Urban shading and artificial light at night alter natural light regimes and affect marine intertidal assemblages

Megan Trethewy, Mariana Mayer-Pinto*, Katherine A. Dafforn

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)
69 Downloads (Pure)

Abstract

Urban development in many coastal cities has resulted in altered natural light regimes, with many coastal habitats being artificially shaded during the daytime by built structures such as seawalls and piers, while artificial light emitted from buildings and associated infrastructure creates pollution at night. As a result, these habitats may experience changes to community structure and impacts on key ecological processes such as grazing. This study investigated how changes to light regimes affect the abundance of grazers on natural and artificial intertidal habitats in Sydney Harbour, Australia. We also examined whether differences in patterns of responses to shading or artificial light at night (ALAN) varied across different areas within the Harbour, characterised by different overall levels of urbanisation. As predicted, light intensity was greater during the daytime on rocky shores than seawalls at the more urbanised sites of the harbour. We found a negative relationship between the abundance of grazers and increasing light during the daytime on rocky shores (inner harbour) and seawalls (outer harbour). We found similar patterns at night on rocky shores, with a negative relationship between the abundance of grazers and light. However, on seawalls, grazer abundances increased with increasing night-time lux levels, but this was mainly driven by one site. Overall, we found the opposite patterns for algal cover. Our findings corroborate those of previous studies that found that urbanisation can significantly affect natural light cycles, with consequences to ecological communities.

Original languageEnglish
Article number115203
Pages (from-to)1-12
Number of pages12
JournalMarine Pollution Bulletin
Volume193
Early online date29 Jun 2023
DOIs
Publication statusPublished - Aug 2023

Bibliographical note

Copyright the Author(s) 2023. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Keywords

  • ALAN
  • Artificial structures
  • Coastal habitats
  • Grazing
  • Light pollution
  • Rocky shores
  • Shading
  • Sydney Harbour
  • Urban

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