applied. An assessment of Pb and Cd uptake by mangrove species was
carried out both in laboratory experiments and field cultivation. The effect of salinity on
Pb and Cd uptake by R. apiculata and A. alba as well as the influence of heavy metals
and salinity stress on the growth of both species have been investigated using
hydroponic cultivation in the laboratory. After 3 months exposure to various levels of Pb
(0.03; 0.3 and 3mg/l) and Cd (0.005; 0.05 and 0.5mg/l) under various salinity regimes
(0 °/oo. 15 °/oo and 30 °/00), Pb and Cd were significantly accumulated in the roots of both
mangrove species. A. alba showed higher uptake of Pb and Cd compared to R.
apiculata, especially in their leaves reaching two fold. The laboratory study also
showed that salinity was found to significantly inhibit the Cd uptake by R. apiculata and
A. alba. The total concentration of Cd in R. apiculata at salinity 30°/00 reduced around
34% and around 22% for A. alba from Cd concentration at 0 °/00 salinity. However, both
species showed the best growth at salinity 15°/00. Salinity was also suggested to
reduce the toxic effects of Pb and Cd on mangrove plants. The assessment of metal
uptake by mangrove species under natural conditions was conducted at two mangrove
areas, Merbok mangrove forest and Juru. The metal uptake from mangrove sediments
by R. apiculata under field experiment was lower than under hydroponic cultivation.
However, the translocation of metals from the roots to the shoots (stems and leaves)
were quite similar. Finally, lower metal uptake by mangrove species under natural
conditions may be related to the metal behaviour in mangrove sediments where they
can be immobilized by the physicochemical properties of the sediments, such as their
organic content.
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Keywords
Lead (pb) , Two species , Grown hydroponically , Mangrove (rhizophora apiculata) , Avicennia alba