An empirical model using dissolved oxygen as an indicator for eutrophication at a regional scale

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

“…Metrics were based on work by Coffin et al (submitted), which found that hypoxia (proportion of time below 4 mg/L), dissolved oxygen supersaturation (proportion of time above 10 mg/L), and the coefficient of variation of dissolved oxygen were all predicted by water residence time and nitrate loading. Additionally, metrics for the proportion of time <2 mg/L, <6 mg/L, and >15 mg/L were incorporated for greater resolution of sites that were minimally and maximally impacted by nutrients (Miller et al 2002;Landman et al 2005;Riedel et al 2014;Coffin et al submitted). The duration of 48 h was selected because effects from hypoxia prior to invertebrate sampling would likely still be evident , and although not investigated directly in this manuscript, the impacts on behaviour and survivorship can occur after extended exposure to hypoxia (Miller et al 2002;Riedel et al 2014).…”

“…The increase in productivity brought on by nutrient enrichment leads to the displacement of seagrasses by macroalgae and eventually the development of hypoxia (Valiela et al 1997;Larkum et al 2006;Burkholder et al 2007). Algal proliferation exaggerates the normal diurnal cycle of photosynthesis-driven elevated dissolved oxygen during the day and respiration-driven decreased dissolved oxygen at night, resulting in supersaturation and hypoxia, respectively (Lovato et al 2013;Coffin et al submitted). Ultimately, macroalgae become space limited and begin to shade themselves and decompose, depressing dissolved oxygen concentration further (Valiela et al 1997;Larkum et al 2006;Burkholder et al 2007).…”

Inorganic nitrogen has a dominant impact on estuarine eelgrass distribution in the Southern Gulf of St. Lawrence, Canada

“…Temperature values were collected half hourly from dissolved oxygen loggers in the same area from May–August (mean and range presented). Data were adapted from Coffin et al (, b ) with the exception that nitrate‐N loading at Bouctouche, Cocagne, and Kouchibouguac were updated with more recent data.…”

“…Nutrient loading, water chemistry, and substrate particle size and organic matter data were available from other studies (Coffin et al , b ) and are presented in Table . The loading estimates for the New Brunswick estuaries (Cocagne, Bouctouche, and Kouchibouguac) were revised from these studies with nitrate data that became available since those studies were published.…”

“…Watersheds in the Southern Gulf often experience intense agricultural land‐use (> 50% of land area) and consequently they are typified by high levels of external nitrogen loading (Bugden et al ; Jiang et al ). Reduced dissolved oxygen, including frequent anoxic events, is observed on an annual basis in many estuaries (Coffin et al ) impacting invertebrate (Coffin et al , ) and fish communities (Schein et al ). Watersheds with intensive agriculture also experience high rates of erosion leading to high total suspended solids that also have the potential to impact the estuary (Alberto et al ; Sirabahenda et al ).…”