Nitrogen loadings to two small estuaries, Prince Edward Island, Canada: a 2‐year investigation of precipitation, surface water and groundwater contributions

Abstract

Abstract:In this research the dissolved inorganic nitrogen (DIN) loadings from direct precipitation, stream flow and groundwater discharge to two small estuaries located in Prince Edward Island (PEI), Canada, were quantified over a 2-year period. The two estuaries, like many around the world, exhibit deteriorating conditions that are believed to be related to excessive nitrogen transport from adjacent catchments. The significance of the groundwater transport pathway and the temporal variability of the loadings have not been previously investigated. The wet fraction of the atmospheric loading was quantified using available precipitation and DIN concentration records. Stream water entering the estuaries and the discharge from numerous shoreline springs, the predominate form of groundwater discharge, were monitored periodically during the study. The annual DIN loads delivered to both estuaries were dominated by streams, although groundwater discharge provided significant contributions of approximately 15-18%. Temporal variability of DIN loading was large, with monthly loads varying by a factor of 5; this variability was found to be primarily related to the variability of freshwater discharge. Concentrations of nitrate in stream water discharging to the estuaries and shoreline groundwater springs were similar in each catchment, suggesting that there was minimal differential attenuation during transport via these two pathways. The McIntyre Creek estuary had one of the highest normalized loads reported in the literature (1700 kg NO 3 -N/ha estuary/year), more than four-fold that of the Trout River estuary, and this result appears to be related to the larger percentage of land area used for potato production in the catchment. This study demonstrates that direct groundwater discharge to estuaries in PEI should not be ignored and that seasonal variations in loading may be important for managing DIN delivery to such estuaries.

Controls on Nitrate Loading and Implications for BMPs Under Intensive Potato Production Systems in Prince Edward Island, Canada

“…The dynamics of stream discharges are a good indicator of groundwater dynamics in PEI as it was previously shown that annual groundwater discharge contribution as base flow can amount to up to 80% of the streamflow on an annual basis (Danielescu et al ). Daily stream discharges (Environment Canada ) recorded between 2000 and 2010 at six hydrometric stations distributed in six watersheds across PEI with drainage areas ranging from 15 to 114 km 2 showed that the stream discharge follows the same dynamics across PEI (Figure A).…”

Impacts of hypoxia on estuarine macroinvertebrate assemblages across a regional nutrient gradient

“…Eelgrass (Z. marina), the local seagrass, is in decline in the region (DFO 2009), particularly in the upper reaches of Prince Edward Island (PEI) estuaries (Hitchcock et al 2017). Many PEI estuaries have agriculturally driven high nitrate-N loads (Danielescu et al 2007;Danielescu and MacQuarrie 2011), are dominated by sea lettuce (Ulva spp. ), and experience seasonal anoxia as a result (Bugden et al 2014).…”

Are floating algal mats a refuge from hypoxia for estuarine invertebrates?

“…and Atlantic silverside ( Menidia menidia (Linnaeus, 1766)), among others. Although nitrogen inputs from human waste and industry are low, nutrient inputs from agriculture can be extremely high, particularly in Prince Edward Island (PEI) (Danielescu & MacQuarrie, 2011; Schein et al, 2012; Bugden et al, 2014). Here, eutrophication manifests as the familiar gradient from inner algae- to outer seagrass-dominated habitat (Valiela et al, 1997; Deegan, 2002; Larkum, Orth & Duarte, 2006; Burkholder, Tomasko & Touchette, 2007), with many sites experiencing intermittent and sustained seasonal hypoxia/anoxia (concentrations of dissolved oxygen <2 mg/L and 0 mg/L, respectively (Bugden et al, 2014)) often lasting days.…”