Avoiding low-oxygen environments: oxytaxis as a mechanism of habitat selection in a marine invertebrate

Abstract

Oxygen-poor habitats are increasingly common in aquatic environments. Human activities are accelerating the spread of oxygen-poor environments, yet the way in which larvae avoid low-oxygen conditions remains poorly resolved. For organisms with a sessile or sedentary adult phase, habitat selection is crucial, and many organisms show sophisticated responses to various habitat cues during colonization. Whether oxygen availability serves as such a cue is unknown, yet increasingly, it seems that oxygen is an essential limiting resource in some systems. In a series of experiments, we manipulated oxygen levels during dispersal and colonization in larvae of the model marine invertebrate Bugula neritina in the laboratory. We found that, in the presence of lower oxygen levels, larvae reduce the time spent in habitat exploration and that they delay settlement. We also found that larvae avoid hypoxic water (positive oxytaxis)-the first such demonstration for marine larvae. All of these behaviors may decrease the likelihood of colonizing low-oxygen habitats in nature. Our results suggest that marine invertebrate larvae, in this species at least, can use oxygen availability as an initial cue for habitat selection but that additional factors (e.g. biofilms) determine settlement patterns.

Removal of deep-sea sponges by bottom trawling in the Flemish Cap area: conservation, ecology and economic assessment

“…It has also been hypothesized that the removal of the sponges will remove the structuring and functional effect of sponges, and that the increase in organic matter in the sediment if not immediately consumed by the infauna 38 , can create a local oxygen depletion. The oxygen depletion will diminish the potential of colonization due to avoidance by larvae 39 , and the habitat will take a long time to recover. If decreased oxygen availability at the bottom, the general complex food web associated with sponge grounds in the area 7,34 may be affected.…”

Effects of habitat usage on hypoxia avoidance behavior and exposure in reef-dependent marine coastal species

“…Low DO can affect the prey and predators of the species of interest, which then, even without direct exposure, affect growth and mortality (David and David, 2000). Major indirect effects occur from the avoidance movement in response to hypoxia exhibited by many mobile species to reduce their exposure to low DO (Craig, 2012;Lagos et al, 2015;Jorissen and Nugues, 2021;LaBone et al, 2021). Avoidance results in indirect effects because it is not the exposure to DO that causes physiological effects but rather the consequences of individuals being forced to move to less preferred locations and habitats where mortality, growth, and reproduction would be different than if they were able to inhabit the avoided areas (Eby and Crowder, 2002;LaBone et al, 2021).…”

Estimating monotonic rates from biological data using local linear regression

“…The full time series is clearly non-linear: the rate of O 2 consumption initially decelerates as the chamber and larva equilibrate after handling. There is also a subtle acceleration towards the end of the time series, probably resulting from a physiological response by the larva to declining O 2 availability (Lagos et al, 2015), or accumulation of bacterial biofilm that began to consume oxygen. Any estimate of O 2 consumption rate including these non-linearities would be conflated with these other processes.…”