Resuspension by fish facilitates the transport and redistribution of coastal sediments

Abstract

Oxygen availability restricts groundfish to the oxygenated, shallow margins of Saanich Inlet, an intermittently anoxic fjord in British Columbia, Canada. New and previously reported 210 Pb measurements in sediment cores compared with flux data from sediment traps indicate major focusing of sediments from the oxygenated margins to the anoxic basin seafloor. We present environmental and experimental evidence that groundfish activity in the margins is the major contributor to this focusing. Fine particles resuspended by groundfish are advected offshore by weak bottom currents, eventually settling in the anoxic basin. Transmittance and sediment trap data from the water column show that this transport process maintains an intermediate nepheloid layer (INL) in the center of the Inlet. This INL is located above the redox interface and is unrelated to water density shifts in the water column. We propose that this INL is shaped by the distribution of groundfish (as resuspension sources) along the slope and hence by oxygen availability to these fish. We support this conclusion with a conceptual model of the resuspension and offshore transport of sediment. This fish-induced transport mechanism for sediments is likely to enhance organic matter decomposition in oxygenated sediments and its sequestration in anoxic seafloors.

An hypoxia‐tolerant flatfish: consequences of sustained stress on the slender sole Lyopsetta exilis (Pleuronectidae) in the context of a changing ocean

“…() reported that over 75% of slender sole stomachs in Strait of Georgia had small crustaceans such as copepods. We often saw slender sole darting off bottom, especially in swarms of migrating plankton; these movements resuspended sediments to the point of creating dense turbidity layers near bottom in severe (<0.5 ml l −1 ) hypoxia (Katz et al ., ; Yahel et al ., ). Hypoxia intensity on the Saanich margins changes over the year, and mobile animals show strong responses as zooplankton adjust the depth of their diurnal migration (Sato et al ., ) while epibenthic animals move up and down slope (Chu & Tunnicliffe, ).…”

Oxygen limitations on marine animal distributions and the collapse of epibenthic community structure during shoaling hypoxia

“…() and Katz et al . () but with an extension into shallower depths (~45 m). This transect was repeated once every year until 2012, and in 2013, it was repeated three times at different times of the hypoxia cycle: after spring renewal (May), after a full summer of deoxygenation (September), and during the onset of oxygen recovery in the fall (October).…”

“…1b, Table S1) using remotely operated vehicles (ROV). This transect (~3 km length) begins in the middle of the inlet (~190 m depth) and is based on the one described in Yahel et al (2008) and Katz et al (2012) but with an extension into shallower depths (~45 m). This transect was repeated once every year until 2012, and in 2013, it was repeated three times at different times of the hypoxia cycle: after spring renewal (May), after a full summer of deoxygenation (September), and during the onset of oxygen recovery in the fall (October).…”

Ecophysiological limits to aerobic metabolism in hypoxia determine epibenthic distributions and energy sequestration in the northeast Pacific ocean

“…Although slender sole is not a commercially valuable species (due to their small size), they resuspend large amounts of bottom sediments, which contribute to substantial fluxes in nutrient recycling and transport (Yahel et al 2008;Katz et al 2009Katz et al , 2012. High abundance and fidelity to low [O 2 ] env (Chu and Tunnicliffe 2015a) also suggest that they could be an important indicator species of hypoxic waters within their habitat range.…”