Metabolic rates and carbon budget of early developmental stages of the marine cyclopoid copepod Oithona davisae

12 pages, 6 figures, 3 tablesThe genus Oithona has been considered the most abundant and ubiquitous copepod in the world’s oceans. However, despite its importance, the metabolism of its developmental stages (nauplii and copepodites), crucial to explain their evolutionary success, is almost unknown. We determined respiration rates, ammonium and phosphate excretion rates, and the net growth efficiencies of early developmental stages of Oithona davisae as related to stage, body weight, temperature, and food availability. Respiration and excretion rates increased with increasing body weight and were positively related to temperature and food. Specific respiration rates of nauplii and copepodites varied from 0.11 to 0.55 d-1 depending on stage, body weight, temperature, and food availability. Metabolic C:N ratios were higher than 14, indicating lipid-oriented metabolism. Assimilation efficiencies and net growth efficiencies ranged from 65% to 86% and from 23% to 32%, respectively, depending on body weight, stage, and temperature. Assimilation efficiencies and net growth efficiencies estimated using the respiration rates of nauplii with food were 1.7 times higher and 0.6 times lower, respectively, than those calculated using respiration rates of nauplii without food. Therefore, the use of respiration rates measured in filtered seawater led to substantial bias on the estimations of zooplankton carbon budget. O. davisae developmental stages exhibited similar assimilation and growth efficiencies but lower carbon-specific respiratory losses than calanoid copepods. Hence, the low metabolic costs of Oithona compared with calanoids may be one reason for their success in marine ecosystemsThis work was funded by the Spanish Ministry of Science and Innovation (MICINN) through a Ph.D. fellowship to R.A. (BES-2005-7491) and the research projects CTM2004-02775 and Intramural-200630I226 to A.C., CTM2007-60052 to E.S., and CTM2006-12344 to M.A.Peer reviewe

Interactions between Zooplankton and Crude Oil: Toxic Effects and Bioaccumulation of Polycyclic Aromatic Hydrocarbons

We conducted ship-, shore- and laboratory-based crude oil exposure experiments to investigate (1) the effects of crude oil (Louisiana light sweet oil) on survival and bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) in mesozooplankton communities, (2) the lethal effects of dispersant (Corexit 9500A) and dispersant-treated oil on mesozooplankton, (3) the influence of UVB radiation/sunlight exposure on the toxicity of dispersed crude oil to mesozooplankton, and (4) the role of marine protozoans on the sublethal effects of crude oil and in the bioaccumulation of PAHs in the copepod Acartia tonsa. Mortality of mesozooplankton increased with increasing oil concentration following a sigmoid model with a median lethal concentration of 32.4 ml L21 in 16 h. At the ratio of dispersant to oil commonly used in the treatment of oil spills (i.e. 1:20), dispersant (0.25 ml L21 ) and dispersant- treated oil were 2.3 and 3.4 times more toxic, respectively, than crude oil alone (5 ml L21 ) to mesozooplankton. UVB radiation increased the lethal effects of dispersed crude oil in mesozooplankton communities by 35%. We observed selective bioaccumulation of five PAHs, fluoranthene, phenanthrene, pyrene, chrysene and benzo[b]fluoranthene in both mesozooplankton communities and in the copepod A. tonsa. The presence of the protozoan Oxyrrhis marina reduced sublethal effects of oil on A. tonsa and was related to lower accumulations of PAHs in tissues and fecal pellets, suggesting that protozoa may be important in mitigating the harmful effects of crude oil exposure in copepods and the transfer of PAHs to higher trophic levels. Overall, our results indicate that the negative impact of oil spills on mesozooplankton may be increased by the use of chemical dispersant and UV radiation, but attenuated by crude oil-microbial food webs interactions, and that both mesozooplankton and protozoans may play an important role in fate of PAHs in marine environments.Zoe Wambaugh was supported by the National Science Foundation (NSF) Research Experiences for Undergraduates (REU) program (grant OCE- 1062745). This research was made possible by a grant from BP/The Gulf of Mexico Research Initiative through the University of Texas Marine Science Institute (DROPPS consortium: ‘Dispersion Research on Oil: Physics and Plankton Studies’). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Marine Scienc

How much crude oil can zooplankton ingest? Estimating the quantity of dispersed crude oil defecated by planktonic copepods

AbstractWe investigated and quantified defecation rates of crude oil by 3 species of marine planktonic copepods (Temora turbinata, Acartia tonsa, and Parvocalanus crassirostris) and a natural copepod assemblage after exposure to mechanically or chemically dispersed crude oil. Between 88 and 100% of the analyzed fecal pellets from three species of copepods and a natural copepod assemblage exposed for 48 h to physically or chemically dispersed light crude oil contained crude oil droplets. Crude oil droplets inside fecal pellets were smaller (median diameter: 2.4–3.5 μm) than droplets in the physically and chemically dispersed oil emulsions (median diameter: 6.6 and 8.0 μm, respectively). This suggests that copepods can reject large crude oil droplets or that crude oil droplets are broken into smaller oil droplets before or during ingestion. Depending on the species and experimental treatments, crude oil defecation rates ranged from 5.3 to 245 ng-oil copepod−1 d−1, which represent a mean weight-specific defecation rate of 0.026 μg-oil μg-Ccopepod1 d−1. Considering a dispersed crude oil concentration commonly found in the water column after oil spills (1 μl L−1) and copepod abundances in high productive coastal areas, copepods may defecate ∼1.3–2.6 mg-oil m−3 d−1, which would represent ∼0.15%–0.30% of the total dispersed oil per day. Our results indicate that ingestion and subsequent defecation of crude oil by planktonic copepods has a small influence on the overall mass of oil spills in the short term, but may be quantitatively important in the flux of oil from surface water to sediments and in the transfer of low-solubility, toxic petroleum hydrocarbons into food webs after crude oil spills in the sea

Implicações da recepção do aporte de capital nas empresas estatais independentes: o caso do SERPRO

This paper addresses the self-sufficiency of the operational activities carried out for cash generation purposes at the Federal Data Processing Service (Serpro) aiming at its continuity as an independent state-owned company vis-à-vis the controlling shareholder. A qualitative, descriptive and documentary study is conducted to analyze the cash flow behaviors in operating, investment and financing activities, alongside the financial statements from 2005 to 2016. The analysis pointed to: a decrease in the cash balance from 2005 onwards, with a recurring shortage of operating activities compared to cash consumption; cash reconciliation based on financing activity involving constant capital injections from the controlling entity; evidence of payment of current expenses and dividends with capital contribution; receipt of financial contribution in 2012 and 2014, without prejudice to the status of independence and therefore in prejudice to legal regulations. The analysis also reveals that Serpro was uncompliant to the characteristics and the requirements of an independent state-owned company during the period. The results of this study have practical implications as it discusses and proposes aspects regarding the planning and development of the public audits oriented to the analysis of the conditions of dependence in independent state-owned companies building on the accounting information.No estudo, avaliou-se a autossuficiência das atividades operacionais do Serviço Federal de Processamento de Dados (Serpro) na geração de caixa, de modo a permitir sua continuidade como empresa estatal independente ante o controlador. Para tanto, por meio de pesquisa de natureza qualitativa, do tipo descritiva e documental, analisou-se o comportamento dos fluxos de caixa das atividades operacionais, de investimento e de financiamento, em conjunto com as demonstrações contábeis, de 2005 a 2016. Observaram-se: decréscimo no saldo de caixa a partir de 2005, com recorrente insuficiência das atividades operacionais face ao consumo de caixa; recomposição do caixa mediante atividade de financiamento com constantes aportes de capital do ente controlador; indícios de pagamento de despesas correntes e dividendos com aporte de capital; recebimento financeiro em 2012 e 2014, sem perda da condição de independente, descumprindo normativos legais. A partir dos procedimentos adotados, constatou-se que, no período analisado, o Serpro encontrou-se em condições de não aderência às características e aos requisitos de estatal independente. Os resultados do estudo apresentam implicações práticas à medida que discute e propõe aspectos quanto ao planejamento e à execução das auditorias públicas voltadas à análise das condições de dependência das empresas estatais independentes sustentadas a partir das informações contábeis

Rapid shifts in the thermal sensitivity of growth but not development rate causes temperature-size response variability during ontogeny in arthropods

Size at maturity in ectotherms commonly declines with warming. This near‐universal phenomenon, formalised as the temperature–size rule, has been observed in over 80% of tested species, from bacteria to fish. The proximate cause has been attributed to the greater temperature dependence of development rate than growth rate, causing individuals to develop earlier but mature smaller in the warm. However, few studies have examined the ontogenetic progression of the temperature–size response at high resolution. Using marine planktonic copepods, we experimentally determined the progression of the temperature–size response over ontogeny. Temperature–size responses were not generated gradually from egg to adult, contrary to the predictions of a naïve model in which development rate was assumed to be more temperature‐dependent than growth rate, and the difference in the temperature dependence of these two rates remained constant over ontogeny. Instead, the ontogenetic progression of the temperature–size response in experimental animals was highly episodic, indicating rapid changes in the extent to which growth and development rates are thermally decoupled. The strongest temperature–size responses occurred temporally mid‐way through ontogeny, corresponding with the point at which individuals reached between ~5 and 25% of their adult mass. Using the copepod Oithona nana, we show that the temperature‐dependence of growth rate varied substantially throughout ontogeny, whereas the temperature dependence of development rate remained constant. The temperature‐dependence of growth rate even exceeded that of development rate in some life stages, leading to a weakening of the temperature–size response. Our analyses of arthropod temperature–size responses from the literature, including crustaceans and insects, support these conclusions more broadly. Overall, our findings provide a better understanding of how the temperature–size rule is produced over ontogeny. Whereas we find support for the generality of developmental rate isomorphy in arthropods (shared temperature dependence of development rate across life stages), this concept appears not to apply to growth rates.</jats:p

Die rußländische Sicherheitspolitik um die Jahrtausendwende

13 pages, 3 figures, 6 tablesThe metabolic carbon requirements and excretion rates of three major zooplankton groups in the Southern Ocean were studied in the vicinity of the Antarctic Peninsula in February 2009. The research was conducted in the framework of the ATOS project (POL2006-00550/CTM), as part of the Spanish contribution to the International Polar Year. Our objective was to ascertain the possible consequences of changes on size spectrum and community structure of the Southern Ocean zooplankton for the cycling of biogenic carbon and the stoichiometry of dissolved inorganic nutrients. The carbon respiratory demands and NH4-N and PO4-P excretion rates of < 5 mm size copepods, krill (represented by furcilia spp. and adult Euphausia superba) and salps (blastozoids of Salpa thompsoni) were estimated by incubation experiments. The respiration rates and N:P metabolic quotients of salps were more than twice those of krill (furcilia spp. and adults) and copepods. The possible community shift from krill to salps in the Southern Ocean would therefore encompass not only the substitution of a pivotal zooplankton group (krill) by one with an apparently indifferent role in Antarctic food webs and with higher specific metabolic carbon demands (salps), but the changes in the proportion of zooplankton-recycled N and P would modify the N:P stoichiometry of the dissolved nutrient pool, thus inducing changes in the functional and structural properties of phytoplankton that would translate to the whole Southern Ocean ecosystemThis work was supported by the Spanish funded projects ATOS (POL 2006-0550/CTM) to Carlos M. Duarte, PERFIL (CTM 2006-12344-C01) to Miquel Alcaraz, and the UE funded project ATP (www.eu-atp.org) contract # 226248 to P. WassmannPeer Reviewe

Influence of UVB radiation on the lethal and sublethal toxicity of dispersed crude oil to planktonic copepod nauplii

AbstractToxic effects of petroleum to marine zooplankton have been generally investigated using dissolved petroleum hydrocarbons and in the absence of sunlight. In this study, we determined the influence of natural ultraviolet B (UVB) radiation on the lethal and sublethal toxicity of dispersed crude oil to naupliar stages of the planktonic copepods Acartia tonsa, Temora turbinata and Pseudodiaptomus pelagicus. Low concentrations of dispersed crude oil (1 μL L−1) caused a significant reduction in survival, growth and swimming activity of copepod nauplii after 48 h of exposure. UVB radiation increased toxicity of dispersed crude oil by 1.3–3.8 times, depending on the experiment and measured variables. Ingestion of crude oil droplets may increase photoenhanced toxicity of crude oil to copepod nauplii by enhancing photosensitization. Photoenhanced sublethal toxicity was significantly higher when T. turbinata nauplii were exposed to dispersant-treated oil than crude oil alone, suggesting that chemical dispersion of crude oil may promote photoenhanced toxicity to marine zooplankton. Our results demonstrate that acute exposure to concentrations of dispersed crude oil and dispersant (Corexit 9500) commonly found in the sea after oil spills are highly toxic to copepod nauplii and that natural levels of UVB radiation substantially increase the toxicity of crude oil to these planktonic organisms. Overall, this study emphasizes the importance of considering sunlight in petroleum toxicological studies and models to better estimate the impact of crude oil spills on marine zooplankton

Novel insight into the role of heterotrophic dinoflagellates in the fate of crude oil in the sea

Although planktonic protozoans are likely to interact with dispersed crude oil after a spill, protozoan-mediated processes affecting crude oil pollution in the sea are still not well known. Here, we present the first evidence of ingestion and defecation of physically or chemically dispersed crude oil droplets (1–86 μm in diameter) by heterotrophic dinoflagellates, major components of marine planktonic food webs. At a crude oil concentration commonly found after an oil spill (1 μL L(−1)), the heterotrophic dinoflagellates Noctiluca scintillans and Gyrodinium spirale grew and ingested ~0.37 μg-oil μg-C(dino)(−1) d(−1), which could represent ~17% to 100% of dispersed oil in surface waters when heterotrophic dinoflagellates are abundant or bloom. Egestion of faecal pellets containing crude oil by heterotrophic dinoflagellates could contribute to the sinking and flux of toxic petroleum hydrocarbons in coastal waters. Our study indicates that crude oil ingestion by heterotrophic dinoflagellates is a noteworthy route by which petroleum enters marine food webs and a previously overlooked biological process influencing the fate of crude oil in the sea after spills