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

Trethewy, Megan; Mayer‐Pinto, Mariana; Dafforn, Katherine A.

doi:10.1016/j.marpolbul.2023.115203

Cited by 3 publications

(2 citation statements)

References 75 publications

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“…changes to kelp microbiota [29,30]. While the light intensity used in this study was higher than ALAN levels that currently occur on some shorelines in Sydney Harbour [60], it is still within relevant light levels that can occur directly under infrastructure such as ports and marinas [13]. Additionally, the levels applied here are useful for understanding the mechanisms and future impacts of ALAN, as ALAN is increasing in intensity and extent with growing urbanization and use of LEDs [72].…”

Section: Discussionmentioning

confidence: 86%

“…This light intensity is within the range used by other studies looking at the effects of ALAN on urchins (30 lux [36]; 300 lux [37]). While the lux used here is brighter than ALAN levels measured on some intertidal shores in Sydney Harbour [60], it is within relevant levels of light that can occur directly under infrastructure such as ports and marinas [13]. Importantly, the levels applied here are useful for understanding the mechanisms and potential long-term effects of ALAN [8].…”

Section: (B) Light and Temperature Treatmentsmentioning

confidence: 93%

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Artificial light at night and warming impact grazing rates and gonad index of the sea urchin Centrostephanus rodgersii

Caley,

Marzinelli,

Byrne

et al. 2024

Proc. R. Soc. B.

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Artificial light at night (ALAN) is a growing threat to coastal habitats, and is likely to exacerbate the impacts of other stressors. Kelp forests are dominant habitats on temperate reefs but are declining due to ocean warming and overgrazing. We tested the independent and interactive effects of ALAN (dark versus ALAN) and warming (ambient versus warm) on grazing rates and gonad index of the sea urchin Centrostephanus rodgersii. Within these treatments, urchins were fed either ‘fresh’ kelp or ‘treated’ kelp. Treated kelp ( Ecklonia radiata ) was exposed to the same light and temperature combinations as urchins. We assessed photosynthetic yield, carbon and nitrogen content and C : N ratio of treated kelp to help identify potential drivers behind any effects on urchins. Grazing increased with warming and ALAN for urchins fed fresh kelp, and increased with warming for urchins fed treated kelp. Gonad index was higher in ALAN/ambient and dark/warm treatments compared to dark/ambient treatments for urchins fed fresh kelp. Kelp carbon content was higher in ALAN/ambient treatments than ALAN/warm treatments at one time point. This indicates ocean warming and ALAN may increase urchin grazing pressure on rocky reefs, an important finding for management strategies.

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Section: Discussionmentioning

confidence: 86%

Section: (B) Light and Temperature Treatmentsmentioning

confidence: 93%

Artificial light at night and warming impact grazing rates and gonad index of the sea urchin Centrostephanus rodgersii

Caley,

Marzinelli,

Byrne

et al. 2024

Proc. R. Soc. B.

Self Cite

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Investigating the interactive effects of habitat type and light intensity on rocky shores

Schaefer,

Dafforn,

Johnston

et al. 2024

Oecologia

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Light availability and habitat complexity are two key drivers of community assembly. Urbanisation has been shown to affect both, with important consequences to ecological communities. On the intertidal, for instance, studies have shown that light intensity is greater on natural rocky shores than on less complex artificial habitats (seawalls), though different habitats can also experience similar light intensities, for example when shaded by urban structures. Understanding therefore how these factors individually, and combined, affect communities is important to understand the mechanisms driving changes in community structure, and consequently provide solutions to tackle the increasing homogenisation of habitats and lightscapes in urbanised spaces through smart infrastructure designs. Here, we assessed how different light levels affect the recruitment of communities in rock pools and on emergent rock on an intertidal rocky shore. We cleared 30 patches of emergent rock and 30 rock pools and manipulated light using shades with different light transmissions (full light, procedural control, 75%, 35%, and 15% light transmission, full shade) and assessed mobile and sessile communities monthly for 6 months. Effects of reducing light levels were generally stronger on rock than in pools. Fully shaded plots supported double the amount of mobile organisms than plots in full sunlight, in both habitats. Algal cover was higher in pools compared to rock, and at intermediate light levels, but effects varied with site. This study highlights the importance of variable light conditions and different habitats for rocky shore communities, which should be considered in future coastal developments to retain natural biodiversity.

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Novel high‐throughput oxygen saturation measurements for quantifying the physiological performance of macroalgal early life stages

Veenhof,

Coleman,

Champion

et al. 2024

Journal of Phycology

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Understanding how macroalgal forests will respond to environmental change is critical for predicting future impacts on coastal ecosystems. Although measures of adult macroalgae physiological responses to environmental stress are advancing, measures of early life‐stage physiology are rare, in part due to the methodological difficulties associated with their small size. Here we tested a novel, high‐throughput method (rate of oxygen consumption and production; ) via a sensor dish reader microplate system to rapidly measure physiological rates of the early life stages of three habitat‐forming macroalgae, the kelp Ecklonia radiata and the fucoids Hormosira banksii and Phyllospora comosa. We measured the rate of O2 consumption (respiration) and O2 production (net primary production) to then calculate gross primary production (GPP) under temperatures representing their natural thermal range. The microplate system was suitable for rapidly measuring physiological rates over a temperature gradient to establish thermal performance curves for all species. The microplate system proved efficient for measures of early life stages of macroalgae ranging in size from approximately 50 μm up to 150 mm. This method has the potential for measuring responses of early life stages across a range of environmental factors, species, populations, and developmental stages, vastly increasing the speed, precision, and efficacy of macroalgal physiological measures under future ocean change scenarios.

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

Cited by 3 publications

References 75 publications

Artificial light at night and warming impact grazing rates and gonad index of the sea urchin Centrostephanus rodgersii

Artificial light at night and warming impact grazing rates and gonad index of the sea urchin Centrostephanus rodgersii

Investigating the interactive effects of habitat type and light intensity on rocky shores

Novel high‐throughput oxygen saturation measurements for quantifying the physiological performance of macroalgal early life stages

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