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Rocky benthic communities are common in Antarctic coastal habitats; yet little is known about their carbon turnover rates. Here, we performed a broad survey of shallow ( < 65 m depth) rocky ice-scoured habitats of South Bay (Doumer Island, Western Antarctic Peninsula), combining (i) biodiversity assessments from benthic imaging, and (ii) in situ benthic dissolved oxygen (O2) exchange rates quantified by the aquatic eddy covariance technique. The 18 study sites revealed a gradual transition from macroalgae and coralline-dominated communities at ice-impacted depths (15–25 m; zone I) to large suspension feeders (e.g., sponges, bivalves) at depth zone II (25–40 m) and extensive suspension feeders at the deepest study location (zone III; 40–65 m). Gross primary production (GPP) in zone I was up to 70 mmol O2 m−2 d−1 and dark ecosystem respiration (ER) ranged from 15 to 90 mmol m−2 d−1. Zone II exhibited reduced GPP (average 1.1 mmol m−2 d−1) and ER rates from 6 to 36 mmol m−2 d−1, whereas aphotic zone III exhibited ER between 1 and 6 mmol m−2 d−1. Benthic ER exceeded GPP at all study sites, with daily net ecosystem metabolism (NEM) ranging from − 22 mmol m−2 d−1 at the shallow sites to − 4 mmol m−2 d−1 at 60 m. Similar NEM dynamics have been observed for hard-substrate Arctic habitats at comparable depths. Despite relatively high GPP during summer, coastal rocky habitats appear net heterotrophic. This is likely due to active drawdown of organic material by suspension-feeding communities that are key for biogeochemical and ecological functioning of high-latitude coastal ecosystems.

Made available in DSpace on 2019-09-12T16:53:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2017 Ministério do Meio Ambiente (MMA) Ministério da Ciência, Tecnologia e Inovação (MCTI) Secretaria da Comissão Interministerial para os Recursos do Mar (SECIRM) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) The gastropod Nacella concinna is the most conspicuous macroinvertebrate of the intertidal zone of the Antarctic Peninsula and adjacent islands. Naturally high levels of copper and cadmium in coastal marine ecosystems are accumulated in N. concinna tissues. We aimed to study the effects of metal cations on N. concinna arginase in the context of possible adaptive microevolution. Gills and muscle had the highest argininolytic activity, which was concentrated in the cytosol in both tissues. Gills had the highest levels of arginase and may be involved in the systemic control of L-arginine levels. The relatively high argininolytic activity of the N. concinna muscular foot, with K-M = 25.3 +/- 3.4 mmol L-1, may be involved in the control of L-arginine levels during phosphagen breakdown. N. concinna arginases showed the following preferences for metal cations: Ni2+ > Mn2+ > Co2+ > Cu2+ in muscle and Mn2+ > Cu2+ in gills. Cu2+ activation is a unique characteristic of N. concinna arginases, as copper is a potent arginase inhibitor. Cu2+ partly neutralized N. concinna arginase inhibition by Cd2+, worked synergistically in muscle arginase activation by Co2+ and neutralized muscle arginase activation by Ni2+. Mn2+ was able to activate muscle arginase in the presence of Fe3+ and Pb2+. The selection of arginases that are activated by Cu2+ and resistant to inhibition by Cd2+ in the presence of Cu2+ over evolutionary timescales may have favored N. concinna occupation of copper- and cadmium-rich niches. (C) 2016 Elsevier Inc. All rights reserved. [de Oliveira, Mariana Feijo; Rodrigues Junior, Edson; Kawagoe Suda, Cecilia Nahomi; Vani, Gannabathula Sree; Rodrigues, Edson] Universidade de Taubaté (Unitau), Basic Biosci Inst [Donatti, Lucelia] Univ Fed Parana, Dept Cell Biol, Curitiba, Parana, Brazil [Lavrado, Helena Passeri] Univ Fed Rio de Janeiro, Dept Marine Biol, Rio De Janeiro, Brazil

Food web analyses are powerful tools to understand the structure, dynamics and stability of communities. Potter Cove (25 de Mayo/King George Island) is one of the most biodiverse and studied fjords on the West Antarctic Peninsula (WAP), where climate change is affecting benthic and pelagic communities. This fjord ecosystem presents a considerable degree of environmental and species distribution heterogeneity across space: the outer portion of the cove is dominated by hard bottoms meanwhile the inner portion is dominated by soft bottoms. In this work, we have incorporated habitat type to a highly-resolved Antarctic food web, and evaluated its effects on different network metrics and proxies for various dimensions of stability. We considered a multidimensional perspective and employed simulation techniques to encompass variability. Our results showed that the incorporation of habitat type to Potter Cove food web analysis led to two different functional types of networks segregated on space: a green food web (in the outer cove) and a brown food web (in the inner cove). The green and the brown food webs showed significant differences in network structure and in some proxies for multidimensional stability (i.e. quasi sign-stability and omnivory), suggesting that these two food webs have different resilience to perturbations. However, there were no changes in network robustness when in silico experiments were performed. We conclude that habitat type plays a significant role in the structure and stability of Antarctic food webs, and should be taken into account to design effective conservation strategies.

Made available in DSpace on 2019-09-12T16:53:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2015 Instituto Nacional de Ciência e Tecnologia Antártico de Pesquisas Ambientais (INCT-APA) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) Physiological studies suggest that Antarctic marine organisms are adversely affected by rising global temperatures and ocean acidification and have poor prospects for survival. However, according to ecological studies, their vulnerability might be less severe than initially thought. Thus, a realistic forecast of species survival and Antarctic biodiversity should be based on studies from a variety of species under consideration of ecological factors. The limpet Nacella concinna is often found in the rocky intertidal and sublittoral zones of the Antarctic Peninsula and adjacent subantarctic islands. This review summarizes most of the available information on the biology of this limpet, one of the most conspicuous invertebrates of the intertidal zone. There is some evidence that adult N. concinna are physiologically flexible and can acclimate to 3 A degrees C. However, the requirements of the larval stage are poorly known, thus precluding realistic predictions of how elevated temperatures will affect N. concinna populations. Data on physiological performance (righting ability, tenacity and radula rasping rate) under different temperatures could provide a useful baseline for further field investigations on the effects of warming. The species could be used as model organism for investigating the biological effects of ongoing global warming on slow-growing Antarctic ectotherms. Nacella concinna might also be a better biomonitor for polycyclic aromatic hydrocarbons than other Antarctic mollusks. [Suda, Cecilia N. K.; Vani, Gannabathula S.; de Oliveira, Mariana Feijo; Rodrigues, Edson, Jr.; Rodrigues, Edson; Lavrado, Helena P.] Univ Fed Rio de Janeiro, Natl Inst Sci & Technol Antarctic Environm Res IN, Headquarters, BR-21941902 Rio De Janeiro, RJ, Brazil [Suda, Cecilia N. K.; Vani, Gannabathula S.; de Oliveira, Mariana Feijo; Rodrigues, Edson] Universidade de Taubaté (Unitau), Basic Biosci Inst, BR-12030180 Taubate, SP, Brazil [de Oliveira, Mariana Feijo; Rodrigues, Edson, Jr.] Univ Fed Parana, Dept Cell Biol, BR-81990970 Curitiba, Parana, Brazil [Lavrado, Helena P.] Univ Fed Rio de Janeiro, Dept Marine Biol, BR-21941902 Rio De Janeiro, RJ, Brazil

Made available in DSpace on 2019-09-12T16:53:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2015 Ministério do Meio Ambiente (MMA) Ministério da Ciência, Tecnologia e Inovação (MCTI) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Secretariat of the Inter-ministerial Commission for the Resources of the Sea (SeCIRM) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) Instituto Nacional de Ciência e Tecnologia Antártico de Pesquisas Ambientais (INCT-APA) The intertidal and subtidal environments in the Antarctic Peninsula are vulnerable to pollutants, such as diesel oil, a commonly used fuel. Nacelle concinna is capable of accumulating polycyclic aromatic hydrocarbons and is a potential biomonitor of diesel oil contamination. This work investigates the interaction of diesel oil, temperature and salinity on the activity of antioxidants enzymes defense of the gills, foot muscle and digestive glands. Upregulation of superoxide dismutase occurred in the three tissues by warming. The foot muscle catalase and the gill glutathione reductase were upregulated only by diesel. The inability to upregulate catalase and glutathione S-transferase in the digestive gland, as well as the increase of lipoperoxidation, suggested that this gland is more susceptible to the deleterious effects from oxidative stress. (C) 2015 Elsevier Ltd. All rights reserved. [de Oliveira, Mariana Feijo; Rodrigues Junior, Edson; Donatti, Lucelia] Univ Fed Parana, Dept Cell Biol, BR-81530130 Curitiba, Parana, Brazil [de Oliveira, Mariana Feijo; Rodrigues Junior, Edson; Suda, Cecilia N. K.; Vani, Gannabathula S.; Rodrigues, Edson] Universidade de Taubaté (Unitau), Basic Biosci Inst, BR-12030180 Taubate, SP, Brazil [Lavrado, Helena P.] Univ Fed Rio de Janeiro, Dept Marine Biol, BR-21941902 Rio De Janeiro, RJ, Brazil

Made available in DSpace on 2019-09-12T16:53:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2015 Ministério do Meio Ambiente (MMA) Ministério da Ciência, Tecnologia e Inovação (MCTI) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Secretariat of the Inter-ministerial Commission for the Resources of the Sea (SeCIRM) Instituto Nacional de Ciência e Tecnologia Antártico de Pesquisas Ambientais (INCT-APA) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) The present study aimed to assess the sewage effects of the Brazilian Antarctic Station Comandante Ferraz, Admiralty Bay, King George Island, on the hepatic metabolism (energetic, antioxidant, and arginase levels) and levels of plasma constituents of two Antarctic fish species Notothenia rossii and N. coriiceps. The bioassays were conducted under controlled temperature (0 degrees C) and salinity (35 psu), exposing the fish for 96 h, to sewage effluent diluted in seawater to 0.5 % (v/v). Liver homogenates were tested for the specific activities of the enzymes glucose-6-phosphatase (G6Pase), glycogen phosphorylase (GPase), hexokinase, citrate synthase, lactate dehydrogenase, malate dehydrogenase, glucose-6-phosphate dehydrogenase, superoxide dismutase, glutathione reductase, catalase, and arginase. Plasma levels of glucose, triacylglycerides, cholesterol, total protein, albumin, chloride, magnesium, calcium, and inorganic phosphate were also determined. In N. rossii, the decrease in citrate synthase and the increase in G6Pase and GPase suggested that the sewage effluent activated glycogenolysis and hepatic gluconeogenesis, whereas is N. coriiceps, only G6Pase levels were increased. In N. rossii, sewage effluent induced hypertriglyceridemia without modulating glucose plasma levels, in contrast to N. coriiceps, which developed hypoglycemia without elevating plasma triglyceride levels. The decrease in glutathione reductase levels in N. coriiceps and in superoxide dismutase and catalase in N. rossii suggest that these two species are susceptible to oxidative stress stemming from the production of reactive oxygen species. An increase in magnesium in N. rossii and a decrease in N. coriiceps showed that sewage effluent compromised the control of plasma levels of this cation. Although phylogenetically close, both species of Antarctic fish exhibited different metabolic responses to the sewage effluent, with N. coriiceps showing greater susceptibility to the toxic effects of the pollutants. The present study suggests that the biochemical responses of these two species are potential indicators of metabolic changes caused by sewage effluents. [Rodrigues, Edson, Jr.; Feijo-Oliveira, Mariana; Kawagoe Suda, Cecilia Nohome; Vani, Gannabathula Sree; Rodrigues, Edson] Universidade de Taubaté (Unitau), Inst Basic Biosci, BR-12030180 Taubate, SP, Brazil [Donatti, Lucelia] Univ Fed Parana, Dept Cell Biol, BR-81530130 Curitiba, PR, Brazil [Lavrado, Helena Passeri] Univ Fed Rio de Janeiro, Dept Marine Biol, BR-21941902 Rio De Janeiro, RJ, Brazil

The western Antarctic Peninsula is experiencing strong environmental changes as a consequence of ongoing regional warming. Glaciers in the area are retreating rapidly and increased sediment-laden meltwater runoff threatens the benthic biodiversity at shallow depths. We identified three sites with a distinct glacier-retreat related history and different levels of glacial influence in the inner part of Potter Cove (King George Island, South Shetland Islands), a fjord-like embayment impacted since the 1950s by a tidewater glacier retreat. We compared the soft sediment meio- and macrofauna isotopic niche widths (d13C and d15N stable isotope analysis) at the three sites to investigate possible glacier retreat-related influences on benthic trophic interactions. The isotopic niches were locally shaped by the different degrees of glacier retreat-related disturbance within the Cove. Wider isotopic niche widths were found at the site that has become ice-free most recently, and narrower niches at the older ice-free sites. At an intermediate state of glacier retreat-related disturbance (e.g. via ice-growler scouring) species with different strategies could settle. The site at the earliest stage of post-retreat development was characterized by an assemblage with lower trophic redundancy. Generally, the isotopic niche widths increased with increasing size spectra of organisms within the community, excepting the youngest assemblage, where the pioneer colonizer meiofauna size class displayed the highest isotopic niche width. Meiofauna at all sites generally occupied positions in the isotopic space that suggested a detrital-pool food source and/or the presence of predatory taxa. In general ice scour and glacial impact appeared to play a two-fold role within the Cove: i) either stimulating trophic diversity by allowing continuous re-colonization of meiofaunal species or, ii) over time driving the benthic assemblages into a more compact trophic structure with increased connectedness and resource recycling.