The Sungei Buloh mangrove has water inputs from rivers, rain and the
sea. The wetland drains into the ocean as well as recieving water at
high tide. In Singapore the tides are mixed semi-diurnal tides.
This means the two high tides, and low tides, in each day are not of
equal height. The timing of the tides shifts by 50 minutes every day
because they are based on a lunar day (24 hours 50 minutes long). The
tidal range (difference in height between high and low tides) in
singapore is only 3.5 meters. This is very significant because in other
countries it is usually around 10 meters. The result being that
Singapore's mangrove forests are very narrow in depth.
(This chart from mangrove.nus.edu.sg shows the
different in the tidal hights between spring and neap tides.)
The high amount
of rainfall the the country recieves (see chart in climate section)
means that the rivers flowing through mangroves are flooded regularly,
especially during the monsoon season. This flushes detritus into the
mangrove, and eventually into the sea if not intercepted. The
ocean also brings dissolved and suspended nutrients into the mangrove
at high tide. These are taken up by the vegetation and eaten by filter
feeders like barnacles and mussels. The receding tide leaves
microscopic organisms on the ground which feed terrestrial wildlife at
low tide. Nutrients move back and forth between the ocean and the
wetland.
The sea water tends to be alkaline due to coral reefs leaching calcium into the water. However, the soils in mangroves are usually neutral to acidic. This is due to the presence of acidic clays and sulfur-reducing bacteria.
Dissolved oxygen is usually lower in the mangrove than in the sea, and eutrophic conditions can lead to further depletion from biological oxygen demand (BOD). The soils are anoxic as a rule, but the first few millimeters are aerated by the tides and atmospheric exchange.
The sea water tends to be alkaline due to coral reefs leaching calcium into the water. However, the soils in mangroves are usually neutral to acidic. This is due to the presence of acidic clays and sulfur-reducing bacteria.
Dissolved oxygen is usually lower in the mangrove than in the sea, and eutrophic conditions can lead to further depletion from biological oxygen demand (BOD). The soils are anoxic as a rule, but the first few millimeters are aerated by the tides and atmospheric exchange.
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