Widespread Deposition in a Coastal Bay Following Three Major 2017 Hurricanes (Irma, Jose, and Maria)

Trevor N Browning,Miguel Canals-Silander,Rebekka A Larson,Gregg R Brooks,Carlos E Ramos-Scharrón,Derek E Sawyer

doi:10.1038/s41598-019-43062-4

Abstract

In 2017, three major hurricanes (Irma, Jose, and Maria) impacted the Northeastern Caribbean within a 2-week span. Hurricane waves can cause physical damage to coastal ecosystems, re-suspend and transport antecedent seafloor sediment, while the associated intense rainfall can yield large influxes of land-derived sediment to the coast (e.g. burial of ecosystems). To understand sedimentation provenance (terrestrial or marine) and changes induced by the hurricanes, we collected bathymetry surveys and sediment samples of Coral Bay, St. John, US Virgin Islands in August 2017, (pre-storms) and repeated it in November 2017 (post-storms). Comparison reveals morphologic seafloor changes and widespread aggradation with an average of ~25 cm of sediment deposited over a 1.28 km2 benthic zone. Despite an annual amount of precipitation between surveys, sediment yield modeling suggests watersheds contributed <0.2% of the total depositional volume. Considering locally established accumulation rates, this multi-hurricane event equates to ~1–3 centuries of deposition. Critical benthic communities (corals, seagrasses) can be partially or fully buried by deposits of this thickness and previous studies demonstrate that prolonged burial of similar organisms often leads to mortality. This study illuminates how storm events can result in major sediment deposition, which can significantly impact seafloor morphology and composition and benthic ecosystems.

Highlights

Coastal ecosystems are critical to economic, cultural, and ecologic health[12,13,14], yet are vulnerable to hurricanes[15]
In the Caribbean, hurricanes have led to dramatic declines in dominant coral species[39,40,41]
As the storm moved in the west-north-west direction, the eyewall passed over Coral Bay

Summary

Introduction

Coastal ecosystems are critical to economic, cultural, and ecologic health[12,13,14], yet are vulnerable to hurricanes[15]. Calcareous algae are reef builders[16], seagrasses serve as fish nurseries[17,18], and coral reef communities create diverse habitats[14] and buffer the coast from wave action and storms[19] Coastal vegetation such as seagrass communities are an important source for carbon capture and storage and do so ~2x more efficiently than tropical rainforests[20]. Only a series of ephemeral gullies activated by extreme rainfall events[48,49,50,51] This allows a situation in which the land-based sediment transport system is either turned ‘on’ (during rainfall events) or ‘off ’ (Fig. 1).

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Methods

Results

Conclusion