Algal turf sediment dynamics across the Florida Reef Tract

Algal turfs and their associated sediments are dominant components of many degraded reefs, where they mediate key ecosystem processes. However, the quantification of algal turfs and their sediments across reef shelves is limited outside Indo-Pacific reef systems. We quantified algal turf length, sediment loads, and sediment grain size distribution across four reef positions (nearshore, inner, middle, and outer) at three locations along the northern Florida Reef Tract (FRT). Sediment loads were positively associated with algal turf length and generally declined moving offshore. Nearshore reefs supported algal turfs that were both 1.6-fold longer and contained 1.6-fold higher sediment loads than on outer reefs, while sediment composition shifted toward finer grain sizes offshore. Nevertheless, regardless of reef position, all algal turfs had high sediment loads ranging from 1,445 to 16,639 g m-2. Our findings suggest that cross-shelf patterns in algal turf sediment dynamics are present on Western Atlantic reefs and reveal that long sediment-laden algal turfs dominate on the FRT. These results highlight the pervasive nature of sediment-laden algal turfs on degraded reefs and emphasize the need to monitor and manage their expansion on reefs subject to chronic coastal development and climate-driven disturbance.