Incubation of lake whitefish (Coregonus clupeaformis) embryos in cooling water discharge and the impacts of fluctuating thermal regimes on development

Abstract

Thermal discharges released from industrial cooling water systems represent a potential environmental risk to fish species that spawn in nearshore waters. We investigated the impacts of in situ incubation of lake whitefish (Coregonus clupeaformis) embryos in the vicinity of a nuclear generating station. Over 3 consecutive years, fertilized embryos were deployed in Lake Huron using custom-built incubation chambers coupled with data loggers to monitor water temperature. Temperatures at sites in the vicinity of the thermal discharge were significantly elevated compared with reference locations, with mean winter temperatures up to 3 °C warmer. Temperatures were also more variable at these sites, with a significantly greater daily temperature range and rate of change. Embryos developing at discharge sites were significantly larger with smaller yolks than those from the reference stations, suggesting an advanced growth. This increased growth was supported by thermal data, with discharge sites predicted to be more than 10% advanced based on growth rate modelling. These temperature changes and increase in development rate are below thresholds for embryonic mortality but could potentially impact posthatch larval survival.

Impacts of temperature, morpholine, and chronic radiation on the embryonic development of round whitefish (Prosopium cylindraceum)

“…This was very similar to the effects of seasonal temperatures on lake whitefish (Lim et al 2017). Both lake and round whitefish embryos from constant temperature regimes had delayed median hatch, likely caused by the lack of warming periods near the end of development (Patrick et al 2013;Thome et al 2016;Lim et al 2017;present study). In agreement with Patrick et al (2013), round whitefish embryos reared with faster (2 8C/wk) warming periods reached median hatch relatively more quickly (Table 1), with smaller hatch windows (Supplemental Data, Values represent the mean of 5 replicates (days 0 and 1) or 3 replicates (days 2 and 3).…”

“…However, achieving an approximately 1 °C temperature elevation with temperature spikes alone is unlikely in natural water bodies, because round whitefish embryos would require very frequent (e.g., 3 °C spikes 6 times/d) and/or very large (e.g., 15 °C spikes 1 time/d) 1‐h temperature spikes throughout the entirety of development. In addition, it is unlikely that all round whitefish spawning occurs within the range of thermal plumes, which is probably <5 km from once‐through cooling discharge sites (Thome et al ). Thus, in line with our predictions, current levels of temperature spikes from once‐through cooling processes are unlikely to have significant effects on round whitefish embryogenesis.…”

“…The maximum temperature of 15 8C was chosen because it is roughly in between hatching and summer temperatures (Armstrong et al 1977). Although more representative of a very warm spring compared with previous studies (Griffths, 1980;Patrick et al 2013;Thome et al 2016), the rapid warming used in the present study allowed for larvae to quickly reach temperatures where they displayed foraging/feeding behaviors. Beginning at 5 to 10 dph (based on visual inspection of yolk sac size and foraging behavior), larvae were fed crushed fish pellets (Otohime Larval Fish Diet; Marubeni Nisshin Feed) every 2 to 3 d, followed 1 h later by 100% water change.…”

Plastic responses to diel thermal variation in juvenile green sturgeon, Acipenser medirostris

“…Aquatic ectotherms must contend with increasing thermal variability as habitat temperatures are continually modified by anthropogenic activities (Thome et al, 2016;Verones et al, 2010). Riverine thermal regimes have been extensively altered by channelization, flow regulation, and the installation of instream structures (Caissie, 2006;Casado et al, 2013).…”

“…Riverine thermal regimes have been extensively altered by channelization, flow regulation, and the installation of instream structures (Caissie, 2006;Casado et al, 2013). The operation of waterway infrastructure can abruptly raise or lower daily and seasonal water temperatures by 5-15°C, with alterations often persisting for hundreds of kilometres downstream (Lugg and Copeland, 2014;Raptis et al, 2016;Thome et al, 2016). The major sources of thermal pollution are injections of heated effluent from thermoelectric power plants and inputs of cold, hypolimnetic water from dams (Caissie, 2006).…”