Acute and chronic toxicity of nitrate to fat greenling (Hexagrammos otakii) juveniles

Abstract

We evaluated the acute and chronic toxicity of nitrate to juvenile fat greenling Hexagrammos otakii. The 24‐, 48‐, 72‐, and 96‐hr LC50s of nitrate to 1.91 ± 0.7 g greenlings were 2,741, 2,413.5, 2,357.6, or 2,339.2 mg/L nitrate‐N, respectively. Greenlings (6.55 ± 1.83 g) were exposed to 5 mg/L (control) and 157 mg/L for 4 weeks in a recirculating aquaculture system. After 4 weeks, length, weight, feed conversion ratio, and specific growth rate were significantly (p < 0.05) lower for nitrate‐exposed fish than for control fish. Elevated nitrate exposure was associated with decreased plasma hemoglobin concentration and red blood cell count. Our results demonstrate that nitrate poses a threat to greenlings and provide information that is useful for establishing water quality criteria for early life stages of this cultured fish. The sensitivity of greenlings to elevated NO3− should be evaluated at other life stages to determine how chronic exposure might impact survival, growth, health, reproductive success, and harvest quality.

Exposure to Nitrate Increases Susceptibility to Hypoxia in Fish

“…DOI: https://doi.org/10.1086/713252 kPa) and their blood-carrying capacity (lower hemoglobin concentration, HB]; and hematocrit, HCT) was marginally impaired. Exposure to other nitrogenous waste products (nitrite, ammonia) have also been shown to disrupt regular cardiorespiratory function (causing hyperventilation, tachycardia; Aggergaard and Jensen 2001; Williams et al 1997), while nitrate exposure has been shown to lower the blood-carrying capacity of various fishes via the formation of methemoglobin, and reductions in functional [HB] and HCT (Aboagye and Allen 2014;Gomez Isaza et al 2020b;Monsees et al 2017;Yang et al 2019). Indeed, in our previous study, we found that silver perch exposed to identical nitrate concentrations (50 and 100 mg NO 3 − L -1 ) experienced significant methemoglobin formation (20 -34% methemoglobin in the blood) and indicates that silver perch are susceptible long-term nitrate exposures (Gomez Isaza et al 2021).…”

“…reduction in the interlamellar cell mass; Borowiec et al 2015; Dhillon et al 2020a). Primarily, nitrate can results in the oxidation of hemoglobin to a nonoxygen binding form, methemoglobin, which generates tissue hypoxia and can be fatal at extreme levels (Camargo et al 2005;Monsees et al 2017;Yang et al 2019). High levels of nitrate also reduce concentrations of functional hemoglobin, lower hematocrit, and alter hemoglobinoxygen binding affinities (i.e.…”

“…High levels of nitrate also reduce concentrations of functional hemoglobin, lower hematocrit, and alter hemoglobinoxygen binding affinities (i.e. reduce affinity for oxygen at the gills; Gomez Isaza et al 2021; Monsees et al 2017;Yang et al 2019), effectively lowering blood oxygen carrying capacity (Gomez Isaza et al 2020b;Monsees et al 2017), raising energetic costs (Gomez Isaza et al 2018, 2020c and leading to respiratory collapse and disrupted physiological function (Jensen 2003;Jensen et al 1987). As such, organisms exposed to elevated nitrate concentrations and hypoxia are confronted with both environmental hypoxia and hypoxemia and may be unable to adequately respond to both stressors (Rodgers et al 2020).…”

Thermal acclimation offsets the negative effects of nitrate on aerobic scope and performance

“…When water-nitrate concentrations are elevated, nitrate enters the body of aquatic animals passively through the gill epithelium and accumulates in plasma (Stormer et al, 1996). Inside the body, nitrate can lower concentrations of functional haemoglobin, via the oxidation of the central iron ion (Fe 2+ to Fe 3+ ), to a non-oxygen binding form, methaemoglobin (Monsees et al, 2017;Yang et al, 2019). Elevated concentrations of methaemoglobin cause an inherent loss of oxygen transport capacity (i.e.…”

Effects of Hydraulic Retention Time and Influent Nitrate-N Concentration on Nitrogen Removal and the Microbial Community of an Aerobic Denitrification Reactor Treating Recirculating Marine Aquaculture System Effluent

“…Nitrogenous contamination of surface waters is a serious environmental problem, causing eutrophication of rivers, lakes, and near-shore marine environments [1,2] and raising the likelihood of toxic algal blooms in receiving waters [3,4]. Accumulation of nitrogenous wastes is also a problem in aquaculture systems [5], posing toxicity to cultured organisms [6][7][8][9]. Microbially mediated nitrification in biofilters is commonly used to convert ammonia-N to nitrite-N and further to nitrate-N [10].…”