The interplay between predatory chaetognaths and zooplankton community in a high Arctic fjord

In the marine environment, chaetognaths are among the major predators of zooplankton. The most common Chaetognatha species in the Arctic coastal waters are Parasagitta elegans and Eukrohnia hamata. Their distribution and size structure and potential predatory impact on the zooplankton community were analyzed in Isfjorden (Svalbard Archipelago). Parasagitta elegans dominated in terms of biomass (1.5 mg DM & BULL; m  3) over E. hamata (0.09 mg DM & BULL; m  3), and the clear pattern of chaetognaths' size distribution was noticed: smaller individuals occurred in the upper water layers, while larger ones were observed near the fjords' bottom. Based on Redundancy Analysis (RDA) followed by variation partitioning, the zooplankton community was influenced by environmental variables (36.6%) and by chaetognaths (16.6%), while the joint impact for both groups of these predictors was 46.6%. Both increasing temperature and P. elegans influenced medium-sized and small copepods (e.g., Calanus finmarchicus, Oithona similis), pteropods, and meroplankton larvae (upper layers), while E. hamata was related to larger copepods (e.g., Calanus hyperboreus, Metridia longa) at greater depths. The study showed different predation pressure of P. elegans and E. hamata in the Arctic fjord and revealed complex interactions within the zooplankton community and marine environment.

Automated summary

In the marine environment, chaetognaths such as Parasagitta elegans and Eukrohnia hamata are important predators of zooplankton. This study analyzed their distribution, size structure, and predatory impact in the Arctic coastal waters. Parasagitta elegans was dominant in biomass over E. hamata, and there was a clear pattern of size distribution with smaller individuals in upper water layers and larger ones near fjords' bottom. Environmental variables and chaetognaths had significant influences on the zooplankton community, with a joint impact of 46.6%. The study revealed different predation pressure and complex interactions within the zooplankton community and marine environment in the Arctic fjord.