Are seaward pneumatophore fringes transitional between mangrove and lower-shore system compartments?

Abstract

Work in temperate New Zealand has concluded that seaward fringes of Avicennia pneumatophores (P) form an 'important ecological transitional environment' between seagrass (Z) and mangrove (M), supporting intermediate macrofaunal numbers and biodiversity (Alfaro, 2006). This study re-examined that hypothesis in subtropical Moreton Bay, Queensland, and investigated its dependence on the nature of the lower-shore habitat; i.e. whether seagrass or sandflat (S). Adjacent macrobenthic assemblages across 45 m deep Z:P:M and S:P:M interfaces were compared uni- and multivariately and via various assemblage metrics. Here, system compartment P was not intermediate. In Z:P:M interfaces it was essentially an extension of the lower-shore assemblage and supported peak biodiversity. In contrast, P in S:P:M interfaces was partly an extension of the upper-shore assemblage with unchanged biodiversity but minimum abundance. Several species spanned the whole interface zone, and assemblage structure and several metrics remained unchanged across it. These findings are discussed in relation to ecotones in general. Like other such zones the characteristics of pneumatophore-fringe ecotones are context dependent.

Context dependency in the effect of Ulva‐induced loss of seagrass cover on estuarine macrobenthic abundance and biodiversity

“…Loss of the seagrass cover along the Steenbok Channel, therefore, appears not to have induced a change in the affected habitat to some degraded state but to one approximating the local natural unvegetated situation; that is, one naturally supporting greater numbers of animals but less species and systematic diversity (Barnes & Barnes, ). The nature and magnitude of green tidal effects can thus clearly be context dependent, as indeed are many ecological phenomena (Barnes, ; Chamberlain, Bronstein, & Rudgers, ; Zwerschke et al, ). Were the Knysna system, like other local sites (Siebert & Branch, ; Whitfield, ), to have possessed more highly contrasting vegetated versus unvegetated benthic habitats consequent on the presence of Callichirus kraussi (Pillay & Branch, ; Pillay, Branch, & Forbes, ), changes induced by the Ulva are likely to have been very much more marked.…”

Changing Ocean, Marine Ecosystems, and Dependent Communities

“…• Responses to future SLR are also uncertain and complex (Kirwan and Megonigal, 2013;Spencer et al 2016). However, impacts are not necessarily negative: carbon sequestration capacity may increase where totally new habitats are created (Barnes, 2017), or if mangroves replace salt marshes (Kelleway et al 2016).…”

Spatial structure of a multi-species guild: the dominant biofilm-grazing microgastropods of seagrass

“…For some species such as Iravadia goliath and Cerithidium diplax their areas of maximum abundance are known to be elsewhere, in the adjacent mangrove (Barnes, 2017c) and sublittoral (Rachello-Dolmen et al, 2013a) respectively, so those in the seagrass can be regarded as stragglers. Others, like Elachisina and Circulus, are presumably genuinely rare in that they are not listed in the checklist of Moreton Bay gastropods (Healy et al, 2010), do not appear in Rachello-Dolmen & Ponder's (2013) list of microgastropods of the region, nor are they shown as occurring there in the Atlas of Living Australia (ala.org.au) 1 .…”