Study on the effects of near-future ocean acidification on marine yeasts: a microcosm approach

Abstract

Marine yeasts play an important role in biodegradation and nutrient cycling and are often associated with marine flora and fauna. They show maximum growth at pH levels lower than present-day seawater pH. Thus, contrary to many other marine organisms, they may actually profit from ocean acidification. Hence, we conducted a microcosm study, incubating natural seawater from the North Sea at present-day pH (8.10) and two near-future pH levels (7.81 and 7.67). Yeasts were isolated from the initial seawater sample and after 2 and 4 weeks of incubation. Isolates were classified by matrix-assisted laser desorption/ ionization time-of-flight mass spectrometry (MALDI-TOF MS) and representative isolates were identified by partial sequencing of the large subunit rRNA gene. From the initial seawater sample, we predominantly isolated a yeast-like filamentous fungus related to Aureobasidium pullulans, Cryptococcus sp., Candida sake, and various cold-adapted yeasts. After incubation, we found more different yeast species at near-future pH levels than at present-day pH. Yeasts reacting to low pH were related to Leucosporidium scottii, Rhodotorula mucilaginosa, Cryptococcus sp., and Debaryomyces hansenii. Our results suggest that these yeasts will benefit from seawater pH reductions and give a first indication that the importance of yeasts will increase in a more acidic ocean.

A high biodiversity mitigates the impact of ocean acidification on hard-bottom ecosystems

“…5). This is consistent with current evidence showing that marine fungi can be favoured by acidification 98,99 . Notably, the proliferation of fungi decreased with increasing biodiversity (R 2 = 0.847; p < 0.01; Fig.…”

Diversity of filamentous fungi associated with coral and sponges in coastal reefs of northeast Brazil

“…It has already been recorded that pollution in coastal and estuarine areas, mainly by anthropic activities, generates eutrophication events and that these may create point acidification by microbiological routes . In fact, our results corroborate this, as the amount of coliforms is a measure used to estimate pollution.…”

“…Among the unusual species that we isolated, all of them were already previously related to plants, either as saprophytic or pathogenic, suggesting that they were transported from the terrestrial environment to the reefs. Similar facts have already been observed, and led us to suspect that these are spore contaminants and not active symbionts , as isolating a fungi from a marine organism does not show that the fungi grows there because sponges filter feed from the surrounding seas, which contain spores of terrestrial fungi coincidentally found in these waters .…”

Salinity, pH and temperature growth ranges of Halophytophthora isolates suggest their physiological adaptations to mangrove environments

“…The optimal growth of Halophytophthora species at neutral/acidic pH suggests that ocean acidification might not exert a strong effect on mangrove Halophytophthora . In a microcosm study of seawater of the North Sea, a higher abundance and an increase in species richness of marine fungi were observed after incubation at pH 7.81 and 7.67 compared with the normal pH of the North Sea (8.10), showing that marine filamentous fungi and yeasts might benefit from seawater acidification (Krause et al 2013a , 2013b ).…”