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Spatial-temporal distribution of salinity and temperature in the Oued Loukkos estuary, Morocco: using vertical salinity gradient for estuary classification.

Geawhari MA, Huff L, Mhammdi N, Trakadas A, Ammar A - Springerplus (2014)

Bottom Line: In this case, it is also evident that the morphology of the bottom was capable of impacting the distribution of salinity by locally changing the water circulation.Based on the vertical salinity gradient measurement, the Oued Loukkos represents an estuarine environment with one section near its mouth that can be characterized as a mixed mesotidal estuary and another section upstream which can be characterized as a stratified mesotidal estuary.Between, there is an intermediate zone with a low vertical gradient of salinity, classified as a partially mixed mesotidal estuary.

View Article: PubMed Central - PubMed

Affiliation: Faculté des Sciences Rabat, Département Sciences de la Terre, Université Mohammed V - Agdal, Agdal, Morocco ; Institut Scientifique, Département Sciences de la Terre, Université Mohammed V - Agdal, Agdal, Morocco.

ABSTRACT

Background: Several different classifications to characterize estuarine systems have been proposed. In this present paper, one of the most important estuaries in North Africa, the Oued Loukkos (Morocco), forms a case-study for proposing a systematic classification of this particular tidal estuary according to the vertical salinity gradient.

Findings: This study, conducted using a CTD, shows that the spatial-temporal distribution of salinity depends on the stage of the tide and the upstream distance from the mouth of the river. In this case, it is also evident that the morphology of the bottom was capable of impacting the distribution of salinity by locally changing the water circulation.

Conclusions: Based on the vertical salinity gradient measurement, the Oued Loukkos represents an estuarine environment with one section near its mouth that can be characterized as a mixed mesotidal estuary and another section upstream which can be characterized as a stratified mesotidal estuary. Between, there is an intermediate zone with a low vertical gradient of salinity, classified as a partially mixed mesotidal estuary. When the effect of terrestrial inputs is low compared to marine inputs, the river bed topography plays a role in the stratification of salinity by either disrupting the vertical stratification of the water or by changing the lateral distribution of salinity. The proposed classification deepens our hydrological knowledge and provides descriptive labels to the Oued Loukkos estuary. It provides a valid starting point for predicting the environmental impact of future recreational, agricultural and commercial activities on the estuary.

No MeSH data available.


Salinity stratification recorded during a low stage of tide in the far inland reach of the survey.
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Fig4: Salinity stratification recorded during a low stage of tide in the far inland reach of the survey.

Mentions: In the vertical plane, a gradient of salinity (increasing from lower near-surface values to higher near-bottom values) was generally observed along the study area of the Oued Loukkos. The strength of the gradient varied with the stage of the tide and the distance upstream from the mouth of the river. For example, on 15 October, in the far inland reach of the survey and during an ebbing tide, fresher water was observed overlying more saline water. In this instance, the salinity ranged from 0.7 psu in the near-surface water to greater than 25 psu at a depth of 4 m, with a temperature close to 21°C throughout the entire water column (Figure 4).


Spatial-temporal distribution of salinity and temperature in the Oued Loukkos estuary, Morocco: using vertical salinity gradient for estuary classification.

Geawhari MA, Huff L, Mhammdi N, Trakadas A, Ammar A - Springerplus (2014)

Salinity stratification recorded during a low stage of tide in the far inland reach of the survey.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4233025&req=5

Fig4: Salinity stratification recorded during a low stage of tide in the far inland reach of the survey.
Mentions: In the vertical plane, a gradient of salinity (increasing from lower near-surface values to higher near-bottom values) was generally observed along the study area of the Oued Loukkos. The strength of the gradient varied with the stage of the tide and the distance upstream from the mouth of the river. For example, on 15 October, in the far inland reach of the survey and during an ebbing tide, fresher water was observed overlying more saline water. In this instance, the salinity ranged from 0.7 psu in the near-surface water to greater than 25 psu at a depth of 4 m, with a temperature close to 21°C throughout the entire water column (Figure 4).

Bottom Line: In this case, it is also evident that the morphology of the bottom was capable of impacting the distribution of salinity by locally changing the water circulation.Based on the vertical salinity gradient measurement, the Oued Loukkos represents an estuarine environment with one section near its mouth that can be characterized as a mixed mesotidal estuary and another section upstream which can be characterized as a stratified mesotidal estuary.Between, there is an intermediate zone with a low vertical gradient of salinity, classified as a partially mixed mesotidal estuary.

View Article: PubMed Central - PubMed

Affiliation: Faculté des Sciences Rabat, Département Sciences de la Terre, Université Mohammed V - Agdal, Agdal, Morocco ; Institut Scientifique, Département Sciences de la Terre, Université Mohammed V - Agdal, Agdal, Morocco.

ABSTRACT

Background: Several different classifications to characterize estuarine systems have been proposed. In this present paper, one of the most important estuaries in North Africa, the Oued Loukkos (Morocco), forms a case-study for proposing a systematic classification of this particular tidal estuary according to the vertical salinity gradient.

Findings: This study, conducted using a CTD, shows that the spatial-temporal distribution of salinity depends on the stage of the tide and the upstream distance from the mouth of the river. In this case, it is also evident that the morphology of the bottom was capable of impacting the distribution of salinity by locally changing the water circulation.

Conclusions: Based on the vertical salinity gradient measurement, the Oued Loukkos represents an estuarine environment with one section near its mouth that can be characterized as a mixed mesotidal estuary and another section upstream which can be characterized as a stratified mesotidal estuary. Between, there is an intermediate zone with a low vertical gradient of salinity, classified as a partially mixed mesotidal estuary. When the effect of terrestrial inputs is low compared to marine inputs, the river bed topography plays a role in the stratification of salinity by either disrupting the vertical stratification of the water or by changing the lateral distribution of salinity. The proposed classification deepens our hydrological knowledge and provides descriptive labels to the Oued Loukkos estuary. It provides a valid starting point for predicting the environmental impact of future recreational, agricultural and commercial activities on the estuary.

No MeSH data available.