Trophic Interactions of Ambush Predator Dinoflagellates in Estuarine Microbial Food Webs

各种异养鞭毛藻包括自由生活的河口物种，它们对藻类、原生动物或鱼类猎物表现出“伏击捕食者”的行为。这种行为模式很普遍；到目前为止，地中海、墨西哥湾和西大西洋都有报道。在过去的两年中，发现了一种新的伏击捕食者鞭毛虫属，Pfiesteria (nov. gen.)，已知的物种有一个复杂的生命周期，包括至少15个阶段。在这些阶段中，有持久的变形虫异养生物和短暂的“幽灵般的”鞭毛虫，它们常见于富营养化的大西洋中部和墨西哥湾沿岸河口，并可能广泛分布于暖温带和亚热带水域。这些阶段在水柱和沉积物中普遍存在和丰富，它们对细菌、藻类和微动物猎物的贪婪吞噬，以及它们对鱼类的致命性，表明伏击捕食者鞭毛藻在河口食物网的结构和功能中起着重要作用。本项目旨在通过实验研究Pfiesteria piscimorte （nov. gen. et sp.）作为一种具有代表性的有毒伏击捕食者的丰富阶段的营养生态学和营养相互作用，以确定这些生物在河口食物网中的多种形式的作用。本项目将：(1)研究双鞭毛虫和变形虫对鳍鱼猎物刺激性分泌物的腐殖性营养；(2)描述了Pfiesteria （11 . gen.）与细菌、藻类和微动物猎物之间的吞噬作用；(3)确定双鞭毛虫和变形虫阶段对代表性微生物捕食者的影响。从这项研究中获得的见解将改变关于甲藻在富营养化暖温带河口食物网结构和功能中的作用的一般范例。

BURKHOLDER 9403920 The diverse heterotrophic dinoflagellates include free- living estuarine species that demonstrate "ambush predator" behavior toward algal, protozoan, or fish prey. This behavioral pattern is widespread; thus far, it has been reported from the Mediterranean Sea, the Gulf of Mexico, and the western Atlantic. Within the past two years, a new genus of ambush predator dinoflagellate, Pfiesteria (nov. gen.) has been discovered, with known species having a complex life cycle that includes at least 15 stages. Among these stages are persistent amoeboid heterotrophs and ephemeral "phantom-like" flagellates that are common in eutrophic mid-Atlantic and Gulf Coast estuaries, and likely are widespread throughout warm temperate and subtropical waters. The ubiquitous occurrence and abundance of these stages in the water column and sediments, their voracious phagotrophy on bacterial, algal, and microfaunal prey, and their lethality to fish point to a major role of ambush predator dinoflagellates in the structure and function of estuarine food webs. This project is to experimentally examine the nutritional ecology and trophic interactions of abundant stages of Pfiesteria piscimorte (nov. gen. et sp.) as a representative toxic ambush predator, toward determining the role of these organisms -- in their many forms -- within estuarine food webs. This project will: (1) examine saprotrophic nutrition of the biflagellate and amoeboid forms on stimulatory secretions of finfish prey; (2) characterize phagotrophic interactions between Pfiesteria (nov. gen.) and bacterial, algal and microfaunal prey; and (3) determine the influence of the biflagellate and amoeboid stages on representative microbial predators. The insights gained from this research will alter general paradigms about the role of dinoflagellates in the structure and function of food webs n eutrophic warm temperate estuaries.