Early Miocene coral reef-associated bryozoans from Colombia. Part I: Cyclostomata, “Anasca” and Cribrilinoidea Cheilostomata

This is the first of two comprehensive taxonomic works on the early Miocene (ca. 23–20 Ma) bryozoan fauna associated with coral reefs from the Siamaná Formation, in the remote region of Cocinetas Basin in the La Guajira Peninsula, northern Colombia, southern Caribbean. Fifteen bryozoan species in 11 families are described, comprising two cyclostomes and 13 cheilostomes. Two cheilostome genera and seven species are new: Antropora guajirensis n. sp., Calpensia caribensis n. sp., Atoichos magnus n. gen. n. sp., Gymnophorella hadra n. gen. n. sp., Cribrilaria multicostata n. sp., Cribrilaria nixor n. sp., and Figularia bragai n. sp. Eight species are identified only at genus level and remain in open nomenclature. Of the species found, 27% have erect colonies and 73% encrusting colonies. Both types contributed to the reef framework and produced sediment. The observed bryozoan diversity was higher in the barrier reefs than in the lagoonal patch reefs. UUID: http://zoobank.org/5c8468ef-31b0-4e7e-ba93-60a2e2f30b76.

Wave Interaction With a Shallowly Submerged Step in 2D

Water wave propagation over shallowly submerged structures is of much interest in the context of submerged wave energy devices, breakwaters or barrier reefs. This work examines waves passing over a two-dimensional shallowly submerged fixed step extending to the seabed. The problem has been modelled in CFD using the open source toolbox OpenFoam utilising the Reynolds Averaged Navier-Stokes Equations. These simulations are compared to experimental work from a previous study as means of validation and extended to larger amplitude waves for a single incident wave frequency. The flow over the step is characterised and examined in the context of developing an efficient hybrid numerical model for the problem.

Spatial Patterns and Short-term Changes of Coral Assemblages Along a Cross-shelf Gradient in the Southwestern Lagoon of New Caledonia

Coral reef assemblages generally form gradients of spatial structures which are governed by a variety of interacting physical and biological processes that vary in intensity, frequency, and spatial scale. Assessing the structure of contemporary reef assemblages may help to understand future changes and to identify appropriate conservation actions. The spatial distribution and interannual variability (from 2006 to 2008) of coral assemblages were investigated at 10 stations in the southwestern lagoon of New Caledonia, and the strength of the cross-shelf gradient was evaluated. Coral cover, generic richness, and abundance of adult and juvenile assemblages were highly variable within and among the three major reef habitats (fringing, mid-shelf, and barrier reefs). Abundance increased with distance from shore, whereas generic richness and cover were not correlated with shelf position. Assemblage composition was generally related to habitat, even though some mid-shelf and fringing reef assemblages resembled those observed on other habitats. A significant correlation between juvenile and adult distributions was recorded, suggesting that adult assemblages are partly controlled by the short-term history of recruitment patterns. The interannual variation of coral assemblages was far less pronounced, with significant changes only detected at some mid-shelf and barrier reefs, for a few genera characterised by high turn-over.

Coral reefs

Coral reefs are the ocean’s richest ecosystem in terms of biodiversity and productivity. They are restricted to tropical waters, where conditions of salinity, temperature and sedimentation are suitable. Where they grow, their main benthic organisms deposit substantial limestone skeletons, such that they effectively make their own habitat which sustains their dynamic nature and supports the wide range of species which inhabit them. Reefs grow to the low tide level, thus providing a breakwater, but the richest parts lie 5–20 metres below the surface, an area where light is still sufficient but where sediment and turbulence are not severe. Reefs may occur as narrow fringing reefs bordering a continental coast, as huge offshore barrier reefs or as series of atolls that support entire nations; the biogenic nature of corals is enormously important to mankind.

Snapshot recordings provide a first description of the acoustic signatures of deeper habitats adjacent to coral reefs of Moorea

Acoustic recording has been recognized as a valuable tool for non-intrusive monitoring of the marine environment, complementing traditional visual surveys. Acoustic surveys conducted on coral ecosystems have so far been restricted to barrier reefs and to shallow depths (10–30 m). Since they may provide refuge for coral reef organisms, the monitoring of outer reef slopes and describing of the soundscapes of deeper environment could provide insights into the characteristics of different biotopes of coral ecosystems. In this study, the acoustic features of four different habitats, with different topographies and substrates, located at different depths from 10 to 100 m, were recorded during day-time on the outer reef slope of the north Coast of Moorea Island (French Polynesia). Barrier reefs appeared to be the noisiest habitats whereas the average sound levels at other habitats decreased with their distance from the reef and with increasing depth. However, sound levels were higher than expected by propagation models, supporting that these habitats possess their own sound sources. While reef sounds are known to attract marine larvae, sounds from deeper habitats may then also have a non-negligible attractive potential, coming into play before the reef itself.

Characterizing carbonate facies using high-definition frequency decomposition: Case study from North West Australia

Carbonate facies identification is difficult using conventional seismic attributes due to subtle lithologic changes that cannot be easily recognized. Therefore, there is a need to develop new methodologies to study their evolution and their associated sedimentary processes, which will eventually lead to better prediction for reservoir-quality rocks. New insights into the Cenozoic carbonates in North West Australia have been captured with the application of a high-definition seismic attribute workflow. The workflow starts with conditioning of the seismic volume using structurally oriented noise attenuation filters to remove any random and coherent noise from the input data. It also benefits from a high-definition frequency decomposition that matches the original seismic resolution without smearing interfaces using a “matching pursuit” algorithm. A color blend of multigeometric attributes, such as semblance and conformance, has also been used in the workflow to define edges and discontinuities present in the data within carbonate deposits that are attributed to depositional geometries, such as barrier reefs. Our workflow has been developed to investigate the geomorphology and the sedimentary processes affecting Cenozoic successions in the Northern Carnarvon Basin in North West Australia. Geomorphological and sedimentological observations have been documented such as an Eocene rounded carbonate ramp with evidence of slump blocks and scarps, Middle Miocene accretions generated due to longshore drift, and the presence of Pliocene-Pleistocene patch and barrier reefs. These observations were extracted as geobodies to allow for visualization, and they can be used in an automated seismically based facies classification scheme. The new appreciations are not only useful for understanding the carbonate evolution but can also be used to identify geohazards such as slumps ahead of future drilling.