Spatial variation in the morphology of monospecific stands of the western white mangrove Avicennia marina var. Marina in Shark Bay Marine park

© The Government of Western Australia, 2014. Spatial variation in the morphology of mangrove stands could be expected to lead to differences in their ecological role and the ecosystem services they provide. Here we examine spatial variation in the structural morphology of stands of Avicennia marina, the sole mangrove inhabiting Shark Bay, Western Australia—a semi-arid environment with strong regional-scale gradients in the physical environment. Morphological variables were measured at 12 sites across a putative gradient in physical conditions from oceanic (western) to metahaline (eastern) parts of the bay and data were tested using both univariate and multivariate analyses. The multivariate analysis of the combined suite of characters found a significant difference between sites, and pairwise tests revealed significant differences for most comparisons. Changes in morphology across Shark Bay were correlated to longitude, which was used as a proxy for the salinity regime. Three distinct morphotypes associated with different salinity zones were revealed. The results suggest that the morphology of A. marina in Shark Bay varies across regional scales and may be influenced by background physical conditions. It is likely that the functional roles of these mangrove stands differ across the region, and thus, treating stands as uniform ‘units’ may not be appropriate for conservation management. We suggest that the conservation of A. marina could be enhanced by revised management zoning of Shark Bay Marine Park to include representative areas of each of the divergent morphotypes in sanctuary zones or special purpose zones configured for mangrove protection.