Water Hyacinth Eichhornia Crassipes Biology Essay

Water jacinth Eichhornia crassipes is an invasive aquatic works that is foreign to many of the ecosystems in which it has established itself. It proliferates in waterways and signifiers free drifting mats on top of the waterway. If non controlled, H2O jacinth will cover the entireness of the waterway. This significantly reduces the flow of H2O, blocks sunlight from perforating the H2O ‘s surface and starves the H2O of O doing deductions for the other organisms life in the waterways, such as the fish as they do n’t have plenty O because the bed on top of the H2O does n’t let the visible radiation to perforate through to let the underneath works flora to photosynthesis and give off O in which the fish usage for endurance. It is besides a menace to human wellness in that it houses insects transporting diseases such as malaria and contaminates the H2O beginning through decomposition doing it unfit for human ingestion. Water jacinth is regarded as South Africa ‘s most detrimental aquatic weed.

One effectual method for the obliteration of H2O jacinth has been the debut of H2O jacinth weevils ( neochetina eichhorniae and neochetina bruchi ) which provender and proliferate on the H2O jacinth, cut downing its generative rate and, provided conditions are optimum, finally doing the decease of the weed.

Research inquiry

The effectivity of the H2O hyacinth weevil as a biological control on the proliferation of H2O jacinth will be influenced by a figure of factors. The inquiry that I hope that my research will reply is “ To what extent does sunlight increase the activity and reproduction of the H2O jacinth weevils and consequence in more harm to the H2O jacinth works through increased activity and reproduction? ”


My hypothesis throughout this probe is that the weevils will make greater activity on H2O jacinth workss that are grown in full sunshine.


My purpose in this probe will be to find whether the weevils are more active and more generative, thereby bring downing more harm, when introduced onto H2O jacinth workss grown in full sunshine and resultant higher temperatures than when introduced onto H2O jacinth workss grown in lower visible radiation strengths and resultant lower temperatures.

Importance of the research

The research is of import because it will supply insight into the interrelatedness between climatic conditions and the biological control of H2O jacinth trough the debut of weevils. This will assist conservationists to measure whether biological control of H2O jacinth through the debut of H2O jacinth weevils is the most effectual method of obliteration of this works in certain predominating conditions conditions or whether alternate methods, such as mechanical or chemical methods, would be more effectual in protecting the ecosystem.

Literature reappraisal

The proliferation of H2O jacinth has an highly detrimental impact in many of the aquatic waterways in South Africa. For illustration it contributes to:

the spread of deathly diseases such as malaria,

the interruption down of ecosystems which adversely impacts certain industries, such as fishing, and

the toxic condition of H2O beginnings as it rots when morbid or dead.

Whilst there are alternate methods of commanding the proliferation of the weed, biological control is the safest option available from an environmental position. Every attempt should be made to understand the impact of climatic conditions on the efficaciousness of the available biological options. The research set out below will corroborate that conditions conditions, peculiarly the impact of sunshine, has a important impact on the choice of a biological solution as opposed to a mechanical or chemical solution.

Water jacinth weevils weaken the works in their eating and reproduction activities. This makes the works vulnerable to other upwind elements such as H2O motion ( moving ridges ) and wind which automatically break down the works. Weather conditions that encourage the activity ( feeding ) and reproduction of the weevils improve the opportunities of their effectivity in commanding H2O jacinth.

Successful biological control of H2O jacinth through the usage of the weevils has been limited to tropical and/or sub-tropical climes.

In 1991, weevils were released in the New Years Dam in the Eastern Cape, South Africa. Three old ages subsequently, the H2O hyacinth population had reduced by about 80 % . However, in the Western Cape, the debut of these insects has non been as successful and research workers have concluded that the insects are non good adapted to a Mediterranean clime.

Many of the worst H2O hyacinth countries in South Africa occur at high heights that experience cold winters and frequent hoars. Research has concluded that one type of H2O jacinth weevil ( Neochetina eichhorniae ) is much less effectual in those conditions. This is due to the fact that the active turning season of the workss, and hence the weevils, is limited to six months. The other type of weevil ( Neochetina bruchi ) is much more cold tolerant and play an of import function in hyacinth control in colder parts.

The seasons play an of import function in the activity of the weevils. Research has shown that the harm that the weevils inflict in heightened during the summer months and reduces during the fall and winter months.

Adult H2O jacinth weevils are nocturnal animals i.e. they are less active during the twenty-four hours and more active during the dark. This could take to the decision that the weevils would be less active in environments where sunshine is present and more active where there are sustained periods of darkness.

However, the form of the H2O jacinth works plays a function in cut downing the impact of this. The works is a mat that blocks out the sunshine thereby cut downing the difference between nocturnal and diurnal activity.

Weevils are much more productive on healthy workss. The H2O hyacinth thrives in sunlit and warm conditions and growing is most rapid in the temperature scope of 22- 35 grades celcius. A colder or darker environment consequences in less healthy workss and a less effectual environment for the weevils to proliferate.

Water jacinth weevils are an environmentally friendly method of eliminating the most environmentally unfriendly aquatic weed, the H2O jacinth. However, climatic conditions, specifically sunlight and temperature, play an of import function in the effectivity of the weevils as a control agent. In measuring whether to utilize the weevils as a step to eliminate the weevils, the predominating conditions conditions need to be considered. Sustained periods of cold conditions and/or darkness will do the weevils to be hibernating and non reproduce. This will hold a significantly inauspicious consequence on their effectivity as control agents. Warm conditions and/or sunlight increase the rate of reproduction and eating activity and increase their effectivity.


The experiment will be conducted in nine containers – three containers at each of the three different Stationss that will be exposed to different light strengths. The containers will be the containers for each single H2O jacinth works for the continuance of the probe. The containers will all be precisely the same. Every constituent that the containers will envelop will be fixed variables and these variables are:

80 liters of H2O

24g of 7:1:3 fertilizer

8g of Fe chelates

10 weevils

A H2O jacinth works, all of the same initial works size

Areas with different light strengths will be set up to retroflex countries with different light strengths found in nature. To retroflex the different visible radiation strengths, shade fabric such as that used for covering auto parking countries will be used. Two big constructions ( one metre in breadth by one metre in length and by one metre in tallness ) will be constructed. These two buildings will be the constructions in which the shadiness fabric will be positioned over to copy different light strengths. The shadiness fabric will cover every gap so that no visible radiation can come in the building enveloping the H2O jacinth workss without perforating through the shadiness fabric and hence making different light strengths. The constituents required in piecing one of the buildings to place shadow fabric over will be:

8 metres of wood


Tape or gum

There will be three different Stationss, each station acquiring exposed to a different light strength. In each station there will be three containers incorporating the above constituents. Three containers are used to guarantee that the probe is dependable and accurate consequences and to extinguish any opportunity of the research stuffs going tainted.

The first station will hold three containers exposed to full sunshine and will hold no shadiness fabric to set the light strength.

The 2nd station will hold three containers exposed to full sunshine but will be enclosed in one of the antecedently discussed buildings and will hold a individual bed of shadiness fabric covering the full enclosure, so no visible radiation can come in the building enveloping the three containers of H2O jacinth workss without perforating through a individual bed of shade fabric. Therefore the light strength will be less than the light strength of the first station that is exposed to full sunshine.

And the 3rd station will hold three containers and will be setup in the same manner as the 2nd station ( exposed to full sunshine and enclosed in a building and shadow fabric covering the full enclosure ) with the lone difference being that alternatively of a individual bed of shade fabrics like at station two the 3rd station with have a dual bed of shade fabric hence decreasing the light strength even more than station two.

In garnering the information, one time all the setup has been setup, I will tag off a specific foliage on each specimen of H2O jacinth works in each single container. The pronounced foliage on each works will be about equal in surface country and will be found in the same place on each works to do certain all the marked foliages are of the same estimated age. The pronounced foliage on each works will be from the newest batch of foliages produced by the works because this will be the greatest country of activity of the weevils as the new foliages contain higher volumes of foods for the weevils.

The information that will be collected will be the figure of feeding cicatrixs caused by the weevils eating the H2O jacinth works. The information will be collected by numbering the eating cicatrixs on the foliage blade, from the leafstalk to the vertex ( excepting the root ) . The information will be collected from a marked off foliage of the most late bloomed set of foliages of each H2O jacinth works. The information will be cod in the forenoon before school twice a hebdomad over a continuance of eight hebdomads. The information will hence be collected 16 times throughout the ain undertaking.

The information will be analysed during the probe by infixing the readings of “ the figure of feeding cicatrixs on a specifically marked foliage ” into a table format every clip informations is collected, which will be twice a hebdomad for eight hebdomads. Each tabular array will hold a row for each single H2O jacinth works ‘s reading over the period of probe


Once the probe period is over I will utilize the tabular array in which all my consequences from every clip I collected my informations is shown and by looking at my consequences I have gathered during the probe period, I will expose my consequences on a line graph. The graph will hold an x-axis header of the informations aggregation figure ( 1 to 16, because if I collect my informations twice a hebdomad for eight hebdomads, 16 sets of informations will be collected ) , and will hold a y-axis of the figure of feeding cicatrixs on a specifically pronounced foliage. All three Stationss ‘ consequences will be displayed on one line graph and the three Stationss ‘ consequences line will be in a different coloring material to the other two Stationss ‘ consequences. This will give a clear position on how the figure of feeding cicatrixs differed from workss that were exposed to different light strengths and will therefore turn out my hypothesis to be true or false. During the full experiment I will be taking exposure of my H2O jacinth workss to demo the progressive addition in feeding cicatrixs over the eight hebdomads. The grounds will be photographed on a regular footing and included in the analysis. I will take a exposure of each single foliage from which I am numbering the figure of feeding cicatrixs on and will make this for all nine workss every clip I collect my informations ( twice a hebdomad for eight hebdomads ) .

The temperature will be recorded every bit good utilizing a thermometer to acquire a reading of the H2O temperature, as the different visible radiation strengths will hold an impact on the H2O temperature.

There are a figure of ethical issues that will be considered in carry oning the probe and showing the consequences derived at that place from, inter alia:

The decisions reached will be indifferent and will be presented in an unambiguous mode

All inputs and mentions will be recorded and referenced

Other beings in the immediate locality of the probe will non be harmed or become infested

The weevils will be disposed of at the terminal of the probe in a responsible and humanist mode