Bioturbation by macrofauna and its effects on oxygen environments within tidal sediments

Abstract

The burrow irrigation rates of Laomedia were measured using an electromagnetic flow meter. A burrow system with one mound and eight funnels was selected for the measurement.The average burrow irrigation rate during the flooding of about 4 hours was 24.7 ℓ/h in the mound and 2.9 ℓ/h in the funnel. The irrigation had two peaks: the one was between 10 min and 30 min after the flooding and the other one was between 10 min and 50 min before the ebbing the maximum value occurred in the former duration. Laomedia’s burrow spacing and bio-irrigation can result that about 22,400 cm3 of oxic sediments exists below 1m2 surface area, which means increase in oxic sediments up to 17 times compared to unburrowed sediments. If the burrow space is added, oxic volume within the tidal sediments attains up to 111,600 cm3 per unit m2. The study area has a flooding duration of roughly 7 hours per day. If we assume that Laomedia pumps 24.7 l/h, each shrimp would pump 173 l/d and would flush their burrow water 17 times a day in a maximum. Oxygen penetration into anoxic sediment and water exchanges between burrow waters and overlying waters by burrow spacing and bio-irrigation impacts on biogeochemical processes and, subsequently, can strongly accelerate the degradation of organic materials within tidal sediments and more detailed material flux between tidal sediments and overlaying wates will be expected.ours was 24.7 ℓ/h in the mound and 2.9 ℓ/h in the funnel. The irrigation had two peaks: the one was between 10 min and 30 min after the flooding and the other one was between 10 min and 50 min before the ebbing the maximum value occurred in the former duration. Laomedia’s burrow spacing and bio-irrigation can result that about 22,400 cm3 of oxic sediments exists below 1m2 surface area, which means increase in oxic sediments up to 17 times compared to unburrowed sediments. If the burrow space is added, oxic volume within the tidal sediments attains up to 111,600 cm3 per unit m2. The study area has a flooding duration of roughly 7 hours per day. If we assume that Laomedia pumps 24.7 l/h, each shrimp would pump 173 l/d and would flush their burrow water 17 times a day in a maximum. Oxygen penetration into anoxic sediment and water exchanges between burrow waters and overlying waters by burrow spacing and bio-irrigation impacts on biogeochemical processes and, subsequently, can strongly accelerate the degradation of organic materials within tidal sediments and more detailed material flux between tidal sediments and overlaying wates will be expected.