Informe: Invasive Quagga Mussel: Potential Survival, Growth and Reproduction in the Pyramid Truckee Ecosystem

SEITZ, CARINA; CHANDRA, SUDEEP; SCORDO, FACUNDO

2021-02-01/2022-03-14

1-43

Biológica

Recursos hidricos

The introduction of non-native species is a leading threat to the biodiversity and function of inland waters, which has been exacerbated by the globalization of the economy and trade. The most aggressive freshwater invaders, the Dreissena species zebra (Dreissena polymorpha) and quagga (D. rostriformis bugensis), arrived at the Great Lakes Region mid- 90s, and by 2007 the infestation of quagga mussels appeared in the western United States, in the largest reservoir in country Lake Mead. A recent study suggests that quagga mussels could live in Lake Tahoe, located in the Upper Truckee River basin. This raised the alarm about the possible invasion of quagga mussels into nearby, connected downstream ecosystems, such as Pyramid Lake. This lake is home to endangered and threatened species, so ensuring the quality of the lake habitat is critical to its protection. Therefore, this works aims to assess the risk of invasion to Pyramid Lake-Truckee River ecosystem and provide insights into the tolerance of quagga mussels to high pH concentration. To analyze the potential for survival, growth, and reproduction, we drew water from two Pyramid Lake (Warrior Point and Popcorn Rock) locations, one in the lower Truckee River basin nearby the connecting hydrologic inflows to the lake, and one in Lake Mead. Lake Mead was used as a positive control experiment as it is currently invaded by quagga mussels. In addition, we collected the mussels from Lake Mead.One of the primary variables used to assess the potential of mussel invasion is pH. However, it has been barely studied for quagga mussels. In particular, the upper limit of tolerance has not been defined for quagga mussels, except for pH 12 which causes rapid mortality. To test the potential survival of mussels in Pyramid Lake with lower pH water, we amended it with Phosphoric Acid. Also, we amended water from Truckee River and Lake Mead with Sodium Hydroxide to test mussels´ survival at higher pH concentrations. We observed 100% mortality after 12 h in unamended Pyramid Lake water, even when we reduced the temperature and pH. In contrast, adult quagga mussels in unmodified Truckee River water increased in size and reproduced successfully with a moderate infestation potential. In Pyramid Lake water, swelling and disintegration of body tissues suggest degradation in the osmoregulating system as the likely cause of death. Therefore, we propose the high concentration of Potassium, Sodium, and Chloride in the lake water as the probable cause of the high mortality rate. The response of quagga mussels to higher pH concentrations in freshwater treatments showed 50% mortality at pH 11 after 2 and 1 days in Mead and Truckee waters, respectively. While in pH 10, 50 % of mortality occurred after ~12 days in both water treatments. No mortality at pH 9.0, 9.3, and 9.5 during the experiment. The finding of this study provides new information about higher limits of tolerance of pH concentration for quagga mussels.Examining invasion potential into aquatic ecosystems requires additional focus on understanding physiological and environmental tolerances specific to quagga mussels rather than their taxonomic relatives, zebra mussel for which much literature has been developed. Furthermore, we note that one or a few parameters may not be sufficient to determine the potential of quagga mussel invasions, and more site-specific studies are needed. We did not find a potential risk of invasion for quagga mussels in Pyramid Lake; however, we did find that adults can survive in the water of the Truckee River entering pyramid lake. In addition, other possible invasions by other species, such as zebra mussels, which tolerate higher salinity concentrations, should not be ruled out and pragmatic approaches to minimizing the potential for introduction of invasive species (zebra mussels, plants, fishes) should be undertaken including education and advertisement and boat inspections and washing stations.