Fig 1.
Map depicts the locations of the Tristan da Cunha Islands in the South Atlantic (top) and locations of scuba surveys (n = 34), pelagic camera surveys (n = 26), and deep sea benthic camera surveys (n = 23) in the four islands of the Tristan da Cunha Islands group (bottom).
Fig 2.
Temperature, salinity and dissolved oxygen.
Oceanographic properties of the water column from a CTD attached to the deep-water drop cameras. A. Temperature (oC), B. salinity (PSU) and C. dissolved oxygen (mg/L) from each island by shore orientation are shown. The depth at which both temperature and salinity equilibrated among islands (approximately 600-750m) is shown in the grey band.
Fig 3.
Fish biomass and density-island means.
Stacked bar plots depicting fish biomass and density patterns in nearshore habitats of the Tristan da Cunha Islands from SCUBA surveys. Shown are the island-level mean (A) fish biomass (tonnes ha-1) and (B) fish density (no. m-2) for each species observed. Error bars are ± 1 standard error of the mean for the total fish biomass or total fish density respectively.
Fig 4.
Fish biomass and density-site means.
Bubble plots depicting site-level variation in fish biomass, density, and species composition of kelp forest fish communities in the four Tristan da Cunha Islands. Shown are plots of (A) fish biomass and (B) fish density. Bubble size scales with the biomass or density estimated using site-level means of SCUBA surveys.
Table 1.
Linear mixed models testing the effects of island (fixed), site (random), and depth zone (fixed) on patterns of fish biomass among the Tristan da Cunha islands.
Density and biomass were square root transformed. Statistically significant p-values are in bold text. Presented for the random effect of site are Wald p-values and percent of total variance explained.
Table 2.
Linear mixed models testing the effects of island (fixed), site (random), and depth zone (fixed) on patterns of fish density among the Tristan da Cunha islands.
Density and biomass were square root transformed. Statistically significant p-values are in bold text. Presented for the random effect of site are Wald p-values and percent of total variance explained.
Fig 5.
Invertebrate and algal biomass and density-island means.
Bar plots depicting island-level variation in lobster biomass and the density of common invertebrates and macroalgae in the Tristan da Cunha Islands from SCUBA surveys of nearshore habitats. Shown are mean values for each species ± 1 standard error of the mean.
Fig 6.
Invertebrate and algal biomass and density-site means.
Bubble plots depicting site-level variation in (A) lobster biomass and (B) sea urchin density, (C) giant kelp stipe density, and (D) pale kelp density across the four Tristan da Cunha Islands. Bubble size scales with the biomass or density estimated using site-level means of SCUBA surveys in nearshore habitats.
Table 3.
Linear mixed models testing the effects of island, site, and depth zone on patterns of invertebrate and macroalgal density and lobster biomass among the Tristan da Cunha islands.
Density and biomass were square root transformed. Statistically significant p-values are in bold text. Density and biomass were square root transformed. Presented for the random effect of site are Wald p-values and percent of total variance explained.
Fig 7.
Fish and benthic community structure.
Multivariate description of fish and benthic communities in the Tristan da Cunha Islands from nearshore SCUBA surveys. Plots depict non-metric multidimensional scaling (nMDS) analyses of (A) fish assemblages and (B) benthic assemblages using site-level densities of species observed. Vectors overlaying the plot depict the species that are driving separation among sites and islands in species composition in fish and benthic communities. Data were square root transformed prior to analysis.
Table 4.
Results of a PERMANOVA testing differences in fish community structure among the Tristan da Cunha Islands.
Table 5.
Results of a PERMANOVA testing differences in benthic invertebrate and kelp community structure among the Tristan da Cunha Islands.
Fig 8.
Species richness and abundance from pelagic BRUVs.
Bubble plots depicting A. site-level variation in species richness and B. numerical abundance from pelagic BRUV stations sampled across the four Tristan da Cunha Islands. Bubble size scales with the richness or total abundance of individual organisms observed from each pelagic BRUV deployment. Inset bar plots show mean values for each island ± 1 standard error of the mean.
Fig 9.
Multivariate description of pelagic assemblages in the Tristan da Cunha islands from mid-water BRUVS surveys.
Plots depict canonical analysis of principal coordinates (CAP) analyses based on a Bray-Curtis resemblance matrix site-level species specific abundances. Vectors overlaying the plot depict the species that are driving separation among sites and islands in species composition. Data were square root transformed prior to analysis.
Table 6.
Results of a PERMANOVA testing differences in pelagic community structure among islands from the mid-water BRUVS surveys at the Tristan da Cunha Islands.
Data are species abundances (MaxN) and were square root transformed.
Fig 10.
Species richness and abundance from deep water drop cameras.
Bubble plots depicting A. site-level variation in species richness and B. numerical abundance from deep-water drop-camera stations sampled across the four Tristan da Cunha Islands. Bubble size scales with the richness or total abundance of individual fishes observed from each drop camera deployment. Inset bar plots show means (± 1 standard error of the mean) for the two benthic types.
Fig 11.
Multivariate description of the fish community in the Tristan da Cunha Islands from deep-water camera surveys.
Multivariate description of the fish community categorized into two depth strata (0–750 m and >750 m depth). Shown is a non-metric multidimensional scaling (nMDS) analysis of the fish assemblage using presence/absence data at each station and a Euclidean distance matrix. Vectors overlaying the plot depict the species that are driving separation among sites and islands (Gough = triangle symbols, Inaccessible = diamond symbols, Nightingale = circle symbols, Trista da Cunha = square symbols) in species composition in deep-water fish communities.
Table 7.
Results of a PERMANOVA testing differences in fish community structure between depth categories (0–750 m vs. >750 m depth) from the deep-sea drop-cam surveys at the Tristan da Cunha Islands.