Hypersalinity: a dramatic change in the hydrology of Sahelian estuaries

Savenije, Hubert; Pagès, Jean

doi:10.1016/0022-1694(92)90087-c

Cited by 57 publications

(29 citation statements)

References 3 publications

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“…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]. The general consensus being that seasonal variations are much more pronounced within the River Gambia estuary [44,28].…”

Section: Environment/water Qualitymentioning

confidence: 99%

“…The increase in atmospheric temperatures, erratic rains and prolonged droughts have led to reduced habitat integrity and lower ecosystem services/functions in many Sahelian estuaries [9] and in many cases, the formation of inverse estuaries [39]. For instance, exponential increase in salinity of the Casamance estuary in Senegal was reported to have completely eradicated Rhizophora mangle stands, while the few Avicennia germinans stands that survived got severely stunted [40].…”

Section: Mangrove Vegetation Dynamicsmentioning

confidence: 99%

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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: 99%

Section: Mangrove Vegetation Dynamicsmentioning

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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“…These factors are significantly correlated with the production of R. mangle. Drought reduces the ecological functions and services of many estuaries and mangroves, inhibiting the production of hypocotyls of R. mangle to exponentially increase the salinity [47,62].…”

Section: Litterfall Production and Phenological Reproductionmentioning

confidence: 99%

Ecophysiological Response of Rhizophora mangle to the Variation in Hydrochemistry during Five Years along the Coast of Campeche, México

et al. 2018

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We evaluated the phenological response and litterfall production of Rhizophora mangle to changes in pore water chemistry over a five-year period (from 2009 to 2014 and 2010 to 2016) along the coast of Campeche, México. Severe drought conditions were recorded in 2009 with a Standardized Precipitation Index (SPI) of −1.5 and again in 2015 with a SPI of −1.16). A precipitation deficit of 22.1% was recorded between 2009 and 2016 ranging from 9.5% in Laguna de Terminos in the south to 64.4% in Los Petenes Biosphere Reserve in the north. Precipitation varied significantly per year (p < 0.001), seasonally (p < 0.001), and between years and seasons (p < 0.001). An interaction was observed in the salinity (p < 0.05), redox potential (p < 0.001), and precipitation (p < 0.001) of the Laguna de Terminos, Rio Champoton, and Los Petenes Biosphere Reserve regions. Significant differences were found between the years in the leaf and propagule production (p < 0.001), and between seasons in production of leaves, flowers, and propagules (p < 0.001). The determining factor in the production of flowers during both the rainy and dry seasons was the salinity, and the determining factors for the production of propagules were the redox potential and salinity. The results of this study suggest a low phenotypic plasticity in R. mangle.

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“…It was shown that the North Atlantic oscillation has the potential to cause regime shifts, including changing dominance of copepod species and leading to declining or low level cod (Gadus morhua) stocks [1,5] in the North and Baltic Seas. Further, droughts were observed to cause hypersalinity in estuaries in the tropics and subtropics with severe ecological consequences [60], or increasing salinities were observed in coastal lakes caused by sea-level rise [61]. Effects of changing abiotic conditions on prey composition and therefore larval fish nutrition and survival and ultimately recruitment are expected to be case-dependent.…”

Section: Discussionmentioning

confidence: 99%

Food-limited growth of larval Atlantic herring Clupea harengus recurrently observed in a coastal nursery area

Paulsen

Clemmesen

Hammer³

et al. 2016

Helgol Mar Res

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Food-limited growth of larval fish, defined as growth rates lower than observed in other habitats or from laboratory experiments at a given temperature, is rarely reported in field studies. This would imply that either larval fishes are living in an environment characterized by plenty of food, that nutritional condition selective mortality (i.e., eliminating the weak) is very strong, or this impression is caused by misinterpretation of data concerning e.g., poor taxonomical resolution of potential prey items, i.e., total potential prey abundance is high, but positively selected food is actually scarce. We analyzed RNA:DNA derived growth rates of herring larvae (Clupea harengus L.) and taxonomically differentiated prey field data of six consecutive spring seasons from the Kiel Canal, an artificial waterway in northern Germany, in order to test if food-limited growth in larval fish can occur recurrently in coastal habitats. In all years analyzed, larval growth rates decreased simultaneously with prey abundance at the end of each larval season. Furthermore, larval growth rates were observed to be lower than mean growth rates observed in another herring larvae nursery area at temperatures above 15 °C. Asymptotic relationships between prey abundance and larval growth rates were observed, further supporting the hypothesis of food-limitation. As larval growth was best explained by the abundance of the numerically dominant calanoid copepod Eurytemora affinis, the paramount importance of the dominant prey item is highlighted. We conclude that food limitation can be a severe and re-occurring issue for larval fish in coastal habitats, and that certain prey items play a crucial role in determining larval growth rates, and therefore potentially recruitment.

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Hypersalinity: a dramatic change in the hydrology of Sahelian estuaries

Cited by 57 publications

References 3 publications

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

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

Ecophysiological Response of Rhizophora mangle to the Variation in Hydrochemistry during Five Years along the Coast of Campeche, México

Food-limited growth of larval Atlantic herring Clupea harengus recurrently observed in a coastal nursery area

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