Increasing densities of an invasive polychaete enhance bioturbation with variable effects on solute fluxes

Abstract

Bioturbation is a key process affecting nutrient cycling in soft sediments. The invasive polychaete genus Marenzelleria spp. has established successfully throughout the Baltic Sea increasing species and functional diversity with possible density-dependent effects on bioturbation and associated solute fluxes. We tested the effects of increasing density of M. arctia, M. viridis and M. neglecta on bioturbation and solute fluxes in a laboratory experiment. Benthic communities in intact sediment cores were manipulated by adding increasing numbers of Marenzelleria spp. The results showed that Marenzelleria spp. in general enhanced all bioturbation metrics, but the effects on solute fluxes varied depending on the solute, on the density and species identity of Marenzelleria, and on the species and functional composition of the surrounding community. M. viridis and M. neglecta were more important in predicting variation in phosphate and silicate fluxes, whereas M. arctia had a larger effect on nitrogen cycling. The complex direct and indirect pathways indicate the importance of considering the whole community and not just species in isolation in the experimental studies. Including these interactions provides a way forward regarding our understanding of the complex ecosystem effects of invasive species.

Legacy Effects of Eutrophication on Modern Methane Dynamics in a Boreal Estuary

“…Our results show strong evidence of bioirrigation, i.e., the introduction of oxic bottom water via animal burrows down to 10 cm or more in the sediment, which greatly reduces sediment flux of methane. Indeed, site J was recently shown to have an active community of benthic fauna that affects solute fluxes seasonally (Kauppi et al 2018), whereas in comparison at site L, there is no benthic fauna, likely due to recurrent seasonal hypoxia or anoxia (e.g., Gammal et al 2017 report 0.0 mg/L O 2 at this site for August 2010). We suggest that this is reflected in the porewater profiles, with CH 4 found much closer to the sediment surface at the hypoxic site L due to the absence of bioirrigation.…”

Estuarine Macrofauna Affects Benthic Biogeochemistry in a Hypertrophic Lagoon

“…While in most deep aquatic ecosystems, meiofauna and microbial communities are drivers of benthic processes, in coastal estuarine systems macrofauna play a major role in organic matter mineralization and nutrient cycling [8,[58][59][60]. The analysis of macrofauna diversity, abundance, functional role, and distribution is therefore central to understand coastal lagoon functioning [16,24]. The latter can be defined as the capacity of sediments to process organic matter inputs, avoiding excess carbon accumulation and resulting in fast nutrient turnover.…”

“…A number of previous studies were targeting a heterogenous set of parameters including dissolved oxygen (O 2 ) , carbon dioxide (TCO 2 ), various nitrogen (N), phosphorus, silica forms, chlorophyll, and functional genes [13][14][15][16]. A large body of scientific work has clearly defined, sometimes at the microscale, how burrowers via intermittent ventilation import O 2 into their burrows and temporally enhance microbial aerobic activity, or how filter-feeders increase sedimentary organic matter via feces and pseudofeces production [17,18].…”

“…A large body of scientific work has clearly defined, sometimes at the microscale, how burrowers via intermittent ventilation import O 2 into their burrows and temporally enhance microbial aerobic activity, or how filter-feeders increase sedimentary organic matter via feces and pseudofeces production [17,18]. Nevertheless, majority of these studies were built on laboratory experiments, with reconstructed sediments and a single macrofauna species [16,[19][20][21][22]. While such approach enables to characterize target organisms and reduces background noise (sediment heterogeneities, presence of non-target macrofauna groups, etc.…”

Effects of the Bioturbating Marine Yabby Trypaea australiensis on Sediment Properties in Sandy Sediments Receiving Mangrove Leaf Litter

“…In some of these studies, including the present study, sieved and homogenised sediments are used to prepare the mesocosms/microcosms [30,32,38,50,[54][55][56] to eliminate effects of local heterogeneity that can mask the effects of the imposed treatments. Alternatively, sediment cores are collected and maintained intact to represent more natural characteristics of the sampled area [15,[57][58][59][60][61].…”