Plastic debris increases circadian temperature extremes in beach sediments

• Published in: Journal of Hazardous Materials
• Main Authors: Lavers, JL, Rivers-Auty, J, Bond, AL
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier Science Bv 2021
• Subjects: Biological Sciences; Ecology; Marine and estuarine ecology (incl. marine ichthyology); Henderson Island
• Online Access: https://doi.org/10.1016/j.jhazmat.2021.126140; http://www.ncbi.nlm.nih.gov/pubmed/34492929; http://ecite.utas.edu.au/144371

Plastic pollution is the focus of substantial scientific and public interest, leading many to believe the issue is well documented and managed, with effective mitigation in place. However, many aspects are poorly understood, including fundamental questions relating to the scope and severity of impacts (e.g., demographic consequences at the population level). Plastics accumulate in significant quantities on beaches globally, yet the consequences for these terrestrial environments are largely unknown. Using real world, in situ measurements of circadian thermal fluctuations of beach sediment on Henderson Island and Cocos (Keeling) Islands, we demonstrate that plastics increase circadian temperature extremes. Particular plastic levels were associated with increases in daily maximum temperatures of 2.45C and decreases of daily minimum by -1.50C at 5 cm depth below the accumulated plastic. Mass of surface plastic was high on both islands (Henderson: 571 197 g/m 2 Cocos: 3164 1989 g/m 2 ), but did not affect thermal conductivity, specific heat capacity, thermal diffusivity, or moisture content of beach sediments. Therefore, we suggest plastic effects sediment temperatures by altering thermal inputs and outputs (e.g., infrared radiation absorption). The resulting circadian temperature fluctuations have potentially significant implications for terrestrial ectotherms, many of which have narrow thermal tolerance limits and are functionally important in beach habitats.