Abstract
The benthic and fish communities of the central portion of the Guanica, Puerto Rico shelf edge were studied to determine species abundance, distributions and species overlap between two depth stratifications, 20 and 45 m, at eight sites. A total of 67 fish species belonging to 21 families were identified. Similar species richness estimates were observed between depths, though fish assemblage composition differed significantly, with observable changes in feeding guild contributions of herbivore and omnivore (20 m) to a deeper assemblage composed of piscivores and planktivores (45 m). Coral assemblages consisted of 31 species at 20 m and 11 species at 45 m, accounting for 17.0% (±1.76 SE) and 2.6% (±0.89 SE) benthic cover for the altiphotic and mesophotic surveys, respectively. The altiphotic and mesophotic coral reef communities support different scleractinian coral assemblages with minimal species overlap. Altiphotic surveys of sponges yielded a higher species richness than mesophotic, with 60 and 54 species respectively, and an overall total of 71 species identified from both depths, with 45 species overlapping (63.0%). The percent cover of sponges surveyed at altiphotic reefs accounted for 9.0% (±1.04 SE), while the percent cover of sponges surveyed at mesophotic reefs was 14.0% (±1.96 SE). Our data show fish, coral, and sponge assemblages are differentiated between 20 and 45 m along thes provides an annotated species list of the local sponge fauna. Combined, these results highlight the need for con Guanica shelf edge offshore of the Guanica Biosphere Reserve. This study represents the first observations for species distributions of adjacent altiphotic and mesophotic coral reef habitats along the Guanica shelf edge, as well atinued environmental stewardship and conservation in the area.
Highlights
Mesophotic coral ecosystems (MCEs) are found on insular and continental slopes between 30–40 and 150 m in the tropics (Hinderstein et al, 2010; Locker et al, 2010; Slattery et al, 2011)
The aim of this study is to characterize, describe and compare the biological composition along the Guánica shelf edge to: (1) rest if there is a difference in the presence, overlap, and abundance of coral, fish, and sponge species between altiphotic (20 m) and mesophotic (45 m) coral reefs, and (2) to provide an annotated list of sponges encountered within our surveys, since the true diversity of Puerto Rican sponges is currently not known
We highlight the need to continue monitoring this dynamic ecosystem and emphasize that it is crucial to perform long-term time series assessments of the general area to fully assess any fluctuations in community structure (Wulff, 2001, 2006; Easson et al, 2015) and preservation of the overall marine biodiversity (Miloslavich et al, 2010; Jenkins and van Houtan, 2016; Hoeksema et al, 2017)
Summary
Mesophotic coral ecosystems (MCEs) are found on insular and continental slopes between 30–40 and 150 m in the tropics (Hinderstein et al, 2010; Locker et al, 2010; Slattery et al, 2011). As deep-water refuges, MCEs may provide a haven for scleractinian corals and commercially important fish (Lindfield et al, 2016), thereby replenishing adjacent impacted shallow water reefs with both coral (Bongaerts et al, 2017; Kahng et al, 2017) and fish larvae (Bejarano et al, 2014; Vaz et al, 2016), leading to the formation of the deep reef refuge hypothesis (Bongaerts et al, 2010) Despite their depth (∼30–120 m), mesophotic reefs are not immune to stressors and can experience environmental degradation at levels comparable to nearby altiphotic coral reefs (Lesser and Slattery, 2011; Loya et al, 2016; Smith et al, 2016). Mesophotic reefs cannot be assumed to be buffered from natural and anthropogenic stressors solely because of their increased depth or distance from the coast (Smith et al, 2016; White et al, 2017)
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