A different and innovative approach: Identifying the spectral signature of micro-plastics in water has been proved highly challenging. We propose to tackle the problem from another perspective. We will not attempt to identify the presence of micro-plastic itself, but rather the effects of plastic on the microbial environment and, as a consequence, on ocean surface characteristics. Connecting pieces of a puzzle: This project brings together three pieces of research:
- Plastic in the ocean is heavily colonised by microbes;
- Microbes in water produce substances (surfactants) that dampen small waves; and
- Synthetic Aperture Radar (SAR) can identify surfactants as dark areas or stripes in images.
Proof of concept (presented in IGARSS2018 and EO4Atlantic2019): Very recently, we discovered that several Sentinel-1 satellite images acquired over the garbage patches present the same dark features we see in the attached Figure. We have seen similar features in the Atlantic, Indian and Pacific oceans, which are not correlated with high chlorophyll-a. This is a strong indication that they are not produced by phytoplankton.
Our hypothesis is that these dark patches are the signature of micro-plastics. The experiments:
Our experiments will show whether or not plastic-dwelling microbes can produce enough surfactants to be visible from space. We will use aquaculture mesocosms and fish cages in Scotland and submerge plastic in them. We will split mesocosms into test and control samples, where empty mesocosms act as a benchmark against which we will monitor changes in surfactants in the test tanks. A ground radar, ground spectrometer and Sentinel-1 images will be used to check the production of surfactants around mesocosms with and without plastic in it.
