ALBERT

Description: The federal channel at Port of Miami, Florida, USA, was dredged between late 2013 and early 2015 to widen and deepen the channel. Due to the limited spatial extent of impact-assessment monitoring associated with the project, the extent of the dredging impacts on surrounding coral reefs has not been well quantified. Previously published remote sensing analyses, as well as agency and anecdotal reports suggest the most severe and largest area of sedimentation occurred on a coral reef feature referred to as the Inner Reef, particularly in the sector north of the channel. A confounding regional warm-water mass bleaching event followed by a coral disease outbreak during this same time frame made the assessment of dredging-related impacts to coral reefs adjacent to the federal channel difficult but still feasible. The current study sought to better understand the sedimentation impacts that occurred in the coral reef environment surrounding Port of Miami, to distinguish those impacts from other regional events or disturbances, and provide supplemental information on impact assessment that will inform discussions on compensatory mitigation requirements. To this end, in-water field assessments conducted after the completion of dredging and a time series analysis of tagged corals photographed pre-, during, and post-dredging, are used to discern dredging-related sedimentation impacts for the Inner Reef north. Results indicate increased sediment accumulation, severe in certain times and places, and an associated biological response (e.g., higher prevalence of partial mortality of corals) extended up to 700 m from the channel, whereas project-associated monitoring was limited to 50 m from the channel. These results can contribute to more realistic prediction of areas of indirect effect from dredging projects needed to accurately evaluate proposed projects and design appropriate compliance monitoring. Dredging projects near valuable and sensitive habitats subject to local and global stressors require monitoring methods capable of discerning non-dredging related impacts and adaptive management to ensure predicted and unpredicted project-related impacts are quantified. Anticipated increasing frequency and intensity of seasonal warming stress also suggests that manageable- but- unavoidable local stressors such as dredging should be partitioned from such seasonal thermal stress events.

Description: A variety of construction activities occur in or near estuarine and coastal waters of Florida within habitats that may support seagrass. Resource managers have a need for a science-based seagrass survey window for Florida to ensure that habitats are adequately mapped and characterized prior to authorizing the destruction or modification of the habitat. The development of a survey window requires a balance between physical factors that maximize the ability to detect seagrass during sampling (essentially water clarity) and the time of year that supports peak biomass and distribution. Of the seven seagrass species found in Florida, two species exhibit greater seasonality: Halophila decipiens and Halodule wrightii. Several publications were synthesized that refer to the seasonality of seagrass. Based on this review and consultation with leading seagrass scientists, surveys for these seagrass species should occur June 1 through September 30. Results from surveys conducted outside this window will require careful evaluation given the likelihood that seagrass distribution or extent is underrepresented. This recommendation differs from but is not in conflict with recommendations from NMFS Protected Resources Division for Johnson's seagrass, Halophila johnsonni, which exhibits a life history that makes year-round sampling less problematic than it is for Halophila decipiens and Halodule wrightii. Because Halophila decipiens and Halodule wrightii are within the range of Halophila johnsonii, conducting surveys within the June 1 to September 30 window could eliminate the need for multiple surveys.