Andres Rüggeberg

Sedimentary patterns in the vicinity of a carbonate mound in the Hovland Mound Province, northern Porcupine Seabight

Large carbonate mound structures have been discovered in the northern Porcupine Seabight (Northeast Atlantic) at depths between 600 and 1000 m. These mounds are associated with the growth of deep-sea corals Lophelia pertusa and Madrepora oculata. In this study, three sediment cores have been analysed. They are from locations close to Propeller Mound, a 150 m high ridge-like feature covered with a cold-water coral ecosystem at its upper flanks. The investigations are concentrated on grain-size analyses, carbon measurements and on the visual description of the cores and computer tomographic images, to evaluate sediment content and structure.

Bioluminescence in deep-sea isidid gorgonians from the Cape Verde archipelago

Cold-water corals, and in particular numerous gorgonian species, occur abundantly on the deep slopes of the Cape Verde archipelago (Fig. 1a). Among them, the isidid gorgonian genus Keratoisis occurred frequently. A living Keratoisis sp. was ROV collected (KIEL 6000) from 3,052 m (16 42.3¢N, 25 34.9¢W) in the Charles Darwin Volcanic Field (1b) during METEOR cruise M80/3. A strong luminescence was accidentally observed when this bamboo coral arrived on deck in the early evening hours just before sunset. The entire stem and branch tissue showed a dull blue luminescence. Additionally, when touched, it emitted a very strong blue light (Fig. 1c) that persisted for a few seconds. Coral tissue lit up strongest and flash like at the point of stimulation, and the illumination spread in a wave across the coenenchyme of the distal branches. The most intense light emission originated from the non-retractile sclerite-rich feeding polyps and remained visible for several minutes before it slowly faded. This phenomenon could be reproduced several times within hours. Luminescence in octocorals has been observed in the alcyonarian Anthomastus sp., as well as in isidid gorgonians (Isidella, Keratoisis, and Lepidisis), primnoid gorgonians (Primnoisis and Thouarella), and in Iridigorgia and Acanthogorgia (Herring 1987). Muzik (1978) documented bioluminescence in the isidid gorgonian Lepidisis olapa off Hawaii, and Etnoyer (2008) mentioned luminescent capabilities for Isidella tentaculum from the northeast Pacific. Just recently, bioluminescence was reported for Keratoisis flexibilis and for the zoanthid Gerardia sp. from the Gulf of Mexico (http://oceanexplorer.noaa.gov/explorations/09bioluminescence/). Likely due to the scarce availability of direct deep-sea sampling and observation, there are no further Atlantic records for bioluminescence in the Keratoisidinae outside the Gulf of Mexico. Our additional observations support that bioluminescence in Keratoisis and in other deep-sea gorgonians is rather common and deserves detailed in situ observations.

RV POSEIDON Cruise Report POS473 LORELEI II: LOphelia REef Lander Expedition and Investigation II, Tromsø – Bergen – Esbjerg, 15.08. – 31.08. – 04.09.2014

As a result of the raising CO2-emissions and the resultant ocean acidification (decreasing pH and carbonate ion concentration), the impact on marine organism that build their skeletons and protective shells with calcium carbonate (e.g., mollusks, sea urchins, coccolithophorids, and stony corals) becomes more and more detrimental. In the last few years, many experiments with tropical reef building corals have shown, that a lowering of the carbonate ion concentration significantly reduces calcification rates and therefore growth (e.g., Gattuso et al. 1999; Langdon et al. 2000, 2003; Marubini et al. 2001, 2002). In the middle of this century, many tropical coral reefs may well erode faster than they can rebuild. Cold-water corals are living in an environment (high geographical latitude, cold and deep waters) already close to a critical carbonate ion concentration below calcium carbonate dissolves. Actual projections indicate that about 70% of the currently known Lophelia reef structures will be in serious danger until the end of the century (Guinotte et al. 2006). Therefore L. pertusa was cultured at GEOMAR to determine its long-term response to ocean acidification. Our work has revealed that – unexpectedly and controversially to the majority of warm-water corals – this species is potentially able to cope with elevated concentrations of CO2. Whereas short-term (1 week) high CO2 exposure resulted in a decline of calcification by 26-29 % for a pH decrease of 0.1 units and net dissolution of calcium carbonate, L. pertusa was capable to acclimate to acidified conditions in long-term (6 months) incubations, leading to slightly enhanced rates of calcification (Form & Riebesell, 2012). But all these studies were carried out in the laboratory under controlled conditions without considering natural variability and ecosystem interactions with the associated fauna. Moreover, only very little is known about the nutrition (food sources and quantity) of cold-water corals in their natural habitat. In a multifactorial laboratory study during BIOACID phase II we could show that food availability is one of the key drivers that promote the capability of these organisms to withstand environmental pressures such as alterations in the carbonate chemistry and temperature (Buscher, Form & Riebesell, in prep.). To take into account the influences of natural fluctuations and interactions (e.g. bioerosion), we aim to merge in-situ results from the two research cruises POS455 and POS473 with laboratory experimental studies for a comprehensive understanding of likely ecosystem responses under past, present and future environmental conditions.