Online resource for: Cross-habitat effects shape the ecosystem consequences of co-invasion by a pelagic and benthic consumer
David C. Fryxell, Amber R. Diluzio, Maya A. Friedman, Nicklaus A. Menge, and Eric P. Palkovacs
Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA 95060, USA
1.1Upper Warm Springs, Inyo County California. This site served as the source for experimental crayfish and mosquitofish. It is a dammed spring with purpose to house a refuge population of endangered Owens pupfish (Cyprinodonradiosus). The pupfish population became extirpated there in 2008. Today, non-native mosquitofish are the only fish present, and non-native red swamp crayfish are the only crayfish present. Photo credit: D. Fryxell.
1.2The mesocosm array used in this study, located at the Long Marine Laboratory of the University of California- Santa Cruz, Santa Cruz, CA 95060. Younger Lagoon Reserve and the Pacific Ocean are visible in the upper right. Photo credit: D. Fryxell.
1.3Estimating phytoplankton abundance using pelagic chlorophyll a.Using a depth-integrated water sampler, we collected 1-2 liters of mesocosm water and immediately filtered it through a 0.7 µm Whatman® GF/F filter. The filter was then frozen. Within one month we extracted the chlorophyll aon the filter with 90% acetone at 2° C for 24 hours and then measured its concentration using the non-acid module in the Turner Designs® Trilogy Lab Fluorometer.
1.4Estimating gross primary production (GPP) using diel change in dissolved oxygen. We measured dissolved oxygen concentration at dawn, dusk, and the following dawn using a YSI® Pro 2030 sonde. We calculated the hourly rate of respiration as the decrease in dissolved oxygen between dusk and the following dawn divided by the total number of nighttime hours. We then determined GPP as the amount of dissolved oxygen increase during daylight (dusk minus the previous dawn) hours plus the respiration rate * the number of daylight hours. Units of GPP are therefore the concentration of dissolved oxygen increase during the day while accounting for decreases due to respiration. Similar methods have been used in other recent papers (Harmon et al. 2009, Fryxell et al. 2015).
Harmon, L. J., Matthews, B., Des Roches, S., Chase, J. M., Shurin, J. B., & Schluter, D. (2009). Evolutionary diversification in stickleback affects ecosystem functioning. Nature, 458(7242), 1167-1170.
Fryxell, D. C., Arnett, H. A., Apgar, T. M., Kinnison, M. T., & Palkovacs, E. P. (2015). Sex ratio variation shapes the ecological effects of a globally introduced freshwater fish. Proc. R. Soc. B. Online early.
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