Duckweed Elodea And Algae Why Are They Important Answer Key Pdf

duckweed elodea and algae why are they important answer key pdf

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The relationship between elodea and snails has been the subject of science experiments in elementary schools for years.

Citation of this paper. Duckweeds have received research attention because of their great potential to remove mineral contaminants from waste waters emanating from sewage works, intensive animal industries or from intensive irrigated crop production. Duckweeds need to be managed, protected from wind, maintained at an optimum density by judicious and regular harvesting and fertilised to balance nutrient concentrations in water to obtain optimal growth rates.

Sample. Setting Up the Aquarium LESSON 3. Overview and Objectives. Background

Citation of this paper. Duckweeds have received research attention because of their great potential to remove mineral contaminants from waste waters emanating from sewage works, intensive animal industries or from intensive irrigated crop production. Duckweeds need to be managed, protected from wind, maintained at an optimum density by judicious and regular harvesting and fertilised to balance nutrient concentrations in water to obtain optimal growth rates.

Duckweeds have been fed to animals and fish to complement diets, largely to provide a protein of high biological value. Mature poultry can utilise duckweed as a substitute for vegetable protein in cereal grain based diets whereas very young chickens suffered a small weight gain reduction by such substitution. Little work has been done on duckweed meals as supplements to forages given to ruminants, but there appears to be considerable scope for its use as a mineral particularly P and N source.

The protein of duckweeds requires treatment to protect it from microbial degradation in the rumen in order to provide protein directly to the animal. The combination of crop residues and fresh duckweeds in a diet for ruminants appears to provide a balance of nutrients capable of optimising rumen microbial fermentative capacity.

These diets can, therefore, be potentially exploited in cattle, sheep and goat production systems particularly by small farmers in tropical developing countries. Duckweed species are small floating aquatic plants found worldwide and often seen growing in thick, blanket-like mats on still or slow moving, nutrient-rich fresh or brackish waters.

They are monocotyledons of the botanical family Lemnaceae and are higher plants or macrophytes, although they are often mistaken for algae. Many species of duckweed cope with low temperatures by forming a turion and the plant sinks to the bottom of a lagoon where it remains dormant until warmer water brings about a resumption of normal growth.

Duckweeds have structural features that have been simplified by natural selection. A duckweed leaf is flat and ovoid. Many species have adventitious roots which function as a stability organ and which tend to lengthen as mineral nutrients in water are exhausted.

Roots, however, appear to be more fibrous. As a result the plant has little or no indigestible material even for monogastric animals. Duckweed species are adapted to a wide variety of geographic and climatic zones.

They are found in all but waterless deserts and permanently frozen areas. They grow best in tropical and temperate zones and many species can survive temperature extremes. The natural habitat of duckweed is the surface of fresh or brackish water which is sheltered from wind and wave action. The best nutritional situations for duckweed growth are in waters with decaying organic material, providing it with a steady supply of nutrients.

A dense cover of duckweed inhibits competing submerged aquatic plants, which require solar energy for growth and they can also often exclude algae from bodies of water. The best conditions for cultivation of duckweed simulates the favoured natural environmental niche, namely a sheltered lagoon or a lagoon with surface partitions to prevent wind from blowing the plants onto the banks causing conditions of self shading and competition for nutrients.

For high growth rates, nutrients must be made available, at a rate commensurate with growth, being derived either from organic or mineral fertilisers added daily. Duckweed reproduction is primarily vegetative. An individual leaf may go through 10 divisions over a period of 10 days to several weeks before the original plant senesces.

Duckweeds can double their mass in between 16 hours to 2 days under optimal nutrient availability, sunlight, and water temperature. This is faster than almost any other higher plant. The growth pattern resembles the exponential growth of unicellular algae more than that of higher plants and this confers a high potential for production as a livestock feed resource.

Growth rates of duckweed colonies will be reduced by a variety of stresses: such as nutrient scarcity or imbalance; toxins; extremes of pH and temperature; crowding by overgrowth of the colony and competition from other plants for light and nutrients.

However, when conditions are good, duckweed contains considerable protein, fat, starch and minerals which appear to be mobilised for biomass growth when nutrient concentrations fall below critical levels for growth. The reported nutrient densities in duckweed therefore vary according to conditions of growth Table 2. Fibre and ash content are higher and protein content is lower in duckweed colonies that grow slowly. Nutrients are absorbed through all surfaces of the duckweed leaf. There are at least three methods of fertiliser application including broadcasting, dissolving in the water column of the plot, and spraying a fertiliser solution on the duckweed mat.

Efficient crop management strategies need to maximise fertiliser uptake and at the same time minimise fertiliser losses, particularly nitrogen, while also maintaining the pH of the water in the range of Duckweed survives from pH 5 to 9, but grows best over the pH 6.

Ammonia, in the ionised form is the preferred N substrate for duckweed. As a generalisation, duckweed growth is controlled by temperature and sunlight more than nutrient concentrations in the water. At high temperatures, duckweeds can grow rapidly down to trace levels of P and N nutrients in water. Urea is a suitable fertiliser which is rapidly converted to ammonia under normal conditions. Fast growing duckweed on nutrient-rich water is a highly efficient sink for both phosphorus and potassium, but little of each is required for rapid growth.

Muriate of potash and superphosphate are commercial sources of potassium and phosphorus that are widely available in most countries and have been used where duckweed has been farmed. Duckweed growth is not particularly sensitive to potassium or phosphorus once an adequate threshold has been reached.

The effect of water phosphorus content on duckweed phosphorus concentration is shown in Table 4. Thus duckweed efficiently concentrates P and could be an important source of P particularly for grazing ruminants in the tropics where P- deficiency is widespread. However, recent research showed that levels of up to 1.

Trace mineral requirements for duckweed growth are unknown although it appears the plant is able to concentrate some trace minerals more than , times. Sea salt has been regarded as a good source of trace minerals to use in duckweed farming. In work in these laboratories, molasses which is a concentrated plant juice has been used to safe guard the trace mineral requirements of duckweed. Duckweed species are able to survive extremely adverse conditions.

Their growth rate is, however, highly sensitive to the major nutrient balances in the water. They can survive and recover from extremes of temperature, nutrient loadings, nutrient balance, and pH. However, for duckweed to thrive, these four factors need to be balanced and maintained within reasonable limits. Crop management and therefore the initial research requirements are concerned with when to fertilise, harvest, and buffer; how much to fertilise and to harvest; and which nutrients to supply.

Judicious management should be aimed at: i maintaining a complete and dense cover of duckweed; ii low dissolved oxygen; and iii a pH of 6- 7. A total crop cover suppresses algal growth, which minimises CO 2 production from algal respiration and prevents its elevating effect on pH.

Any waste organic material can be used to supply duckweed with nutrients. The most economical sources are wastewater effluents from homes, food processing plants, cattle feedlots, and intensive pig and poultry production. Solid materials, such as manure from livestock, night soil from villages, or food processing wastes, can also be mixed with water and added to a pond at suitable levels.

All wastewater containing manure or night soil must undergo an initial treatment by holding it for a few days in an anaerobic pond, before using it to cultivate duckweed.

There is an additional need when using such sources of nutrients to reduce solids and prevent the formation of a floating mat. The basic concept of a duckweed wastewater treatment system is to farm local duckweeds on the wastewater which needs to be treated. The rapidly growing plants act as a nutrient sink, absorbing primarily nitrogen, phosphorus, calcium, sodium, potassium, magnesium, carbon and chloride from the wastewater.

These ions are then removed permanently from the effluent stream following the harvesting of a proportion of the crop.

Depending on the wastewater, the harvested crop may serve as: i an animal feed; ii feed supplement supplying protein and minerals; or iii fertiliser. However, it may have to be decontaminated prior to feeding to animals if heavy metals are present in the water as these are concentrated by the duckweed.

Maintenance of efficient duckweed growth requires an even distribution of a thick layer of plants across the entire lagoon surface.

Initial research has shown that there is a range of plant densities that supports optimum growth rate for prevailing conditions. The upper density appears to be that at which crowding limits growth above 1. The composition of duckweed depends on the nutrient content of the water and the prevailing climatic conditions. A range of values for the composition of duckweed is shown in Table 2. Duckweed protein has a better array of essential amino acids than most vegetable proteins and more closely resembles animal protein Hillman and Culley It is, therefore, a source of high quality protein to be exploited for domestic animal production.

Duckweed grown on nutrient-rich water has a high concentration of trace minerals, K and P and pigments, particularly carotene and xanthophyll, that make duckweed meal an especially valuable supplement for poultry and other animals, and it provides a rich source of vitamins A and B for humans.

A major limitation to fish farming is that meals high in protein with high biological value are expensive and often locally unavailable. Fresh duckweed is highly suited to intensive fish farming systems with relatively rapid water exchange for waste removal Gaigher et al and duckweed is converted efficiently to liveweight by certain fish including carp and tilapia Hepher and Pruginin ; Robinette et al ; Van Dyke and Sutton ; Hassan and Edwards A duckweed lagoon with a standing crop of duckweed is harvested and placed fresh into a second lagoon containing a mixed size tilapia culture.

The pond is harvested twice weekly and the fish sorted into various groups for return to the lagoon or sale.

Under these circumstances the average yield of fish per hectare of lagoon is estimated at around 10 tons annually using only duckweed as the supplement to the naturally available fish feed Skillicorn et al In recent more detailed studies in Thailand, Hassan and Edwards have grown tilapia in static-water concrete tanks and fed them on two species of duckweed, Lemna perpusilla and Spirodela polyrrhiza at levels of 0, 25, 50 or 75g duckweed DM per kg wet weight of fish.

The Spirodela was poorly consumed whereas Lemna was rapidly ingested by fish. The growth rate and feed conversion rates for Lemna-fed tilapia are shown in Table 5.

Duckweed is a convenient feed for fish. Its attributes are: It can be readily grown locally often in waste ponds that are polluted. It can be fed fresh and since it floats, by judicious setting of the rates of application it may be totally used by fish. It is used very efficiently by fish such as tilapia and carp but other species might well cope with duckweed as a component of the diet since it is particularly low in fibre and high in protein when grown under ideal conditions.

It is relatively inexpensive to produce or may be regarded to have no cost where the opportunity costs of family labour are not taken into consideration. Use of duckweed in pig and poultry production. It seems reasonable to assume that village pigs, horses or ruminants could be fed on freshly harvested duckweed. For most applications with poultry, dried duckweed would be preferable.

Research with ducks has been surprisingly lacking but it could be expected that duckweed would provide an ideal wet supplement to any high energy diet. Research on using duckweed in the diets of domestic animals has been surprisingly scarce, perhaps because of the difficulties of growing sufficient duckweed under experimental conditions.

Thus there are major opportunities to grow duckweed as a crop for animal production purposes, but research on preparation and drying is needed to facilitate the uptake of the technology particularly in the poultry industry. The potential nutritional value of duckweed in poultry diets has long been recognised Lautner and Mueller ; Musaffarov ; Abdullaev Dehydrated duckweed has been used to replace alfalfa lucerne meal as a protein source in conventional poultry diets.

Recent studies have demonstrated that the growth of very young broiler chickens may be retarded with increasing levels of Lemna gibba dehydrated meal in the diet Haustein et al b whereas layer hens produced effectively Haustein et al a and older broiler birds had excellent growth when fed relatively high levels of Lemna gibba meal. Thus there is a need to be conservative when using Lemna protein meals with young birds.

Aquatic Plants and Flowers

Washington, B. Wastewaters amenable to aquaculture treatment are inventoried and constraints which are limiting to more widespread application of aquaculture technology are assessed. The report concludes that aquaculture is a viable technology which can be used to treat many biologically treatable wastewaters. Potential benefits cannot be fully realized under current regulatory restrictions and technological constraints. The study suggests that wider dissemination of technical information, coordinated efforts to reconsider regulations, and additional research will benefit future applications of this technology. Ray Dinges, Henry R. Thacker, B.

Name required. Mail will not be published required. Food chains help us understand the connection between living things. In this food chain, energy flows from the grass producer to the deer primary consumer to the tiger secondary consumer. A pond ecosystem is represented in the diagram below Click here to view. In a forest ecosystem, grass is eaten by a deer, which in turn is eaten by a tiger. Share Your Word File Some aquatic plants are valuable in providing shade, hiding places for small fish, habitat for some aquatic insects and animals, as well as being a food source for some fish and animals.


Section 3 addresses the important issues in duckweed-fed fish production. The economics of er plants, or macrophytes, although they are often mistaken for algae. The family of the plot, and spraying a fertilizer solution on the duckweed mat. Efficient Carp, Ctenopharyngodon idella, Fed Elodea, Egeria densa." 7Tan-.


The Best Oxygenating Pond Plants (Top 8 Plant Species)

Skip to main content Skip to table of contents. Advertisement Hide. This service is more advanced with JavaScript available. Vegetation of inland waters. Editors view affiliations J.

Figure Littoral zone of Lake Newnan, Florida, July Previous editions of this guide were edited and designed by Allison Slavick, ww. Excellent editorial changes were added to this edition by Mike D.

In this activity, students explore the idea of food webs by making their own food web of a pond ecosystem. A food web can be described as a "who eats whom" diagram that shows the complex feeding relationships in an ecosystem. Students are given a set of cards with organisms on them. Bullfrogs grow large, too. Get it as soon as Tue, Feb

Lesson 3 extends their thinking from land to aquatic environments.

Vegetation of inland waters

Generations ago, people believed that anything green that was not considered an animal was a plant. In , a modern classification of plants was proposed by plant ecologist, Robert Whittaker, who gave five divisions: monera single-celled organism , protoctista mainly fresh water aquatic plants , fungi ascomycete, basidiomycete, chytria and penicillium conidiophor , plantae algae, all seaweed and kelp and animalia sponge, jellyfish, insect, etc. The role of aquatic plants is so essential for survival that they belong to two divisions: Plantae and Protoctista.

Name required. Mail will not be published required. In a pond ecosystem, the primary consumers are tadpole larvae of frogs, fishes and other aquatic animals which consume green plants and algae as their food.

pond food web

Aquatic ecosystems are expected to receive Ag 0 and Ag 2 S nanoparticles NPs through anthropogenic waste streams. The speciation of silver in Ag-NPs affects their fate in ecosystems, but its influence on interactions with aquatic plants is still unclear. The silver distribution in duckweed roots was visualized using synchrotron-based micro X-ray fluorescence XRF mapping and Ag speciation was determined using extended X-ray absorption fine structure EXAFS spectroscopy. By 24 h after exposure, all three forms of silver had accumulated on and partially in the roots regardless of the form of Ag exposed to the plants. Once associated with duckweed tissue, Ag 0 -NPs had transformed primarily into silver sulfide and silver thiol species. This suggests that plant defenses were active within or at the root surface.

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Answer the following questions, while reading the article. 1) What is Follow the key: Duckweed, Elodea, and Algae: Why Are They Important? Answer the.

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They include herbivores (animals that eat plants), carnivores (animals that eat other animals) Duckweed, Elodea, and Algae: Why Are They Important? Why should you add To find the answers, do some research in the.

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