Predicted aquatic and human health risks associated with the presence of metals in the Syr Darya and Shardara Reservoir, Kazakhstan.

Due to the decline of the Aral Sea fishery and recent efforts to expand the fisheries sector in Kazakhstan for both local consumption and global export, there is a need to sustain other fisheries in the area, including the Shardara Reservoir, which lies in the Syr Darya basin. Metals are present in the Syr Darya; yet, their impacts on fishery and consumer health remain unclear. Thus, the objectives of this study were to evaluate: 1) the potential impacts of metals on Syr Darya basin fish and 2) the human health risks posed by consumption of Shardara Reservoir fish. The health of the fishery was assessed by comparing surface water metal concentrations to maximum permissible concentrations (MPCs), calculating water quality index (WQI) and degree of contamination (Cd) values, and evaluating gene expression biomarker responses in wild-caught roach (Rutilus rutilus). To assess the risk to consumers, metal concentrations in roach were used to calculate hazard quotients (HQs) and hazard indices (HIs). Water concentrations of Cu, Fe, Mn, Se, Sr and V exceeded MPCs and all sites were classified as highly polluted based upon WQI and Cd values. This, along with site-specific differences in the expression of genes associated with xenobiotic metabolism and oxidative stress in roach, indicates potential risks to the fishery. Though all HQs and HIs were below 1 indicating a lack of significant risk to consumers, Pb levels in roach exceeded MPCs for safe consumption indicating a potential risk. Given the potential risks to the fishery and consumers, the development of pollution monitoring and management programs are warranted. The work presented here provides initial monitoring data that can be used to aid such efforts and also underscores the need to identify environmental stressors that may thwart the anticipated growth of fisheries in this region.

Legacy and current pesticide residues in Syr Darya, Kazakhstan: Contamination status, seasonal variation and preliminary ecological risk assessment.

The Syr Darya is one of two major rivers in Central Asia supplying critical fresh water to the Aral Sea. In spite of the river's importance and agriculturally-intensive history, few studies have provided a modern evaluation of and the occurrence of pesticide residues potential effects to aquatic life. The primary goal of this investigation was to determine seasonal variations in ambient concentrations of modern and legacy pesticides in bottom sediment and water of the Syr Darya in Kazakhstan (KZ) downstream from an agriculturally-intensive watershed in Uzbekistan. Grab samples and passive samplers were used at five remote sampling stations during June 2015 to provide a baseline for ecotoxicological evaluation. Results were compared with samples collected during and after the agricultural growing season. Polar organic chemical integrative samplers (POCIS) were used in June and calibrated for time-weighted average concentrations of current use pesticides. Among legacy chlorinated pesticides measured in grab samples from the river, lindane (γ-HCH) was detected most frequently with the highest concentrations occurring during June. For all the sampling events, residues of lindane (γ-HCH) ranged from 0.014 to 0.24 µg/L detected in water samples, are among the highest concentrations reported for rivers globally. Concentrations of γ-HCH, p,p'-DDE and dieldrin were highest in October when dieldrin concentrations approached 0.4 µg/L. Sources of legacy pesticides may be either illicit upstream use or evidence of previous atmospheric contamination of glacial meltwater. Chronic exposure to these residues may lead to ecological risk to lower order organisms in both the sediment and water column.

Maternally derived Cu tolerance in larval fathead minnows: how long does it persist?

Fathead minnow Pimephales promelas larvae were produced by either copper (Cu)-exposed or naïve females and then subjected to a 96 h survival test using Cu concentrations of 400 and 800 microg l(-1). Three survival challenges were conducted: the first survival test featured 0 day-old larvae while the second and third featured 8 and 15 day-old larvae, respectively. The results of this study show that maternally derived Cu tolerance was relatively short-lived as it persisted for <8 days.

Sublethal identification of susceptible individuals: using swim performance to identify susceptible fish while keeping them alive.

One branch of ecotoxicology has focused on identifying genetic markers in fish that are associated with susceptibility to toxic compounds. In laboratory studies, a common approach has been to compare the genetic variation in fish that die first in time-to-death studies to that found in fish that live longer or survive the exposure. Studies of this kind would benefit from the ability to identify living individuals as susceptible, as these individuals could then be used to answer currently unanswerable questions. The purpose of this mini-review is to suggest that post-exposure swim performance can be used to sublethally discriminate between susceptible and resistant individual fish after these fish have been exposed to environmental stressors, particularly heavy metals.

Morphological and physiological correlates with swimming performance in juvenile largemouth bass.

Winter- and summer-acclimatized largemouth bass (Micropterus salmoides) were collected from hatchery ponds in eastern Colorado during late winter and midsummer, then challenged with two prolonged swimming performances (step test and constant-velocity endurance). Variation in the step test performances was significantly correlated with variation in the endurance performances in the winter-acclimatized but not in the summer-acclimatized fish. Fourteen physiological and morphological traits were measured on each fish, and correlations among these traits and swimming performance were tested. None of the traits measured were correlated with performance variation in both the winter- and summer-acclimatized fish. The only significant correlate with swimming performance in the summer-acclimatized fish was white muscle lactate dehydrogenase activity (n = 19). Six of the seven factors correlating with winter swimming performance (n = 18-19) could be divided into two categories: traits associated with fasting (condition factor and liver enzymatic activity) and those associated with oxygen delivery (heart mass, heart and red muscle cytochrome oxidase activity). The results of this study suggest that morphological and physiological correlates of swimming performance in juvenile largemouth bass are profoundly influenced by seasonal variation.