Description: Several experiments were conducted with starved and fed females of the arctic copepod Calanus hyperboreus to investigate 1) their life span, reproductive period, egg production and egg viability ; 2) to study the effect of origin, ie Atlantic and Arctic waters in the Greenland Sea, on the timing of reproduction; and 3) to study the effect of time of collection on the onset of reproductive activity as a first approach to study control mechanisms of the reproductive cycle. Females collected in October produced up to 1000 eggs and had a maximum life span of 164 days without feeding, whereas fed females produced up to ca. 6000 eggs and survived up to 806 days. These observations support earlier assumptions that females were multiannual-iteroparous, ie capable to spawn in successive years, which would be unique for calanoid copepods. In starved females clutch size decreased significantly with each spawning event. Viable eggs were produced during most of the life time. There was no difference in the timing of reproductive activitiy between females from the Westspitsbergen Current and the Greenland Sea Gyre. Fed and starved females collected in May and June began to spawn circa two and four months after collection, respectively, whereas females collected in August and October started spawning at the same time, in the middle of October. This indicates initiation of reproductive activity in the field in August, coincident with the descent into deep waters. Potential cues for the untimely spawning of females collected in spring, and "unnatural" feeding in fall experiments are discussed. Their large size, robustness and combination of different types of diapause in their life cycle makes C. hyperboreus a good model organism to study diapause control mechanisms.

Description: Near-bottom zooplankton communities have rarely been studied despite numerous reports of high zooplankton concentrations, probably due to methodological constraints. In Kongsfjorden, Svalbard, the near-bottom layer was studied for the first time by combining daytime deployments of a remotely operated vehicle (ROV), the optical zooplankton sensor moored on-sight key species investigation (MOKI), and Tucker trawl sampling. ROV data from the fjord entrance and the inner fjord showed high near-bottom abundances of euphausiids with a mean concentration of 17.3 ± 3.5 n x 100 m^-3. With the MOKI system, we observed varying numbers of euphausiids, amphipods, chaetognaths, and copepods on the seafloor at six stations. Light-induced zooplankton swarms reached densities in the order of 90,000 (euphausiids), 120,000 (amphipods), and 470,000 ind m^-3 (chaetognaths), whereas older copepodids of Calanus hyperboreus and C. glacialis did not respond to light. They were abundant at the seafloor and 5 and 15 m above and showed maximum abundance of 65,000 ind m^-3. Tucker trawl data provided an overview of the seasonal vertical distribution of euphausiids. The most abundant species Thysanoessa inermis reached near-bottom concentrations of 270 ind m^-3. Regional distribution was neither related to depth nor to location in the fjord. The taxa observed were all part of the pelagic community. Our observations suggest the presence of near-bottom macrozooplankton also in other regions and challenge the current view of bentho–pelagic coupling. Neglecting this community may cause severe underestimates of the stock of pelagic zooplankton, especially predatory species, which link secondary production with higher trophic levels.