Phase shift to algal dominated communities at mesophotic depths associated with lionfish (<Emphasis Type="Italic">Pterois volitans</Emphasis>) invasion on a Bahamian coral reef

Mesophotic coral reefs (30–150 m) have been assumed to be physically and biologically connected to their shallow-water counterparts, and thus may serve as refugia for important taxonomic groups such as corals, sponges, and fish. The recent invasion of the Indo–Pacific lionfish (Pterois volitans) onto shallow reefs of the Caribbean and Bahamas has had significant, negative, effects on shallow coral reef fish populations. In the Bahamas, lionfish have extended their habitat range into mesophotic depths down to 91 m where they have reduced the diversity of several important fish guilds, including herbivores. A phase shift to an algal dominated (>50% benthic cover) community occurred simultaneously with the loss of herbivores to a depth of 61 m and caused a significant decline in corals and sponges at mesophotic depths. The effects of this invasive lionfish on mesophotic coral reefs and the subsequent changes in benthic community structure could not be explained by coral bleaching, overfishing, hurricanes, or disease independently or in combination. The significant ecological effects of the lionfish invasion into mesophotic depths of coral reefs casts doubt on whether these communities have the resilience to recover themselves or contribute to the recovery of their shallow water counterparts as refugia for key coral reef taxa.     

The extent and significance of petroleum hydrocarbon contamination in Crater Lake,Oregon

In order to evaluate hydrocarbon inputs to Crater Lake from anthropogenic and natural sources, samples of water, aerosol, surface slick and sediment were collected and analyzed by gas chromatography-mass spectrometry (GC-MS) for determination of their aliphatic and aromatic hydrocarbon concentrations and compositions. Results show that hydrocarbons originate from both natural (terrestrial plant waxes and algae) and anthropogenic (petroleum use) sources and are entering the lake through direct input and atmospheric transport. The concentrations of petroleum hydrocarbons range from low to undetectable. The distributions and abundances of n-alkanes, polycyclic aromatic hydrocarbons (PAH) and unresolved complex mixture (UCM) from petroleum are similar for all surface slick sampling sites. The estimated levels of PAH in surface slicks range from 7–9 ng/m² which are low. Transport of petroleum-derived hydrocarbons from the lake surface has resulted in their presence in some sediments, particularly near the boat operations mooring (total petroleum HC = 1440 μg/kg, dry wt. compared to naturally derived n-alkanes, 240 μg/kg, dry wt.). The presence of biomarkers such as the tricyclic terpanes, hopanes and steranes in shallow sediments further confirms petroleum input from boat traffic. In the deep lake sediments, petroleum hydrocarbon concentrations were very low (16 μg/kg, dry wt.). Very low concentrations of PAH were detected in shallow sediments (17–40 μg/kg at 5 m depth near the boat operations) and deep sediments (3–15 μg/kg at 580 m depth). The individual PAH concentrations in sediments (μg/kg or ppb range) are at least three orders of magnitude less than reported threshold effects levels (mg/kg or ppm range, test amphipod Hyalella azteca). Therefore, no adverse effects are expected to occur in benthic biota exposed to these sediments. Boating activities are leaving a detectable level of petroleum in surface waters and lake sediments but these concentrations are very low.     

Caprellids (Crustacea: Amphipoda) from India

The caprellid fauna of India is investigated. A total of 538 samples (including algae, seagrasses, sponges, hydroids, ascidians, bryozoans, encrusted dead corals, coral rubble, fine and coarse sediments) were collected from 39 stations along the coast of India, covering a wide diversity of habitats from intertidal to 12 m water depth. A new species (Jigurru longimanus n.sp.) is described, and figures of the 11 valid species reported so far from India are given together with a key for their identification. No caprellids were found in sediments from the northeast (16–20oN) coast of India while they were abundant in the southeast and west coast. Decreases in salinity due to river discharges associated with lower values of oxygen, higher water temperatures and lower nutrient inputs along the east coast could explain these differences in caprellid composition between the two coastlines. Significantly, lower abundance of caprellids in India, as in other tropical ecosystems, is probably related to the lack of species belonging to the genus Caprella, which reach very high abundances in temperate waters.     

Sedimentation on Rasdhoo and Ari Atolls, Maldives, Indian Ocean

A first systematic study of composition, texture, and distribution of modern sediments in two Maldivian atolls reveals the predominance of skeletal carbonates. Fragments of corals, calcareous algae, mollusks, benthic foraminifera, and echinoderms are identified in the grain-size fraction >125 μm. Non-skeletal grains such as cemented fecal pellets and aggregate grains only occur in small percentages. Fragments of skeletal grains, aragonite needles, and nanograins (<1 μm) are found in the grain-size fraction <125 μm. Needles and nanograins are interpreted to be largely of skeletal origin. Five sedimentary facies are distinguished (1–5), for which the Dunham-classification is applied. Fore reef, reef, back reef, as well as lagoonal patch reef and faro areas in both atolls are characterized by the occurrence of coral grainstones (1), which also contain fragments of red coralline algae, the codiacean alga Halimeda, and mollusks. On reef islands, coral-rich sediment is cemented to form intertidal beachrock and supratidal cayrock. Skeletal grains in atoll-interior lagoons are mainly mollusks and foraminifera. The lagoon of Rasdhoo Atoll is covered in the west by mudstones (2), in the center by mollusk packstones (3) and mollusk wackestones (4), and by hard bottoms with corals in the east adjacent to channels through the atoll reef margin. The interior lagoon of Ari Atoll contains mollusk wackestones (4) in the center and mollusk-foraminifer packstones (5). Marginal lagoon areas are characterized by hard bottoms with corals. Facies distribution appears to be an expression of depositional energy, which decreases from the atoll margin towards the center in Ari Atoll, and towards the west in Rasdhoo Atoll. Predominant sediment mineralogies include aragonite and high-magnesium calcite. Mean aragonite content decreases from 90% in coral grainstone to 70–80% in mollusk packstone, mollusk wackestone, and mudstone, and to 50% in mollusk-foraminifer packstone. Stable isotopes of oxygen and carbon in bulk samples range from −3 to −1.5 (δ¹⁸O) and from +0.4 to +3.2 (δ¹³C). It is not possible to delineate facies based on O- and C-isotopes.     

A late Devonian (Frasnian) coral-bafflestone reef at Houshan in Guilin, South China

Summary Givetian to early Carboniferous sediments of South China are characterized by carbonates. Middle and Late Devonian strata are best developed in the Guilin area. Reefs and organic shoals are recorded by various lithofacies types indicating the existence of an extended carbonate platform and a change of the composition of reef communities in time. Starting in the late Devonian, stromatoporoids and corals were replaced by algae that subsequently played an important role together with stromatoporoids, receptaculitids and fasciculate rugose corals in reef communities. In Houshan, 5 km west of Guilin, a coral-bafflestone reef occurs in the Frasnian strata, situated near an offshore algal-stromatoporoid reef. The coral reef was formed in a back-reef area adjacent to the inner platform margin. The coral-bafflestone reef is unique among the late Devonian reefs of South China with regard to the biotic composition. The reef is composed of fasciculate colonies ofSmithiphyllum guilinense n. sp. embedded within in packstones and wackestones. The height of colonies reaches 1 m. The community is low-diverse. The species ofSmithiphyllum occurring in the Frasnian reef complexes of Guilin exhibit a distinct facies control:Smithiphyllum guilinense occurs in or near to margin facies and formed bafflestone, constituting a coral reef whereasSmithiphyllum occidentale Sorauf, 1972 andSmithiphyllum sp.—characterized by small colonies with thin corallites—are restricted to the back-reef and marginal slope facies. The bush-like coral colonies baffled sediments. Algae and stromatoporoids (mainlyStachyodes) are other reef biota. Reef-dwelling organisms are dominated by brachiopods. The reefs are composed from base to top of five lithofacies types: 1) cryptalgal micrite, 2) peloidal packstone, 3) stromatactis limestone, 4) coral-bafflestone, and 5) pseudopeloidal packstone. The reef complex can be subdivided into back-reef subfacies, reef flat and marginal subfacies, and marginal fore-slope subfacies. The Houshan coral-bafflestone reef is not a barrier reef but a coral patch reef located near the inner margin of a carbonate platform.     

Detection Methanogens in Newly Settled Sediments from Xuanwu Lake in Nanjing, China

Sediments from Xuanwu Lake have been dredged in the past 3 years to improve the water quality, but methanogenesis should still exist in the newly settled sediment. Methane production, methanogens, and physiochemical parameters were detected in the surface sediments (0–5 cm) and/or vertical sediments (0–21 cm, segmented at interval of 3 cm). Methane flux at water–air interface varied among five detected sites. Principal component analysis showed that CH₄ flux, content of water and the concentration of total nitrogen (TN), CH₄ and organic matters (OM) weighed most heavily on the component I in surface sediments while different patterns were observed for vertical sediments. The copy number of the 16S rRNA gene for bacteria was lower in the surface sediment (0–6 cm) than that in deeper sediments (12–21 cm), while 16S rRNA genes of Archaea were almost evenly distributed in the vertical sediments. Representatives belonging to the orders Methanobacteriales, Methanomicrobiales, and Methanosarcinales were detected in all samples of the vertical sediments, except that no members of the Methanococcales were detected in the samples at 0–6 cm. The level of Methanobacteriales reached a highest density at 18.1 × 10⁴ copies g⁻¹ dry weight (dw) at 6–9 cm; for Methanosarcinales (76.89 × 10⁶ copies g⁻¹ dw) and Methanococcales (82.70 × 10³ copies g⁻¹ dw) at 12–15 cm, whereas for Methanomicrobiales (43.37 × 10⁶ copies g⁻¹ dw) at 9–12 cm. Methanosarcinaceae and Methanosaetaceae reached to their highest densities at 6–9 and 9–12 cm, respectively. These data provided useful information for better understanding the methanogenesis in the newly settled sediments of a recently dredged lake.     

Patch reef development in the florigemma-Bank Member (Oxfordian) from the Deister Mts (NW Germany): a type example for Late Jurassic coral thrombolite thickets

Small reefal bioconstructions that developed in lagoonal settings are widespread in a few horizons of the Late Jurassic (Oxfordian) succession of the Korallenoolith Formation, exposed southwest of Hannover, Northwest Germany. Especially the florigemma-Bank Member, “sandwiched” between oolite shoal deposits, exposes a high variety of build-ups, ranging from coral thrombolite patch reefs, to biostromes and to coral meadows. The reefs show a distribution with gradual facies variations along an outcrop belt that extends about 30 km from the Wesergebirge in the NW to the Osterwald Mts in the SE.The patch reefs from the Deister Mts locality at the “Speckhals” are developed as coral-chaetetid-solenoporid-microbialite reefs and represent a reef type that was hitherto unknown so far north of its Tethyan counterparts. They are mainly built up by coral thickets that are preserved in situ up to 1.5 m in height and a few metres in diameter. They contain up to 20 coral species of different morphotypes but are chiefly composed of phaceloid Stylosmilia corallina and Goniocora socialis subordinately. The tightly branched Stylosmilia colonies are stabilized by their anastomosing growth. The coral branches are coated with microbial crusts and micro-encrusters reinforcing the coral framework. Encrusters and other biota within the thicket show a typical community replacement sequence: Lithocodium aggregatum, Koskinobullina socialis and Iberopora bodeuri are pioneer organisms, whereas the occurrence of non-rigid sponges represents the terminal growth stage. The latter are preserved in situ and seem to be characteristic so far poorly known constituents of the Late Jurassic cryptobiont reef dweller community. The distance and overall arrangement of branches seems to be the crucial factor for the manifestation of a (cryptic) habitat promoting such community replacement sequences. Widely spaced branches often lack any encrusting and/or other reef dwelling organisms, whereas tightly branched corals, as is St. corallina, stimulate such biota. Hence, such reefs are well suited for research on coelobites and community sequences of encrusting and cavity dwelling organisms.     

Reef habitats and associated sessile-benthic and fish assemblages across a euphotic–mesophotic depth gradient in Isla Desecheo, Puerto Rico

Quantitative surveys of sessile benthos and fish populations associated with reef habitats across a 15–50 m depth gradient were performed by direct diver observations using rebreathers at Isla Desecheo, Puerto Rico. Statistically significant differences between depths were found for total live coral, total coral species, total benthic algae, total sponges and abiotic cover. Live coral cover was higher at the mid-shelf (20 m) and shelf-edge (25 m) stations, whereas benthic algae and sponges were the dominant sessile-benthic assemblage at mesophotic stations below 25 m. Marked shifts in the community structure of corals and benthic algae were observed across the depth gradient. A total of 119 diurnal, non-cryptic fish species were observed across the depth gradient, including 80 species distributed among 7,841 individuals counted within belt-transects. Fish species richness was positively correlated with live coral cover. However, the relationship between total fish abundance and live coral was weak. Abundance of several numerically dominant fish species varied independently from live coral cover and appeared to be more influenced by depth and/or habitat type. Statistically significant differences in the rank order of abundance of fish species at euphotic vs mesophotic stations were detected. A small assemblage of reef fishes that included the cherubfish, Centropyge argi, sunshine chromis, Chromis insolata, greenblotch parrotfish, Sparisoma atomarium, yellowcheek wrasse, Halichoeres cyanocephalus, sargassum triggerfish, Xanthichthys ringens, and the longsnout butterflyfish, Chaetodon aculeatus was most abundant or only present from stations deeper than 30 m, and thus appear to be indicator species of mesophotic habitats.     

Topography, substratum and benthic macrofaunal relationships on a tropical mesophotic shelf margin, central Great Barrier Reef, Australia

Habitats and ecological communities occurring in the mesophotic region of the central Great Barrier Reef (GBR), Australia, were investigated using autonomous underwater vehicle (AUV) from 51 to 145 m. High-resolution multibeam bathymetry of the outer-shelf at Hydrographers Passage in the central GBR revealed submerged linear reefs with tops at 50, 55, 80, 90, 100 and 130 m separated by flat, sandy inter-reefal areas punctuated by limestone pinnacles. Cluster analysis of AUV images yielded five distinct site groups based on their benthic macrofauna, with rugosity and the presence of limestone reef identified as the most significant abiotic factors explaining the distribution of macrofaunal communities. Reef-associated macrofaunal communities occurred in three distinct depth zones: (1) a shallow (<60 m) community dominated by photosynthetic taxa, notably scleractinian corals, zooxanthellate octocorals and photosynthetic sponges; (2) a transitional community (60–75 m) comprising both zooxanthellate taxa and azooxanthellate taxa (notably gorgonians and antipatharians); and (3) an entirely azooxanthellate community (>75 m). The effects of depth and microhabitat topography on irradiance most likely play a critical role in controlling vertical zonation on reef substrates. The lower depth limits of zooxanthellate corals are significantly shallower than that observed in many other mesophotic coral ecosystems. This may be a result of resuspension of sediments from the sand sheets by strong currents and/or a consequence of cold water upwelling.     

Do fluctuating temperature environments elevate coral thermal tolerance?

In reef corals, much research has focused on the capacity of corals to acclimatize and/or adapt to different thermal environments, but the majority of work has focused on distinctions in mean temperature. Across small spatial scales, distinctions in daily temperature variation are common, but the role of such environmental variation in setting coral thermal tolerances has received little attention. Here, we take advantage of back-reef pools in American Samoa that differ in thermal variation to investigate the effects of thermally fluctuating environments on coral thermal tolerance. We experimentally heat-stressed Acropora hyacinthus from a thermally moderate lagoon pool (temp range 26.5–33.3°C) and from a more thermally variable pool that naturally experiences 2–3 h high temperature events during summer low tides (temp range 25.0–35°C). We compared mortality and photosystem II photochemical efficiency of colony fragments exposed to ambient temperatures (median: 28.0°C) or elevated temperatures (median: 31.5°C). In the heated treatment, moderate pool corals showed nearly 50% mortality whether they hosted heat-sensitive (49.2 ± 6.5% SE; C2) or heat-resistant (47.0 ± 11.2% SE; D) symbionts. However, variable pool corals, all of which hosted heat-resistant symbionts, survived well, showing low mortalities (16.6 ± 8.8% SE) statistically indistinguishable from controls held at ambient temperatures (5.1–8.3 ± 3.3–8.3% SE). Similarly, moderate pool corals hosting heat-sensitive algae showed rapid rates of decline in algal photosystem II photochemical efficiency in the elevated temperature treatment (slope = −0.04 day⁻¹ ± 0.007 SE); moderate pool corals hosting heat-resistant algae showed intermediate levels of decline (slope = −0.039 day⁻¹ ± 0.007 SE); and variable pool corals hosting heat-resistant algae showed the least decline (slope = −0.028 day⁻¹ ± 0.004 SE). High gene flow among pools suggests that these differences probably reflect coral acclimatization not local genetic adaptation. Our results suggest that previous exposure to an environmentally variable microhabitat adds substantially to coral–algal thermal tolerance, beyond that provided by heat-resistant symbionts alone.     

The contribution of epipelon to total sediment microalgae in a shallow temperate eutrophic loch (Loch Leven, Scotland)

Benthic microalgae are known to perform important ecosystem functions in shallow lakes. As such it is important to understand the environmental variables responsible for regulating community structure, positioning and biomass. We tested the hypothesis that the positioning (across a depth gradient of 2–22 m overlying water depth) and relative biomass (determined using bulk and lens tissue harvested chlorophyll (Chl) a concentrations) of the epipelon community would vary independently with season (12 monthly samples) and across natural gradients of light and habitat disturbance relative to the total benthic algal community (i.e. all viable microalgae in the surface sediments) in a shallow eutrophic loch. Total sediment microalgal Chl a concentrations (TS-Chl; range: 5–874 μg Chl a g⁻¹ dw) were highest in winter and in the deepest site (20 m overlying water depth), apparently as a result of phytoplanktonic settling and sediment focussing processes. Epipelic Chl a concentrations (Epi-Chl; range: <0.10–6.0 μg Chl a g⁻¹ dw) were highest in winter/spring, a period when water clarity was highest and TS-Chl lowest. Principal components analysis highlighted strong associations between Epi-Chl and sites of intermediate depths (2.5–5.5 m) in all seasons except autumn/winter. Autumn/winter represented the season with the highest average wind speeds preceding sampling, during which the highest Epi-Chl concentrations were associated with the deepest sites. Epi-Chl was associated with intermediate light and habitat disturbance during spring/summer and summer/autumn and varied positively with habitat disturbance, only, in autumn/winter and winter/spring. The epipelon community structure also varied with depth; diatoms dominated shallow water sediments, cyanobacteria dominated deep water sediments, and sediments at sites of intermediate depth returned the highest biovolume estimates and the most diverse communities. This study has strengthened the hypothesis that the structure and biomass of benthic microalgal communities in lakes are regulated by habitat disturbance and water clarity, both of which are expected to respond to climate change and eutrophication. The degree to which these structural responses reflect functional performance requires clarification.     

Trace metal concentrations in the tropical sponge Spheciospongia vagabunda at a sewage outfall: synchrotron X-ray imaging reveals the micron-scale distribution of accumulated metals

Major and trace elements were measured in sponges, seawater and sediment in Darwin Harbour (Australia) to test the hypothesis that metals are elevated in sponges closer to a sewage outfall compared with unimpacted sites. Seawater and sediment at the sewage discharge site contained high, but localised, concentrations of phosphorus (P), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As) and lead (Pb) compared with background sites. Metal concentrations in the sponge Spheciospongia vagabunda were highly elevated compared with other sponges and, although site specific, high metal concentrations were unrelated to the presence of sewage effluent. X-ray fluorescence microprobe imaging was used to investigate the metal distribution pattern in S. vagabunda. High Fe, Ni and Zn concentrations were either localised in circular patches (100–200 μm size) near water canals or in the pinacoderm, or scattered in spots (approximately 10 μm) throughout the tissue. This supports a microflora-mediated metal bioaccumulation hypothesis. In contrast, Co and Mn were highly dispersed and probably associated with aluminium- and iron-oxide rich sediment inclusions. Although the lack of association between sewage effluent and metal accumulation precludes the use of S. vagabunda as a biomonitor, the apparent differential mechanisms of metal accumulation warrants further investigation.     

Paleoecology of Pennsylvanian phylloid algal buildups in south Guizhou,China

Pennsylvanian phylloid algal reefs are widespread and well exposed in south Guizhou, China. Here we report on reefs ranging from 2 to 8 m thickness and 30–50 m lateral extension. Algae, the main components, display a wide spectrum of growth forms, but are commonly cyathiform (cup-shaped) and leaf-like (undulate plates). The algal reef facies is dominated by boundstone. Algal thalli form a dense carpet whose framework pores are filled with marine cement and peloidal micrite. The peloidal matrix is dense, partly laminated or clotted with irregular surfaces and often gravity defying. Algal reefs in Guizhou differ from examples reported to date by the high biodiversity of organisms other than phylloids: e.g., the intergrowth of algae with corals (some of which are twice the size of algal thalli) and numerous large brachiopods. This contrasts to previous views that phylloid algal “meadows” dominated the actual seafloor, excluding other biota. Also, the pervasive marine cements (up to 50%) including botryoidal cement are noteworthy. Algal reefs developed at platform margins, a depositional environment similar to that of modern Halimeda mounds in Java, Australia and off Bahamas, and to that of time-equivalent examples reported from the Canadian Arctic Archipelago. Whereas nutrients appear decisive in the growth of Halimeda reefs, algal reefs reported herein seemingly grew under conditions of low nutrient levels. Overall, algal reefs in Guizhou challenge previous views on growth forms, diversity patterns, and depositional environments and add to the spectrum of these partly puzzling biogenic structures.     

Modern cryptic microbialite/metazoan facies from Lizard Island (Great Barrier Reef,Australia) formation and concepts

Summary From shallow water caves of fringing reefs related to continental islands of the Lizard Island Section thrombolitic micritic microbialites were observed. The microbialites exhibit always a light decreasing facies succession. The succession starts with a coralgal community and ends with light independent microbial biofilms and benthos (coralline sponges). The sessile mineralized benthos community is constructed of crustose foraminifera, serpulids, thecidean brachiopods, bryozoans, and coralline sponges. The observed benthic community is very similar to those one observed in cryptic habitates of Aptian and Albian reefs of northern Spain. For longtime studies of the microbialite formation and growth rates of coralline sponges the specimens were stained in vivo, within their natural habitat with histochemical fluorochromes and nonfluorescent agents. Main results are a very slow growth of the microbialite and associated sponges (50–100 μm/y). Only few calcifying microbes are participators during microbialite formation. Calcifying acidic organic macromolecules are mainly responsible for microbialite formation by cementing detritical material. Fe/Mn-bacterial biofilms are responsible for strong corrosion of the microbialite. Beside the corrosive activity of the Fe/Mn-bacterial biofilms boring sponges (Aka, Cliona) are the main destructors. Geochemically the observed microbialites are composed of mainly high-Mg calcites and exhibit high positive δ¹³C (+3 to +4) values.     

The Cenomanian of northern Germany: facies analysis of a transgressive biosedimentary system

A facies analysis of the epicontinental marine Cenomanian sediments of northern Germany shows the presence of 17 facies types (FTs, including several subtypes) which can be assigned to three facies associations: 1) an inner shelf facies association (FT 1–8) with high amounts of terrigenous material and/or high-energy depositional features, 2) a middle shelf facies association (FT 9–15) of predominantly calcareous sediments with moderate amounts of generally fine siliciclastics, and 3) an outer shelf facies association (FT 16–17) of low-energy, fine-grained, pure limestones. These three facies associations roughly correspond to the well-known lithological units of the Cenomanian of northern Germany, i.e., the Essen Greensand/Cenomanian Marls complex, the Pläner Limestones, and the Poor rhotomagense Limestones. The sediments were deposited on a northward-dipping homoclinal ramp with more-or-less shoreline-parallel facies belts. The sediment composition on this ramp-like shelf was a function of the varying importance of three different sediment sources: 1) terrigenous input from the south (Rhenobohemia), generally fining/decreasing in a proximal–distal (i.e., S–N) direction; 2) production of skeletal grains, mainly by macrobenthic organisms; and 3) settling of planktic carbonate (mainly calcispheres and calcareous nannofossils). In response to decreasing water energy with increasing water depth, the seaward decreasing terrigenous influence, and increasing planktic carbonate production, increasingly finer and more calcareous sediments were deposited in a proximal–distal transect. This rather straightforward picture was slightly modified by highest carbonate accumulation rates (planktic and benthic) on the middle shelf, forming a mid-shelf depocenter (fossiliferous, calcisphere-rich Pläner Limestones). Time-transgressive, southward-directed onlap of this biosedimentary system during the Cenomanian caused a significant retreat of the coastline towards the south and a retrogradational stacking of facies belts, explaining the broadly similar facies development and lithology of Cenomanian successions across northern Germany. The boundaries of the lithological units, however, tend to be considerably diachronous in a distal–proximal transect. In the late Middle and early Late Cenomanian, a final drowning and facies levelling (“oceanization”) is indicated by the widespread deposition of uniform calcareous nannofossil mudstones (Poor rhotomagense Limestones).     

Upper Triassic reef facies in the Asher-Atlit-1 borehole, Northern Israel: Microfacies, cement stratigraphy and paleogeographic implications

Summary  The late Triassic succession of the Asher-Atlit 1 borehole is over 1000 m thick, and is composed of reefal and associated facies interbedded with volcanics of Norian age. Only borehole cuttings are available. Microfacies classification and cement stratigraphy determined by optical and CL microscopy, allowed discrimination of six episodes of reef establishment, progradation, shallowing, and termination. Organic buildups are constructed of reef-building biota (sponges, possible corals, encrusting organisms) typical for the late Triassic of the Tethys. Reef-associated facies include fore-slope, central reef, ooid shoal, lagoonal, and supratidal environments. Cement zoning patterns trace diagenetic signatures which range from early neomorphic skeletal replacements and original marine cements, via characteristic burial sequences; depositional and diagenetic sequences are terminated by marginal marine intra- or supratidal conditions, and subaerial exposure with pedogenic overprints. Volcanic episodes tend to be associated with termination of carbonate sedimentation episodes, while volcanic quiescence and subsidence permit vertical progradation of reefal and associated facies. The depositional and progradational environment, rapid rate of sedimentation, periodicity, association with volcanics, and regional considerations, suggest a depositional setting on the rifted shelf-margin of the nascent Neo-Tethys, with a possible eustatic overprint.     

Visibly healthy corals exhibit variable pigment concentrations and symbiont phenotypes

Understanding the natural variability of photosynthetic pigment ranges and distributions in healthy corals is central to evaluating how useful these measurements are for assessing the health and bleaching status of endosymbiotic reef-building corals. This study examined the photosynthetic pigment variability in visibly healthy Porites lobata and Porites lutea corals from Kaneohe Bay, Hawaii and explored whether pigment variability was related to the genetic identity or phenotypic characteristics of the symbionts. Concentrations of the photosynthetic pigments chlorophyll a, peridinin, chlorophyll c ₂ , diadinoxanthin, diatoxanthin, β,β-carotene and dinoxanthin were quantified using high-performance liquid chromatography (HPLC). Pigment concentrations were found to range 1.5–10 fold in colonies of each species at similar depths (0–2, 2–4, 10–15 and 19–21 m). Despite the high pigment variability, pigment ratios for each species were relatively conserved over the 0–21 m depth gradient. The genetic identity of the symbiont communities was examined for each colony using 18S nuclear ribosomal DNA (nrDNA) restriction fragment length polymorphisms. All colonies contained symbionts belonging to clade C. The density and phenotypic characteristics of the symbionts were explored using flow cytometry, and fluorescence and side scatter (cell size) properties revealed phenotypically distinct symbiont subpopulations in every colony. The symbiont subpopulations displayed pigment trends that may be driven by acclimatization to irradiance microenvironments within the host. These results highlight the biological complexity of healthy coral–symbiont associations and the need for future research on pigments and symbiont subpopulation dynamics.     

Biotic structure and morphology of patch reefs from South China (Ningqiang Formation, Telychian, Llandovery, Silurian)

Summary Ningqiang Formation (late Telychian, Llandovery, Silurian), characterized by nearly 3000 m of shales in tercalated with carbonates, is situated between Ningqiang (S. Shaanxi Province) to Guangyuan (N. Sichuan Province) adjacent to the northwest margin of the Yangtze Platform. The high diversity “Xiushan Fauna”, and abundant reef development, illustrate a relatively warm and persistent shallo marine environment in these early Silurian sediments. The sequence shows reef radiation after recovery from the end Ordovician mass extinction envents. Multiple horizons of reef-building occurred within a relatively short geological interval and resulted in more than 30patch reefs up to 200 m in diameter and 1–50 m vertically, composed of abundant fossils. Reef biota include frame-building corals, stromatoporoids, bryozoans, and microbialites, and reef-associated oranisms such as crinoids, brachiopods, trilobites, gastropods, nautiloids and ostracods. Three reefrelated biotic associations are recognised: a) reefs dominated by framework with crinoids and microbia; b) reefs dominated by only crinoids and microbia; and c) crinoiddomainated facies. Seven representative reef examples illustrate different morphologies and growth styles. A high terrigenous debris input and shallow epicontinental ramp, which lacked obvious topographic variation, were major controls which resulted in rather simple reefs; sedimentation was apparently the main constraint on lateral and vertical extension of reefs, and prevented large-scale reef complexes developing.     

Reconstructing the history of an invasion: the toxic phytoplankton species <Emphasis Type="Italic">Gymnodinium catenatum</Emphasis> in the Northeast Atlantic

The phytoplankton species Gymnodinium catenatum is responsible for major worldwide losses in aquaculture due to shellfish toxicity. On the West coast of the Iberian Peninsula, toxic blooms have been reported since the mid-1970s. While the recent geographical spread of this species into Australasia has been attributed to human-mediated introduction, its origin in the Northeast Atlantic is still under debate. Gymnodinium catenatum forms a highly resistant resting stage (cyst) that can be preserved in coastal sediments, building-up an historical record of the species. Similar cyst types (termed microreticulate) are produced by other non-toxic Gymnodinium species that often co-occur with G. catenatum. We analysed the cyst record of microreticulate species in dated sediment cores from the West Iberian shelf covering the past ca. 150 years. Three distinct morphotypes were identified on the basis of cyst diameter and paracingulum reticulation. These were attributed to G. catenatum (35.6–53.3 μm), G. nolleri (23.1–36.4 μm), and G. microreticulatum (20.5–34.3 μm). Our results indicate that G. catenatum is new to the NE Atlantic, where it appeared by 1,889 ± 10, expanding northwards along the West Iberian coast. The earliest record is from the southernmost sample, while in the central Portuguese shelf the species appears in sediments dated to 1,933 ± 3, and in the North, off Oporto, in 1,951 ± 4. On the basis of the cyst record and toxic bloom reports, we reconstruct the invasive pathway of G. catenatum in the NE Atlantic. Although human-mediated introduction cannot be discarded, the available evidence points towards natural range expansion, possibly from NW Africa.