Formation Mechanisms and Characteristics of the Marine Nepheloid Layer: A Review

Abstract

Marine nepheloid layer is widely distributed in the oceans and marginal seas. The concentration of suspended particles in the nepheloid layer is significantly higher than that of the adjacent layers. Marine nepheloid layers include the surface nepheloid layer (SNL), intermediate nepheloid layer (INL), and bottom nepheloid layer (BNL). As a transport pathway for the particulate matter in the oceans, nepheloid layer is important to the carbon cycle and the source–sink system at the continental margin. This paper focused on the characteristics of the marine nepheloid layer and the mechanism of internal solitary waves that form INL and BNL, providing a reference for further research on the marine ecological environment dynamic process and source–sink system. BNL is formed by suspended seabed sediments with strong currents near the bottom, but the fate of BNL remains unknown. Marine nepheloid layer significantly affects the transportation of materials within the ocean. The transport of sediments by ISWs dramatically affects the formation of deep seabed sedimentary landform. However, the formation process and the transport contribution of INL and BNL are still unclear. The systematic and long-term research on the marine nepheloid layer in the world oceans is still limited.

New physical and biological evidence of lateral transport affecting dinoflagellate cyst distribution in the benthic nepheloid layer along a land-sea transect off Figueira da Foz (Atlantic Iberian margin)

“…Results presented herein on physical and cyst data obtained off Figueira da Foz bring new insights into the effect of internal waves on BNL particle distribution with possible influence on the dynamics of cyst producing dinoflagellates, many of which may be nuisance. The West Iberian coast is characterized by seasonal upwelling and high internal wave activity and these results may be of relevance in comparable regions of the world, where the BNL is an ubiquitous feature (Oliveira et al, 2002;Oliveira et al, 2007;Villacieros-Robineau et al, 2019;Tian et al, 2022;Oliveira et al, 2023;and references therein). Internal waves are common in shelf environments and their propagation is favored by stratification of the water column (e.g., Oliveira et al, 2002;Vitorino et al, 2002;Jackson, 2007;Jackson et al, 2012;Lamb, 2014).…”

“…Nepheloid layers (NL) are zones of increased particle concentration (turbidity) and can significantly affect the transport of suspended particulate matter in the ocean (e.g., Oliveira et al, 2002;Zonneveld et al, 2018;Villacieros-Robineau et al, 2019). Benthic nepheloid layers (BNL) are assumed to be formed mainly from seabed particle resuspension, mostly induced by physical processes, such as upwelling/downwelling-induced currents and internal waves (Oliveira et al, 2002;Oliveira et al, 2007;Tian et al, 2022;Oliveira et al, 2023 and references therein). However, the origin and fate of the organic particles that form the NL and their role in the biota distribution are still poorly understood.…”

Sediment Dynamics in Coastal and Marine Environments: Scientific Advances

“…Tian et al [17] explored the characteristics of oceanic nepheloid layers and the mechanism of internal solitary waves that form the middle and bottom layers. Internal solitary waves can cause powerful currents at the bottom, leading to the resuspension of sediments and the formation of the bottom nepheloid layer.…”

Interaction between internal solitary waves and the seafloor in the deep sea

“…It is a catastrophic factor second only to typhoons (Dong et al, 2015), and its important impact on the marine environment has attracted great attention from oceanographers. ISW disturbs seafloor sediments and forms marine nepheloid layers (Geng et al, 2017; Tian, Jia, et al, 2019; Tian, Liu, et al, 2022; Tian, Zhang, et al, 2019). At the same time, ISW transforms the seafloor to form sand waves, which have been extensively observed and studied in marginal seas (Ma et al, 2016).…”