Ecological Modelling 221 (2010) 1184–1193 Contents lists available at ScienceDirect Ecological Modelling journal homepage: www.elsevier.com/locate/ecolmodel Physiochemical properties influencing biomass abundance and primary production in Lake Hoare, Antarctica Radu Herbei b,∗ , W. Berry Lyons b , Johanna Laybourn-Parry a , Christopher Gardner b , John C. Priscu c , Diane M. McKnight d a Institute for Antarctic and Southern Ocean Studies, University of Tasmania, Hobart, Australia b The Ohio State University, Columbus, OH 43210, United States c Montana State University, Bozeman, MT 59717, United States d INSTAAR, University of Colorado, Boulder, CO 80309, United States article info Article history: Received 22 July 2009 Received in revised form 14 December 2009 Accepted 18 December 2009 Available online 26 January 2010 Keywords: Lake Hoare MCM-LTER Bayesian methods Correlation analysis Gaussian Markov random fields abstract The perennially ice-covered, closed basin lakes in the McMurdo Dry Valleys respond rapidly to environ- mental changes, especially climate. For the past 15 years, the McMurdo Dry Valleys Long-Term Ecological Research (MCM-LTER) program has monitored the physical, chemical and biological properties of the lakes in Taylor Valley. In order to better assess the physiochemical controls on the biological process within one of these lakes (Lake Hoare), we have used vertical profile data to estimate depth-dependent correlations between various lake properties. Our analyses reveal the following results. Primary produc- tion rates (PPR) are strongly correlated to light (PAR) at 12–15 m and to soluble reactive phosphorus (SRP) at 8–22 m. Chlorophyll-a (CHL) is also positively correlated to PAR at 14 m and greater depths, and SRP from 15 m and greater. This preliminary statistical analysis supports previous observations that both PAR and SRP play significant roles in driving plant growth in Lake Hoare. The lack of a strong relation- ship between bacterial production (BP) and dissolved organic carbon (DOC) is an intriguing result of the analysis. Published by Elsevier B.V. 1. Introduction The McMurdo Dry Valleys of Antarctica (76 ◦ 30 ′ S to 78 ◦ 30 ′ S) from the largest ice-free area on the continent. In Taylor Valley, the mean annual temperature ranges from -14.8 ◦ C to -30 ◦ C with 10–100 days when average temperatures exceed 0 ◦ C, see Doran et al. (2002). The average net annual precipitation are less than 5 cm of water equivalent, see Fountain et al. (1999) and Witherow et al. (2006). Yet Taylor Valley contains perennial ice-covered lakes that are maintained by the input of glacier melt flows from 4 to 10 weeks per year (Fountain et al., 1999). Taylor Valley is a major east–west trending valley within this landscape and has been the primary site of the McMurdo Dry Valleys Long-Term Ecological Research (MCM-LTER) program since 1993. Despite extremely climatic con- ditions, these ice-covered lakes contain a habitat where microbial life exists throughout the year (Roberts and Laybourn-Parry, 1999; Priscu et al., 1999; Marshall and Laybourn-Parry, 2002). Because ∗ Corresponding author. Tel.: +1 614 247 7487; fax: +1 614 292 2096. E-mail addresses: herbei@stat.osu.edu (R. Herbei), lyons.142@osu.edu (W. Berry Lyons), Jo.Laybourn-Parry@utas.edu.au (J. Laybourn-Parry), gardner.177@osu.edu (C. Gardner), jpriscu@montana.edu (J.C. Priscu), diane.mcknight@colorado.edu (D.M. McKnight). of their permanent ice covers, physical mixing is minimized and diffusion and the seasonal input of meltwater beneath the ice cov- ers are the primary controls of chemical variation in these lakes (Spigel and Priscu, 1998; Foreman et al., 2004). Taylor Valley lakes have been termed “end-members” among the world’s lakes, in part because of their permanent ice covers (Fritsen and Priscu, 1999). Lake Hoare is the freshest water lake of the Taylor Valley lakes and it has not been greatly impacted by cryocentration as the other Taylor Valley lakes have been (Doran et al., 1994; Lyons et al., 1998). Every year since 1993 limnological data have been collected from Lake Hoare by MCM-LTER scientists. These data include biological, chemical and physical information which are all part of the long- term monitoring program used to determine ecosystem change through time. It is evident from studies on these lake systems that an integrated knowledge of the biological, chemical and physical factors is required to understand the biogeochemical dynamics of these ecosystems. Previous research has demonstrated that these lakes are very oligotrophic and have important mixotrophic com- ponents (Priscu et al., 1999); however, gaps in knowledge remain, especially in linking how these ecosystems responds to physical drivers. In order to better assess the physiochemical controls on biological processes within Lake Hoare we have developed a sta- tistical model which allows us to study the relationship between various environmental properties. 0304-3800/$ – see front matter. Published by Elsevier B.V. doi:10.1016/j.ecolmodel.2009.12.015