Artificial Crab Burrows Facilitate Desalting of Rooted Mangrove Sediment in a Microcosm Study

Water uptake by mangrove trees can result in salt accumulation in sedimentaround roots, negatively influencing growth. Tidal pumping facilitates salt release and canbe enhanced by crab burrows. Similarly, flushing of burrows by incoming tidal waterdecreases sediment salinity. In contrast to burrows with multiple entrances, the role of burrowswith one opening for salinity reduction is largely unknown. In a microcosm experiment westudied the effect of artificial, burrow-like macro-pores with one opening on the desalting ofmangrove sediment and growth of Rhizophora mangle L. seedlings. Sediment salinity,seedling leaf area and seedling growth were monitored over six months. Artificial burrowsfacilitated salt release from the sediment after six weeks, but seedling growth was notinfluenced. To test whether crab burrows with one opening facilitate salt release in mangroveforests, sediment salinities were measured in areas with and without R. mangle stilt roots inNorth Brazil at the beginning and end of the wet season. In addition, burrows of Ucidescordatus were counted. High crab burrow densities and sediment salinities were associated with stilt root occurrence. Precipitation and salt accumulation by tree roots seem to have alarger effect on sediment salinity than desalting by U. cordatus burrows