Streaming Media
Presentation Abstract
Hypoxia and acidification are chemical stressors that are increasing in duration and extent in many coastal waters, including regions of the Salish Sea. Copepods, which play major roles in marine food webs and biogeochemical cycling, increasingly encounter water columns with these chemical stressors located at depth. Many copepods undergo diel vertical migration (DMV), swimming downwards during the day to avoid visual predation and upwards at night to feed on phytoplankton near the surface. Understanding behavioral responses of copepods to coastal stressors—particularly whether they avoid stressful conditions but potentially increase predation risk by altering DMV behavior—is important to anticipate impacts of climate change on marine ecosystems. We conducted laboratory experiments using stratified water columns to measure effects of bottom water hypoxia and acidification on mortality, avoidance, and swimming behaviors in the calanoid copepod, Calanus pacificus. Copepods showed strong behavioral responses to hypoxia, and weaker but significant responses to acidification. C. pacificus exposed to hypoxic (0.65 mg O2/L) bottom waters were on average higher in the water column, exhibited slower swimming speeds below the halocline and faster swimming speeds above the halocline, and were more likely to be “moribund” (immobile on the bottom) relative to controls. C. pacificus exposed to acidic (7.48 pH) bottom waters swam slower but did not show changes in mortality or depth. Observed responses to hypoxia suggest a 25% decrease in copepod abundance due to mortality and a 22% decrease in the average depth of copepods in situ. These shifts may impact hypoxia’s effects on predator-prey interactions and advective loss from fjords. Changes in swimming speed in response to hypoxia and acidification likely also impact predator-prey interactions and copepods’ energy budgets. With advances in ocean technology, in situ behavioral responses may be useful proxies in monitoring impacts of climate change on coastal ecosystems.
Session Title
Poster Session 3: Land - Water Connections
Conference Track
SSE14: Posters
Conference Name
Salish Sea Ecosystem Conference (2022 : Online)
Document Type
Event
SSEC Identifier
SSE-posters-214
Start Date
27-4-2022 4:00 PM
End Date
27-4-2022 4:30 PM
Rights
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.
Type
Text
Language
English
Effects of hypoxia and acidification on the swimming behavior of Calanus pacificus: Lethal and sublethal responses to stressors
Hypoxia and acidification are chemical stressors that are increasing in duration and extent in many coastal waters, including regions of the Salish Sea. Copepods, which play major roles in marine food webs and biogeochemical cycling, increasingly encounter water columns with these chemical stressors located at depth. Many copepods undergo diel vertical migration (DMV), swimming downwards during the day to avoid visual predation and upwards at night to feed on phytoplankton near the surface. Understanding behavioral responses of copepods to coastal stressors—particularly whether they avoid stressful conditions but potentially increase predation risk by altering DMV behavior—is important to anticipate impacts of climate change on marine ecosystems. We conducted laboratory experiments using stratified water columns to measure effects of bottom water hypoxia and acidification on mortality, avoidance, and swimming behaviors in the calanoid copepod, Calanus pacificus. Copepods showed strong behavioral responses to hypoxia, and weaker but significant responses to acidification. C. pacificus exposed to hypoxic (0.65 mg O2/L) bottom waters were on average higher in the water column, exhibited slower swimming speeds below the halocline and faster swimming speeds above the halocline, and were more likely to be “moribund” (immobile on the bottom) relative to controls. C. pacificus exposed to acidic (7.48 pH) bottom waters swam slower but did not show changes in mortality or depth. Observed responses to hypoxia suggest a 25% decrease in copepod abundance due to mortality and a 22% decrease in the average depth of copepods in situ. These shifts may impact hypoxia’s effects on predator-prey interactions and advective loss from fjords. Changes in swimming speed in response to hypoxia and acidification likely also impact predator-prey interactions and copepods’ energy budgets. With advances in ocean technology, in situ behavioral responses may be useful proxies in monitoring impacts of climate change on coastal ecosystems.
