Insect community organisation in estuaries: the role of the physical environment

• Published in: Ecography
• Main Authors: Williams, D. Dudley, Hamm, Tanya
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2002
• Subjects: North Atlantic
• Online Access: https://doi.org/10.1034/j.1600-0587.2002.250314.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1034%2Fj.1600-0587.2002.250314.x; https://onlinelibrary.wiley.com/doi/pdf/10.1034/j.1600-0587.2002.250314.x

Insects are reportedly uncommon in marine habitats and, from a spatial/temporal intercomparison perspective, estuaries are among the least studied. We examined the natural variability seen among insect community organisation in estuaries on both sides of the North Atlantic, and evaluated the role of their physical environments. Community composition was found to be strongly influenced by three physical factors: estuary size, the degree of inundation by incoming tides, and substrate size/stability. Insects formed a significant proportion (17–54%, by numbers) of the benthic community of coarse‐grained‐substratum estuaries, and species richness increased with estuary size. Nymphs/larvae of mayflies, stoneflies, caddisflies, elmid beetles and chironomids dominated channel sites inundated by up to 25% of all incoming tides, but a gradual loss in species richness occurred downstream. However, even the most seaward sites supported high insect densities (up to 25 016 and 5433 m −2 , supporting 26 and 4 species, at sites inundated by 75 and 100% of all incoming tides, respectively). Sites covered by tides for between 3 and 5 h twice daily were dominated by orthocladine chironomids, especially of the genus Orthocladius . Chironomid larvae contribute significantly to the diets of some coastal fish species, particularly juvenile flounder and sticklebacks. We present a schematic model summarising the relationships between estuary size, degree of inundation by salt water and insect community structure.