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.

本实验探究了红树林幼苗（无瓣海桑，Avicennia marina）与招潮蟹（Uca vocans）对红树林沉积物中碳、铁与硫生物地球化学过程的影响。实验设置4组中型实验生态系统（mesocosms）处理：无蟹有植物组、无蟹无植物组、有蟹有植物组、有蟹无植物组。记录空气与水体温度。通量测定：底栖初级生产力通过淹水沉积物的沉积物-水界面（总CO₂与溶解性有机碳（Dissolved Organic Carbon, DOC）分析）以及干露沉积物的沉积物-空气界面的碳（CO₂）交换量进行测定；测定光照下的产氧量与黑暗中的耗氧量。对沉积物中的厌氧碳氧化与铁呼吸作用进行定量分析。测定孔隙水中总CO₂、溶解性有机碳与Fe²+的浓度。孔隙水提取后剩余的沉积物在氮气氛围下均质化，采用盐酸（HCl）法提取活性Fe(II)。铁还原作用以Fe(II)的生成量进行表征。硫酸盐还原作用采用岩心注入法测定。以叶绿素a浓度作为微藻类丰度的衡量指标。细菌种群计数采样与叶绿素a采样同步进行。
本实验旨在探究红树林根系与蟹类对红树林沉积物中碳、铁与硫生物地球化学过程的影响。