The role of copepods and heterotrophic dinoflagellates in the production of dissolved organic matter and inorganic nutrients

Zooplankton play a key role in the cycling of dissolved organic matter (DOM) and inorganic nutrients. The factors that affect these processes, however, are not fully understood. I measured the effects of various diets on DOM and inorganic nutrient production by the copepod Acartia tonsa and the heterotrophic dinoflagellate Oxyrrhis marina, and explored the mechanisms of nutrient release from copepods. Copepods feeding on a mixed diet, the preferred diet of most copepods, had significantly lower dissolved organic carbon (DOC), ammonium (NH4+), and total dissolved nitrogen (TDN) release rates compared to feeding on a carnivorous or herbivorous diet. Thus, copepod feeding strategy can control the magnitude and composition of regenerated nutrients supplied to bacteria and phytoplankton. Secondly. I determined the effects of non-bloom and bloom concentrations of non-toxic and toxic cultures of harmful algal bloom (HAB) species Prorocentrum minimum and Karlodinium veneficum on grazing and production of DOM and inorganic nutrients by A. tonsa and O. marina. All algal diets deterred grazing, which likely resulted in starvation and subsequent catabolism of grazer body tissue. Additionally, DOM was typically a higher proportion of total dissolved nutrients released by zooplankton while feeding on the toxic algal culture, suggesting algal nutrient quality or direct toxic effects played a role in the differential nutrient release. Low ingestion rates coupled with high nutrient release rates could lead to feedback mechanisms that could intensify HABs. Finally, the various mechanisms of A. tonsa nutrient release, including sloppy feeding, excretion, and fecal pellet leaching, were isolated. Excretion and sloppy feeding were the dominant modes of DOC and NH4+ release, while sloppy feeding and fecal pellet leaching were dominant modes of urea release. A large proportion of ingested PON was lost as dissolved NH4+ and urea from copepods via all release mechanisms. These results have implications for the rapidity and location at which the regenerated nutrients are recycled in the water column. My dissertation results emphasize the importance of diet and release mechanism on the production of nutrients, particularly DOM, by zooplankton, which are important in understanding the recycling and transfer of nutrients and organic matter in marine food webs

Abundance, Composition, and Sinking Rates of Fish Fecal Pellets in the Santa Barbara Channel

Rapidly sinking fecal pellets are an important component of the vertical flux of particulate organic matter (POM) from the surface to the ocean\u27s interior; however, few studies have examined the role fish play in this export. We determined abundance, size, prey composition, particulate organic carbon/nitrogen (POC/PON), and sinking rates of fecal pellets produced by a forage fish, likely the northern anchovy, in the Santa Barbara Channel. Pellet abundance ranged from 0.1-5.9 pellets m(-3). POC and PON contents averaged 21.7 mu g C pellet(-1) and 2.7 mu g N pellet(-1). The sinking rate averaged 787 m d(-1); thus pellets produced at the surface would reach the benthos (similar to 500 m) in m(-2) d(-1). This is equal to or exceeds previous measurements of sediment trap POM flux, and thus may transport significant amounts of repackaged surface material to depth

Estilos educativos parentales, conducta hostil y resiliencia en adolescentes de una institución educativa en Lima 2019

Esta investigación tuvo como finalidad determinar el rol mediador de la resiliencia entre los estilos educativos parentales y conducta hostil en adolescentes de una institución educativa en Lima. El diseño de investigación es no experimental, de un corte transversal con un método explicativo. La muestra estuvo compuesta por 459 adolescentes que cursaron el nivel secundario. La técnica de recolección de datos fue la versión corta del Cuestionario de Autoridad Parental, el Inventario Multiculltural Latinoamericano de Hostilidad y la versión corta de la Escala de Resiliencia de Connor y Davidson. En los resultados se evidenciaron que en esta muestra la resiliencia no estaría cumpliendo como rol mediador entre los estilos educativos parentales y conducta hostil. En cuanto a los Estilos educativos parentales democrático explico de manera estadísticamente significativa a la resiliencia indicando los valores p<.05, por el contrario, los estilos educativos parentales autoritarios explican de manera estadísticamente significativa a la conducta hostil p<.05 cumpliendo así los valores aceptados. En conclusión, en esta investigación no hay evidencias suficientes para declarar a la resiliencia como un rol mediador con las otras dos variables de estudio

Toward a better understanding of fish‐based contribution to ocean carbon flux

Fishes are the dominant vertebrates in the ocean, yet we know little of their contribution to carbon export flux at regional to global scales. We synthesize the existing information on fish‐based carbon flux in coastal and pelagic waters, identify gaps and challenges in measuring this flux and approaches to address them, and recommend research priorities. Based on our synthesis of passive (fecal pellet sinking) and active (migratory) flux of fishes, we estimated that fishes contribute an average (± standard deviation) of about 16.1% (± 13%) to total carbon flux out of the euphotic zone. Using the mean value of model‐generated global carbon flux estimates, this equates to an annual flux of 1.5 ± 1.2 Pg C yr−1. High variability in estimations of the fish‐based contribution to total carbon flux among previous field studies and reported here highlight significant methodological variations and observational gaps in our present knowledge. Community‐adopted methodological standards, improved and more frequent measurements of biomass and passive and active fluxes of fishes, and stronger linkages between observations and models will decrease uncertainty, increase our confidence in the estimation of fish‐based carbon flux, and enable identification of controlling factors to account for spatial and temporal variability. Better constraints on this key component of the biological pump will provide a baseline for understanding how ongoing climate change and harvest will affect the role fishes play in carbon flux

Winter and spring controls on the summer food web of the coastal West Antarctic Peninsula

Understanding the mechanisms by which climate variability affects multiple trophic levels in food webs is essential for determining ecosystem responses to climate change. Here we use over two decades of data collected by the Palmer Long Term Ecological Research program (PAL-LTER) to determine how large-scale climate and local physical forcing affect phytoplankton, zooplankton and an apex predator along the West Antarctic Peninsula (WAP). We show that positive anomalies in chlorophyll-a (chl-a) at Palmer Station, occurring every 4-6 years, are constrained by physical processes in the preceding winter/spring and a negative phase of the Southern Annular Mode (SAM). Favorable conditions for phytoplankton included increased winter ice extent and duration, reduced spring/summer winds, and increased water column stability via enhanced salinity-driven density gradients. Years of positive chl-a anomalies are associated with the initiation of a robust krill cohort the following summer, which is evident in Adelie penguin diets, thus demonstrating tight trophic coupling. Projected climate change in this region may have a significant, negative impact on phytoplankton biomass, krill recruitment and upper trophic level predators in this coastal Antarctic ecosystem

Penguin biogeography along the West Antarctic Peninsula: Testing the canyon hypothesis with Palmer LTER observations

The West Antarctic Peninsula (WAP) is home to large breeding colonies of the ice-dependent Antarctic Adélie penguin (Pygoscelis adeliae). Although the entire inner continental shelf is highly productive, with abundant phytoplankton and krill populations, penguin colonies are distributed heterogeneously along the WAP (Ducklow et al., 2013, in this issue). This ecological conundrum targets a long-standing question of interest: what environmental factors structure the locations of Adélie penguin "hot spots" throughout the WAP

Toward a better understanding of fish‐based contribution to ocean carbon flux

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Recommended Priorities for Research on Ecological Impacts of Ocean and Coastal Acidification in the U.S. Mid-Atlantic

The estuaries and continental shelf system of the United States Mid-Atlantic are subject to ocean acidification driven by atmospheric CO2, and coastal acidification caused by nearshore and land-sea interactions that include biological, chemical, and physical processes. These processes include freshwater and nutrient input from rivers and groundwater; tidally-driven outwelling of nutrients, inorganic carbon, alkalinity; high productivity and respiration; and hypoxia. Hence, these complex dynamic systems exhibit substantial daily, seasonal, and interannual variability that is not well captured by current acidification research on Mid-Atlantic organisms and ecosystems. We present recommendations for research priorities that target better understanding of the ecological impacts of acidification in the U. S. Mid-Atlantic region. Suggested priorities are: 1) Determining the impact of multiple stressors on our resource species as well as the magnitude of acidification; 2) Filling information gaps on major taxa and regionally important species in different life stages to improve understanding of their response to variable temporal scales and sources of acidification; 3) Improving experimental approaches to incorporate realistic environmental variability and gradients, include interactions with other environmental stressors, increase transferability to other systems or organisms, and evaluate community and ecosystem response; 4) Determining the capacity of important species to acclimate or adapt to changing ocean conditions; 5) Considering multi-disciplinary, ecosystem-level research that examines acidification impacts on biodiversity and biotic interactions; and 6) Connecting potential acidification-induced ecological impacts to ecosystem services and the economy. These recommendations, while developed for the Mid-Atlantic, can be applicable to other regions will help align research towards knowledge of potential larger-scale ecological and economic impacts

Penguin Biogeography Along the West Antarctic Peninsula Testing the Canyon Hypothesis with Palmer LTER Observations

The West Antarctic Peninsula (WAP) is home to large breeding colonies of the ice-dependent Antarctic Adélie penguin (Pygoscelis adeliae). Although the entire inner continental shelf is highly productive, with abundant phytoplankton and krill populations, penguin colonies are distributed heterogeneously along the WAP (Ducklow et al., 2013, in this issue). This ecological conundrum targets a long-standing question of interest: what environmental factors structure the locations of Adélie penguin “hot spots” throughout the WAP