Ocean Acidification

[New publication] Biology Letters publishes CO2 x Hypoxia review

Gobler & Baumann’s review provides a good overview over the nascent field of multi-stressor acidification and hypoxia work. A first part firmly establishes that virtually all hypoxic zones in the ocean are also acidified, given that metabolic processes (i.e., respiration) consume oxygen and release CO2 into the environment. In a second part, the sparse emerging evidence for multistressor effects of low pH (high CO2) and low oxygen are reviewed, showing that while the majority of effects are additively negative, every study so far has also found synergistically negative effects of combined stressors in at least one trait.

This invited review was published Open Access.

Gobler, C.J. and Baumann, H. (2016)
Hypoxia and acidification in ocean ecosystems: Coupled dynamics and effects on marine life.
Biology Letters 12:20150976

Examples for synergistic negative effects of low DO and low pH (high CO2) on different traits and marine taxa. (a) Synergistic decrease in respiration rate in small and big sea urchins [27]; (b) growth rate of juvenile quahog was unaffected by low DO or low pH individually, but decreased under combined stressor conditions [23]; (c) survival of Atlantic silverside larvae to 10 dph. Survival was robust against low pH and sensitive to low DO, but decreased synergistically under combined stressors (green arrow, [22]); (d) representation of Po ̈rtners [25] ‘Oxygen- and capacity-limited thermal tolerance’ framework, adapted to the multiple stressor scenario of acidification and hypoxia.


There is increasing recognition that low dissolved oxygen (DO) and low pH conditions co-occur in many coastal and open ocean environments. Within temperate ecosystems, these conditions not only develop seasonally as temperatures rise and metabolic rates accelerate, but can also display strong diurnal variability, especially in shallow systems where photosynthetic rates ameliorate hypoxia and acidification by day. Despite the widespread, global co-occurrence of low pH and low DO and the likelihood that these conditions may negatively impact marine life, very few studies have actually assessed the extent to which the combination of both stressors elicits additive, synergistic or antagonistic effects in marine organisms. We review the evidence from published factorial experiments that used static and/or fluctuating pH and DO levels to examine different traits (e.g. survival, growth, metabolism), life stages and species across a broad taxonomic spectrum. Additive negative effects of combined low pH and low DO appear to be most common; however, synergistic negative effects have also been observed. Neither the occurrence nor the strength of these synergistic impacts is currently predictable, and there- fore, the true threat of concurrent acidification and hypoxia to marine food webs and fisheries is still not fully understood. Addressing this knowledge gap will require an expansion of multi-stressor approaches in experimental and field studies, and the development of a predictive framework. In consider- ation of marine policy, we note that DO criteria in coastal waters have been developed without consideration of concurrent pH levels. Given the per- sistence of concurrent low pH–low DO conditions in estuaries and the increased mortality experienced by fish and bivalves under concurrent acidifi- cation and hypoxia compared with hypoxia alone, we conclude that such DO criteria may leave coastal fisheries more vulnerable to population reductions than previously anticipated.

[Student video] Climate Change: A Future for Fish in a Changing Ocean

A big shout-out to Megan, Rainer, and Liz who apart from their intrepid work as volunteers in our lab also excelled here in their video project for MARN3000. They interviewed Profs. Kelly Lombardo, Michael Finiguerra, and Hannes Baumann about aspects of Marine Climate Change and then cut their answers with researched video material from the web. Note the sartorial touch throughout the clip (6 min)!
Well done, all!

Megan Barry
Rainer Moy-Huwyler
Elizabeth Karamavros

[Talk] Multistressor seminar at URI

URI talk

On 26 February 2016, H. Baumann was invited to give a seminar at the Biological & Environmental Sciences Colloquium Series at the University of Rhode Island, featuring the recently published e-lecture on “Combined effects of ocean acidification, warming, and deoxygenation on marine organisms”
His host, David Bengston has been a renowned fisheries and aquaculture biologist for the past 40 years.

Baumann, H. (2016)
Combined effects of ocean acidification, warming, and hypoxia on marine organisms.
Limnology and Oceanography e-Lectures 6:1-43

[Lab news] Sand lance spawning

For the last 6 weeks, we housed about 100 adult sand lance (Ammodytes dubius) in our lab that Chris and Jake brought from a research cruise on Stellwagen Bank (Massachusetts Bay). We watched them visibly ripen in our tanks, and today managed to strip-spawn 10 males and 10 females, obtaining several thousands of eggs and having them develop under different CO2 conditions now.
Thumbs up, and fingers crossed for the next steps!

Sand lance embryos 1h post-fertilization
Sand lance embryos 1h post-fertilization
Sand lance embryos 1h post-fertilization
Sand lance embryos 1h post-fertilization
Squeezing milt from a running ripe male sand lance
Squeezing milt from a running ripe male sand lance

Squeezing eggs from a running ripe female sand lance
Squeezing eggs from a running ripe female sand lance

[Publication] “Offspring sensitivity to ocean acidification changes seasonally in a coastal marine fish”

MEPS Feature Cover
Novel experiments on wild Atlantic silversides Menidia menidia suggest that parents are capable of pre-conditioning their offspring to the naturally occurring, seasonal acidification in their spawning habitat (shape depicts the annual pattern of pH mean, minimum and maximum.)
How vulnerable are marine organisms to unfolding ocean acidification? Apart from being species- and habitat-specific, the answer may even differ between times of the year. Other than open ocean species, most coastal organisms naturally experience large seasonal pH fluctuations, to which they have adapted. Murray and co-workers monitored pH conditions in the spawning habitat of a common coastal marine fish, while sampling wild spawning adults repeatedly over the season and conducting standardized CO2 exposure experiments on their offspring. This demonstrated that offspring CO2 sensitivity is not constant, but decreases seasonally with the increasing acidification in their habitat. These findings imply that realistic assessments of species CO2 sensitivities should account for the pH/CO2 variability in the parental environment.

Murray, C.M., Malvezzi, A., Gobler, C.J., and Baumann, H.(2014) Offspring sensitivity to ocean acidification changes seasonally in a coastal marine fish. Marine Ecology Progress Series 504: 1-11 (Open Access)