Effects of two estuarine intertidal polychaetes on infaunal assemblages and organic matter under contrasting crab bioturbation activity

FERNANDA ALVAREZ; M CIELO BAZTERRICA; MARIANA ADDINO; EUGENIA FANJUL; MACARENA VALIÑAS; OSCAR IRIBARNE; FLORENCIA BOTTO

JOURNAL OF SEA RESEARCH

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2018 vol. 139 p. 33 - 40

1385-1101

Polychaetes and burrowing crabs are widely distributed inintertidal soft bottom environments, playing an important role in structuringinfaunal assemblages through trophic and non-trophic interactions such as bioturbation.In southwestern Atlantic (SWA; 37°40′S, 57°23′W) intertidal mudflats, thepolychaetes Laeonereis acuta and Neanthes succinea coexist withthe burrowing crab Neohelice (Chasmagnathus) granulata. N. granulataand L. acuta strongly modify the sediment characteristics at differentspatial scales, changing the infaunal assemblages and probably affectingfeeding mode of N. succinea,which could prey upon L. acuta.Here, we experimentally evaluated the effects of constant densities of L.acuta and N. succinea on the benthic species assemblages andsediment organic matter (OM) content in two contrasting scenarios of crabbioturbation: inside and outside crab beds. We found that (1) both polychaetesdid not affect the mean density of other macrofaunal organisms neither themeiofauna in general, but L. acuta modifiesthe abundance of specific groups such as foraminiferans; (2) polychaetes producedchanges in meiofaunal spatial distribution probably by adding habitatheterogeneity; and (3) no evidence of predation of N. succinea on L. acutawere observed. Additionally, the variable effects of polychaetes on chlorophylland OM content showed that they were species-specific and also modified by crabbioturbation. Moreover, effects of crab bioturbation on primary producers,quality and content of OM, and on some macro and meiofaunal organisms werefound. Our results suggest that the effects of L. acuta and N. succinea on benthic species and OM content are mostlyspecies-specific and, with regard to food sources (OM content andmicrophytobenthic biomass), strongly modified by larger scale crab bioturbation.