Growth and grazing losses of prokaryotes in the central Atlantic Ocean

doi:10.1093/plankt/fbi074 On page 1058, in paragraph 4, lines 1 to 5     

Zooplankton influence on the phytoplankton-bacterioplankton coupling

The evolution of phytoplankton biomass, and bacterial numberand activity were followed in laboratory microcosms with andwithout zooplankton, in order to study the time lag betweenphytoplankton and bacterioplankton development, as well as thepossible influence of consumers on phytoplankton-bacterioplanktoncoupling.     

Extended Life Cycle Assessment of Southern Pink Shrimp Products Originating in Senegalese Artisanal and Industrial Fisheries for Export to Europe

Southern pink shrimp (Penaeus notialis) are an important Senegalese export commodity. Artisanal fisheries in rivers produce 60%. Forty percent are landed in trawl fisheries at sea. The shrimp from both fisheries result in a frozen, consumer‐packed product that is exported to Europe. We applied attributional life cycle assessment (LCA) to compare the environmental impact of the two supply chains and identify improvement options. In addition to standard LCA impact categories, biological impacts of each fishery were quantified with regard to landed by‐catch, discard, seafloor impact, and size of target catch. Results for typical LCA categories include that artisanal fisheries have much lower inputs and emissions in the fishing phase than does the industrial fishery. For the product from artisanal fisheries, the main part of the impact in the standard LCA categories occurs during processing on land, mainly due to the use of heavy fuel oil and refrigerants with high global warming and ozone depletion potentials. From a biological point of view, each fishery has advantages and drawbacks, and a number of improvement options were identified. If developing countries can ensure biological sustainability of their fisheries and design the chain on land in a resource‐efficient way, long distance to markets is not an obstacle to sustainable trading of seafood products originating in artisanal fisheries.     

The Ethical Use of Placebo Controls in Clinical Research: The Declaration of Helsinki

Medical ethicists have questioned the use of no-treatment (placebo and sham procedure) controlled studies of new therapies when safe and effective standard therapies are available for use as an active or equivalence control. Current ethical principles of conduct for biomedical research specifically prohibit designs that withhold or deny the best proven diagnostic and therapeutic treatment to any participant in a clinical study, including those individuals who consent to randomization into a control group. Studies of psychophysiological therapies are often criticized on the grounds they lack a placebo or sham treatment control group. This paper briefly reviews the history of the problem and discusses the ethical standards that govern human research as derived from the Nuremberg Code and the Declaration of Helsinki. An examination of the problem with regard to research involving EEG biofeedback therapy for Attention-Deficit/Hyperactivity Disorder, Traumatic Brain Injury, and depression serves to highlight the issues. It is concluded that the active treatment control (treatment equivalence) design is most appropriate for those clinical studies examining disorders for which there is a known, effective treatment. Sham- or placebo-controlled studies are ethically acceptable for those disorders for which no effective treatment is available.     

Zooplankton biomass distribution patterns along the western Antarctic Peninsula (December 2002)

The phytoplankton [chlorophyll a (Chl a)], microzooplankton,mesozooplankton and macrozooplankton biomass and distributionwere studied as part of a multidisciplinary project (Tempano)along the Antarctic Peninsula during December 2002. Even thoughthe summer phytoplankton bloom was not yet developed in thearea, autotrophs dominated the plankton biomass. Phytoplanktonvertical distribution was, in general, homogeneous in the upper40–50 m of the water column, further decreasing with depth.Protozoans showed low biomass; their contribution to the totalplankton being one order of magnitude lower than that of autotrophs.The vertical distribution of protozoans was variable among stationswith marked peaks at depths ranging from 30 to 80 m. Mesozooplankton-integratedbiomass was generally low, although there was a notable increasesouthward near the ice marginal zone. Macrozooplankton distributionwas more variable without any clear zonal distribution pattern.The vertical distribution of meso- and macrozooplankton (>4mm) biomass showed clear peaks of abundance comprising differentspecies depending on the geographical area. Our biomass distributiondata suggest a food-web scenario in which macrozooplankton arepreying on mesozooplankton populations only in the northernerstations, and mesozooplankton are, in their turn, shaping theabundance of the emerging populations of microzooplankton. Phytoplankton,on the other hand, seem to be hardly controlled by grazing activity.     

Growth and grazing losses of prokaryotes in the central Atlantic Ocean

The trophic relation between prokaryotes and heterotrophic nanoflagellateswas studied during two latitudinal cruises in the central AtlanticOcean. The losses to predation on prokaryotes were determinedin 12 locations covering a wide range of trophic situations,from ultraoligotrophic [<0.05 mg chlorophyll a (Chl a) m^–3]to moderately eutrophic waters (>1 mg Chl a m^–3). Inthese locations, the abundance of prokaryotes (P) covaries withthat of heterotrophic nanoflagellates, thus suggesting thatresources controlled the abundance of heterotrophic nanoflagellates(HNF). Besides, the losses to predation were positively relatedto prokaryotic and heterotrophic nanoflagellate biomass, whichpoints toward higher consumption rates associated with largerconcentrations of preys and predators. Conversely, decliningtrends between prokaryotic production (P_P) and the fractionof this production lost to predation revealed higher relativelosses in the environments with lower productions. Our studyshows for the central Atlantic that 35% of prokaryotic biomass(B_P), equating to between 40 and 83% of P_P can be ingested dailyand that 55% of the variability observed in the rate of prokaryoticloss to predation was related with the HNF. As predators grazeon many prey types, in an oligotrophic system containing manyprey species but little numeric loading, there will still beprey for predators but not enough hosts for viruses. In thissense, our study confirms the importance of the prey–predatorrelationship between prokaryotes and heterotrophic nanoflagellatesin the flow of carbon of the less productive regions of theocean.     

Grazing on bacteria by flagellates and cladocerans in lakes of contrasting food-web structure

We tested the hypothesis that grazing on bacteria would varybetween lakes with differing plankton community structures.Paul and Tuesday lakes (Gogebic County, MI) are respectivelydominated by piscivorous and planktivorous fish. Consequently,zooplankton in Paul are primarily large daphnids, while zooplanktonin Tuesday are primarily small cladocerans and copepods. Wemeasured flagellate grazing on bacteria using a fluorescentminicell method, while cladoceran grazing was estimated fromthe relationship between body length and filtering rate. Wepredicted that cladoceran grazing on bacteria would be higherin Paul, and flagellate grazing would be higher in Tuesday.Cladoceran grazing on bacteria was important in both lakes contraryto our initial expectation. Large populations of the small cladoceran,Bosmina longirostris, in Tuesday exerted a grazing pressure(0.18–35x10⁶ bacteria 1^–1 h^–1) approximatelyequal to that of the large cladoceran, Daphnia pulex, in Paul(0.34–30x10⁶ bacteria 1^–1 h^–1). Flagellategrazing was higher in Tuesday as predicted (range: Paul, 0.1–6x10⁶bacteria 1^–1 h^–1; Tuesday, 0.2–20x10⁶ bacteria1^–1 h^–1). However, there was not a simple relationshipbetween total abundance of flagellates and total grazing rates.High community grazing by flagellates occurred when attachedchoanoflagellates were present. These flagellates had higheringestion rates than free forms. We find no clear evidence thatdifferences in food-web structure between the two lakes influencethe process of grazing on bacteria. Instead, our results emphasizethe significance of cladocerans and attached flagellates asconsumers of bacteria in freshwater ecosystems.     

Response to Striefel and Glaros

In this response to the comments of Drs. Striefel and Glaros, we take issue with Dr. Striefel's assertion that the Declaration of Helsinki should not be regarded as a core ethical document, and demonstrate that his claim that the Declaration has no significance in or recognition by agencies of the United States Federal Government is in error. A reading of FDA and DHHS documents shows that the Declaration is not, as Dr. Striefel suggested, only an aspirational document, but also is clearly regarded as mandatory. Dr. Glaros' observations regarding the slippery concept of efficacy is very much on point, and we certainly agree with his call for more data. It is the means by which that can be accomplished that is problematic. We have suggested that the logic of placebo controls developed to render drug efficacy studies more rigorous and scientifically grounded does not translate well to many psychological and behavioral studies of efficacy. It is important for our discipline to rethink the standards by which new behavioral and psychological (including psychophysiological) interventions can be demonstrated to be efficacious. One possible approach that avoids ethical pitfalls and design impossibilities is the active control, which requires good demonstration of assay sensitivity. We hope that this discussion may stimulate further discussion about other approaches that do not depend upon the flawed placebo orthodoxy.