Corals thriving in dynamic environments may hold key insights into future coral reefs

The coastal waters of Texas have dynamic environmental conditions and are heavily influenced by anthro- pogenic stressors, which are not conducive for corals. However, cryptic coral species (Astrangia poculata and Oculina diffusa) have been documented in this ecosystem, particularly within manmade channels on jetty rocks connecting the Gulf of Mexico and Corpus Christi Bay. This research explored the strategies that these corals utilize to survive with varying fluctuations in environmental conditions. Extensive in-water-field surveys were conducted in Packery Channel over one year to 1) identify observed corals 2) biologically char- acterize observed corals, 3) document environmental variability, 4) quantify zooplankton abundance, and 5) conduct coral tissue stable isotope analyses. Physical environmental data (e.g., turbidity, temperature, salinity, etc.) was measured weekly during each season (e.g., winter, spring, summer, and fall). Additionally, plankton abundance and diversity measurements were assessed within each season at the highest tide and the lowest tide of the full moon cycle. Corals were collected seasonally (total n=64). Results of this work revealed the species present are Astrangia poculata and Oculina diffusa and that these corals utilize both heterotrophy and autotrophy year-round to withstand extreme environmental conditions including large temperature (9.4-31.5°C) and turbidity (0-95.3 NTU) ranges. Stable isotope analyses suggest heterotrophy to be the dominant feeding mechanism year-round and autotrophy secondarily. Specifically, autotrophic contribution is more prominent during the summer and fall seasons than in the spring and winter seasons which correlates with the environmental data fluctuating the least in the summer and fall. Understanding the nutritional sources of corals in extreme environmental conditions could provide insights into potential phenotypic plasticity and adaptability to anthropogenic influence. Therefore, corals thriving in dynamic environments could provide researchers with the insight they need to understand coral adaptation amid rapidly changing environmental conditions.