Properties and distribution of sediment in the Salton Sea, California: an assessment of predictive models

The Salton Sea is the largest lake, on a surface area basis, in California (939 km(2)). Although saline (> 44 g/l) and shallow (mean depth approximately 9.7 m), it provides valuable habitat for a number of endangered species. The distribution of sediments and their properties within the Salton Sea are thought to have significant influence on benthic ecology and water quality. Sediment properties and their distribution were quantified and compared with predicted distributions using several sediment distribution models. Sediment samples (n = 90) were collected using a regular staggered-start sampling grid and analyzed for water content, organic carbon (C), calcium carbonate, total nitrogen (N), total phosphorus (P), organic phosphorus, and other properties. Water content, total N, and total and organic P concentrations were all highly correlated with organic C content. The organic C concentration showed a non-linear increase with depth, with low organic C contents (typically 1-2%) present in sediments found in depths up to 9 m, followed by a strong increase in organic C at greater depths (to about 12% at 15 m depth). The models of Hakanson, Rowan et al., Blais and Kalff, and Carper and Bachmann yielded very different predicted critical depths for accumulation (10.5-22.8 m) and areas of accumulation (0-49.5%). Hakanson's dynamic ratio model more reasonably reproduced the observed zone of elevated organic C concentrations in the Salton Sea than either exposure- or slope-based equations. Wave theory calculations suggest that strong winds occurring less than 1% of the time are sufficient to minimize accumulation of organic matter in sediments that lie at depths less than 9 m in this system.