A major environmental concern going forward into the 21st century is that of climate change. Invertebrates that reside in aquatic habitats with momentary periods of environmental suitability may be particularly at risk to increases in temperature. These animals, including fairy shrimp, are able to survive unfavorable conditions by producing diapausing eggs. Diapausing eggs from two fairy shrimp species, one typically active in summer (Streptocephalus sp.) and one active during winter (Branchinecta sp.), were obtained to determine possible effects of a projected 4 °C rise in temperature on egg viability and development. Summer fairy shrimp eggs (n=20, 3 replicates) were incubated at temperatures of 22, 27, 32, and 37 °C to determine optimal egg hatching temperature. The same approach was applied to winter fairy shrimp eggs with temperature treatments of 7, 12, 17, 22, and 27 °C. The seasonal high where the summer species is active is 37.5 °C, while for the winter species, the temperature is 26.8 °C. After determining optimal hatching temperature, treatments were adjusted 4 °C above reported highs. Naupliar development will be followed at the optimal and projected temperatures to determine survival rates to first reproduction.
Results/Conclusions
Optimal egg hatching experiments revealed different hatching successes for summer and winter fairy shrimp species. For the summer species, 27 °C yielded the highest hatching rate (Mean ± SD: 85 ± 10 %) while 37 °C had the lowest (28 ± 25 %). Temperature treatment 22 °C had highest hatching rate for winter species (13.3 ± 2.9 %) and 7 °C the lowest (3.3 ± 2.9 %). Summer species had their lowest egg hatching percentage at the highest temperature treatment tested during optimal egg hatching trails. Winter species yielded a higher percent hatching at the two warmest incubations for optimal hatching. Under the future climate scenario, the summer species had its lowest hatching rate (3.3 ± 2.9 %) at 41.5 °C. In contrast the winter species, had the second highest hatching rate. Our results indicated that summer species are more susceptible to temperature increases. For aquatic invertebrates with specialized short life cycles timing of egg hatching is paramount. The utilization of temporary resources and successful reproduction are crucial. A delay in hatching challenges the amount of time needed for species to contribute to future populations and may negatively impact other species that depend on fairy shrimp for food.