Chesapeake Bay SAV: A Second Technical Synthesis

Description

The health and survival of submerged aquatic vegetation, or SAV, communities in the Chesapeake Bay and other coastal waters depend on suitable environmental conditions that define the quality of SAV habitat. These habitats have been characterized previously for Chesapeake Bay using simple models that relate SAV presence to medians of water quality variables. In Chesapeake Bay Submerged Aquatic Vegetation Habitat Requirements and Restoration Targets: A Technical Synthesis, published in 1992, SAV habitat requirements were defined in terms of five water quality variables. These SAV habitat requirements have been used in conjunction with data from the Chesapeake Bay Monitoring Program as diagnostic tools to assess progress in restoring habitat quality for SAV growth in Chesapeake Bay. Attempts to use these habitat requirements to predict SAV presence or absence in Chesapeake Bay and elsewhere, however, have met with mixed success.

This report provides an integrated approach for defining and testing the suitability of Chesapeake Bay shallow water habitats in terms of the minimum light requirements for SAV survival. It incorporates statistical relationships from monitoring data, field and experimental studies, and numerical model computations to produce algorithms that use water quality data for any site to calculate potential light availability at the leaf surface for SAV at any restoration depth. The original technical synthesis defined SAV habitat requirements in terms of five water quality parameters based on field correlations between SAV presence and water quality conditions. In the present approach, these parameters are used to calculate potential light availability at SAV leaves for any Chesapeake Bay site. These calculated percent light at the leaf surface values are then compared to minimum light requirements to assess the suitability of a particular site as SAV habitat. The approach for assessing SAV habitat conditions described in this report represents a major advance over that presented in 1992. At the same time, areas requiring further research, assessment and understanding have been brought into sharper focus.