The Introduced Fanworm, Sabella spallanzanii, Alters Soft Sediment Macrofauna and Bacterial Communities

Abstract

The Mediterranean fanworm, Sabella spallanzanii, is listed as an introduced and established "unwanted species" in New Zealand, subject to nationwide targeted surveillance in port, marina, urban and natural environments. Sabella spallanzanii has the potential to change soft-sediment benthic habitats due to the physical presence of the fanworm's tube and associated biological activities, particularly suspension feeding and bio-deposition. A 6-month field experiment was conducted to investigate the impacts of S. spallanzanii on the structure and diversity of existing communities within invaded soft-sediment habitats. Macrofaunal communities were assessed using traditional sampling and identification via microscopy, while microbial and eukaryotic communities were characterized using metabarcoding of 16S and 18S ribosomal genes, respectively. Live and mimic S. spallanzanii were transplanted at different densities (10-50 individuals per m 2) into experimental plots with existing assemblages, to test for potential biological and/or physical effects on benthic communities. Analyses revealed significant differences in macrofaunal, eukaryote, and bacterial assemblages in the presence of live S. spallanzanii and mimics, underpinned by changes in the relative abundance of several taxa, indicating that these effects are brought about by biological and physical functions. The presence of S. spallanzanii did not alter total abundance and taxa richness of benthic assemblages but resulted in compositional differences. We found no effect of live or mimic worm density on the structure and diversity of the studied communities. Changes in the structure of native benthic communities, as indicated by this study, can potentially impact functioning of soft-sediment habitats, through alterations to nutrient cycling, bioturbation and benthic-pelagic coupling. Quantitative measurements of impacts are crucial to understand the trajectory of marine invasions, their roles in restructuring communities, and to guide management efforts.

Invasive ecosystem engineers threaten benthic nitrogen cycling by altering native infaunal and biofouling communities

“…Autogenic engineering is the alteration of physical aspects of the environment by www.nature.com/scientificreports www.nature.com/scientificreports/ the bodies of the engineers themselves (e.g., alteration of flow regimes by Sabella tubes or provision of habitat for other organisms), whereas allogenic engineering is the alteration of physical environmental properties via mechanical or chemical means (e.g., extraction of particulate material by Sabella) 1 . Shifts in bioturbating ecosystem engineers (e.g., Echinocardium cordatum 16 ) suggest the autogenic influence of the introduced species (Sabella) may be partially mediated through shifts in the composition of native fauna, flora and microbiota 52 which play important functional roles in nutrient cycling, particularly removal of bioavailable nitrogen (i.e., denitrification). Alterations of infaunal community composition was observed by Ross et al 28 , and our results suggest this may be associated with a combination of crowding and interception of suspended particulate organic material by Sabella and biofouling on its tubes.…”

Impacts of alien polychaete species in marine ecosystems: a systematic review

“…In Australia research groups lead by the polychaete taxonomists Pat Hutchings, Elena Kupriyanova and Christopher J. Glasby are active at national museums of the country, while in New Zealand the research by Geoffrey Read at the National Institute of Water and Atmospheric Research is active in the taxonomy of polychaetes. In these last two countries the polychaete taxonomists collaborate with institutions and are involved in programmes in biosecurity such as the Center for Introduced Marine Pests (CRIMP) established by Australia in the early 1990s and the Biosecurity Act of 1993 in New Zealand which provides for targeted surveillance in harbours, ports, marinas and high-value natural environments (Atalah et al, 2019).…”

“…Once established in recipient regions, alien species may cause significant changes to local species richness and abundance, population genetic composition, behaviour patterns, trophic networks, ecosystem productivity or habitat structure through competition, displacement or predation (Brooks et al, 2004;Hendrix et al, 2008;Shine, 2010;Pyšek et al, 2012;Ricciardi et al, 2013). There has therefore been significant interest in evaluating the impacts of alien species in different components of recipient ecosystems (Blackburn et al, 2014;Bacher et al, 2018;Pyšek et al, 2020). Unfortunately, marine invasion science can be biased towards certain taxonomic groups, study types, marine systems and invasion stages.…”

“…barnacles, bryozoans and sponges) (Holloway & Keough, 2002a, 2002b or the post-colonization process of other macrofauna (O'Brien et al, 2006). In fact, most of the studies conducted in Australia and New Zealand showed that this species causes changes in the composition of macrofauna and nutrient cycling with regards to the process of denitrification and bacterial communities (Ross et al, 2013;Atalah et al, 2019;Tait et al, 2020). It has even been suggested that the presence of S. spallanzanii increased the local biodiversity, although this increase probably also included other alien species (Douglas et al, 2020).…”

A Rapid Molecular Assay for Detecting the Mediterranean Fanworm Sabella spallanzanii Trialed by Non-Scientist Users

“…Despite efforts to eradicate S. spallanzanii at the initial incursion area and mitigate its further spread (Fletcher, 2014), soon it was found in multiple harbors across the North and South Islands (Fletcher, 2014). Being a highly effective suspension filter feeder (Clapin, 1996) and an ecosystem engineer (O'Brien et al, 2006), the fanworm can impact abundance and recruitment patterns of invertebrate larvae (O'Brien et al, 2006;Ross et al, 2007) and alter benthic macrofauna and microbial communities adjacent to S. spallanzanii canopies (Atalah et al, 2019). Because of its high invasive potency and adverse ecological impacts, the uncontrolled spread of S. spallanzanii threatens species native to New Zealand and puts local economies at risk.…”