Handley et al. 2020. A Seagrass Monitoring Approach for the Gulf of Mexico

Lawrence Handley, Catherine Lockwood, Mark Finkbeiner, W. Judson Kenworthy. 2020. A Seagrass Monitoring Approach for the Gulf of Mexico.

A seagrass inventory and monitoring guideline will produce an invaluable resource to guide future efforts for conservation and restoration. The first step in producing a guideline is the development of a comprehensive approach for seagrass monitoring. The Approach is best viewed through a matrix concept by tier hierarchy based on spatial area, frequency of monitoring, and scope of project/study.

Tier 1 characterizes the overall distribution and extent of seagrasses in a defined ecosystem. The metrics used in Tier 1 are typically acquired by well-established and widely used and available remote sensing methods (aerial or satellite imagery) and analysis techniques. Tier 1 in the hierarchy is designed to characterize a few numbers of specific properties, ideally to inventory seagrasses over the entire system of interest, (e.g., GOM), while simultaneously characterizing relatively large regional areas. Tier 1 monitoring has been one of the most commonly used approaches for assessing the status and trends of seagrasses over long time periods and broad scales.

Tier 2 characterizes the ecological condition of seagrasses over relatively large areas by carefully selecting statistically valid sample sites and monitoring frequency. Tier 2 surveys are generally
restricted to subsections of the larger ecosystem, collected in or on the water at a greater number of sites and a higher temporal frequency than Tier 1. Tier 2 data provides more detailed properties describing the spatial-temporal variation in seagrass structure (e.g., species composition, size) and abundance (e.g., percent cover, shoot density) to quantify stressor/response relationships and produce estimates of the ecological condition of resources over broad areas.

Tier 3 monitoring includes more intensive monitoring than Tier 2, sometimes using a larger number of metrics sampled simultaneously and more frequently, and usually at a smaller number of sites that are smaller in size. Tier 3 monitoring is driven by specific scientific hypotheses (e.g., measuring levels of
uncertainty, evaluating multiple process-related responses) and local and regional programs that directly address questions regarding the specific mechanisms responsible for the changes detected in Tiers 1 and 2. Tier 3 can be effectively used to monitor the suspected drivers of change simultaneously with multiple seagrass stress response metrics to gain much better resolution and decrease ambiguity. Tier 3 monitoring is designed to test hypotheses and confirm or refute suspected mechanisms for stressor/response relationships.