Alkenone distribution in Lake Van sediment over the last 270 ka: influence of temperature and haptophyte species composition

Fossil long-chain alkenones have been used for several decades to reconstruct past ocean surface water temperatures and gained recent interest as a paleotemperature proxy for continental lake settings. However, factors besides temperature can affect alkenone distributions in haptophyte algae, and alkenone compositions can differ between haptophyte species. Alkenone-biosynthesizing haptophyte algae are genetically much more diverse in lakes than in the marine realm, and species-level variations in alkenone compositions could have implications for alkenone paleothermometry. Here, we performed a paired analysis of alkenone distributions and haptophyte species compositions using ancient DNA in up to 270 ka-old sediments of Lake Van in Turkey to reveal a possible species-effect on fossil alkenone distributions and paleotemperature estimates. The same predominant haptophyte in Lake Van today prevailed also since the last ~100 ka. However, a calibration of alkenone paleotemperature especially in the oldest analyzed intervals is complicated due to a more complex haptophyte species composition predominated by a haptophyte (LVHap_6), which is phylogenetically different from sequences recovered from currently existing lakes including Lake Van and from haptophyte species existing in culture. Thepredominance of LVHap_6 coincided with the presence of alkenone MeC38:3 and relatively highMeC37:3/4 (2.4) and MeC38:4/5 ratios (3.0). Uk37 index values in the sediment core over the last 270 ka reflect relative changes in past temperature and are additionally linked to haptophyte species composition. A sustained period of high salinity, as indicated by pore-water salinity measurements, could potentially have triggered the succession of haptophytes as sources of alkenones in Lake Van

Strategic Public Management for Financial Condition: Focus on Fund Balances of School Districts

Scholars have emphasized the roles of strategic public management and the financial condition but little is known about the link between the two. Finding the missing link is the purpose of this study. By analyzing data from K-12 Texas school districts, this study investigates how top managers’ strategic efforts toward their superiors, subordinates, and external stakeholders affect the financial condition of school districts. The findings suggest that superintendents’ managing upward toward school boards increases fund balances, whereas managing downward toward school principals decreases fund balances. Apparently, the relationships between school boards, superintendents, and school principals contain different priorities and incentives that influence their behaviors in managing school district budgets.Accepted versio