Derek E. Smith

Ice cover extent drives phytoplankton and bacterial community structure in a large north‐temperate lake: implications for a warming climate

Mid-winter limnological surveys of Lake Erie captured extremes in ice extent ranging from expansive ice cover in 2010 and 2011 to nearly ice-free waters in 2012. Consistent with a warming climate, ice cover on the Great Lakes is in decline, thus the ice-free condition encountered may foreshadow the lakes future winter state. Here, we show that pronounced changes in annual ice cover are accompanied by equally important shifts in phytoplankton and bacterial community structure. Expansive ice cover supported phytoplankton blooms of filamentous diatoms. By comparison, ice free conditions promoted the growth of smaller sized cells that attained lower total biomass. We propose that isothermal mixing and elevated turbidity in the absence of ice cover resulted in light limitation of the phytoplankton during winter. Additional insights into microbial community dynamics were gleaned from short 16S rRNA tag (Itag) Illumina sequencing. UniFrac analysis of Itag sequences showed clear separation of microbial communities related to presence or absence of ice cover. Whereas the ecological implications of the changing bacterial community are unclear at this time, it is likely that the observed shift from a phytoplankton community dominated by filamentous diatoms to smaller cells will have far reaching ecosystem effects including food web disruptions.

Water velocity modeling can delineate nearshore and main channel plankton environments in a large river

Methods to distinguish nearshore and main channel ecosystems within large rivers are essential for observing physical, chemical, and biological features that influence overall river ecosystem function. Water velocity fields based on hydrodynamic modeling of water flow trajectory were used to evaluate water history (i.e., water moving slowly as in a slack water region, or more rapidly, as characteristic of the main channel) prior to passing a given point in the Upper St. Lawrence River. Using this method to differentiate zones in the river, observations of biotic and abiotic variables in nearshore and main channel zones during late spring and summer (June–August) were compared to assess the difference in these water column river ecosystems. Differences in plankton community composition between nearshore and main channel waters along the Upper St. Lawrence River were investigated to test the hypothesis that nearshore and main channel environments in large river systems have different biotic (e.g., phytoplankton, crustacean zooplankton, and rotifer concentrations) and abiotic [e.g., water temperature, specific conductivity, silicate, colored dissolved organic matter (CDOM), and total phosphorus] characteristics. Nearshore water had significantly higher concentrations of CDOM and chlorophyll-a than main channel waters. With distance downstream, crustacean zooplankton and rotifers decreased in abundance in both nearshore and main channel regions. This study describes an effective method for stratified sampling design that differentiates nearshore and main channel ecosystems in the water column of large rivers.

Detection of oligoprogressive disease in oncogene-addicted non-small cell lung cancer using PET/CT versus CT in patients receiving a tyrosine kinase inhibitor

OBJECTIVES In oncogene-addicted non-small cell lung cancer (NSCLC), oligoprogressive disease (OPD) can be treated with local ablative therapy (LAT) to prolong benefit from tyrosine kinase inhibitors (TKIs). A comparison of PET/CT vs. CT for the detection of OPD at first extra central nervous system (eCNS) progression was performed to determine which modality was more sensitive for OPD detection. MATERIALS AND METHODS Patients with metastatic EGFR-MT, ALK + or ROS-1+ NSCLC on a relevant TKI from 2010 to 2016 were identified. Scan methodology at first eCNS progression (index scan) was noted and progression was categorized as OPD (≤ 4 lesions) or non-OPD (> 4 lesions). RESULTS Of the 67 analyzable patients (EGFR-MT = 37, ALK+ = 28, ROS1+ = 2), OPD was detected in 81.3% (26/32) by PET/CT vs. 68.6% (24/35) by CT (p = 0.363). Of these, 17/26(65.4%) in PET/CT and 5/24(20.8%) in CT group had LAT (p = 0.004). Among patients receiving an alternate modality scan within 6 weeks of the index scan that showed first eCNS progression, 91.7% (11/12) had CT prior to index PET/CT, 75% (6/8) had post-index PET/CT showing further progression, whereas 0% (0/5) had post-index CT showing further progression. Time to progression (TTP), Post-progression TKI benefit (TTP2) and overall survival (OS) were longer in the PET/CT-detected group (p = 0.001, p = 0.032, and p = 0.01, respectively). In both PET/CT (N = 26) and CT-detected (N = 24) OPD subgroups, TTP2 and OS were longer in those that received LAT (65.4% [17/26] and 20.8% [5/24]) versus those that did not, although the difference was not statistically significant. CONCLUSION PET/CT demonstrated a non-significant trend to detect more eCNS OPD and a significantly higher rate of OPD suitable for LAT than CT. Peri-progression alternate modality scans were also consistent with PET/CT being more sensitive. A prospective randomized study is required to assess the long-term impact of PET/CT vs CT in oncogene-addicted NSCLC patients on TKI therapy.