Algal Reefs Research Articles

Historical Connectivity and Demography of the Ferocious Reef Crab, Eriphia ferox (Crustacea; Eriphiidae), Demonstrate That Taoyuan Algal Reef Is an Essential Population Source Along the East Taiwan Strait

The east Taiwan Strait is largely fringed by sandy and muddy habitats. However, a massive algal reef made of crustose coralline algae has been found along the coast off Taoyuan city in northwestern Taiwan. The porous structure of Taoyuan Algal Reef harbors high abundance and diversity in marine organisms, including the ferocious reef crab, Eriphia ferox. Such a pivotal geographic location and unique ecological features make Taoyuan Algal Reef a potential stepping stone connecting biotic reefs in the east Taiwan Strait, South China Sea to the south, and even the high latitude of Japan to the north. In this study, we examined the population connectivity and historical demography of E. ferox by analyzing mitochondrial cytochrome oxidase I (COI) fragments of 317 individuals sampled from 21 localities in the northwestern Pacific. Our analyses of haplotype network and pairwise FST comparisons revealed a lack of phylogeographical structure among E. ferox populations, implying the existence of a migration corridor connecting the South and East China Seas through the east Taiwan Strait. Multiple lines of evidence, including significant values in neutrality tests, unimodally shaped mismatch distributions, and Bayesian skyline plots elucidated the rapid population growth of E. ferox following the sea-level rise after Last Glacial Maximum (ca. 2–10 Ka). Such demographic expansion in E. ferox coincided with the time when Taoyuan Algal Reef started to build up around 7,500 years ago. Coalescent migration analyses further indicated that the large and continuous E. ferox population exclusively found in Datan Algal Reef, the heart of Taoyuan Algal Reef, was a source population exporting migrants both northward and southward to the adjacent populations. The bidirectional gene flow should be attributed to larval dispersal by ocean currents and secondary contact due to historical population expansion. Instead of serving as a stepping stone, our results support that Taoyuan Algal Reef is an essential population source for biotic reef-associated species along the east Taiwan Strait, and highlight the importance of conserving such a unique ecosystem currently threatened by anthropogenic development.

Implementation of a Petrographical and Petrophysical Workflow Protocol for Studying the Impact of Heterogeneity on the Rock Typing and Reservoir Quality of Reefal Limestone: A Case Study on the Nullipore Carbonates in the Gulf of Suez

AbstractThis study focuses on the heterogeneity of the middle Miocene syn‐rift Belayim nullipore (reefal) marine sequences in the Gulf of Suez and its impacts on reservoir quality. The sequences consist of coralline algal reef limestones with a highly complex dual‐porosity system of primary and secondary porosities of widely varying percentages. To achieve a precise mathematical modeling of these reservoir sequences, a workflow protocol was applied to separate these sequences into a number of hydraulic flow units (HFUs) and reservoir rock types (RRTs). This has been achieved by conducting a conventional core analysis on the nullipore marine sequence. To illustrate the heterogeneity of the nullipore reservoir, the Dykstra‐Parsons coefficient (V) has been estimated (V = 0.91), indicating an extremely heterogeneous reservoir. A slight to high anisotropy (λk) has been assigned for the studied nullipore sequences. A stratigraphic modified Lorenz plot (SMLP) was applied to define the optimum number of HFUs and barriers/baffles in each of the studied wells. Integrating the permeability‐porosity, reservoir quality index‐normalized porosity index (RQI‐NPI) and the RQI‐flow zone indicator (RQI‐FZI) plots, the discrete rock types (DRT) and the R35 techniques enable the discrimination of the reservoir sequences into 4 RRTs/HFUs. The RRT4 packstone samples are characterized by the best reservoir properties (moderate permeability anisotropy, with a good‐to‐fair reservoir quality index), whereas the RRT1 mudstone samples have the lowest flow and storage capacities, as well as the tightest reservoir quality.

Bryozoan‐rich stromatolites (bryostromatolites) from the Silurian of Gotland and their relation to climate‐related perturbations of the global carbon cycle

ABSTRACTBryozoan–stromatolite associations (bryostromatolites) formed conspicuous reef structures throughout the Sheinwoodian (Wenlock) to Ludfordian (Ludlow) stratigraphy on Gotland but have not been described so far. They are mainly composed of encrusting bryozoans forming a complex intergrowth with porostromate and spongiostromate microbes and are different from the abundant stromatoporoid–coral–algal reefs with respect to their composition. In the bryostromatolite different growth stages can be identified. The observed succession can be taken as evidence for cyclic environmental changes during reef formation. Stenohaline reef‐dwelling organisms, such as echinoderms, sponges, corals and trilobites, indicate fully marine salinities. Ten localities exposing bryostromatolites were discovered. Individual bryostromatolites are small with few decimetres up to one metre in size, and occur solely in shallow marine areas. Common features of these reefs on Gotland are cauliflower‐like growth, a high bryozoan diversity, a high abundance of phosphatic fossils and components such as bryozoan pearls and inarticulate phosphatic brachiopods, enhanced bioerosion, Palaeomicrocodium crusts, vadose silt and gypsum pseudomorphs. The high abundance of Palaeomicrocodium, as well as the alternation with other crust‐forming contributors, suggest that it could have been formed directly at the palaeo‐sea surface, probably in times of minor but high‐frequency sea‐level fluctuations. Vadose silt and pseudomorphs after gypsum in reef cavities indicate subaerial exposure shortly after reef growth. The high amount of phosphatic components indicates a high nutrient input, probably by dust. All bryostromatolites were formed in times of strongly elevated δ13C values. The unusual combination of sedimentological and palaeoecological features, as well as their occurrence exclusively during strong positive δ13C excursions, are evidence that the bryostromatolite development responded to climatic/oceanographic changes, which may have played an important role in reef control.

An intertidal life: Combined effects of acidification and winter heatwaves on a coralline alga (Ellisolandia elongata) and its associated invertebrate community

In coastal marine ecosystems coralline algae often create biogenic reefs. These calcareous algal reefs affect their associated invertebrate communities via diurnal oscillations in photosynthesis, respiration and calcification processes. Little is known about how these biogenic reefs function and how they will be affected by climate change. We investigated the winter response of a Mediterranean intertidal biogenic reef, Ellissolandia elongata exposed in the laboratory to reduced pH conditions (i.e. ambient pH – 0.3, RCP 8.5) together with an extreme heatwave event (+1.4 °C for 15 days). Response variables considered both the algal physiology (calcification and photosynthetic rates) and community structure of the associated invertebrates (at taxonomic and functional level). The combination of a reduced pH with a heatwave event caused Ellisolandia elongata to significantly increase photosynthetic activity. The high variability of calcification that occurred during simulated night time conditions, indicates that there is not a simple, linear relationship between these two and may indicate that it will be resilient to future conditions of climate change.In contrast, the associated fauna were particularly negatively affected by the heatwave event, which impoverished the communities as opportunistic taxa became dominant. Local increases in oxygen and pH driven by the algae can buffer the microhabitat in the algal fronds, thus favouring the survival of small invertebrates.

To the light side: molecular diversity and morphology of stomatopod larvae and juveniles (Crustacea: Malacostraca: Stomatopoda) from crustose coralline algal reefs in Taiwan

Biology of planktonic stomatopod larvae has long remained poorly understood and often considered “black boxes” in life history studies. From coralline crustose algal (CCA) reefs at Datan, Taoyuan, Taiwan, using light traps recently designed, we collected considerable number of stomatopod larvae and juveniles. Applying DNA barcoding techniques using mitochondrial cytochrome oxidase I (COI) and 16S ribosomal RNA (16S rRNA) gene sequences, 14 morphotypes were revealed to represent 12 distinct species, seven of which identified to species level by comparing against reference sequences available from online source (GenBank), whereas the other five do not cluster with any known sequences. All stomatopod larvae and juveniles were described and illustrated. We report Manningia pilaensis (De Man, 1888) and Levisquilla jurichi (Makarov, 1979) as new records of the stomatopod fauna of Taiwan and confirm the validity of Lysiosquillina maculata (Fabricius, 1793). Based on material we acquired from light traps, which include propelagic antizoea larvae (of L. maculata), and also postlarval and juvenile forms (of various squillid species), both positively phototactic, indicating the current understanding of negative-positive-negative phototactic tendency from early planktonic to postlarval stages through the development of stomatopod larvae, might not be as distinct as previously described.

Distinguishing regeneration from degradation in coral ecosystems: the role of value

In this paper I argue that the value attributed to coral reefs drives the characterisation of evidence for their regeneration or degradation. I observe that regeneration and degradation depend on an understanding of what an ecosystem looks like when undegraded (a baseline), and that many mutually exclusive baselines can be given for any single case. Consequently, facts about ecological processes are insufficient to usefully and non-arbitrarily characterise changes to ecosystems. By examining how baselines and the value of reefs interact in coral and algal reef examples, I argue that considering the value of an ecosystem is a necessity when describing processes like regeneration and degradation. This connects value as studied in socio-ecological and economic research with values as discussed in the philosophy of science literature. It also explains why such a broad range of processes may be considered regenerative, including those which introduce significant novelty, as well as pointing towards ways to mediate related debates, such as those surrounding novel and ‘pristine’ ecosystems.

Brackish water algal reefs – facies analysis as a tool to identify palaeoenvironmental variations in Miocene deposits (Mainz‐Weisenau, Germany)

Brackish‐water carbonates are far less studied than their marine or limnic counterparts. However, their association with few, specialized species enables the documentation of fine‐scale changes in the depositional environment. The Cenozoic Mainz Basin (Germany) was only sporadically connected to the North Sea and the Paratethys, exposing several transitions from marine to fresh water influence. Focusing on one outcrop of the Rüssingen Formation of Mainz‐Weisenau (Aquitanian, Miocene), we present a detailed analysis of the faunal and sedimentological responses to changing salinities and water depth, including algal reef growth and facies development. The deposits include allochthonous limestones surrounding an autochthonous reef complex and several smaller reef patches. The allochthonous facies is dominated by the gastropod Hydrobia inflata, and the reef facies is mainly made up by the green alga Cladophorites sp. The algal thalli are overgrown by cryptocrystalline, organic precipitations, and laminated, chemical precipitations. Locally, quiver‐shaped structures of Trichoptera sp. protective cases occur. The depositional setting was a shallow, low energy, and brackish environment supersaturated by carbonate. We could not confirm a general trend of reducing salinities as reported for the Rüssingen Formation. Our results question previously reported episodic desiccation events, because apparent caliche horizons actually represent thin beds of increased Cladophorites growth. Set‐up, distribution of the reef facies, and reef debris indicate short‐time variations of temperature, salinity and water depth. We conclude that these variations are based on the geographic position at the edge of an algal reef barrier, separating the Mainz Basin from the Rhine Rift Valley.

Multiple Environmental Factors Increase the Niche Complexity and Species Diversity of Brachyuran Crabs in an Intertidal Algal Reef Ecosystem in Northwestern Taiwan.

Algal reefs are one of the world's rare and poorly understood ecosystems. They are mainly distributed in the Mediterranean Sea, but one notable exception-an intertidal algal reef ecosystem in northwestern Taiwan-stretches for 27 km along the coast of Taoyuan, making it probably the largest algal reef coast found in shallow water. Despite the reef's rarity and striking characteristics, the coastal land that it is part of has undergone a series of developments and is now surrounded by industrial parks. Brachyuran crabs are one of the most abundant and visible groups of organisms in the intertidal zone. In the present study, we investigated the brachyuran crab community in this reef to provide a more detailed record of brachyuran crab species compositions in this intertidal algal reef ecosystem and illustrate the characteristics of this understudied ecosystem by comparing its species diversity and abundance with three natural variables- sampling time, tidal level, and season-in a wildlife refuge and north of the refuge. Two methods were used in the study: a qualitative method (to determine the species richness) and a quantitative method (to estimate the population density). We identified a total of 52 brachyuran species from 13 families in the habitats. The highest species richness was found in Datan G2, north of the wildlife refuge. The crab species composition in this algal reef is different from its compositions in coral and rocky reefs. Our analysis indicated that the species abundance is affected by multiple factors, and a single investigation is not enough to reflect the true population density of brachyuran crabs on this reef. In addition, we found that the sites outside the wildlife refuge were in much better condition than those in the wildlife refuge, and should therefore be included in the wildlife refuge. In particular, Datan, located north of the wildlife refuge, had the highest species richness, and the area's species composition was different from that of the nearby wildlife refuge. Thus, we strongly recommend that a) the Datan area be protected to maintain this high crab diversity and b) further research be performed to better understand brachyuran crab biology in the intertidal algal reef ecosystem.

A UAV-RTK-LIDAR SYSTEM MEASUREMENTS OF WAVE ENERGY DISSIPATION OVER A SANDY BEACH AND AN ALGAL-REEF AREA

Wave energy dissipation is a significant factor affecting coastal hydrodynamics, coastline morphology, wave height transformation, and the nutrient uptake in the coral reef (Huang, Lenain et al. 2012). However, it is difficult to be measured since accurate and spatial-distributed measurements of sea surface elevations are required to compute this quantity. We used a UAV-RTK-Lidar system to test the possibility for the measurements of wave energy dissipation. The UAV system was validated to able to measure the ocean wave properties (Huang, Yeh et al. 2018). Two field experiments of measuring energy dissipation were conducted over an algal-reef and a sandy beach site, respectively. Nine and eight flights of UAV measurements on the algal reef and sandy beach were conducted for one tidal cycle. The measurements of wave properties by UAV were compared with those of in-situ instruments using pressure sensors.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/fBLbsBuK4AA

Preliminary study on the boundary layer of an artificial reef with regular grooves surface structure

Seaweeds spores need to pass through the boundary layer on the surface of artificial algal reef before they can contact with the attaching substrate and start the process of attachment, germination and growth. However, the performance of the boundary layer is affected by the roughness of reef surface, but the mechanism is not clear. In this article, the cable tie was selected as the attaching substrate of seaweed spores to facilitate the analysis of the relationship between the reef surface structure and its boundary layer. The comparison results of flume experiment and numerical simulation in different magnification dimensions verified that the numerical simulation method can be directly applied to analyze the boundary layer on the reef surface. The numerical results showed that the roughness of reef surface had a significant effect on velocity profiles, boundary layer thickness, turbulence intensity and bottom shear stress. The flow in the boundary layer on the reef surface is a highly-turbulent case, and the flow in the grooves belongs to a medium-turbulent case. This may be one of the reasons that affect whether algal spores can finally attach to the reef surface after passing through the boundary layer. This work supplies a scientific evidence for research of the boundary layer on the reef surface.

Coastal development threatens Datan area supporting greatest fish diversity at Taoyuan Algal Reef, northwestern Taiwan

Abstract Taoyuan Algal Reef is a biodiverse coralline algal reef in north‐west Taiwan, that is currently threatened by coastal development and industrial waste runoff. As the reef lies in an exposed area that is frequently disturbed by monsoons, it is difficult to survey using traditional methods. Knowledge of the reef is therefore limited, and has until recently, long been regarded as a barren environment. However, recent studies have revealed that the reef is inhabited by a diverse array of organisms, particularly at Datan, where a natural gas receiving terminal is planned for construction. Due to challenging environmental conditions, otolith assemblage and soundscape analyses were used to supplement traditional sampling methods including clove oil, netting, and pole‐and‐line fishing in order to assess the diversity of the fish community at Taoyuan Algal Reef. Several fish species that had not been recorded by previous surveys were observed. Fish diversity and the average size of commercially targeted species were greatest at Datan G2. Predatory reef fishes such as groupers (Serranidae) and snappers (Lutjanidae), as well as several small endangered scalloped hammerhead sharks Sphyrna lewini were recorded at G2, where otolith assemblage analysis also indicated increased predatory activity. However, fewer individuals and species were recorded from tidal pools across all sites compared to previous surveys, suggesting a loss of biodiversity. If construction work resumes at Datan, it will be likely to have adverse consequences for the reef itself, the species that inhabit it, and by extension, the local fishermen that rely upon it. Halting additional coastal development, reducing industrial and domestic pollution, as well as improving the management of traditional fisheries is recommended to protect this unique reef ecosystem from further degradation.

The Application of Seabed Silt in the Preparation of Artificial Algal Reefs

Large amounts of silt have been deposited on the seabed in China’s coastal areas due to intensive coastal development and marine raft aquaculture, which are the main causes of local marine environmental disasters. In this study, seabed silt was tested as a potential raw material for artificial reefs. The silt was mixed with cement in four proportions to create concrete specimens for use in silt artificial reefs (SARs). The compressive strength development and nutrient dissolution were examined in the SAR specimens. The hydration products of the SAR paste were investigated through X-ray diffraction (XRD), scanning election microscope (SEM), and differential scanning calorimetry (DSC) techniques. The results showed that the compression strength of the SAR specimens was inversely proportional to their seabed silt content. The SAR specimens were able to continuously dissolve nitrogen-containing nutrients. The presence of Ca(OH)2, commonly found in traditional concrete, was not detected, which may help improve the seaweed adhesion and biological effects of artificial reefs. The effective utilization of seabed silt could serve to restore and improve the marine ecological environment.

Factors structuring the macrobenthos community in tidal algal reefs

Tidal algal reefs are considered high biodiversity habitats but have received little attention. Macrobenthos communities were characterized in a gradient of habitat types on the tidal flats in northwestern Taiwan, including algal reefs (R), mixed algal reefs and gravel (RG), mixed sand and gravel (SG) and sand (S). Both hydrodynamic movement and surface rugosity were highest in R, followed by RG, SG, and S. The faster the movement and the higher the rugosity were, the higher the density and taxon richness of the macrobenthos community. The relatively slower movement and accumulated sand in S likely resulted in stress on organisms, which led to a lower density and taxon richness of the macrobenthos community. Our results suggest that the main factors structuring the macrobenthos community in the diverse habitat types were hydrodynamic movement and surface rugosity.

Demographic census confirms a stable population of the critically-endangered caryophyllid coral Polycyathus chaishanensis (Scleractinia; Caryophyllidae) in the Datan Algal Reef, Taiwan

Polycyathus chaishanensis is a symbiotic caryophyllid coral described from a single population in a tidal pool off Chaishan, Kaohsiung, Taiwan. Due to its rarity, P. chaishanensis was declared a critically-endangered species under the Taiwan Wildlife Protection Act. In May 2017, a P. chaishanensis colony was discovered in the intertidal area of the Datan Algal Reef, Taoyuan, Taiwan. To determine whether this is a stable population in the algal reef, a demographic census—including data on occurrence, distribution, and colony size—was carried out in the algal reef in southern Taoyuan. Intertidal censuses and sediment collections were conducted at five different sections—Baiyu, Datan G1, Datan G2, Yongxing, and Yongan algal reefs—during the monthly spring low tide from July 2018 to January 2019. In total, 84 colonies—23 in Datan G1 and 61 in Datan G2—were recorded from a tidal range of − 160 to − 250 cm, according to the Taiwan Vertical Datum 2001 compiled by the Central Weather Bureau. No P. chaishanensis was found in Baiyu, Yongxing, or Yongan. The P. chaishanensis colony sizes ranged from 2.55 to 81.5 cm in diameter, with the larger P. chaishanensis present in the lower intertidal zone. Sediment was extremely high, with monthly site averages ranging from 3,818.26 to 29,166.88 mg cm−2 day−1, and there was a significant difference between sites and months, both of which affected the distribution of P. chaishanensis in the algal reef. Our study confirms the existence of a second population of P. chaishanensis in Taiwan, highlighting the importance of the Datan Algal Reef for the survival and protection of this critically-endangered caryophyllid coral and why it is so urgent that the reef should be conserved.

Pushing satellite imagery to new depths: Seascape feature mapping in a tropical shelf

Continental shelves are areas of extreme environmental and economic importance and priority areas for management and planning efforts. However, there is a knowledge gap regarding many tropical shelves, mainly due to high costs associated with surveying large marine areas with traditional techniques. Carbonatic, sediment-starved shelves are distributed across tropical and temperate regions and display characteristics that may allow the application of remote sensing methods, albeit the depth range found in these areas. Thus, this study tested the applicability of Landsat-8 imagery to detect bottom features in a sediment-starved shelf in North-eastern Brazil. The Brazilian Northeast Continental Shelf harbours a variety of geohabitats, including coral and algal reefs, beachrocks, mesophotic reefs, canyons, and paleochannels. Nine scenes were processed following the same steps: radiometric and atmospheric correction, masking, glint removal, water column correction and individual image adjustments. Two scenes were deemed best to portray targeted features. We detected 14 paleochannels in a 9700 km2 area, as well as the shelf break. A pixel-by-pixel analysis using all available bathymetric field data (n = 42,373 pixels) showed that 92.38% of the pixels were accurately classified. Misinterpreted pixels were either due to bordering regions incorrectly identified as paleochannels (3.99%) or paleochannels’ sections undetected in our final mosaic (3.62%). The final mosaic allowed a detailed view of submerged valleys (including previously unmapped channels) distributed up to areas deeper than 100 m using free of charge, medium-resolution satellite imagery. Some of these channels are known fishing grounds and fish spawning aggregation areas, making them priority zones for management and conservation efforts. To the best of our knowledge, this represents the first study applying Landsat imagery to map paleochannels in submerged areas, and most importantly, in areas deeper than 30 m. We believe this research can help focusing future mapping efforts and may advance the general knowledge of the area.

Assessing Fine-Scale Distribution and Volume of Mediterranean Algal Reefs through Terrain Analysis of Multibeam Bathymetric Data. A Case Study in the Southern Adriatic Continental Shelf

In the Mediterranean Sea, crustose coralline algae form endemic algal reefs known as Coralligenous (C) build-ups. The high degree of complexity that C can reach through time creates notable environmental heterogeneity making C a major hotspot of biodiversity for the Mediterranean basin. C build-up can variably modify the submarine environment by affecting the evolution of submerged landforms, although its role is still far from being systematically defined. Our work proposes a new, ad-hoc semi-automated, GIS-based methodology to map the distribution of C build-ups in shallow coastal waters using high-resolution bathymetric data, collected on a sector of the southern Apulian continental shelf (Southern Adriatic Sea, Italy). Our results quantitatively define the 3D distribution of C in terms of area and volume, estimating more than 103,000 build-ups, covering an area of roughly 305,200 m2, for a total volume of 315,700 m3. Our work firstly combines acoustic survey techniques and geomorphometric analysis to develop innovative approaches for eco-geomorphological studies. The obtained results can contribute to a better definition of the ocean carbon budget, and to the monitoring of local anthropogenic impacts (e.g., bottom trawling damage) and global changes, like ocean warming and acidification. These can affect the structural complexity and total volume of carbonate deposits characterizing the Mediterranean benthic environment.

Natural Gas or Algal Reef: Survey-Based Valuations of Pro-Gas and Pro-Reef Groups Specifically for Policy Advising

Much energy-related construction causes environmental concern. Sometimes the environmental issue is so huge that it is difficult to make a policy decision even with the assistance of traditional valuation techniques. The third natural gas receiving station at Datan, Taiwan, is one example of this. The construction would be beneficial to energy security, economic development, and particulate matter (PM) 2.5 reduction. However, it would destroy a precious algal reef, which is a habitat for endangered species, biodiversity, and a unique ecological system. Thus, we used willingness-to-pay to show the strength of both pro-energy and pro-ecology opinions specifically to help with decision-making. First, respondents were asked to choose between the gas station and the reef. Then they were asked about their willingness to pay for that choice. We then estimated parametric/nonparametric models—traditional probit, structured probit, and Turnbull—to obtain reliable estimates. We found that the per-person value for pro-gas-station respondents was higher than that for pro-reef respondents, while the percentage of pro-reef respondents was higher than the percentage of pro-gas-station respondents. These results together form a clear policy implication for this case.

Evolution of Pennsylvanian inner-platform phylloid algal reef mounds, Pha Nok Khao platform, northeastern Thailand

Phylloid algal reef mounds were commonly developed on Pennsylvanian—Permian carbonate platforms and today form globally distributed hydrocarbon reservoirs. The Pennsylvanian—Permian Pha Nok Khao (PNK) carbonate platform in the Loei-Phetchabun Foldbelt provides a direct analogue for gas-producing subsurface platforms beneath the nearby Khorat Basin. Although phylloid algal reef mounds are recognised across the PNK Platform, to date only patch reefs and isolated mounds have been described. This study describes two sections representing an ~80-m-thick succession of closely spaced phylloid reef mounds and intermound facies. Reef mounds are interbedded with deep to shallow subtidal lagoon and tidal flat facies and are interpreted to have formed on the inner platform. The phylloid reef mounds follow the build-and-fill style of growth, in which relief-building and relief-filling represent separate stages. Between mounds, lagoonal sediments fill topographic lows. Subsequent reef mounds were not restricted to building on existing mounds, but distributed within the inner platform. Thick peritidal facies overlie the mounds suggesting development of a shallow carbonate platform in this region during overall regressive conditions in the Late Pennsylvanian (Moscovian—Kasimovian).

Acclimation of a rocky shore algal reef builder Neogoniolithon sp. to changing illuminations

AbstractVermetid reefs and rocky shores are hot spots of biodiversity, often referred to as the subtropical equivalent of coral reefs. The development of the ecosystem depends on the activity of several reef builders, including red crustose coralline algae (CCA) such as Neogoniolithon brassica‐florida. Despite its importance, little is known about Neogoniolithon sp. acclimation to rapid changes in light intensity and corresponding photosynthetic activity. To overcome the large spatial variability in the light field (due to location and the porous nature of the rocks) we grew Neogoniolithon sp. on glass slides and characterized its photosynthetic performance in response to various light intensities by following O2 exchange and fluorescence parameters. This was also performed on rock‐inhabiting thalli collected from the east Mediterranean basin. Generally, maximal photosynthetic rate was reached when Neogoniolithon sp. thalli grown under low illumination (such as in protected niches where the light intensity can be as low as 1% of surface illumination) were examined. When exposed to light intensities higher than those experienced during growth, Neogoniolithon sp. activates adaptive/protective mechanisms such as state transition and nonphotochemical fluorescence quenching and increases the dark respiration thereafter. We find that the Fv/Fm parameter (variable/maximal fluorescence) is not suitable to assess photosynthetic performance in Neogoniolithon sp. and propose using instead an alternative parameter recently developed. Our findings help to clarify why Neogoniolithon sp. is usually observed in shaded niches along the reef surfaces.

Algal reefs (Coralligenous) from glacial stages: Origin and nature of a submerged tabular relief (Hyblean Plateau, Italy)

In the framework of the Italian multidisciplinary research project “Mud volcanoes Ecosystem study - Sicily Channel”, cores MV02_GC01 and MV03_GC02 were recovered from a tabular relief at 140 m water depth, to investigate the nature of such uncommon shallow seep-related morphology trough micro- and macro-paleontological, mineralogical, sedimentological and geochronological analyses.Both cores record muddy surficial sedimentation, hosting a strictly circalittoral molluskan death assemblage typical of mobile substrate, coherent with the present-day seafloor depth and environment. The core bottom recovered a biogenic framework, in which the molluskan fossil assemblage is characteristic of shallow-water, possibly infralittoral, representing a past sea level low stand. The biogenic framework shows structure and composition that are similar to present day algal reefs indicated as coralligenous build-ups. Both cores recorded the Holocene transgression. Core MV02_GC01 is longer and its basal section records cobbles and pebbles of both terrigenous and biogenic origin partially covered by a dark patina, and finely preserved Halimeda sp. fragments. The dark patina reveals a fibrous nature, often containing framboid pyrite crystals, ankerite, but no organic matter. We interpret the dark patina level as the last lowstand, possible forming in a lagoon-like paleoenvironment. Below such level, another coralligenous build-up occurs, U/Th dated to MIS 6, in agreement with the available seismic interpretation. The tabular relief lays up to 10 m above the surrounding seafloor and reveals a complex inner architecture, in which at least two generations of coralligenous build-ups shaped its geomorphological development, and the local tectonic activity contributed to its uplift.