Fig 1.
Map showing collection islands discussed in this study.
Map details relative locations of samples represented by respective symbols within cluster analysis (Fig 2).
Table 1.
In situ and satellite-derived environmental parameters used in this analysis.
Sample sites showing depth, calculated Fisher α indices, species richness, FORAM-Index values, aragonite saturation (Ωarag), pH, and calculated mean (μ), and mean anomaly (μ_.An) for Chlorophyll-a (Chl), sea surface temperature (SST), and sea surface salinity (SSS) from satellite data for July 2002—December 2014. Mean: mean of monthly values; Mean Anomaly: per-month mean of all monthly anomalies over all months (monthly anomalies: annual mean of mean monthly values minus each monthly value). Samples: DAR: Darwin; BAL: Baltra; ES: Española; SF: Santa Fé; IS: Isabela; SC: San Cristóbal; FL: Floreana.
Table 2.
Explanation of the major calculated oceanographic parameter.
Fig 2.
Comparisons of reef assessment analyses.
(A) Average FORAM–Index values plotted against average percent coral abundance in sediments for each collection site. (B) Average mean Chlorophyll-a (nutrient proxy) plotted against average percent coral abundance in sediments for each collection site, showing relative position with respect to coral reef turn on-turn off zone (CRTTZ; [11]). Abundances based on thin section point count data for 128 samples. D, Darwin; B, Baltra; SF, Santa Fé; ES, Española; FL, Floreana; SC, San Cristóbal; IS, Isabela. Islands color coded according to strong symbiont activity and reef production (green), marginal symbiont activity and no true reef production (blue), and low symbiont production and low coral production (red) according to their respective scales.
Fig 3.
Cluster analysis (Chord Distance; Ward Linkage) on Hellinger-transformed count data for 28 foraminifera species making up top 75% of production. Sample sites from individual clusters are marked by grey symbols for corresponding plots within CCA.
Fig 4.
Canonical correspondence analysis (CCA) triplot results.
CCA constructed from percent abundance data of 28 most abundant species, making up roughly 75% of total population of foraminifera. (A) optimal display for cluster sample (grey symbols) interpretation; (B) optimal display of foraminifera species interpretation. CCA results represent constrained ordination of foraminiferal population numbers, and not principal components analysis (PCA) of environmental variables at each site. Thus, triplots display how foraminiferal community is organized with respect to environmental parameters [47]. Environmental parameters are plotted as vectors (black), samples—labeled with their respective cluster symbols—are represented as points, and abbreviated species names (Table 1 caption) are plotted as points, color-coded according to their respective functional group affiliation (blue, symbiont bearing; red, opportunistic; green, heterotrophic). Permutation tests show high significance for CCA axes in question (S1 Fig).
Table 3.
Percent component of the 28 species making up 75% of all foraminifera encountered.
Abbreviations: Ah, Amphisorus hemprichii; Bsp, Borelis sp.;Cf, Cibicides fletcheri; Cl, Cibicides lobatulus; Csp, Cibicides sp. (juvenile); Cs, Cibicidoides schmitti; Ecs, Elphidium crispum subcrispum; Em, Elphidium macellum; Ep, Elphidium postulosum; Gv, Gypsina vesicularis; Mb, Miniacina barringtonensis; Msp, Miniacina sp.; NHsp, Neohauerina or Hauerina sp. (all specimens degraded); Nsp, Nouria sp.; Pd, Parahauerina displicata; Pc, Poroeponides cribrorepandus; Qb, Quinqueloculina blackbeachensis; Qg, Quinqueloculina galapagosensis; Qs, Quinqueloculina suborbicularis; Rmc, Rotorbinella mira clarionensis; Rmg, Rotorbinella mira galapagosensis; Sm, Sorites marginalis; Sg, Sphaerogypsina globulus; Ta, Triloculina ashbrooki; Usp1, Unidentifiable agglutinated specimens 1; Usp2, Unidentifiable agglutinated specimens 2; Usp3, Unidentifiable agglutinated specimens 3; Usp4, Unidentifiable agglutinated specimens 4. Samples: DAR: Darwin; BAL: Baltra; ES: Española; SF: Santa Fé; IS: Isabela; SC: San Cristóbal; FL: Floreana.
Fig 5.
Average percent benthic foraminifera composition plotted against species richness (A) and Fisher α diversity (B). Plots show an inverse correlation between foraminiferal production and species richness / diversity. Islands are as follows: + Baltra;—Darwin; ● Santa Fé; ▲Española; × Isabela; ♦ San Cristóbal; ■Floreana.
Fig 6.
Ternary diagrams for major test structure categories of Loeblich & Tappan (1984) [52].
(A) average compositions of foraminifera from each sampled island, including mean pH (red) and mean Fisher α indices (blue), revealing a general increase in hyaline forms along declining pH and Fisher α indices gradients as well as shift toward higher agglutinated content at Española, Santa Fé and Isabela islands with decreasing pH (circled). (B) Ternary representation of a shift from calcareous to agglutinated dominance along a declining pH gradient as represented in Dias et al. [75]. *Baltra pH values are inferred from regression of all site data.
Fig 7.
Graphs of in situ logger temperature data from Darwin reef taken at a depth of 12m.
(A) Full temperature data set from 26 November 2016–18 April 2017. (B) Detail of temperature fluctuations from 14 Jan– 19 Jan 2017, showing strong temperature depression resulting from localized shoaling of deeper water masses into reef environment.
Fig 8.
Univariate regression tree analysis.
Plot shows the dominant controls on the cluster distribution in cluster analysis. The plot was produced by modeling the response variables (binned results of the cluster analysis) against the explanatory variables (oceanographic controls and sample depths. The resulting dendrogram reveals long-term average temperature anomalies (Mean.Anomaly..SST) as the dominant oceanographic influence of cluster splits, followed by sample depth.
Fig 9.
Scanning electron micrographs of select foraminifera species exhibiting varying degrees of test degradation.
1. Elphidium crispum subcrispum; 2. Poroeponides cribrorepandus; 3. Sphaerogypsina globulus; 4.Quinqueloculina sp.; 5. Textularia sp.; 6. Unidentified agglutinated fragment; 7. Cibicides(?) sp.; 8. Elphidium sp.