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Abstract This study examines the annual cycle of the Surface Energy Budget (SEB) in the Beaufort‐Chukchi seas, focusing on the autumn transition. Shipboard measurements from NASA's Salinity and Stratification at the Sea Ice Edge (SASSIE) experiment (8 September–2 October 2022) and satellite flux analysis for the entire 2022 were utilized to provide a comprehensive perspective of the SEB's seasonal dynamics. An important finding is the alignment of SEB’s autumnal transition with the September 22 equinox, marking the onset of prolonged Arctic darkness. This transition involved a shift from the summertime radiative heating to cooling conditions, characterized by outgoing longwave radiation surpassing incoming solar radiation and a notable increase in synoptic turbulent latent and sensible heat flux variability. The increased turbulent heat fluxes after the equinox were associated with increased occurrences of short‐duration cold air outbreaks. These outbreaks seem to originate from cold mesoscale surface winds transitioning from cooling landmasses or ice caps to the warmer seas, driven by differential cooling rates between land/ice and ocean as solar irradiance declined. Turbulent heat losses, outpacing longwave emission by more than fivefold, accelerated ocean surface cooling in the subsequent 2 months, leading to the complete freeze‐up of the Beaufort‐Chukchi seas by late November. These findings underscore the substantial influence of astronomical seasons on the SEB, emphasizing their crucial role in Arctic climate dynamics. 

The settlement of coral larvae is an important process which contributes to the success and longevity of coral reefs. Coral larvae often recruit to benthic structures covered with crustose coralline algae (CCA) which produce cues that promote settlement and metamorphosis. The PeysonneliaceaeRamicrustaspp. are red-brown encrusting alga that have recently become abundant on shallow Caribbean reefs, replacing CCA habitat, overgrowing corals and potentially threatening coral recruitment. In order to assess the threat ofRamicrustato coral recruitment, we compared the survival and settlement ofPorites astreoidesandFavia fragumlarvae to 0.5 – 2 mg ml^-1solutions ofRamicrustasp. or CCA as well as sterile seawater (control). In all cases larval mortality was extremely high in theRamicrustatreatments compared to the CCA and control treatments. We found 96% (± 8.9% standard deviation, SD) mortality ofP. astreoideslarvae when exposed to solutions ofRamicrustaand 0 - 4% (± 0 - 8.9% SD) mortality in the CCA treatments. We observed 100%F. fragumlarval mortality when exposed toRamicrustaand 5 – 10% (± 10 – 20% SD) mortality in the CCA treatments. Settlement or surface interaction of larvae in the CCA treatments was 40 - 68% (± 22 - 37% SD) forP. astreoidesand 65 - 75% (± 10 - 19% SD) forF. fragum. TwoP. astreoideslarva that survivedRamicrustaexposure did settle/surface interact, suggesting that some larvae may be tolerant toRamicrusta. These results suggest thatRamicrustais a lethal threat to Caribbean coral recruitment.