Control by fiddler crabs and plant roots on biogeochemistry in mangrove sediment, north Queensland

The experiment examined the influence of mangrove saplings (Avicennia marina) and fiddler crabs (Uca vocans) on carbon, iron and sulfur biogeochemistry in mangrove sediment. Four mesocosms represented 4 treatments: without crabs and with plants; without crabs and plants; with crabs and plants; with crabs and without plants.Air and water temperature were recorded.Flux measurements:Benthic primary production was determined as carbon (CO2) exchange across the sediment-water interface of inundated sediment (total CO2 and DOC analyses) and across the sediment-air interface of air-exposed sediment. O2 production in the light and O2 demand in the dark were measured. Anaerobic carbon oxidation and iron respiration were quantified in the sediment. Porewater concentrations of total CO2, DOC and Fe2+ were determined. Sediment remaining after porewater extraction was homogenised under N2 for reactive Fe(II) extraction by an HCl technique.Iron reduction was measured as Fe(II) generation.Sulfate reduction was measured by the core injection technique.Chlorophyll a concentrations were used as a measure of microalgal abundance.Samples for enumeration of bacterial populations were taken in parallel with Chl a. To examine the influence of mangrove roots and crabs on carbon, iron and sulfur biogeochemistry in mangrove sediment.