804 research outputs found

    The deepest record of the octocoral Acanthogorgia from the Red Sea

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    Octocorals (Cnidaria: Anthozoa) have a global distribution and form benthic assemblages along the depth gradient, from shallow to deep waters. They often occur below SCUBA diving limits, where they can become dominant habitat builders and aggregate different taxa. During a cruise in February 2023, one octocoral specimen was collected at 1453 m depth at Kebrit Deep, in the northern Saudi Arabian Red Sea axis, an area with extremely high temperature and salinity profiles at depth. Morphological analysis coupled with DNA barcoding using two mitochondrial markers (COI and mtMuts), revealed that the coral belongs to Acanthogorgia, a genus of azooxanthellate octocorals known to occur from 3 to 2300 m depths in cold, temperate and tropical waters. In the Red Sea, the genus was previously only known from shallower waters. Hence, we report the deepest record of the genus Acanthogorgia from the warm and saline Red Sea basin. This finding provides novel insights on deep-water octocoral diversity in the Red Sea, a still scantily explored area of the world, while emphasizing the need for further explorations at depth

    Evolution of mitochondrial and nuclear genomes in Pennatulacea

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    We examine the phylogeny of sea pens using sequences of whole mitochondrial genomes and the nuclear ribosomal cluster generated through low coverage Illumina sequencing. Taxon sampling includes 30 species in 19 genera representing 13 families. Ancestral state reconstruction shows that most sea pen mitochondrial genomes have the ancestral gene order, and that Pennatulacea with diverse gene orders are found in a single clade. The monophyly of Pennatulidae and Protoptilidae are rejected by both the mitochondrial and nuclear dataset, while the mitochondrial dataset further rejects monophyly of Virgulariidae, and the nuclear dataset rejects monophyly of Kophobelemnidae. We show discordance between nuclear ribosomal gene cluster phylogenies and whole mitochondrial genome phylogenies and highlight key Pennatulacea taxa that could be included in cnidarian genome-wide studies to better resolve the sea pen tree of life. We further illustrate how well frequently sequenced markers capture the overall diversity of the mitochondrial genome and the nuclear ribosomal genes in sea pens

    Effect of environmental and anthropogenic factors on the distribution and co-occurrence of cold-water corals

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    Cold-water corals (CWCs) are bioengineering species that can increase habitat heterogeneity and improve the deep sea’s biological diversity and ecosystem functioning. Knowledge of their distribution provides a critical baseline for assessing the effect of natural and anthropogenic impacts on these important deep-sea habitats. The aims of this study are: i) provide new data on the spatial distribution of six CWCs species in the Strait of Sicily, ii) describe the principal environmental and anthropogenic variables that play a role in shaping their distribution, iii) identify hotspots in which individuals belonging to the various species co-occur. Presence-only data of six CWCs species, ten environmental variables (depth, slope, rugosity, aspect, flowdir, temperature, salinity, north bottom current, east bottom current, chlorophyll-a), and one variable relating to bottom trawling effort (Automatic Information System – AIS) were used to predict the suitable habitats. We used Maximum Entropy modelling (MaxEnt) approach and used the AUC (area under the receiver operating characteristic curve) and TSS (true skill statistics) to evaluate the model performance. The results showed excellent AUC, TSS and AUC’s standard deviation mean values for all six species. The validation show high predictive performance. MaxEnt identified slope, depth, and rugosity as the most important predictors, showing the highest percentage contribution for all six species considered. Throughout the study area, highlyinterspecific persistent density hotspot of CWCs co-occurrence were discovered, with a total extension of 4.05 km2 where all species co-occur. Although studies on the effect of environmental and anthropogenic factors that impact the distribution of these species of conservation interest remain scarce, the results of this study offer useful guidance for decision-makers to develop necessary conservation measures

    Regional to Interhemispheric Connectivity of the Atlantic Ocean Circulation

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    This thesis investigates the connectivity and interaction of remote regions in the Atlantic Ocean based on high-resolution model experiments. Connectivity between remote regions has important implications on a range of spatial and temporal scales. It can affect global climate variability, the coherence of circulation changes on regional scales and the spreading of marine organisms. Based on several advancements in modelling, it is demonstrated how interhemispheric connectivity contributes to changes of the Atlantic Meridional Overturning Circulation (AMOC) on climate timescales. At the same time, the effect of wind-forcing and the interaction of individual AMOC pathways with eddies on regional scales are shown to be highly important to understand AMOC variability on sub-decadal timescales, with further implications on interdisciplinary research questions

    Non-native coral species dominate the fouling community on a semi-submersible platform in the southern Caribbean

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    A coral community was examined on a semi-submersible platform that was moored at the leeward side of Curaçao, in the southern Caribbean, from August 2016 until August 2017. This community included several non-native or cryptogenic species. Among them were two scleractinian corals (Tubastraea coccinea and T. tagusensis) and two octocorals (Chromonephthea sp. and an unidentified Nephtheidae sp.). This is the first reported presence of T. tagusensis in the southern Caribbean, and the genus Chromonephthea in the Caribbean region. An ascidian, Perophora cf. regina, is also reported from the southern Caribbean for the first time, as well as a coral-associated vermetid gastropod, Petaloconchus sp., first recorded in the Caribbean in 2014. Lack of biofouling management could potentially harm indigenous marine fauna through the introduction of non-native species. Therefore monitoring communities associated with semi-submersible platforms is essential to track the presence and dispersal of non-native, potentially invasive species

    Investigating patterns of deep sea coral and sponge diversity and abundance across multiple spatial scales in the Central Pacific

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    The deep sea is the largest ecosystem on the planet, comprising more than 90% of the volume that life can inhabit, yet it is the least explored biome in the world. The deep sea includes the benthos, which makes up 91.5 % of all the seafloor globally, and the water column deeper than 200 meters. It hosts a wealth of ecosystems including deep-sea vents, seamount coral gardens, abyssal plains, high-productivity whale falls, and life even in the deepest trenches. We now understand that all of these ecosystems host a variety of habitats, each with their own ecology and unique species. These ecosystems and habitats- and their associated biodiversity- provide essential ecosystem services such as carbon sequestration, nutrient regeneration, microbial processes detoxification, fisheries provisioning, and many others. However, despite the uniqueness of these ecosystems and the importance of the services they provide, we still know far less about them than we do about their shallow water and terrestrial counterparts. In this dissertation, I contribute new insights about the patterns of biodiversity in the Pacific Ocean across a large geographic area, and across a wide range of depths. To that end, in Chapter 1, I have used one of the largest ocean exploration datasets to look for patterns of the abundance and diversity across the most common benthic invertebrate families found on Pacific seamounts: Anthozoa, Porifera, and Echinodermata across the Central and Western Pacific. In addition to quantifying the diversity and abundance of known taxa, I also documented patterns of as-of-yet unidentified taxa by region, depth, and deepwater feature (seamount shape). Building on patterns associated with seamount shape that were described in Chapter 2, I focused on the effect of seamount shape on the diversity and abundance of deep-sea coral communities in Chapter 3. The analysis presented in Chapter 3 provides strong support for the novel hypothesis that gross seamount morphology is a significant driver of community composition. In Chapter 4, I focused on a single seamount to investigate biodiversity and abundance of coral and sponge taxa on a finer spatial scale, examining the role of direction (N, S, E, W) on different flanks of a single equatorial seamount. This analysis yielded interesting consistent patterns of zonation on all sides of the seamount in terms of depth, but with differences in abundance patterns on each flank for individual taxa. Finally, in Chapter 5, I took a global perspective to investigate gaps in deepwater data, with the goal of determining what regions need further exploration to conclusively determine patterns of deep-sea biodiversity, which will be critical for determining the health of deepwater ecosystems under climate change conditions with increased exploitation pressure and cooccuring with increased conservation efforts. Merging Ocean Biogeographic Information System (OBIS) records with the largest collection of deep submergence dive records ever collected, I used proposed biogeographic provinces schema to identify areas with the least supporting data. Additionally, I coupled records from OBIS with climate change projections to identify the areas with the fewest number of biodiversity records that are likely to change the fastest under different IPCC projections. These areas of low number of records and high likelihood of change by the end of the century should become priority targets for future exploration. Taken together, this dissertation provides valuable insights and generates new hypotheses about patterns and drivers of deep-sea biodiversity, and puts forth recommendations for future research and exploration efforts

    Vulnerability of reef-building corals towards global change

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    Global warming is leading to large-scale coral bleaching and mass mortality, but also to increases in tropical storms' frequency and intensity. Storms allow fragmentation of reef-building corals and can lead to near-shore salinity reduction which, combined with ocean warming, will aggravate coral distress. In order to assess the susceptibility of different coral species to these environmental stressors, small fragments of nine coral species of the Indo-Pacific region were exposed to different thermal (26°C, 30°C, 32°C) and hyposaline (26°C-33psu, 30°C-33psu, 26°C-20psu, 30°C-20psu) experimental treatments for 60 days. Several parameters were assessed at different levels of biological organization: at the organism level (total and partial mortality, and coral condition based in bleaching levels), physiological level (growth rate and regeneration rate of artificially inflicted lesions), and molecular level (superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), and lipid peroxidation (LPO)). Also, in order to test two different approaches to be applied in the monitoring of the effects of heat stress, some parameters were combined in integrated biomarker response indices, either in a molecular approach, approach A, using GST, CAT, LPO, and SOD, or in an approach that integrates the molecular, physiological and organism levels, approach B, using GST, CAT, LPO, SOD, partial mortality, and growth rate. Results indicate that Pocillopora damicornis and Stylophora pistillata were the most vulnerable at 30°C. Psammocora contigua, Turbinaria reniformis, and Galaxea fascicularis were the most tolerant species at 32°C. The species P. contigua and G. fascicularis were the most tolerant to low salinity (26°C-20psu). The species G. fascicularis was the only one capable of surviving the combined effect of high temperature and low salinity (30°C-20psu). Approach B, the most integrative approach, was considered the most adequate for evaluating the health of reef corals since it better discriminated the stress suffered by the tested species.MAREUCIBI

    Growth and Survival Performance of Transplanted Acropora Fragment in a Nursery Floating

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    The status of the condition of Indonesia's coral reefs is mostly categorized as moderate and damaged. Relatively inexpensive and easy-to-implement rehabilitation methods need to involve the participation of many stakeholders. The method of transplanting coral fragments by hanging (floating) from the surface of the water will be more efficient, especially in their maintenance. This study aims to investigate the most suitable water depth to support the growth and survival of the transplanted coral fragments. A non-factorial Completely Randomized Design (CRD) field experiment with 3 (three) treatments, namely different seedbed depths, 2 m, 4 m, and 6 m respectively. Each treatment was repeated 4 (four) times. The results of analysis of variance showed that the absolute growth rate of coral fragments transplanted by hanging from the surface of the water at different depths (2 m, 4 m, 6 m) showed no significant difference (P-value > 0.05). This shows that the environmental conditions at a depth of 2 m-6 m are relatively the same, so that on average all coral fragments have almost the same growth potential (0.29 cm/month). Meanwhile, the survival rate obtained is also very high (> 90%). These results confirm that the method of transplanting corals by hanging from the sea surface is technically feasible and gives good results. This will help many stakeholders to be involved in optimizing the economic potential value of coral reefs, as well as increasing participation in the conservation and rehabilitation of coral reefs

    Sclerochronology of deep-sea bamboo corals from the northwest Atlantic: Acanella arbuscula and Keratoisis spp.

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    Deep-sea corals provide habitat for invertebrates and fish, have high longevities, and slow growth rates, making them vulnerable to anthropogenic disturbances. The bamboo corals Acanella arbuscula and Keratoisis flexibilis have been observed in the NW Atlantic, but growth rates and ages have not been heavily studied. Growth ring counts at the proteinaceous nodes of the coral skeletons were used for aging. Both species exhibited major and minor growth rings, but major rings represent annual growth in A. arbuscula and minor rings represent annual growth in K. flexibilis, determined by comparing age estimates from ring counts to radiometrically validated specimens of each species. Ages, radial, and axial growth rates ranged from 8-29 years, 0.025 – 0.160 mm/yr, and 1.87 – 16.1 mm/yr for A. arbuscula, and 89-168 years, 0.007-0.027 mm/yr, and 1.5-5.3 mm/yr for K. flexibilis. Geographic variations in A. arbuscula growth rates were observed, with the SE Baffin Shelf specimens growing the fastest because these specimens were youngest, and ontogenetic influence on growth rates was observed, causing younger colonies to grow faster. K. flexibilis growth rates were slower than K. grayi, and this inter-specific difference can be attributed to temperature, as the K. flexibilis samples were collected in colder waters
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