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2 Overview of the Aquatic Ecosystem
At a low controlled level, aquatic plants add aesthetics to the aquatic environment
as some have colorful flowers. Aquatic plants also absorb the water waves and abate
the impact of flowing water which may lead to erosion. However, at uncontrolled
levels they tend to starve essential aquatic life of light and oxygen which are essential
to their growth. The death of the aquatic flora, the process of decay of these dead
plants commences which then results in the decomposing bacteria taking up all the
dissolved oxygen in the water, this then leads to the death of the fish and other aquatic
lives which require dissolved oxygen to survive. The humans who live around these
water bodies also depend on the fish as food and trade, once this depletes this also
affects the survival of the humans living around the hyacinth-infested waters.
2.3.2 Algae
Algae are polyphyletic; they are a group of photosynthesizing organisms which
belong to different kingdoms; some are plants while some are not; some are microscopic in nature while others are meters in length; and some are unicellular and
others multicellular. What they have in common is that they possess chlorophyll,
they photosynthesize, and however, they grow on water and do not have roots, stems
or leaves as terrestrial plants do (Cavalier-Smith 2007).
Although there are thousands of species of algae, they can be classified into
three main types: green, red and brown (Chlorophyta, Rhodophyta and Phaeophyta,
respectively) (Kadam et al. 2015; Bleakley and Hayes 2017). This classification is
mainly based on their domination pigments which give them the visible color. The
green algae include species such as Ulva lactuca, the red algae include species such
as Kappaphycus alvarezii, and the brown algae include species such as Laminaria
Japonica. Most brown and red algae are found in marine waters while green algae
can be found in freshwater. Some freshwater red algae exist albeit rare and brown
algae are almost exclusively found in marine water. Fucoxanthin is the pigment
responsible for the brown coloration of the phaeophyta, that of red algae are caused
by phycobilins while that of green algae is due to the presence of only chlorophyll.
The brown algae are all multicellular and could grow to tens of meters in length. The
red algae are also mostly multicellular while the green algae comprise unicellular
and multicellular species (Bleakley and Hayes 2017).
One of the direct uses of algae, particularly marine macroalgae, is as food for
humans and other animals (Fougere and Bernard 2019). Currently, algae have been
having both detrimental and potentially revamping effect to food security. Harmful
algal blooms threaten aquatic life, so does the potential for algae serving as a more
sustainable source of food (FAO, IFAD, UNICEF, WFP and WHO 2018).
Marine algae are usually found in the photic zone of the sea as they require
sufficient sunlight for photosynthesis. The importance of light for algae growth is
further emphasized in studies where in the absence of sufficient light, with surplus
nutrient supply, very little growth occurs even in the presence of abundant nutrients
(Prabhu et al. 2019). In the absence of light, the organisms are unable to convert
2 Overview of the Aquatic Ecosystem
At a low controlled level, aquatic plants add aesthetics to the aquatic environment
as some have colorful flowers. Aquatic plants also absorb the water waves and abate
the impact of flowing water which may lead to erosion. However, at uncontrolled
levels they tend to starve essential aquatic life of light and oxygen which are essential
to their growth. The death of the aquatic flora, the process of decay of these dead
plants commences which then results in the decomposing bacteria taking up all the
dissolved oxygen in the water, this then leads to the death of the fish and other aquatic
lives which require dissolved oxygen to survive. The humans who live around these
water bodies also depend on the fish as food and trade, once this depletes this also
affects the survival of the humans living around the hyacinth-infested waters.
2.3.2 Algae
Algae are polyphyletic; they are a group of photosynthesizing organisms which
belong to different kingdoms; some are plants while some are not; some are microscopic in nature while others are meters in length; and some are unicellular and
others multicellular. What they have in common is that they possess chlorophyll,
they photosynthesize, and however, they grow on water and do not have roots, stems
or leaves as terrestrial plants do (Cavalier-Smith 2007).
Although there are thousands of species of algae, they can be classified into
three main types: green, red and brown (Chlorophyta, Rhodophyta and Phaeophyta,
respectively) (Kadam et al. 2015; Bleakley and Hayes 2017). This classification is
mainly based on their domination pigments which give them the visible color. The
green algae include species such as Ulva lactuca, the red algae include species such
as Kappaphycus alvarezii, and the brown algae include species such as Laminaria
Japonica. Most brown and red algae are found in marine waters while green algae
can be found in freshwater. Some freshwater red algae exist albeit rare and brown
algae are almost exclusively found in marine water. Fucoxanthin is the pigment
responsible for the brown coloration of the phaeophyta, that of red algae are caused
by phycobilins while that of green algae is due to the presence of only chlorophyll.
The brown algae are all multicellular and could grow to tens of meters in length. The
red algae are also mostly multicellular while the green algae comprise unicellular
and multicellular species (Bleakley and Hayes 2017).
One of the direct uses of algae, particularly marine macroalgae, is as food for
humans and other animals (Fougere and Bernard 2019). Currently, algae have been
having both detrimental and potentially revamping effect to food security. Harmful
algal blooms threaten aquatic life, so does the potential for algae serving as a more
sustainable source of food (FAO, IFAD, UNICEF, WFP and WHO 2018).
Marine algae are usually found in the photic zone of the sea as they require
sufficient sunlight for photosynthesis. The importance of light for algae growth is
further emphasized in studies where in the absence of sufficient light, with surplus
nutrient supply, very little growth occurs even in the presence of abundant nutrients
(Prabhu et al. 2019). In the absence of light, the organisms are unable to convert