Impact of nitrogen and phosphorus on phytoplankton production and bacterial community structure in two stratified Antarctic lakes: a bioassay approach
- 387 Downloads
Arctic, Antarctic, and alpine ecosystems are recognized as sensors and sentinels of global change. As a consequence of their high sensitivity to minor climatic perturbations, permanently ice-covered lakes located in the McMurdo Dry Valleys (MDV), Antarctica, represent end members in the global network of inland bodies of water. Episodic climatic events in the form of increased summer glacial melt result in inputs of organic sediment and nutrients from glacial streams to these closed basins. Phytoplankton communities residing in the oligotrophic water columns are highly responsive to pulses in nutrient availability; however, there is a lack of understanding on whether specific phytoplankton groups are more competitive during a summer flood event and how shifts in the phytoplankton community may influence heterotrophic bacteria. A bioassay approach in 3-l bottles was used to investigate the influence of inorganic nitrogen and phosphorus availability on planktonic communities from the oligotrophic upper waters of two chemically distinct MDV lakes (Lakes Bonney and Fryxell) which differ in their external inputs and water column N/P stoichiometry. While microbial community responses varied between lakes and were nutrient-dependent, stimulation of phytoplankton biomass and productivity across all treatments was strongly linked with increased abundance of a single phytoplankton phylum (Chlorophyta). Despite stimulation of phytoplankton growth, primary and bacterial productivity was generally uncoupled; however, shifts in bacterial community diversity were observed in bioassays amended with either P or NP. We suggest that climate-associated increases in phytoplankton production and concomitant shifts in diversity will influence MDV bacterial community structure by altering the availability and composition of autochthonous carbon for heterotrophic production.
KeywordsAlgal–bacteria interactions Climate change McMurdo Dry Valleys Nutrient bioassay Primary production
The authors thank the McMurdo LTER, Antarctic Support Contract (Lockheed Martin), and Petroleum Helicopters Inc., for logistical assistance in the field. We thank the Center for Bioinformatics and Functional Genomics at Miami University for assistance with Illumina sequencing. This work was supported by NSF Office of Polar Programs Grant OPP-1056396.
- ACI Assessment (2005) Arctic climate impact assessment (ACIA). In: Symon C, Arris L, Heal B (eds). Cambridge University Press, New YorkGoogle Scholar
- Bowman JS, Vick-Majors TJ, Morgan-Kiss RM, Takacs-Vesbach C, Priscu JC (2016) Microbial community dynamics in two polar extremes: the lakes of the McMurdo Dry Valleys and the West Antarctic Peninsula Marine Ecosystem. Bioscience (in press)Google Scholar
- Hammer Ø, Harper DT, Ryan PD (2001) PAST: paleontological statistics software package for education and data analysis. Palaeontol Electron 4:9Google Scholar
- Obryk MK, Doran PT, Friedlaender AS, Gooseff M, Li W, Morgan-Kiss R, Priscu JC, Schofield O, Stammerjohn SE, Steinberg DK, Ducklow HW (2016) Responses of Antarctic marine and freshwater ecosystems to changing ice conditions. Bioscience (in press)Google Scholar
- Priscu JC (1991) Variation in light attenuation by the permanent ice cap of Lake Bonney during spring and summer. Antarct J US 26:223–224Google Scholar
- Rier ST, Stevenson RJ (2001) Relation of environmental factors to density of epilithic lotic bacteria in 2 ecoregions. Relation 20:520–532Google Scholar
- Sieburth JM, Keller MD (1989) Methylaminotrophic bacteria in xenic nanoalgal cultures: incidence, significance, and role of methylated algal osmoprotectants. Biol Ocean 6:383–395Google Scholar