ALBERT

Description: Cold-Water Corals (CWCs), and most marine calcifiers, are especially threatened by ocean acidification (OA) and the decrease in the carbonate saturation state of seawater. The vulnerability of these organisms, however, also involves other global stressors like warming, deoxygenation or changes in sea surface productivity and, hence, food supply via the downward transport of organic matter to the deep ocean. This study examined the response of the CWC Desmophyllum dianthus to low pH under different feeding regimes through a long-term incubation experiment. For this experiment, 152 polyps were incubated at pH 8.1, 7.8, 7.5 and 7.2 and two feeding regimes for 14 months. Mean calcification rates over the entire duration of the experiment ranged between −0.3 and 0.3 mg CaCO3 g−1d−1. Polyps incubated at pH 7.2 were the most affected and 30% mortality was observed in this treatment. In addition, many of the surviving polyps at pH 7.2 showed negative calcification rates indicating that, in the long term, CWCs may have difficulty thriving in such aragonite undersaturated waters. The feeding regime had a significant effect on skeletal growth of corals, with high feeding frequency resulting in more positive and variable calcification rates. This was especially evident in corals reared at pH 7.5 (ΩA = 0.8) compared to the low frequency feeding treatment. Early life-stages, which are essential for the recruitment and maintenance of coral communities and their associated biodiversity, were revealed to be at highest risk. Overall, this study demonstrates the vulnerability of D. dianthus corals to low pH and low food availability. Future projected pH decreases and related changes in zooplankton communities may potentially compromise the viability of CWC populations.

Description: The feeding behavior of the cosmopolitan cold-water coral (CWC) Desmophyllum dianthus (Cnidaria: Scleractinia) is still poorly known. Its usual deep distribution restricts direct observations, and manipulative experiments are so far limited to prey that do not occur in CWC natural habitat. During a series of replicated incubations, we assessed the functional response of this coral feeding on a medium-sized copepod (Calanoides patagoniensis) and a large euphausiid (Euphausia vallentini). Corals showed a Type I functional response, where feeding rate increased linearly with prey abundance, as predicted for a tentaculate passive suspension feeder. No significant differences in feeding were found between prey items, and corals were able to attain a maximum feeding rate of 10.99 mg C h−1, which represents an ingestion of the 11.4% of the coral carbon biomass per hour. These findings suggest that D. dianthus is a generalist zooplankton predator capable of exploiting dense aggregations of zooplankton over a wide prey size-range.

Description: While large mass mortality events (MMEs) are well known for toothed whales, they have been rare in baleen whales due to their less gregarious behavior. Although in most cases the cause of mortality has not been conclusively identified, some baleen whale mortality events have been linked to bio-oceanographic conditions, such as harmful algal blooms (HABs). In Southern Chile, HABs can be triggered by the ocean–atmosphere phenomenon El Niño. The frequency of the strongest El Niño events is increasing due to climate change. In March 2015, by far the largest reported mass mortality of baleen whales took place in a gulf in Southern Chile. Here, we show that the synchronous death of at least 343, primarily sei whales can be attributed to HABs during a building El Niño. Although considered an oceanic species, the sei whales died while feeding near to shore in previously unknown large aggregations. This provides evidence of new feeding grounds for the species. The combination of older and newer remains of whales in the same area indicate that MMEs have occurred more than once in recent years. Large HABs and reports of marine mammal MMEs along the Northeast Pacific coast may indicate similar processes in both hemispheres. Increasing MMEs through HABs may become a serious concern in the conservation of endangered whale species.

Description: The Chilean fjord region, situated between 42 and 56 °S, forms one of the most ragged shorelines and belongs to the ecologically and biogeographically least understood marine regions of the world. A labyrinth of fjords, channels, and islands extends over 240,000 km2 and creates a coastline of more than 80,000 km. Due to strong abiotic gradients, numerous habitats are created, which are further diversified by temporal dynamics (tidal cycle, seasonal changes in precipitation, temperature, radiation, etc.). The region is a biodiversity hotspot hosting unique and fragile ecosystems. Among the species living here, several are species forming habitats in the ecosystem. These organisms can reach high densities conforming the so-called marine animal forests. Examples are marine animal forests dominated by cold-water stony corals, gorgonians, hydrocorals, brachiopods, polychaetes, giant barnacles, sponges, and ascidians. Many of these communities have been discov- ered only recently. There is also a singular characteristic in this area: exceptionally low pH levels of the waters of Patagonian fjords provide the opportunity to study calcifying organisms in an environment with pH conditions in the same range as the ones predicted by the IPCC for the world oceans in 2100. Despite the scarce ecological and biogeographical knowledge of this area, it encounters an unparalleled economic development including high-impact industry-scale salmonid farming, ambitious infrastructure and industrialization projects, and increasing extractive activities. Baseline research on the abiotic and biotic environment of the region is needed to reach sustainability in the use of the marine resources. Management plans including the establishment of marine protected areas to preserve benthic diversity and ecosystem services are urgently needed.

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.

Description: In the North Patagonian fjord region, the cold-water coral (CWC) Desmophyllum dianthus occurs in high densities, in spite of low pH and aragonite saturation. If and how these conditions affect the energy demand of the corals is so far unknown. In a laboratory experiment, we investigated the carbon and nitrogen (C, N) budget of D. dianthus from Comau Fjord under three feeding scenarios: (1) live fjord zooplankton (100 2,300 mm), (2) live fjord zooplankton plus krill (〉7 mm), and (3) four-day food deprivation. In closed incubations, C and N budgets were derived from the difference between C and N uptake during feeding and subsequent C and N loss through respiration, ammonium excretion, release of particulate organic carbon and nitrogen (POC, PON). Additional feeding with krill significantly increased coral respiration (35%), excretion (131%), and POC release (67%) compared to feeding on zooplankton only. Nevertheless, the higher C and N losses were overcompensated by the threefold higher C and N uptake, indicating a high assimilation and growth efficiency for the krill plus zooplankton diet. In contrast, short food deprivation caused a substantial reduction in respiration (59%), excretion (54%), release of POC (73%) and PON (87%) compared to feeding on zooplankton, suggesting a high potential to acclimatize to food scarcity (e.g., in winter). Notwithstanding, unfed corals `lost' 2% of their tissue-C and 1.2% of their tissue-N per day in terms of metabolism and released particulate organic matter (likely mucus). To balance the C (N) losses, each D. dianthus polyp has to consume around 700 (400) zooplankters per day. The capture of a single, large krill individual, however, provides enough C and N to compensate daily C and N losses and grow tissue reserves, suggesting that krill plays an important nutritional role for the fjord corals. Efficient krill and zooplankton capture, as well as dietary and metabolic flexibility, may enable D. dianthus to thrive under adverse environmental conditions in its fjord habitat; however, it is not known how combined anthropogenic warming, acidification and eutrophication jeopardize the energy balance of this important habitat-building species.

Description: The fibrous calcite layer of modern brachiopod shells is a hybrid composite material and forms a substantial part of the hard tissue. We investigated how cells of the outer mantle epithelium (OME) secrete calcite material and generate the characteristic fibre morphology and composite microstructure of the shell. We employed AFM, FE-SEM, and TEM imaging of embedded/etched, chemically fixed/decalcified and high-pressure frozen/freeze substituted samples. Calcite fibres are secreted by outer mantle epithelium (OME) cells. Biometric analysis of TEM micrographs indicates that about 50% of these cells are attached via hemidesmosomes to an extracellular organic membrane present at the proximal, convex surface of the fibres. At these sites, mineral secretion is not active. Instead, ion transport from OME cells to developing fibres occurs at regions of closest contact between cells and fibres, however only at sites where the extracellular membrane at the proximal fibre surface is not developed yet. Fibre formation requires the cooperation of several adjacent OME cells. It is a spatially and temporally changing process comprising of detachment of OME cells from the extracellular organic membrane, mineral secretion at detachment sites, termination of secretion with formation of the extracellular organic membrane, and attachment of cells via hemidesmosomes to this membrane.