Freshwater is a limited resource on earth. Only 3% of the world’s water is fresh – the rest is salt or brackish. Of this fresh water, 75% is locked up in the earth’s ice caps, 24% is found in aquifers in porous rocks and 1% is present in lakes and rivers. Of this tiny amount, much is concentrated in small areas – the Great Lakes of North America, the Caspian Sea and Lake Baikal. For the majority of people around the world, acquiring life’s basic resource is difficult. Water is needed:
In the home for drinking, cooking and washing;
In industry as a coolant, in food manufacturing, brewing and distilling;
In agriculture for irrigation and livestock;
For it’s amenity value;
As a habitat for plants, invertebrates, birds and mammals.
As a result of these uses, water is often polluted and under the Water Framework Directive (WFD) it is now a requirement for all water bodies to be of ‘good’ status and for continuous monitoring to be undertaken. Both chemical and biological monitoring methods are used within the WFD. You can find out more about freshwater Ecosystems in last weeks lecture, including information on key characteristics of these systems and indicators of freshwater pollution. Today we will look at some biological indicators to assess water quality in three different stream environments. We will collect water samples from 2 different parts of the stream running through Blackford Glen near SRUC. One location will be within the local nature reserve (LNR), and the other will be downstream of the LNR and a council depot. We will also assess the water quality of stream water collected from a nearby stream into which large levels of agricultural run-off accumulate. The management plan for Blackford Glen and a map of the site are also posted on Moodle.
The aims of this exercise are to determine the effects of aquatic pollution on the biological water quality of freshwater streams, and to identify levels of aquatic pollution using biological indicators.
To achieve these aims we will:
Assess biological water quality in two different locations within the Braid Burn at Blackford Glen, and in stream water gathered from a nearby agricultural catchment.
Determine whether biological water quality varies between these points and suggest possible causes of any differences found.
Biotic data collection:
The Scottish Environment Protection Agency standardises this type of data collection by using a 3- minute kick sample. It has been shown that this provides the highest proportion of species present for the least time actually spent sampling. It is essential that all of the microhabitats in the stream be sampled within this time, such as in fine sediment, amongst larger pebbles, in weeds, and where leaves have accumulated. You are required to carry out kick samples at two locations within Blackford Glen, one from the Braid Burn above the Council Depot (within the LNR) and one from the Braid Burn below the council depot (downstream of the LNR). You will be provided with a sample taken from the nearby agricultural catchment on the morning of the fieldtrip. To carry out your kick samples you should follow these key steps:
Divide into approximately 6 groups with 6 people per group – making sure at least one person in the group has wellies!. Each group should take two sampling jars with lids and a kick sampling sweep net
Walk to the location at which you will collect your kick-sample. Within your group perform one kick sample per group at each of the two locations (so your group of 5-6 students just needs to do one kick sample below the depot and one above the depot)
To carry out your kick samples select an appropriate area of the stream, start a stop watch (with one group member keeping time) and walk out into the stream. Place the open mouth of the net so it faces towards the flow of the water with the base of the net on the stream bed. Now kick and dislodge stones at the mouth of the net. Try not to fill your net with stones. Every 30 second or so move the net to a different type of stream microhabitat and continue kicking. Include all the main habitat types with an even amount of time given to each – fast riffles/shallow water/slow water/vegetated areas (diverse sample). In heavily vegetated areas sweep the net for allocated time. Stop sampling when three minutes is up and empty the net into your water sampling jar, try to remove or rinse out all the invertebrates in your net into the jar.
Return to the Lab with your samples. At the start of the lab we will empty your samples into white trays with some river water. Remember which sample your tray relates to (above or below the depot) and mark this on your sample sheet.
Within your group, use the magnifying lens and keys provided to identify as far as you are able, how many of each species shown in the table below occur in your tray. You will also identify the species and abundance of species in the agricultural catchment stream water sample collected earlier.
For this assessment you are required to complete a pro-forma (see Moodle) based on the field visit and lab work you carried out on the day. You need to complete each section of the form based on the fieldwork you carried out and the lab work on identifying different categories of species within the water samples. Use the summary data from the fieldwork/lab that I will circulate after the lab to insert into the appropriate sections of the form, and use the lecture notes and wider information/background reading to complete the other sections.
The BMWP score uses indicator species to show water quality. Species that need lots of dissolved oxygen have a high score. Species that need a low concentration of dissolved oxygen have a low score. If you observed a family then record for that family the indicated score and sum all the scores for your sample.
3) Using the BMWP scoring sheet above calculate the total BMWP score for each stream as a group and decide which stream is of better water quality.
Based on the lab work of the whole class we will end up with two tables, one showing the species found across all stream water samples and their relative abundance (this is why you count the number of each species) and a table calculating the average BMWP for each sample location (this will look like the blank table below). I will accumulate all of your data together and produce these tables. Once these are done I will circulate them to the class and you can include them in your report for this assignment.