Increased agricultural land use leads to accelerated erosion and deposition of fine sediment in surface water. Monitoring of suspended sediment yields has proven challenging due to the spatial and temporal variability of sediment loading. Reliable sediment yield calculations depend on accurate monitoring of these highly episodic sediment loading events. This study aims to quantify precipitation-induced loading of suspended sediments on Prince Edward Island, Canada. Turbidity is considered to be a reasonably accurate proxy for suspended sediment data. In this study, turbidity was used to monitor suspended sediment concentration (SSC) and was measured for 2 years (December 2012-2014) in three subwatersheds with varying degrees of agricultural land use ranging from 10 to 69 %. Comparison of three turbidity meter calibration methods, two using suspended streambed sediment and one using automated sampling during rainfall events, revealed that the use of SSC samples constructed from streambed sediment was not an accurate replacement for water column sampling during rainfall events for calibration. Different particle size distributions in the three rivers produced significant impacts on the calibration methods demonstrating the need for river-specific calibration. Rainfall-induced sediment loading was significantly greater in the most agriculturally impacted site only when the load per rainfall event was corrected for runoff volume (total flow minus baseflow), flow increase intensity (the slope between the start of a runoff event and the peak of the hydrograph), and season. Monitoring turbidity, in combination with sediment modeling, may offer the best option for management purposes.

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Abstract:Increased sedimentation in surface waters due to anthropogenic activities can lead to the deterioration of salmonid spawning habitat through infiltration of excessive fine sediment into redds. This study assessed the effects of sediment on salmonid reproductive habitat on Prince Edward Island, Canada by evaluating egg survival and fry length using brook trout egg in situ incubations. In-stream egg incubators were buried in the substrate of streams in three watersheds with between 10 and 69% agricultural land-use during 2012-2013 and 2013-2014. Accumulated incubator sediment load and associated particle size, incubator organic matter and stream parameters temperature, velocity, bed sediment and particle size were measured over the period of study. There was no significant difference in embryo survival among watersheds. Survival was not related to fine sediment; instead, it increased with higher average temperature that was in turn associated with the presence of groundwater upwelling in the stream. The size of the fry was also not significantly different between watersheds with varying agricultural activity. Fry length was most strongly related to sediment organic matter content. Brook trout are widespread in PEI rivers, including in many rivers that have high sediment loads due to intensive agricultural land use. This species may avoid the adverse effect of fine sediment through their natural adaptation of using groundwater upwelling for spawning. Sedimentation is of particular concern on PEI because of its potential to impact spawning habitat for native salmonids, namely brook trout and Atlantic salmon (Merz et al., 2004;Curry and MacNeill, 2004). While brook trout remain widespread on PEI, Atlantic salmon is only present in about one third of its former rivers (Cairns and MacFarlane, 2015) and its decline has been attributed to a variety of factors, including excessive sedimentation (Guignion et al., 2010). In contrast to the situation on PEI, there is evidence of the decline of brook trout in other parts of the world that has been attributed to landscape alteration (Stranko et al., 2008). Thus, the study of the impacts of sedimentation on brook trout spawning can provide some insight into the persistence of this species on PEI despite the seemingly adverse conditions. The objective of this study was to assess the effects of deposited sediment on brook trout survivorship and fry length on PEI. This study tested the hypothesis that sediment is a limiting factor in salmonid egg survival to hatching and emergence. Survival was assessed by placing in-stream egg incubators in three watersheds with varying degrees of agricultural land-use during two separate spawning seasons. Eggs were monitored for hatching and swimup over the early spring months and the relationship between survival and fine sediment accumulated within the incubators was assessed. Keywords Materials and Methods Study sitesThree rivers on PEI with varying degrees of agricultural landuse within the watershed were selected for the study: Whe...