Buoyant Debris Research Articles

Abundance of Marine Macrodebris on the Northern Coast of Jaffna Peninsula, Sri Lanka.

Marine plastic debris has emerged as a pressing concern along the northern coast of Jaffna, Sri Lanka, posing a significant threat to marine resources. A preliminary study was conducted to investigate the abundance and characteristics of marine plastic debris at four major fish landing sites in the northern coast of Jaffna, using the Clean Coast Index (CCI) and Plastic Abundance Index (PAI). The results revealed that the average abundance of marine debris and plastic debris were 1.71 ± 0.42 items/m2 and 1.66 ± 0.57 items/m2, respectively. The most common types of plastic debris represented plastic rope and net pieces (23.2%), followed by unidentified weathered plastic fragments (16.7%), beverage bottles (16.2%), bottle caps and lids (13%), and styrofoam (14.1%). The recognized sources of plastic debris were mainly fishing-based activities, recreation activities, transboundary sources, and unidentified sources. The fish landing sites were classified as exceptionally polluted, with a CCI exceeding 10 and a PAI value exceeding 8. Myliddy had the highest debris density, indicating substantial pollution levels, followed by Point Pedro, Mathagal, and Valveddithurai. These findings underscore the urgency of establishing a comprehensive plastic waste management framework for the northern coast of Jaffna and devising strategies to address buoyant debris within the northern Indian Ocean. Furthermore, this study carries significant implications for the local marine ecosystem, coastal communities, and Sri Lanka's broader environmental policies and practices.

Marine debris provide long-distance pathways for spreading invasive corals

Anthropogenic marine debris and invasive species are pervasive in the ocean. However, research on the mechanisms and dynamics controlling their distribution in marine systems (e.g.; by floating debris acting as vectors for invasive species) is limited. Applying a numerical modeling approach, we demonstrate that rafting invasive corals (Tubastraea spp.) can be transported over long distances and reach important tropical receptor regions. In <180 days, buoyant debris can cover distances between 264 and 7170 km moving from the Brazilian semiarid coast to the Amazon coast and reaching eight regions in the Wider Caribbean (mainly the Eastern Caribbean and Greater Antilles). Analyzing 48 simulated scenarios (4 years × 3 depths × 4 months), we demonstrate that in ~86 % of the scenarios the particles are stranded in the Caribbean and in ~71 % they end up in the Amazon coast. Our results showed litter floating trajectories at 0–10 m water depth, transported every year to the Caribbean province. However, in August this transport is frequently blocked by the retroflection of the North Brazil Current adjacent to the Amazon River estuarine plume. Our results indicate routes for fast and long-distance transport of litter-rafting invasive species. We hypothesized a high risk of bioinvasion on important marine ecosystems (e.g., coral reefs) likely becoming increasingly threatened by these invasive species and debris. This highlights the imperative need for an ocean governance shift in prevention, control, and eradication, not only focused on local actions to prevent the spread of invasive species but also a broad international action to decrease and mitigate marine debris pollution globally.

Beaching model for buoyant marine debris in bore-driven swash

Marine debris pollution is a growing problem impacting aquatic ecosystems, coastal recreation and human society. Beaches are known to be a sink for debris, and beaching needs to be accounted for in marine debris mass balances, but the process of buoyant debris beaching is not yet sufficiently well understood in order for it to be included in coastal models. We develop a simplified model for buoyant marine debris transport in bore-driven swash (where swash refers to the area that the water wets the beach with each incoming wave). We validate the model with laboratory experiments and use the combined results from the model and experiments to understand the parameters that are important for dictating particle beaching. The most relevant parameters are the particle inertia and the initial conditions with which debris particles enter the swash zone.

Role of Indian Ocean Dynamics on Accumulation of Buoyant Debris

AbstractBuoyant marine plastic debris has become a serious problem affecting the marine environment. To fully understand the impact of this problem, it is important to understand the dynamics of buoyant debris in the ocean. Buoyant debris accumulates in “garbage patches” in each of the subtropical ocean basins because of Ekman convergence and associated downwelling at subtropical latitudes. However, the precise dynamics of the garbage patches are not well understood. This is especially true in the southern Indian Ocean (SIO), where observations are inconclusive about the existence and numerical models predict inconsistent locations of the SIO garbage patch. In addition, the oceanic and atmospheric dynamics in the SIO are very different from those in the other oceans. The aim of this paper is to determine the dynamics of the SIO garbage patch at different depths and under different transport mechanisms such as ocean surface currents, Stokes drift, and direct wind forcing. To achieve this, we use two types of ocean surface drifters as a proxy for buoyant debris. We derive transport matrices from observed drifter locations and simulate the global accumulation of buoyant debris. Our results indicate that the accumulation of buoyant debris in the SIO is much more sensitive to different transport mechanisms than in the other ocean basins. We relate this sensitivity to the unique oceanic and atmospheric dynamics of the SIO.

Flow convergence at the tip and edges of a viscous swash front — Experimental and analytical modeling

The details of flow at the tip of a viscous swash front are important to describe the propagation of the wave, the bed shear and to estimate material transport rates and impact forces. This paper presents novel experimental data illustrating the convergence of fluid at swash fronts generated by dam-break flows. Very viscous fluids (detergents) were used to slow the flow sufficiently to enable video tracking of particles on the free surface and within the interior of the flow. The experiments were performed both up a slope and on a horizontal bed. The particle tracking shows that surface particles travel faster than the mean flow, converge on the swash tip and then rapidly decelerate, a process that will induce a high bed shear stress at the swash tip as observed in recent experiments. Particles also converge on the wall boundaries because of the no-slip condition. A simple analytical model is developed to estimate the ratio of the velocity of surface particles and the wave front. For laminar flows, this ratio is found to be 3/2, independent of the bed slope and flow depth, and is in good agreement with the experimental data. The same model approach suggests a ratio of 8/7 for turbulent flows. This flow convergence does not appear to be included in either analytical modeling of the tip region or in basal resistance laws for the swash front and would modify the momentum equation at the swash tip [c.f. Hogg and Pritchard, 2004] and the kinematic boundary condition at the shoreline. The flow convergence is consistent with observations of the behavior and build-up of buoyant debris at the leading edge of tsunami wave front and can be observed in natural swash flows on beaches.

Impact of nondegradable marine debris on the ecology and survival outlook of sea turtles

Sea turtles of all kinds are peculiarly prone to eat plastic scraps and other buoyant debris and to tangle themselves in lines and netting discarded by fishermen, and records of such mishaps have increased markedly in recent years. Advances in our understanding of the developmental ecology of sea turtles shed new light on the impact of buoyant wastes on the juvenile stages. The initial developmental stages of all species are passed in the open sea. In the case of the loggerhead Caretta this period of pelagic life is likely to include 3–5 years of planktonic open-ocean travel, which may involve multiple transatlantic crossings. During this time both the young turtles and their buoyant food are drawn by advection into fronts (convergences, rips, driftlines) and the same process also brings in and aligns persistent plastics and lost fishing gear. This effect exacerbates survival problems for sea turtles that are dependent on driftlines for their food supply or shelter.

THE SETTLEMENT OF POST LARVAL MYTILUS EDULIS (SETTLEMENT OF POST LARVAL MUSSELS)

It is probable that post larval mussels cut their byssus moorings. For those that gain their freedom in this way, two modes of passive flotation are possible. In the ‘summer’ mode, they are lifted into the water column on the end of a mucus filament; in the ‘winter’ mode, they attach themselves to certain negatively buoyant debris which leaves the bottom when the tide flows. Passive flotation prolongs the errant existence of post larval mussels by increasing their drag. By enabling them to avoid silt and keep in touch with hard substrates, passive flotation makes it more likely that they will settle advantageously. The two modes of passive flotation pose an all-the-year-round threat of fouling to the cooling water systems of coastal power stations.