Hypersaline tidal flats (apicum ecosystems): the weak link in the tropical wetlands chain

Abstract

Hypersaline tidal flats (HTFs) are transitional ecosystems commonly occurring in arid and (or) semiarid coastal regions. These ecosystems typically border mangrove forests. Hypersaline tidal flats perform important functions related to the maintenance of coastal biodiversity as well as support socioeconomic and cultural activities in local communities. Despite their importance, HTFs are rarely studied, especially with regard to the understanding of their formation and function. From the premise that the knowledge on the formation of HTF and soil contribute to the understanding of ecological relationships occurring in these ecosystems, a review is presented. Flat topography, coastal dynamics, pronounced hydric deficit, limited frequency, and duration of tidal flooding are the key factors for the formation of these coastal wetlands. The active pedogenetic processes (salinization, gleyzation, sulfidization, and bioturbation) are highly influenced by these factors and present important ecological roles, specifically in regards to carbon and nutrient dynamics. This review presents evidence for the necessity of further studies on the ecological relationships in HTFs, as well as determining the ecological connection between HTFs and other wetlands. Filling this knowledge gap is essential if we are to improve public policies and conservation laws on the protection of all coastal ecosystems.

Wind Power on the Brazilian Northeast Coast, from the Whiff of Hope to Turbulent Convergence: The Case of the Galinhos Wind Farms

“…Chen et al [54] discuss the relationship between maintaining dune shape and their water content, which contributes to the maintenance of groundwater levels. Other studies, such as carried out by Albuquerque et al [55] and Hadlich and Ucha [56], describe the ecological importance of apicuns flat areas, presenting high salinity or acidity, located in the supramarine region and with shallow or no vegetation, present in intertropical regions and associated with mangroves. These are natural protections for the coastal areas and act against erosion, besides being areas used in recycling nutrients and energy [57].…”

General considerations and highlights of low-lying coastal zones: passive continental margins from the poles to the tropics

“…This type has a variety of mangroves, but is dominated by four species with Rhizophora (red mangrove) at the shoreline grading landward into the Avicennia (black mangrove) and inland into Laguncularia (white mangrove) and Conocarpus (bottonwood) zones, bounded landward by marshes, saline in dry areas like Brazil where they are called 'Apicum' (Fig. 19a) with plants such as Salicornia, Sarcorcornia, Suaeda and other Chenopodiaceae, Poaceae and minor Cyperaceae (Albuquerque et al 2014). The other province is the Indo-West Pacific province that has greater variation in flora with an Avicennia-dominated mangal at the shoreline grading landward in arid parts of Australia into a saline marsh with Suaeda and Sarcocornia, bounded landward by a Juncus-Samolus wetland (Fig.…”

Hypersaline tidal flats as important “blue carbon” systems: a case study from three ecosystems

“…These environments are generally located in an intermediary position between mangrove forests or saltmarshes and the terrestrial environment and are common in many tropical arid, and to a lesser extent non-arid, intertidal zones. These systems occur in many regions around the world including northern Australia, Africa, Spain, the Gulf of Mexico and throughout Brazil where they are referred to as apicum ecosystems (Ridd and Stieglitz, 2002;Albuquerque et al, 2013Albuquerque et al, , 2014Soares et al, 2017). In arid and semi-arid estuaries (Ridd and Stieglitz, 2002) or humid tropical supratidal zones with less fluvial contribution (Soares et al, 2017), HTF ecosystems cover an area that exceeds mangrove forests and occupy a substantial proportion of tropical intertidal zones.…”

“…To date, there has been large-scale destruction and degradation of these systems on a global scale as a result of anthropogenic pressures on coastal areas including infilling for urban and agricultural development (Halpern et al, 2008). Although there has been the implementation of various laws in some parts of the world to prevent the loss of coastal vegetated systems, this legislation rarely extends to protect HTFs that are viewed as being ecological deserts with no obvious vegetation (Albuquerque et al, 2013). Furthermore, the landward encroachment of mangrove forests as a response to rising sea levels, coupled to barriers preventing landward migration of HTFs (i.e.…”