Abstract
How will coastal soils in areas newly flooded with seawater function as habitat for benthic marine organisms? This research question is highly relevant as global sea level rise and coastal realignment will cause flooding of soils and form new marine habitats. In this study, we tested experimentally the capacity of common marine polychaetes, Marenzelleria viridis, Nereis (Hediste) diversicolor and Scoloplos armiger to colonize and modify the biogeochemistry of the newly established Gyldensteen Coastal Lagoon, Denmark. All tested polychaetes survived relatively well (28–89%) and stimulated carbon dioxide release (TCO2) by 97–105% when transferred to newly flooded soils, suggesting that soil characteristics are modified rapidly by colonizing fauna. A field survey showed that the pioneering benthic community inside the lagoon was structurally different from the marine area outside the lagoon, and M. viridis and S. armiger were not among the early colonizers. These were instead N. diversicolor and Polydora cornuta with an abundance of 1603 and 540 ind m-2, respectively. Considering the species-specific effects of N. diversicolor on TCO2 release and its average abundance in the lagoon, we estimate that organic carbon degradation was increased by 219% in the first year of flooding. We therefore conclude that early colonizing polychaetes modify the soils and may play an important role in the ecological and successional developments, e.g. C cycling and biodiversity, in newly flooded coastal ecosystems. Newly flooded soils have thus a strong potential to develop into well-functioning marine ecosystems.
Highlights
Future sea levels are predicted to rise 2–16 mm yr-1 as a consequence of climate change, implying 0.2–1.2 m higher average sea levels by year 2100 [1]
Polychaete recovery at the end of the experiment was not different between soil types, but varied according to species, with lower recovery for M. viridis (22–44%) than for N. diversicolor (55–78%) and S. armiger (86–89%) (F2,17 = 69.0, p
It was impossible to identify whether they escaped from uncultivated soil (UC) or C treatments, since cores of both soil types were incubated in the same tanks
Summary
Future sea levels are predicted to rise 2–16 mm yr-1 as a consequence of climate change, implying 0.2–1.2 m higher average sea levels by year 2100 [1]. Some low-lying coastal areas will be permanently flooded in the future [2] These include coastal soils with low elevation and gentle slopes towards the inland and areas that are currently below mean sea level and kept dry by drainage and dikes. Engineering techniques such as coastal realignment [3] may be implemented to protect valuable assets in coastal zones, which will result in the formation of newly flooded habitats. This research question is highly important for the future management of coastal zones.
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