Effects of chronic hypoxia and reduced temperature on survival and growth of burrowing mayflies, (Hexagenia limbata) (Ephemeroptera: Ephemeridae)

Abstract

Hexagenia nymphs are sensitive to hypoxia, and their abundance has been proposed as an ecosystem indicator for assessing the recovery from eutrophication of shallow, mesotrophic lakes. Acute oxygen tolerance limits are known for Hexagenia spp., but effects of prolonged exposure to sublethal levels of hypoxia are not. A series of 21-day laboratory experiments was conducted to determine the influence of hypoxic stress (range 2-12.6 mg/L dissolved oxygen) and temperature (range 4-20°C) on survival and growth of Hexagenia limbata nymphs. Oxygen and temperature together explained 89% of the variability in survival among H. limbata, and 71% of the variability in average growth. Survival increased with increasing oxygen concentration, reaching an asymptote at 7-8 mg/L. Survival increased with temperature to an asymptote at approximately 9.5°C. Higher temperatures magnified the effects of hypoxia on survival. Growth increased with both oxygen and temperature, and did not reach an asymptote at levels up to 12.6 mg/L oxygen and 20°C. Persistent, sublethal oxygen stress (concentrations <7 mg/L) and reduced temperature (<20°C) can influence both survival and size of H. limbata. Résumé : Les nymphes d'Hexagenia sont sensibles à l'hypoxie, et on a proposé d'utiliser leur abondance comme indicateur écosystémique pour évaluer le rétablissement après eutrophisation des lacs mésotrophes peu profonds. On connaît les limites de la tolérance à une concentration aiguë d'oxygène chez Hexagenia, mais pas les effets d'une exposition prolongée à des niveaux sublétaux d'hypoxie. Nous avons mené une série d'expériences de 21 jours en laboratoire pour déterminer l'influence du stress hypoxique (fourchette 2-12,6 mg/L d'oxygène dissous) et de la température (fourchette 4-20°C) sur la survie et la croissance des nymphes d'Hexagenia limbata. Combinés, l'oxygène et la température expliquaient 89% de la variabilité de la survie parmi les H. limbata et 71% de la variabilité de la croissance moyenne. La survie augmentait avec la concentration d'oxygène, pour atteindre une asymptote à 7-8 mg/L. La survie augmentait en fonction de la température pour atteindre une asymptote à environ 9,5°C. La hausse des températures amplifiait les effets de l'hypoxie sur la survie. La croissance augmentait en fonction à la fois de l'oxygène et de la température, et n'avait pas atteint une asymptote à des niveaux de 12,6 mg/L d'oxygène et 20°C. Un stress persistant et sublétal dû à la concentration de l'oxygène (<7 mg/L) et une réduction de la température (<20°C) peuvent avoir un effet sur la survie et sur la taille d'H. limbata.

The effect of mayfly (Hexagenia spp.) burrowing activity on sediment oxygen demand in western Lake Erie

“…populations in a variety of ways: increased mortality rates, differential mortality related to nymph sizes, slower growth rates, and decreased fecundity. Winter et al (1996) found increased mortality of nymphs under even light to moderate hypoxic conditions, decreased and even negative growth rates, and that small nymphs were less likely to survive hypoxia than larger nymphs, which would impact Hexagenia spp. abundances in the succeeding 2 years.…”

Impacts of Paleo-Oxygen Levels on the Size, Development, Reproduction, and Tracheal Systems of Blatella germanica

“…1) fits with results for other insects that have been studied ). The fruitfly D. melanogaster, beetles Z. morio, Tenebrio molitor, and Cotinis texana, the tobacco hornworm moth M. sexta and the mayfly Hexagenia limbata all demonstrate decreased body sizes when reared under hypoxia (Winter et al 1996;Peck and Maddrell 2005;Harrison et al 2009). The mechanisms behind the hypoxia-induced decrease in size are still poorly understood, though it has been shown in D. melanogaster that both cell size and cell number decrease in hypoxia (Peck and Maddrell 2005;Heinrich et al 2011).…”

Multispatial-scale variation in benthic and snag-surface macroinvertebrate assemblages in mid-continent US great rivers

“…A number of studies have shown the target taxa, especially mayflies, fingernail clams, and midges, to be ecologically important as fish and waterfowl food, biological indicators, and converters of phytoplankton and bacteria to higher energy pathways (Hoopes 1960;Fremling 1964Fremling , 1989Jude 1968;Ranthum 1969;Thompson 1973;Anderson et al 1978;Sandusky and Sparks 1979;Reice and Wohlenberg 1992;Rosenberg and Resh 1993;Winter et al 1996;Diggins and Stewart 1998;Schloesser and Nalepa 2001;Tyson and Knight 2001). For these reasons, there is much interest in tracking the abundance of these taxa.…”