ZOOPLANTON DATA REPORT: LLYN MAELOG WETLAND
Earlier this year, we carried out a baseline survey to explore what kinds of freshwater life are using the habitat beneath our Llyn Maelog floating wetland. The Floating Wetland project is a pilot study looking at how constructed wetlands could improve water quality and increase biodiversity by providing cover, feeding areas, and breeding habitat – but how effective are they?
In February 2025 the first samples were collected, setting out to compare the aquatic invertebrate life beneath the wetland with that in the adjacent open water, to see what difference the wetland might be making.
How We Surveyed
Using a fine-mesh net from a boat, samples were taken from directly under the floating wetland and from nearby open water. The survey focused on two groups:
Zooplankton – microscopic animals like water fleas and copepods that drift in the water column.
Macroinvertebrates – larger invertebrates including insect larvae, snails, worms, and amphipods.
All samples were preserved and later analysed under laboratory microscopes to identify the species present.
Key Findings
Zooplankton
Zooplankton abundance was low overall, which is expected during the colder months when activity slows down. Copepods were the most common group across all sites, known for their resilience in a range of conditions.
We also found higher numbers of Bosmina (a type of cladoceran or water flea) in the open water sample, possibly reflecting differences in light, predation pressure, or water movement between the habitats.
Macroinvertebrates
This is where we saw the clearest contrast:
Beneath the floating wetland, we recorded a much higher diversity and abundance of macroinvertebrates.
Species included:
Chironomid (non-biting midge) larvae
Damselfly nymphs
Freshwater snails (including Radix balthica)
Springtails
Amphipods
Bryozoans – colonial filter-feeding animals that attach to surfaces and can indicate stable, oxygen-rich conditions
In contrast, the open water samples yielded very few macroinvertebrates.
What This Tells Us
These results suggest that the floating wetland is providing important habitat benefits, even during winter when invertebrate activity is typically low. The structure offers shelter, stable surfaces for attachment, and food sources that are largely absent in the open water column.
Bryozoans, for example, are good indicators of improved habitat conditions, and the presence of damselfly larvae suggests that predatory invertebrates are also using the area – a sign of a developing food web.
Recommendations and Next Steps
This is an encouraging early result that shows the floating wetland is enhancing habitat complexity and supporting biodiversity. To build on these findings, we are planning:
Seasonal repeat surveys in spring and late summer, when aquatic invertebrate communities are more active and diverse.
Longer-term monitoring to track changes over time and measure any improvements in water quality.
Broader surveys, including fish and amphibians, to better understand how the wetland is being used by other wildlife.
Over time, we hope to see the floating wetland support an even richer community of species and contribute to improved ecological function in the lake.
