Thin terrestrial sediment deposits on intertidal sandflats: effects on pore-water solutes and juvenile bivalve burial behaviour

[摘要] Nearshore zones experience increased sedimentation due tocoastal development and enhanced loads of fine terrestrial sediment(hereafter, TS) in river waters. Deposition of TS can alter seabedbiogeochemical processes but the effects on benthic ecosystem functioningare unknown. The results of a past experiment with defaunated, intertidalsediment suggest that a decrease in the oxygenation of this sediment by athin (mm) TS deposit causes substrate rejection (refusal to bury) bypost-settlement juvenile recruits of the tellinid bivalve Macomona liliana. We furtherexamined this behaviour, asking if such deposits negatively affect burialwhen applied to intertidal sediment that is oxygenated by bioturbation (C)or depleted of dead and living organic matter (D). We observed recruits onthe surface of four treatments: C, D, and the same sediments to which weadded a 1.7–1.9 mm layer of TS (CTS, DTS). The TS deposit decreased theoxygenation and the pH of the underlying intertidal sediment (CTS)confirming previous results, but significantly increased but not decreasedthe probability of burial, irrespectively of treatment. Juveniles morelikely buried into C than into D. The mechanism that caused previouslyobserved substrate rejection by post-settlement juvenile M. liliana remains unclearbut our results suggest that contact of the recruits with the TS depositdoes not cause substrate rejection. We now hypothesise that conditioning ofsediment by bioturbation can mediate negative effects of TS deposits on therecruits' burial behaviour.

[学科分类] 地球化学与岩石