Studies of acoustic propagation in seagrass meadow environments have demonstrated a high degree of sensitivity of passive and active acoustics to diurnal photosynthetic cycles and seasonal growth patterns. While empirical metrics based on these measurements in combination with traditional ecological monitoring methods provide insight into trends in primary productivity, estimates of seagrass biomass and other ecological condition indicators have not yet been calculated directly from acoustic measurements. Towards this goal, an acoustic inference was developed utilizing a Bayesian framework to infer estimates of seagrass biomass. This work was based on active acoustic measurements collected over the course of a 25-month remote monitoring experiment conducted in a seagrass meadow in a shallow-water sub-tropical estuary. A ray-based acoustic propagation model was developed to incorporate effects of the seagrass leaf canopy and model parameter estimates related to the height and leaf density of the canopy are used to predict above-ground seagrass biomass over the course of the experiment. The study found biomass to be consistent with seasonal trends found in previous measurements. Comparison of acoustic estimates with an 11-month record of direct measurements of biomass shows good agreement, demonstrating the potential of acoustic inversion to facilitate acoustic-based ecosystem monitoring in seagrass meadow environments.

Read Here: https://doi.org/10.1121/10.0041880

Oxygen ebullition is typically ignored in long-term measurements of net ecosystem productivity (NEP), which reflects whether systems are net heterotrophic or autotrophic based on diel changes in oxygen. The solubility of oxygen in seawater is a function of temperature, salinity, and pressure. Warm, high-salinity seawater has low oxygen solubility, and when combined with the photosynthetic productivity of macrophytes in shallow, clear waters, oxygen ebullition frequently occurs. The presence of mixed-phase oxygen in supersaturated seawater creates difficulties for oxygen measurements because sensors cannot measure dissolved and gas phases simultaneously. Therefore, dissolved oxygen measurements must be taken in conjunction with separate ebullition measurements to develop an accurate oxygen budget needed to characterize NEP. Here, we seek to understand the drivers of NEP for a Thalassia testudinum meadow in the Gulf of Mexico and calculate ebullition rates using acoustic sensing. We hypothesize that oxygen ebullition will substantially increase NEP, particularly during the summer months because of photosynthetic dependence on temperature and irradiance. We found that the seagrass meadow is typically oxygen saturated during the hours 0700 to 2200 with maximum saturation occurring at 1400. Acoustic-based methods and general additive modeling both found highest ebullition rates in July/August. High respiration led to an apparent net heterotrophic system (NEP = −2.1 mmol O₂ m⁻² d⁻¹), but accounting for air–sea exchange and ebullition causes the system to be autotrophic (NEP = 54 mmol O₂ m⁻² d⁻¹). This study demonstrates the importance of including ebullition into NEP calculations and the viability of acoustics as a tool for monitoring aquatic productivity.

Read more here: https://spj.science.org/doi/10.34133/olar.0087

Read our recent paper, Ballard et al. (2024) that details the usage of acoustics to monitor seagrass meadows!

Kyle Capistrant-Fossa and Ken Dunton recently wrote a manuscript linking the decline of seagrasses in Upper Laguna Madre to rapid sea level rise. It is currently under review, but if you want to get an early sneak peek, you can check it out here: https://www.researchsquare.com/article/rs-3168298/v1

NatureServe, in partnership with USGS Wetland and Aquatic Research Center, The Nature Conservancy, University of Texas, Austin, Florida Fish and Wildlife Conservation Commission, and the Ocean Conservancy, has just published a recommended set of indicators to assess ecological resilience for five ecosystem types in the Northern Gulf of Mexico. Funded by the NOAA RESTORE Science Program, this project established conceptual ecological models for salt marsh, mangrove, seagrass, oyster and coral ecosystems to guide the identification of the indicators, the metrics used to assess them, and metric ratings that allow evaluation of ecological condition and ecosystem service provision. The study also provides a spatial analysis of the existing monitoring programs that are collecting data for the indicators to identify opportunities for additional data collection. This work is meant to help guide the collection of data that will inform living marine resource management, restoration planning and evaluation, damage assessment and recovery, and ecosystem health assessment. The project report and list of indicators can be downloaded at http://www.natureserve.org/conservation-tools/projects/ecological-resilience-indicators-five-northern-gulf-mexico-ecosystems . The spatial analysis is available at http://maps.coastalresilience.org/gulfmex/.