Oral Presentation Australian Society for Limnology Congress 2013

Rest is for the tiny: The effects of temperature and photoperiod on the termination of dormancy in microfauna of the Ovens Floodplain. (#34)

Isobel Colson 1
  1. Charles Sturt University, Albury, NSW, Australia

Freshwater aquatic microfauna possess a remarkable ability to survive harsh environmental conditions, through dormancy. Dormant eggs are produced by adult females and transferred to vegetation and the soil, where they remain, sometimes for years, until conditions are suitable for their emergence. Live animals of some groups are also able to enter dormancy. These dormant life stages play a vital role in succession and recovery of aquatic microfaunal populations, particularly in ephemeral waterbodies. Despite this importance, little is known about the particular cues triggering the breaking of dormancy in Australian aquatic microfauna, though international literature suggests that temperature and photoperiod are important cues. In this study the hatching response of dormant microfauna to a range of temperature and light conditions was investigated for billabongs on the Ovens River Floodplain. Sediment from 14 dry billabongs was collected in April 2013, combined and inundated in the laboratory in combinations of four temperatures (10, 15, 20 and 250C) and four photoperiods (8, 10, 12 and 14 hours daylight) representing 'typical' winter conditions to those of late spring. The water used for inundation was collected and refreshed every three days, for three weeks. Hatchling emergence was dominated by rotifers, especially those from the Bdelloida and Cephalodella, with a lesser number of copepod nauplii and cladoceran hatchlings. The results also showed that the highest diversity and abundance of aquatic microfauna emerged at the highest temperature and longest photoperiod, suggesting that these conditions are associated with a more favourable time of year for hatching.