ALBERT

Description: Two scleractinian cold-water corals, Desmophyllum dianthus and Caryophyllia huinayensis are abundant on hard substrate, below 18 m depth, throughout the entire fjord Comau in Northern Patagonia, Chile. At “X-Huinay” (42º 23.276’ S, 72º 27.657’ W) on the western side of the central fjord, a recent mass mortality of D. dianthus occurred, while C. huinayensis survived. H2S seeps here support the formation of filamentous chemosynthetic bacterial mats. At this site, sulfide concentrations of up to 100 higher than normal ambient water values have been measured.

Description: Scleractinian corals (or stony corals) are important habitat forming organisms. Their characteristic growth creates three dimensional structures that provide shelter, settlement substrate and habitat to a diversity of organisms. This also holds true for cold water corals (CWC), but current knowledge is limited with only two decades of research. Caryophyllia huinayensis (Carins et al. 2005) is a small solitary scleractinian coral, which can serve as a model organism for the study of metabolism of CWC. This stony coral is commonly found in association with the larger scleractinian coral Desmophyllum dianthus in the Chilean Fjord Region, even in diving depths. As to quantify the basic physiological parameter ‘respiration’, specimens of the whole size range were collected at two stations and acclimatised to in vitro condition. Oxygen microoptodes (based on the dynamic fluorescence quenching principle), a four channel optode array, an intermittent flow system, and online data registration were used to measure the metabolic activity of Caryophyllia huinayensis during in vitro respiration experiments. This species showed oxygen consumption rates, ranging from 0.01mg/l up to 1.61mg/l. The overall metabolic rates are compared with those of other scleractinian corals.

Description: The energy budget is one key to the understanding of an ecosystem and may be determined by its carbon fluxes. The aim of the study was and still is to quantify the carbon flux between newly established arctic hard bottom communities and their pelagial in-situ. A complex setup was constructed to establish a functional in-situ method for hard bottom communities. We used artificial panels, installed in arctic Kongsfjorden at 20 m depth. The panels were colonized by hard bottom organisms over the last decade. These panels were transferred in-situ into benthic chambers. The latter were connected via Tygon-tubes to a multiprobe array (CTD, Seabird 19 V2 plus) allowing measurement of O2-concentrations. A newly designed 16-way valve was used to measure several panels over a period of 72 h in a day and night rhythm.

Description: The cold-water hydrocoral Errina antarctica provides habitat for numerous macroepibenthic species. Gaining knowledge about the highly diverse communities associated with E. antarctica is crucial for efficient protection of the ecosystems, which are strongly threatened by aquaculture and other human activities. This investigation for the first time provides information on quantitative composition of benthic communities associated with E. antarctica. Structure of macroepibenthic community associated with E. antarctica in three bathymetric zones (Zone 1: 10-20 m; Zone 2: 20-30 m; Zone 3: 30-40 m) from four diving sites in the Chilean fjord region is described by analyzing 260 images extracted from videos recorded via ROV. Community compositions were investigated based on abundances using multivariate statistical methods (SIMPER, ANOSIM, MDS). Ecological indices (S, H´, d, J´) were calculated. Distribution of differently sized E. antarctica-colonies (small [diameter 〈 10 cm], medium [10 cm 〈 diameter 〈 20 cm], large [20 cm 〈 diameter]) was investigated and set into context with analysis of community structure. No significant influence of depth on the investigated community was detected. Differences between the four diving sites seem to overlay bathymetric effects. Annelids (mainly genus spirorbis) dominate all bathymetric zones, in line with former investigations. ANOSIM indicated poor distinctness between bathymetric zones (GR=0.062). The MDS-plot showed no grouping of bathymetric zones. Low values of ecological indices in Zone 1 are explained by distribution of E. antarctica-colonies. Abundances of colonies of all sizes decreases with depth, portion of small colonies is highest in Zone 1.

Description: To understand mineral transport pathways for shell secretion and to assess differences in cellular activity during mineralization, we imaged with TEM and FE-SEM ultrastructural characteristics of outer mantle epithelium (OME) cells. Imaging was carried out on Magellania venosa shells embedded/etched, chemically fixed/decalcified and high-pressure frozen/freeze-substituted samples from the commissure, central shell portions and from puncta. Imaging results are complemented with morphometric evaluations of volume fractions of membrane-bound organelles. At the commissure the OME consists of several layers of cells. These cells form oblique extensions that, incross-section, are round below the primary layer and flat underneath fibres. At the commissure the OME is multi-cell layered, in central shell regions it is single-cell layered. When actively secreting shell carbonate extrapallial space is lacking, because OME cells are in direct contact with the calcite of the forming fibres. Upon termination of secretion, OME cells attach via apical hemidesmosomes to extracellular matrix membranes that line the proximal surface of fibres. At the commissure volume fractions for vesicles, mitochondria and lysosomes are higher relative to single-cell layered regions, whereas for endoplasmic-reticulum and Golgi apparatus there is no difference. FE-SEM, TEM imaging reveals the lack of extrapallial space between OME cells and developing fibres. In addition, there is no indication for an amorphous precursor within fibres when these are in active secretion mode. Accordingly, our results do not support transport of minerals by vesicles from cells to sites of miner-alization, rather by transfer of carbonate ions via transport mechanisms associated with OME cell membranes.