2.3 Aquatic Organisms
25
bacteria, viruses, protozoa and fungi. They can be of various classification such as
filamentous, rod-shaped or helical, aerobic, anaerobic or facilitators, heterotrophs,
autotrophs or mixotrophs (Little et al. 2001). Some exist within other organisms
where they have a symbiotic relationship with the host organisms. Examples of
such are the microbes which produce light within bioluminescent aquatic organisms.
These are discussed in later chapters of this book under bioluminescent proteins.
Other examples of symbiotic aquatic bacteria include those in the internal organs
of fish and the digestive bacteria in the utricle and stolon of the carnivorous aquatic
plant Utricularia breviscapa (Lima et al. 2018). Such bacteria aid in the digestion of
food and organic matter.
Aquatic microorganisms can either drift with the current suspended in the water.
These are generally classified as plankton (Meaning vagabond in Greek). Other
microorganisms are attached to substrates or within sediments in water. These are
known as the benthos (Greek word meaning depth) (Callieri et al. 2019). Planktons
are generally stationary; however, some possess some features sufficient to enable
them to maintain buoyancy. This allows them to migrate and aggregate as the nutrient
content and conditions vary, generally to move toward regions with nutrients and
favorable living conditions. Planktons serve as a food source for various species
which in turn are also a source of food to other organisms.
Benthos depend on the organic matter settled on the substrate they are attached to.
These types of microorganisms form biofilms which are the polymeric extracellular
matrix of the aggregates of microorganisms. The biofilms formed by these microbes
are crucial to their survival as it serves as a barrier through which nutrients and other
compounds are exchanged with the immediate environment (Kostakioti et al. 2013).
The biofilm enables the microorganism to adhere to the substrate in water; it also
serves a protective purpose to these benthic microorganisms. Outside of the natural
aquatic ecosystem, biofilm-producing bacteria also form on wet surfaces in everyday
life such as bathrooms, labs and hospitals. Microbes present in the water could be true
aquatic microorganisms which only exist in water while others are introduced from
land. The introduction of land microorganisms into water could be from seepage
from land or deliberate or accidental introduction of fecal waste into the water.
2.3.8 Humans
Since water serves as a source of food, means of transportation, source of energy,
recreation and aesthetics, for a very long time in human history, people have settled
along aquatic ecosystem. There are also communities in different parts of the world
who have settled on water. An example is the Makoko community in Lagos, Nigeria,
which is made up of humans who have constructed floating wooden houses on water
and use canoe and other floating objects as the primary means of transportation
within the water community (Riise and Adeyemi 2015). Similarly, the Satoyama
community in the ancient city of Kyoto in Japan have for centuries established a
harmonious relationship with the aquatic life which promotes biodiversity and also
25
bacteria, viruses, protozoa and fungi. They can be of various classification such as
filamentous, rod-shaped or helical, aerobic, anaerobic or facilitators, heterotrophs,
autotrophs or mixotrophs (Little et al. 2001). Some exist within other organisms
where they have a symbiotic relationship with the host organisms. Examples of
such are the microbes which produce light within bioluminescent aquatic organisms.
These are discussed in later chapters of this book under bioluminescent proteins.
Other examples of symbiotic aquatic bacteria include those in the internal organs
of fish and the digestive bacteria in the utricle and stolon of the carnivorous aquatic
plant Utricularia breviscapa (Lima et al. 2018). Such bacteria aid in the digestion of
food and organic matter.
Aquatic microorganisms can either drift with the current suspended in the water.
These are generally classified as plankton (Meaning vagabond in Greek). Other
microorganisms are attached to substrates or within sediments in water. These are
known as the benthos (Greek word meaning depth) (Callieri et al. 2019). Planktons
are generally stationary; however, some possess some features sufficient to enable
them to maintain buoyancy. This allows them to migrate and aggregate as the nutrient
content and conditions vary, generally to move toward regions with nutrients and
favorable living conditions. Planktons serve as a food source for various species
which in turn are also a source of food to other organisms.
Benthos depend on the organic matter settled on the substrate they are attached to.
These types of microorganisms form biofilms which are the polymeric extracellular
matrix of the aggregates of microorganisms. The biofilms formed by these microbes
are crucial to their survival as it serves as a barrier through which nutrients and other
compounds are exchanged with the immediate environment (Kostakioti et al. 2013).
The biofilm enables the microorganism to adhere to the substrate in water; it also
serves a protective purpose to these benthic microorganisms. Outside of the natural
aquatic ecosystem, biofilm-producing bacteria also form on wet surfaces in everyday
life such as bathrooms, labs and hospitals. Microbes present in the water could be true
aquatic microorganisms which only exist in water while others are introduced from
land. The introduction of land microorganisms into water could be from seepage
from land or deliberate or accidental introduction of fecal waste into the water.
2.3.8 Humans
Since water serves as a source of food, means of transportation, source of energy,
recreation and aesthetics, for a very long time in human history, people have settled
along aquatic ecosystem. There are also communities in different parts of the world
who have settled on water. An example is the Makoko community in Lagos, Nigeria,
which is made up of humans who have constructed floating wooden houses on water
and use canoe and other floating objects as the primary means of transportation
within the water community (Riise and Adeyemi 2015). Similarly, the Satoyama
community in the ancient city of Kyoto in Japan have for centuries established a
harmonious relationship with the aquatic life which promotes biodiversity and also