Water Quality in Aquaculture: An Introduction
In aquaculture,
water must provide a healthy environment for culture species, support feeding
and handle waste products. This course introduces various traits and
chemical properties of freshwater,
brackish water and ocean water, as
well as how they are measured and managed. It also explains osmotic pressure in
aquatic animals and
their need to live in environments with limited ranges of salinity. Alkalinity
and hardness are also covered.
pH Management in Aquaculture
Fish and shellfish must maintain fairly specific internal
pH levels. Chemical changes in water can shift pH and affect cell function and
even survival. This course explains the pH scale is an index of the
hydrogen ion concentrations in water, which can swing widely in ponds due to
levels of vegetation, temperature, aeration activity and bottom soil composition.
Learn to maintain pH between 7 and 8.5 with liming treatments and controlled fertilization,
stocking and feeding.
Total Suspended Solids Management in Aquaculture
Suspended
solids from source water, erosion, excess feed and feces can lower
dissolved-oxygen levels, contribute to water pollution and cause thermal
stratification. This course discusses
solids measurement
and recommends management through eliminating sources of turbidity and using
controlled applications of coagulants, if necessary. Learn to control erosion
by applying stabilization construction methods and treat turbid
conditions with organic fertilizers or inorganic flocculants.
Pond Liming and Fertilization
Liming of
aquaculture ponds between cycles and during production is an important
management tool. Liming materials neutralize acidity in soil and water, and
increase the alkalinity of culture water. Fertilization improves conditions for
healthy, managed growth of phytoplankton and other microorganisms. Students
will review the different types of organic and commercial fertilizer products,
as well as how to establish suitable rates of application based on practical
tests and past research.
Feeding and Water Quality
The
nutrients aquatic species take in through feed support healthy metabolism and growth. However,
feed waste products and uneaten feed are a major source of water quality
deterioration in aquaculture. Enroll in this course and learn to judge feed
quality and establish an effective feeding regimen that answers the nutritional
needs of the culture species. Understand feed conversion and feeding methods
that provide maximal diets while minimizing waste.
Dissolved Oxygen Management in Aquaculture
Dissolved
oxygen concentration is a primary water quality gauge in aquaculture systems. Low
concentrations stress culture animals and increase susceptibility to
disease. This
course explains the typical daily peaks in dissolved-oxygen levels and what conditions
affect how animals absorb oxygen from water. Learn how to measure dissolved-oxygen concentrations, as well as target and
maintain appropriate DO levels through feed and fertilizer management, and use
of aeration.
Phosphorus and Phytoplankton Management in Aquaculture
Phosphorus is an essential mineral for fish and shrimp,
and also a key regulator of phytoplankton growth in aquaculture ponds. Phytoplankton
supply natural food and oxygen through photosynthesis, but can cause thermal
stratification and reduce oxygen levels at night. This course describes the phosphorus cycle, as well as how to measure
phosphorus and phytoplankton levels. Phosphorus and phytoplankton must
be managed through controlled pond fertilization, stocking and feeding.
Ammonia and Toxic Metabolite Management in Aquaculture
High levels of molecular
metabolites formed as products of metabolic reactions can be toxic to aquatic
organisms. In aquaculture, the most problematic metabolites are ammonia, carbon
dioxide, nitrite and hydrogen sulfide. These substances enter culture water via
excretions from culture animals and organic decomposition. As explained in this
course, metabolites
can be limited through controlled feeding, mechanical aeration and treatments to maintain oxygen at the
sediment-water interface.
Water Circulation and Aeration
Still water tends to
develop defined layers based on temperature and chemical composition, which reduces
water quality with greater depth. This course outlines the dynamics of
circulation and explains what affects stratification in ponds and larger water
bodies. It compares various types of mechanical aerators and their best uses in
raising oxygen levels and improving bottom conditions. Learn about proper
siting and site management at cage sites in lakes and reservoirs, as well.
Pond Bottom Management in Aquaculture
Water quality in ponds
is influenced by interactions between chemical compounds in the water and those
in bottom soils. Decomposition of organic matter on pond bottoms removes dissolved
oxygen and can lead to the release of toxic metabolites. As described in this course, inputs can be reduced to improve sediment
quality. Mechanical aeration helps maintain conditions at the soil-water
interface. Bottom dryout between crops oxidizes organic matter and lessens its accumulation.