Climate-driven restructuring of phytoplankton productivity and community composition in the south-eastern black sea: Insights from seasonal CO<sub>2</sub>-Temperature manipulation experiments
MARINE ENVIRONMENTAL RESEARCH, cilt.218, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 218
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.marenvres.2026.108029
- Dergi Adı: MARINE ENVIRONMENTAL RESEARCH
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, BIOSIS, Chemical Abstracts Core, Chimica, Compendex, EMBASE, Environment Index, Geobase, MEDLINE, Zoological Record, Academic Search Ultimate (EBSCO), Engineering Source (EBSCO)
- Anahtar Kelimeler: Black sea, Carbonate system, Interactive effects, Nutrient stoichiometry, Ocean acidification, Phytoplankton primary production, Warming
- Recep Tayyip Erdoğan Üniversitesi Adresli: Evet
Özet
Semi-enclosed marine systems with low buffering capacity, such as the Black Sea, are expected to experience amplified impacts of ocean acidification and warming, yet experimental evidence on their combined short-term effects on natural phytoplankton assemblages remains limited. Here, we present a seasonally resolved one-year study (four experiments conducted between 2022 and 2023) based on 48 h short-term microcosm incubation experiments using natural phytoplankton communities collected from coastal and offshore stations in the south-eastern Black Sea. CO2 concentrations (360, 600, and 760 ppm) and temperature (ambient and +3 degrees C) were manipulated to examine short-term physiological and compositional responses under projected climate scenarios. We hypothesised that CO2 and warming would exert both independent and interactive effects on short-term particulate organic carbon production (C-14 uptake rates) and relative community composition, with responses varying seasonally and being most pronounced during summer stratification. Short-term particulate primary production increased by similar to 22% and similar to 36% at 600 and 760 ppm CO2, respectively (p<0.05), while warming provided an additional 14-22% enhancement depending on season, with significant CO2 & times; temperature interaction terms detected for total production (two-way ANOVA, p<0.05), indicating synergistic CO2-temperature effects. Warming and moderate CO2 enrichment were associated with increased relative contributions of nano- and picophytoplankton (by similar to 6-10%), whereas high CO2 reduced the warming-driven shift toward smaller cells by maintaining microphytoplankton contributions similar to 10-15% higher than in the warming-only treatment. Carbonate chemistry responded strongly to CO2 manipulation, with pH declining from in-situ values of 8.09-8.21 to 7.06-7.52 during incubations and minor reductions in total alkalinity, reflecting the weak buffering capacity of the system. Pigment composition and microscopy indicated short-term increases in dinoflagellate relative abundance (similar to 12-18%) and concurrent declines in diatom markers, accompanied by accelerated nitrate depletion and reduced nitrogen-to-phosphorus (N:P) ratios, consistent with enhanced nitrogen limitation. Overall, these findings demonstrate pronounced short-term sensitivity of natural phytoplankton assemblages in the south-eastern Black Sea to combined CO2 and warming under controlled incubation conditions. Because these results derive from 48 h microcosm experiments, they represent short-term physiological and compositional responses rather than direct evidence of long-term ecosystem restructuring, yet the observed patterns suggest potential implications for trophic efficiency, harmful algal bloom development, and carbon cycling in this low-buffer, stratified basin under future climate forcing.