Flooding and arsenic contamination: Influences on ecosystem structure and function in an Appalachian headwater stream

Abstract

We investigated the influence of flooding and chronic arsenic contamination on ecosystem structure and function in a headwater stream adjacent to an abandoned arsenic (As) mine using an upstream (reference) and downstream (mine-influenced) comparative reach approach. In this study, floods were addressed as a pulse disturbance, and the abandoned As mine was characterized as a press disturbance. We further addressed chronically elevated As concentrations as a ramp disturbance, in which disturbance intensity was ramped by increasing proximity to the As source. Stream ecosystem structure and biogeochemical functioning were characterized monthly over a period ranging from July to December 2004. Influence of the press disturbance was evident in the mine-influenced reach, where As concentrations (254 6 39 mg L 21 ) were more than 30 times higher than in the reference reach (8 6 1 mg L 21 ). However, in almost all cases the presence of the abandoned As mine appeared to exert little influence on reach-scale measures of ecosystem structure and function (e.g., organic matter [OM] standing crops, phosphorus [P] uptake). Conversely, floods significantly influenced OM standing stock in both study reaches. Interactions between press and pulse disturbances influenced P uptake in the mine-influenced reach. Within the mine-influenced reach, P uptake across a gradient of As concentrations correlated with Michaelis-Menton models of enzyme kinetics in the presence of a competitive inhibitor. These results indicate that As competitively inhibits P uptake by microbial assemblages.

The evolving legacy of disturbance in stream ecology: concepts, contributions, and coming challenges

“…For example, storms transport significantly more sediment to streams in deforested (Keim andSchoenholtz 1999, Swank et al 2001) or burned (Vieira et al 2004) watersheds than in undisturbed watersheds, and invertebrate populations can be less resilient to repeated flooding in streams draining agricultural watersheds than in forested streams because of loss of refugia Quinn 2003, Parkyn andCollier 2004). Most disturbance interaction studies have focused on structural biotic consequences, but such interactions also should affect functional responses, such as nutrient retention (Lottig et al 2007).…”

Press-pulse: a general theory of mass extinction?

“…In contrast, press events are long-term stresses that may not cause immediate mortality, but instead alter population densities and shift the community into a new equilibrium. In studies of living systems, the press-pulse paradigm has been broadly applied to the marine ben thos (Elias et al 2005;Morello et al 2005;Lilley and Schiel 2006;Scheibling and Gagnon 2006), freshwater communities (Marshall and Bailey 2004;Parkyn and Collier 2004;Lottig et al 2007;Alexander et al 2008), soil inverte brates (Bengtsson 2002), terrestrial animals (Alterio and Moller 2000), plants (Inchausti 1995), and conservation theory (Parasiewicz 2007).…”

Influence of land use on stream ecosystem function in a Mediterranean catchment

“…, 2006) and other forms of water pollution that inhibit biological communities responsible for nutrient uptake (Newbold et al. , 2006; Lottig et al. , 2007).…”

“…Past research shows that some activities reduce retention efficiency (i.e. retention relative to nutrient flux), such as channel modification (Sweeney et al, 2004;Bukaveckas, 2007), nutrient loading (Martí et al, 2004;Bernot et al, 2006;Newbold et al, 2006) and other forms of water pollution that inhibit biological communities responsible for nutrient uptake Lottig et al, 2007). Conversely, retention efficiency may increase with other human activities, such as riparian vegetation removal, through increases in light for primary producers (Sabater et al, 2000).…”