Anastasia Konefal

Seagrasses are foundational species threatened by chronic and acute abiotic stressors. Seagrasses reallocate carbon and alter their physiology to cope with these changes; however, it is unclear whether those responses are coordinated with molecular changes. Molecular and physiological responses related to abiotic change could elucidate their ability to acclimate to current conditions. We hypothesized that seagrass gene expression and physiology are linked to temporal and storm-induced environmental variation. Between February and October 2020, we assessed variation in water quality concurrently with in situ measures of metabolism, photosynthetic efficiency, and gene expression of the seagrass Halodule wrightii in a dynamic northern Gulf of Mexico estuary. The study started 227 d before and finished 38 d after landfall of Hurricane Sally. Irradiance, pH, and dissolved oxygen showed diel patterns of variation, while temperature exhibited diel and seasonal oscillations. Hurricane passage disrupted environmental variability and caused rapid reductions in water quality. Despite this perturbation, most physiological measures did not exhibit consistent patterns of variation across the study. Primary productivity was not affected by hurricane passage. However, effective quantum yield was negatively related to the relative expression of photosynthesis- and stress-related genes, whereas maximum quantum yield was positively related to the abundance of those transcripts. Variation in maximum quantum yield and relative expression of photosynthesis-related genes PsaJ , psbA , and psbD appeared to be driven by poor water quality following the hurricane. Results indicate that major disturbances can trigger seagrass physiological responses via gene expression, improving our understanding of seagrass biology and response to short-term disturbance.

Seagrasses, corals, marsh plants, kelps, and mangroves support valuable coastal ecosystems but are threatened by environmental stressors. The need to manage these foundation taxa has spurred more than a decade of study on the relationship between genetic diversity and function or stability. We synthesized this literature base (129 relevant publications) and found more reported instances of neutral to positive relationships between genetic diversity and function than negative. However, much of the scientific understanding is based on the response of three genera and from unreplicated observational studies that correlate genetic diversity to measured response variables. When a disturbance was present, the studies often lacked controls or baseline data. Only 5.5% of the studies robustly tested for stability. These shortcomings preclude a rigorous evaluation of whether more genetically diverse foundation populations increase stability and hinder the use of genetics-based conservation strategies. Future studies should be focused on diverse species and ecosystem-level impacts using manipulative designs.