Impacts of nitrogen on avicennia propagule survival in the presence of UCA




Peterson, Jessica
Devlin, Donna J.
Proffitt, C. Edward
Feller, Ilka C.

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In Winter 2021, Uri brought historically low temperatures to Texas. Avicennia germinans mangrove popula- tions in the salt marsh/mangrove ecotone were heavily impacted; damage varied from loss of exterior canopy leaves in Boca Chica, to death of above ground tissue in many shrubs as far south as Laguna Atascosa. There has been some above ground biomass recovery, but mangrove population density is drastically reduced and at many sites, there has been no recovery of adults. Recolonization of Avicennia will require establishment by the propagule life stage. Both biotic and abiotic factors and their interactions will play an important role in recovery. In general, Uca (fiddler crabs) are considered to have a facilitative relationship with Avicennia, burrowing oxygenates sediment in the rootzone of trees/shrubs. Herbaceous salt marsh species facilitate establishment and growth of mangroves in Florida and Belize. However recent findings indicate that in the unique Texas arid salt marsh habitat, Uca bury many of the Avicennia propagules that strand within the protective salt marsh habitat. Avicennia propagules consist of photosynthetic cotyledons that remain above the sediment and an embryonic root that anchors in the sediment. Burial often results in mortality of propagules and newly established seedlings. In contrast, nitrogen increases growth in height and leaf production in Avicennia seedlings in salt marsh ecotones. Understanding how Uca and soil nutrients impact propagule establishment will help us to predict the rate of recovery of Avicennia in Texas. We will study the direct effects and interactions of Uca and nitrogen on Avicennia propagules that strand in the salt marsh ecotone in a fully crossed experiment. We hypothesize that 1) a greater percentage of propagules will survive and establish when Uca when is excluded 2) nitrogen will allow for greater survival and establishment of propagules and 3) nitrogen will ameliorate the negative effect of Uca.



disturbance, species interaction, eutrophication



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