Sea lamprey nests promote the diversity of benthic macroinvertebrate assemblages
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Date
2022-12Author
Dhamelincourt, Marius
Rives, Jacques
Pons, Marie
Larrañaga Arrizabalaga, Aitor
Tentelier, Cedric
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PLOS One 17(12) : (2022) // Article ID e0274719
Abstract
The habitat heterogeneity hypothesis states that increased habitat heterogeneity promotes
species diversity through increased availability of ecological niches. We aimed at describing
the local-scale (i.e. nest and adjacent substrate) effects of nests of the sea lamprey (Petro-
myzon marinus L.) as ecosystem engineer on macroinvertebrate assemblages. We hypoth-
esized that increased streambed physical heterogeneity caused by sea lamprey spawning
would modify invertebrate assemblages and specific biologic traits and promote reach-scale
diversity. We sampled thirty lamprey nests of the Nive River, a river of the south western
France with a length of 79.3 km and tributary of the Adour River, in three zones: the unmodi-
fied riverbed (upstream) and zones corresponding to the nest: the area excavated (pit) and
the downstream accumulation of pebbles and cobbles (mound). The increased habitat het-
erogeneity created by lamprey was accompanied by biological heterogeneity with a reduced
density of invertebrates (3777 ± 1332 individuals per m2 in upstream, 2649 ± 1386 individu-
als per m2 in pit and 3833 ± 1052 individuals per m2 in mound) and number of taxa (23.5 ±
3.9 taxa for upstream, 18.6 ± 3.9 taxa in pit and 21.2 ± 4.5 taxa for mound) in the pit com-
pared to other zones. However the overall taxa diversity in nest increased with 82 ± 14 taxa
compared to the 69 ± 8 taxa estimated in upstream zone. Diversity indices were consistent
with the previous results indicating a loss of α diversity in pit but a higher β diversity between
a pit and a mound than between two upstream zones, especially considering Morisita index
accounting for taxa abundance. Trait analysis showed high functional diversity within zones
with a reduced proportion of collectors, scrapers, shredders, litter/mud preference and small
invertebrates in mound, while the proportion of “slabs, blocks, stones and pebbles” prefer-
ence and largest invertebrates increased. Pit presented the opposite trend, while upstream
had globally intermediate trait proportions. Our results highlight important effects on species
and functional diversity due to habitat heterogeneity created by a nest-building species,
what can ultimately influence food webs and nutrient processes in river ecosystems
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