Description: We analysed carbon (δ13C) and nitrogen (δ15N) isotope ratios of organisms and biogenic tissues from Comau Fjord (southern Chile) to characterise benthic food webs and spatial isotope variability in this ecosystem. These values were intended to serve as a baseline for detecting anthropogenic impacts on Patagonian marine fjord ecosystems in later studies. Benthic macro algae and invertebrate suspension feeders were primarily considered, with some supplementary data from cyanobacteria, plankton, fish, and coastal vertebrates. Six depth transects typified the lateral salinity gradients from the innermost part of the fjord to its mouth, as well as the vertical density gradients caused by freshwater inflow. Carbon isotope signatures indicated predominant consumption of either CO2 or HCO3– for benthic macroalgal. All CO2 users belonged to rhodophytes. The δ15N values of benthic macrophytes decreased with decreasing salinity, both vertically and along the fjord axis. This implies the influence of 15N-poor terrestrial dissolved inorganic nitrogen (DIN) at these sites. Enhanced influence of freshwater influx also lowered N contents and increased C/N ratios in algal tissues. Exceptionally high macroalgae δ15N values at the seabird and sealion colony Isla Liliguapi point to animal faeces as an additional source of 15N-enriched DIN. Thus, DIN sources not originating from the open sea are additionally utilised by the benthic macroalgae in the fjord. In contrast, mussel tissue from the same locations was much less influenced by varying DIN sources. Among benthic suspension feeders, mytilids (Mytilus chilensis, Aulacomya ater) had the lowest and scleractinian corals (Desmophyllum dianthus) had the highest δ15N values, and Balanidae (Elminius kingii) and gorgonians (Primnoella sp.) showed values in between. The preference for specific size classes of marine particulate organic matter (seston) as food serves as an explanation for the δ15N variability observed between the different benthic suspension feeders.

Description: It has been hypothesized that endolithic photo- autotrophs inside the skeleton of cold-water corals may have a mutualistic relationship with the coral host posi- tively affecting coral calcification. This study investigated the effect of endolithic photo-autotrophs on the apical septal extension of the cold-water coral Desmophyllum dianthus at Fjord Comau, southern Chile (42.41°–42.15°S, 72.5°W). The fluorescent staining agent calcein was used to document the linear apical extension of septae for a period of one and a half years between 2006 and 2007. The results showed a severe reduction in extension rates asso- ciated with the presence of endolithic photo-autotrophs. Infested individuals grew about half as fast as non-infested polyps with a median value of 1.18 lm day-1 compared to 2.76 lm day-1. Contrary to the initial hypothesis, these results point toward a parasitic relationship between D. dianthus and its endolithic photo-autotrophs potentially impairing coral fitness. However, further data on physio- logical parameters and other aspects of the calcification process are necessary to confirm these findings.

Description: In Patagonia, Chile, an extensive Fjord system can be found. The Comau Fjord is located in the northern part and is characterized by steep walls, a high tidal range and is approximately 500 m deep. Along its course from mouth to head (horizontally, along isobaths) and with decreasing depth (vertically) it shows gradual changes in water parameters including pH and the associated carbonate chemistry. Desmophyllum dianthus is a cosmopolite coral usually found in deeper water (〉 200 m). In the Comau Fjord it thrives in shallow depth up to 15 m and is distributed in a broad variety of water parameters, including a pH range of at least 0.5 units – likely more. This demonstrates the high adaptation ability of cold water corals to a relatively wide spectrum of pH values.

Description: In Patagonia, Chile, an extensive Fjord system can be found. The Comau Fjord is located in the northern part and is characterized by steep walls, a high tidal range and is approximately 500 m deep. Along its course from mouth to head (horizontally, along isobaths) and with decreasing depth (vertically) it shows gradual changes in water parameters including pH and the associated carbonate chemistry. Desmophyllum dianthus is a cosmopolite coral usually found in deeper water (〉 200 m). In the Comau Fjord it thrives in shallow depth up to 15 m and is distributed in a broad variety of water parameters, including a pH range of at least 0.5 units – likely more. This demonstrates the high adaptation ability of cold water corals to a relatively wide spectrum of pH values.

Description: Increasing dissolution of anthropogenic-released carbon dioxide into the world’s oceans is causing ocean acidification (OA). OA is thought to negatively affect most marine-calcifying organisms, notably cold-water corals (CWC), which may be especially sensitive due to the deep and cold waters they normally thrive in. However, the impact of OA on CWC is difficult to predict. Recorded distributions of CWC are rarely linked to in situ water chemistry, and the boundaries of their distributions are not clearly defined. The fjord Comau in Chilean Patagonia features pronounced pH gradients, and up to 0.5 pH units have been recorded both vertically (at some sites within 50 m depth) and less distinct horizontally (from head to mouth). The cosmopolite coral Desmophyllum dianthus grows along the course of the fjord and of the entire pH range. It occurs in shallow depths (below 12 m, pH 8.1) as part of a deep-water emergence community, but also in 225 m depth at a pH of 7.4. Based on pH and totalalkalinity, data calculations of the associated carbonate chemistry revealed that this CWC thrives commonly close the aragonite (the orthogonal crystal form of calcium carbonate, the mineral structure of coral skeletons) saturation horizon and even below. This suggests a high adaptation potential of D. dianthus to adjust its calcification performance to conditions thermodynamically unfavourable for the precipitation of aragonite.

Description: Fiordo Comau in Northern Patagonia, Chile, is home to a wide range of unique habitats and diverse communities of many new and little understood species. At one site in the fiordo, XHuinay, H2S seeps allow for the formation of filamentous chemosynthetic bacteria mats. Here, two scleractinians, Desmophyllum dianthus and Caryophyllia huinayensis, were once abundant on hard substrate below 18m depth. However, a recent mass mortality of D. dianthus occurred while C. huinayensis continues to survive. This pilot study investigates whether the presence of H2S seeps and their associated bacteria have an affect on D. dianthus mortality. We fixed nine D. dianthus individuals and nine C. huinayensis individuals at 25m depth at two sites: XHuinay and Isla Lilihuapi (control) to monitor their survival under actual conditions. If H2S seeps negatively affect Desmophyllum dianthus survival, then we expect to observe deaths of individuals of D. dianthus at XHuinay and the survival of individuals at Isla Lilihuapi. We also expect C. huinayensis to survive at both sites. This experiment is still in progress. However, this preliminary study emphasizes the need for and seeks to prompt further investigation into these scleractinians, their relationship with both biotic and abiotic environmental factors, and specifically their role within the fragile web of Chilean Fiord ecology.

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 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: Fiordo Comau in Northern Patagonia, Chile, is home to a wide range of unique habitats and diverse communities of many new and little understood species. At one site in the fiordo, XHuinay, H2S seeps allow for the formation of filamentous chemosynthetic bacteria mats. Here, two scleractinians, Desmophyllum dianthus and Caryophyllia huinayensis, were once abundant on hard substrate below 18m depth. However, a recent mass mortality of D. dianthus occurred while C. huinayensis continues to survive. This pilot study investigates whether the presence of H2S seeps and their associated bacteria have an affect on D. dianthus mortality. We fixed nine D. dianthus individuals and nine C. huinayensis individuals at 25m depth at two sites: XHuinay and Isla Lilihuapi (control) to monitor their survival under actual conditions. If H2S seeps negatively affect Desmophyllum dianthus survival, then we expect to observe deaths of individuals of D. dianthus at XHuinay and the survival of individuals at Isla Lilihuapi. We also expect C. huinayensis to survive at both sites. This experiment is still in progress. However, this preliminary study emphasizes the need for and seeks to prompt further investigation into these scleractinians, their relationship with both biotic and abiotic environmental factors, and specifically their role within the fragile web of Chilean Fiord ecology. El fiordo Comau, en la Patagonia Norte de Chile, da hogar a una gran variedad de hábitats singulares y comunidades diversas de muchas especies nuevas y poco entendidas. En un sitio en el fiordo (X-Huinay) filtraciones de H2S permiten la formación de bacterias quimiosintéticas que crean esteras filamentosas. En este sitio abundaban antes dos escleractinios, Desmophyllum dianthus y Caryophyllia huinayensis, en el sustrato duro abajo de una profundidad de 18m. Sin embargo, una mortalidad masiva de D. dianthus fue detectada recientemente, mientras que C. huinayensis continúa sobreviviendo en este sitio. Este estudio piloto investiga si la presencia de las filtraciones de H2S y las bacterias asociadas están conectadas a la mortalidad de D. dianthus. Nueve individuos de D. dianthus y nueve individuos de C. huinayensis fueron fijados a una profundidad de 25m mediante buceo autónomo en dos sitios: X-Huinay e Isla Lilihuapi (control) para monitorear su supervivencia en condiciones reales. Si las filtraciones de H2S afectan negativamente la supervivencia de D. dianthus, esperamos observar la muerte de individuos de esta especie en X-Huinay pero no en Isla Lilihuapi. Además la expectativa es que no haya mortalidad significativa de C. huinayensis en ninguno de los sitios. Este experimento preliminar aún está en curso, sin embargo hace hincapié en la necesidad de mayores investigaciones de estos escleractinios, sus relaciones con factores ambientales bióticos y abióticos, y específicamente su nicho dentro de la frágil red ecológica de los fiordos chilenos.