Beschreibung: Many species of the genus Octopus are important resources for fisheries worldwide. Its approximately 200 species show a strong similarity in structural morphology and a wide diversity in skin coloration and patterning, behaviour and life strategies that have hampered the study of phylogenetic relationships. We used a Bayesian approach to estimate as yet unknown phylogenetic relationships among O. tehuelchus from the southwestern Atlantic, new specimens of O. mimus (Chile and Peru) and other Octopus species, and used Bayes factors to test phylogenetic hypotheses. O. tehuelchus was more closely related to the genera Callistoctopus , Grimpella and Macroctopus than to Octopus , and therefore its generic placement may need a revision. O. vulgaris specimens from Costa Rica (Pacific Ocean) and O. oculifer grouped with O. mimus. Bayes factors showed positive evidence in favor of this grouping and therefore these individuals could have been misidentified, being in fact O. mimus. O. vulgaris specimens from the Costa Rican Caribbean were more related to O. mimus than to other O. vulgaris and could represent a cryptic species. The remaining O. vulgaris clustered with O. tetricus . Bayes factors found strong evidence against the monophyly of O. vulgaris as currently defined, giving statistical support to the monophyly of an O. vulgaris s. str. + O. tetricus group proposed previously by other authors.

Beschreibung: For marine invertebrates living at low temperatures of high latitudes Thorson’s rule suggests a comparatively reduced speed of development. Several studies conducted in different climatic zones have revealed the processes involved in the maturation of benthic assemblages. However, the duration and chronology of succession, as well as the influence of environmental impacts on arctic benthic assemblages is only scarcely analysed. Long-term studies are still rare. By analysing species abundances and substrate coverage over an exposure time of one decade the following hypotheses are tested: (i) Exposition time significantly modifies the structure of arctic benthic hard-bottom assemblages, (ii) the macroscopic structure of the substrate surface has a significant influence on the structure of benthic hard-bottom assemblages, and (iii) the succession of benthic hard-bottom assemblages in the Arctic is in general slower compared to the benthic succession in all non-polar climatic zones. In 2002 forty Polyethylene growth panels were installed on an underwater cliff in Kongsfjorden (Svalbard, Norway) in about 20 m water depth. Six of these were grooved to create structural diversity on the panel surface. Once a year the ripening epibenthic assemblages were photographed by scientific divers. Until 2007 annually about eight panels were sampled and replaced, thus creating starting points for succession in different years. Additionally a ground truthing was carried out for reference. The findings of this study indicate a resilience time exceeding a decade. A strong heterogeneity can be observed between the assemblages on different panels, signifying an influence of different starting points. The results are discussed in comparison with results of related studies from this and other cold-water regions.

Beschreibung: 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.

Beschreibung: In the Arctic, the currently observed rising air temperature results in more frequent calving of icebergs. The latter derive from tidewater glaciers. Arctic macrozoobenthic soft-sediment communities are considerably disturbed by direct hits and sediment reallocation caused by iceberg scouring. With the aim to describe the primary succession of macrozoobenthic communities following these events, scientific divers installed 28 terracotta containers in the soft-sediment off Brandal (Kongsfjorden, Svalbard, Norway) at 20 m water depth in 2002. The containers were filled with a bentonite–sand mixture resembling the natural sediment. Samples were taken annually between 2003 and 2007. A shift from pioneering species (e.g. Cumacea: Lamprops fuscatus) towards more specialised taxa, as well as from surface detritivores towards subsurface detritivores was observed. This is typical for an ecological succession following the facilitation and inhibition succession model. Similarity between experimental and non-manipulated communities from 2003 was significantly highest after 3 years of succession. In the following years, similarity decreased, probably due to elevated temperatures, which prevented the fjord system from freezing. Some organisms, numerically important in the non-manipulated community (e.g. the polychaete Dipolydora quadrilobata) did not colonise the substrate during the experiment. This suggests that the community had not fully matured within the first 3 years. Later, the settlement was probably impeded by consequences of rising temperatures. This demonstrates the long-lasting effects of severe disturbances on Arctic macrozoobenthic communities. Furthermore, environmental changes, such as rising temperatures coupled with enhanced food availability due to an increasing frequency of sea-ice-free days per year, may have a stronger effect on succession than exposure time.

Beschreibung: 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.

Beschreibung: Cold-water corals (CWC) are thought to be especially vulnerable to ocean acidification. However, in situ studies on the response of CWC to low aragonite saturation (Ωar) are still scarce. The Comau Fjord in southern Patagonia (Chile) is naturally stratified with vertical and horizontal pH gradients and high abundances of the cosmopolitan CWC Desmophyllum dianthus at Ωar ≤ 1. Previous studies reveal high growth rates of D. dianthus in summer but it is not known if skeletal growth and the ability of internal pH up-regulation show seasonal fluctuations due to changes in Ωar and/or food supply. In the present study, we compare D. dianthus skeletal carbonate accretion (buoyant weight technique) and linear extension rates (fluorescent microscopy) with the physico-chemical conditions in the water column (T, Ωar) in austral summer 2016/2017 and winter 2017. Corals were sampled at six stations at 20m water depth along the presumed horizontal pH gradient of Comau Fjord.

Beschreibung: Cold-water corals (CWC) were long thought to be particularly sensitive to ocean acidification (OA). However, previous laboratory studies indicate no negative effect of low aragonite saturation (Ωar) on growth rates of CWC while the few in situ studies show the same result. The CWC Desmophyllum dianthus is ubiquitous in Comau Fjord (southern Chile), a small but deep (〉 400 m) semi-enclosed stratified basin with pronounced horizontal and vertical pH gradients. High densities of D. dianthus can be found below the aragonite saturation horizon (Ωar 〈 1) but it is not known so far if seasonal changes in Ωar lead to seasonal differences in growth rates. Corals were sampled along the pH gradients of Comau Fjord (Ωar = 0.65-1.45) and cross-transplanted between stations. Skeletal carbonate accretion (buoyant weighing technique) and calcification rates (alkalinity anomaly technique) were measured in austral summer 2016/2017 and winter 2017 and compared to physico-chemical conditions in the water column (T, Ωar). Higher growth rates were found in summer than in winter. Surprisingly, growth of D. dianthus was highest in undersaturated waters in both seasons (Ωar = 0.65 and 0.83) and cross-transplanted specimens were able to acclimatise to Ωar 〈 1. We conclude that Ωar is a poor predictor of D. dianthus growth and more factors (like plankton food supply) need to be taken into account when investigating the impact of OA on CWC in the future.

Beschreibung: Cold-water corals (CWC) have long been considered particularly sensitive to ocean acidification (OA). However, a number of laboratory studies indicate that exposure to acidic waters does not affect CWC growth but in situ OA studies on CWC are scarce. In the naturally acidified Comau Fjord (Chile), high densities of the cosmopolitan CWC Desmophyllum dianthus are found at or below aragonite saturation (Ωar ≤ 1), but it is not known if the corals’ ability to up-regulate the pH in the calcifying fluid (pHcf) and calcify shows seasonal fluctuations due to changes in Ωar and/or food supply. In the present study, corals were sampled along both horizontal and vertical pH gradients in Comau Fjord (equivalent to 0.81 〈 Ωar 〈 1.45 and 0.65 〈 Ωar 〈 1.45, respectively). We compared D. dianthus’ calcification rates (alkalinity anomaly technique), skeletal carbonate accretion (buoyant weight technique, BWT), linear extension rates (fluorescent microscopy) and pHcf (skeletal δ11B; LA-ICP-MS) with the physico-chemical conditions in the water column (T, Ωar) in austral summer 2016/2017 and winter 2017. Growth rates (BWT) were higher in summer than in winter, with highest values, irritably, at Ωar 〈 1. Cross-transplant experiments showed that D. dianthus is able to acclimatise to Ωar 〈 1. A strong biological pHcf up-regulation of 1.13 pH units was found at low pHT with δ11B of 25.6 ‰ compared to ΔpH of 0.77 (δ11B = 23.4 ‰) at higher pHT. The present study shows that Ωar alone is a poor predictor of D. dianthus’ pH up-regulation and growth. They suggest a complex combination of biological and physical factors that need to be considered to constrain the future of CWC in an era of OA.

Beschreibung: Ascidians are abundant and well-represented members of worldwide benthic communities, including Antarctica and the Arctic. These organisms exhibit different reproductive patterns usually related to a latitudinal gradient, as do many marine invertebrate species. Reproductive seasonality varies from one or two annual peaks in cold and temperate water species to continuous reproduction throughout the year in warm water species. Styela rustica (Linnaeus 1767) and Halocynthia pyriformis (Rathke 1806) are solitary species with external fertilization and a wide distribution range, from the North Atlantic to the Arctic. The reproductive patterns of these two species were assessed for Arctic populations by year-round sampling and structural analysis of the gonads. Both species are hermaphrodites and showed marked seasonality in oocyte maturity and spawning; S. rustica peaked during the boreal summer and H. pyriformis in late spring. The two species also showed marked differences in mature oocyte sizes: H. pyriformis almost doubled those of S. rustica and, while spermatocytes of H. pyriformis were mature year-round, the maturity of male and female gametes was synchronized in S. rustica. The species thus showed an annual reproductive cycle coupled with a higher production period in the ecosystem, but also exhibited different strategies developed under the same environmental pressures.

Beschreibung: Coastal ecosystems are increasingly impacted by man-made disturbances including pollution from agriculture, aquaculture and municipal waste. This study employed multiple ecological indicators to assess environmental quality of the Densu Estuary and understanding of environmental controls on the spatial distribution of organisms. Physicochemical parameters were measured in situ. Water and sediment samples were collected from ten stations and analysed for nutrients, total suspended solids and organisms using standard methods. The water quality index for the Densu Estuary ranged from 359.5 to 484.4, suggesting an unhealthy ecosystem. The abundance of indicator species, e.g. faecal bacteria (Escherichia coli, Enterococcus species) and polychaetes (Capitella and Nereis species) varied significantly (p〈0.05) among stations. Contaminated sites are located landwards with high human impacts. Faecal bacteria and polychaete abundance correlated significantly (p〈0.05) with the respective physicochemical parameters. Canonical analysis (74.11%) showed the physicochemical influence on the spatial distribution of species. The pH significantly (p〈0.05) controlled the spatial distribution of faecal bacteria and polychaetes in the Densu Estuary. The results suggest environmental pollution in the Densu Estuary, useful baseline information for effective legislation towards its sustainable management.