Buffering and Amplifying Interactions among OAW (Ocean Acidification & Warming) and Nutrient Enrichment on Early Life-Stage Fucus vesiculosus L. (Phaeophyceae) and Their Carry Over Effects to Hypoxia Impact

Abstract

Ocean acidification and warming (OAW) are occurring globally. Additionally, at a more local scale the spreading of hypoxic conditions is promoted by eutrophication and warming. In the semi-enclosed brackish Baltic Sea, occasional upwelling in late summer and autumn may expose even shallow-water communities including the macroalga Fucus vesiculosus to particularly acidified, nutrient-rich and oxygen-poor water bodies. During summer 2014 (July–September) sibling groups of early life-stage F. vesiculosus were exposed to OAW in the presence and absence of enhanced nutrient levels and, subsequently to a single upwelling event in a near-natural scenario which included all environmental fluctuations in the Kiel Fjord, southwestern Baltic Sea, Germany (54°27 ´N, 10°11 ´W). We strove to elucidate the single and combined impacts of these potential stressors, and how stress sensitivity varies among genetically different sibling groups. Enhanced by a circumstantial natural heat wave, warming and acidification increased mortalities and reduced growth in F. vesiculosus germlings. This impact, however, was mitigated by enhanced nutrient conditions. Survival under OAW conditions strongly varied among sibling groups hinting at a substantial adaptive potential of the natural Fucus populations in the Western Baltic. A three-day experimental upwelling caused severe mortality of Fucus germlings, which was substantially more severe in those sibling groups which previously had been exposed to OAW. Our results show that global (OAW), regional (nutrient enrichment) and local pressures (upwelling), both alone and co-occurring may have synergistic and antagonistic effects on survival and/or growth of Fucus germlings. This result emphasizes the need to consider combined stress effects.

Season affects strength and direction of the interactive impacts of ocean warming and biotic stress in a coastal seaweed ecosystem

“…Despite the mentioned limitations of our experiments, we may, nonetheless, dare speculating on the fate of Fucus communities in a warmer, more acidic, less saline, overfished, nutrient‐rich, and sporadically deoxygenized Baltic Sea. Fucus will directly suffer from warming in summer, from desalination year‐round but most intensively during summerly stratification, and from hypoxic upwelling in late summer and autumn (e.g., Al‐Janabi et al ). At the same time, it may benefit less from acidification (having CCM) or from nutrient enrichment than its epiphytes because it can accumulate storage products in replete periods (Kawamitsu and Boyer ; Lehvo et al ; Hemmi et al ).…”

“…All abiotic variables assessed in the KOB experiments are available at http://doi.pangaea.de/10.1594/PANGAEA.842739. Per seasonal study, a wide variety of response variables (Table ) were sampled at various temporal intervals (for details, see Werner and Matthiessen ; Graiff et al , b ; Al‐Janabi et al , b ; Werner et al , b ; Graiff et al ; Raddatz et al ). The results were published in the cited references with the raw data being accessible on Pangaea (DOIs in the cited articles).…”

Impacts of Acidic Seawater on Early Developmental Stages of Fucus gardneri at Burrard Inlet, British Columbia

“…However, as CO 2 levels rise, the ocean's carbonate chemistry also changes, making it difficult for calcifying seaweeds and invertebrates to build calcium carbonate skeletal structures or shells because carbonate ions in the seawater are less prevalent (Gazeau et al, 2013;Hofmann and Bischof, 2014). Studies on fucoid algae evaluated the effects of increased CO 2 on vegetative growth of germlings (greater than 8 weeks old) and adult fronds with conflicting results (Gutow et al, 2014;Graiff et al, 2015;Al-Janabi et al, 2016), possibly arising from differential effects of increased photosynthetic activity resulting from higher CO 2 levels and the negative effects of reduced pH on cellular activities. As hydrogen ions become more concentrated in the external environment, the ability to maintain cytoplasmic pH at normal levels within cells may become more difficult.…”

Climate change can cause complex responses in Baltic Sea macroalgae: A systematic review

“…Very few CO2 fertilization experiments have been performed on Baltic macroalgae, with mixed results making it hard to extrapolate to the future. Longer experiments (but see Al-Janabi et al, 2016a, 2016b with well-designed methods for producing the predicted future ocean chemistry (Hurd et al, 2009) should be applied on a wider spectrum of species. In these settings, also other environmental factors such as irradiance, nutrient levels and temperature should be included, as these all may influence the responses of primary producers against OA.…”

“…Three studies (Al-Janabi et al, 2016b;Gutow et al, 2014;Werner et al, 2016) found negative responses; however, in the last study CO2 treatment was coupled with elevated temperature, which the authors interpreted to be driving the decline in Fucus biomass (Werner et al, 2016). In a 4-week experiment in Helgoland, North Sea, Gutow et al (2014) found that in atmospheric CO2 of 700 μatm compared to present atmospheric level, F. vesiculosus growth was reduced by 10-15 % and the C:N ratio was lower.…”