Abstract:
The Lunawa Estuary has
been selected as a model for studying
the long-term diagnoss of tropical
estuarine pollution and its impact on
ecosystems. Surface and short-core
sediments from the Lunawa Estuary
were collected, and analyzed for total
organic carbon (TOC), nitrogen,
sulfur and hydrocarbon contents,
hydrogen index and other related
sediment properties. Water quality
and surface sediment data indicate
that the Lunawa Estuary is presently
an anoxic water body. The upper
part of the sediment cores, characterized
by very high TOC values of
more than 10%, and absence of
bioturbation along with strong laminations
indicate anoxic water since
1970 AD, determined by 14 C dating.
However, before 1970 AD, lower
TOC content and presence of bioturbation
and homogenous sediments
with animal traces suggest the
presence of oxic bottom water and
thus a much better physicochemical
condition. The lower part of the
cores may also suggest the influence
of gradual global warming. Regular
laminations in the upper portions of
the cores probably resulted from
monsoon pulses with material preserved
under anoxic condition.
