Aquatic Invertebrates
Back to the Monitoring Hub
Increase diversity of freshwater invertebrates
Data collection in progress
Kakheti Steppes
Georgia
Problem: The Dali dam construction began on the Iori river in 1984, and since its completion in the 1990s has led to a reduction in hydrological flow below the dam, resulting in increasingly dry conditions, reduced sediment transport, and a degraded river ecosystem, which is reducing the aquatic insect diversity within the river.
Action: SABUKO is working with the dam managers to recreate flooding events by periodically releasing water from the dam. They are also constructing gabions to retain water in the floodplain area when water is released, benefitting aquatic invertebrates that require the continued presence of water for one or more stages in their life cycle.
Indicator: The diversity and abundance of freshwater invertebrates is monitored before and after gabion installation. This will enable SABUKO to assess the effectiveness of their efforts in improving water habitat area and condition.
Methods
To collect aquatic diversity data, SABUKO selected six strategic sites along the Iori River. Three samples were taken at each site, 50 m apart from each other, on the same day in September 2023, resulting in 18 total samples (see Fig. 1 below). To collect samples, benthic hand nets were used (also called kick nets) with a mesh size of 500 µm/0.5 mm.
Figure 1: Map of aquatic invertebrate sampling sites along the Iori River.
Samples were washed and fixed in ethanol for transporting back to the lab, where they were sorted and identified under the microscope, in most cases to family level (exceptions were Oligochaeta and Acariformes). From this dataset, the following variables were calculated:
- BMWP: the BMWP (Biological Monitoring Working Party) index considers the sensitivity of invertebrates to pollution; families are assigned a score between 1 (least sensitive) and 10 (most sensitive). The BMWP score is the sum of the values for all families present in the sample. This index was established in the UK and has been successfully applied in many other countries.
- ASPT: related to the BMWP index, the ASPT (Average Score Per Taxon) is determined by dividing the BMWP score by the number of taxa present. A high ASPT score is considered indicative of a clean site containing many high-scoring taxa.
- FBI: the FBI (Family Biotic Index) scores each family according to their sensitivity to organic pollution, from 1 (high sensitivity) to 10 (low sensitivity), and then calculates an index using the scores of families present in the sample. A lower score therefore generally indicates better water quality.
- TR: TR (Taxon Richness) is the number of taxa found in a sample. A wide variety of taxa suggests good water quality and habitat condition. However, this index is less precise than the others applied.
Together these metrics provide a more complete picture of the health of the river ecosystem and will help SABUKO to evaluate the success of their restoration intervention.
Results
During the initial phase of data collection, 6778 individuals were sampled, belonging to 26 different families. Baetidae (one of the mayfly families) emerged as the most abundant taxon, recognized for its sensitivity to environmental changes. This was followed by the more tolerant families Simuliidae (blackflies) and Chironomidae (midges). Values for the different biotic indices for samples from each site are shown below (Fig. 2).
Figure 1: Total abundance of each macroinvertebrate taxon across all samples.
Figure 2: Biotic index values for macroinvertebrate samples from six points along the Iori River. See above for explanations of each biotic index.
Repeating this data collection will allow evaluation of the impact of the gabion that has been installed at P2, and will be used to guide decisions regarding the potential placement of additional gabions in other sections of the river exhibiting similar ecological characteristics.
Partners
