Rainfall and salinity of a Sahelian estuary between 1927 and 1987

Pagès, Jean; Citeau, Jean

doi:10.1016/0022-1694(90)90182-w

Cited by 70 publications

(60 citation statements)

References 10 publications

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“…The brackish water zone of the River Gambia extends from about 80km in September to more than 220km inland in June, while in the rainy/flood season, at least two-thirds of the estuary becomes totally fresh, oligohaline or mesohaline [25]. Thus, the high seasonal variation recorded in salinities of the rainy and dry seasons during this study is an indication of a negative runoff, which enables seawater to intrude the estuary and become concentrated by evaporation [39].…”

Section: Environment/water Qualitymentioning

confidence: 59%

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Mangrove Vegetation Dynamics of the Tanbi Wetland National Park in The Gambia

Ceesay¹,

Dibi²,

Njie³

et al. 2017

eer

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Changes in mangrove vegetation have been identified as important indicators of environmental deterioration. The mangroves of the Tanbi Wetland National Park (TWNP) connect the Atlantic coast with the estuary of the River Gambia and as such, play an invaluable role in the agriculture, tourism and fisheries sectors of The Gambia. Our research seeks to understand the long-term changes in the mangrove vegetation in order to strengthen the formulation of sustainable alternative livelihoods and adaptation strategies to climate change. Mangrove vegetation dynamics was assessed by remote sensing, using decadal Landsat images covering 1973 -2012. Physicochemical parameters were analyzed during the rainy and dry seasons for correlation with climate data. Our findings indicate that the long-term changes in salinity (24.5 and 35.8ppt) and water temperature (27.6 o C and 30.2 o C) during the rainy and dry seasons respectively are retarding mangrove growth. Mangrove vegetation cover declined by 6%, while grassland increased by 56.4%. This research concludes that long-term hyper-salinity is the cause for the stunted vegetation and lack of mangrove rejuvenation in TWNP. We propose that specialized replanting systems such as the use of saplings be adopted instead of the conventional use of propagules. Alternative livelihoods also need to be diversified to support coastal communities.

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Section: Environment/water Qualitymentioning

confidence: 59%

“…one where rainfall equilibrates evaporation on a yearly basis, so that key variables such as salinity would remain stable between successive years [39]. A lot of research has been done on seasonal variations in the estuaries of the Sahel [39,40,41] and of West Africa as a whole [42,43].…”

Section: Environment/water Qualitymentioning

confidence: 99%

Mangrove Vegetation Dynamics of the Tanbi Wetland National Park in The Gambia

Ceesay¹,

Dibi²,

Njie³

et al. 2017

eer

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“…Total rainfall has been decreasing since the 1920s, with a particularly severe decline since 1961. Combined effects of tides, reduced river run-off, intense evaporation, and shallow waters in the estuary's mouth have led to high salinity and overall inversion of the salinity gradient (Pagès & Citeau 1990).…”

Section: Study Sitesmentioning

confidence: 99%

“…The Sine Saloum estuary is an inverse hypersaline environment with seasonally changing salinities (Pagès & Citeau 1990). In the estuary's middle reaches, water temperatures regularly exceed 30°C and salinity surpasses 50 by the end of the dry season in June/July (Simier et al 2004).…”

Section: Introductionmentioning

confidence: 99%

“…In this regard, the nutritional quality of oocytes, especially in terms of their fatty acid (FA) composition, becomes an important factor in the ontogeny and embryonic development of clupeid fishes in stressful environments (Tocher & Sargent 1984, March 1993, Tocher 2010. Because of a globally changing climate and the possible inversion of estuaries in the dry tropics (Wolanski 1986, Pagès & Citeau 1990, Ridd & Stieglitz 2002, Wedderburn et al 2016, migratory clupeid fish species have to be able to adapt quickly to rapid changes in their spawning habitats to ensure reproductive success.…”

Section: Introductionmentioning

confidence: 99%

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Using oocyte essential fatty acid composition to assess spawner reproductive potential under hypersaline conditions

Döring¹,

Ekau²

2017

Mar. Ecol. Prog. Ser.

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Inversion of estuaries in the dry tropics (i.e. salinity increases upstream) against the backdrop of a globally changing climate is forcing migratory clupeid fish species to adapt quickly to modifications in their spawning habitats to ensure reproductive success. Hatching success and survival probabilities of marine fish eggs and early life stages are prone to impairment under high temperature and elevated salinity conditions. Essential fatty acids affect osmoregulation in marine fish early life stages, and deficiencies can therefore be expected to cause elevated offspring mortality under hyperosmotic conditions, ultimately modifying a stock's reproductive potential. Here we show that oocytes spawned by bonga shad Ethmalosa fimbriata inside a hypersaline estuary exhibited significantly higher 20:4 (n-6) proportions (1.6 ± 0.7% of total fatty acids) than oocytes spawned under marine conditions (0.6 ± 0.2%). Further, oocyte proportions in 20:4 (n-6), 20:5 (n-3), and 20:6 (n-3) were positively correlated with water temperature, water salinity, and female reproductive investment (relative batch fecundity, gonado-somatic index, oocyte dry weight). Oocytes spawned during high temperature/high salinity conditions inside the estuary are therefore likely to develop normally under the prevailing conditions. Reproductive potential was determined to be highest in females spawning inside the estuary at the end of the wet season, when temperatures are high and salinities are less stressful due to freshwater input. Results lead to the conclusion that migratory clupeid fishes can maintain their reproductive potential in hypersaline estuaries and lagoons, which potentially allows for sustainable stock sizes.

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