Role of Macrofaunal Communities in the Vistula River Plume, the Baltic Sea—Bioturbation and Bioirrigation Potential

Abstract

Macrozoobenthos plays a key role in the transformation of inputs from rivers to the sea, such as nutrients, organic matter, or pollutants, and influences biogeochemical processes in the sediments through bioturbation and bioirrigation activity. The purpose of our study was to determine the structure of benthic communities, their bioturbation (BPC) and bioirrigation potential (IPC), and the vertical distribution of macrofauna in the Gulf of Gdańsk. The study revealed changes in the structure of benthic communities and, consequently, in the bioturbation and bioirrigation potential in the study area. Despite the presence of diverse and rich communities in the coastal zone, BPC and IPC values, although high, were formed by a few species. Both indices were formed mainly by the clam Macoma balthica and polychaetes, although the proportion of polychaetes in IPC was higher than in BPC. In the deepest zones, the communities became poorer until they eventually disappeared, along with all macrofaunal functions. Both indices changed similarly with distance from the Vistula River mouth, and there was a very strong correlation between them. We also demonstrated that the highest diversity of the macrofauna was observed in the upper first cm of the sediment, but the highest biomass was observed in deeper layers—at a depth of up to 6 cm, and single individuals occurred even below 10 cm.

Functional structure and diversity of marine benthos reflect food availability and quality, as evidenced by isotopic diversity

“…The taxonomic composition in the study area was in agreement with the previously described division into shallow and more offshore communities that was observed in the southern Baltic Sea (Gic-Grusza et al 2009;Gogina et al 2016;Włodarska-Kowalczuk et al 2016;Miernik et al 2023). We noticed three functionally distinct communities, one present at both deeper sites, and two different for each shallow site (Table 2).…”

Spatial and seasonal pattern of microbial nitrate reduction in coastal sediments in the Vistula River plume area, Gulf of Gdańsk

“…Sediments at the study area were mainly characterized by finegrained sand with organic matter content increasing from the shallower to the deeper sites (Thoms et al, 2018;Miernik et al, 2023). Indeed, sedimentary material discharged by the Vistula River is initially deposited in the shallower area and is subsequently remobilized and transported to deeper areas (Damrat et al, 2013).…”

“…For statistical purposes, to analyze the potential role of macrofauna bioturbation as a co-regulator of the benthic N cycle, the retrieved organisms were divided into three groups. Groups identified the macrofauna burial depth and burial type in shallow burrowers, deep burrowers (burrow/tube dwellers) and free-living deep burrowers (Thoms et al, 2018;Miernik et al, 2023).…”

“…Polychaetes such as Marenzelleria spp. and Hediste diversicolor can dig up to several centimeters into the sediment in the Gulf of Gdanśk (Miernik et al, 2023). They impact the processes not only by influencing sediment structure and pore water chemistry, but also by affecting the microbial diversity, and also as holobionts (Dale et al, 2019;Zilius et al, 2022).…”