Hypoxia effects on females and early stages of Calanus chilensis in the Humboldt Current ecosystem (23°S)

Potential effects of shoaling of oxygen minimum zone on the population of Acartia (Acanthacartia) tonsa in the Humboldt Current Upwelling System (23°S)

“…An earlier study showed that C. chilensis adult female survival, egg production, and growth were not affected by hypoxic treatment (Ruz et al, 2018), which seems to be consistent with field observations that C. chilensis female and egg vertical distribution extend deeper into the oxycline (Ruz et al, 2017). Nevertheless, egg hatching success and naupliar survival were negatively impacted by hypoxia in the same study (Ruz et al, 2018), suggesting that hypoxia tolerance may vary among developmental stages.…”

“…These values are close to our experimental oxygen conditions (Table 2). Hypoxia-induced mortality in copepods in the HCS has been reported for Calanus chilensis (Ruz et al, 2018), Paracalanus. cf.…”

“…The Neutral Red method allowed the discrimination of live (red-stained) vs. dead (non-stained) organisms (Elliott and Tang, 2009;Yáñez et al, 2012). The eggs and copepods in 2 mL of seawater were stained by adding 0.1 mL of Neutral Red solution [0.5% p/v, 1:1000] ( Ruz et al, 2018). After 10 min, the samples were preserved in 4% formaldehyde in a seawater solution buffered with sodium acetate for later analysis.…”

“…Before transferring the samples into counting chambers, they were rinsed on a 200-μm mesh screen to remove the formaldehyde solution. The samples were then acidified to pH < 7 by the addition of ~0.5 mL of acetic acid (C 2 H 4 O 2 ) to develop the red stain's color in organisms that were alive at the end of the experiments (Yáñez et al, 2012;Ruz et al, 2018).…”

“…Egg diameter and cephalosome length and width of nauplii (N1 and N2) were measured (μm ± 1 SD) under a stereomicroscope (40× -80×) equipped with a digital camera and the software Micrometric SE Premium 4. The egg and naupliar biovolumes were calculated from linear dimensions according to Torres and Escribano (2003) and Ruz et al (2018), and then converted to biomass using the factor 0.045 mg C μL − 1 (Ikeda and Omori, 1984). The weight-specific growth rates were calculated from the estimated naupliar weights (μg C) of consecutive stages and the incubation time (Runge and Roff, 2000).…”