Life cycle of the cold-water coral Caryophyllia huinayensis.

Little is known about the biology of cold-water corals (CWCs), let alone the reproduction and early life stages of these important deep-sea foundation species. Through a three-year aquarium experiment, we described the reproductive mode, larval release periodicity, planktonic stage, larval histology, metamorphosis and post-larval development of the solitary scleractinian CWC Caryophyllia (Caryophyllia) huinayensis collected in Comau Fjord, Chilean Patagonia. We found that C. huinayensis is a brooder releasing 78.4 ± 65.9 (mean ± standard deviation [SD]) planula larvae throughout the year, a possible adaptation to low seasonality. Planulae had a length of 905 ± 114 µm and showed a well-developed gastrovascular system. After 8 ± 9.3 days (d), the larvae settled, underwent metamorphosis and developed the first set of tentacles after 2 ± 1.5 d. Skeletogenesis, zooplankton feeding and initiation of the fourth set of tentacles started 5 ± 2.1 d later, 21 ± 12.9 d, and 895 ± 45.9 d after settlement, respectively. Our study shows that the ontogenetic timing of C. huinayensis is comparable to that of some tropical corals, despite lacking zooxanthellae.

Environmental stability and phenotypic plasticity benefit the cold-water coral Desmophyllum dianthus in an acidified fjord.

The stratified Chilean Comau Fjord sustains a dense population of the cold-water coral (CWC) Desmophyllum dianthus in aragonite supersaturated shallow and aragonite undersaturated deep water. This provides a rare opportunity to evaluate CWC fitness trade-offs in response to physico-chemical drivers and their variability. Here, we combined year-long reciprocal transplantation experiments along natural oceanographic gradients with an in situ assessment of CWC fitness. Following transplantation, corals acclimated fast to the novel environment with no discernible difference between native and novel (i.e. cross-transplanted) corals, demonstrating high phenotypic plasticity. Surprisingly, corals exposed to lowest aragonite saturation (Ωarag < 1) and temperature (T < 12.0 °C), but stable environmental conditions, at the deep station grew fastest and expressed the fittest phenotype. We found an inverse relationship between CWC fitness and environmental variability and propose to consider the high frequency fluctuations of abiotic and biotic factors to better predict the future of CWCs in a changing ocean.

The carbon and nitrogen budget of Desmophyllum dianthus-a voracious cold-water coral thriving in an acidified Patagonian fjord.

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 µm), (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.

Stable isotope records of sei whale baleens from Chilean Patagonia as archives for feeding and migration behavior.

Carbon (δ13C) and nitrogen (δ15N) stable isotope variations in baleen plates of sei whales (Balaenoptera borealis) stranded after a mass mortality event in Chilean Patagonia were investigated to assess potential dietary and migratory patterns. Carbon and nitrogen isotope ratios of seven baleens from six individuals were analyzed. The δ13C values ranged from - 19.1 to - 15.9‰ and the δ15N values from 8.7 to 15.4‰. Variations of up to 2.9‰ for δ13C and 5.3‰ for δ15N were observed within one baleen. Carbon and nitrogen isotope records of each baleen were significantly correlated and showed recurring oscillations confirmed by wavelet analyses. Oscillations slightly differed in periodicity indicating variable baleen growth rates between 10.0 and 16.5 cm/year. Food sources of the whales are discussed in terms of available isotope data for potential prey taxa and potential migratory behavior on the basis of latitudinal isotope gradients of particulate organic matter. Cyclicity could be explained by regular migrations of the sei whales from subtropical calving areas to high-latitude foraging grounds. δ15N records of baleens differed between individuals eventually pointing to diverse feeding and migratory preferences among sei whale individuals.

Effects of low pH and feeding on calcification rates of the cold-water coral Desmophyllum dianthus.

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.

All you can eat: the functional response of the cold-water coral Desmophyllum dianthus feeding on krill and copepods.

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.

Largest baleen whale mass mortality during strong El Niño event is likely related to harmful toxic algal bloom.

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.

A new alcyonacean octocoral (Cnidaria, Anthozoa, Octocorallia) from Chilean fjords.

A new species, Swiftia comauensis, is described from Chile. It occurs in shallow waters from 18 to 59 m in the Patagonian fjord region and seems to be endemic to the northern part of the region. The species is characterized by having straggly colonies with sparse branching and long drooping branches, prominent polyp mounds, and long, thin spindles; the colonies are bright orange with pale yellow polyp mounds. A sharp decline in colony abundance was observed between 2003 and 2013, and in January 2014 a proposal was submitted to the IUCN for the addition of this taxon to the Red List of Threatened Species.

Hidden among sea anemones: the first comprehensive phylogenetic reconstruction of the order Actiniaria (Cnidaria, Anthozoa, Hexacorallia) reveals a novel group of hexacorals.

Sea anemones (order Actiniaria) are among the most diverse and successful members of the anthozoan subclass Hexacorallia, occupying benthic marine habitats across all depths and latitudes. Actiniaria comprises approximately 1,200 species of solitary and skeleton-less polyps and lacks any anatomical synapomorphy. Although monophyly is anticipated based on higher-level molecular phylogenies of Cnidaria, to date, monophyly has not been explicitly tested and at least some hypotheses on the diversification of Hexacorallia have suggested that actiniarians are para- or poly-phyletic. Published phylogenies have demonstrated the inadequacy of existing morphological-based classifications within Actiniaria. Superfamilial groups and most families and genera that have been rigorously studied are not monophyletic, indicating conflict with the current hierarchical classification. We test the monophyly of Actiniaria using two nuclear and three mitochondrial genes with multiple analytical methods. These analyses are the first to include representatives of all three currently-recognized suborders within Actiniaria. We do not recover Actiniaria as a monophyletic clade: the deep-sea anemone Boloceroides daphneae, previously included within the infraorder Boloceroidaria, is resolved outside of Actiniaria in several of the analyses. We erect a new genus and family for B. daphneae, and rank this taxon incerti ordinis. Based on our comprehensive phylogeny, we propose a new formal higher-level classification for Actiniaria composed of only two suborders, Anenthemonae and Enthemonae. Suborder Anenthemonae includes actiniarians with a unique arrangement of mesenteries (members of Edwardsiidae and former suborder Endocoelantheae). Suborder Enthemonae includes actiniarians with the typical arrangement of mesenteries for actiniarians (members of former suborders Protantheae, Ptychodacteae, and Nynantheae and subgroups therein). We also erect subgroups within these two newly-erected suborders. Although some relationships among these newly-defined groups are still ambiguous, morphological and molecular results are consistent enough to proceed with a new higher-level classification and to discuss the putative functional and evolutionary significance of several morphological attributes within Actiniaria.

Toward a natural classification: phylogeny of acontiate sea anemones (Cnidaria, Anthozoa, Actiniaria).

Acontia-nematocyst-dense, thread-like extensions of the mesenterial filaments-are the characteristic feature of the actiniarian group Acontiaria. Phylogenetic analyses have shown that acontiate taxa form a clade that also includes some taxa without acontia. We analyse five molecular markers from 85 actiniarians to explore the phylogenetic relationships among families in Acontiaria, including acontiate species assigned to other higher taxa and species without acontia that have been allied to Acontiaria. Based on our results, we redefine the group to accommodate those lineages that have lost acontia, and formalize it as superfamily Metridioidea. Based on stable and well supported clades, we resurrect Phelliidae and Amphianthidae, redefine Kadosactinidae and Actinoscyphiidae, and move two species to new genera: that previously termed Sagartiogeton erythraios belongs in Jasonactis gen. nov.; and that previously termed Anthosactis pearseae belongs in Ostiactis gen. nov., type genus of Ostiactinidae fam. nov. We also synonymized Halcampoididae and Halcampidae (as Halcampidae) and Andvakiidae and Isophelliidae (as Andvakiidae). The results of our phylogenetic analyses indicate that the diagnostic morphological characters used in the family-level taxonomy of acontiate actiniarians such as the nematocysts of the acontia, the marginal sphincter muscle, and mesenteries divisible into macro- and micro-cnemes, have to be revisited, as these features are highly homoplasious.