Water Column Research Articles

Anthropogenic fibers in the Mediterranean sea: Methods and monitoring of an overlooked category of microparticles in the water column.

Anthropogenic fibers in the Mediterranean sea: Methods and monitoring of an overlooked category of microparticles in the water column.

The control of physical and biological drivers on pelagic methane fluxes in a Patagonian fjord (Golfo Almirante Montt, Chile).

Methane fluxes from coastal waters such as fjords and the underlying control mechanisms are poorly understood. During the austral summer, we investigated a fjord in the Chilean part of Patagonia, the Golfo Almirante Montt. The study is based on measurements of methane concentration, stable carbon isotopes and the distribution and activity of methane-oxidizing bacteria in the water column, as well as oceanographic and geological observations. Our results indicate that methane is of biogenic origin and released from gas-rich sediments at the entrance of the fjord, characterized by pockmarks and gas flares. Tidal currents and turbulent mixing at the sill cause a near-surface methane plume to spread into the main fjord basin and mix with the methane- and oxygen-depleted deep water. Wind-induced mixing at the sea surface controls the methane flux from the plume into the atmosphere. The methane plume is consumed by methanotrophic bacteria of the Methylomonadaceae and Ga0077536 families, which are differently distributed along the water column. An enrichment of the characteristic gene methane monooxygenase (pmoA) in the methane-poor deep water, and a conspicuously high δ13C-CH4 signature suggest that methane-rich intrusions regularly enter the deep water, where the methane is microbially oxidized. Our interdisciplinary study offers a comprehensive insight into the complex physical and biological processes that modulate methane dynamics in fjords and thus help to better assess how methane emissions from these systems will change under anthropogenic influence.

Phosphorus loading in impaired wetlands: The role of temperature and simulated dredging under controlled experimental conditions.

Phosphorus loading in impaired wetlands: The role of temperature and simulated dredging under controlled experimental conditions.

Vigilance against climate change-induced regime shifts for phosphorus restoration in shallow lake ecosystems.

Vigilance against climate change-induced regime shifts for phosphorus restoration in shallow lake ecosystems.

Metabolomic signatures of pathogen suppression effect of Baltic eelgrass meadows in surrounding seawater.

Metabolomic signatures of pathogen suppression effect of Baltic eelgrass meadows in surrounding seawater.

Aquatic deoxygenation associated with resuspension of anthropogenic organic matter.

Aquatic deoxygenation associated with resuspension of anthropogenic organic matter.

Biogeochemistry of phosphorus species in water and sediments and sedimentary phosphorus release potential from a eutrophic estuary and adjacent bay.

Biogeochemistry of phosphorus species in water and sediments and sedimentary phosphorus release potential from a eutrophic estuary and adjacent bay.

Unraveling the role of microplastics in antibiotic resistance: Insights from long-read metagenomics on ARG mobility and host dynamics.

Unraveling the role of microplastics in antibiotic resistance: Insights from long-read metagenomics on ARG mobility and host dynamics.

A comprehensive review of recent advancements and challenges in breakwater oscillating water column technology for wave energy conversion

A comprehensive review of recent advancements and challenges in breakwater oscillating water column technology for wave energy conversion

Oscillating water column wave energy converter with flexible structured sheet material for enhanced power output

Oscillating water column wave energy converter with flexible structured sheet material for enhanced power output

Integrated source identification of particulate and dissolved organic matter related to anthropogenic activities in an artificial lake system.

Integrated source identification of particulate and dissolved organic matter related to anthropogenic activities in an artificial lake system.

Efficient nitrate removal via microorganism-iron oxide co-evolution on biocathode surface.

Efficient nitrate removal via microorganism-iron oxide co-evolution on biocathode surface.

Experimental and numerical investigation of resistive load impact on oscillating water column wave energy converter integrated with a parabolic breakwater

Experimental and numerical investigation of resistive load impact on oscillating water column wave energy converter integrated with a parabolic breakwater

Optimization and machine learning analysis of a small-scale oscillating water column (OWC) in regular waves: A computational study

Optimization and machine learning analysis of a small-scale oscillating water column (OWC) in regular waves: A computational study

Regional restructuring in planktic foraminifera communities through Pliocene-early Pleistocene climate variability

Recent studies highlight asymmetrical range shifts within plankton due to spatial variability in climate change, impacting marine ecosystem functioning and biogeochemical cycling. The Pliocene—early Pleistocene interval, characterized by significant climatic fluctuations, provides a framework to study regional responses of marine organisms, such as planktic foraminifera. Using bipartite network analysis of the Triton database, we investigate biogeographic shifts in macroperforate planktic foraminifera ecogroups, tracking taxonomic diversity and distribution. Here we show high turnover between symbiont-bearing warm-water and high-latitude dwellers, isolated to the North Atlantic, and an expansion of cold-water subthermocline taxa across basins, particularly in the South Pacific. Enhanced water column stratification and nutrient export to mesopelagic depths, associated with the intensification of the Northern Hemisphere Glaciation, likely drove shifts in species diversity and ecogroup latitudinal gradients toward modern patterns. This localized community restructuring emphasizes the importance of regional to hemispheric heterogeneity in understanding biodiversity responses to future climate change.

COMPARISON OF SURF ZONE TURBULENCE AND FLOW STRUCTURES IN SPILLING AND PLUNGING WAVES

Wave breaker generated turbulence and flow fields are a major contributor to sediment suspension and transport, hence a quantitative understanding is critical for predicting coastal erosion. Laboratory and field studies have been carried out in both spilling and plunging waves case to measure these fields, primarily using LDA to measure wave breaker turbulence in non-aerated areas of wave flumes. Although more recent measurement campaigns have included imaging techniques most of the recordings have been confined to below the wave trough due to the presence of wave bubbles higher in the water column. This situation is aggravated in plunging waves, with high levels of aeration through the full water column, especially near the break point. Over the past two decades the authors (Govender et al. (2002a,2002b,2023)) have developed a combination of particle and bubble imaging techniques that allows us to measure fluid velocities through the entire water column, including the wave roller in both spilling and plunging waves. In this paper we undertake a comparison of the flow structures and turbulence between spilling and plunging waves in the surf zone. We present comparative plots of the experimental measurements of mean and turbulent velocities, turbulence kinetic energy, and turbulence shear stress. The paper also discusses the evolution of turbulent intensities at various surf zone locations and levels through the water column over the wave period, which is an important consideration for mathematical modeling of sediment dynamics.

Dual mobilization of buried microplastics and organic carbon driven by seagrass degradation: a case study from Swan Lake, China

Seagrass beds are significant sinks for microplastics. However, the degradation of seagrass beds poses significant challenges, and evidence regarding its impacts on microplastic sinks remains scarce. In this study, sediment cores were collected to investigate microplastic stock and composition, microplastic carbon, and organic carbon stock in Zostera japonica seagrass bed and adjacent degraded area in a lagoon Swan Lake, China. The microplastic stock in seagrass bed (84.5 ± 18.5 million particles ha-1) was found significantly higher than degraded area (51.8 ± 0.6 million particles ha-1), resulting in release of 38.7% of buried microplastics reactivated in water column. Similarly, 30.0% of the microplastic carbon stock and 66.1% of the total organic carbon stock were eroded due to seagrass degradation. The carbon stocks derived from microplastics were estimated at 0.19 ± 0.10 kg C ha-1 in the seagrass bed and 0.13 ± 0.11 kg C ha-1 in the degraded area, contributing minimally to the total organic carbon stock (0.0023% and 0.0026%, respectively). Notably, seagrass degradation within a single year may trigger rapid erosion of organic carbon and microplastics buried for over 20 years in Swan Lake. A linear relationship was observed between sediment microplastic carbon and total organic carbon contents (Organic carbon = 1990 + 35100 × Microplastic carbon, R² = 0.26, p < 0.001). Microplastics in the sediments were predominantly fiber (48.1%), black (40.7%), 250–500 µm (47.0%) microplastics in degraded area, while plate (26.7%), blue and transparent, each contributing 26.7% and 125–250 µm (38.2%) in seagrass bed. Seagrass bed degradation may not only reduce the stock of microplastics in the sediments but also alter their composition. This study initially quantified the contribution of microplastics to organic carbon stocks in seagrass bed sediments and underscored the urgent need for seagrass conservation to mitigate climate change and prevent the remobilization of historically buried microplastics.

CONTINUOUS FIELD MEASUREMENTS OF DUNE SLUMPING DURING STORM SURGES

On sandy coastlines, dunes frequently serve as the main line of defense against coastal storms. During a storm, wind and wave setup result in an increased water or surge level, which submerges the beach, allowing waves to collide with and impact the dune face (van Wiechen et al., 2023a). As a consequence, masses of sediment become unstable and these masses, henceforth called slumps, slide down the dune face. These slumps temporarily defend the dune face until they are suspended in the water column and transported offshore by waves and currents, leaving room for new slumps to slide down. (van Gent et al., 2008). This cycle can persist until waves finally wash over the remaining dune, leading to dune failure. This study presents new data of the dune slumping process collected during the RealDune/REFLEX field experiments.

PREDICTING INSTANTANEOUS SUBSURFACE VELOCITY USING SURFACE VELOCITY

Instantaneous measurements of water velocity at depth in the nearshore are rich with information about orbital velocities, longshore and cross shore currents, and forces that lead to sediment transport. Yet measurements of detailed subsurface velocities are scarce owing to the difficulties involved in installing and maintaining instruments such as acoustic velocimeters in high energy environments like the surf zone [Thornton and Guza, 1986]. Deploying in-situ instruments to measure velocity profiles often involves heavy machinery (e.g. cranes, waterjets, tripods, boats) and after deployment the instruments can be buried, broken, or biofouled owing to strong waves, currents, and biological activity. To address these difficulties, researchers have been developing and improving remote sensing methods capable of measuring wave height, wave period, bathymetry, and surface current velocity, among other useful nearshore parameters [Holman and Stanley, 2007; Brodie et. al., 2018; O’Dea, 2021]. Specifically, Chickadel et. al. [2003] and Holland et. al. [2001] show that cameras and particle image velocimetry (PIV) techniques can be used to accurately measure the velocity at the surface in the surf zone. Here, we build on these recent advances in coastal remote sensing by exploring how remote camera measurements can be used to quantify the relationship between the cross-shore components of instantaneous velocity at the surface and the corresponding velocity at depth in the water column. This work aims to address the question: how well can we use velocity at the surface and linear wave theory to obtain information about velocities at depth in the nearshore?

VARIABLE BATHYMETRY EFFECTS ON THE RESPONSE OF U-OWC WAVE ENERGY CONVERTERS

U-Oscillating Water Columns are wave energy harvesters commonly embedded in port infrastructures. They allow transforming a passive infrastructure (the vertical breakwater) into an active structure serving simultaneously the purpose of creating a sheltered basin and harvesting the incident wave energy for producing electrical energy. This article investigates the effect of bathymetry variability through the combination of a U-OWC dynamic model with a Boundary Element Method (BEM) – based solver accounting for irregular bathymetry. The BEM model used in this work has been applied to classical Oscillating Water Column systems (Belibassakis et al., 2020), which are commonly analyzed in the framework of linear water wave theory (Mei et al., 2005). Herein, its utilization with U-OWCs is pursued in combination with a nonlinear dynamic model accounting for the real flow phenomena (specifically, head losses) and large water column oscillations’ effects.