10
2 Overview of the Aquatic Ecosystem
In recent times, some estuaries are under threat from environmental pollution,
disease outbreak and overfishing (Dame 2008). Some of these are due to the release
of toxins from factories and homes. This in turn distorts the balance in the ecosystem.
Losing estuaries means losing several species of aquatic plants and animals.
One of the recent threats studied in the estuaries of the Clyde, Bega and Hunter
estuaries in east coast of Australia revealed that increased human activities resulted
in higher microplastics in the estuaries (Hitchcock and Mitrovic 2019). In the three
estuaries studied, the microplastic pollution was as high as 1032 parts per m
3 in
the coast with the most populated Hunter estuary, to 98 part per m
3 in the Clyde
estuary which the coastal land is least populated by humans while Bega estuary had
a microplastic pollution of 246 parts per m
3 . Most of the microparticles had a particle
diameter below 200 µm.
2.2.2 Springs and Aquifers
In some parts of the earth, water accumulates under layers of rocks and sediments.
These are often artificially obtained by digging wells deep into the earth’s core and
either drawing out or pumping. Such water is relatively high quality as it is naturally
filtered through layers of rock and sand on the way out of the aquifer. They are used
for human consumption, agriculture and other activities important for life. In order
to conserve water and ensure the availability of aquifer-sourced water for future use,
it is important that the rate at which water is returned to the aquifer is balanced
with the rate at which it is being removed. Aquifer forms a relatively low energy
requiring source of clean water. Recharge zones are points in which rainwater seeps
back into the aquifer beneath and this makes up for the water removed either through
natural springs or by human activity. Recharge zones can be natural or man-made,
and these recharge zones experience dry and wet periods. While some aquifers show
rapid response to climate change, others show slow response. The response of an
aquifer to change in climate depends on the type of aquifer. An example is the
Northern Sudan Platform subbasin where average annual precipitation of 85 mm
was recorded between 2002 and 2012, and between 2013 and 2016, average annual
precipitation recorded was 107 mm (Abdelmohsen et al. 2019).
The underground water trapped within aquifers does not always need to be pumped
or drained by human activities. Due to the topology of the ground, the water escapes
from aquifers into the surface due to pressure difference and gravitational force. The
path through which the water flows is known as springs. This serves as a source of
natural spring water. These could either be slow moving or generate enough pressure
to form bubbling springs. The water from springs is usually of high quality due to
the fact that the rainwater flowing into the aquifers is filtered through different layers
of soil and rocks. Water flowing from springs forms a large part of waters in streams
and rivers in addition to annual rainfall.
2 Overview of the Aquatic Ecosystem
In recent times, some estuaries are under threat from environmental pollution,
disease outbreak and overfishing (Dame 2008). Some of these are due to the release
of toxins from factories and homes. This in turn distorts the balance in the ecosystem.
Losing estuaries means losing several species of aquatic plants and animals.
One of the recent threats studied in the estuaries of the Clyde, Bega and Hunter
estuaries in east coast of Australia revealed that increased human activities resulted
in higher microplastics in the estuaries (Hitchcock and Mitrovic 2019). In the three
estuaries studied, the microplastic pollution was as high as 1032 parts per m
3 in
the coast with the most populated Hunter estuary, to 98 part per m
3 in the Clyde
estuary which the coastal land is least populated by humans while Bega estuary had
a microplastic pollution of 246 parts per m
3 . Most of the microparticles had a particle
diameter below 200 µm.
2.2.2 Springs and Aquifers
In some parts of the earth, water accumulates under layers of rocks and sediments.
These are often artificially obtained by digging wells deep into the earth’s core and
either drawing out or pumping. Such water is relatively high quality as it is naturally
filtered through layers of rock and sand on the way out of the aquifer. They are used
for human consumption, agriculture and other activities important for life. In order
to conserve water and ensure the availability of aquifer-sourced water for future use,
it is important that the rate at which water is returned to the aquifer is balanced
with the rate at which it is being removed. Aquifer forms a relatively low energy
requiring source of clean water. Recharge zones are points in which rainwater seeps
back into the aquifer beneath and this makes up for the water removed either through
natural springs or by human activity. Recharge zones can be natural or man-made,
and these recharge zones experience dry and wet periods. While some aquifers show
rapid response to climate change, others show slow response. The response of an
aquifer to change in climate depends on the type of aquifer. An example is the
Northern Sudan Platform subbasin where average annual precipitation of 85 mm
was recorded between 2002 and 2012, and between 2013 and 2016, average annual
precipitation recorded was 107 mm (Abdelmohsen et al. 2019).
The underground water trapped within aquifers does not always need to be pumped
or drained by human activities. Due to the topology of the ground, the water escapes
from aquifers into the surface due to pressure difference and gravitational force. The
path through which the water flows is known as springs. This serves as a source of
natural spring water. These could either be slow moving or generate enough pressure
to form bubbling springs. The water from springs is usually of high quality due to
the fact that the rainwater flowing into the aquifers is filtered through different layers
of soil and rocks. Water flowing from springs forms a large part of waters in streams
and rivers in addition to annual rainfall.