Mesophotic reef fish assemblages of the remote St. Peter and St. Paul’s Archipelago, Mid-Atlantic Ridge, Brazil

Abstract

Mesophotic reeffish assemblages (30-90 m depth) of the small and remote St. Peter and St. Paul's Archipelago (SPSPA), Mid-Atlantic Ridge, Brazil, were characterized using remotely operated vehicles. Ordination analyses identified distinct fish assemblages in the upper (30-50 m) and lower (50-90 m) mesophotic zones, the former characterized by high abundances of species that are also abundant at euphotic reefs (Caranx lugubris, Melichthys niger, Stegastes sanctipauli and Chromis multilineata) and the latter dominated by two mesophotic specialists (Prognathodes obliquus and Chromis enchrysura). Planktivores dominated fish assemblages, particularly in the upper mesophotic zone, possibly due to a greater availability of zooplankton coming from the colder Equatorial Undercurrent in mesophotic depths of the SPSPA. Turf algae, fleshy macroalgae and scleractinian corals dominated benthic assemblages between 30 and 40 m depth, while bryozoans, black corals and sponges dominated between 40 and 90 m depth. Canonical correspondence analysis explained 74 % of the relationship between environmental characteristics (depth, benthic cover and complexity) and structure of fish assemblages, with depth as the most important independent variable. Juveniles of Bodianus insularis and adults of P. obliquus and C. enchrysura were clearly associated with branching black corals (Tanacetipathes spp.), suggesting that black corals play key ecological roles in lower mesophotic reefs

Mesophotic Depth Gradients Impact Reef Fish Assemblage Composition and Functional Group Partitioning in the Main Hawaiian Islands

“…In addition, while not fully protected from environmental or biological disturbance events, mesophotic coral ecosystems ("MCEs") may be partially shielded from some of the influences impacting shallow water coral reefs, and serve as population reservoirs for depth-generalists targeted by fishers in 0-30 m depths (Glynn, 1996;Riegl and Piller, 2003;Bak et al, 2005;Lesser et al, 2009;Bongaerts et al, 2010;Slattery et al, 2011;Kane et al, 2014;Lindfield et al, 2014Lindfield et al, , 2016Tenggardjaja et al, 2014;Baker et al, 2016). Conversely, while shallow water coral reefs and associated habitats (e.g., pavement or rubble flats) may shelter depth-restricted specialist fishes incapable of inhabiting deeper depths, MCEs and other deep-water mesophotic benthic habitats ("MBHs") can likewise host distinct communities and species of reef fishes not found in 0-30 m depths, with depth, habitat type, structural complexity, and biotic cover acting in concert with geographic extent and oceanographic drivers to structure assemblages and functional-level groupings (Thresher and Colin, 1986;Beukers and Jones, 1998;Brokovich et al, 2008;MacNeil et al, 2009;Harvey et al, 2013;Komyakova et al, 2013;Jankowski et al, 2015;Andradi-Brown et al, 2016;Heyns-Veale et al, 2016;Rosa et al, 2016). As a result, limitations of many marine science research programs include missing portions of reef fish populations that are utilizing deeper habitats, or omitting species of potential conservation or management importance that are restricted to mesophotic depths.…”

Changes in mesophotic reef fish assemblages along depth and geographical gradients in the Northwestern Hawaiian Islands

“…The dominant taxa change from photosynthetic organisms in shallower depths to obligate heterotrophs at greater depths (Kahng et al 2014), and the amount of live benthic cover generally decreases with depth (Kahng and Kelley 2007;Rooney et al 2010) although such a pattern can be site-specific and likely depends on depth ranges and intervals of analysis (e.g., Brokovich et al 2008;Eyal et al 2016). Fish assemblages on mesophotic reefs are characterized by relatively high abundances of planktivores and relatively low abundances of herbivores Fukunaga et al 2016;Rosa et al 2016). Species richness of fish generally correlates with live coral cover and therefore decreases with depth (reviewed by Kahng et al 2014).…”

Theme section on mesophotic coral ecosystems: advances in knowledge and future perspectives

“…Rosa et al (2016) conducted the first quantitative characterization of reef fish assemblages (30-90 m depth) of the small and remote St. Peter and St. Paul's Archipelago (mid-Atlantic ridge, Brazil), while Pinheiro et al (2016) used underwater visual assessments to characterize MCE fish assemblages ranging from 45 to 130 m depth in Bermuda and Curaçao; Bermuda had lower fish richness and abundance but higher biomass than Curaçao. Both studies found distinct vertical zonation in the fish assemblages and concluded that depth seems to be an important driver of community structure.…”

“…Both studies found distinct vertical zonation in the fish assemblages and concluded that depth seems to be an important driver of community structure. For example, Rosa et al (2016) identified distinct fish assemblages occurring at 30-50 m and at 50-90 m, with the upper mesophotic assemblage containing species that also occur on SWRs (80 % of all species), while the deeper assemblage contained endemic and mesophotic specialists. Both studies also found that the composition of the benthic communities strongly influenced differences in fish assemblages.…”