Gorgonians, sessile soft corals found globally in reef ecosystems, play a crucial role in providing habitat diversity, supporting fish diversity, and facilitating invertebrate recruitment while sequestering CO2. However, elevated sea surface temperatures (SST) over the past decade as a result of global warming have increased mortality rates in certain Gorgonian species, threatening global Gorgonian populations. Artificial reefs (ARs) offer new substrates that can promote rapid Gorgonian colonization in tropical locations, but it is unclear if these patterns hold in temperate ecosystems. This study focuses on Santa Monica Bay (SMB), adjacent to the largest urban area on the west coast, where significant terrestrial pollution from wastewater, stormwater, and riverine outfalls creates high turbidity conditions, limiting light availability. To investigate Gorgonian colonization patterns in SMB, annual dive survey data from 109 natural and artificial reefs from 2016 to 2023 were analyzed. Depth stratified sampling was conducted across four depth zones: Inner (~5m), Middle (~10m), Outer (~15m), and Deep (~20m). Band transects (30m x 2m) were used to quantify macroinvertebrate and macroalgae species, and uniform point contact (30m) was employed to determine benthic cover, substrate, and reef physical structure. The study revealed that mean Gorgonian density is significantly higher in ARs compared to natural reefs (NR) across SMB and at reefs with high substrate variability. These findings suggest that ARs may provide enhanced habitat conditions conducive to Gorgonian growth and reproduction, underscoring the importance of considering artificial structures in managing temperate reef Gorgonian populations in the face of anthropogenic disturbance. Future investigations will expand the scope of our study to include the entire Southern California Bight as well as explore other biotic factors that might impact Gorgonian abundance.
