Project description:In summer 2014, we conducted experiments to determine the effects of different N substrates on phytoplankton communities in the North Pacific Ocean and in the transition zone of the California Current and gyre (Shilova, Mills et al., 2017). Samples were incubated with nitrate, ammonium, urea, and filtered deep water (FDW) for 48 hours (T48). Two treatments added iron, alone (Fe) or with a mix of N substrates (N+Fe), to determine the effects of Fe on the utilization of N substrates. All treatments resulted in changes in phytoplankton cell abundances and photosynthetic activity at both locations, with differences between phytoplankton groups. Prochlorococcus had large increases in biomass in response to ammonium and urea, while both eukaryotic phytoplankton and Synechococcus had only modest biomass increases in response to N+Fe and FDW. Moreover, distinct physiological responses were observed within sub-populations of Prochlorococcus and Synechococcus. In order to understand the variable responses to N substrates among phytoplankton groups and sub-populations in the California Current transition zone, the present work examines transcriptional changes that occurred 24 h after the substrates were added. Specifically, we hypothesize that transcription changes at 24 h indicate which phytoplankton taxa are N-limited, and thus help explain changes in cell abundances and photosynthetic activity by individual phytoplankton groups observed at 48 h. Furthermore, we hypothesize that the diversity in physiological responses within Prochlorococcus and Synechococcus are evident in the transcriptional responses measured at sub-population resolution.
Project description:Hornyhead turbot (Pleuronichthys verticalis) captured near sewage outfalls are used as sentinel fish for monitoring exposure to industrial and agricultural chemicals of ~20 million people living in coastal southern California. Although analyses of hormones in blood and organ morphology and histology in fish are useful for assessing exposure, there is a need for quantitative and sensitive molecular measurements, as many contaminants produce subtle effects. A novel multispecies microarray and qRT-PCR were used to investigate endocrine disruption in turbot captured near sewage outfalls in San Diego, Orange County and Los Angeles California. Analysis of expression of genes involved in hormone [e.g. estrogen, androgen, thyroid] responses and xenobiotic metabolism in turbot livers was correlated with phenotypic end points.