A mesocosm study investigating the effects of hypoxia and population density on respiration and reproductive biology in the brittlestar Amphiura filiformis

Abstract

Hypoxic events are increasing in frequency and duration, especially in areas susceptible to eutrophication. Such events pose a growing threat to the health and function of marine ecosystems by altering key biological and ecological processes. Of particular concern is how hypoxia impacts upon both the reproductive biology and metabolic activity of marine organisms and what these impacts mean for biodiversity and ecosystem function. Furthermore, information on the effect of population-level processes (e.g. organism density) on individuals' biological responses to hypoxia is currently lacking, hampering predictions on population and species sensitivity to this stressor. Using a mesocosm experiment, we investigated the effects of relatively shortterm hypoxia (14 d, 3.59 mg O 2 l −1 ) and organism density (5, 9, 13, 17, and 21 ind. per aquarium, equating to 500, 900, 1300, 1700, and 2100 ind. m −2 respectively) on the aerobic metabolism and reproductive biology of a key infaunal species, the brittlestar Amphiura filiformis. While there were no observed effects of organism density, exposure to hypoxia did result in reduced metabolic rates and delayed metabolic recovery rates once normoxic (8.09 mg O 2 l −1 ) conditions were restored. Additionally, hypoxia resulted in delayed female reproductive cell development, smaller oocyte feret diameter, and a greater number of pre-vitellogenic oocytes present within the ovaries. These disruptions to metabolism and reproductive biology during hypoxia could cause major alterations in the quantity and quality of planktonic propagules supplied by benthic species to the pelagic environment, which in turn could affect benthic community diversity in the long term, as well as bentho-pelagic coupling, if repeated hypoxic events occur. KEY WORDS: Low oxygen · Aerobic respiration · Benthic invertebrate biologyResale or republication not permitted without written consent of the publisher FREE REE ACCESS CCESS

Rapid deep ocean deoxygenation and acidification threaten life on Northeast Pacific seamounts

“…Brittle stars become less mobile and more vulnerable to predation under low oxygen, leading to shifts in trophic interactions ( Ophiothrix quinquemaculata , Riedel, Stachowitsch, & Zuschin, 2008). Additionally, hypoxic treatments of the brittle star Amphiura filiformis have shown impacts on metabolism and reproduction (Calder‐Potts, Spicer, Calosi, Findlay, & Widdicombe, 2015) and reduced arm growth and disturbance of spawning (Nilsson & Sköld, 1996). Behavioral change under low oxygen has been shown for glass sponges; they reduce (energetically expensive) filtering (i.e., feeding) rates (Leys & Kahn, 2018).…”

“…Brittle stars become less mobile and more vulnerable to predation under low oxygen, leading to shifts in trophic interactions (Ophiothrix quinquemaculata,Riedel, Stachowitsch, & Zuschin, 2008). Additionally, hypoxic treatments of the brittle star Amphiura filiformis have shown impacts on metabolism and reproduction(Calder-Potts, Spicer, Calosi, Findlay, & Widdicombe, 2015) and reduced arm growth and disturbance…”

DIY OCEANOGRAPHY • A Simple and Inexpensive Method for Manipulating Dissolved Oxygen in the Lab

“…Most low oxygen events are this second type, relatively short in duration but occurring frequently (Wenner et al, 2004). Many researchers have examined the effects of declining or persistent low DO on water and sediment chemistry (McCarthy et al, 2008;Lehrter et al, 2012;Neubacher et al, 2013;Foster and Fulweiler, 2019) and organismal behavior and physiology (Diaz and Rosenberg, 1995;Long et al, 2008;Levin et al, 2009;Sturdivant et al, 2012;Riedel et al, 2014;Calder-Potts et al, 2015). However, it is far less common to see investigations into dynamic variation in DO, likely because of the difficulties in precisely and repeatedly manipulating DO in the lab.…”