It’s not all black and white – the effects of substrate brightness on the intertidal communities of seawalls

Substrate brightness can influence colonisation of marine surfaces, but is typically overlooked in the design of marine constructions for ecological co-benefits. Many micro-organisms, invertebrate larvae and algal spores are negatively phototactic, preferentially settling on dark surfaces. Brightness may also influence post-settlement processes in the intertidal by influencing passive warming of substrates, and by influencing the crypsis of organisms susceptible to visually feeding predators.
To inform eco-engineering designs, this study assessed how the brightness of settlement panels influenced biofilm establishment, passive warming of the substrate and microbial and macrobenthic community development on three seawalls in Sydney Harbour, Australia.
Brightness was manipulated using grey-scale customised concrete panels, spanning black, white and three intermediate brightness values matching seawalls constructed of local quarried sandstone and concrete, as well as Hawkesbury sandstone r..., , # It’s not all black and white – the effects of substrate brightness on the intertidal communities of seawalls

Dataset DOI: [10.5061/dryad.dz08kps8f](https://doi.org/10.5061/dryad.dz08kps8f)

## Description of the data and file structure

The study was conducted in Sydney Harbour, New South Wales, Australia, between November 2018 and October 2020. Effects of brightness on benthic community development were investigated using customised concrete panels affixed to three vertical intertidal seawalls, ~9 km from the mouth of the Harbour at: Kurraba Point (33.844564 °S, 151.222579 °E); North Sydney (33.84503 °S, 151.2186 °E); and McMahons Point 33.84899 °S, 151.20553 °E). At all sites, tides were semi-diurnal and of ~1.8 m amplitude, and salinities were close to 35 ppt.

Brightness was manipulated across a greyscale by altering the amount of black oxide in tiles fabricated from white Portland cement. Five brightness levels were established, each described by a mean brightness (B2) value tha..., ,