Uptake of diatoms in Baltic Sea macrozoobenthos during short-term exposure to severe and moderate hypoxia

Abstract

The effect of severe and moderate hypoxia on food uptake of benthic macrofauna was studied in the laboratory. The hypothesis was that low oxygen concentrations negatively affect feeding at oxygen levels that have little effect on the studied animals' survival. The bivalve Macoma balthica, the priapulid Halicryptus spinulosus, the amphipods Monoporeia affinis (subadult & juvenile) and Pontoporeia femorata (subadult) were offered the 14 C-labelled diatom Skeletonema costatum in 0.8 to 10.6 mg O 2 l -1 . Feeding was measured as radioactivity uptake. Subadult amphipods were studied one species at a time (single) or together (mixed). Feeding changed in all amphipods at the lowest oxygen concentrations, but no effect was found for M. balthica and H. spinulosus. At the lowest concentration (0.8 mg O 2 l -1 ) feeding by subadult M. affinis (single) was only 17% of the full oxygen saturation (10.6 mg O 2 l -1 ), and, at 1.6 mg O 2 l -1 , 14% of the feeding at 8.9 mg O 2 l -1 . Juvenile M. affinis consumed more labelled algae at 3 mg O 2 l -1 than at higher oxygen concentrations. M. balthica feeding was not affected. Little radioactivity uptake was registered for H. spinulosus at any oxygen concentration, showing that H. spinulosus is not a surface deposit feeder. The amphipods were the most sensitive to week-long oxygen deficiency. Survival decreased significantly in the lowest oxygen concentrations (0.8; 1.6 mg O 2 l -1 ). Of the subadult M. affinis 15 and 65%, respectively, survived, compared with 0 and 58% for P. femorata. Juvenile M. affinis mortality was high in all oxygen concentrations, whereas most M. balthica and H. spinulosus survived.KEY WORDS: Severe hypoxia · Moderate hypoxia · Macrobenthos · 14 C-uptake · Baltic SeaResale or republication not permitted without written consent of the publisher

Modelling macrofaunal biomass in relation to hypoxia and nutrient loading

“…In addition, anoxia (and severe hypoxia) have been shown to reduce food intake (Ejdung et al, 2008) and by including this, the food uptake is described as…”

Isotopic niche reflects stress-induced variability in physiological status

“…[ 39 ]. Monoporeia affinis are sensitive to low oxygen concentrations, which may reduce swimming and feeding activities [ 40 ]. Amphipod survival in each mesocosm was recorded, and all recovered individuals were snap-frozen.…”

“…Amphipod survival was used as a covariate when evaluating effects on body mass, fecundity and embryo viability to control for possible size-selective mortality effects ( table 1 ). In Experiment 2, oxygen penetration depth and amphipod mortality were used as covariates when evaluating effects on body mass, body condition and RNA : DNA to control for suboptimal feeding conditions [ 40 ] and size-selective mortality ( table 1 ). Analyses were carried out using the lme4 and lmeTEST packages [ 51 , 52 ] (accessed 20 April 2017) in R studio v. 3.1.1 [ 53 ].…”

“…In Experiment 2, δ 13 C and δ 15 N values were related to body mass, C : N ratio, RNA : DNA ratio and weighted mean oxygen penetration depth as well as amphipod mortality ( table 1 ). Mortality was included as a predictor since high mortality could potentially result in scavenging and hence enriched isotope values of surviving individuals, whereas low oxygen penetration depth was expected to reduce swimming activity and affect respiration-driven changes in δ 13 C [ 40 ]. The Akaike information criterion (AIC) was used to select the most parsimonious model.…”

Identifying biotic drivers of population dynamics in a benthic–pelagic community

“…Additionally, a snapshot with oxygen measurements for late summer only might not reflect the overall oxygen conditions for the entire year well enough, as oxygen conditions can vary considerably, both seasonally and spatially (Virtanen et al, 2019). Also, a temporary drop in the oxygen level can be detrimental for sensitive taxa, such as M. affinis that feed less in hypoxic conditions (Ejdung et al, 2008).…”