Sedimentation effects on the benthos of streams and estuaries: a cross-ecosystem comparison

Abstract

Connected ecosystems can be detrimentally affected by the same stressor, such as occurs when excess fine sediment moves from streams into estuaries. However, no previous study has directly compared sedimentation effects across these ecosystems. Responses of benthic macroinvertebrate communities to sedimentation were predicted to vary between streams and estuaries, because of intersystem differences in the physical environment and representation of species traits. To compare these responses, fine terrigenous sediment was added simultaneously to replicated plots in stream-run habitats and the adjacent estuary. Although sediment addition to streams caused reduced invertebrate densities after 1 week, no changes in taxon richness or consistent changes in community structure were detected, and densities had recovered another week later. In contrast, sediment addition to estuarine sites caused large declines in invertebrate densities and changes in community structure, which remained evident at the innermost sites 16 days after addition. Across both systems, sedimentation effects were detectable only for some of the common taxa, and biological traits were not predictive of effects. The potential for more severe effects in estuaries should be considered when predicting the implications of land-use changes that may increase sedimentation, and when setting guidelines for maintaining stream and estuarine condition.

Rapid water quality change in the Elwha River estuary complex during dam removal

“…Studies have shown that deposition of as little as 3 mm of sediment is enough to alter benthic invertebrate communities (Lohrer et al ) and 9 cm of sediment can result in complete mortality and slow recovery (Norkko et al ). Once estuarine benthic communities have been altered by sedimentation events, recovery time may be longer than in adjacent riverine communities (Reid et al ). Changes in estuary productivity can reverberate through the food web and have lasting effects on the growth rates of salmon that experience suboptimal environmental conditions as juveniles (Morrongiello et al ).…”

Social–ecological connections across land, water, and sea demand a reprioritization of environmental management

“…As the point of entry of these sediments into the aquatic systems is mainly via the stream network, limits are set as freshwater standards. While there are considerable impacts of sediments on freshwaters (Burdon et al, 2013), the ecological impacts and potential for legacy effects are much stronger in coastal and estuarine ecosystems (Reid et al, 2011).…”

A novel approach to model exposure of coastal-marine ecosystems to riverine flood plumes based on remote sensing techniques

“…Nutrient enrichment of coastal waters has also been related to increased risk of coral bleaching (Wooldridge, 2009) and outbreaks of the reef-destroying crown-of-thorns starfish (COTS) (Brodie et al, 2005;Fabricius et al, 2010). Globally, land use change associated with agriculture, forestry, and urbanization have led to significant soil loss, resulting in increased sediment loads and turbidity of coastal waters (Croke and Hairsine, 2006;Thrush et al, 2004;Walling, 2006); in turn, these have been related to reduced coral recruitment (Hutchings et al, 2005), increased seagrass mortality (Cabaco et al, 2008), and declines in invertebrate densities (Reid et al, 2011). Pesticides are a major concern, particularly for sites adjacent to coastal catchments with intensive agriculture or forestry plantations, and have been related to dieback in mangroves, as well as reduced photosynthesis and expulsion of the symbiotic algae (bleaching) from corals (Duke et al, 2005;Haynes et al, 2007;Hutchings et al, 2005).…”