Danian cool-water coral reefs in southern Scandinavia localised over seafloor highs
Morten Bjerager, Finn Surlyk, Holger Lykke-Andersen, Nicolas Thibault, Lars Stemmerik, "published in 'Marine and Petroleum Geology', 2010, v. 27, p. 455-466"
Danian (Paleocene) reefs formed by ahermatypic scleractinian corals in relatively deep water are known in a few... more Danian (Paleocene) reefs formed by ahermatypic scleractinian corals in relatively deep water are known in a few localities in southern Scandinavia. Reflection and shallow seismic profiles, and samples from drilling and scuba diving in bridge pier excavations in Øresund, the strait between Denmark and Sweden, for the first time allow interpretation of the factors that controlled the localisation of the reefs. After the mass-extinction at the K/T boundary, reef-building scleractinian corals were absent in the Boreal early Danian in the Danish basin. Faunal evolution after the biotic crisis and a rise in relative sea level are interpreted to have favoured formation of deep-water coral reefs in the Øresund region in mid-Danian time. The reefs were 6–20 m high and 20–200 m long on the seafloor and have a patchy distribution within a bryozoan mound-dominated setting in an area of about 10 km2. They are composed of the framework-building ahermatypic scleractinian coral Dendrophyllia candelabrum with minor occurrences of bryozoans, echinoderms, gastropods and bivalves. It has been suspected that the reefs were located over contemporaneous seafloor highs but this notion was only based on comparison with similar modern deep-water reefs offshore Norway. The data from Øresund indicate that the Danian reef complex was formed over a late Maastrichtian palaeo-seafloor high, the Saltholm-Malmø High, supporting this interpretation and thus adding fundamentally to the understanding of the factors controlling the formation and localisation of these deep and cool-water coral reefs. Individual reefs were initiated and grew on eroded crests and steep south-dipping flanks of bryozoan mounds and were predominantly situated on the southern part of the high and are interpreted as growing towards NW-flowing bottom currents rich in particulate nutrients.
THESIS: 'The effect of ocean acidification upon free-living Symbiodinium spp. (Dinophyceae)'
This is a copy of my PhD thesis which contains a little more info than the peer-reviewed papers I have published so far.
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Download (.pdf) Reef response to sea-level and environmental changes during the last deglaciation: Integrated Ocean Drilling Program Expedition 310, Tahiti Sea Level
Camoin G, Seard C, Deschamps P, Webster J, Abbey E, Braga JC, Iryu Y, Durand N, Bard E, Hamelin B, Yokoyama Y, Thomas A, Hendersone G, Dussouillez P. Geology. DOI: 10.1130/G32057
Ice-sheet collapse and sea-level rise at the Bølling warming 14,600 years ago
by Alex Thomas
Past sea-level records provide invaluable information about the response of ice sheets to climate forcing. Some such... more Past sea-level records provide invaluable information about the response of ice sheets to climate forcing. Some such records suggest that the last deglaciation was punctuated by a dramatic period of sea-level rise, of about 20 metres, in less than 500 years. Controversy about the amplitude and timing of this meltwater pulse (MWP-1A) has, however, led to uncertainty about the source of the melt water and its temporal and causal relationships with the abrupt climate changes of the deglaciation. Here we show that MWP-1A started no earlier than 14,650 years ago and ended before 14,310 years ago, making it coeval with the Bølling warming. Our results, based on corals drilled offshore from Tahiti during Integrated Ocean Drilling Project Expedition 310, reveal that the increase in sea level at Tahiti was between 12 and 22 metres, with a most probable value between 14 and 18 metres, establishing a significant meltwater contribution from the Southern Hemisphere. This implies that the rate of eustatic sea-level rise exceeded 40 millimetres per year during MWP-1A.
Development of bacterial biofilms on artificial corals in comparison to surface-associated microbes of hard corals.
Numerous studies have demonstrated the differences in bacterial communities associated with corals versus those in... more Numerous studies have demonstrated the differences in bacterial communities associated with corals versus those in their surrounding environment. However, these environmental samples often represent vastly different microbial micro-environments with few studies having looked at the settlement and growth of bacteria on surfaces similar to corals. As a result, it is difficult to determine which bacteria are associated specifically with coral tissue surfaces. In this study, early stages of passive settlement from the water column to artificial coral surfaces (formation of a biofilm) were assessed. Changes in bacterial diversity (16S rRNA gene), were studied on artificially created resin nubbins that were modelled from the skeleton of the reef building coral Acropora muricata. These models were dip-coated in sterile agar, mounted in situ on the reef and followed over time to monitor bacterial community succession. The bacterial community forming the biofilms remained significantly different (R = 0.864 p<0.05) from that of the water column and from the surface mucus layer (SML) of the coral at all times from 30 min to 96 h. The water column was dominated by members of the α-proteobacteria, the developed community on the biofilms dominated by γ-proteobacteria, whereas that within the SML was composed of a more diverse array of groups. Bacterial communities present within the SML do not appear to arise from passive settlement from the water column, but instead appear to have become established through a selection process. This selection process was shown to be dependent on some aspects of the physico-chemical structure of the settlement surface, since agar-coated slides showed distinct communities to coral-shaped surfaces. However, no significant differences were found between different surface coatings, including plain agar and agar enhanced with coral mucus exudates. Therefore future work should consider physico-chemical surface properties as factors governing change in microbial diversity.
Development of bacterial biofilms on artificial corals in comparison to surface-associated microbes of hard corals.
Numerous studies have demonstrated the differences in bacterial communities associated with corals versus those in... more Numerous studies have demonstrated the differences in bacterial communities associated with corals versus those in their surrounding environment. However, these environmental samples often represent vastly different microbial micro-environments with few studies having looked at the settlement and growth of bacteria on surfaces similar to corals. As a result, it is difficult to determine which bacteria are associated specifically with coral tissue surfaces. In this study, early stages of passive settlement from the water column to artificial coral surfaces (formation of a biofilm) were assessed. Changes in bacterial diversity (16S rRNA gene), were studied on artificially created resin nubbins that were modelled from the skeleton of the reef building coral Acropora muricata. These models were dip-coated in sterile agar, mounted in situ on the reef and followed over time to monitor bacterial community succession. The bacterial community forming the biofilms remained significantly different (R = 0.864 p<0.05) from that of the water column and from the surface mucus layer (SML) of the coral at all times from 30 min to 96 h. The water column was dominated by members of the α-proteobacteria, the developed community on the biofilms dominated by γ-proteobacteria, whereas that within the SML was composed of a more diverse array of groups. Bacterial communities present within the SML do not appear to arise from passive settlement from the water column, but instead appear to have become established through a selection process. This selection process was shown to be dependent on some aspects of the physico-chemical structure of the settlement surface, since agar-coated slides showed distinct communities to coral-shaped surfaces. However, no significant differences were found between different surface coatings, including plain agar and agar enhanced with coral mucus exudates. Therefore future work should consider physico-chemical surface properties as factors governing change in microbial diversity.
NOAA in the Caribbean Newsletter
Editor-in-Chief: Dr Simon Pittman; Production Editor: Alicia Clarke
This is the 1st Issue of a new tri-annual publication called NOAA in the Caribbean Newsletter. It is a product... more This is the 1st Issue of a new tri-annual publication called NOAA in the Caribbean Newsletter. It is a product of the NOAA in the Caribbean Initiative and it aims to engage and educate regional stakeholders about on-the-ground science, management and operations led by NOAA throughout the Caribbean. Content includes stories on NOAA and partner activities; partnership profiles; new data and geoportals with Caribbean data; news from around the Caribbean and announcements of upcoming events and funding opportunities.
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Coral diseases in aquaria and in nature
Many reef coral diseases have been described affecting corals in the wild, several of which have been associated with... more Many reef coral diseases have been described affecting corals in the wild, several of which have been associated with causal agents based on experimental inoculation and testing of Koch's postulates. In the aquarium industry, many coral diseases and pathologies are known from the grey literature but as yet these have not been systematically described and the relationship to known diseases in the wild is difficult to determine. There is therefore scope to aid the maintenance and husbandry of corals in aquaria by informing the field of the scientifically described wild diseases, if these can be reliably related. Conversely, since the main driver to identifying coral diseases in aquaria is to select an effective treatment, the lessons learnt by aquarists on which treatments work with particular syndromes provides invaluable evidence for determining the causal agents. Such treatments are not commonly sought by scientists working in the natural environment due the cost and potential environmental impacts of the treatments. Here we review both wild and aquarium diseases and attempt to relate the two. Many important aquarium diseases could not be reconciled to those in the wild. In one case, however, namely that of the ciliate Helicostoma sp. as a causal agent of brown jelly syndrome in aquarium corals, there may be similarities with pathogenic agents of the wild coral diseases, such as white syndrome and brown band syndrome. We propose that Helicostoma is actually a misnomer, but improved understanding of this pathogen and others could benefit both fields. Improved practices in aquarium maintenance and husbandry would also benefit natural environments by reducing the scale of wild harvest and improving the potential for coral culture, both for the aquarium industry and for rehabilitation programmes.
Ciliate and bacterial communities associated with White Syndrome and Brown Band Disease in reef building corals.
White Syndrome (WS) and Brown Band Disease (BrB) are important causes of reef coral mortality for which causal agents... more White Syndrome (WS) and Brown Band Disease (BrB) are important causes of reef coral mortality for which causal agents have not been definitively identified. Here we use culture-independent molecular techniques (DGGE and clone libraries) to characterise ciliate and bacterial communities in these diseases. Bacterial (16S rRNA gene) and ciliate (18S rRNA gene) communities were highly similar between the two diseases. Four bacterial and nine ciliate ribotypes were observed in both diseases, but absent in non diseased specimens. Only one of the bacteria, Arcobacter sp. (JF831360) increased substantially in relative 16S rRNA gene abundance and was consistently represented in all diseased samples. Four of the eleven ciliate morphotypes detected contained coral algal symbionts, indicative of the ingestion of coral tissues. In both WS and BrB, there were two ciliate morphotypes consistently represented in all disease lesion samples. Morph1 (JN626268) was observed to burrow into and underneath the coral tissues at the lesion boundary. Morph2 (JN626269), previously identified in BrB, appears to play a secondary, less invasive role in pathogenesis, but has a higher population density in BrB, giving rise to the visible brown band. The strong similarity in bacterial and ciliate community composition of these diseases suggests that they are actually the same syndrome.
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Dynamics of bacterial community development in the reef coral Acropora muricata following experimental antibiotic treatment
Development of the bacterial community associated with the coral Acropora muricata (=formosa) was monitored using 16S... more Development of the bacterial community associated with the coral Acropora muricata (=formosa) was monitored using 16S rRNA gene-based techniques and abundance counts over time following experimental modification of the existing microbial community using the antibiotic ciprofloxacin. Abundance of bacteria was reduced >99% by the treatment, resulting in significant changes in bacterial community structure. Following redeployment to their natural environment, some settlement and re-growth of bacteria took place within a few hours, including ribosomal types that were not present, or in low abundance, in the natural microbiota. However, complete recovery of the bacterial community required longer than 96 h, which indicates a relatively slow settlement and growth of bacteria from the water column and suggests that turnover of the natural community is similarly slow. The early developing community was dominated by antibiotic-resistant bacteria from the natural microbiota that survived the treatment and proliferated in the absence of natural competitors, but also included some non-resident ribotypes colonizing from the water column. Almost, all these opportunists were significantly reduced or eliminated within 96 h after treatment, demonstrating a high resilience in the natural bacterial community. Potential pathogens, including a Clostridium sp., inhabited the coral at low abundances, only becoming prevalent when the natural microbiota was disturbed by the treatment. The healthy coral-associated microbiota appears to be strongly controlled by microbial interactions.
Temporal and spatial patterns in waterborne bacterial communities of an island reef system
The bacterial 16S rRNA gene diversity of waterborne bacterial (WBB) communities was assessed using PCR/DGGE... more The bacterial 16S rRNA gene diversity of waterborne bacterial (WBB) communities was assessed using PCR/DGGE techniques, along with sequence analysis of selected bands. 16S rRNA gene diversity varied between seasons and significant differences were recorded between night and day. However, there were no significant differences detected between low, ebb, flood and high tides when the water body sampled would have originated from completely different areas including those off-reef. These results suggest that changes in productivity and/or vertical diurnal migrations of plankton may have greater effects than large scale water movements effected by tidal flows. These results do not demonstrate a strong link between WBB communities and their underlying benthos. This either suggests a lack of coupling between the benthos and the water column (benthic-pelagic coupling) or that the processes are extremely rapid and efficient with strong mixing. Previous studies at this site have shown cycling between coral reef and lagoon sediments via coral mucus release and tidal transport, supporting the latter. We found a strong seasonality in the abundance and composition of WBB communities, with α-proteobacteria being more prevalent during winter and γ-proteobacteria during summer but quantitative PCR (qPCR) showed no significant differences in vibrios between seasons.
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Bacterial assemblages differ between compartments within the coral holobiont
It is widely accepted that corals are associated with a diverse and host species-specific microbiota, but how they are... more It is widely accepted that corals are associated with a diverse and host species-specific microbiota, but how they are organized within their hosts remains poorly understood. Previous sampling techniques (blasted coral tissues, coral swabs and milked mucus) may preferentially sample from different compartments such as mucus, tissue and skeleton, or amalgamate them, making comparisons and generalizations between studies difficult. This study characterized bacterial communities of corals with minimal mechanical disruption and contamination from water, air and sediments from three compartments: surface mucus layer (SML), coral tissue and coral skeleton. A novel apparatus (the ‘snot sucker’) was used to separate the SML from tissues and skeleton, and these three compartments were compared to swab samples and milked mucus along with adjacent environmental samples (water column and sediments). Bacterial 16S rRNA gene diversity was significantly different between the various coral compartments and environmental samples (PERMANOVA, F = 6.9, df = 8, P = 0.001), the only exceptions being the complete crushed coral samples and the coral skeleton, which were similar, because the skeleton represents a proportionally large volume and supports a relatively rich microflora. Milked mucus differed significantly from the SML collected with the ‘snot sucker’ and was contaminated with zooxanthellae, suggesting that it may originate at least partially from the gastrovascular cavity rather than the tissue surface. A common method of sampling the SML, surface swabs, produced a bacterial community profile distinct from the SML sampled using our novel apparatus and also showed contamination from coral tissues. Our results indicate that microbial communities are spatially structured within the coral holobiont, and methods used to describe these need to be standardized to allow comparisons between studies.
Visualisation of the symbiosome membrane surrounding cnidarian algal cells
Trautman DA, Hinde R, Cole L, Grant A, Quinnell R. 2002. Symbiosis 32:2: 133-146.
Virtually nothing is known of the role of the cnidarian symbiosome, primarily due to the difficulty in visualising its... more Virtually nothing is known of the role of the cnidarian symbiosome, primarily due to the difficulty in visualising its membrane. We used the fluorescent dye MDY-64 to stain symbiosome membranes surrounding algae of the anthozoan Zoanthus robustus. MDY-64 did not stain cultured symbiotic dinoflagellates, confirming that this dye binds to a membrane of host cell origin. Another fluorescent dye, amino-chloromethylcoumarin (CMAC) stained the cytoplasm of both endoderm cells and algal cells from the zoanthid, a coral and an anemone. By drawing a suspension of endoderm. cells from Z. robustus back and forth (5-7 times) through a hypodermic needle, we obtained approximately 73% of the algae in intact symbiosomes, with only 6% of the algae remaining in intact endoderm cells, and 21% free of both endoderm cell and symbiosome. About 15 additional passages of the cells through the needle removed the symbiosome membranes, leaving approximately 85% of the algae free of all host cell material. Use of detergents to remove the endoderm cell plasma membrane damaged both the symbiosome and algal membranes. Transmission electron microscopy showed variable numbers of membranes surrounding the algae. The ability to isolate dinoflagellate cells with and without symbiosome membranes will allow studies of the role of this membrane.