Physiology of Lipid-storing Copepods During Summer Along the West Antarctic Peninsula

Copepods are the dominant component of the mesozooplankton within surface waters of the West Antarctic Pensinsula (WAP) during summer. Two of the most common species of large copepods exhibit different life history strategies. Calanoides acutus is predominantly herbivorous, stores lipids as wax esters, and overwinters in a dormant state. In contrast Calanus propinquus is more omnivorous, stores triglycerides, and often remains active during winter. During austral summer 2019, females of both species were sampled along the WAP and across the continental shelf. Chlorophyll profiles and presumed food availability differed dramatically among sampling stations. Physiological condition of the field-sampled copepods is being assessed through transcriptional profiling and enzymatic activity assays. In addition, shipboard experiments were conducted in which copepods were either fed or starved for up to 9 days. Over the experimental period, citrate synthase activity decreased in the starved animals, consistent with metabolic depression and conservation of energetic reserves. Transcriptional profiling of corresponding experimental animals will provide insight into physiological adaptations to patchy food resources and context for interpreting observed patterns in the field.