Modeling and Monitoring

The principle purpose of this report is to provide recommendations, advice and practical guidance, for the establishment of programmes to monitor and assess the distribution and abundance of plastic litter, also referred to as plastic debris, in the ocean. The intention is to promote a more harmonised approach to the design of sampling programmes, the selection of appropriate indicators (i.e. type of sample), the collection of samples or observations, the characterisation of sampled material, dealing with uncertainties, data analysis and reporting the results and also to inform the establishment of national and regional field monitoring programmes.

Understanding the movement of debris allows us to have a better grasp on how it might distribute and accumulate within our ocean and on our shores.This report reviews the scientific literature that exists on the subject and outlines the methods that are available to gain this sort of insight.

The following overview presents some of the numerical modeling techniques that have been applied to simulate the transport of marine debris. The primary approach to modeling the transport of drifting objects, with marine debris being one application, typically has involved the use of particle tracking models (PTMs) to estimate or simulate the movement of ‘particles’ over time. This movement depends on transport (advection) by ocean surface currents, and some PTMs may incorporate additional factors such as movement resulting from the proportion of buoyant objects floating high in the water and exposed to the wind (windage), or a random motion component (turbulent diffusion).

One of the most pressing needs when addressing marine debris dispersion caused by a major storm is to assess and verify debris locations. Knowing where high densities of marine debris are likely to be found could greatly assist in developing survey priorities and in planning for debris removal. Moreover, a simple, inexpensive, rapid, and verifiable mode to predict marine debris densities could be very useful to federal and state manages dealing with marine debris. The data collected by this project compromise one of the largest systematically collected, post-storm investigations of marine debris in existence, and provide the building blocks for assembling such a model. This document describes model construction and performance. Citation: Nixon, Z., and N. Barnea. 2010. Development of the Gulf of Mexico Marine Debris Model. January 2010. NOAA Technical Memorandum NOS-OR&R-35.

The NOAA Marine Debris Program has developed standardized, statistically valid methodologies for conducting rapid assessments of the debris material type and quantity present in a monitored location. The monitoring guidelines in this document focus on abundance, types, and concentration rather than analyzing by potential source, as in many cases it is very difficult to connect a debris item to a specific debris-generating activity. These techniques are intended to be widely applicable to enable comparisons across regional and global scales. Citation: Lippiatt, S., Opfer, S., and Arthur, C. 2013. Marine Debris Monitoring and Assessment. NOAA Technical Memorandum NOS-OR&R-46.