Depth as an organizer of fish assemblages in floodplain lakes

Abstract

Depth reduction is a natural process in floodplain lakes, but in many basins has been accelerated by anthropogenic disturbances. A diverse set of 42 floodplain lakes in the Yazoo River Basin (Mississippi, USA) was examined to test the hypothesis of whether depth reduction was a key determinant of water quality and fish assemblage structure. Single and multiple variable analyses were applied to 10 commonly monitored water variables and 54 fish species. Results showed strong associations between depth and water characteristics, and between depth and fish assemblages. Deep lakes provided less variable environments, clearer water, and a wider range of microhabitats than shallow lakes. The greater environmental stability was reflected by the dominant species in the assemblages, which included a broader representation of large-body species, species less tolerant of extreme water quality, and more predators. Stability in deep lakes was further reflected by reduced among-lake variability in taxa representation. Fish assemblages in shallow lakes were more variable than deep lakes, and commonly dominated by opportunistic species that have early maturity, extended breeding seasons, small adult size, and short lifespan. Depth is a causal factor that drives many physical and chemical variables that contribute to organizing fish assemblages in floodplain lakes. Thus, correlations between fish and water transparency, temperature, oxygen, trophic state, habitat structure, and other environmental descriptors may ultimately be totally or partly regulated by depth. In basins undergoing rapid anthropogenic modifications, local changes forced by depth reductions may be expected to eliminate species available from the regional pool and could have considerable ecological implications.

Hierarchy in factors affecting fish biodiversity in floodplain lakes of the Mississippi Alluvial Valley

“…Percent of agricultural land may couple with the effects of depth to influence water quality variables. Lakes with high sedimentation rates would experience accelerated lake-shallowing and eventually be subject to environmental conditions typical of shallow lakes (i.e., increased turbidity, large fluctuations in DO) and an unfavorable shift in fish assemblage characteristics (Miranda 2010).…”

“…Likewise, primary and secondary variables may influence the fish assemblage (tertiary variables). For example, vertical stratification of temperature and dissolved oxygen concentrations are largely controlled by depth (Dake and Harleman 1969), whereas the presence of a fish species may be controlled by temperature and oxygen as well as by the diversity of habitat afforded by depth (Miranda 2010). Similarly, lake acidity is influenced by the relative position of the lake within the landscape; lakes over carbonate-based sediments show less impact of acidification than lakes over granite-based sediments , affecting species composition through water chemistry and through the location of the lake within the broader ecological environment.…”

Structural complexity and turbidity do not interact to influence predation rate and prey selectivity by a small visually feeding fish

“…In a floodplain, such changes can also be caused by shallowing, which tends to transform relatively clear complex habitats into turbid simple ones (e.g. Loverde- Oliveira et al 2009;Miranda 2011;Mormul et al 2012). …”

Influence of varying nutrient and pesticide mixtures on abatement efficiency using a vegetated free water surface constructed wetland mesocosm

“…[37,38] Water temperatures were indicative of climatic conditions of the study site (north Mississippi) during summer, with means ranging from 22.4 to 27.3 • C. [36,39] No outflow occurred from the wetland at any time during the study periods (28 July to 26 August 2009 and 1 to 30 September 2009) despite ∼ 162 mm total precipitation occurring from 28 July to 26 August and 188 mm total precipitation occurring from 1 to 30 September. Prior to both the first and second treatment periods, east and west section baseline pretreatment (27 July 2009 and 31 August 2009) nutrient and pesticide concentrations indicated low levels of N and P and very low to below detection limit concentrations of atrazine, S-metolachlor and permethrin (Supplemental Table 1 available online at http://dx.doi.org/10.1080/02757540.2013.861823).…”