The Effects of Drought on Aquatic Biodiversity

Topics: Standard deviation, Aquatic ecosystem, Life Pages: 5 (989 words) Published: September 13, 2013
Faith Cruda

Student number 332289

The effects of drought on Aquatic Biodiversity


Prolonged drought is one of the biggest environmental predicaments we encounter periodically. Australia is a well known dry continent and is potentiated by low yearly rainfall. As drought progresses, water evaporation increases sharply which then decreases water levels on dams, rivers and creeks threatening the flora and fauna present in those ecosystem. “The augment in water temperature may also result in diminishing levels of Oxygen present in water and as a consequence the salinity of the water increases and could do an immense destruction on fish species” (Bond, , Lake, Arthington,2008 p.14). The “ increase in water temperature may also result in nutrient build up which will intensify algal growth and makes the water poisonous not only to the fish species but also to the livestock and domestic animals in the surrounding area” (Boulton,2003 p 1173). The study on the effects of increased frequency and prolonged period of drought was conducted in order to establish the impact and its adverse effect on living organisms.

Purpose: To determine the effects of a droughts duration and frequency upon aquatic flora and fauna.

Hypothesis: It is believed that as drought progresses, the rate at which aquatic living organisms propagate decreases.


The data from different ten wetland systems was analysed. These wetland systems has experienced drought in 1950, 2005 and 2008. Each event occurred for the duration of nine, eighteen and ten months respectively refer to figure 1.1 “ Invertebrate richness”. The mean, standard deviation, standard error and variance of the available data given were calculated using the formulas shown in figure 1.0. The data available was also plotted into a line graph (refer to figure 1.2 “The number of invertebrate present in each wetland with year”) to easily determine the significant effect of prolonged drought on number of invertebrates. The data in the table was colour-coded to match the graph. Once the mean, variance, standard deviation, and standard error was calculated the answers were placed on a table and then a bar graph was established where the average was plotted against the year in order to determine the extent of damage drought could do to living flora and fauna present in those ten wetland systems. The Bar graph was a useful tool to compare the trend in averages of the number of invertebrate per annum.

Figure 1.0 Formulas for calculating the Mean, Variance, Standard Deviation and Standard Error



Figure 1.1 Invertebrate Richness

|WETLAND |1950 |2005 |2008 | |1 |30 |25 |15 | |2 |25 |20 |10 | |3 |15 |15 |7 | |4 |18 |12 |5 | |5 |14 |12 |7 | |6 |16 |10 |4 | |7 |24 |16 |5 | |8 |33 |25 |15 | |9 |12...

References: Bond, N.R., Lake, P.S, Arthington, A.H. (2008) The impacts of drought on freshwater ecosystem: an Australian perspective. Hydrobiologia,600, 3-16.
Boulton, A.J. (2003). Parallels and contrast in the effects of drought on stream macro invertebrate assemblages. Freshwater Biology, 48, 173-1185.
Where X= total number of invertebrate present in a given year minus the mean gathered per year and N=total number of wetland system used
Where the square root of the given variance each year is calculated.
Where X= the average number of invertebrate present in a given year and N=the number of wetland system used.
Where S=total number of standard deviation each year and N= is the square root of the number of wetland system used.
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