Marine Research

This study focuses on bioerosion of an aphotic deep-water coral mound, the Propeller Mound, in the northern Porcupine Seabight. The predominant framework builder is the cosmopolitan cold-water coral Lophelia pertusa. We demonstrate bioerosion patterns within the skeleton of L. pertusa using a new embedding method under vacuum conditions with subsequent scanning electron microscope analysis. Following this method, 23 ichnospecies are documented and related to heterotrophic organism groups such as Bacteria (1), Fungi (12), Bryozoa (1), Foraminifera (3), and Porifera (6). Predominant endolithic sponges in the framework of L. pertusa are Alectona millari and Spiroxya heteroclita. Owing to its characteristic growth and surface ornamentation, trace casts of Spiroxya heteroclita are correlated to the well-known trace fossil Entobia laquea.
Investigations of thin sections of post-mortem skeletons show a clearly pronounced endolithic tiering of three penetration depths. The analysed samples are divided into three macroscopic preservational stages differing in post-mortem age, and exposure of the framework. Bioerosion affects bare parts of the coral skeleton.
Bioeroders preferably settle on one side of an upright growing colony. A succession usually starts with the infestation by bacteria and fungi. Contact zones of epiliths are preferred areas for penetration by endoliths. Sponges and foraminifers appear 10 cm below the zone of living polyps, followed by boring bryozoans 15 cm below. However, in one case the sponge Spiroxya heteroclita is documented in the skeleton of living polyps. Frameworks exposed to water host 19 ichnospecies, thus forming the most diverse ichnocoenosis, whereas nine ichnospecies are documented in coral specimens buried by sediment. Mapping of epi- and endoliths in living and freshly necrotic colonies represents a useful tool for monitoring environmental conditions and define ecological “health” of deep-water corals in a rapid large-scale assessment of the state of coral reefs.

The skeleton morphology of the azooxanthellate
cold-water coral Lophelia pertusa can be strongly
inXuenced by invasive boring sponges that infest corallites
in the still living part of the colony. Atypically swollen
corallites of live Lophelia pertusa from the Galway
Mound (Belgica Carbonate Mound Province, Porcupine
Seabight, NE Atlantic), heavily excavated by boring
organisms, have been examined with a wide range of nondestructive
and destructive methods: micro-computed
tomography, macro- and microscopic observations of the
outer coral skeleton, longitudinal and transversal thin sections
and SEM analyses of coral skeleton casts. As a result,
three excavating sponge species have been distinguished
within the coral skeleton: Alectona millari, Spiroxya heteroclita
and Aka infesta. Furthermore, four main coral/ sponge growth stages have been recognised: (1) cylindrical juvenile corallite/no sponge cavities; (2) flared juvenilecorallite/linear sponge cavities (if present); (3) slightly swollen adult corallites/chambered oval sponge cavities;
(4) very swollen adult corallites/widespread cavities. The
inferred correlation between corallite morphology and boring
sponge infestation has been detected in micro-computed
tomography (micro-CT) images and conWrmed in sponge trace casts and peculiar features of coral skeleton microstructure.

The parasitic foraminifer Hyrrokkin sarcophaga predominantly infests the cold-water coral Lophelia pertusa and the co-occurring bivalve Acesta excavata, showing a commensal or parasitic behaviour. It occurs also on some other corals (e.g., Caryophyllia sarsiae), bivalves (e.g., Delectopecten vitreus) and sponges (Geodia sp.), typically in aphotic environments. The aim of the study is to describe its traces from various host substrates, to characterise its parasitic behaviour and to map the geographical distribution of the genus Hyrrokkin. Epoxy-resin casts of H. sarcophaga traces in A. excavata, C. sarsiae, D. vitreus and L. pertusa, and of H. carnivora traces in A. excavata, were SEM analysed. The boring pattern is in all cases characterised by a shallow groove of up to 7 mm in diameter (max. 2 mm deep), from which ‘whip’-shaped extensions protrude vertically into the substrate. In A. excavata the foraminifer can penetrate the entire valve to the mantle cavity, producing a thick shaft of fused ‘whips’. This parasitic attack is answered by a strong callus formation of the mollusc. One individual foraminifer can repeatedly bypass the organic-rich callus, resulting in a thick aragonite pinnacle. The trace surface texture is xenoglyph and changes with the penetrated host-microstructures. This is especially obvious on deeply penetrating trace portions (e.g., ‘whip’-shaped filaments) and is a strong indication for a chemical penetration mode (etching). The trace of Hyrrokkin is described as Kardopomorphos polydioryx igen. n., isp. n. On the substrates without the shaft, related to parasitic behaviour, Hyrrokkin might feed directly on adjacent external host tissue. H. sarcophaga is known along the North Atlantic continental margin from polar to subtropical latitudes and H. carnivora occurs on the continental margin of Mauritania, Congo and Guinea. In the Mediterranean we could document the parasitism of H. sarcophaga from Last Glacial A. excavata. Traces or detached foraminifer tests occur in Early Pleistocene cold-water coral deposits on Sicily and Rhodes. Recent H. sarcophaga has not been observed above 11°C and is scarce near 5°C water temperature. Hyrrokkin sp. was reported from the Canadian Pacific on fossil sponges and was observed on Acesta patagonica in the Beagle Channel (Chile).

This study focuses on the carbonate biodegradation processes of deep-water scleractinians from off Apulia at Santa Maria di Leuca (SML) in the Ionian Sea, including living colonies of Lophelia pertusa, Madrepora oculata and Desmophyllum dianthus. The corallites were grouped into three zones: the live zone, edge zone and dead zone. In total, 13 trace types were encountered and are attributed to borings of sponges (3), fungi (6), foraminifers (2), bacteria (1) and annelids (1). Their relative spatial appearance within the host skeletons led to the distinction between six succession stages of bioerosion. The first endobiontic traces are exclusively produced by bacteria and fungi and are already present in the edge zone, which could be attributed to their fast growth rates and/or temporal exposure of the bare skeleton to the water column. In D. dianthus the entire ichnospecies assemblage has been documented within the first 1.9cm below the live zone and represents the most condensed bioerosion succession amongst the coral species studied. The strongest degradation of corallites at SML is made by boring sponges, which can excavate 70% or more of the skeleton. The finding of a unilateral condensed succession of bioerosion stages may be linked to prevailing unidirectional strong currents. A comparison of the present ichnocoenosis with bioerosion studies from the Eastern Atlantic evidences a reduced ichnodiversity in Ionian Sea bathyal corals.

Late Pennsylvanian seep limestones (ca. 300 Ma) enclosed in the Ganigobis shales in southern Namibia formed by microbial activity. The process that induced carbonate precipitation was the anaerobic oxidation of methane. The presence of 13C-depleted pentamethylicosane (PMI) (–113‰) and a mixture of crocetane and phytane (–112‰) in concert with similarly 13C-depleted pseudohomologous series of regular isoprenoids reveals that methanotrophic archaea oxidized methane anaerobically at the ancient seep site. Biphytane and a C39 pseudohomologue are other archaeal molecular fossils with δ13C values of –99‰ and –97‰, respectively. The former presence of sulfate reducing bacteria as the syntrophic partners of methanotrophic archaea in the anaerobic oxidation of methane is indicated by isotopically depleted iso- and anteiso-alkanes. These compounds most probably derive from non-isoprenoidal monoethers and diethers, synthates of sulfate-reducing bacteria. These fi ndings show that anaerobic oxidation of methane is at least 300 m.y. old, extending the record of this process for ~140 m.y. As the molecular fossils of archaea and bacteria are preserved in a product of their own metabolic activity (i.e., methane-derived carbonates with δ13C values as low as –51‰), the syngenicity of molecular fossils and enclosing deposits is unambiguous. This reveals that microbially formed rocks can represent excellent archives for studying past biogeochemical processes

Within the siliciclastic dominated red-bed strata of the Early Devonian Wood Bay Formation, various types of calcareous deposits, characterised by
specific sedimentary structures, lithologies, microfacies, carbonate contents and stable isotope signatures, occur at different stratigraphic levels.
Pedogenic, nodular calcretes with a thickness from 40 to 150 centimetres, associated with alluvial-plain and overbank sediments, represent palaeosol
(calcisols, aridisols) development. The massive nodules show an internal mudstone fabric, calcium carbonate concentrations from 64 to 87 %
and carbon and oxygen signatures of –5.3 to –6.4 and –8.5 to –9.9 ‰, respectively. It is likely that they reflect a bio-induced carbonate precipitation
in an oxygenated near-surface setting, connected with the evaporation of ground water.
Single, up to some decimetres thick beds of calcareous mudstones and marls are characterised by a gradual colour change from reddish-brown to
grey-violet upwards, and a meshwork of desiccation cracks at the top. The sediments show calcium carbonate concentrations from 22 to 43 % and
carbon and oxygen isotope values ranging from –0.6 to –0.7 ‰ and –7.6 to –8.8 ‰, respectively. They are interpreted as deposits of relatively small,
ephemeral lakes, formed by inorganic carbonate precipitation due to the evaporation of surface water.
Individual beds and regressive, shallowing-upward sequences, up to a few metres thick, formed of calcareous mudstones to sandstones,marls to calcarenites
and argillaceous to sandy limestones represent the depositional products of perennial, low-relief, low-energy lakes. These sediments yield
carbonate concentrations from 20 to 81 % and a stable isotope composition of –2.1 to –3.1 ‰ for δ13C and –9.5 to –10.9 ‰ for δ18O. They reflect
deposition in basinal and littoral lacustrine and palustrine sub-environments, in which carbonate was formed due to inorganic, bio-induced and
biotic precipitation.
The different types of calcareous deposits formed under arid to semi-arid climatic conditions in various sub-environments of alluvial plains and
perennial lakes. Their occurrence at different stratigraphic levels within the Wood Bay Formation can be related to a gradually increasing geomorphologic
maturity of the terrestrial basin. The latter was marked by a decrease of the topographic relief and a lowering of sedimentation rates. An
increase in landscape stability, combined with a general water-level rise led to the recurrent formation of broad lake plains in the centre of the basin.

Studies in the northern Norwegian Troms district indicate that widespread carbonate dissolution and maceration phenomena are taking place, at least seasonally, on cold-temperate shelves. These processes occur preferentially within microenvironmental niches in a broadly calcium carbonate supersaturated environment. These niches appear to be associated with organic material and bacteria and suggest a case for microbial bioerosion