Dynamics of the Estuarine Turbidity Maximum Zone from Landsat-8 Data: The Case of the Maroni River Estuary, French Guiana

Abstract

<jats:p>The estuarine turbidity maximum (ETM) zone occurs in river estuaries due to the effects of tidal dynamics, density-driven residual circulation and deposition/erosion of fine sediments. Even though tropical river estuaries contribute proportionally more to the sediment supply of coastal areas, the ETM in them has been hardly studied. In this study, surface suspended particulate matter (SPM) determined from OLI (Operational Land Imager)-Landsat 8images was used to gain a better understanding of the spatio-temporal dynamics of the ETM of the tropical Maroni estuary (located on the Guianas coast, South America). A method to estimate the remotely-sensed ETM location and its spatiotemporal evolution between 2013 and 2019 was developed. Each ETM was defined from an envelope of normalized SPM values &gt; 0.6 calculated from images of the estuary. The results show the influence of the well-marked seasonal river discharge and of tides, especially during the dry season. The ETM is located in the middle estuary during low river-flow conditions, whereas it shifts towards the mouth during high river flow. Neap–spring tidal cycles result in a push of the ETM closer to the mouth under spring-tide conditions or even outside the mouth during the rainy season. An increase in SPM, especially since 2017, coincident with an extension of the ETM, is shown to reflect the periodic influence of mud banks originating from the mouth of the Amazon and migrating along the coast towards the Orinoco (Venezuela). These results demonstrate the advantages of ocean color data in an exploratory study of the spatio-temporal dynamics of the ETM of a tropical estuary, such as that of the Maroni.</jats:p>

Habitat protection planning for Indo‐Pacific humpback dolphins (Sousa chinensis) in deteriorating environments: Knowledge gaps and recommendations for action

“…CEME impacts can be amplified by alterations in nearby landscapes and adjacent catchments. Human interventions happening upstream can influence interactions between river discharges and tidal dynamics in the estuary (Yang et al, 2020), which further leads to changes in ETM area and location (Asp et al, 2018; Abascal‐Zorrilla et al, 2020). Along the western coast of Taiwan, Landsat imagery has revealed reduced river flows in summer (Figure 3).…”

“…Ecologically, the ETM area is a major nurturing site of fishes (Whitfield, 2020; Whitfield, 2021) and exports sediments to adjacent ecosystems (Asp et al, 2018). The ETM location is modulated by tidal dynamics and upstream river discharges (Asp et al, 2018; Abascal‐Zorrilla et al, 2020). Seasonal changes in humpback dolphin distributions are associated with seasonal changes in riverine discharges (Jefferson, 2000; Chen et al, 2010; Lin, Akamatsu & Chou, 2015), which could result from the river–tide interaction in the ETM area (Asp et al, 2018; Abascal‐Zorrilla et al, 2020).…”

Sustainable Management, Conservation, and Restoration of the Amazon River Delta and Amazon-Influenced Guianas Coast: A Review

“…In addition to spatially and temporally variable shoreline erosion (inter-bank) and accretion phases (bank), Amazon mud determines the morphology and estuarine dynamics of the numerous smaller Guiana Shield river mouths between the Amazon and the Orinoco [99][100][101]. The migrating mud banks tend to cause a westward deflection of the mouths of the small rivers through more or less prominent capes built from Amazon mud, whereas the larger rivers are characterized by open estuaries but are also significantly influenced by mud intrusion during the dry season when river discharge is low [100]. These aspects imply significant management problems for ports subject to abundant silting [101][102][103].…”

Detection of the Minute Variations of Total Suspended Matter in Strong Tidal Waters Based on GaoFen-4 Satellite Data

“…The study of the inter-annual, annual, and monthly variations of TSM concentration in strong-tidal estuary, gulf, and other sea areas has been widely reported in previous literatures [6][7][8][9][10][11]. Using traditional in-situ measurement, it is difficult to detect the TSM concentration on a timely basis and on a large scale [12,13].…”

“…The satellite can provide global water leaving radiance from the sea surface, so as to provide continuous observation of TSM [11,14]. Early TSM concentration was mostly retrieved by Landsat-x_MSS [6,15], NIMBUS-7_CZCS [16], and SeaStar_SeaWiFs [8,17] satellite sensors. With the progress of optical sensor design technology, the MODIS [18,19], MERIS [9,10,20], sentinel-2A/B [11], sentinel-3_OLCI [21], and VIIRS [22] have been used widely to study the spatial and temporal change trends of TSM concentration in near shore and in large lakes.…”