The ecology of the exotic zooplankter, Bythotrephes longimanus in a reservoir system: Evaluating the role of multiple environmental factors in life-cycle completion.

摘要

A recent surge in range expansion of many non-indigenous species has prompted scientists to identify those habitat characteristics that facilitate successful dispersal and establishment of exotic species. For the spiny waterflea, Bythotrephes longimanus (Onychopoda: Cercopagidae), establishment requires suitable habitat in two very different regions of a lake, the pelagia and the sediment. During the ice-free season, B. longimanus is an active free-swimming plankter of about 1 cm total length whose growth and reproduction are strongly temperature dependent. It requires an abundance of microcrustacea prey to satisfy its growth, but can also be highly vulnerable to fish predation. During the winter, B. longimanus is present as a sexual diapausing egg that undergoes dormancy in lake sediments where extreme oxygen and pH conditions can be encountered. To broaden our understanding of B. longimanus' niche, the range of limnological conditions that can satisfy both life cycle stages was examined through laboratory experiments, in situ experiments in reservoirs, and field observations in Island Lake Reservoir (St. Louis Co., Minnesota). This study demonstrates (1) tight annual correspondence between the planktonic life stage of B. longimanus and the sediment diapausing egg bank; (2) environmental conditions and maternal investment influence diapausing egg hatching success, length of dormancy, and neonate condition; (3) a combination of predation and food resource limitations dictate when planktonic B. longimanus will be numerically successful, and (4) stark contrasts exist between the ecology of B. longimanus in reservoir systems compared to natural lakes.