Environmental and biological controls on Na∕Ca ratios in scleractinian cold-water corals

Here we present a comprehensive attempt to correlate aragonitic Na∕Ca ratios from Desmophyllum pertusum (formerly known as Lophelia pertusa), Madrepora oculata and a caryophylliid cold-water coral (CWC) species with different seawater parameters such as temperature, salinity and pH. Living CWC specimens were collected from 16 different locations and analyzed for their Na∕Ca ratios using solution- based inductively coupled plasma-optical emission spectrometry (ICP-OES) measurements.The results reveal no apparent correlation with salinity (30.1–40.57 g  kg−1) but a significant inverse correlation with temperature (−0.31±0.04  mmolmol−1∘C−1). Other marine aragonitic organisms such as Mytilus edulis (inner aragonitic shell portion) and Porites sp. exhibit similar results highlighting the consistency of the calculated CWC regressions. Corresponding Na∕Mg ratios show a similar temperature sensitivity to Na∕Ca ratios, but the combination of two ratios appears to reduce the impact of vital effects and domain-dependent geochemical variation. The high degree of scatter and elemental heterogeneities between the different skeletal features in both Na∕Ca and Na∕Mg, however, limit the use of these ratios as a proxy and/or make a high number of samples necessary. Additionally, we explore two models to explain the observed temperature sensitivity of Na∕Ca ratios for an open and semi-enclosed calcifying space based on temperature-sensitive Na- and Ca-pumping enzymes and transport proteins that change the composition of the calcifying fluid and consequently the skeletal Na∕Ca ratio

Charakterisierung gerüstbildender Kaltwasserkorallenökosysteme: Fallstudien auf makro- bis mikroskopischen Betrachtungsebenen

Deep-water corals have been known for more than two centuries; however, broad scientific interest in these hardly accessible ecosystems is relatively new and strongly increasing in the last years owing to application of advanced technologies. Like their shallow-water counterparts, frame-building deep-water corals play a fundamental role in the ecology of the oceans. However, cold-water coral ecosystems have been already economically discovered and exploited by e.g., the fishing industry and jewellery industry and thus are regionally threatened. Therefore, primarily it is important to map and characterise their global distribution to deduce marine protected areas, which allow securing the oceans ecosystem balances, to establish ecologically sustainable fishing practises and to protect its potential as a rich pool for studies gaining human’s benefit. Additionally, it is essential to carry out base studies, which give insights into the biodiversity, biocoenotic interactions, the ecosystem functioning and history. The presented work attempts a cold-water coral ecosystem characterisation by different key studies on a macro and micro-scale with main focus on the North Atlantic and Mediterranean Sea. Within this context, this thesis presents a set of methodologies embedded into different key studies, some of them having been applied for the first time to this scientific field. The individual key studies are grouped thematically: (1) Cold-water corals as habitat-forming substrate (Chapter 2) and (2) interactions between substrate and its colonisers on a micro-scale (Chapter 3). Chapter 2 comprises four key studies with the main focus set on a general characterisation of cold-water coral ecosystems, in particular: (a) their abiotically triggered distribution to trace their individual environmental requirements; (b) the role of cold-water corals as habitat-forming substrate to investigate biodiversity, biocoenotic interactions and long-term influences of abiotic factors; (c) their bio-induced degradation mechanisms to gain insights into the longevity and health of coral ecosystems. In Chapter 3 two key studies are established characterising interactions between substrate and colonisers on a micro-scale with special focus on host calcification as defence mechanism against colonisation. In general, the results from Chapter 2 indicate that currents have a strong influence on the appearance of cold-water coral ecosystems by shaping the mound structures, by causing the spatial distribution of corals and mechanically also coral framework transports, by transporting nutrients and therefore triggering the 'daily routine' of the biocoenosis and by affecting on destruction processes of cold-water coral frameworks. The key studies in Chapter 3 show that carbonate precipitation by the host is in most cases an effective defence mechanism against slowly growing epibionts (e.g., serpulids) but it constitutes a limited protection mechanism against boring organisms since carbonate for the latter group does not form any border. The individual key studies presented in Chapters 2 and 3 spotlight coral ecosystems from different perspectives and scales and can be considered as pieces of a huge mosaic that contribute synergistically to the understanding of these fascinating ecosystems. An upscaling of the key studies has been carried out in Chapter 4, and their individual potential is discussed in a larger content with special focus on the methodologies applied. The final outlook depicts the general potential of cold-water coral ecosystem analyses.Die Entdeckung der Tiefwasserkorallen liegt inzwischen mehr als zwei Jahrhunderte zurück; jedoch stießen diese schwer zugängigen Ökosysteme erst in den letzten Jahren auf breites, wissenschaftliches Interesse infolge der stark expandierenden technischen Erforschungsmöglichkeiten. Entsprechend tropischen Warmwasserkorallenökosystemen nehmen gerüstbildende Tiefwasserkorallenökosysteme eine wesentliche Rolle in der Ökologie der Ozeane ein. Allerdings stehen Kaltwasserkorallenökosysteme heutzutage unter einem stark kommerziellen Druck und werden vielfältig ausgebeutet, z.B. von der Fischindustrie und von der Juwelenindustrie, und sind somit regional gefährdet. Daher ist es primär wichtig, die globale Verbreitung dieser Ökosysteme zu erfassen und sie zu charakterisieren, um marine Schutzgebiete zu etablieren und ökologisch nachhaltige Fischfangverhalten zu implementieren. Diese Maßnahmen könnten das ökologische Gleichgewicht der Ozeane sicherstellen und ihr hohes Potenzial für zukünftige Studien zum Wohle der Menschheit konservieren. Darüber hinaus ist es wichtig, parallel Studien zur Ökosystemforschung durchzuführen, die Aufschluß über Biodiversität, biozönotischen Interaktionen, Funktionalität und ihre Entstehungsgeschichte geben. Die vorliegende Arbeit charakterisiert in verschiedenen Fallstudien Kaltwasserkorallenhabitate auf makro- und mikroskopischer Betrachtungsebene. Der Hauptfokus liegt dabei auf dem Nordatlantik und dem Mittelmeer. In diesem Kontext präsentiert diese Arbeit einige Methoden, die zum ersten Mal auf diesem Feld Anwendung finden. Die aus ihr resultierenden Fallstudien liegen thematisch gruppiert vor: (1) Kaltwasserkorallen als Lebensraum schaffende Substrate und (2) Interaktionen zwischen Substrat und Besiedlungsorganismen auf mikroskopischer Betrachtungsebene. Kapitel 2 beinhaltet vier Fallstudien und der Hauptfokus ist auf eine generelle Charakterisierung von Kaltwasserkorallenökosystemen gerichtet, im Besonderen auf: (a) ihre abiotisch kontrollierte Verbreitung, um ihre jeweiligen Umweltbedürfnisse auszumachen; (b) die Rolle von Kaltwasserkorallen als Lebensraum schaffendes Substrat, um die Biodiversität, biozönotischen Interaktionen und Langzeiteinflüsse von abiotischen Faktoren zu charakterisieren; (c) ihre biologischen Abbaumechanismen, um Einblicke in Lebensdauer und Gesundheit von Korallenökosystemen zu gewinnen. In Kapitel 3 liegen zwei Fallstudien vor, in denen Interaktionen zwischen Substrat und Besiedlern betrachtet werden. Der Schwerpunkt liegt dabei auf Wirtskalkabscheidung als Verteidigungsmechanismus gegen Besiedlung auf mikroskopischer Betrachtungsebene. Die Ergebnisse des Kapitels 2 zeigen, dass Strömungen auf verschiedenen Betrachtungsebenen einen starken Einfluss auf das heutige Erscheinungsbild der Korallenökosysteme nehmen, indem sie sowohl auf die Hügelmorphologie formend wirken, die Verbreitung von Korallen steuern, was hauptsächlich ihrer Nahrungsanlieferung und Sedimentationssteuerung zuzuschreiben ist, aber auch ihrer Transportkraft, sowie im kleinskaligeren Bereich die Morphologie und räumliche Orientierung der Korallenkelche beeinflussen und ihre Abbauprozesse maßgeblich steuern. Die Fallstudien in Kapitel 3 zeigen, dass eine Karbonatfällung seitens des Wirtes in den meisten Fällen einen effektiven Verteidigungsmechanismus gegen langsam wachsende Aufwuchsorganismen, wie Serpuliden bildet, jedoch einen limitierenden Schutz gegen Bohrorganismen darstellt, da Karbonatskelett für letztere Gruppe keine Grenze definiert. Die individuellen Fallstudien in Kapitel 2 und 3 beleuchten Korallenökosysteme aus verschiedenen Perspektiven und Betrachtungsebenen und können somit als Teile eines großen Mosaiks aufgefasst werden, die synergistisch zum Verständnis dieser faszinierenden Ökosysteme beitragen. Eine Hochskalierung der Fallstudien wurde in Kapitel 4 vorgenommen, in dem darüber hinaus auch ihre individuellen Potenziale in einem größeren Zusammenhang diskutiert sind und spezieller Fokus unter anderem auf die angewandten Methoden gelegt worden ist. Der abschließende Ausblick zeichnet das generelle Potenzial von Kaltwasserkorallenökosystemstudien auf

Where Topsent went wrong: Aka infesta a.k.a. Aka labyrinthica (Demospongiae: Phloeodictyidae) and implications for other Aka spp.

Early descriptions for species of Aka were poor in detail, and the only spicule type that occurs in this genus does not vary much between species, which led to taxonomic confusion. Moreover, the type specimens of five species of Aka are lost, causing considerable problems. Mediterranean specimens of Aka were identified as Aka labyrinthica (Hancock, 1849) by Topsent (1900), even though this species was originally described from the Indo-Pacific. All following publications on Mediterranean Aka accepted Topsent's decision. We assessed this problem with new samples from the Ionian Sea. Our material consisted of only one specimen of Aka, and we had to rely mainly on spicule characters for comparison with other species. We developed a system for species recognition solely based on spicular characters and biometry, involving a combination of the parameters oxea length, width, tip form and angle of curvature. This approach was surprisingly accurate. Forming ratios of the above parameters was less helpful, but can sometimes provide additional information. We identified our sample as Aka infesta (Johnson, 1899), and describe it as a minute-fistulate species with large, multicamerate erosion traces and stout, smooth oxeas. Our data further imply that A. labyrinthica sensu Hancock has not yet been found in the Mediterranean. Aka labyrinthica sensu Topsent is a collection of different species not including A. labyrinthica sensu Hancock

Bioerosion patterns in a deep-water Lophelia pertusa (Scleractinia) thicket (Propeller Mound, northern Porcupine Seabight)

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

A new octocoral species of Swiftia (Holaxonia, Plexauridae) from the upper bathyal off Mauritania (NE Atlantic)

Three species of the genus Swiftia are known for the NE Atlantic Ocean and Mediterranean Sea. Remotely-operated vehicle (ROV) surveys and sampling on board RV Maria S. Merian during cruise MSM 16/3 ‘PHAETON’ in 2010 provided footage and specimens of octocorals off Mauritania. Micro-computed tomography (micro-CT) reveals, for the first time in taxonomy of octocorals, the three-dimensional arrangement of the sclerites in a polyp. Swiftia phaeton sp. nov. is described for the continental slope off Mauritania. This azooxanthellate octocoral is distinctive from NE Atlantic and Mediterranean congenerics by the dark red colour of the colonies (including the polyps), the presence of a layer of rod sclerites on top of the polyp mounds, and different sizes of polyps and sclerites. Using micro-CT has allowed the observation and imaging of a layer of sclerites that is distinct from other species of the same genus. ROV images revealed live records of S. phaeton sp. nov. in submarine canyons and on cold-water coral mounds in the upper-bathyal off Mauritania (396–639 m depth), mainly attached to dead coral, coral rubble, or rocks. The new species represents an extension of the genus distribution to the tropical latitudes (17°07'N and 20°14'N) of the NE Atlantic Ocean

Spicule dimensions of Siphonodictyon spp., raw data, biometry and frequency distributions

Early descriptions for species of Aka were poor in detail, and the only spicule type that occurs in this genus does not vary much between species, which led to taxonomic confusion. Moreover, the type specimens of 5 species of Aka are lost, causing considerable problems. Mediterranean specimens of Aka were identified as Aka labyrinthica (Hancock, 1849) by Topsent (1900), even though this species was originally described from the Indo-Pacific. All following publications on Mediterranean Aka accepted Topsent's decision. We assessed this problem with new samples from the Ionian Sea. Our material consisted of only one specimen of Aka, and we had to rely mainly on spicule characters for comparison to other species. We developed a system for species recognition solely based on spicular characters and biometry, involving a combination of the parameters oxea length, width, tip form and angle of curvature. This approach was surprisingly accurate. Forming ratios of the above parameters was less helpful, but can sometimes provide additional information. We identified our sample as Aka infesta (Johnson, 1899), and describe it as a minute-fistulate species with large, multicamerate erosion traces and stout, smooth oxeas. Our data further imply that A. labyrinthica sensu Hancock has not yet been found in the Mediterranean. A. labyrinthica sensu Topsent is a collection of different species not including A. labyrinthica sensu Hancock