Published: 2019-05-15 10:00:00
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Dissolved oxygen refers to the amount of gaseous oxygen dissolve in water. Oxygen enters the water through the process of diffusion from the atmosphere (direct absorption), through aeration by rapid movement as well as photosynthesis by aquatic plants. Running water contains more dissolved oxygen than still water. Additionally, oxygen dissolves easier in cooler water than in warmer water. Extremely too high or too low levels of dissolved oxygen can compromise on water quality and also harm aquatic life. Factors that affect the amount of dissolved oxygen levels include water temperature and volume of moving water.

Merits of dissolved oxygen in water.

Enhances quality of water

Adequate dissolved oxygen is important is good for water quality and necessary to all forms of life. It essentially makes drinking water taste better.

Aquatic life support

Dissolved oxygen is essential for the survival and maintenance of aquatic life. This is because the levels of dissolved oxygen determine the number and types of organisms living in water masses. Microbes such as fungi and bacteria require dissolved oxygen. These organisms decompose organic material at the sea bed. Microbial decomposition is an important contributor to nutrient recycling. Oxygen levels that drop below 5.0mg/L can lead to stress in aquatic life.

New York safe fishing standard for dissolved oxygen?

The NYS Water Quality Standard for dissolved oxygen is 4 mg/L for most of the Hudson River Estuary except in Haverstraw Bay which is 3mg/L. The generally accepted minimum amount of DO that will support a large population of various fishes varies from 4 to 5 mg/l.

Relationship between oxygen levels and time of year in the Hudson River

There is an inverse relationship between temperature and the average dissolved oxygen levels. This implies that the relationship between the average oxygen levels and the time of year in inverse. Average dissolved oxygen levels are highest when the temperatures are lowest and are lowest when the temperatures are highest.


Ideally, warm water increases the molecular activity and pushes the oxygen molecules out of the spaces between the moving water molecules. This implies that when temperatures increase, the amount of dissolved oxygen decreases thus the months having high temperatures will experience decreased oxygen levels.


Bloomberg, M. R. Stickland, H. & Carter, M. 2012). The State of the Harbor. Available at http://www.nyc.gov/html/dep/pdf/hwqs2012.pdf>. NYC

NYSDEC (1985). Use Attainability Analysis of the New York Harbor Complex. New York State Department of Environmental Conservation, Division of Water


Question 1

The best way to make this data comparable is by computing the average of the dissolved oxygen data values for each month and comparing it alongside with the temperature values.

Question 2

The type of graph to use is a column bar graph.


This is because a column bar graph helps to clearly represent the information data conspicuously in a manner that makes data simple to analysis. Drawing a trend line also makes it possible to see how the direction and variation of the data.

Question 3

The best statistics to use is the average. This is because it will be easier to compare the average values of the dissolved oxygen values with the NYC standards and hence establish how suitable the data fits for analysis.

Question 4

Number transformations that can help make the data more relevant.

The best number transformation to use is percentages. This is because it will help analyze the percentage of months that have dissolved oxygen value above the NYC standards and hence get to know the particulars of each month.


Question 1

In the excel sheet attached;

Chart 1 describes, it shows the column bar chart showing the variation of temperature against the average dissolved oxygen values for the 12 months in the year.

Question 2

General trends:

From this graph, it is clear that the month with the highest average dissolved oxygen value is March (11.18) followed by February (11.08) while the month with the highest temperature was July of 78.

The months with the least average dissolved oxygen value are August (5.45) and September (5.65) respectively. January had the least average temperature of 32.

The general trend of the data shows that the amount of dissolved oxygen tends to increase from the October all the way to February. From April, the amount of dissolved oxygen can be seen to decline. With temperature, it can be seen that the temperature decreases from July all the way to December and rises from January all the way to July. When temperature is highest, the average dissolved oxygen is least and vice versa. Thus the average temperature has an inverse relationship with the average dissolved oxygen.

Question 3

Statistics describing the data




Question 4

Explanation of statistics


The use of averages was the most suitable method of analyzing the data. Getting the average on dissolved oxygen levels and comparing it with the average on temperature makes analysis more easier. The general trend in the average of temperature is that temperature can be seen to rise from January onwards till August after which it declines all the way to the month of January after which it starts another cycle of increasing.

Dissolved oxygen can be seen to decrease from the month of January all the way to the month of August after which it starts rising all the way to December.

The general trend is that the level of dissolved oxygen is least when the temperatures are highest and are maximum when the temperatures are at their lowest point.


Temperature can be seen to have the highest average of 78 in the month of July. On the other hand, the average dissolved oxygen level was highest in the month of March with 11.18.


Temperature can be seen to be lowest in the month of January with an average of 32. The average dissolved oxygen level was least in the month of August 5.45.

Question 5

Number transformations

Use of percentages.


Rank. (Highest to Lowest) and vice versa.

Question 6

Explanation on how the data transformations help put your numerical data in context.


The month with the highest average was August with 5.64% of the total average dissolved oxygen levels. The month with the lowest amount of dissolved oxygen levels was March with 11.57% of the total amount of dissolved oxygen levels.

The total number of mouths that had a percentage above the NYC standard represented about


Question 1

Hypothesis testing

There is a relationship between the dissolved oxygen levels and temperature. Hence;

Ho; U0 - There is no relationship between the dissolved oxygen levels and temperature.

H1; U1- There is a significant relationship between the dissolved oxygen levels and temperature.

Question 2

Did the data analysis support your hypothesis?

Yes. Results from the data analysis show that dissolved oxygen levels vary with temperature. There is a strong negative correlations between dissolved oxygen levels and temperature.

Which method was the most useful in determining your conclusions? Why?

The data analysis was more useful in drawing conclusions. Data analysis availed more information in addition to establishing the relationship between the levels of dissolved oxygen as well as the temperatures.


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