Andre Freiwald

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Papers by Andre Freiwald

Cold-water coral framework architecture is selectively shaped by bottom current flow

Coral Reefs, Feb 28, 2023

The three-dimensional (3D) structure of habitat-forming corals has profound impacts on reef ecosy... more The three-dimensional (3D) structure of habitat-forming corals has profound impacts on reef ecosystem processes. Elucidating coral structural responses to the environment is therefore crucial to understand changes in these ecosystems. However, little is known of how environmental factors shape coral structure in deep and dark waters, where cold-water coral (CWC) reefs thrive. Here, we attempt to infer the influence of current flow on CWC framework architecture, using 3D scanning to quantify colony shape traits (volume compactness and surface complexity) in the reef-building CWC Desmophyllum pertusum from adjacent fjord and offshore habitats with contrasting flow regimes. We find substantial architectural variability both between and within habitats. We show that corals are generally more compact in the fjord habitat, reflecting the prevailing higher current speeds, although differences in volume compactness between fjord and offshore corals are more subtle when comparing the fjord with the more exposed side of the offshore setting, probably due to locally intensified currents. Conversely, we observe no clear disparity in coral surface complexity between habitats (despite its positive correlation with volume compactness), suggesting it is not affected by current speed. Unlike volume compactness, surface complexity is similarly variable within a single colony as it is between colonies within the same habitat or between habitats and is therefore perhaps more dependent than volume compactness on microenvironmental conditions. These findings suggest a highly plastic, trait-specific and functionally relevant structural response of CWCs to current flow and underscore the importance of multiple concurrent sources of hydrodynamic forcing on CWC growth.

format_quoteNordleksa displays higher mean annual horizontal flow speed (~18 cm/s) compared to Sula (~8 cm/s), influenced by tidal control.format_quote

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High‐resolution imaging sheds new light on a multi‐tier symbiotic partnership between a “walking” solitary coral, a sipunculan, and a bivalve from East Africa

Ecology and Evolution, 2022

Marine symbioses are integral to the persistence of ecosystem functioning in coral reefs. Solitar... more Marine symbioses are integral to the persistence of ecosystem functioning in coral reefs. Solitary corals of the species Heteropsammia cochlea and Heterocyathus aequicostatus have been observed to live in symbiosis with the sipunculan worm Aspidosiphon muelleri muelleri, which inhabits a cavity within the coral, in Zanzibar (Tanzania). The symbiosis of these photosymbiotic corals enables the coral holobiont to move, in fine to coarse unconsolidated substrata, a process termed as “walking.” This allows the coral to escape sediment cover in turbid conditions which is crucial for these light‐dependent species. An additional commensalistic symbiosis of this coral‐worm holobiont is found between the Aspidosiphon worm and the cryptoendolithic bivalve Jousseaumiella sp., which resides within the cavity of the coral skeleton. To understand the morphological alterations caused by these symbioses, interspecific relationships, with respect to the carbonate structures between these three organi...

format_quoteSpecies in turbid environments exhibit flexible metabolic shifts, with coral adapting by enhancing heterotrophic feeding abilities to cope with reduced photosynthesis.format_quote

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In memoriam: Prof.dr. Erik Flügel (1934–2004)

Geologia Croatica, 2004

Dr. Erik Flügel has died. We lost not only the founder of the Institute of Paleontology of the Un... more Dr. Erik Flügel has died. We lost not only the founder of the Institute of Paleontology of the University Erlangen-Nuremberg, but also an internationally renowned and highly regarded scientist. He was a passionate researcher, ardent teacher, unrelenting science manager, but also a loyal and encouraging colleague and a reliable friend. Erik Flügel was born on April 6, 1934 in Steiermark, Austria. From 1940 to 1952 he attended the primary and secondary school at Graz where he earned his "Abitur". In 1952 he commenced his studies of geology and paleontology as well as mineralogy and petrography at the Universities of Graz and Marburg, and completed his degree in July 1957 in Graz with a PhD thesis dealing with the revision of Devonian hydrozoans of the Graz area. Until 1962 he worked at the Natural History Museum in Vienna where he completed his post-doctorate in paleontology. From 1962 on Erik Flügel worked as "Wissenschaftlicher Rat" at the Technical University of Darmstadt, Germany, where he became a professor in 1968. In 1971 he extended his venia legendi to include geology. Since 1972 he chaired the newly formed Institute of Palaeontology at the University of Erlangen-Nuremberg, which he led until his retirement in 1999.

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Changes in sponge bioerosion: from experimental evidence to monitoring guidelines

F1000Research, 2012

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Circulation and Ecosystems in the Subpolar and Polar North Atlantic Cruise No. 2

Page 4.1 Participants 4-3 4.2 Research Programme 4-4 4.3 Narrative of the cruise 4-5 4.4 Prelimin... more Page 4.1 Participants 4-3 4.2 Research Programme 4-4 4.3 Narrative of the cruise 4-5 4.4 Preliminary results 4-9 4.4.1 Hydrography and circulation in the Fram Strait 4-9 4.4.2 Ecosystems time series studies and experimental work in the deep Arctic Ocean 4-24 4.4.3 Interdisciplinary investigations at the deep-sea long-term observatory Hausgarten 4-25 4.4.4 Latitudinal shifts in deep sea nematode assemblages 4-28 4.4.5 Carbon remineralisation by the benthic community 4-28 4.4.6 Responses of deep-sea nematode assemblages to increase food availability 4-29 4.4.7 Biofouling experiments at the deep seafloor 4-30 4.4.8 Biodiversity and ecology of deep-sea copepods 4-32 4.5 Station List 4-34 4.

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Bathyal species in Rissoidae (Gastropoda) from Azorean seamounts

Biodiversity Journal, 2021

Three new species in the family Rissoidae (Gastropoda) have been found in bioclastic sediment sam... more Three new species in the family Rissoidae (Gastropoda) have been found in bioclastic sediment samples taken on the bathyal slopes of two Azorean seamount areas during the cruise M151 Athena by R/V Meteor: Alvania templadoi n. sp., Crisilla avilai n. sp. and Crisilla herosae n. sp. A review of endemicity in bathyal rissoids is presented; the large majority (81%) of the rissoids are endemic to the Azorean region. The distribution of species is frequently (20% of rissoids) limited to a single seamount, a seamount cluster or to the full Azorean seamounts and islands province. The degree of endemicity is comparable between the northern and southern Azorean seamount areas and between shallow-water species and bathyal species in the northern area. Endemic species and genera evolved after the formation of the islands and seamounts during the Neogene following an early population by species from eastern Atlantic genera.

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Host influenced geochemical signature in the parasitic foraminifer Hyrrokkin sarcophaga

Hyrrokkin sarcophaga is a parasitic foraminifera that is commonly found in cold-water coral reefs... more Hyrrokkin sarcophaga is a parasitic foraminifera that is commonly found in cold-water coral reefs where it infests the file clam Acesta excavata and the scleractinian coral Desmophyllum pertusum (formerly known as Lophelia pertusa). Here, we present measurements of the trace element and isotopic composition of these parasitic foraminifera, analyzed by inductively coupled optical emission spectrometry (ICP-OES), electron probe microanalysis (EPMA) and mass spectrometry (gas-source MS and inductively-coupledplasma MS). Our results reveal that the geochemical signature of H. sarcophaga depends on the host organism it infests. Sr / Ca ratios are 1.1 mmol mol −1 higher in H. sarcophaga that infest D. pertusum, which could be an indication that dissolved host carbonate material is utilized in shell calcification, given that the aragonite of D. pertusum has a naturally higher Sr concentration compared to the calcite of A. excavata. Similarly, we measure 3.1 ‰ lower δ 13 C and 0.25 ‰ lower δ 18 O values in H. sarcophaga that lived on D. pertusum, which might be caused by the direct uptake of the host's carbonate material with a more negative isotopic composition or different pH regimes in these foraminifera (pH can exert a control on the extent of CO 2 hydration/hydroxylation) due to the uptake of body fluids of the host. We also observe higher Mn / Ca ratios in foraminifera that lived on A. excavata but did not penetrate the host shell compared to specimen that penetrated the shell, which could be interpreted as a change in food source, changes in the calcification rate, Rayleigh fractionation or changing oxygen conditions. While our measurements provide an interesting insight into the calcification process of this unusual foraminifera, these data also indicate that the geochemistry of this parasitic foraminifera is unlikely to be a reliable indicator of paleoenvironmental conditions using Sr / Ca, Mn / Ca, δ 18 O or δ 13 C unless the host organism is known and its geochemical composition can be accounted for.

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Cold-water coral reefs thriving under hypoxia

Coral Reefs, 2020

Reefs formed by scleractinian cold-water corals represent unique biodiversity hot spots in the de... more Reefs formed by scleractinian cold-water corals represent unique biodiversity hot spots in the deep sea, preferring aphotic water depths of 200–1000 m. The distribution of the most prominent reef-building species Lophelia pertusa is controlled by various environmental factors including dissolved oxygen concentrations and temperature. Consequently, the expected ocean deoxygenation and warming triggered by human-induced global change are considered as a serious threat to cold-water coral reefs. Here, we present results on recently discovered reefs in the SE Atlantic, where L. pertusa thrives in hypoxic and rather warm waters. This sheds new light on its capability to adapt to extreme conditions, which is facilitated by high surface ocean productivity, resulting in extensive food supply. Putting our data in an Atlantic-wide perspective clearly demonstrates L. pertusa’s ability to develop population-specific adaptations, which are up to now hardly considered in assessing its present and...

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Natural history collections as a basis for sound biodiversity assessments: Plexauridae (Octocorallia, Holaxonia) of the Naturalis CANCAP and Tyro Mauritania II expeditions

ZooKeys, 2019

Mapping biodiversity is the marathon of the 21st Century as an answer to the present extinction c... more Mapping biodiversity is the marathon of the 21st Century as an answer to the present extinction crisis. A century in which science is also characterised by large scientific datasets collected through new technologies aiming to fill gaps in our knowledge of species distributions. However, most species records rely on observations that are not linked to specimens, which does not allow verification of species hypotheses by other scientists. Natural history museums form a verifiable source of biodiversity records which were made by taxonomists. Nonetheless, these museums seem to be forgotten by biologists in scientific fields other than taxonomy or systematics. Naturalis Biodiversity Center (NBC) in Leiden is care keeper of large collections of marine organisms, which were sampled in the Northeast Atlantic during the CANCAP and Tyro Mauritania II expeditions (1976–1988). Many octocorals were sampled and deposited in the NBC collection, where they became available for study and were part...

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Last snails standing since the Early Pleistocene, a tale of Calliostomatidae (Gastropoda) living in deep-water coral habitats in the north-eastern Atlantic

Zootaxa, 2019

Three species in the gastropod genus Calliostoma are confirmed as living in Deep-Water Coral (DWC... more Three species in the gastropod genus Calliostoma are confirmed as living in Deep-Water Coral (DWC) habitats in the NE Atlantic Ocean: Calliostoma bullatum (Philippi, 1844), C. maurolici (Seguenza, 1876) and C. leptophyma Dautzenberg & Fischer, 1896. Up to now, C. bullatum was only known as fossil from Early to Mid-Pleistocene outcrops in DWC-related habitats in southern Italy; our study confirmed its living presence in DWC off Mauritania. A discussion is provided on the distribution of DWC-related calliostomatids in the NE Atlantic and the Mediterranean Sea from the Pleistocene to the present.

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Environmental factors influencing cold-water coral ecosystems in the oxygen minimum zones on the Angolan and Namibian margins

Biogeosciences Discussions, 2019

Fossil cold-water coral mounds overgrown by sponges and bryozoans were observed in anoxic conditi... more Fossil cold-water coral mounds overgrown by sponges and bryozoans were observed in anoxic conditions on the Namibian margin, while mounds colonized by thriving cold-water coral reefs were found in hypoxic conditions on the Angolan margin. These low oxygen conditions do not meet known environmental ranges favoring cold-water corals and hence are expected to provide unsuitable habitats for cold-water coral growth and therefore reef formation. To explain why the living fauna can nevertheless thrive in both areas, present day environmental conditions at the southwestern African margin were assessed. Downslope CTD transects and the deployment of bottom landers were used to investigate spatial and temporal variations of environmental properties. Temporal measurements in the mound areas recorded oscillating low dissolved oxygen concentrations of 0-0.17 ml l-1 (≙ 0-9 % saturation) on the Namibian and 0.5-1.5 ml l-1 (≙ 7-18 % saturation) on the Angolan margin, which were associated with relatively high temperatures (11.8-13.2°C and 6.4-12.6°C respectively). Semi-diurnal barotrophic tides were found to interact with the margin topography producing internal waves with excursions of up to 70 and 130 m for the Namibian and Angolan margins, respectively. These tidal movements temporarily deliver water with more suitable characteristics to the coral mounds from below and above the hypoxic zone. Concurrently, the delivery of high quantity and quality of suspended particulate organic matter was observed, which serves as a food source for cold-water corals. On the Namibian slope organic matter indicates a completely marine source and originates directly from the surface productive zone, whereas on the Angolan margin the geochemical signature of organic material suggest an additional mechanisms of food supply. A nepheloid layer observed above the cold-water coral mound area on the Angolan margin may constitutes a reservoir of fresh organic matter, facilitating a constant supply of food particles by tidal mixing. This suggests that the cold-water coral communities as well as the associated fauna may compensate unfavorable conditions induced by low oxygen levels and high temperatures with an enhanced availability of food. With the expected expansion of oxygen minimum zones in the future due to anthropogenic activities, this study provides an example on how ecosystems could cope with such extreme environmental conditions.

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Testing the applicability of a benthic foraminiferal-based transfer function for the reconstruction of paleowater depth changes in Rhodes (Greece) during the early Pleistocene

PloS one, 2017

We present paleo-water depth reconstructions for the Pefka E section deposited on the island of R... more We present paleo-water depth reconstructions for the Pefka E section deposited on the island of Rhodes (Greece) during the early Pleistocene. For these reconstructions, a transfer function (TF) using modern benthic foraminifera surface samples from the Adriatic and Western Mediterranean Seas has been developed. The TF model gives an overall predictive accuracy of ~50 m over a water depth range of ~1200 m. Two separate TF models for shallower and deeper water depth ranges indicate a good predictive accuracy of 9 m for shallower water depths (0-200 m) but far less accuracy of 130 m for deeper water depths (200-1200 m) due to uneven sampling along the water depth gradient. To test the robustness of the TF, we randomly selected modern samples to develop random TFs, showing that the model is robust for water depths between 20 and 850 m while greater water depths are underestimated. We applied the TF to the Pefka E fossil data set. The goodness-of-fit statistics showed that most fossil sa...

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Laser Ablation - Accelerator Mass Spectrometry: a novel approach for rapid radiocarbon analyses of carbonate archives at high spatial resolution

Analytical chemistry, Sep 11, 2016

A new instrumental setup, combining laser ablation (LA) with accelerator mass spectrometry (AMS),... more A new instrumental setup, combining laser ablation (LA) with accelerator mass spectrometry (AMS), has been investigated for the online radiocarbon ((14)C) analysis of carbonate records. Samples were placed in an in-house designed LA-cell and CO2 gas was produced by ablation using a 193 nm ArF excimer laser. The (14)C/(12)C abundance ratio of the gas was then analyzed by gas ion source AMS. This configuration allows flexible and time resolved acquisition of (14)C profiles in contrast to conventional measurements, where only the bulk composition of discrete samples can be obtained. Three different measurement modes, i.e. discrete layer analysis, survey scans and precision scans, were investigated and compared using a stalagmite sample and, subsequently, applied to terrestrial and marine carbonates. Depending on the measurement mode, a precision of typically 1-5 % combined with a spatial resolution of 100 µm can be obtained. Prominent (14)C features, such as the atomic bomb (14)C peak,...

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