Satellite-Based Analysis of Night-Time Radiance Dynamics in Near-Shore and Offshore Aquaculture Systems in Çandarlı Bay (Northern Aegean Sea, Türkiye)

Öz

Artificial Light at Night (ALAN) has emerged as a growing environmental concern in coastal regions, where marine aquaculture operations coexist with expanding urbanization and tourism infrastructure. This study presents a decadal satellite-based assessment of night-time radiance dynamics associated with marine aquaculture systems in Çandarlı Bay, a semi-enclosed coastal environment in the Northern Aegean Sea, Türkiye. Monthly composites from the Visible Infrared Imaging Radiometer Suite Day/Night Band (VIIRS DNB) were analyzed for the period 2014–2024 to examine long-term trends in relative radiance at offshore and near-shore aquaculture sites, alongside marine and terrestrial control zones. Aquaculture installations were classified into two spatial typologies: a near-shore island-associated cluster and an offshore solitary system. To evaluate aquaculture-related radiance independently from broader coastal illumination, an Aquaculture Light Index (ALI) was developed to quantify radiance contrast relative to a dark-water marine reference. Temporal trends were assessed using STL decomposition, the Mann–Kendall trend test, and Theil–Sen slope estimation. The offshore aquaculture system exhibited no significant long-term trend in relative radiance, indicating a stable nocturnal light signature over the study period. In contrast, near-shore aquaculture sites showed a statistically significant decline in relative radiance contrast, coinciding with increasing night-time brightness in the adjacent terrestrial control area. These findings indicate that observed changes in aquaculture-related radiance are primarily associated with intensifying coastal background illumination rather than progressive increases in farm-level lighting. The study demonstrates the importance of spatial context and background radiance when interpreting satellite-derived ALAN signals in coastal aquaculture environments.

Anahtar Kelimeler

• Artificial Light at Night (ALAN)
• Marine aquaculture
• Night-time radiance
• Satellite-based analysis
• Coastal urbanization

Destekleyen Kurum

This research did not receive any funding.

Etik Beyan

Ethics committee approval was not required for this study because there was no study on animals or humans.

Kaynakça

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