Abstract
Seagrass meadows are globally important ecosystems for carbon (C) sequestration. However, bioturbation by benthic fauna can alter the distribution, degradation and overall preservation of C in the sediment. We performed a 4 wk laboratory experiment to investigate the short-term degradation and burial of 2 major C sources in bare sediments associated with seagrass ecosystems. Eelgrass Zostera marina and macroalgal (Fucus vesiculosus) detritus were amended in sediment with and without bioturbation by the common polychaete Arenicola marina. Bioturbation did not significantly affect the loss of eelgrass detritus (>0.5 mm), but caused a rapid burial of this material as a discrete layer (55% recovery) at sediment depths ranging from 8 to 14 cm. A. marina effects on macroalgal detritus were more pronounced, resulting, in total, in an 80% loss of macroalgal detritus by microbial degradation and worm ingestion. We conclude that A. marina bioturbation effectively buries eelgrass detritus into deep anoxic sediments, but we cannot confirm that this leads to enhanced C preservation in coastal ecosystems. In contrast, A. marina bioturbation significantly increases the degradation of macroalgal tissue, and it is unlikely that this detritus is a major source for permanent C burial.
Highlights
Coastal ecosystems including seagrass beds, saltmarshes, and mangrove forests are highly productive and sequester large amounts of organic carbon (Corg) in the sediment, serving an important role in the global carbon (C) cycle and climate change mitigation (Duarte et al 2005, Fourqurean et al 2012)
We investigated the effects of Arenicola bioturbation on the short-term fate of eelgrass Zostera marina and macroalgal (Fucus vesiculosus) detritus in sandy coastal sediments
A 27 d laboratory experiment was set up to assess the effect of Arenicola bioturbation on the degradation and burial of Zostera and Fucus detritus in the sediment
Summary
Coastal ecosystems including seagrass beds, saltmarshes, and mangrove forests are highly productive and sequester large amounts of organic carbon (Corg) in the sediment, serving an important role in the global carbon (C) cycle and climate change mitigation (Duarte et al 2005, Fourqurean et al 2012). Arenicola is considered an ecosystem engineer due to its large capacity for both sediment particlereworking and burrow ventilation (Kristensen et al 2012). It significantly alters the sediment texture by selectively ingesting particles
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