(350215709) nutrient cycle in aquaculture system
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Nutrient Cycle in Aquaculture System
SA3323
DR HELENA KHATOONSchool of Fisheries & Aquaculture
Sciences
Universiti Malaysia Terengganu
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What is nutrient cycle?
• Nutrient cycle (or ecological recycling) - movement &exchange of organic & inorganic matter back intoproduction of living matter
the
• Process is regulated by food web pathways thatdecompose matter into mineral nutrients
• Occur within ecosystems
• Begins with incorporation of substances into bodiesliving organisms from non-living reservoirs
of
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What is nutrient cycle?
• Materials pass from organisms that first acquireinto bodies of organisms that eat them
them
• Until they complete cycle & return to non-living world,through decomposition
• Refers to biodiversity within community food websystems that loop organic nutrients or water suppliesback into production
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Biogeochemical cycles
• continually through both biotic & abiotic componentsof ecosystems
• cyclic pathways involving biological, geological &chemical processes
• driven directly or indirectly by incoming solar radiationand gravity connect past, present, future forms of life
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3 main categories of biogeochemical cycles
• Hydrologic
• hydrologic (water) cycle
Gaseous - involves exchanges& oceans
• among atmosphere, biosphere, soils
•
•
•
Carbon Cycle
Oxygen Cycle
Nitrogen Cycle
• Sedimentary - involvesback
• Phosphorous cycle
• Sulfur cycle
materials that move from land to oceans and
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Carbon Cycling in Aquatic EcosystemsCarbon is an element that is the basis of all forms of life on Earth
•
• It moves through atmosphere, lithosphere, biospherehydrosphere
&
• Carbon cycle regulates Earth's global temperature &controls amount of carbon dioxide in atmosphere
• As carbon recycles, it is reused by numerousorganisms
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Carbon Cycling in Aquatic Ecosystems
• Aquatic ecosystems are those that contain plants &animals dependent on water
• If toocool
much CO2 is removed from atmosphere, it will
• If tooit will
much CO2 is added (or remains in) atmosphere, warm
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4 main reservoirs
• Lithosphere
• Biosphere
• Hydrosphere
• Atmosphere -
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LithosphereLargest reservoir for earth’ carbon - rocks such as limestone(CaCO3) deposited as sediment on ocean floor & on continents
Enters
• death, burial, compaction over geologic time
• becoming sediment, marine sediments, sedimentary rock, fossil fuels
Leaves - very slowly
• weathering, uplifting over geologic time, volcanic activity
• exception: combustion of fossil fuels
•
•
•
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Biosphere
• Biosphere is part of thesupports life of animals
Enters
• Photosynthesis
• consumption
Leaves
• cellular respiration
• death
earth & its atmosphere which& other living organisms
•
•
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HydrosphereOceans - second largest reservoir of earth’s carbon which play role in regulating amount ofCO2 in atmosphere
CO2 is readily soluble in water - some stays dissolved in sea water, some removed by
•
•marine photosynthesizing producers & some reacts with sea water to form carbonate ions(CO32-) & bicarbonate
Enters
ions (HCO3-)
•
•
•
•
•
•
Weathering
Leaching
runoff
diffusion
cellular respiration• Leaves
•
•
•
Photosynthesis
Diffusion
incorporation into sediments
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Atmosphere•
•
The gaseous envelope surrounding
Enters
the earth
•
•
•
•
•
cellular respiration
combustion of wood
combustion of fossil fuels
volcanic action
diffusion from ocean
• Leaves
• photosynthesis
• diffusion from the ocean
Flow of carbon in form of carbon• dioxide from atmosphere to biosphere(photosynthesis) and back to atmosphere (respiration)balance
- is approximately in
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Carbon cycle
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Types of ecosystem• Marine - largest ecosystems on Earth
• Most important subdivisions of marine ecosystems -oceanic, deep-water, estuarine, coral reefs, inter-tidalcoastal ecosystems
Living organisms range from bacteria, algae, corals, bivalves, fish & mammals
&
•
• Freshwater
• Major subdivisions - lakes & ponds, rivers & streams,reservoirs, wetlands & groundwater
• Living organisms include algae, fish, amphibians & plants
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Carbon Source
• Main source of the Earth's carbon is carbon dioxidegas from submarine volcanic eruptions
• Some of this carbon dioxide dissolves in ocean
• Another part escapes into atmosphere throughevaporation of ocean
• A further part is absorbed by marine biomass suchas plankton, algae & bacteria
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Photosynthesis
Plants & algae in freshwater & phytoplankton (marine organisms & algae) use sun's energy photosynthesis
•for
• They convert carbon dioxide & water they haveabsorbed into sugars & oxygen
• They store sugars as energy & release oxygen backinto water
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Fish
Freshwater algae & marine phytoplanktonfish
• are food for
• Fish inhale dissolved oxygen from water withexhale carbon dioxide back into water
their gills &
• They store carbohydrates they have eaten as energy &excrete inorganic calcium carbonate & bicarbonate
• These compounds are carried by currents to deep oceanwhere they precipitate
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Decomposition
• Dead organisms decompose on the river, lake orsea bottom and emit carbon dioxide
• The gas recycles into the freshwaterwhere other organisms absorb them evaporates into the atmosphere
and sea wateror the gas
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Precipitation
• Rainfall dissolves carbon dioxide in the atmospherereturns it as a mild acid to ground & water systems
&
• On the ground, rain water exposed carbonate rockssuch as limestone
• Limestone remains of inorganic carbonates thatprecipitated as excreta from fish & the skeletons of dead fish, corals or other marine life
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Run-Off
• Rainwater accumulates beneath the soil asgroundwater & runs off via rivers & lakes into seas
• Its carbon dioxide content is absorbed byfreshwater & marine organisms for photosynthesis& aquatic carbon cycle resumes
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Carbon cycle in freshwater & marine
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Nitrogen & Phosphorus Cycle
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• N & P - essential nutrients for plant growth
• Accelerated input of these two nutrients intoaquatic ecosystems due to human activities, is the primary cause of most algal bloom problems
• Nutrient cycle - the ways in which these elementsare transported & transformed within theenvironment, is therefore essential tounderstanding & effectively managing algal blooms
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• N & P cycles are fundamentally different to eachother
• N cyclingis mostly
- most common element in atmospheremediated by living organisms
-
• P cycling - is primarily a chemically mediatedprocess that originates with the weathering of rocks
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Nitrogen cycle• Nitrates are produced & used in aquatic ecosystems through a
process called nitrogen cycle
• Plant & animal by products first break down to produce ammonia
• Bacteria within the water oxidize that ammonia to produce nitrites, and then other bacteria colonies oxidize the nitrites to produce nitrates
• Nitrates are then used as a fertilizer for blue-green algae & aquatic plants, which enables plants & blue green algae colonies to grow & perform photosynthesis
• Plants become food for aquatic animals, which produce ammonia-rich waste, & nitrogen cycle begins again
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Major nitrogen & categories
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Plant & animal by products produceammonia
Protein in dead organic matter, such as in dead aquatic plantsbreaks down into ammonia as organic matter decays
•
• Waste from living aquatic animals, as well as the waste ofterrestrial animals that streams into waterways, also containsammonia
• Ammonia is toxic to all aquatic animal life
• Meanwhile, as the proteins and waste break down into ammonia,the living plants within the aquatic ecosystem release oxygen intothe water as a by product of their photosynthesis
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Bacteria oxidize ammonia to producenitrites
Nitrosomonas bacteria within the water bind ammonia in water with oxygen released by plants & oxygen that is mixed into water from air through movement at water's surface
•
• Oxidized ammonia that the nitrosomonas produce is called nitrite,also called NO2
• Like ammonia, NO2 also toxic to aquatic animal life
• Nitrosomonas bacteria oxidize ammonia in order to gain energythrough oxidation, which they use to fuel their metabolic
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Bacteria colonies oxidize nitrite toproduce nitrates
• Colonies of aquatic nitrospira bacteria then bind anotheroxygen to the nitrite, to produce nitrate (NO3)
& ammonia, nitrate is also toxic tois relatively neutral when compared
• Though, like nitratesaquatic animal life, itthose chemicals
to
• It is also in the form of nitrogen that can be directly absorbedby plants & cyanobacteria
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Blue-green algae & plants metabolize nitrates toproduce amino acids
• Cyanobacteria (blue-green algae) arephotosynthesis
aquatic bacteria that performs
• Though individual cyanobacteria are single-celled organisms, theygrow in colonies that can become so large they're visible to the naked eye
• A cyanobacterium also makes up the plant cell's chloroplast, whichis what allows the plant to perform photosynthesis
• Dead plant matter left over from feeding also releases ammonia intoaquatic ecosystem, fueling nitrogen cycle
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Blue-green algae & plants metabolize nitrates toproduce amino acids
• Amino acids make up proteinbuilding block of life
molecules, & protein is an essential
• Nitrate acts as a fertilizer for the aquatic plants
• Plants then become foodammonia-rich waste
for aquatic animals, which produce
• Dead plant matter left over from feeding also releases ammonia intoaquatic ecosystem, fueling nitrogen cycle
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Process of nitrogen cycle
• Assimilation – conversionNH4+) by phytoplankton &organic N
of inorganic N (mostly NO3 or other aquatic plants, into
• Ammonification – NH4+ (re)generation, resulting from decomposition of dead organisms & breakdown of animal wastes
• Nitrification – oxidation of NH4+ to NO2- & further oxidation of NO2- to NO3- by aerobic bacteria, which obtain energy through nitrification process
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Process of nitrogen cycle
• Recycling – refers to repeated movement of N through differentorganisms within an estuary via assimilation, ammonification &nitrification
• Sedimentation/resuspension – organic N from dead organismsfalls to the ecosystems floor & is incorporated into sediments;disturbance of sediments can return it to water
• Sediment flux – release of NH4+ from the sediments into overlyingwater
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Nitrogen cycle
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Nitrogen cycle
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Phosphorus cycle
• Phosphorus is found in soils, rock minerals,organisms & water
living
• but unlike nitrogen it is not present in atmospherefound by itself in nature
nor
• Pure phosphorus is highly reactive & rapidlycombines with oxygen when exposed to air
• In natural systems it usually exists as phosphate
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Forms of phosphorus in water• Orthophosphate is the major form of biologically available
phosphorus found in water. It is usually present as acombination of HPO4 2- and H2PO4- depending on pH
• Sum of all forms of phosphorus in water is known as Total
Phosphorus (TP)
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Process of phosphorus cycle• Adsorption – is process where PO4 binds to the surface of solid particles
Desorption – is reverse process where adsorbed PO4 is released into water
•
• Assimilation – uptake of PO4 & conversion to organic phosphorus, by phytoplankton & other organisms
• Mineralisation – release of PO4 from organic compounds by microbialbreakdown
• Sedimentation/resuspension – organic & particulate phosphorus falls toestuary floor & is buried in sediments; disturbance of sediments can return itto water
• Sediment flux – release of PO4 from sediments into overlying water
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Phosphorus cycle
http://arnica.csustan.edu/carosella/Biol4050W03/figures/phosphorus_cycle.htm
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Conclusion
Nitrogen & phosphorus contribute to problemin our coastal waterways
• of eutrophication
• These nutrients are present in several forms
• It is important to consider not just total nutrient conc. butof different forms of nutrient
conc.
• Dissolved inorganic nutrient conc. determine what plantscan access at any time
& algae
• But total conc. tell us a lot more about what may becomeavailable over time
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• There are important differences between nitrogen &phosphorus cycles
• Nitrogen is found in several different bioavailable forms,can be lost to atmosphere though denitrification
&
• Phosphorus cycle is dominated by one main bioavailableform (PO4) but is complicated by its reversible movementthrough both living organisms (assimilation-mineralisation)& particulate phases (adsorption-desorption)
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• Phosphorus does not exist as a gas & can only be physicallyremoved by being flushed from estuary or through permanent accumulation in sediments
• Both N & P can be released from sediments under anoxicconditions
• A coupled reduction in input of these two nutrients is onlyviable long-term approach to confronting problem ofeutrophication
• But direct intervention techniques provide additional optionsin the short term