Microplastics can be a major health risk to seabirds such a this Shy Albatross. SOI/Randall Lee
Invisible Risk
The direct nutritional effects of ingested microplastics on organisms such as seabirds and their chicks has become a familiar story. Lesser known, but potentially equally as important, is that the surface of microplastics present a new substrate in the ocean, which can be rapidly colonized by a complex community of microorganisms. Microplastics in the environment also act as a sponge, by absorbing numerous persistent organic pollutants and heavy metals, that can be many times greater than ambient concentrations. As such, ingested microplastics can pose a significant pollutant exposure risk to aquatic organisms, with pollutant concentrations accumulated up the food chain. The RMIT researchers wish to expand the limited knowledge of the complex microbial-ecological interactions that occur on plastic surfaces, that will influence the bioavailability, toxicity and subsequent release of plastic co-pollutants into aquatic fauna.
Bacterial cells (~1.5 mmlong) attached to polyethylene microplastics in U.K. coastal marine sediments. Harrison et al. BMC Microbiology 2014 14:232 doi:10.1186/s12866-014-0232-4
How much is out there?
Concentrations of microplastics in the oceans wildly vary. A recent study in the North Pacific found they ranged from 8 to 9200 particles /m3 (Deforges et al 2014). In the Tasman Sea scant studies have been done, though at lower latitudes Reisser et al. (2012) found that concentrations vary from 500 to 3500 pieces per km2.
Using Falkor’s autonomous sampling system, water is initially passed through a 5mm strainer, before filtering with a 250 micron mesh to capture microplastic samples. Each sample will represent 10hrs of filtering accounting for ~12000L or 1.2m3 volume. These 10 hr samples will be taken throughout the cruise at key locations associated with the companion biological sampling by Dr. Peter Strutton.
Filtering microplastics from the outflow of the Falkor’s autonomous surface sampling system. SOI/Randall Lee
The plastic journey…
Each individual plastic fragment present within the marine environment will have been subject to complex dynamic changes in its biofilm community (microscopic organisms that produce a film on the plastic surface).
During a myriad of divergent routes that transition across and between the terrestrial, freshwater and marine environment, each plastic fragment may develop into a unique environmental microhabitat, shaped by travel through differing physical–chemical environments. Adsorption of organic and inorganic chemicals and by colonization of diverse microorganisms produces a sort of fingerprint of their journey. For the region Falkor is operating in, drifter tracks shown in the figure indicate source areas are predominately associated with the East Australian Current system, though some originate from the Indian Ocean and beyond.
Drifters released (asterisks) and pathways relative to Tasman Sea sampled stations (purple) (Adapted from Reisser et al, 2014).
The microplastics being collected by Falkor will be passed onto Slobodanka and Mark to further their investigations into the local microbial community, and general observations of the plastics collected shared with others studying the regional microplastics community. Hopefully, enough data will eventually be collected to provide information to policy makers and resource managers.
– Randall Lee, Falkor
The Tasman Tidal Dissipation Experiment//Supported by the National Science Foundation