Anthropogenic effects on Posidonia oceanica fields in Kvarner Bay (Croatia) inferred by a live-dead study of seagrass-associated molluscs

Roberto Joseph Pineyro Partl
2020 unpublished
Molluscan living (LAs) and death assemblages (DAs) were sampled from two separate Posidonia oceanica meadows in Kvarner Bay (Croatia) for a live-dead (LD) study of fidelity. Regarded as good bioindicators, Posidonia biocoenoses are sensitive to recent anthropogenic disturbances in the littoral zone. Problematically, limiting impact assessments to short observation windows (i.e., days to years) overlooks human activity prevalence across larger timeframes (i.e., decades to centuries). Durable
more » ... ogical material from previous communities (e.g., molluscan shells) help uncover pre-impact community states to distinguish between natural and anthropogenic community shifts over time. LD studies of fidelity quantitatively assess whether biological attributes (e.g., species richness, evenness, taxonomic similarity, rank-abundances) characterizing DAs (i.e., taxonomically identifiable, dead organic remains) and LAs, match. Assuming DAs are time-averaged, strong assemblage resemblance (LD agreement) suggests pristine habitat settings, whereas strong discrepancies (LD mismatch) indicate ecological change, likely caused by anthropogenic disturbances. The evaluated meadows are subject to different impact levels: Krk (impacted) was expected to produce lower LD agreement than Kormati. Although multivariate analyses confirm assemblages and fields are compositionally distinct, compositional agreement does not suggest sizeable impacts in either meadow. No indications of community assemblage turnover were revealed, and taxonomic similarity is elevated across all samples. Lastly, depressed DA diversity metrics could be influenced by taphonomic processes, but (low) time-averaging effects are more likely. Despite distinctive amounts of human presence, the LAs depict typical molluscan communities, implying resilience to moderate human activity
doi:10.25365/thesis.65256 fatcat:p6a73aeoundpxgvuybwgwul6fe