The polychaete Marenzelleria viridis is an invasive species and often replaces the native Nereis diversicolor. This shift leads to more reduced conditions and changes in the biogeochemical function of the sediments. By combining imaging techniques for O2 (planar optodes) and irrigation patterns (rhodamine WT and brilliant blue), we investigated the relationship between irrigation and O2 dynamics in burrows of M. viridis. The investigated animals shifted between 2 modes of ventilation: ciliary pumping for 77% of the time and muscular pumping for 23% of the time. On average, muscular pumping was induced every 0.4 h. During ciliary pumping, oxic water was pumped into blind-ended burrows and into the surrounding sediment, inducing an upward porewater transport of O2-depleted water. This pattern was reversed during muscular pumping. The 2 pumping modes induced oscillating O2 penetration along the burrow wall and along the primary sediment-water interface. The average net downward irrigation rate, including both pumping modes, amounted to 11.1 × 10−3 ± 2.4 × 10−3 ml min−1. The estimated average oxic sediment volume was 2.1 ± 0.5 cm3 per burrow, and the burrow-specific O2 consumption was 45.6 ± 18.1 nmol min−1. M. viridis burrows and the ambient sediment are relatively O2 depleted, with intensified rates of O2 consumption, compared to similar-sized native N. diversicolor. The complex O2 dynamics induced a unique icroenvironment that must favor meiofauna and microbial communities that are tolerant to oxic-anoxic oscillations or that have the ability to migrate along with the pulsing oxic-anoxic interface.
Marine Ecology - Progress Series, 2014, Vol 504, p. 181-192