Friederike Hoffmann

University of Bergen | UiB · Department of Biological Science

Sponges are commonly known as general nutrient providers for the marine ecosystem, recycling organic matter into various forms of bioavailable nutrients such as ammonium and nitrate. In this study we challenge this view. We show that nutrient removal through microbial denitrification is a common feature in six cold-water sponge species from boreal...

Sponges are commonly known as general nutrient providers for the marine ecosystem, recycling organic matter into various forms of bio-available nutrients such as ammonium and nitrate. In this study we challenge this view. We show that nutrient removal through microbial denitrification is a common feature in six cold-water sponge species from boreal...

To meet the increasing global energy demand, expanding exploration for oil and gas reserves as well as associated drilling activities are expected in the Arctic-boreal region where sponge aggregations contribute to up to 90% of benthic biomass. These deep-water sponges along with their microbial endobionts play key roles in the nitrogen cycling in...

During the last decades, our knowledge about the activity of sponge-associated microorganisms and their contribution to biogeochemical cycling has gradually increased. Functional groups involved in carbon and nitrogen metabolism are well documented, whereas knowledge about microorganisms involved in the sulfur cycle is still limited. Both sulfate r...

After disinfection of ballast water, it is crucial to detect organisms and determine their vitality to assess the performance of the chosen treatment technique. Ultraviolet (UV) irradiation is a treatment technology commonly used for water disinfection. In this study, the phytoplankter Tetraselmis suecica was UV irradiated and subsequently stained...

This study investigates different UV doses (mJ/cm(2)) and the effect of dark incubation on the survival of the algae Tetraselmis suecica, to simulate ballast water treatment and subsequent transport. Samples were UV irradiated and analyzed by flow cytometry and standard culturing methods. Doses of ≥400mJ/cm(2) rendered inactivation after 1day as me...

Elucidation of macroevolutionary transitions between diverse animal body plans remains a major challenge in evolutionary biology. We address the sponge-eumetazoan transition by analyzing expression of a broad range of eumetazoan developmental regulatory genes in Sycon ciliatum (Calcispongiae). Here we show that many members of surprisingly numerous...

Cold-water coral reefs are known to locally enhance the diversity of deep-sea fauna as well as of microbes. Sponges are among the most diverse faunal groups in these ecosystems, and many of them host large abundances of microbes in their tissues. In this study, twelve sponge species from three cold-water coral reefs off Norway were investigated for...

Cold-water coral reef ecosystems are recognized as biodiversity hotspots in the deep sea, but insights into their associated bacterial communities are still limited. Deciphering principle patterns of bacterial community variation over multiple spatial scales may however prove critical for a better understanding of factors contributing to cold-water...

Geographical and topographical setting of sampling events at Røst. (A) Røst bathymetry, including dive transects at Røst-in (reef center) and Røst-out (reef periphery; map: courtesy of V. Unnithan, JUB), (B) Røst transversal scheme (not to scale) indicating topographical reef structure, geomorphological reef zoning and single sampling stations (ree...

Partitioning of bacterial OTUs between distinct coral-associated and ambient microbial habitats. Numbers indicate the amount of OTUs unique to each microbial habitat, or common to any two or all microbial habitats: (A) Bacterial OTUs associated with samples of white L. pertusa (left), red L. pertusa (middle) or M. oculata (right) and their ambient...

NMDS ordinations of ARISA community profiles per microbial habitat. For each microbial habitat type, differences in bacterial community structure are plotted as related to reef site, reef boundary, geomorphologic reef zoning, coral species and color. Objects represent consensus signals for all PCR triplicates per sample and share a more similar com...

Overview on sampling events of living coral specimens, seawater and sediments at the different study sites. wL = white L. pertusa, rL = red L. pertusa, rM = red M. oculata. aSample lost during processing. The full station list of ARKXXII/1a is available via the PANGAEA database at: http://www.pangaea.de/ddi?retr=events/HERMES/ARK-XXII_1a.retr&conf=...

Sponge species (along with their field number) used in this study. A. Geodia barretti, PS70/40-4(1). B. Geodia atlantica, PS70/27-1(12). C. Geodia phlegraei, PS70/27-1(6). D. Geodia macandrewii, PS70/15(1). E. Pachymatisma normani, PS70/13-1(1). F. Craniella zetlandica, PS70/9-4(6). G. Poecillastra compressa, PS70/19-7(1). H. Plakortis sp., PS70/13...

Pairwise Bray-Curtis dissimilarity relationships between all community profiles. Samples are grouped according to microbial habitat type, coral species and color, geomorphologic reef zoning, reef boundary (incl. distances away from the apparent reef margin), and reef site. Cell position corresponds to the symmetrical pairing of single sample groups...

PERMANOVA of coral-associated bacterial variation done at Røst. A) Analyses considering A) reef boundary, i.e. in/out-reef location (IN-OUT) and B) geomorphologic reef zoning (ZONE) within Røst-in. aSource of variation. bAmount of explained variation. cSignificance level, assessed by 999 random permutations (*** P≤0.001, ** P≤0.01, * P≤0.05). dSign...

The association of archaea with marine sponges was first described 15 years ago and their role in the nitrification process in Mediterranean and tropical sponges has been suggested. Here we explore the occurrence and abundance of potential ammonia-oxidizing archaea (AOA) in four morphologically different cold-water sponges (Phakellia ventilabrum, G...

The oxygen dynamics and pumping behavior in Dysidea avara and Chondrosia reniformis (Porifera, Demospongiae) were investigated using oxygen microelectrodes and heated thermistor flow sensors. Both field and laboratory experiments showed the common occurrence of low oxygenation approaching anoxia in both species, lasting up to 1 h. Strong temporal a...

Aerobic and anaerobic microbial key processes were quantified and compared to microbial numbers and morphological structure in Mediterranean sponges. Direct counts on histological sections stained with DAPI showed that sponges with high microbial abundances (HMA sponges) have a denser morphological structure with a reduced aquiferous system compare...

Marine sponges constitute major parts of coral reefs and deep-water communities. They often harbour high amounts of phylogenetically and physiologically diverse microbes, which are so far poorly characterized. Many of these sponges regulate their internal oxygen concentration by modulating their ventilation behaviour providing a suitable habitat fo...

The discovery of large ecosystems of cold-water corals (CWC), stretching along continental margins in depths of hundreds to thousands of meters, has raised many questions regarding their ecology, biodiversity and relevance as deep-sea hard-ground habitat. This study represents the first investigation that explicitly targets bacterial diversity from...

Particulate (POM) and dissolved organic matter (DOM) released by the cold water corals Lophelia pertusa (L.) and Madrepora oculata (L.) was collected, analysed and quantitatively compared to that released by warm water reef-building corals. Particulate nitrogen (PN) and particulate organic carbon (POC) release rates of L. pertusa were 0.14 +/- 0.07...

The Mediterranean sponge Aplysina aerophoba kept in aquaria or cultivation tanks can stop pumping for several hours or even days. To investigate changes in the chemical microenvironments, we measured oxygen profiles over the surface and into the tissue of pumping and non-pumping A. aerophoba specimens with Clark-type oxygen microelectrodes (tip dia...

The present publication presents oxygen properties and pumping behaviour of Dysideaavara. Oxygen profiles were measured near and inside the atrial space of the osculum with a Clark-type micro-electrode. Pumping sponges had profiles with oxygen concentrations marginally lower than that of the aquarium water. In contrast, diffusive profiles, with a c...

This essay is the outcome of a colloquium convened in November 2005 at the Benthos Laboratory of the Stazione Zoologica Anton Dohrn in Ischia, Italy, on chemical ecology and the role of secondary metabolites in the structuring and functioning of marine biodiversity. The participants of the workshop are part of the European Network of Excellence Mar...

To determine the stability and specificity of microbes associated with the marine cold-water sponge Geodia barretti during cultivation, we compared the microbial community of freshly retrieved specimens to that of cultivated explants by fluorescence in situ hybridization (FISH). G. barretti hosts a specific homogeneous microbial community in its me...

Sponges can host vast amounts of phylogenetically and physiologically diverse microorganisms in their mesohyl. Descriptions of anaerobic microbes inhabiting sponge mesohyls have questioned the general assumption that sponge tissue is well-oxygenated due to continuous percolation by oxygen-rich water. We applied Clark-type oxygen-microelectrodes wit...

The associated microbial community in the mesohyl of the Arctic deep-water sponge Tentorium semisuberites Schmidt, 1870 (Hadromerida, Demospongiae) is dominated by Archaea. This is the result of an integral approach applying analyses of microbial lipid biomarkers as well as microscopic investigations using differential fluorescence in situ hybridis...

Oxygen microprofiles were measured over the boundary layer and into the tissue of 10-day-old cultivated tissue fragments (explants of 2-4 cm 3) from the choanosome of the cold-water sponge Geodia barretti with oxygen-sensitive Clark-type microelectrodes. At this time of cultivation, the surface tissue and the aquiferous system of the explants is re...

Associated microorganisms have been described in numerous marine sponges. Their metabolic activity, however, has not yet been investigated in situ. We quantified for the first time microbial processes in a living sponge. Sulfate reduction rates of up to 1200 nmol cm-3 d-1 were measured in the cold-water bacteriosponge Geodia barretti. Oxygen profil...

In various specimens of the deep-water sponge Geodia barretti, inclusions consisting of siliciclastic sediment were found, with spicules of G. barretti as main clasts. The inclusions were clearly separated from the surrounding tissue by a cortex of microscleres. Some were entirely surrounded by sponge tissue, while others were connected to the spon...

Siliceous and calcareous sponges commonly are treated with acid to remove the spicules prior to embedding and cutting for histological investigations. Histology of spiculated sponge tissue represents a challenging problem in sponge histotechnology. Furthermore, fluorescence in situ hybridization (FISH), a key method for studying sponge-associated m...

A cultivation method has been developed for the boreal deep-water sponge Geodia barretti (Demospongiae, Geodiidae), a species which is common in the deep Norwegian fjords. The species is known to contain secondary metabolites which are biologically active. Choanosomal fragments of 2-4 cm(3) (approximately 3-7 g) were kept in half-open systems. Cica...

In recent years, a large diversity of sponge-microbe associations has been described: sponges can harbour archaea, eubacteria (including cyanobacteria), microalgae, fungi and probably also protozoa. The current paper gives a brief overview of the different types of associations and describes the potential influence of symbiotic micro-organisms on b...

By means of benthic landers, sediment core incubations and the whole core squeezing (WCS) technique, benthic exchange and mineralization rates were investigated in 4 different fjords of Arctic Norway (Svalbard). These coastal sediments experience constant low temperatures close td 0 degrees C. The sediments were dominated by large densities of bioi...

Göttingen, University, Diss., 2003. Computerdatei im Fernzugriff.