Streams To Spiders: How Aquatic Insects Interconnect Our Ecosystems

Posted byKeiron Derek BrownPosted inBlog, entoLIVE Blog

Freshwaters and forests might seem like definitively separate habitats, but they are in fact tightly interconnected by insects. These insects, such as mayflies, dragonflies and mosquitoes, develop in water but emerge onto land as winged adults, with a powerful impact on the surrounding landscape. Some feed birds, bats, lizards and spiders, others transfer microplastics and heavy metals out of rivers and others form swarms so large they are picked up by weather satellites. This talk delves into how these largely overlooked insects create an interconnected world in ways we don’t always expect.

Q&A with Liam Nash

Liam Nash is a 4th-year NERC PhD student primarily based at Queen Mary, University of London in collaboration with ZSL and the University of Campinas. He specialises in community and conservation ecology and has worked with all kinds of invertebrates in Brazil and across the UK.

  • Late and reduced emergences of mayflies have been observed in my area (northeast Wales) but caddisflies attracted to my light trap don’t show the same. Have you suggestions about why this might be?
    My research has looked at things from a broad perspective and looking at overall patterns, rather than focusing on individual species or groups. There could be a wide range of triggers that are impacting emergence times, and these will vary between groups (such as mayflies and caddisflies) and even between species. If we take changing climate as an example, and the impacts that this has on temperature – this could impact different species depending on the specific trigger for emergence for a given species. In some species, emergence may be triggered by the winter temperature, while others may be triggered by the spring temperature. In others still, it could be that reaching a specific temperature is a trigger or a sustained period above a temperature. Climate change affects each of these temperature variables in different ways. So, in summary, the only way to answer your question with confidence would be to study the species (or species groups) present in that area to better understand the triggers for emergence and how they might be changing over time.
  • Did you undertake canopy sampling within your research?
    Unfortunately, the answer is no. We focused on ground-level surveys of the vegetation and looked at the lateral movement/impact of freshwater insects from the stream into the forest. Insects do, obviously, also travel upwards too and it would have been great to include surveying at different heights within the forest, but we were limited by what could be achieved within the time frame and resources that were available. Canopy surveying can be complex and would have required more equipment, making it too expensive for us to undertake.
  • Do you think that humidity may have an influence on insect distance away from water?
    This is something that was simply out of scope for my research project. I’m aware that humidity can impact the flying ability of some insect groups so it is important, and humidity may factor into the emergence times of some species.
  • Did you notice if the spiders that you found were mostly from a particular group?
    We looked at the overall spider community, rather than breaking it down into families or species, so I can’t give you a definitive answer to this question. Again, it would have been great to look at this in more detail if we had more capacity. However, from my own personal observations, I can say anecdotally that some of the dominant groups in the tropics in our samples were sac spiders, tangle-web and jumping spiders. The long-jawed orb weavers are known to be specialists of aquatic prey so this was not necessarily what you’d expect so near water. In the UK, I was surprised at how spread out throughout the transects these specialist spiders were – rather than being concentrated near the water. I wonder if this could be to do with the fact that the UK forests were more open and managed.
  • Did you consider eutrophication and the oxygen levels within the streams?
    We didn’t measure oxygen levels within any of the streams, but we know that this can be important so we tried to standardise this variable by only using streams that were in some kind of protected area, in the hope that these would be less likely to suffer from eutrophication.

Literature references

Further info

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Published by Keiron Derek Brown

A blog about biological recording in the UK from the scheme organiser for the National Earthworm Recording Scheme.

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