Recovery from finfish predation on newly outplanted boulder coral colonies on three reefs in the Florida Keys

Corals throughout the Caribbean have experienced major declines since the 1970s. In response, many agencies have focused their conservation and restoration efforts on outplanting nursery-grown coral fragments onto degraded reefs. Predation on newly outplanted corals can be an important but often unmonitored factor contributing to the declining health and survival of these fragments. In this study, we outplanted 360 boulder coral fragments (Montastraea cavernosa, Orbicella faveolata, Pseudodiploria clivosa), sourced from both ex situ and in situ nurseries, at three locations in the Florida Keys. Each location included one inshore and one offshore site. Ten fragments of each species and source were outplanted at each site (60 corals per site). Transplants were monitored for finfish predation, live tissue area, and survival at 1, 2, 6, and 12 wks post-outplanting. We found the highest finfish predation for all species during the first week monitoring period. Predation during this first week varied by location and reef type, with two locations showing higher predation on offshore sites and one location experiencing increased predation on the inshore site. We also found that coral fragments produced in the ex situ nursery experienced higher initial predation compared to fragments produced in the in situ nursery. However, overall coral survival at 12 wks post-outplanting was 96%, suggesting there was no effect of initial predation on survival. Our results indicate that coral restoration efforts may be affected by intense, initial predation on newly-outplanted boulder coral colonies, but this initial predation may not lead to an increase in mortality.

Characterization of fish assemblages in mesophotic reefs of Cuba

Although mesophotic coral reef ecosystems (MCEs) are widespread and diverse, they remain largely unexplored. The Caribbean MCEs are among the most studied in the world, but detailed information regarding Cuban MCEs is limited. In this study we present the first analyses of the ichthyofauna of the Cuban MCEs based on data from a research cruise in June 2017. Forty-two sites were sampled around the Archipelago of Cuba using a Remotely Operated Vehicle at depths between 30 and 180 m. Overall, 151 species were observed, including 13 threatened species. Differences in ichthyofauna were observed between marine protected areas (MPAs) and unprotected areas, with greater abundances and species richness inside national parks. Invasive lionfish had greater abundances on the north coast, while the south coast had greater abundances and richness of threatened and commercially valuable species. A detailed analysis (Generalized Lineal Model) showed effects of depth, protection level, reef type (seamount or fringing reef), and region on abundance (as fish observed per minute), but no interaction between them. A transition was observed in the fish assemblages between the 30–60 m and 60–100 m depth ranges. Species abundance and richness decreased with increasing depth. The most represented families of commercial importance (Serranidae, Lutjanidae, and Carangidae) were well represented in the upper, middle, and lower areas of the MCEs, but dominated in deeper areas. The percentage of herbivores in the fish assemblage decreased with increasing depth, contrary to what was observed with piscivores and invertebrate feeders/piscivores. Twenty-seven functional groups were identified, with cryptic micro-invertivores and cryptic planktivores being the most abundant, while roving macro-invertivores and roving piscivores were the most functionally redundant. This research constitutes a valuable contribution to the study and management of ichthyofauna in Cuba and highlights the effectiveness of MPAs in the conservation of fish biodiversity.

Spatial assemblage structure of shallow-water reef fish in Southwest Australia

Bioregional categorisation of the Australian marine environment is essential to conserve and manage entire ecosystems, including the biota and associated habitats. It is important that these regions are optimally positioned to effectively plan for the protection of distinct assemblages. Recent climatic variation and changes to the marine environment in Southwest Australia (SWA) have resulted in shifts in species ranges and changes to the composition of marine assemblages. The goal of this study was to determine if the current bioregionalisation of SWA accurately represents the present distribution of shallow-water reef fishes across 2000 km of its subtropical and temperate coastline. Data was collected in 2015 using diver-operated underwater stereo-video surveys from 7 regions between Port Gregory (north of Geraldton) to the east of Esperance. This study indicated that (1) the shallow-water reef fish of SWA formed 4 distinct assemblages along the coast: one Midwestern, one Central and 2 Southern Assemblages; (2) differences between these fish assemblages were primarily driven by sea surface temperature, Ecklonia radiata cover, non-E. radiata (canopy) cover, understorey algae cover, reef type and reef height; and (3) each of the 4 assemblages were characterised by a high number of short-range Australian and Western Australian endemic species. The findings from this study suggest that 4, rather than the existing 3 bioregions would more effectively capture the shallow-water reef fish assemblage patterns, with boundaries having shifted southwards likely associated with ocean warming.

Bryozoan-rich stromatolites (“bryoliths”) from the Silurian of Gotland and their relation to climate-related perturbations of the carbon cycle

<p>A small but rather unique reef type occurs in the Silurian of Gotland mainly composed of encrusting bryozoans and microbial crusts, forming a complex intergrowth, which can be characterized as bryozoan-rich stromatolites, so-called “bryoliths”. The alternation of bryozoans and microbes is assumingly driven by a repeated change of hostile and more favorable conditions for metazoan growth. The surfaces of the reef bodies are composed of characteristic cauliflower structures, created by bryozoans, which are performing a finger-like growth in every direction. Other common features are bioerosion (mostly by bivalves), enigmatic encrusting echinoderms, a high abundance of organophosphatic fossil remains such as bryozoan pearls and discinid brachiopods, a high abundance of epi- and endobionts, vadose silt, and gypsum pseudomorphs.</p><p>Altogether, ten of these special reefs have been identified on Gotland so far. All of them were formed during periods of strong positive δ <sup>13</sup>C excursions at the Ireviken and Lau isotope excursions in the early Wenlock and late Ludlow, respectively. The unusual features of the bryoliths as well as their occurrence exclusively during strong positive δ <sup>13</sup>C excursions indicate very specific environmental requirements. This leads to the assumption, that whatever caused the isotope excursions also has affected these reef systems. Hence, investigating the bryoliths will hopefully increase our knowledge to what has happened during the – still enigmatic – Silurian stable isotope excursions.</p>

Parental magma, magmatic stratigraphy, and reef-type PGE enrichment of the 2.44-Ga mafic-ultramafic Näränkävaara layered intrusion, Northern Finland

About 20 mafic-ultramafic layered intrusions in the northern Fennoscandian shield were emplaced during a widespread magmatic event at 2.5–2.4 Ga. The intrusions host orthomagmatic Ni-Cu-PGE and Cr-V-Ti-Fe deposits. We update the magmatic stratigraphy of the 2.44-Ga Näränkävaara mafic-ultramafic body, northeastern Finland, on the basis of new drill core and outcrop observations. The Näränkävaara body consists of an extensive basal dunite (1700 m thick), and a layered series comprising a peridotitic–pyroxenitic ultramafic zone (600 m thick) and a gabbronoritic–dioritic mafic zone (700 m thick). Two reversals are found in the layered series. The composition of the layered series parental magma was approximated using a previously unidentified marginal series gabbronorite. The parental magma was siliceous high-Mg basalt with high MgO, Ni, and Cr, but also high SiO2 and Zr, which suggests primary magma contamination by felsic crust. Cu/Pd ratio below that of primitive mantle implies PGE-fertility. The structural position of the marginal series indicates that the thick basal dunite represents an older wallrock for the layered intrusion. A subeconomic reef-type PGE-enriched zone is found in the border zone between the ultramafic and mafic zones and has an average thickness of 25 m with 150–250 ppb of Pt + Pd + Au. Offset-type metal distribution and high sulfide tenor (50–300 ppm Pd) and R-factor (105) suggest reef formation by sulfide saturation induced by fractional crystallization. The reef-forming process was probably interrupted by influx of magma related to the first reversal. Metal ratios suggest that this replenishing magma was PGE-depleted before emplacement.

Switching between standard coral reef benthic monitoring protocols is complicated: proof of concept

Monitoring the state of coral reefs is necessary to identify drivers of change and assess effectiveness of management actions. There are several widely-used survey methods, each of which is likely to exhibit different biases that should be quantified if the purpose is to combine datasets obtained via different survey methods. The latter is a particularly important consideration when switching methodologies in long-term monitoring programs and is highly relevant to the Caribbean today. This is because of the continuing need for regionally comparable coral reef monitoring datasets and the fact that the Global Coral Reef Monitoring Network (GCRMN)-Caribbean node is now recommending a photoquadrat (PQ) method over the chain intercept transect method widely adopted by the members of the first truly regional monitoring network, Caribbean Coastal Marine Productivity Program (CARICOMP), in the early-1990s. Barbados, a member of the CARICOMP network, has been using a variation of the chain intercept method in its long-term coral reef monitoring program for more than two decades. Now a member of GCRMN-Caribbean, Barbados is considering switching to the PQ method in conformity with other regional members. Since we expect differences between methods, this study seeks to quantify the nature of those differences to inform Barbados and others considering switching methods. In 2017, both methods were concurrently implemented at 21 permanent monitoring plots across three major reef types in Barbados. Differences in % cover estimates for the six major benthic components, that is, hard corals, sponges, gorgonians, macroalgae, turf algae and crustose coralline algae, were examined within and among reef types. Overall, we found a complex pattern of differences between methods that depended on the benthic component, its relative abundance, and the reef type. We conclude that most benthic components would require a different conversion procedure depending on the reef type, and we provide an example of these procedures for Barbados. The factors that likely contribute to the complex pattern of between-method differences are discussed. Overall, our findings highlight that switching methods will be complicated, but not impossible. Finally, our study fills an important gap by underscoring a promising analytical framework to guide the comparison of ecological survey methods on coral reefs.

Elemental Distributions and Mineral Parageneses of the Skaergaard PGE–Au Mineralization: Consequences of Accumulation, Redistribution, and Equilibration in an Upward-Migrating Mush Zone

The Skaergaard PGE–Au mineralization, aka the Platinova Reef, is a syn-magmatic Platinum Group Element (PGE) and gold (Au) mineralization that formed after crystallization of ∼74% of the bulk melt of the intrusion. It is hosted in a more than 600 m deep and bowl-shaped succession of gabbroic macro-rhythmic layers in the upper 100 m of the Middle Zone. The precious metal mineralization comprises a series of concordant, but compositionally zoned, mineralization levels identified by distinct PGE, Au and Cu peaks. They formed due to local sulphide saturation in stratiform concentrations of interstitial and evolved mush melts in six MLs over > 2000 years. The PGE–Au mineralization is compared to a stack of gold-rimmed saucers of PGE-rich gabbro of upward decreasing size. Fundamentally different crystallization and mineralization scenarios have been proposed for the mineralization, including offset reef type models based on sulphide saturation in the melt from which the silicate host crystallized, and the here argued model which restricts the same processes to the melt of the inward migrating mush zone of the magma chamber. The latter is supported by: i) a 3 D summary of the parageneses of precious metal minerals and phases (> 4000 grains) from 32 samples across the mineralization; ii) a 3 D compilation of all bulk rock assay data; and iii) a principal component analysis (PCA) of PGE, Au, Cu, and selected major and trace elements. In the main PGE-mineralization level (Pd5 alias Pd-Zone) the precious metal mineral paragenesis varies across the intrusion with precious metal sulphides and Au-alloys at the W-margin to Precambrian basement, precious metal plumbide and Au- and Ag-alloys at the E-margin to flood basalts, and skaergaardite (PdCu) and intermetallic compounds and alloys of PGE–Au and Cu in the central parts of the mineralization. Precious metal parageneses are distinct for a given sector of the intrusion, i.e. drill core (local control), rather than for a given stratigraphic or temporal interval in the accumulated gabbros. The precious metal ‘grade times width’ number (average g/t x metres) for the mineralization at an upper and a lower cut off of 100 ppb PGE or Au increases from ∼20 to ∼45 g toward the centre of the mineralization due to ponding of precious metal bearing melt. A strong increase in (Pd+Pt+Au)/Cu and dominance of (PdCu) alloys in the lower and central parts of the mineralization demonstrate the partial dissolution of droplets of Cu-rich sulphide melt and fractionation of precious metal ratios. The precious metal parageneses, the distribution of precious metals in the mineralization, and the PCA support initial accumulation of precious metals in the melt of the mush in the floor, followed by equilibration, sulphide saturation, and reactions with residual and immiscible Fe-rich silicate melt in a series of macro-rhythmic layers in the stratified and upward migrating mush zone in the floor of the magma chamber. Syn-magmatic and upward redistribution of precious metals sets the Skaergaard PGE–Au Mineralization apart from conventional reef type and offset-reef type precious metal mineralizations, and characterize ‘Skaergaard type’ precious metal deposits.

Upper Devonian (Frasnian) stromatactis-bearing mud mounds, western Alberta, Canada: reef framework dominated by peloidal microcrystalline calcite

ABSTRACT Two well-preserved mud mounds, approximately 50 m thick, in the Mount Hawk Formation (Upper Devonian, Frasnian) in western Alberta provide an unparalleled opportunity to study the microstructure of this reef type in detail for this time interval. This reveals that they are composed dominantly of peloidal sediments—more than a quarter of mud mound volume—along with dense micrite, particulate micrite, bioclasts, and stromatactis cavities. Five types of peloids are differentiated: bacterial, cyanobacterial, bioclastic, intraclastic, and pseudo-peloids. Bacterial peloids were generated by bacterial metabolic activities with possibly some contribution from organomineralization in areas within spicular networks. Three subtypes of cyanobacterial peloids are distinguished based on whether they are physically reworked calcified filaments, aggregates of calcified coccoids, or precipitated within stromatolite-forming cyanobacterial mats or biofilms. Bioclastic peloids are fully micritized fragments of skeletons and shells. Intraclastic peloids are eroded fragments of early-lithified matrix. Pseudo-peloids represent artifacts of poorly preserved sponge spicular networks reflecting the interplay between dissolution of spicules and organomineralization. The distribution of the various peloid types shows specificity in different microfacies. They prove to be valuable paleoecological indicators, and taken together suggest that the mud mounds accreted within the photic zone above storm wave base but below the fair-weather wave base, during deposition of a transgressive and perhaps highstand systems tracts. They are the products reflecting a dynamic balance between constructional versus destructive processes. Bacterial peloids combined with dense micrite constitute the framework, which in turn makes up close to 40% of the mud mounds. This indicates that microbial activities are responsible for the early-indurated framework. The onset of bacterial peloid formation in the bedded sediment immediately underlying the mud mounds further demonstrates that it may have been a necessary precursor to mud-mound initiation. Bacterial peloids appear to characterize most Paleozoic and Mesozoic reefal mud mounds as an essential framework element.

UNDULAR BORE DEVELOPMENT OVER A LABORATORY FRINGING REEF

Several studies have reported the development of undular bores over fringing coral reefs (e.g, Gallagher, 1976; Nwogu and Demirbilek, 2010) but the importance of this phenomenon for reef hydrodynamics has never been studied. Yet, the transformation of a long wave (e.g., swell or infragravity wave) into an undular bore leads to significant modifications of the wave field. The formation of undulations is for example associated to a significant increase of the leading bore height. Moreover, if the undulations have enough time to develop (i.e. if the reef flat is wide enough), the initial long wave will ultimately split into a series of solitons (e.g., Grue et al., 2008). All this is likely to affect wave run-up. As reeffronted coastlines are particularly vulnerable to flooding, a good understanding of long wave transformation over the reef flat, including their possible transformation into undular bores, is crucial. In this study, we investigate undular bore development over reef-type profiles based on a series of laboratory experiments. More specifically, we aim to characterize the conditions under which undular bores develop, and analyse how their development affect the hydrodynamics at the toe of the reef-lined beach and the resulting wave run-up.