University of Maryland Center for Environmental Science, Horn Point Laboratory, PO Box 775, Cambridge, Maryland 21613, U.S.A..
University of Maryland Center for Environmental Science, Horn Point Laboratory, PO Box 775, Cambridge, Maryland 21613, U.S.A.
Harmful Algae. 2022 Mar;113:102203. doi: 10.1016/j.hal.2022.102203. Epub 2022 Feb 25.
Blooms of dinoflagellate Karlodinium veneficum are widely distributed in estuarine and coastal waters and have been found to cause fish kills worldwide. K. veneficum has a mixed nutritional mode and relies on both photosynthesis and phagotrophy for growth; it is a mixotroph. Here, a model of mixotrophic growth of K. veneficum (MIXO) was developed, calibrated with previously-reported laboratory physiological data, and subsequently embedded in a 3D-coupled hydrodynamic (ROMS)-biogeochemical (RCA) model of eutrophic Chesapeake Bay, USA. The resulting ROMS-RCA-MIXO model was applied in hindcast mode to investigate seasonal and spatial distributions. Simulations showed that K. veneficum blooms occurred during June-August and were confined to the upper and middle Bay, consistent with long-term field observations. Autotrophic growth dominated in spring but heterotrophic growth dominated during the summer. The number of prey ingested by K. veneficum varied from 0.1 to 0.6 day and the food vacuole content reached up to 50% of the core mixotroph biomass. The ingestion rate increased with prey density and also when P:N ratio fell below ∼0.03 (N:P ∼ 33), indicating that K. veneficum only switched to mixotrophic feeding in P-deficient waters when sufficient prey were available; this occurred during the summer months. The digestion rate increased with both the food vacuole content and temperature. The modeling analysis affirms K. veneficum as a phagotrophic 'alga' which is primarily photosynthetic but switches to mixotrophic feeding under nutrient deficient conditions.
卡氏裸甲藻的藻华广泛分布于河口和沿海水域，并已在全球范围内发现其导致鱼类死亡。卡氏裸甲藻具有混合营养模式，依赖光合作用和吞噬作用来生长；它是一种混合营养体。在此，建立了卡氏裸甲藻混合营养生长模型（MIXO），并用先前报道的实验室生理数据进行了校准，然后将其嵌入到美国富营养切萨皮克湾的三维耦合水动力（ROMS）-生物地球化学（RCA）模型中。所得到的 ROMS-RCA-MIXO 模型被应用于回溯模式，以研究季节和空间分布。模拟表明，卡氏裸甲藻藻华发生在 6 月至 8 月，局限于湾的上部和中部，与长期的现场观测一致。自养生长在春季占主导地位，但异养生长在夏季占主导地位。卡氏裸甲藻摄入的猎物数量从 0.1 到 0.6 天不等，食物泡含量达到核心混合营养体生物量的 50%。吞噬率随猎物密度的增加而增加，当 P:N 比下降到约 0.03（N:P~33）以下时也会增加，这表明只有在有足够的猎物时，卡氏裸甲藻才会在磷缺乏的水域中切换到混合营养摄食；这发生在夏季。消化率随食物泡含量和温度的增加而增加。该建模分析证实卡氏裸甲藻是一种吞噬性“藻类”，它主要是光合作用的，但在营养缺乏的条件下会切换到混合营养摄食。
