UNIVERSITY OF LIVINGSTONIA
LAWS CAMPUS
FALCULTY OF EDUCATION
DEPARTMENT OF SCIENCES
TO
MR. K. MBEYA
FROM
GRITTY CHAMANGA
REG NUMBER
BES/01/33/21
COURSE TITLE
FRESH WATER BIOLOGY
COURSE CODE
BIO 3503
TASK
ANSWERING QUESTIONS
DUE DATE
24th NOVEMBER, 2023
QUESTION 1
Fresh water communities:
a) Phytoplankton: phytoplankton are very small floating photosynthetic organisms that
form the base of the food chain in the fresh water ecosystem. Phytoplankton that are
usually found in these ecosystems include, diatoms, green algae and blue-green algae
(cyanobacteria), and they all photosynthesize. These organisms are microscopic and
contribute so much in oxygen production through photosynthesis. In other words they
are the primary producer because they produce their own food through
photosynthesis.
b) Zooplankton: these are tiny organisms that are heterotrophic in nature. These
organisms are the primary consumers in the freshwater ecosystem, they feed on the
phytoplankton. Zooplanktons provide a link in the food chain that is transferring
energy from primary producers to higher trophic levels in the freshwater ecosystems.
Examples of zooplankton include, daphnia, copepods, rotifers and cladocerans
(Heneghan, Everett, Blanchard, Sykes, & Richardson, 2023).
c) Zoo benthos: these are organisms that inhabit the bottom of the freshwater
ecosystems. Examples of such organisms are snail, insects, crustaceans like crabs and
worms. These organisms are important decomposers that decompose decayed organic
matter and contribute to nutrient cycling in the ecosystem.
QUESTION 2
Food chains in freshwater ecosystem:
Blue-green algae→ snail → crayfish → turtle → heron
Green algae → daphnia →juvenile sunfish → bass → river otters
QUESTION 3
Chemical water quality parameters are those access the chemical composition of the water and
some of them are the following:
pH (acidity/alkalinity): pH is the measure of how acidic or alkaline the water is, and it is
measured on the scale of 0-14. The pH of water influences the chemical processes
happening in the water and the solubility of some minerals found in the water
Dissolved Oxygen (DO): dissolved oxygen is the amount of dissolved oxygen in the
waters. Dissolved oxygen in the water is from the photosynthetic activities by the plants
found there and from the atmospheric oxygen. It is essential for aquatic life because there
are some organisms that cannot survive in very low levels of oxygen. The amount of this
oxygen found in the water is also affected by the temperature, pressure and the amount of
organic matter decomposition.
Biological water quality parameters are important indicators of ecosystem health
and some of them are the following:
Biotic index: this is what measures the diversity and abundance of the organisms in the
freshwater ecosystem, by this parameter, the overall water quality is assessed. If the water
quality is good, more organisms will be found in abundance unlike when the quality is
poor.
Macroinvertebrate metrics: the presence and abundance of diversity of the different
invertebrates like the insects, crustaceans ie crabs, mollusks, will reflect the condition and
quality of the fresh waters. Again if they invertebrates are in abundance, that means the
quality is good enough favoring the survival of the organisms, but if they are less in
number that means the water quality is not good.
QUESTION 4
Four physical parameters of water quality:
Temperature
Turbidity
Conductivity
color
REFERENCES
Dudgeon, D. (2019). Multiple threats imperil freshwater biodiversity in the Anthropocene.
Current Biology, 29(19), R960-R967.
Heneghan, R. F., Everett, J. D., Blanchard, J. L., Sykes, P., & Richardson, A. J. (2023). Climate-
driven zooplankton shifts cause large-scale declines in food quality for fish. Nature
Climate Change, 13(5), 470-477.
Li, Y., Meng, J., Zhang, C., Ji, S., Kong, Q., Wang, R., & Liu, J. (2020). Bottom-up and top-
down effects on phytoplankton communities in two freshwater lakes. PLoS One, 15(4),
e0231357.
Omer, N. H. (2019). Water quality parameters. Water quality-science, assessments and policy,
18, 1-34.
Pradeep, V., Deepika, C., Urvi, G., & Hitesh, S. (2012). Water quality analysis of an organically
polluted lake by investigating different physical and chemical parameters. Int. J. Res.
Chem. Environ, 2(1), 105-111.
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