Stetson Bank long-term monitoring: 2020 and 2021 annual report

This document contains descriptions of the methods used, analyses of field data collected, summaries of field notes, details of challenges faced, and significant observations made during 2020–2021 annual long-term monitoring of fish and benthic communities at Stetson Bank. Stetson Bank is an uplifted claystone/siltstone feature located 130 km southeast of Galveston, Texas within Flower Garden Banks National Marine Sanctuary in the northwestern Gulf of Mexico. It supports a productive benthic community of sponges and coral. Annual monitoring of the bank crest has been conducted since 1993. Surveys of the mesophotic zone surrounding the bank crest began in 2015. Field work and data collection were limited in 2020 and 2021 due to vessel, diving, and operational restrictions established in response to the COVID-19 pandemic. In 2020, a single quarterly water sampling cruise was completed, followed by a cruise for water quality instrument exchange. In 2021, two water sampling cruises were completed, and instruments that recorded temperature, salinity, and turbidity data since 2019 were exchanged. A subset of bank crest repetitive photostations (n = 24), representing 40% of all photostations on the Stetson Bank crest, were captured in 2021. In 2021, mean percent cover was 6.56% for coral, 7.09% for sponges, and 42.72% for macroalgae. Bleaching and/or paling was observed in Millepora alcicornis colonies in 2021; however, no signs of stony coral tissue loss disease were observed. Seawater temperatures on the bank exceeded 30 oC for one day in 2020 and for 18 nonconsecutive days in 2021. This report highlights the importance of long-term monitoring efforts by providing a summary of benthic and water quality trends on the bank crest and detailing challenges and resolutions for future field work.