Comparisons among colonization of artificial substratum types and natural substratum by benthic macroinvertebrates

A field study was designed to concurrently evaluate differences in colonization by benthic macroinvertebrates on a range of artificial substratum types (single particles of natural rock or clay brick and baskets of natural substratum) after three colonization periods (1, 8 and 29 days). Fauna on the artificial substrata were compared to natural substratum and the effect of natural epilithic cover on colonization by zoobenthos was determined. Densities of total number of organisms and the seven most abundant taxa, total number of taxa and quantity of organic material were greater on the natural substratum than on the artificial substratum types. Relative abundances of taxa on pairs of the artificial substratum types, unlike pairs of each artificial substratum type and the natural substratum, were statistically correlated. Among the artificial substratum types densities of total number of organisms and about one-half of the most abundant taxa, total number of taxa and quantity of organic material were greatest in the substratum baskets. Natural epilithic cover on the single rock particles and substratum baskets affected the densities of total number of organisms and two of the seven most abundant taxa. These taxonomic groups were at approximately two to six-fold greater densities on the substrata with fine sediment. consistent patterns in densities of the zoobenthos on the substrata were found after each colonization period. In our study all measures of the macroinvertebrate assemblages (densities of each taxon, total number of organisms, total number of taxa and relative abundances of taxa), with few exceptions, were different between each artificial substratum type and natural substratum. This result showed the abundance and composition of the macroinvertebrate fauna on artificial substratum types were different from the natural substratum. Therefore, the choice of using artificial substrata instead of direct sampling of the natural substratum should be carefully made. Among the artificial substratum types relative abundances of taxa were similar on the single substratum particles and substratum baskets indicating single particles instead of baskets might be used to sample the zoobenthos. Investigators should consider the potential effect of the natural epilithic cover of substratum particles on colonization by zoobenthos when choosing the type of artificial substratum.     

Short-term uptake of heavy metals by periphyton algae

Benthic invertebrates in a tropical river (Menik Ganga) recolonised denuded substrates within 2–3 weeks, though full diversity was not achieved until 4 weeks. No well defined succession was observed. All taxa apparently colonised at random from drift, upstream and vertical sources. Traps colonised from only one of these sources developed as abundant and diverse a fauna as control traps in 5 weeks. Strong spatial heterogeneity in the number and composition of colonisers was observed between replicate traps. It is suggested that colonisation resulted from random foraging activities and most colonists were derived from veryshort distances.     

The interplay of physical and biological factors in maintaining mid-shore and low-shore assemblages on rocky coasts in the north-west Mediterranean

This study examined the interactive effects of grazing by limpets and inclination of the substratum in maintaining differences between mid-shore and low-shore assemblages of algae in the northwest Mediterranean, at different scales of space and through time. Alternative models leading to different predictions about these effects were proposed and tested. Limpets were excluded by fences from areas of the substratum at mid levels on the shore. The response of algal assemblages to this manipulation was compared with control and enclosure plots at the same level, and with unmanipulated plots in the low shore where limpets are less abundant. The effects of limpets were examined at several replicated sites (0.1–4 km apart) for each slope of the substratum (nearly horizontal vs vertical), at different locations (hundreds of kilometres apart) and at different times. Individual taxa responded differently to limpet exclusion. The percentage cover of the coarsely branched and filamentous algae increased significantly in exclosure plots, in some loser reaching values found on the low shore. These patterns, however, varied greatly from shore to shore and significant effects were found both on horizontal and vertical substrata. Multivariate analyses indicated that grazing by limpets accounted for about 20% of the differences between mid-shore and low-shore assemblages. This effect was independent of substratum inclination and was consistent in space and time, suggesting that physical conditions were not as stressful for macroalgae on vertical substrata as initially supposed. Variable recruitment of algae is proposed as a possible explanation for the lack of consistency in the effects of limpets at the scale of the shore. The results of this study emphasize the need for multiple-scale analyses of the interactive effects of physical and biological factors to understand the organization of natural assemblages. Received: 22 June 1999 / Accepted: 15 November 1999     

Benthic macro- and meso-invertebrates of a sandy riverbed in a mountain stream, central Japan

Quantitative samples of benthic invertebrates were collected from a sandy riverbed of a mountainous stream (Kozu site of Takami-gawa stream, Nara Prefecture), central Japan by core samplers in five sampling occasions through the years 2008–2009. A total of 120 taxa were identified, representing 55 families and 97 genera. Insects formed about 92% of the total recorded taxa and 88% of individuals’ abundance. A total of 111 taxa of aquatic insects, belonging to 49 families and 92 genera, were identified and represented by ten orders. Oligochaeta and Acari were dominant non-insect invertebrates. Diptera was the most diverse insect group, followed by Trichoptera and Ephemeroptera. Dominant taxa were mesoinvertebrates, younger stages of macroinvertebrates, both of which predominantly inhabit the interstitial zone of a sandy riverbed. Both taxon richness and invertebrate abundance were higher in February 2009 and lower in April and August 2008. A few major invertebrate taxa demonstrated distinct seasonal trends; i.e. Nymphomyia alba, Rheosmittia, and Corynoneura were abundant in February 2009. Newly hatched larvae of Larcasia akagiae were abundant in May 2008. This study also demonstrated the effectiveness of core samplers to collect small-sized benthic fauna that inhabit the interstitial or hyporheic zone of the sandy riverbed.     

Fish assemblages on artificial and natural reefs in the Flower Garden Banks National Marine Sanctuary, USA

 Visual censusing was used to characterize fish assemblages on artificial and natural reefs located within the boundaries of the Flower Garden Banks National Marine Sanctuary (FGBNMS) in the northwestern Gulf of Mexico. Emphasis was placed on determining spatial and temporal patterns in habitat utilization by fishes on an offshore artificial reef (Mobil Platform HI-A389A). Overall, 43 species were observed during diurnal surveys in the upper 24 m of the artificial reef. Midwater pelagic fishes (i.e., carangids and scombrids) accounted for over 50% of all taxa enumerated on the artificial reef; however, these taxa were transient members of the assemblage and were observed infrequently. Labrids, pomacentrids, and serranids were the dominant reef-dependent taxa. Distinct trends in vertical, diel, and seasonal abundances were observed for juvenile and adult fishes. Of the three designated depth zones (upper 1.5–9.0, middle 9.0–16.5; lower 16.5–24.0 m), abundance and species diversity were lowest in the upper zone. Nocturnal counts were characterized by a marked reduction or complete absence of most species, due in part to twilight cover-seeking and movement activities. Seasonal variation in community composition and species abundance (May versus September) was primarily due to recruitment of juveniles (0-age fishes) to the artificial reef in late summer. Increases in total fish abundance (all taxa combined) coincided with both increasing habitat rugosity and degree of fouling. Species richness on natural coral reefs in the FGBNMS was higher than on the artificial reef. Unlike the artificial reef, fish assemblages on the natural reefs were dominated by a single family (Pomacentridae) which accounted for over 50% of all individuals observed. Accepted: 1 August 1996     

Hyporheic Production is Substantially Greater than Benthic Production for a Common New Zealand Caddisfly

Life-history and production of Olinga feredayi in both benthic and hyporheic stream habitats were investigated in a pristine Waikato, New Zealand, forest stream over two years to investigate the contribution of hyporheic habitat to total secondary production. O. feredayi had a univoltine life-history with adult emergence occurring from November to March. Larvae with case lengths < 2 mm were present on most dates suggesting delayed egg hatching. Benthic densities were inversely related to maximum peak daily flow in the month prior to sampling, and positively related to the dry mass of particulate organic matter present in samples. Reach-average benthic production calculated by the size-frequency method was 0.024 g DM m⁻² year⁻¹. Hyporheic production was 4.276 g DM m⁻³ year⁻¹ and 6.462 g DM m⁻³ year⁻¹ in colonisation baskets set at 15–30 cm and 30–45 cm within the substratum, respectively, 2.3–3.4 times greater than production in surface baskets (0–15 cm). Averaged out over the reach scale, it was estimated that 96% of annual secondary production of O. feredayi occurred in hyporheic habitats >10 cm below the streambed surface. Our study clearly demonstrates that only sampling benthic habitats can lead to gross under-estimation of population-level annual production, and provides evidence for the role of the hyporheos as a source of secondary production that may partly account for the Allen Paradox.     

The influence of initial colonization by hydropsychid caddisfly larvae on the development of stream invertebrate assemblages

Many aspects of the colonization history of a disturbed site can influence the development of a biological community. Initial colonization is known to play a significant role in community development because of the facilitative or inhibitory effects that `pioneer' species can have on subsequently arriving taxa. We performed an experiment to assess how initial colonization by two species of benthic invertebrates (Trichoptera: Hydropsychidae) might influence the development of stream faunal assemblages. Substrate baskets initially colonized by either Hydropsyche depravata or Ceratopsyche bronta were placed alongside control baskets in a recently flooded stream. After baskets had colonized for 30 days, we found that species composition in treatment baskets was identical to that in control baskets, indicating that the caddisfly taxa had no selective effects on colonization of other macroinvertebrate species. We did, however, find that C. bronta facilitated the recruitment of all species in the colonist pool leading to greater overall abundance and biomass of macroinvertebrates in the final assemblages. In contrast, H. depravata had no effect on the abundance or biomass of colonizing invertebrates. The differential effects of these two taxa on abundance and biomass may have been related to differences in microhabitat complexity created by the construction of their retreats and catchnets. The results of this study support the growing recognition that colonization history does influence the structure of lotic communities, but they also suggest that even closely related taxa can play different roles as initial colonists in community development.     

Land‐use legacy and the differential response of stream macroinvertebrates to multiple stressors studied using in situ experimental mesocosms

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Long-term changes in a benthic assemblage associated with artificial reefs

The aim of the study was to evaluate the long-term development of a hard bottom benthic assemblage over a period of 20 years in an area off the mouth of a large river. The artificial reef of Fregene was selected because benthic assemblage data were available for the period 1981–1992. This artificial reef is located in the mid Tyrrhenian Sea, 5 nautical miles north of the two mouths of the Tevere River (Latium, Italy) and 1.5 nautical miles offshore from Fregene (Rome, Italy). The artificial reef was deployed in March 1981 for fisheries enhancement in 10–14 m of water on a sandy-silty seabed. The Tevere River carries suspended materials and a heavy load of organics since it transports Rome’s effluent, resulting in the eutrophic state of area waters. Benthic sampling was conducted in 2001 by SCUBA diving; two standard surfaces of 400 cm² were scraped from the vertical walls of the same uppermost block in four different periods. All organisms were identified and counted. The methodology used is the same as that adopted in the previous periods, so that the 2001 data could be compared with past collected data. The benthic assemblage was analysed by cluster analysis using the Bray-Curtis index and clustered using the group average clustering algorithm. The SIMPER procedure was used to identify those taxa that characterize each station group identified by cluster analysis. Changes in benthic assemblages and hydrological trends of the Tevere River were investigated using the cumulative sum series method. The 20-year development of the benthic community, starting from the new substratum, is composed of different phases characterised by different benthic assemblages. In particular five different phases were distinguished: 1. Pioneer species recruitment (May 1981–June 1981); 2. Mytilus galloprovincialis (mussel) dominance (August 1981–November 1983); 3. M. galloprovincialis regression (July 1984–October 1985); 4. M. galloprovincialis absence (91–92); 5. Bryozoans bioconstruction dominance (2001). The dynamic succession of the observed benthic assemblages exhibited a good relation with the Tevere River flow. The Tevere River flow, and the subsequent sedimentation process, seems to have strongly influenced the benthic assemblage succession of the Fregene artificial reef. Guest editors: G. Relini & J. Ryland Biodiversity in Enclosed Seas and Artificial Marine Habitats     

Responses of ground-active beetle assemblages to different styles of reforestation on cleared rainforest land

Despite increasing efforts to re-establish forest cover in landscapes that have been previously cleared, the relative ability of different styles of reforestation to contribute to conservation and support forest biota is poorly known, particularly for invertebrates. We investigated the use of different types of reforested habitat by ground-active rainforest beetle assemblages on land, which had been previously cleared of rainforest, in the tropics and subtropics of eastern Australia. Between five and ten replicate sites within each of five reforestation styles were selected in each region: un-managed regrowth, young mono-species timber plantations, young mixed-species timber plantations, ecological restoration plantings, and old mono-species timber plantations, together with reference sites in pasture and in intact rainforest. Ground-active beetles were sampled using pitfall traps, and assemblages were compared among site-types. In both regions, beetle assemblages in all styles of reforestation were intermediate in species composition between pasture and rainforest. The similarity of beetle assemblages to intact rainforest increased with the age and structural complexity of reforested sites. The most rainforest-like beetle assemblages were from older reforestation sites (38–70 year plantations in tropics, and 30–40 year regrowth in subtropics) and in younger (6–22 years) but floristically and structurally diverse ecological restoration plantings in both regions. Assemblages in younger (5–20 year) sites of regrowth, mono-species timber plantations, and mixed-species timber plantations were more similar to pasture than rainforest. We conclude that achieving high canopy cover and sufficient structural complexity are important factors associated with the restoration of rainforest-like beetle assemblages to reforested sites.     

Anadromous alewives,Alosa pseudoharengus,as prey for white perch,Morone americana

Macroinvertebrates continuously redistribute themselves in the riverbed. A knowledge of the colonization mechanisms and movement patterns is very important for an understanding of processes of restoration of lotic environments, particularly of inland waters with severe pollution. We tested the colonization patterns of stream macroinvertebrates in the Visone River, a tributary of the highly contaminated Bormida River (NW Italy). We placed six groups of traps in the riverbed, each group consisting of three traps: the C trap allowed colonization from all directions, while the D and U traps allowed access only from downstream and upstream respectively. The C traps were the most colonized substrates, both in number of individuals and taxa. The U traps were more colonized than the D traps, demonstrating the great importance of movements directed downstream. We report data on taxonomic and seasonal differences in the colonization process.     

Recolonisation patterns of benthic invertebrates: a field investigation of restored former sewage channels

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First survey of interstitial fauna in New Caledonian rivers: influence of geological and geomorphological characteristics

Despite zoogeographical implications and geological anomalies, the interstitial fauna of New Caledonian rivers remains unstudied. During this first survey, 15 different sized rivers varying in sediment grain size and geological substratum were sampled for both benthic (Surber sampler) and interstitial (Karaman-Chappuis pits) invertebrates during summer 1998–99. A total of 34 taxa was collected during the study, of which 22 were present in the sediment interstices. Interstitial assemblages were dominated by the Oligochaeta (present in 80% of the samples), the Chironomidae (in 73%), the Ceratopogonidae (in 73%), the Coleoptera Berosini (in 47%), the Turbellaria (in 47%), the OstracodaVestalenula sp. (in 40%) and the Copepoda Cyclopoida (in 40%). New amphipods close to Bogidiellidae were found in two stations. Some organisms, frequent and abundant in the benthic layer, were rare or absent in the sediment interstices (e.g. Decapoda Atyidae, Ephemeroptera Leptophlebiidae, Trichoptera Hydropsychidae and Leptoceridae, Diptera Simulidae). River size and distance between the station and the ocean were unassociated with abundance, taxonomic richness or composition of interstitial assemblages. In contrast, both abundance and taxonomic richness were significantly lower when sediment grain size decreased (probably because of low exchange with surface assemblages) and when the percentage of peridotitic substratum in the catchment increased (probably because of its high nickel and chromium contents). These preliminary results suggest that interstitial fauna can be used for ecological survey and river management even in tropical regions.     

Characterization,Ecological Status and Type-specific Reference Conditions of Surface Water Bodies in Wallonia (Belgium) using Biocenotic Metrics based on Benthic Invertebrate Communities

The river types in Wallonia (Belgium) were defined according to the system B of the European Water Framework Directive (WFD) taking into account obligatory and optional factors synthesized in three criteria: ‘size’, ‘slope’ and ‘natural region’. Under the hypothesis that benthic invertebrate assemblages would be specialized according to river type, a set of 627 faunal samples originating from an 11-year sampling period was tested to characterize river types with faunal assemblages. A multivariate approach led to gather 23 river types into seven groups exhibiting similar faunal assemblages. Using biocenotic metrics based on benthic invertebrate assemblages (e.g., the French standard IBGN), type-specific reference conditions and ecological status class limits were defined for each ‘natural’ river type group. Ecological potential was defined for heavily modified and for artificial (i.e., man-made canals) types. An ‘ecological status’ evaluation strategy was therefore developed and applied in the southern – and more natural – part of Wallonia, where many reference sites were available. In the northern part of Wallonia (i.e., the ‘Loess region’) where no high quality site was available, the expert judgement took a larger part in the definition of the reference conditions and of the ecological status class limits, in addition to the calculations. Two independent distribution gradients of taxa assemblages resulted from multivariate ordination: a first ‘saprobity axis’, as the taxa-sensitivity to organic contamination was increasing from ‘very resistant’ taxa (mainly located in the ‘Loess region’) to ‘sensitive’ and ‘very sensitive’ taxa (from the river types belonging to the Condroz, the Famenne, the Arden and the Jurassic regions) and a second axis characterizing the Meuse-specific faunal assemblage, gathering exotic species and typical limnophilous taxa of large heavily modified rivers. The ecological status monitoring management system developed in this study – i.e., the definition of faunal river type groups, related reference conditions and ecological status class limits – represents a proposal to be integrated in the ecological status assessment of biological elements for the implementation of the WFD and was tested in Wallonia. For the period 2000–2002 involving 349 different sites, the element ‘benthic invertebrate fauna’ was in that way classified ‘high status’ for 31.5% of sites, ‘good status’ for 31.5% and below ‘good status’ for 37% of sites. The best ecological status (i.e., 100% ‘high’ and ‘good’ status) was found in river type ‘Arden’s xenotrophic brooks with strong slope’ and in river types 8large rivers with medium slope’. The worst status was found in river types ‘Loess brooks and rivers with medium slope’.     

Ecology of the introduced snapper Lutjanus kasmiva (Forsskal) in the reef fish assemblage of a Hawaiian bay

Since its first introduction in 1955, the snapper Lutjanus kasmira (taape) has developed large populations in shallow coastal waters of Hawaii. Visual abundance estimates and trap catches of taape were different between the main habitat types of the reef. Overall, taape was the second most abundant species by numbers and biomass over a hard substratum and was patchily distributed, even within habitat type. The largest individuals occurred singly or in small groups on shallow reef slopes; on the deep slopes and in spur-and-groove habitat, taape occurred in larger groups of smaller sized fish. Catches in fish traps showed a negative relationship with the complexity of the adjacent natural substratum, suggesting that traps are more productive where they offer additional cover in areas with less natural cover. In all areas in which traps were used, from fringing reef to open sand, the catch was dominated by taape. Tagging confirmed the theory that taape tend to maintain a limited range over long periods. Tagging results also indicated occasional long-range movements among major habitats and provided data confirming patterns of movement between reef habitat by day and sand habitat by night. Taape collected over open sand substratum by trap and by hook-and-line were smaller than those collected by the same means at the reef. Observations and collections suggested an ontogenetic trend in habitat use by taape from initial settlement in fringe areas toward ultimate residence on the main reef. Other common fish species in the reef assemblages were tested for statistical associations with taape. Although several positive species associations were found, multivariate analysis did not reveal patterns that indicated strong ecological relationships.     

The typology of floodplain water bodies of the Middle Danube (Slovakia) on the basis of the superficial polychaete and oligochaete fauna

The oligochaete fauna of different side arms and other water bodies in the Slovak–Hungarian stretch of the River Danube below Bratislava (r.km 1840 – r.km 1807) was investigated. The structure of the oligochaete assemblages is correlated with the bottom substratum of the river. From data on the composition of the oligochaete fauna, the clustering and ordination analysis divided the inland delta water bodies into three groups supporting the river classification of Roux et al. (1982), i.e. eupotamon, parapotamon and plesiopotamon, but parapotamon and plesiopotamon divided furthermore into two subgroups, which better reflects hydrological conditions, type of substratum, depth of water bodies and presence of macrophytes. Oligochaete assemblages differ in individual type of group and subgroups, not only species composition, but mainly quantitative (average abundance). This revised version was published online in July 2006 with corrections to the Cover Date.     

Tyrrhenian basins of Ligury as a new peri-Mediterranean ichthyogeographic district? Population structure of <Emphasis Type="Italic">Telestes muticellus</Emphasis> (Osteichthyes,Cyprinidae), a primary freshwater fish

The phylogeographic structure of vairone (Telestes muticellus), a primary freshwater fish endangered in a large part of its distributional range, was assessed: (i) to reconstruct the complex dispersion pattern in the upper Tyrrhenian hydrographic basins of Ligury, actually not recognised as peri-Mediterranean ichthyogeographic district, and (ii) to evidence the shape of population genetic structure as useful tool for future conservation strategies. A partial fragment of mitochondrial DNA cytochrome b (497 bp) was sequenced in 109 specimens sampled from eight populations, along an east–west geographic gradient. Fourteen haplotypes were identified, confirming the evolutionary distance between the two co-generic species: T. muticellus as ‘Ligurian’ clade and T. souffia as ‘French’ clade. The Nested Clade Analysis (NCA), the population genetic variability and population structure suggested a natural colonization occurred throughout the crossing of Alpine and Apennine watershed. The hierarchical Analysis of Molecular Variance (AMOVA) confirmed a geographic distinction between the populations from western (WTL) and from eastern (ETL) Tyrrhenian basins of Ligury colonised through the river capture processes along the Maritime Alpine watershed (Padano-Venetian district) and along the Apennine watershed (Tuscano-Latium district), respectively. Our results, evidencing the lack of genetic contiguity among vairone populations of the upper Tyrrhenian hydrographic basins of Ligury, allowed to recognise the presence of two management units (MUs) for its conservation. Handling editor: Christian Sturmbauer     

Does lake age affect zooplankton diversity in Mediterranean lakes and reservoirs? A case study from southern Italy

Zooplankton assemblages of 51 lacustrine environments located in the middle of the Mediterranean Region were analysed to evaluate the existence of an ‘age effect’ in determining their structure. The analysed datasets refer to two different geographic areas, one comprising 30 natural and artificial lakes in Sicily and the other an arrangement of 21 analogous aquatic ecosystems located at the bottom of the Italian Peninsula, a more pristine area called Southern Apennine region. Most of the natural lakes are of post-glacial origin. The artificial lakes in both datasets were built in the last century and offer the opportunity to evaluate the possible short-term effects of ageing on the structure of their zooplankton. A comparison of assemblages in the two regions by PERMANOVA and nMDS revealed that they are quite different; therefore they were analysed separately. An explorative analysis on the possible relationship between biological data and environmental data (including lake age) was performed on both datasets using DISTLM. The presence of an ‘age effect’ emerged only in the subset of artificial lakes of the Southern Apennine region; accordingly it was tested more in detail with an a posteriori PERMANOVA analysis in the subset of reservoirs that resulted positive in the first test. SIMPER allowed us to single out the main species responsible of changes in the zooplankton along the selected age groups. No age effect was evident in the Sicilian water bodies, where other variables, such as conductivity, trophic state, urbanisation and water level fluctuations proved to have a major role in shaping zooplankton assemblages. The results showed that the age effect is: (i) detectable only at a time scale of decades; (ii) masked by the human impact in the watershed.     

Spatial and temporal variations of assemblages in a Mediterranean coralligenous reef and relationships with surface orientation

The structure, distribution, and temporal changes of epibenthic assemblages of a Mediterranean coralligenous reef were investigated using a multifactorial sampling design. The distribution of taxa on vertical walls and down-facing surfaces of overhangs and crevices was analysed at ten sites along 2 km of rocky reefs, south of Livorno (Ligurian Sea, Italy). The temporal variations were analysed between two periods (1995–1996 and 1997–1998) and among four sampling times within each period. Most of the space was dominated by prostrate seaweeds (including Peyssonnelia rubra, P. rosa-marina, and Mesophyllum lichenoides), turf-forming seaweeds, and the red coral Corallium rubrum. The cover of a variety of other invertebrates, mainly sponges and bryozoans, was less than 2%. All taxa were found on both vertical and down-facing surfaces. However, seaweeds dominated the vertical surfaces (mean cover >97%), while C. rubrum and other invertebrates dominated down-facing surfaces (mean density of C. rubrum >16 colonies dm⁻²). Although there was some fluctuation in the abundance of taxa, no obvious patterns were observed. These results support the model of limited temporal variability in Mediterranean coralligenous reefs, possibly related to the slow growth rates of the most abundant taxa and the reduced seasonality of physical conditions.     

Neogene reef coral assemblages of the Bocas del Toro region, Panama: the rise of Acropora palmata

Temporal patterns are evaluated in Neogene reef coral assemblages from the Bocas del Toro Basin of Panama in order to understand how reef ecosystems respond to long-term environmental change. Analyses are based on a total of 1,702 zooxanthellate coral specimens collected from six coral-bearing units ranging in age from the earliest Late Miocene to the Early Pleistocene: (1) Valiente Formation (12–11 Ma), (2) Fish Hole Member of the Old Bank Formation (5.8–5.6 Ma), (3) La Gruta Member of the Isla Colon Formation (2.2–1.4 Ma), (4) Ground Creek Member of the Isla Colon Formation (2.2–1.4 Ma), (5) Mimitimbi Member of the Urracá Formation (1.2–0.8 Ma), and (6) Hill Point Member of the Urracá Formation (1.2–0.8 Ma). Over 100 coral species occur in the six units, with faunal assemblages ranging from less than 10% extant taxa (Valiente Formation) to over 85% extant taxa (Ground Creek Member). The collections provide new temporal constraints on the emergence of modern Caribbean reefs, with the La Gruta Member containing the earliest occurrence of large monospecific stands of the dominant Caribbean reef coral Acropora palmata, and the Urracá Formation containing the last fossil occurrences of 15 regionally extinct taxa. Canonical correspondence analysis of 41 Late Miocene to Recent reef coral assemblages from the Caribbean region suggests changes in community structure coincident with effective oceanic closure of the Central American Seaway (~3.5 Ma). These changes, including increased Acropora dominance, may have contributed to a protracted period of elevated extinction debt prior to the major peak in regional coral extinctions (~2–1 Ma).