Andrew Kalmbach

• Master of Science
• Researcher at ICF International

Zooplankton density and community composition in estuaries can be affected by variation in freshwater inputs, with important implications for higher trophic levels. In the San Francisco Estuary, management agencies have initiated autumn flow augmentations in the form of changes to reservoir releases or to exported water from the South Delta to incr...

Longfin Smelt (Spirinchus thaleichthys) was an important forage fish in the San Francisco Estuary (the SFE) but was listed as threatened under the California Endangered Species Act in 2009. This has inspired research within the estuary at the southern edge of their distribution. However, populations also exist in other estuaries along the coast, wh...

Recruitment of estuarine organisms can vary dramatically from year to year with abiotic and biotic conditions. The San Francisco Estuary (California, USA) supports a dynamic ecosystem that receives freshwater flow from numerous tributaries that drain one of the largest watersheds in western North America. In this study, we examined distribution and...

The McMurdo Dry Valleys (MDV) in Antarctica harbor a diverse assemblage of mat-forming diazotrophic cyanobacteria that play a key role in nitrogen cycling. Prior research showed that heterotrophic diazotrophs also make a substantial contribution to nitrogen fixation in MDV. The goals of this study were to survey autotrophic and heterotrophic diazot...

Diazotrophic cyanobacteria, those capable of fixing di-nitrogen (N2), are considered one of the major sources of new nitrogen (N) in the oligotrophic tropical ocean, but direct incorporation of diazotrophic N into food webs has not been fully examined. In the Amazon River-influenced western tropical North Atlantic (WTNA), diatom diazotroph associat...

It is commonly thought that biological media cannot exhibit an appreciable nonlinear optical response. We demonstrate, for the first time to our knowledge, a tunable optical nonlinearity in suspensions of cyanobacteria that leads to robust propagation and strong self-action of a light beam. By deliberately altering the host environment of the marin...

We study nonlinear light propagation through suspensions of Synechococcus cells. Such cyanobacteria in aqueous solution enable self-focusing and -defocusing of a light beam, leading to controlled transmission despite extremely low absorption and weak polarizability.