Shifts in coastal fish communities: Is eutrophication always beneficial for sticklebacks?

A1 Journal article (refereed)

Internal Authors/Editors

Publication Details

List of Authors: Karine Gagnon, Max Gräfnings, Christoffer Boström
Publication year: 2017
Journal: Estuarine, Coastal and Shelf Science
Journal acronym: Estuar. Coast. Shelf Sci.
Volume number: 198
Start page: 193
End page: 203


Following declines of predatory fish, mesopredators such as sticklebacks have been linked to shifts in
coastal trophic networks through both top-down (preying on mesograzers and facilitating algal blooms)
and bottom-up (benefitting from eutrophicated conditions) processes. Here, we tested whether the
association between eutrophication effects (filamentous algae and turbidity) and sticklebacks held true
in the Finnish Archipelago Sea where predatory fish populations have remained stable. If so, sticklebacks
should be more abundant in the middle archipelago, where eutrophic conditions have led to increased
turbidity, higher filamentous algal loads, and decreased cover of submerged aquatic vegetation (SAV),
than in the outer archipelago, where environmental conditions are better. We measured the spatial and
seasonal variation of sticklebacks (three-spined Gasterosteus aculeatus and nine-spined Pungitius pungitius) in middle and outer archipelago sites, as well as environmental variables potentially affecting their

Adults and juveniles of both species were more abundant in the outer than middle archipelago. The
outer archipelago was characterized by greater Secchi depth throughout the summer and higher SAV
cover in late summer. Secchi depth was positively correlated with stickleback abundance of both species,
while SAV cover was also positively correlated in late summer. Filamentous algal cover was high in both
the middle and outer archipelago, but not consistently associated with stickleback abundance
throughout the summer. While sticklebacks have been thought to both contribute to, and benefit from,
eutrophication, our results instead suggest that the resulting environmental changes may have adverse
effects on sticklebacks, especially if predators are present. This may lead them to shift their breeding
grounds and spatial distribution to less eutrophicated areas where lower turbidity and the resulting
increased availability of SAV provide refuge from predators for juveniles, and higher quality breeding and
feeding grounds for adults.

Last updated on 2019-12-12 at 03:30