Fig 1.
Map of Northern Gulf of Aqaba showing study sites.
Suspended artificial reef (FER) and seafloor artificial reef (IGL) in blue, and two natural reef sites in red (IUI, OBS). Inset shows location of the Gulf in the Red Sea.
Fig 2.
Experimental units and arrays at artificial and natural reefs.
(A) 2-collector arrays at an artificial reef (IGL) and (B) a 4-collector array at a natural reef (IUI) in the mensurative experiment; (C) 2-collector arrays at a natural reef (IUI) in the manipulative experiment and (D) at an artificial reef (FER) in the mensurative experiment. Each collector (ceramic tile) in an array had 2 settlement surfaces (topside, underside). For the manipulative experiment (C), each array had 1 collector enclosed in a cage to exclude large consumers, the other collector served as an uncaged control.
Fig 3.
Trajectories of change in community composition among reefs in the mensurative and manipulative experiments.
nMDS plot of community composition as planar cover (%) on collector topsides and undersides for (A) two artificial reefs (FER, IGL) and two natural reefs (IUI, OBS) over 13 mo in the mensurative experiment (Oct 2015–Nov 2016), and (B) for control (C) and exclusion (E) treatments at one of the artificial reefs (FER) and one of the natural reefs (IUI) over 7 mo in the manipulative experiment (Nov 2016). Each numbered symbol represents the average composition at that sampling interval (elapsed time, mo); symbol colour intensifies with time and symbols for final samples are magnified for clarity. Mensurative experiment: n = 10 arrays for artificial reefs, 5 arrays for natural reefs. Manipulative experiment; n = 8 collectors for each treatment x site combination.
Fig 4.
Final community composition on artificial and natural reefs in the mensurative experiment.
Non-metric multidimensional scaling (nMDS) plot of (A) community composition as planar cover (%) and (B) invertebrate composition as biomass (g 400 cm-2) on collector topsides and undersides (averaged per array) at two artificial reefs (FER, IGL; orange symbols, n = 10 arrays) and two natural reefs (IUI, OBS; blue symbols, n = 5 arrays) at the end of the mensurative experiment (Nov 2016). Ellipses bound groups of arrays of 70% similarity.
Fig 5.
Final biomass of invertebrates on artificial and natural reefs in the mensurative and manipulative experiments.
Biomass (g 400 cm-2) of invertebrate colonists on collector topsides and undersides for (A) two artificial reefs (FER, IGL; n = 10 arrays) and two natural reefs (IUI, OBS; n = 5 arrays) at the end of the mensurative experiment (Nov 2016), and for (B) control (C) and exclusion (E) treatments at one of the artificial reefs (FER) and one of the natural reefs (IUI) (n = 8 collectors for each site x treatment combination) at the end of the manipulative experiment (Nov 2016). Bar heights are mean (+SE) total biomass for arrays in the mensurative experiment and collectors in the manipulative experiment.
Fig 6.
Final community composition in treatments at reefs in the manipulative experiment.
Non-metric multidimensional scaling (nMDS) plot of (A) community composition as planar cover (%) and (B) invertebrate composition as biomass (g 400 cm-2) on collector topsides and undersides in control (C, circles) and exclusion (E, triangles) treatments (n = 8 collectors) at an artificial reef (FER, orange symbols) and a natural reef (IUI, blue symbols) at the end of the manipulative experiment (Nov 2016).