Detecting sedimentation impacts to coral reefs resulting from dredging the Port of Miami, Florida USA

Abstract

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.

Pathogenesis of a Tissue Loss Disease Affecting Multiple Species of Corals Along the Florida Reef Tract

“…The emergence of infectious disease outbreaks often occurs following a change in host-parasite ecology such as introduction of novel pathogens in naïve host populations, emergence of newly evolved pathogens or changes in the environment fostering increased pathogen virulence or rates of transmission (Daszak et al, 2000(Daszak et al, , 2001. The first reports of high levels of SCTLD occurred in 2014 coincident with summer bleaching events across the Florida Reef Tract in 2014 and 2015 (Manzello, 2015;Walton et al, 2018) and dredging operations between 2013 and 2015 in the channel at Port of Miami, FL, that resulted in massive sedimentation near the initial site of the outbreak (Miller et al, 2016). It is likely that these two concurrent stresses, bleaching, and sedimentation, both of which can degrade coral health contributed to the emergence of this disease.…”

Rhodobacterales and Rhizobiales Are Associated With Stony Coral Tissue Loss Disease and Its Suspected Sources of Transmission

“…In 2014, the outbreak of Stony Coral Tissue Loss Disease (SCTLD) was first documented off Virginia Key, Florida (Miller et al, 2016;Precht et al, 2016;Walton et al, 2018). The spatial spread of SCTLD has been rapid, moving 100 km north and 30 km south from Virginia Key within 1 year (Precht et al, 2016).…”

“…Initially implicated as a 'white plague-like disease or syndrome' (Miller et al, 2016;Precht et al, 2016;Walton et al, 2018), SCTLD now has its own case definition (Stony Coral Tissue Loss Disease [SCTLD], 2018). Corals affected by SCTLD display focal or multifocal lesions, some of which may be preceded by a band of bleached tissue.…”

“…One study identified five bacteria families associated with SCTLD lesions, but none were found across all four coral species examined . Coincident with the initial outbreak of SCTLD, a dredging project at the Port of Miami in 2013-2015 increased sedimentation (Miller et al, 2016;Cunning et al, 2019) and relative turbidity (Rosales et al, 2019) in adjacent reefs. This has led to a controversial hypothesis that sediment is a potential source of transmission of the SCTLD pathogen(s) (Miller et al, 2016;Cunning et al, 2019;Gintert et al, 2019).…”

“…Coincident with the initial outbreak of SCTLD, a dredging project at the Port of Miami in 2013-2015 increased sedimentation (Miller et al, 2016;Cunning et al, 2019) and relative turbidity (Rosales et al, 2019) in adjacent reefs. This has led to a controversial hypothesis that sediment is a potential source of transmission of the SCTLD pathogen(s) (Miller et al, 2016;Cunning et al, 2019;Gintert et al, 2019). Initial studies also have indicated that SCTLD is likely contagious and waterborne (Precht et al, 2016;Aeby et al, 2019;Muller et al, 2020).…”