Modern foraminiferal distribution and diversity in two atolls from the Maldives,Indian Ocean

Foraminifera from the coral-reef lagoons of two atolls are used to investigate the distribution and diversity of assemblages in the central Indian Ocean. Eight assemblages and 270 species of foraminifera are identified. Three assemblages are reefal and dominated by Amphistegina and Calcarina. Only one lagoon assemblage is present in both atolls, which is characterized by abundant Ammonia sp. 1 and smaller miliolid foraminifera. In Ari Atoll, abundant Amphistegina sp. 1, Operculina ammonoides, Amphistegina radiata and Nummulites venosa characterize one lagoon assemblage and abundant Neoeponides bradyi and Textularia cf. T. cushmani characterize the other. In Rasdhoo Atoll, abundant Textularia gr. foliacea and Spiroloculina nummiformis characterize one lagoon assemblage and abundant Textularia cf. T. cushmani and Textularia sp. 5 characterize the other. The assemblages compare well with sedimentological characteristics, which is also reflected in their distributions. Species diversity in the Maldives appears to be higher than the western Indian Ocean region due to the stronger influence of central Indo-Pacific faunas. It is not however, as high as the central Indo-Pacific region, which may be due to lower habitat diversity.     

Holocene trends in distribution and diversity of benthic foraminifera assemblages in atoll lagoons,Belize, Central America

Seven benthic foraminiferal assemblages were identified in vibracores through Holocene lagoons of three Belize atoll lagoons (Glovers Reef, Lighthouse Reef, Turneffe Islands). These include (1) the low-diversity Cribroelphidium assemblage (2) the Cribroelphidium-Elphidium assemblage (3) the Quinqueloculina-Triloculina-Peneroplis assemblage (4) the high-diversity miliolid assemblage (5) the Archaias-miliolid assemblage (6) the low-diversity miliolid assemblage, and (7) the mixed assemblage. Altogether, 109 species and 56 genera were identified. The highest diversities are observed in the largest lagoon (Turneffe Islands), whereas one of the smaller lagoons (Glovers Reef) exhibits the lowest diversities during the Holocene. No significant changes in diversity over time occur, however, a slight trend to higher diversity may be observed through the Holocene, suggesting that the foraminiferal faunas in the atolls are in a diversification stage. Faunal diversity in atoll lagoons appears to be controlled largely by habitat size, habitat heterogeneity, and water circulation. Habitat age and water depth only play minor roles. Substrate texture, water depth, and turbidity influence the predominant modes of life of benthic foraminifera encountered in the lagoons (epifaunal versus infaunal versus symbiont-bearing). Time-averaging effects were not observed, even though lagoonal sedimentation rates fluctuate in individual cores and the three lagoons, and despite the fact that sediments are modified through bioturbation by callianassid shrimps. This finding underlines the potential of benthic foraminifera for paleoecological studies in the fossil record of reefs and carbonate platforms.     

Spatial Patterns in the Distribution,Diversity and Abundance of Benthic Foraminifera around Moorea (Society Archipelago,French Polynesia)

Coral reefs are now subject to global threats and influences from numerous anthropogenic sources. Foraminifera, a group of unicellular shelled organisms, are excellent indicators of water quality and reef health. Thus we studied a set of samples taken in 1992 to provide a foraminiferal baseline for future studies of environmental change. Our study provides the first island-wide analysis of shallow benthic foraminifera from around Moorea (Society Archipelago). We analyzed the composition, species richness, patterns of distribution and abundance of unstained foraminiferal assemblages from bays, fringing reefs, nearshore and back- and fore-reef environments. A total of 380 taxa of foraminifera were recorded, a number that almost doubles previous species counts. Spatial patterns of foraminiferal assemblages are characterized by numerical abundances of individual taxa, cluster groups and gradients of species richness, as documented by cluster, Fisher α, ternary plot and Principal Component Analyses (PCA). The inner bay inlets are dominated by stress-tolerant, mostly thin-shelled taxa of Bolivina, Bolivinella, Nonionoides, Elongobula, and Ammonia preferring low-oxygen and/or nutrient-rich habitats influenced by coastal factors such as fresh-water runoff and overhanging mangroves. The larger symbiont-bearing foraminifera (Borelis, Amphistegina, Heterostegina, Peneroplis) generally live in the oligotrophic, well-lit back- and fore-reef environments. Amphisteginids and peneroplids were among the few taxa found in the bay environments, probably due to their preferences for phytal substrates and tolerance to moderate levels of eutrophication. The fringing reef environments along the outer bay are characterized by Borelis schlumbergeri, Heterostegina depressa, Textularia spp. and various miliolids which represent a hotspot of diversity within the complex reef-lagoon system of Moorea. The high foraminiferal Fisher α and species richness diversity in outer bay fringing reefs is consistent with the disturbance-mosaic (microhabitat heterogeneity) hypothesis.Calculations of the FORAM Index (FI), a single metric index to assess reef vitality, indicate that all fore- and most back-reef environments support active carbonate accretion and provide habitat suitability for carbonate producers dependent on algal symbiosis. Lowest suitability values were recorded within the innermost bays, an area where natural and increasing anthropogenic influences continue to impact the reefs. The presence of habitat specific assemblages and numerical abundance values of individual taxa show that benthic foraminifera are excellent recorders of environmental perturbations and good indicators useful in modern and ancient ecological and environmental studies.     

Experimental dissolution of a fossil foraminiferal assemblage (Paleocene–Eocene Thermal Maximum,Dababiya, Egypt): Implications for paleoenvironmental reconstructions

Dissolution experiments were carried out on a foraminiferal assemblage from the Paleocene–Eocene Thermal Maximum (PETM) at Dababiya, Egypt, in order to: 1) reveal the effects of differential dissolution on the composition of the foraminiferal assemblage and 2) develop objective criteria for the evaluation of dissolution in foraminiferal assemblages used in early Paleogene paleoenvironmental reconstructions, particularly with respect to neritic Midway-type assemblages from the Paleocene/Eocene transition. Our results confirm two general observations on modern foraminifera: 1) planktic foraminifera are much more vulnerable to dissolution than benthic foraminifera, leading to depressed P/B ratios and 2) dissolution susceptibility differs between size fractions, with the smaller specimens dissolving more rapidly than the bigger ones, leading to a larger average size of the remaining assemblage. Within a size fraction, wall structure and thickness are considered to be the main factors controlling differential dissolution susceptibility. We propose a ranking scheme for taxa with respect to dissolution resistance. Among the benthic taxa, Lenticulina is most resistant, followed by the agglutinated Gaudryina cf. ellisorae and Alabamina midwayensis. Biserial and triserial hyaline taxa and the porcelaneous Spiroloculina sp. are most susceptible to dissolution, whereas rotaliines, such as Cibicidoides and Anomalinoides have an intermediate susceptibility. This implies that mild dissolution of a Midway-type benthic assemblage leads to a relative enrichment in Lenticulina, Gaudryina and rotaliines. Amongst planktic foraminifera, the muricate taxa Acarinina and Morozovella are most resistant, followed by the cancellate Subbotina. The smooth and generally small Globanomalina and Zeauvigerina are least resistant to dissolution. Our data enable to objectively evaluate various degrees of dissolution in benthic and planktic foraminiferal assemblages retrieved from the lower Paleogene Tethyan outcrops. In this way taphonomic artifacts can be readily distinguished from paleoenvironmental signals affecting the primary composition of the assemblages. More generally, we propose that the combined use of foraminiferal numbers, P/B ratio and relative abundances of non-calcareous agglutinated taxa and Lenticulina may provide a powerful proxy for assessing dissolution in hemipelagic assemblages from Cenozoic and upper Cretaceous continental margins. In order to achieve more robust pre-Quaternary paleoenvironmental reconstructions based on quantitative foraminiferal data, application of dissolution proxies, like proposed here, or in slightly modified form, should become a more widely used micropaleontologic procedure. Particularly continental margin studies dealing with major biotic events (e.g. PETM) or employing P/B ratios for sea-level reconstructions should benefit from such an approach.     

UK intertidal foraminiferal distributions: implications for sea-level studies

Foraminiferal assemblages have been collected from ten intertidal study areas situated on the east, south and west coasts of the UK. The assemblages display a vertical zonation which indicates that the distribution of foraminifera in these intertidal environments is usually the direct function of altitude with the duration and frequency of intertidal exposure the most important factors. Multivariate analyses separate foraminiferal assemblages into two faunal zones: a high- and middle marsh zone consisting of differing abundances of Jadammina macrescens, Trochammina inflata and Miliammina fusca; and a low-marsh and tidal flat zone dominated by calcareous foraminiferal species, notably Elphidium williamsoni, Haynesina germanica and Quinqueloculina spp. These faunal zones are similar to those in other mid-latitude, cool temperate intertidal environments although there are spatial and temporal variations between areas. The altitudinal ranges of the faunal zones are employed to identify the vertical relationship of the local environment in which the assemblage accumulated to a reference tide level.     

The anthropogenic impact on the western French coasts as revealed by foraminifera: A review

Coastal benthic foraminifera are widely studied as indicators of environmental disturbance. This paper presents a synthesis of the studies that showed correlations between foraminiferal assemblages and various environmental problems along the western French coasts. Pollution in coastal environments may be chronic, resulting from current activities, or may result from accidental events. All the studies show that foraminifera may be used as indicators of pollution after deconvoluting from natural impacts. The most sensitive foraminifera identified by these studies are Haynesina germanica, Ammonia tepida, Cribroelphidium excavatum, bolivinids and Eggerelloides scabrus.     

Recent benthic foraminiferal assemblages from cold-water coral mounds in the Porcupine Seabight

Cold-water coral ecosystems are characterised by a high diversity and population density. Living and dead foraminiferal assemblages from 20 surface sediment samples from Galway and Propeller Mounds were analysed to describe the distribution patterns of benthic foraminifera on coral mounds in relation to different sedimentary facies. Hard substrates were examined to assess the foraminiferal microhabitats and diversities in the coral framework. We recognised 131 different species, of which 27 prefer an attached lifestyle. Epibenthic species are the main constituents of the living and dead foraminiferal assemblages. The frequent species Discanomalina coronata was associated with coral rubble, Cibicides refulgens showed preference to the off-mound sand veneer, and Uvigerina mediterranea displayed abundance maxima in the main depositional area on the southern flank of Galway Mound, and in the muds around Propeller Mound. The distribution of these species is rather governed by their specific ecological demands and microhabitat availability than by the sedimentary facies. Benthic foraminiferal assemblages from coral mounds fit well into basin-wide-scale distribution patterns of species along the western European continental margin. The diversity of the foraminiferal faunas is not higher on the carbonate mounds as in their vicinity. The living assemblages show a broad mid-slope diversity maximum between 500 and 1,300 m water depth, which is the depth interval of coral mound formation at the Celtic and Amorican Margin. The foraminiferal diversity maximum is about 700 m shallower than comparable maxima of nematodes and bivalves. This suggests that different processes are driving the foraminiferal and metazoan diversity patterns.     

Contributions of molecular phylogenetics to foraminiferal taxonomy: General overview and example of Pseudoeponides falsobeccarii

Molecular phylogenetics gives new insights into the taxonomy of foraminifera, independent of their morphology. After a survey of the present knowledge on how molecular phylogeny can contribute to foraminiferal taxonomy, we present an applied example. The comparison of ribosomal DNA (rDNA) sequences belonging to the SSU (Small Subunit) and LSU (Large Subunit) genes of Pseudoeponides falsobeccarii with other similar sequences of rotaliids available in GenBank shows that this species actually belongs to the genus Ammonia, because it groups inside the other Ammonia sequences instead of forming a distinct clade. Moreover, Ammonia falsobeccarii forms a clade well separated from other Ammonia phylotypes, meaning that it can be considered as a distinct species, and not as an ecophenotype of one of the other Ammonia species.     

Palaeogeographic and stratigraphic distribution of mid-late Oxfordian foraminiferal assemblages in the Prebetic Zone (Betic Cordillera, Southern Spain)

Middle-Upper Oxfordian assemblages of foraminifera in the Prebetic Zone (Betic Cordillera, SE Spain) were analysed at the genus level to determine their composition, relative abundance, diversity, and dominance, as well as the size of the specimens. A relationship has been established between lithofacies, palaeogeography and composition of foraminiferal assemblages, the former two also determining the stratigraphic record of these microfossil assemblages. Two assemblages of foraminifera serve to identify relatively distal and proximal areas in the Prebetic shelf. The distal assemblage is characterized by higher diversity, specimens of greater size, and more abundant planktic and agglutinated forms. Benthic forms include Ophthalmidium, Epistomina and colonies of encrusting foraminifera. The proximal assemblage shows lower diversity, lower abundance of planktic forms, Epistomina and encrusting nubeculariids, and a greater abundance of spirillinids and Reofax. On the whole, planktic foraminifera decrease upwards in the studied succession, which, together with decreasing nodularity, could be related to system tract conditions previously proposed for Oxfordian deposits in the southern palaeomargin of Iberia.     

Sediment oxygen demand and benthic foraminiferal faunas in the Arabian Gulf: A test of the method on a siliciclastic substrate

In this study, we investigated the relationship between environmental parameters (water and sediment) and benthic foraminiferal assemblages found in nearshore siliciclastic sediment in the Arabian Gulf. Nearshore marine water and sediment samples were collected from a beach on the Gulf of Bahrain located south of Al Khobar, Saudi Arabia. The water samples were analyzed for biochemical oxygen demand (BOD₅) and other chemical analyses. The sediment samples were tested for sediment oxygen demand (SOD) and heavy metal analysis. Results showed the BOD₅ levels were below the detection limit (<1 ppm), while the mean SOD value was 0.97 ± 0.08 g/m²·day. The water and sediments were unpolluted and free of eutrophic enrichment, while the sediment was anoxic. The two most common genera in the benthic foraminiferal assemblage, Ammonia and Elphidium, are typical of shallow water sandy substrates. This is the first reported comparison between SOD and benthic foraminiferal assemblages.     

Microfacies and sequence stratigraphy of the Amapá Formation, Late Paleocene to Early Eocene, Foz do Amazonas Basin, Brazil

On the basis of thin-section studies of cuttings and a core from two wells in the Amapá Formation of the Foz do Amazonas Basin, five main microfacies have been recognized within three stratigraphic sequences deposited during the Late Paleocene to Early Eocene. The facies are: 1) Ranikothalia grainstone to packstone facies; 2) ooidal grainstone to packstone facies; 3) larger foraminiferal and red algal grainstone to packstone facies; 4) Amphistegina and Helicostegina packstone facies; and 5) green algal and small benthic foraminiferal grainstone to packstone facies, divisible locally into a green algal and the miliolid foraminiferal subfacies and a green algal and small rotaliine foraminiferal subfacies. The lowermost sequence (S1) was deposited in the Late Paleocene–Early Eocene (biozone LF1, equivalent to P3–P6?) and includes rudaceous grainstones and packstones with large specimens of Ranikothalia bermudezi representative of the mid- and inner ramp. The intermediate and uppermost sequences (S2 and S3) display well-developed lowstand deposits formed at the end of the Late Paleocene (upper biozone LF1) and beginning of the Early Eocene (biozone LF2) on the inner ramp (larger foraminiferal and red algal grainstone to packstone facies), in lagoons (green algal and small benthic foraminiferal facies) and as shoals (ooidal facies) or banks (Amphistegina and Helicostegina facies). Depth and oceanic influence were the main controls on the distribution of these microfacies. Stratal stacking patterns evident within these sequences may well have been related to sea level changes postulated for the Late Paleocene and Early Eocene. During this time, the Amapá Formation was dominated by cyclic sedimentation on a gently sloping ramp. Environmental and ecological stress brought about by sea level change at the end of the biozone LF1 led to the extinction of the larger foraminifera (Ranikothalia bermudezi).     

First record ofBorelis melo andDendritina sp. in the Messinian of SE Spain (Cabo de Gata, Province Almeria)

Borelis melo andDendritina sp. occur in Messinian carbonates of the Cabo de Gata near Almeria. This is the first record of these larger benthic foraminifera from Messinian deposits in SE Spain. Two foraminiferal assemblages are differentiated: firstly, aBorelis- Dendritina assemblage which occurs on reef flanks, and secondly a lagoonal monospecificDendritina fauna.     

The Foram Stress Index: A new tool for environmental assessment of soft-bottom environments using benthic foraminifera. A case study from the Saronikos Gulf,Greece, Eastern Mediterranean

Saronikos Gulf, including the industrial zone of Elefsis Bay and the Port of Piraeus, is one of the most anthropogenically impacted coastal regions of Greece. Distinct assemblages of benthic foraminifers in sediment samples, collected from this gulf in February 2012, defined three zones that reflect abiotic parameters of the sediments (e.g., organic carbon, metal content). A low-diversity assemblage, dominated by stress-tolerant Ammonia tepida and Bulimina spp., was characteristic of samples from Elefsis Bay. Samples from the western and central part of Saronikos Gulf were the most variable with respect to both abiotic parameters and the foraminiferal assemblage, characterized by a mix of stress-tolerant and more sensitive taxa, especially Bolivina spp. and Nonion fabum. Samples from the coast of Salamis and at the eastern sector of the gulf were characterized by a diverse assemblage that included Peneroplis pertusus, miliolids, and a variety of small, epiphytic rotaliid taxa. A new biotic index, the Foram Stress Index (FSI), is based on the relative percentages of two ecological groups of benthic foraminiferal species, grouped according to their tolerance/sensitivity to organic matter enrichment and weighted proportionately to obtain a formula to define five ecological-status classes. The FSI produced three rankings for these samples (Poor, Moderate and Good), that strongly correlate with the macroinvertebrate-classification tool known as the BENTIX Index. The FSI provides a new tool to assess sediment or substrata quality based upon the benthic foraminiferal assemblages, which are a significant component of living meiobenthic communities that are generally not considered in most biotic benthic indices.     

Cluster analysis of recent benthic foraminifera from the northwestern Mediterranean coast of Egypt

A suite of 74 surface sediment samples, collected from two areas along the Egyptian Mediterranean coast (the Western Harbor of Alexandria and its environs, and the area comprising the Gulf of Kanayis and the Abu Hashafa Bay), have been examined for their benthic foraminiferal faunas. A total of 82 species were identified. Census data were obtained for different species in each sample and the statistically significant fractional abundances values (≥5%) were analyzed using a Q-mode cluster analysis. Samples were segregated into four clusters, each having its peculiar benthic faunal assemblage (biotope), reflecting particular environmental conditions. These clusters are: (1) the Ammonia beccarii forma tepida Biotope, found in samples located in areas with waters of low energy, characterizing semi-closed basin conditions, with muddy or sandy mud bottom sediments (Harbor Proper); (2) the Quinqueloculina spp. Biotope, found in samples collected from depths bathed by turbid inner shelf conditions with some fresh water inflow and sandy bottom sediments (Harbor’s environs); (3) the Peneroplis-Amphistegina Biotope, found in samples collected from depths characterizing marine shelf environments with calcareous algae, and medium to very coarse calcareous sands (the Gulf of Kanayis and the Abu Hashafa Bay); (4) the Triloculina trigonula-Adelosina laevigata Biotope was represented by only one sample (at the far eastern part of the Gulf of Kanayis), collected from a site exhibiting very restricted environmental conditions. The study suggests that nutrients, turbidity, light intensity, type of substrate, and salinity are the main ecological factors controllingthe distribution of benthic foraminifera.     

Heterosteginapapyracea Seguenza du Miocène du Corridor Sud-Rifain (Maroc) : biométrie et particularités paléoécologiques

Biometric study of the inner features of Heterostegina specimens preserved in tortonian sediments of the oued Yhoudi member allows to confirm the presence of species Heterostegina papyracea Seguenza, 1880. Analysis of both large and small components of the foraminiferal assemblage in all examined samples establishes the dominant character of species Heterostegina papyracea Seguenza (more than 60% of total benthic foraminifera). The assemblage of small benthic foraminifera associated with the Heterostegina is different from that described from Recent sediments, as well as from Miocene sediments of Calabria and Spain. In order to explain this result, two hypotheses can be put forward: (1) the Tortonian Heterostegina from Morocco proliferated abundantly in very shallow environments in association with small foraminifera (i.e. abundant Ammonia beccarii). (2) Because of powerful tidal currents in the South Rifian Corridor, Heterostegina tests were probably transferred after death. This transfer could possibly be due to the narrowness of the South Rifian Corridor in the Early Late Tortonian and its position between the Atlantic and the Mediterranean. Similar cases foraminiferal displacements are also known from modern basins. This study illustrates the difficulties in reconstructing the paleogeography of the studied area and the importance of considering all available components of the assemblage.     

Modern foraminiferal record of alternating open and restricted environmental conditions in the Santo André lagoon,SW Portugal

Benthic foraminifera from eleven stations sampled seasonally were analyzed in order to examine the biological response to rapid and intense environmental changes taking place in the Santo André coastal lagoon. Foraminiferal assemblages show a very low species diversity and a high dominance of three euryhaline species throughout the year. Under closed-inlet conditions, foraminiferal assemblages exhibit low abundance of foraminiferal tests, whereas under open-inlet conditions absolute abundance greatly increases due to sea water entrance. Present-day dramatic environmental changes are thought to be responsible for deformed foraminiferal tests that are commonly found. Comparison of modern assemblages with those obtained from the Holocene sedimentary record indicates persistent restrictive environmental conditions after sandy barrier formation, circa 5000 years ago.     

Pleistocene agglutinated foraminifera from the Lomonosov Ridge and Amundsen Basin, Arctic Basin. Initial report on piston cores 2177-5 (KAL) and 2176-3 (KAL)

Noncalcareous Pleistocene sediments of the Central Arctic Ocean contain sparse benthic foraminiferal assemblages consisting entirely of agglutinated taxa. Deep water agglutinated foraminifera are studied from two piston cores collected from the Lomonosov Ridge and Amundsen Basin [Cores PS 2177-5 (KAL) and 2176-3 (KAL)]. Core PS 2177-5 (KAL) contains an assemblage of 10 species, dominated by Cyclammina pusilla Brady, and is interpreted to reflect a bathyal environment with variable organic flux and nutrition levels. Core PS 2176-3 (KAL) in the Amundsen Basin yielded a very depauperate benthic foraminiferal assemblage. It is assumed that the environment was inhospitable for agglutinated foraminifera.     

Foraminiferal and ostracod ecological patterns in coastal environments of SE Andros Island (Middle Aegean Sea, Greece)

A comparative study of recent epiphytal ostracod and benthic foraminiferal populations was conducted in August 2001, at two gulfs (Korthi and Kastro) located at the southeastern part of Andros Island (middle Aegean Sea, Greece). Thirty samples (representing living macro-benthic algae and seagrasses) from both gulfs were studied and a total of 34 ostracod species and 60 benthic foraminiferal species were identified. In the gulf of Korthi both benthic foraminiferal and epiphytal ostracod assemblages were characterized by high abundances of Amphistegina lessonii and Xestoleberis spp., respectively, therefore the performed Q-mode cluster analysis verified the presence of a Normal Environment Biofacies (NE). Declined Environment (DE) and Stressed (SE) Environment Biofacies were recognized in the gulf of Kastro, an area more affected by anthropogenic activities. Several deformed foraminiferal specimens have been documented in the assemblages from both gulfs, but malformed tests are significantly increased in SE Biofacies of Kastro gulf. This study suggests that great accumulations of A. lessonii (35-60%) associated with high frequencies of Xestoleberis communis and/or Xestoleberis decipiens and high species diversities can be used as bioindicators of coastal health.     

Deep-sea benthic foraminiferal recolonisation following a volcaniclastic event in the lower Campanian of the Scaglia Rossa Formation (Umbria–Marche Basin,central Italy)

We studied the distribution of deep water agglutinated foraminiferal (DWAF) assemblages across a 15-cm-thick volcaniclastic layer in the lower Campanian Scaglia Rossa limestones of the Umbria–Marche Basin. Above the volcaniclastic layer, which is devoid of foraminifera, a remarkable pattern of recovery among DWAF has been observed. The complete recovery of DWAF in terms of trophic groups and complexity of assemblages is observed in the first 5 cm above the volcaniclastic layer, representing 4.8 kyr based upon the mean sedimentation rate of the Campanian Scaglia Rossa Formation.In its initial stage, the recovery pattern is remarkably similar to that observed following the 15 June 1991 Mount Pinatubo ashfall in the abyssal South China Sea where various species of Reophax, a small organically cemented species of Textularia, and the calcareous species Quinqueloculina seminula and Bolivina difformis are the earliest recolonisers on top of the tephra layer.Such similarities between modern and fossil analogues strengthens the reliability of environmental reconstructions based on DWAF.     

Effectiveness of benthic foraminiferal and coral assemblages as water quality indicators on inshore reefs of the Great Barrier Reef, Australia

Although the debate about coral reef decline focuses on global disturbances (e.g., increasing temperatures and acidification), local stressors (nutrient runoff and overfishing) continue to affect reef health and resilience. The effectiveness of foraminiferal and hard-coral assemblages as indicators of changes in water quality was assessed on 27 inshore reefs along the Great Barrier Reef. Environmental variables (i.e., several water quality and sediment parameters) and the composition of both benthic foraminiferal and hard-coral assemblages differed significantly between four regions (Whitsunday, Burdekin, Fitzroy, and the Wet Tropics). Grain size and organic carbon and nitrogen content of sediments, and a composite water column parameter (based on turbidity and concentrations of particulate matter) explained a significant amount of variation in the data (tested by redundancy analyses) in both assemblages. Heterotrophic species of foraminifera were dominant in sediments with high organic content and in localities with low light availability, whereas symbiont-bearing mixotrophic species were dominant elsewhere. A similar suite of parameters explained 89% of the variation in the FORAM index (a Caribbean coral reef health indicator) and 61% in foraminiferal species richness. Coral richness was not related to environmental setting. Coral assemblages varied in response to environmental variables, but were strongly shaped by acute disturbances (e.g., cyclones, Acanthaster planci outbreaks, and bleaching), thus different coral assemblages may be found at sites with the same environmental conditions. Disturbances also affect foraminiferal assemblages, but they appeared to recover more rapidly than corals. Foraminiferal assemblages are effective bioindicators of turbidity/light regimes and organic enrichment of sediments on coral reefs.