The functioning of the ecosystem of the Banc d'Arguin, Mauritania: a review

Abstract

The Banc d'Arguin, Mauritania, is an area of over 10000 km 2 of shallow water and tidal flats between the Sahara and the upwelling system off the Mauritanian coast . The results of the Dutch-Mauritanian project `Banc d'Arguin 1988' as well as the relevant literature are reviewed in order to develop a preliminary conceptual model of the functioning of this ecosystem . Hydrographically the Banc d'Arguin can be characterized as a large-scale negative estuary with higher salinities near the shore . It is concluded that ultimately the Banc d'Arguin ecosystem is fueled by nutrients and organic matter derived from the upwelling area . The inner part of the Banc d'Arguin system is dominated by a detritus-based benthic foodweb in which seagrasses are the principal primary producers . Little of the seagrass production seems to be exported to other parts of the system or other areas . Zooplankton and zoobenthos biomasses are relatively low, but nevertheless support high densities of consumers . Aquatic birds are especially numerous . The study identifies many research topics for the future .

Trophic connectivity between offshore upwelling and the inshore food web of Banc d'Arguin (Mauritania): New insights from isotopic analysis

“…The benthic macrofauna of this area is actively exploited by shorebirds and motile marine predators (Wolff et al, 1993b(Wolff et al, , 2005Ahmedou Salem et al, 2014). Because of this, approximately 12,000 km 2 of shallow water, tidal flats, and adjacent desert have been included in a marine protected area called the Parc National du Banc d'Arguin (PNBA) since 1976.…”

“…However, apart from an exploration of ecological interactions between the entire BA and the upwelling input (Wolff et al, 1993b), the subtidal food web structure of the gulf is poorly known, mainly because scientific cruises to this area have been hampered by its extreme shallowness and poorly described bottom topography. In addition, the high carrying capacity of the BA tidal flat area for wintering shorebirds is still not fully understood (Wolff et al, 1993a;van der Geest, 2013;Ahmedou Salem et al, 2014).…”

“…Notably, resuspended seagrass epiphytes could also contribute to the suspended POM pool in the intertidal part of BA, but given their low biomass, their contribution is expected to generally be low compared to resuspended MPB (Wolff et al, 1993b).…”

“…Trophic enrichment values were adapted from literature values obtained with marine bivalves (Dubois et al, 2007;Yokoyama et al, 2005Yokoyama et al, , 2008 and herbivorous marine invertebrates (Vander Zanden and Rasmussen 2001): 3.7 ± 0.9‰ and 0.7 ± 1.2‰ for N and C, respectively. The model was run only with two sources, suspended POM originating from upwelling and suspended POM from inshore waters, as other potential food sources, such as suspended epiphytic algae, macroalgae, and drifting fragments of mangroves and seagrass, are not abundant at the subtidal part of BA (Wolff and Smit, 1990;Hemminga and Nieuwenhuize, 1991;Wolff et al, 1993b). In addition, MPB were assumed to only be an important primary producer in the seagrass-covered intertidal flat area of BA (Honkoop et al, 2008).…”

Biomass and leaf dynamics of Cymodocea nodosa in the Ria Formosa lagoon, South Portugal

“…Analysis of the genetic structure of the Cymodocea nodosa meadows in Ria Formosa suggested that this population was likely introduced from a single male ''founder'' clone (Alberto et al 2001), which may be derived from either the northern Africa or the Mediterranean meadows. A further peculiarity of Ria Formosa as a habitat for Cymodocea nodosa is that it is a highly productive, nutrient-rich system wnitrate concentrations up to 8.8 mM, phosphates up to 5.6 mM and ammonium concentrations up to 108 mM (Falcã o and Vale 1990)x, whereas all other Atlantic meadows investigated grow in oligotrophic or mesotrophic environments (Wolff et al 1993, Pé rez et al 1994. The growth of Cymodocea nodosa is often nutrient-limited (Pé rez et al 1994), so growth and production in Ria Formosa may be particularly high.…”