Abstract
The suspended sediment contribution arising from the bioturbation activity of Neohelice granulata at intertidal sites of the Bahía Blanca estuary was analysed using several approaches, ranging from field experiments to numerical modelling. Crabs from the mudflat remove, trap and erode more sediment from their burrows per unit area than those from saltmarshes, as a consequence of the high population density and the mobility of cohesive sediments. The results obtained through the MOHID simulations showed that the sediments that were bioavailable in the intertidal of Puerto Cuatreros were maintained in the water column much longer than sediments in Villa del Mar. This longer residence time in the area could be because of the geomorphological and hydrodynamic characteristics of the internal area of the estuary, where numerous tidal channels coexist and phenomena of “retention” occur before entry into the main channel. By contrast, in Villa del Mar, located in the middle of the estuary, the sediments are affected by a greater water depth and higher tidal current speeds. In addition, the waves caused by the winds can be a determining factor in the spatio-temporal evolution of the bioavailable sediment in the water column of the study areas.
Highlights
Sediment dynamics is an important aspect to be considered in studies of water quality and problems related to the engineering of coastal areas, estuaries and lagoons
Considering the sediment from biogenic mounds in 1 m2, no significant differences were found among the microhabitats analysed
Neohelice granulata has usually been classified as an ecosystem engineer due to its great burrowing activity and its potential effect on intertidal sediment characteristics
Summary
Sediment dynamics is an important aspect to be considered in studies of water quality and problems related to the engineering of coastal areas, estuaries and lagoons. The burrowing crab Neohelice granulata (Dana 1851) is a semi-terrestrial species of tropical and subtropical estuaries of South America, ranging from the San José Gulf (42°25'S, 64°36'W) in northern Patagonia, Argentina, through Uruguay to Lagoa Araruama, Rio de Janeiro, Brazil (22°57'S, 42°50'W). This bioturbator crab builds elaborate and stable burrows in the intertidal during low tides, giving a special physiognomy to the regions where they are found (Spivak 2010). Neohelice granulata plays a key ecological role in estuaries as an ecosystem engineer, by making changes in the physical environment that strongly affect other organisms, since their absence or presence has a disproportionate impact on the ecosystem (Kristensen 2008)
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