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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.


Vertical profiles of temperature and salinity recorded on 19 October during a CTD cast taken near the predicted time of a mid-flood tide at the mouth of the Oued Loukkos.
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Fig2: Vertical profiles of temperature and salinity recorded on 19 October during a CTD cast taken near the predicted time of a mid-flood tide at the mouth of the Oued Loukkos.

Mentions: The temperature of the water in the estuary decreases with depth, however, only marginally. At both low and high stages of the tide, the difference in water temperature between the near-surface and near-bottom rarely exceeded 1°C. Figure 2 presents temperature and salinity profiles measured near mid-flood tide on the morning of 19 October at the mouth of the river. The character of the temperature and salinity profiles in the upper 6 m of the water column is consistent with their having recently been a surface influx of fresh water into the system which mixed with the more saline underlying water. The lowest salinity in the figure was measured at 0.27 m depth and it is possible that in the upper 2 decimeters of the water column, there may be waters whose salinities are slightly lower than any of the measured values presented in the figure.Figure 2


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)

Vertical profiles of temperature and salinity recorded on 19 October during a CTD cast taken near the predicted time of a mid-flood tide at the mouth of the Oued Loukkos.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig2: Vertical profiles of temperature and salinity recorded on 19 October during a CTD cast taken near the predicted time of a mid-flood tide at the mouth of the Oued Loukkos.
Mentions: The temperature of the water in the estuary decreases with depth, however, only marginally. At both low and high stages of the tide, the difference in water temperature between the near-surface and near-bottom rarely exceeded 1°C. Figure 2 presents temperature and salinity profiles measured near mid-flood tide on the morning of 19 October at the mouth of the river. The character of the temperature and salinity profiles in the upper 6 m of the water column is consistent with their having recently been a surface influx of fresh water into the system which mixed with the more saline underlying water. The lowest salinity in the figure was measured at 0.27 m depth and it is possible that in the upper 2 decimeters of the water column, there may be waters whose salinities are slightly lower than any of the measured values presented in the figure.Figure 2

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.