Impact of salinity and temperature on the vital rates of co-occurring Calanus glacialis and C. finmarchicus from West Greenland

Abstract

Climate change creates multiple stressors for organisms in Arctic ecosystems, such as key zooplankton species of the genus Calanus. Here, we quantified the mortality and fecal pellet production rate of Calanus finmarchicus and C. glacialis from Disko Bay, West Greenland, with respect to temperature and salinity. The 2 species were exposed to temperatures of 0, 5 and 10°C and a salinity range from 5 to 60. C. glacialis had a significantly lower mean lethal concentration (LC50) of 9 with a standard error of 1.98 at the lowest temperature, at salinities below in situ salinities, compared to C. finmarchicus (14 ± 0.35). At high temperatures, C. glacialis LC50 was significantly lower than that at 0°C. At high salinities, the 2 species did not have significantly different LC50 values. The fecal pellet production rates were quantified at saturated food concentration (>400 µg C l-1). No impact of salinity was observed between salinities of 25 and 40. Increases in fecal pellet production rates were observed at the limits of this range, indicating a physiological stress response. Within the 25-40 salinity range, fecal pellet production rates increased exponentially with temperature for C. finmarchicus (average Q10 = 1.9 ± 0.18) in the temperature range of 0-10°C, while for C. glacialis, they peaked at 5°C (average Q10 between 0 and 5°C was 2.19 ± 0.15). Our results demonstrate a high physiological plasticity of both Calanus species with respect to salinity. C. glacialis will be more tolerant in a future surface freshening scenario, although this advantage seems to be impaired at temperatures above 5°C.

Cumulative Impacts of Oil Pollution, Ocean Warming, and Coastal Freshening on the Feeding of Arctic Copepods

“…This pattern was also found for C. finmarchicus, though with higher sensitivity compared to C. glacialis , seen by a significantly higher FPP . Makri et al also found a similar response for C. finmarchicus within the same temperature range (0–10 °C) and with salinities ranging between 25 and 40 psu. However, they observed the FPP of C. glacialis to peak at 5 °C, contradicting previous observations. , …”

“…An increase in temperature accelerates biochemical reactions and hence metabolic rates, which is most likely the underlying mechanism of this finding . Previous studies have also reported a temperature-driven increase in FPP for the two species. ,, Both Grote et al and Kjellerup et al reported increased feeding for C. glacialis at higher temperatures within a range of 0–10 °C. This pattern was also found for C. finmarchicus, though with higher sensitivity compared to C. glacialis , seen by a significantly higher FPP .…”

“…In terms of salinity, Makri et al found no significant impact on FPP across a salinity range of 25–40 psu. At 20 psu, they observed an increase in FPP at a temperature of 0 °C but no difference at 5 °C.…”

“…Arctic copepods are exposed to ongoing environmental changes, including warming and freshening. Makri et al recently determined the tolerance of C. glacialis and C. finmarchicus to a range of temperatures (0, 5, 10 °C) and salinities (5–60 psu), as well as their combination. They found a stress response in the form of increased feeding outside of 25–40 psu and higher mortality outside of 5–55 psu and 20–45 psu for C. glacialis and C. finmarchicus , respectively.…”