Estimating quantities and sources of marine debris at a continental scale

Abstract

Marine debris is recognized as an important global issue that can negatively affect wildlife, habitats, environmental processes, ecosystem services, and human activities including tourism, fishing, and navigation. To improve understanding of the sources and impacts of marine debris, we carried out a national litter survey at 175 sites around Australia using a stratified random sampling approach. Litter from land‐ and sea‐based sources is ubiquitous, and sampling effects related to coastline shape, substrate characteristics, gradient, and backshore type were highly significant. Source effects related to land‐based sources (eg population density and distance to road) were also highly significant. Of the total debris sampled, approximately 75% was plastic; 2% was related to recreational fishing. Litter density significantly increased with proximity to urban areas, suggesting a domestic origin; statistical patterns suggest that illegal rubbish disposal is a major driver. By quantifying debris at a large scales and distinguishing potential litter sources, we can better develop scale‐appropriate solutions to reduce debris inputs to the environment.

Differentiating littering, urban runoff and marine transport as sources of marine debris in coastal and estuarine environments

“…Rubber was recorded separately from plastics, as it is frequently a natural product. To adhere with Hardesty et al 32. foam was also recorded separately from plastics.…”

The physical oceanography of the transport of floating marine debris

“…Another approach is based on the fact that natural sorting and retention of certain type of sediments (sand, granules, pebbles) are observed on coastlines (Reniers et al 2013). The same could be happening with plastic particles: beach characteristics like steepness and sediment type could determine which particles get stranded (Hardesty et al 2017b). For example, surface roughness and the pore size of the beach sediments are likely to be important when plastic objects are pushed on the shore by the wave run-up.…”

Using Numerical Model Simulations to Improve the Understanding of Micro-plastic Distribution and Pathways in the Marine Environment

“…We can also identify movement pathways or trajectories , identify hotspots, and develop scenario analysis tools to identify potential sources and sinks. We can further evaluate effectiveness of local actions and activities (see Hardesty et al, 2016), predict risk of invasion along pathways and evaluate costs of inaction and efficiency of action (Sherman and Van Sebille, 2016).…”

“…Using information from these activities as monitoring information raises a number of issues, as the activities can be idiosyncratic, may have uneven sampling, and frequently do not control sampling effort carefully. Designed surveys can provide much more robust data, however, these are much rarer globally [but see OSPAR (http://www.ospar.org/work-areas/ eiha/marine-litter), CSIRO (http://www.csiro.au/en/Research/ OandA/Areas/Marine-resources-and-industries/Marine-debris; Hardesty et al, 2016), and NOAA's (https://marinedebris.noaa. gov/) approaches].…”