Polychaete invader enhances resource utilization in a species-poor system

Abstract

Ecosystem consequences of biodiversity change are often studied from a species loss perspective, while the effects of invasive species on ecosystem functions are rarely quantified. In this experimental study, we used isotope tracers to measure the incorporation and burial of carbon and nitrogen from a simulated spring phytoplankton bloom by communities of one to four species of deposit-feeding macrofauna found in the species-poor Baltic Sea. The recently invading polychaete Marenzelleriaarctia, which has spread throughout the Baltic Sea, grows more rapidly than the native species Monoporeia affinis, Pontoporeia femorata (both amphipods) and Macoma balthica (a bivalve), resulting in higher biomass increase (biomass production) in treatments including the polychaete. Marenzelleria incorporated and buried bloom material at rates similar to the native species. Multi-species treatments generally had higher isotope incorporation, indicative of utilization of bloom material, than expected from monoculture yields of the respective species. The mechanism behind this observed over-yielding was mainly niche complementarity in utilization of the bloom input, and was more evident in communities including the invader. In contrast, multi-species treatments had generally lower biomass increase than expected. This contrasting pattern suggests that there is little overlap in resource use of freshly deposited bloom material between Marenzelleria and the native species but it is likely that interference competition acts to dampen resulting community biomass. In conclusion, an invasive species can enhance incorporation and burial of organic matter from settled phytoplankton blooms, two processes fundamental for marine productivity.

Effect of reoxygenation and Marenzelleria spp. bioturbation on Baltic Sea sediment metabolism

“…In the Baltic, colonization by macrofauna, particularly of the invasive genus Marenzelleria, is expected once normoxia is established (Schiedek 1997, Leppä -koski et al 2002, Karlson et al 2011. Our results indicate a 50% decrease in denitrification and a 3-fold increase of DNRA in sediment inhabited by Marenzelleria compared to normoxic non-bioturbated sediments, resulting in a net stimulation effect of denitrification by bottom water oxygenation of only a factor 3 compared to the HY treatment.…”

Modelling macrofaunal biomass in relation to hypoxia and nutrient loading

“…For example, the introduction of Marenzelleria spp. may have implications for both the productivity of the system (Karlson et al, 2011) and for sediment nutrient dynamics (Norkko et al, 2012).…”

Seasonal oxygen, nitrogen and phosphorus benthic cycling along an impacted Baltic Sea estuary: regulation and spatial patterns

“…Furthermore, in the 1980s and early 1990s the sediment hosted different communities of bioturbating fauna dominated by the amphipods Monoporeia affinis and Pontoporeia femorata (Elmgren and Larsson 1997), whereas today the widespread polychaete Marenzelleria spp. dominates benthic macrofauna (Elmgren and Larsson 1997;Karlson et al 2011). Karlson et al (2005) showed that the bioturbation activity of M. affinis stimulated N 2 removal compared to non-bioturbated sediment, whereas recent experiments with conditioned sediment with and without Marenzelleria spp.…”