Application of remote sensing to site characterisation and environmental change analysis of North African coastal lagoons

Abstract

This article describes the use of satellite imagery for identifying key environmental characteristics within three North African coastal lagoons (Merja Zerga, Morocco; Ghar El Melh, Tunisia and Lake Manzala, Egypt) and for detecting the major environmental changes within these environments. A combination of Landsat MSS, Landsat TM, Landsat ETM? and ASTER imagery was acquired for the three sites for a period covering the last three decades . Following geometric correction and enhancement, the interpretation of the most recent image acquired for each of the three lagoons provides important insights into their current conditions. For Merja Zerga, these include the distribution of the largest channels which drain extensive inter-tidal mudflats and the two major depositional features associated with sources of freshwater. The distribution of marginal aquatic vegetation is highlighted as is the intensive use of the surrounding landscape for agriculture. Intensive agriculture around Ghar El Melh is also indicated. The influence of the Mejerda River, which was diverted away from the lagoon over 100 years ago, is shown to persist as a residual area of deltaic deposits in shallow water that has been eroded over time. Coastal processes including the direction of the alongshore sediment transport and the influence of engineering work associated with port construction can also be recognised. Within Lake Manzala, vegetated islands divide the lake into a series of sub-basins which can be clearly distinguished. The large influence of human activities within this lake can be identified and include reclamation for agriculture and the conversion of parts of the lake bed for fish farms.works, such as the El Salam Canal and road embankments, are shown to have resulted in significant lake change. The distribution of emergent vegetation within the lake has also changed. Classification of images for this lake into open water, vegetation and land enables the quantification of these changes. Between 1973 and 2003, the lake declined in area by approximately 50%. Changes at Merja Zerga over the last three decades include reconfiguration of the marine outlet and the expansion of the internal delta at the end of the Nador Canal. The images of this site clearly demonstrate the intensification of agriculture around the lagoon. The most marked changes evident within the images of Ghar El Melh concern the sand bars that separate the lagoon from the sea. Geomorphological processes operating within the coastal zone have resulted in the straightening of the bars with central sections migrating out towards the sea. Remote sensing is established as a promising application for detecting the quantitative surface cover changes in coastal lagoons and their near landscapes.

Monitoring temporal changes of the surface water area of the Burullus and Manzala lagoons using automatic techniques applied to a Landsat satellite data series of the Nile Delta coast

“…This result means that the Manzala lagoon has been heavily impacted by eutrophication caused by wastewater from the drainage system and by the drying processes of land reclamation and urban encroachment due to the expansion of the Dameitta governorate to the east of the lagoon. By comparing the results of this study with other studies (AHMED, et al, 2009), there is general agreement in the trend and pattern of shrinkage for the water surface area of Manzala lagoon. The above situation justifies the creation of improvement works to maintain the present area of the lagoon water body without further area loss.…”

“…Their study also indicated that Manzala lagoon has suffered from different levels of eutrophication resulting from human activities and poor management. RAMDANI et al, 2009, stated that zooplankton communities in Manzala lagoon were generally dominated by rotifers and that the planktonic communities were comparatively highly diverse with essentially freshwater species.…”

Physicochemical properties of Manzala Lake, Egypt

“…1) is the largest coastal lake in Egypt which is a shallow brackish lake extending between the Damietta Nile River branch and the Suez Canal with a maximum length of 50 km along the Mediterranean coast [1]. The northern boundary of the lake is connected with some narrow inlets such as El-Gamil canal with the sea.…”

Screening of Bacterial and Fungal Biota Associated with Oreochromis niloticus in Lake Manzala and Its Impact on Human Health

“…It has been gradually transformed from a largely marine or estuarine environment to eutrophic brackish water system. The overall area of the lake was decline from more than 1400 km 2 in the early 1970s to less than 700 km 2 in 2003 [8]. The Lake is considered an important and valuable natural resource ecosystem for fish catch, wildlife, hydrological and biological regime in Egypt.…”