CAS IN MARINE BIOLOGY
SUBMITTED BY – PRABIR SAHOO
M.Sc. Coastal Aquaculture,2nd sem
ROLL NO :2222020015
NUTRIENT CYCLES - Nitrogen Cycle,Sulphar Cycle & Phosphorus Cycle
WHAT IS NUTRIENT CYCLE ?
TYPES OF NUTRITENT CYCLE
• A nutrient cycle is the cyclic pathway by which
nutrients pass-through, in order to be recycled
and reutilised. The pathway comprises cells,
organisms, community and ecosystem.”
The cyclic pathway by which nutrients pass-
through, in order to be recycled and reutilised.
The pathway comprises cells, organisms,
community and ecosystem.” In the process,
nutrients get absorbed, transferred, released
WHAT IS NUTRIENT CYCLE ?
The nutrient cycle is a system where energy and matter
are transferred between living organisms and non-living parts
of the environment. This occurs as animals and plants consume
nutrients found in the soil, and these nutrients are then
released back into the environment via death and
decomposition. In forest environments, there is an exchange of
nutrient elements such as hydrogen, nitrogen and oxygen
among the soil, plants and animals living within the
What are the essential
The essential nutrient are mainly two types:
1.Non mineral elements : Carbon (C), Hydrogen (H), Oxygen (O)
2.Mineral elements : Macronutrients & Micronutrients(Nitrogen (N),
phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)
TYPES OF NUTRITENT
1. NITROGEN CYCLE :
Nitrogen Cycle is a biogeochemical process through which nitrogen is
converted into many forms, consecutively passing from the atmosphere to
the soil to organism and back into the atmosphere.
2.IMPORTENCE OF THE NITROGEN CYCLE:
• Helps plants to synthesise chlorophyll from the nitrogen compounds.
• Helps in converting inert nitrogen gas into a usable form for the plants
through the biochemical process.
• In the process of ammonification, the bacteria help in decomposing the
animal and plant matter, which indirectly helps to clean up the
PROCESS OF NITROGEN
THE PROCESS OF NITROGEN CYCLE HAVE MANY STEPS
• BIOLOGICAL NITROGEN FIXETION
•The sulphur is released by the weathering of rocks.
•Sulphur comes in contact with air and is converted into sulphates.
•Sulphates are taken up by plants and microbes and are converted into organic forms.
•The organic form of sulphur is then consumed by the animals through their food and thus
sulphur moves in the food chain.
•When the animals die, some of the sulphur is released by decomposition while some enter
the tissues of microbes.
•There are several natural sources such as volcanic eruptions, evaporation of water, and
breakdown of organic matter in swamps, that release sulphur directly into the atmosphere.
This sulphur falls on earth with rainfall.
Important steps of the sulphur cycle:
Decomposition of Organic Compounds
Protein degradation releases amino acids that contain sulphur. Sulphates are reduced to H2S by the action
of Desulfotomaculum bacteria.
Oxidation of Hydrogen Sulphide to Elemental Sulphur
Hydrogen sulphide oxidises to produce elemental sulphur. Certain photosynthetic bacteria from the
families Chlorobiaceae and Chromatiaceae initiate the oxidation process.
Oxidation of Elemental Sulphur
Elemental sulphur present in the soil cannot be utilized directly by the plants. Therefore, it is converted
into sulphates by chemolithotrophic bacteria.
Reduction of Sulphates
Sulphates are reduced to hydrogen sulphide by Desulfovibrio desulfuricans. This occurs in two steps:
Firstly, the sulphates are converted to sulphites utilizing ATP.
Secondly, the reduction of sulphite to hydrogen sulphide.
STEPS OF SULPHUR CYCLE
Phosphorus cycle is a very slow process. Various weather processes help to wash
the phosphorus present in the rocks into the soil. Phosphorus is absorbed by the
organic matter in the soil which is used for various biological processes.
Phosphorus is an important element for all living organisms. It forms a significant
part of the structural framework of DNA and RNA. They are also an important
component of ATP. Humans contain 80% of phosphorus in teeth and bones.
Steps of Phosphorus Cycle
Following are the important steps of phosphorus cycle:
Absorption by Plants
Absorption by Animals
Return to the Environment through Decomposition
STEPS OF PHOSPHORUS
The nitrogen cycle, bacteria and fungi help decompose organic matter, where the
nitrogenous compounds get dissolved into the soil which is again used by the
Through nutrient cycling, the various nutrients necessary for life on earth, move
from the respective nutrient pool (in the abiotic components) to the biotic
components and back. In nature, the nutrient cycles operate in a balanced manner.