Responses of Intertidal Bacterial Biofilm Communities to Increasing pCO2

Abstract

The effects of ocean acidification on ecosystems remain poorly understood, because it is difficult to simulate the effects of elevated CO2 levels on entire marine communities in controlled laboratory conditions. Natural systems such as CO2 seeps that are enriched in CO2 are being used to help understand the long-term effects of ocean acidification in situ. Here, we compared biofilm bacterial community composition on cobbles/boulders and bedrock along a CO2 gradient in the NW Pacific. Samples sequenced for 16S rRNA showed that different bacterial communities were associated with zones of different seawater pCO2, and were also distinct between the two rocky habitat types. In both habitats, there was increased bacterial diversity in the biofilm communities in acidified conditions. Differences in pCO2 were associated with differences in the relative abundance of major bacterial phyla including Cyanobacteria, Bacteroidetes, Proteobacteria, Planctomycetes, and Verrucomicrobia. However, despite the differences in community composition, there is little sign of changes in the bacterial community that would be functionally significant in terms of nutrient cycling and ecosystem structure. As well as direct seawater pH effects, it is possible that increased growth of algae and decreased grazing contributed to the observed shift in bacterial community composition at high CO2, as documented at several seep systems worldwide. Given the importance of biofilms to coastal ecology, changes in their composition due to globally rising pCO2 levels requires further investigation to assess the implications for marine ecosystem function. However, the apparent lack of functional shifts in the biofilms despite the pH change may be a reassuring indicator of stability in shallow oceanic biofilm communities in the future.

Microbial communities network structure across strong environmental gradients: How do they compare to macroorganisms?

“…Firsts, removal of sections of natural, existing rocks from the environment with different exposure time (De la Iglesia et al 2012, Taylor et al 2014, Tan et al 2015, Kerfahi et al 2020, or the installation of artificial surfaces such as plexiglass, polystyrene, or glass slides (Zhang et al 2013, Sanli et al 2015. The first approach is useful for examining the composition of microbial communities but makes it difficult to make sensible comparisons across gradients because the successional time is unknown.…”

Ocean acidification locks algal communities in a species‐poor early successional stage

“…To investigate our core question of how ocean acidification influences early community succession of algal communities, experiments using recruitment tiles were carried out using an acidified area of the Shikine Island CO 2 seep, Japan (34°19′9ʺN, 139°12′18ʺE), and a nearby reference p CO 2 area in an adjacent bay (~600 m away by the shortest route). Both the reference and acidified locations (hereafter ‘350 μatm’ and ‘900 μatm’, respectively) have had their carbonate chemistry and biology well characterized previously (Agostini et al, 2015, 2018; Cattano et al, 2020; Harvey et al, 2018, 2019; Kerfahi et al, 2020; Witkowski et al, 2019), and we present 2 months of additional original pH T (Figure S1) and temperature data collected at the ‘900 μatm’ location with a Durafet sensor (SeaFET, Sea‐Bird Scientific) using the same approach as Agostini et al (2018). Salinity was measured concurrently using Hobo conductivity loggers (U24‐002‐C), and discrete samples for total alkalinity were collected throughout the study period, with total alkalinity measured using an auto‐titrator (916 Ti‐Touch, Metrohm).…”

Ocean acidification alters the benthic biofilm communities in intertidal soft sediments

“…So far, there have been several studies investigating how OA affects coastal benthic biofilms and these have concluded that OA can alter the biomass and community composition (Kerfahi et al, 2014;Taylor et al, 2014;Kerfahi et al, 2020). However, there are some important gaps in the current understanding.…”

“…However, there are some important gaps in the current understanding. Firstly, most previous studies, solely or independently, investigated the effects of OA on microalgae or bacteria in intertidal benthic biofilms, but failed to consider the impacts of OA at a community-level (Cartaxana et al, 2015;Kerfahi et al, 2020). Thus, to get a better understanding of the implications of OA on benthic biofilms, it is recommended that the effects of OA on microalgae, bacteria and viruses in benthic biofilms are studied simultaneously.…”