1 Aquatic Science Unit 2 Water Quality and Water Pollution
2 What is a healthy water body? In your own words, take a moment to describe what you believe are some of the characteristics of a healthy stream or lake.
3 Is this a healthy water body?
4 Is this?
5 What about this?
6 Or this?
7 Or this?
8 Or this?
9 Or this?
14 This river in China?
15 This river in Peru?
20 What affects Water Quality in Streams and Lakes? We measure water quality using four general categories Water chemistry Sediment chemistry Physical habitat Biological community
21 Water Chemistry Historically, water chemistry has been the primary method for measuring water quality in streams and lakes. Water chemistry is measured using both physical and chemical parameters.
22 Physical water quality indicators The most common physical water quality indicators are: Dissolved Oxygen (DO) Temperature ph
23 Chemical indicators of water quality Some common chemical indicators of water quality are: nutrients ammonia chloride sulfates suspended solids
24 Sediment chemistry Water quality does not depend on the water alone. Pollution can also contaminate the sediments on the bottom of lakes and streams. Some common pollutants that contaminate sediments include Heavy metals PCBs
25 Physical habitat Healthy streams and lakes require more than just clean water and clean sediments. Physical habitats are necessary for the health of organisms Some important physical habitat criteria include: shade sunlight shelter stream flow sediments
26 What physical habitat characteristics are missing here?
27 Biological communities Finally, healthy streams and lakes require healthy biological communities. Some issues that affect biological communities include: habitat destruction invasive species predator removal over fishing
28 What is the difference between pollution and pollutants? Pollution is defined as the man-made alteration of the chemical, physical, or biological integrity of water. Pollution is caused by activities that affect overall water quality. Some examples of pollution include: damming of rivers channelization and levee construction for flood control dumping of industrial waste.
29 Pollution vs pollutants (cont) A pollutant is any substance that can cause pollution. Examples of pollutants include: nutrients heavy metals chlorine pesticides waterborne diseases
30 Pollutant concentration vs pollutant loading Most water quality measurement is based on pollutant concentration and is measured in units such as parts per million (ppm) But pollutant concentration doesn t tell us the total amount of pollution entering a water body. We measure the total quantity of pollution entering a water body using pollutant load in units such as pounds per day.
31 Water Pollution Sources Pollution comes from two general categories of sources. Point source pollution comes from a specific location such as a discharge pipe from a factory Nonpoint source pollution does not have a single source of origin but comes from dispersed sources such as fertilizer runoff from lawns.
32 Point source pollution Point sources Located at specific places Easy to identify, monitor, and regulate
33 Nonpoint source pollution Nonpoint sources Broad, diffuse areas Difficult to identify and control Expensive to clean up What could this farmer do to prevent this problem?
34 Common point sources of pollution Municipal wastewater treatment plants Factories Sewage bypasses Oil rigs and refineries
35 Common nonpoint sources of pollution Agriculture (largest single source of nonpoint pollution) Sediment eroded from farmlands Fertilizers and pesticides Bacteria from livestock and food processing wastes Mining Golf courses, lawns, and parking lots
36 Pollutant Types: Nutrients Nutrients, primarily nitrogen and phosphorus are essential for plant growth but can become pollutants when provided in excess. The addition of nutrients from human activities is called cultural eutrophication.
37 The process of nitrification Ammonia, a toxic chemical found in animal waste is broken down through a process called nitrification Ammonia is oxidized into the chemical nitrite (NO 2- ) by special bacteria called Nitrosomonas Nitrite, which is still toxic to fish is further oxidized into nitrate (NO 3- ) by another specialized bacteria called Nitrobacter. Nitrate is relatively non-toxic, but is still considered a pollutant because it is a major plant nutrient.
38 The Aquatic Nitrogen Cycle (nitrification)
39 Algal blooms When too many nutrients are added to ponds and lakes, algal blooms can occur. During the day, the algae produce much oxygen through photosynthesis so DO levels increase But during the night, plant respiration by the algae consumes all the oxygen. So DO levels drop to lethal levels for fish and marine animals.
40 Algal blooms
41 Harmful Algal Blooms A harmful algal bloom is one that produces toxins that harm plants and animals Fish kills from the golden algae Prymnesium parvum have occurred throughout Texas.
42 Oxygen Demanding Substances Organic pollution such as raw sewage, food processing waste, and cow manure can cause decreases in DO The organisms that decompose organic waste actually consume the oxygen through respiration The amount of oxygen required to decompose organic materials is called biochemical oxygen demand (BOD)
43 Recovery of polluted streams and lakes Streams can cleanse themselves of many pollutants through dilution and decomposition if we do not overload them or reduce their flows. Lakes are less effective at diluting pollutants than streams because: Lakes have stratified layers with little vertical mixing. Lakes have little or no water flow
44 Dilution and Decay of Degradable, Oxygen-Demanding Wastes in a Stream
45 Active Figure: Stream pollution
46 Water Quality as Measured by Dissolved Oxygen Content in Parts per Million
47 Water temperature Each aquatic species has an optimum temperature range at which it functions best Elevated temperatures reduce the solubility of DO which decrease the DO in a water body Most fish and other aquatic species in Texas are adapted to warm water (and lower DO levels) That s why Texas is famous for bass and not trout.
48 Effects of water temperature on metabolism Higher water temperatures increase metabolism and respiration which increases the demand for oxygen by fish So fish need more oxygen in warmer water but warm water has less DO!
49 Sources of water temperature pollution Clearing of bank vegetation (riparian zones) which provide shade for streams. This is caused by agriculture, logging, and suburban development. Discharges from power plants and other industries Especially nuclear power plants that generate enormous quantities of hot water in their turbines Global warming and climate change
50 Water ph (Acidity and Alkalinity) ph is not a pollutant but a measure of how acidic or basic a body of water is. ph from 0.0 to 6.9 is acidic ph of 7.0 is neutral ph from 7.1 to 14.0 is basic Most aquatic organisms do best in water that is neither highly acidic or highly basic Few organisms can live in water more acidic than ph of 5.0 or more basic than ph of 9.0
51 What affects the ph of water bodies? Geology: The underlying rock and soil type in a watershed affect water ph. The limestone in Texas raises the ph when dissolved. Photosynthesis by aquatic plants removes CO 2 from the water which raises the ph. Human activities. Mining, acid rain from air pollution, and dumping of industrial waste can all affect ph
52 Salinity and dissolved salts Water quality is affected by elevated salinity and other dissolved salts This is most common in the coastal regions and arid parts of the state. Most freshwater fish do not tolerate brackish water (water that is slightly salty) Salinity in a watershed is often increased by irrigation and oil drilling which brings salty water to the surface
53 Suspended solids Suspended solids is the common term used for mud, clay, and other minerals that are suspended in water Construction, erosion from farmlands, and surface mining cause increases in suspended solids which makes water look muddy or silty
54 Why are suspended solids a concern? They block light which prevents photosynthesis by aquatic plants Fish can t feed as easily when they can t see in muddy water Sediments settle on the bottom covering aquatic habitats and food sources
55 Bacteria and infectious diseases While most bacteria are helpful or benign, harmful disease-causing bacteria can be a form of water pollution Fecal coliform bacteria (E. coli) is a widely-used indicator bacteria to measure water quality Fecal coliform bacteria are found in the intestines of humans and animals. Their presence may indicate the presence of other harmful bacteria found in raw sewage.
56 Toxic Substances Substances are considered toxic when they can kill organisms directly. Acute toxicity results when high concentrations of a substance cause immediate danger or death. Chronic toxicity refers to the long term effects of sublethal levels of a substance which can alter growth and reproduction of an organism.
57 Toxic Substances continued Ammonia is one of the most common toxic aquatic pollutants. Ammonia enters the water from industrial and municipal wastewater and agricultural and urban runoff (especially raw sewage and manure). Ammonia is extremely toxic to fish and is the most common reason why fish die in aquariums.
58 Other toxic pollutants Chlorine is another common toxic substance. Chlorine is used to treat drinking water and is commonly used in industry. Pesticides are another common toxic pollutant. The class of pesticides called organophosphates are the most toxic to fish. Heavy metals such as arsenic, cadmium, and mercury are also highly toxic in the environment and commonly discharged by industry.
59 ABC Video: MTBE pollution
60 Sedimentation and Sediments Sediment is a mixture of loose particles (sand, silt, and clay) that covers the bottom of streams and rivers. Sediment is removed by fast moving streams and rivers and deposited in slower moving rivers and lakes when the water flow is no longer fast enough to keep the sediment suspended. Sediment buildup (Sedimentation) can cause problems for aquatic organisms because food sources can become covered with sediment.
61 Sediment chemistry In addition to the effects of sediment on the aquatic environment, sediment also collects toxic chemicals which bind with the sediment in the water and settle out on the bottom. Even when the water around industrial sites is cleaned up and the source of pollutants is stopped, toxic sediments around the sites may persist for decades. These types of pollutants are called legacy pollutants.
62 Physical Habitat Alteration Changes in the physical habitat of a stream often affect the biological communities regardless of the water quality. Channelization is one of the major reasons why streams and rivers are degraded. Channelization is the straightening of a stream or river by removing its natural meanders and vegetation. Channelized streams and rivers are often nearly lifeless no matter what the water quality.
63 Examples of Channelization - Texas
65 Los Angeles
67 Effects of channelization Water temperature increase. The removal of vegetation causes water temperatures to increase. Increased turbidity. Erosion of exposed banks increases turbidity (soil and sediment in the water). Changes in stream flow. Straightening of streams and rivers changes the water flow and prevents water from spreading out into floodplains.
68 Indicator organisms Biological communities (fish and invertebrates) can be used to evaluate the health of water bodies. Fish and invertebrates are placed into categories based on their tolerance to pollution and are used as indicator organisms.
69 Indicator organisms Organisms are grouped into 3 categories Intolerant (sensitive to pollution Intermediate (moderately tolerant to pollution) Tolerant (most tolerant to degraded habitat and water quality. The type and number of organisms present can tell a lot about a stream. The presence of intolerant organisms generally means that little or no pollution exists.