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Preferential impairment of later mating stages and sex-dependent metabolic shifts in Japanese medaka exposed to acute acidification

Thu, 01 Jan 2026 00:00:00 GMT

標題: Preferential impairment of later mating stages and sex-dependent metabolic shifts in Japanese medaka exposed to acute acidification 作者: Chung, Chih-Ching; Liu, Sian-Tai; Horng, Jiun-Lin; Chou, Ming-Yi 摘要: Environmental acidification poses a significant threat to aquatic organisms, yet the underlying mechanisms of how acid stress disrupts complex social and reproductive behaviors remain incompletely understood. In the present study, we investigated the behavioral and physiological responses of adult Japanese medaka (Oryzias latipes) under acute acid exposure (pH 4.5, 24 h). Our results showed that acute acid stress reduced mating success, with a stronger impairment observed in the transition to the crossing stage and subsequent spawning, while the earlier, male-driven stages of following and courtship were relatively less affected under the present experimental conditions. This reproductive impairment did not coincide with detectable changes in generalized emotional-like behavior. Fish showed normal performance in the novel tank test and maintained territorial aggression. Physiologically, we observed a clear sexual dimorphism. Under acid stress, males maintained relatively stable MOB and JAmm, whereas females showed elevated MOB and JAmm. These findings suggest that reproductive impairment may be more pronounced in energetically demanding mating stages and may be associated with sex-dependent physiological strain. We further propose that the increased metabolic cost of acidbase regulation in females could shift energy allocation, and that high-cost coordination behaviors may be reduced in order to maintain short-term survival. This study provides evidence linking bioenergetics, acid-base regulation, and reproductive behavior in a teleost model under acidification.

Organic-inorganic carbon coupling shapes carbon dioxide fluxes in seagrass ecosystems

Thu, 01 Jan 2026 00:00:00 GMT

標題: Organic-inorganic carbon coupling shapes carbon dioxide fluxes in seagrass ecosystems 作者: Natividad, Mariche B.; Cai, Wei-Jun; Bednarsek, Nina; Chen, Jian-Jhih; Chou, Wen-Chen 摘要: Seagrass meadows can remove atmospheric carbon dioxide through organic carbon production and storage, but they also alter seawater chemistry through calcium carbonate formation and dissolution. Most blue carbon assessments focus on organic carbon burial and overlook how inorganic carbon cycling regulates carbon dioxide exchange. This Perspective presents a framework linking organic carbon metabolism, carbonate cycling, and sedimentary processes to explain when seagrass ecosystems function as net carbon dioxide sinks or sources. We introduce a compensation ratio that defines the balance between organic carbon uptake and calcification-driven carbon dioxide release and show how this balance changes with environmental conditions and sediment carbon sources. Using the Dongsha Island lagoon as a case study, we show how seagrass metabolism coupled to dissolution of geologically derived carbonate sediments can sustain alkalinity generation and long-term carbon dioxide uptake. Together, this framework provides a more complete basis for evaluating blue carbon and the climate mitigation potential of carbonate-rich coastal ecosystems.

Event-Scale Responses of Phytoplankton and Heterotrophic Bacterial Biomass and Production to Super Typhoon Maria in the East China Sea

Thu, 01 Jan 2026 00:00:00 GMT

標題: Event-Scale Responses of Phytoplankton and Heterotrophic Bacterial Biomass and Production to Super Typhoon Maria in the East China Sea 作者: Chen, Tzong-Yueh; Thai, Nien En; Lai, Chao-Chen; Chen, Liang-Yu; Shiah, Fuh-Kwo; Gong, Gwo-Ching 摘要: Typhoons are major physical disturbances in marginal seas, yet their event-scale impacts on microbial processes and carbon cycling remain poorly constrained. Here, we investigated the biogeochemical responses to Super Typhoon Maria (2018) in the East China Sea using combined field observations and satellite data. While surface temperature, nutrients, and chlorophyll-a (Chl-a) showed no significant changes, depth-integrated nutrients and Chl-a increased markedly, revealing a clear decoupling between surface and depth-integrated responses driven by vertical mixing and upwelling. Satellite observations further showed that phytoplankton enhancement was short-lived, with Chl-a returning to background levels within one week. This rapid attenuation likely reflects transient nutrient supply and strong grazing pressure. In contrast, microbial responses were characterized by increased bacterial specific growth rate without significant changes in biomass or production, indicating enhanced microbial turnover. Together, these results suggest that typhoon forcing promotes rapid and vertically structured carbon processing through the microbial loop without increasing biomass accumulation. This highlights the importance of temporal resolution and vertical structure in understanding ecosystem responses to episodic disturbances in marginal seas.

Flood-driven nutrient influx and phytoplankton succession in the subtropical waters of the Matsu Archipelago, Taiwan

Thu, 01 Jan 2026 00:00:00 GMT

標題: Flood-driven nutrient influx and phytoplankton succession in the subtropical waters of the Matsu Archipelago, Taiwan 作者: Supriyadi; Lin, Yun-Chi; Chen, Wan-Lin; Chen, Kuo-Shu; Gong, Gwo-Ching; Tsai, Sheng-Fang 摘要: Flood-driven nutrient influxes are a major driver of harmful algal blooms (HABs) in subtropical coastal systems, yet baseline phytoplankton abundance data are often lacking. We conducted a four-year (2021-2024) time-series study in the Matsu Archipelago, Taiwan, to examine the background abundance and succession dynamics of diatoms and dinoflagellates in relation to Minjiang River flooding events. Salinity was used to define flooding (salinity <29; March-June) and non-flooding seasons. The results of our study show that the distribution of phytoplankton consisting of diatoms (1.8 x 10(6) cells/L) and dinoflagellates (4.8 x 10(6) cells/L) has the highest concentration peak in the May and July range. In those months, flooding generally occurs in the Minjiang River. The new background abundance of diatoms is 250,000 cells/L while dinoflagellates are 60,000 cells/L. In general, the abundance each year ranges between these numbers and increases drastically during the flooding season. Diatoms peaked during flooding periods, exhibiting strong correlations with silicate, nitrite, chlorophyll a, temperature, and pH, whereas dinoflagellates were positively associated with dissolved oxygen and chlorophyll a. Canonical Correspondence Analysis revealed that Pseudo-nitzschia, Rhizosolenia, and Chaetoceros were strongly linked to temperature and chlorophyll a during flooding events, while Eucampia dominated in non-flooding seasons. These results provide the first baseline abundance estimates for key phytoplankton groups in this region and highlight the role of freshwater nutrient inputs in shaping community dynamics. This ecological framework offers a foundation for early-warning systems to mitigate HAB risks in subtropical estuarine ecosystems.