Frentes y remolinos como estructuras clave en el habitat de las larvas de peces marinos: oportunidad, respuesta adaptativa y ventaja competitiva

Surface fronts and mesoscale eddies are two classes of ocean structures that engender significant pattern in the habitats of marine organisms. Both are sites where mechanical energy of the physical system may be accessible for augmenting trophic energy available to biological organisms. Accordingly, they may offer opportunities for exceptional local productivity and growth of species particularly adapted to excelling in such highly-productive rapid-growth/high-mortality situations. The major relevant physical mechanisms involved are presented. A widespread attraction of many types of fish to floating objects drifting in the ocean is cited as an apparent adaptive response to the desirable aspects of surface fronts. An apparent contrary tendency for certain important marine fish species to be particularly successful in relatively poorly productive situations, where slower growth may be offset by much lower early life predation mortality, is also noted. Competing tradeoffs between (1) early life nutrition and resulting growth, and (2) mortality of early stages due to predation are suggested. These tradeoffs are posed and illustrated via a “predator pit” conceptual framework. Illustrations of the evident reproductive habitat choices of several populations of large temperate tunas are briefly presented. It is concluded that the time may have come for a general shift in the approach of at-sea fish larval ecological investigations from the conventional focus on associations with environmental properties on a “macro” scale to intensive investigations of the real-time progressions of linked physical-biological interactions occurring on a “meso” (and smaller) scale.Los frentes superficiales y los remolinos de mesoescala son dos tipos de estructuras de mesoescala que producen patrones significativos en los hábitats de los organismos marinos. Ambos son notables por ser lugares en los que la energía mecánica del sistema físico puede ser accesible para aumentar la energía trófica disponible para los organismos biológicos. Por consiguiente, pueden ofrecer oportunidades para que se produzcan producciones y crecimientos localmente excepcionales de especies particularmente adaptadas a sobresalir en tales situaciones de alta producción/rápido crecimiento/alta mortalidad. Los mecanismos físicos de mayor relevancia involucrados son elaborados. La amplia atracción de muchos tipos de peces por objetos flotantes que derivan en el océano ha sido señalada como una aparente respuesta adaptativa a los aspectos deseables de los frentes superficiales. Existe una tendencia aparentemente contraria para ciertas importantes especies de peces marinas que son particularmente exitosas en situaciones productivas relativamente pobres, en las que se ha señalado que un crecimiento más lento podría ser contrarrestado por una menor mortalidad por predación en los primeros estadios de desarrollo, sugiriendo competencias compensadores entre (1) la nutrición y crecimiento resultante en las primeras fases de desarrollo, y (2) la mortalidad debida a la predación en estos primeros estadios. Estas contraposiciones se plantean y se ilustran vía un marco conceptual, el “hoyo de predación”. Se presentan brevemente ilustraciones de las “opciones” del hábitat reproductivo escogidas por varias poblaciones de grandes atunes de zonas templadas. Se extrae la conclusión de que puede haber llegado el momento de un cambio general en la “moda” de las investigaciones ecológicas sobre larvas de peces en-mar, enfocadas convencionalmente en asociaciones con las características ambientales a macroescala, hacia investigaciones intensivas de las progresiones en tiempo real de las interacciones físicobiológicas que suceden a mesoescala (y a menores escalas)

A comparative analysis of the efficacy of zero-order, first-order and Monod kinetic models in representing raw aerobic biodegradation data

A total of 148 raw aerobic biodegradation data sets from batch and continuous stirred-tank reactors were extracted from the open literature and previous NJIT MS theses. Kinetic analysis of each of these data sets was performed with respect to the following commonly used empirical models: (1) zero-order, (2) first-order, and (3) Monod. Two constant-biomass versions of each model were evaluated; one in which So (i.e., the boundary condition for substrate concentration at time equal to zero) was assumed to be equal to the measured value of the initial substrate concentration and the other in which So was treated as a regressable parameter. Where adequate biomass concentration data were available, variable-biomass versions of each model, in which So was assumed to be equal to the initial substrate concentration, were also evaluated. Each data set was categorized within one of nine different biodegradation data types and discussed with respect to the advantages and disadvantages of each model evaluated for the given data type. Model selection recommendations were given for each data type. A theoretical analysis of the effects of variations in raw biodegradation data on the corresponding regression results was performed for the constant- and variable-biomass models. The effects of random experimental error, number of data points, sampling regularity and substrate concentration range were evaluated. The impact of erroneous models on reactor sizing was also demonstrated

The seasonal upwelling cycle along the eastern boundary of the North Atlantic

Merchant ship observations were summarized for one-degree squares along the eastern shore of the Atlantic between 7° and 44°N; monthly averages were prepared for several properties including sea surface temperature and its difference from mid-ocean values, offshore Ekman transport, and surface current...

Dissolved organic phosphorus uptake by marine phytoplankton is enhanced by the presence of dissolved organic nitrogen

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Active opportunist species as potential diagnostic markers for comparative tracking of complex marine ecosystem responses to global trends

Abstract As it becomes ever clearer that on longer time scales marine ecosystems function as non-linear “complex adaptive systems”, potential consequences of global change become obscured within a maze of multiple possibilities. This essay attempts to route one pathway to a potentially more robust conceptual synthesis, employing the globally important example of anchovies and sardines as a model. Expressly, the anchovy emerges as an efficient specialist of neritic origin. In contrast, the sardine's oceanic-based adaptations equip it to deal with intermittent episodes of poorly productive conditions and to take advantage of associated reduction in predation pressure on early life stages of their offspring. Based on the overall synthesis, the nimble, wide-ranging, actively opportunistic sardine appears notably well equipped to deal with climate-related disruptions and dislocations and even to profit from their adverse effects on predators and competitors. Global-scale multispecies population synchronies in the 1970s to the mid-1980s suggest that a variety of different species types might be flagged for investigation as perhaps embodying similar “active opportunist” attributes. If so, events and anecdotes might, as global changes proceed, be viewed within a developing universal framework that could support increasingly effective transfers of experience and predictive foresight across different species groups and regional ecosystems

Linking climate to population variability in marine ecosystems characterized by non-simple dynamics: Conceptual templates and schematic constructs

The ability to abstract and symbolize ideas and knowledge as simplified schematic constructs is an important element of scientific creativity and communication. Availability of such generalized symbolic constructs may be particularly important when addressing a complex adaptive system such as a marine ecosystem. Various examples have appeared in the climate–fisheries literature, each more or less effectively integrating hypothesized effects of several interacting environmental and/or biological processes in controlling population dynamics of exploited fish species. A selection of these are herein presented and reviewed, including match–mismatch, connectivity, school trap, loopholes, ocean triads, stable ocean hypothesis, several classes of nonlinear feedback loops (e.g., ‘ P2P’, school-mix feedback, predator pit), as well as several prominent large-scale integrative climatic index series ( SOI, NAO, PDO). The importance of considering the potential for adaptation and/or rapid evolution is stressed. An argument is offered for the potential utility of such widely recognizable schematic concepts in offering relatively well-understood, fairly well-defined frameworks for comparative identification and elaboration of important mechanistic linkages between climate variability and fishery dynamics, as well as in easing effective communication among scientists from different regions and disciplinary backgrounds. Certain difficulties in the application of the comparative method are discussed. It is suggested that alleviation of such difficulties may be one of the major benefits of international collaborative programs such as GLOBEC and IMBER

Climate change and ocean deoxygenation within intensified surface-driven upwelling circulations

Ocean deoxygenation often takes place in proximity to zones of intense upwelling. Associated concerns about amplified ocean deoxygenation arise from an arguable likelihood that coastal upwelling systems in the world's oceans may further intensify as anthropogenic climate change proceeds. Comparative examples discussed include the uniquely intense seasonal Somali Current upwelling, the massive upwelling that occurs quasi-continuously off Namibia and the recently appearing and now annually recurring ‘dead zone’ off the US State of Oregon. The evident ‘transience’ in causal dynamics off Oregon is somewhat mirrored in an interannual-scale intermittence in eruptions of anaerobically formed noxious gases off Namibia. A mechanistic scheme draws the three examples towards a common context in which, in addition to the obvious but politically problematic remedy of actually reducing ‘greenhouse’ gas emissions, the potentially manageable abundance of strongly swimming, finely gill raker-meshed small pelagic fish emerges as a plausible regulating factor