Berlin 2025 - Aquatic Ecology - Day 2

1 Aim and learning objectives

The overarching aim of this day is to introduce you to established biomonitoring methods

By the end of the practical you will:

• Have confidence collecting macroinvertebrates using qualitative and quantitative sampling methods;

• Understand how microhabitat heterogeneity can influence macroinvertebrate abundance and composition;

• Appreciate how urbanization can alter macroinvertebrate communities and how biotic indices can be used to assess anthropogenic pressures on river ecosystems

2 Study sites

We will visit the River Panke at Karow (site 2 from day 1; Figure 2) and Pank Terrace (Figure 1), also on the River Panke.

Fig. 1: Urban section of the River Panke at Panke Terrace (Screen capture from Google Earth)

Fig. 2: Map displaying all the points of interest for the day two activites

3 Field activities

3.1 Semi-quantitative approach

Macroinvertebrate samples will be collected using a standard sampling approach - the 3-min kick sample. You should aim to sample across a 10 – 20 m reach and target microhabitats relative to the proportion of the total reach they represent (Figure 3).

Fig. 3: Example of how to distribute the time between habitats

You need to conduct a manual search (1-min) to check for surface dwelling animals (before kicking) and animals attached to large stones, banks or marginal plants (after kicking). For the kick sampling a member of the group should carefully enter the stream (downstream of the sampling section), then moving up stream disturb the substrate with their feet to dislodge any attached invertebrates, which are subsequently collected in the sample net.

Tip

Don’t kick too vigorously otherwise you will end up with a net full of sediment!

After 3 mins the content of the net should be emptied into a white tray (filled with water) for your group to examine. If there is a significant amount of sediment in the sample decant into a sieve first and then spoon smaller amounts of sediment into the tray, this will make it easier to spot organisms.

Tip

Leave the tray to settle for about a minute as it is easier to identify the animals once you see them moving. Also you can Use forceps or a pipette to move different groups of animals into holding trays to make identification easier.

We are going to use the Extended River Fly key (ERF), this has been developed for rapid bankside assessment of biological health and has 33 groups. Using the ERF key identify and count the number of invertebrates in your tray. Then record numbers using the tally sheets provided (see Supplementary material: ERF recording sheets). These can be glued or sellotaped into your field notebook

You may wish to make notes on organisms of interest and take photographs or make field sketches. Once you are happy that all the organisms have been identified and counted return the contents of the tray to the river.

Tip

You can use the tally counters to aid counting very abundant taxa.

This process will be repeated at site 2 (Karow) and site 3 (Panke terrace). At both sites you should also take replicate (n = 5) measurements of water quality (DO, EC, pH, Temperature, Turbidity). Ammonia measurements (n = 3) should be collected from site 4 only.

3.2 Quantitative sampling approach

Quantitative sampling approaches enable us to measure the number of individuals per unit area and are used to track changes in populations over space and time. We will use 2 quantitative methods to calculate number of individuals per m2. A surber sampler and adapted shovel sampler. The surber sampler, samples an area of 0.04 m2 the shovel sampler an area of 0.023 m2

Select 3 random locations in the river (aim for uniform substrate conditions to minimise impact of microhabitat differences). For the surber sampler you may require 2 people in the river – one to hold the net and quadrat flush to the river bed, the other to disturb the sediments within the quadrat (see detailed methods in theme workbook). Record the water depth and estimate flow velocity. After collection of each sample return to the bankside and decant contents into a white tray so all organisms can be counted and identified using the ERF key.

For the shovel sampler due to the smaller sampling area select 5 locations to sample as we are trying to standardise the sampling effort (i.e the surface area of streambed sampled).

Record all data in your field notebook, clearly stating the sampling method, replicate number (depth and estimated velocity).

4 Measurement check list

 Kick sample from site 3 and site 4 with organisms identified and counted using the ERF key

 Five replicate spot measurements of EC, DO (saturation and concentration), pH and water temperature for sites 3 & 4.

 Three replicate measurements of ammonia for site 4.

 Replicate surber and shovel samples (ideally 3 & 5 respectively) with organisms identified and counted using either the ERF key

5 Day two data analysis

5.1 Semi quantitative data processing

For each site and identification method (i.e. ARMI, Urban and ERF) sum; 1: the number of different types of taxa (groups) observed, known as the taxonomic richness, and 2. the total abundance of all the organisms, Tabulate this information (see below) or present in graphical form. For each identification resolution use the associated scoring systems (see handbook and handouts provided) to create a biotic index related to organic pollution/water quality. Here you will calculate 3 different scores; 1. The ARMI index (based on 8 groups), 2. The Urban index (based on 14 groups), and 3. The Extended index which is based on 33 groups. Note: All these index is weighted by abundance. Create a new table with your derived variables. Be sure to show any workings in your field notebook.

Variable	Site 2 ARMI	Site 2 Urban	Site 2 ERF_WQ	Site 4 ARMI	Site 4 Urban	Site 2 ERF_WQ
Taxon richness
Total abundance
Biotic index score

Discussion – Write 1-2 sentences on the following in your field notebook

• Was there any difference in taxon richness or abundance between the two sites?

• Do the three methods broadly agree and correspond to patterns in your water quality measurements?

• Do you notice any differences in community composition between the two sites?

• Why do you think it is important to abundance weight biotic indices?

5.2 Quantitative data processing

For each sampling method and replicate count the number of different types of taxa (groups) observed, known as the taxonomic richness) and the total abundance. Calculate the mean and SD for both methods (consult day 1 work sheet for the formulas) and then convert to individuals per m2. Tabulate this information or present in graphical form.

	Variable	Site 2 Surber	Site 2 Shovel	Site 4 Surber	Site 4 Surber
R1	Abun.
R2	Abun.
R3	Abun.
Mean	Abun.
SD	Abun.
R1	Richness
R2	Richness
R3	Richness
Mean	Richness
SD	Richness

Tip

To calculate number m2 use the sum (i.e. abundance) and area sampled (this varies depending on the sampling method) then multiple to make this up to 1 m2

Now calculate the mean value for each taxa based on the two methods. Convert this into relative abundance (i.e. a percentage). Tabulate this information or present in graphical form.

Discussion – Write 1-2 sentences on the following in your field notebook

• Was there any difference in taxon richness or density between the two methods?

• Which method would you recommend for sampling soft-bottomed streams?

• Based on the relative abundance data are there any differences in the community composition associated with the methods?

• When might it be important to use quantitative rather than qualitative sampling approaches?