Edinburgh Napier University

  Water uptake by mangrove trees can result in salt accumulation in sediment
around roots, negatively influencing growth. Tidal pumping facilitates salt release and can
be enhanced by crab burrows. Similarly, flushing of burrows by incoming tidal water
decreases sediment salinity. In contrast to burrows with multiple entrances, the role of burrows
with one opening for salinity reduction is largely unknown. In a microcosm experiment we
studied the effect of artificial, burrow-like macro-pores with one opening on the desalting of
mangrove sediment and growth of Rhizophora mangle L. seedlings. Sediment salinity,
seedling leaf area and seedling growth were monitored over six months. Artificial burrows
facilitated salt release from the sediment after six weeks, but seedling growth was not
influenced. To test whether crab burrows with one opening facilitate salt release in mangrove
forests, sediment salinities were measured in areas with and without R. mangle stilt roots in
North Brazil at the beginning and end of the wet season. In addition, burrows of Ucides
cordatus 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 a
larger effect on sediment salinity than desalting by U. cordatus burrows.