| Decreased ground-water flux associated with urbanization has the potential to increase the salinity of anchialine ponds at Hawai'i's Kaloko-Honokohau National Historical Park. These unique coastal aquatic ecosystems possess an endemic invertebrate fauna including candidate endangered crustaceans and aquatic insects. To assess the effects of rising salinities on anchialine pond biota, our objective was to determine the effect of salinity and temperature on egg hatch and naiad (larval) survival of the endemic orange-black Hawaiian damselfly (Megalagrion xanthomelas). The study used a 5 x 3 factorial experimental design consisting of constant salinities of 0, 5, 10, 15, and 20 ppt and constant temperatures of 20, 24, and 28°C. Results revealed that eggs and naiads were sensitive to increased salinity and temperature, although different salinity-temperature combinations yield differing effects on hatching success and naiad survival. Generally, egg hatch increased with increased temperature and decreased salinity, whereas, naiad survival increased with decreased temperature and increased at intermediate salinity. Naiads also displayed a threshold response to salinity above 15 ppt with no naiads surviving at 20 ppt despite successful hatch observed at this salinity. Given the limited information on the effects of increased salinity on anchialine pond biota, the results of this study has significant management implications and raises awareness on the importance of water quality and quantity for organisms in these rare environments. |
