LTREB: Interannual Variability, Food-Web Interactions, and Climatic Forcing at Castle Lake

在LTREB资助更新的请求中，主要研究者描述了之前在加州城堡湖支持的多年全湖食物网实验的结果。 然后，研究人员概述了一个持续的全湖操作的设计。 该项目采用了可追溯到1959年的夏季初级生产动态的连续记录。 研究人员通过改变虹鳟鱼（Oncorhynchus mykiss）的放养率来操纵城堡湖食物网，从三年期（1989-1991）的每年零鱼到接下来三年期（1992-1994）的每年30，000鳟鱼（或三倍背景率）。 他们用三变量模型解释了城堡湖初级生产力年际变化的77%.这是由总降水量和冬季降雪量的负相关关系和一个积极的一年的时间滞后。 全湖食物网的操纵产生扰动，在平均年初级生产的规模相当于那些看到的气候变量。 在1989- 1994年干旱期间，年平均初级生产值达到或高于1959年以来的最高值。 虽然其他研究人员已经研究了这个和其他湖泊食物网的微生物成分之间的营养相互作用，但尚未对整个湖泊气候和食物网过程中的微生物动力学进行直接比较。 持续的LTREB支持将使调查人员能够完成第二阶段的调查（每年放养30，000条鳟鱼），并进行新一轮的低和高鳟鱼放养率操作。 他们还将监测食物网的微生物组成部分（细菌，微型浮游生物，混合营养浮游植物，异养鞭毛虫和纤毛虫）到未来的全湖监测，食物网操纵。拟议的调查将跨越各种空间和时间尺度，将通过长期气候变化加强对整个湖泊食物网和微生物动态的了解。

In this request for an LTREB grant renewal the principal investigators describe results of previously supported multi-year whole-lake food web experiment at Castle Lake, California. The investigators then outline a design for continued whole-lake manipulations. The project incorporates a continuous record of summer primary production dynamics dating back to 1959. The investigators manipulated the Castle Lake food web by varying rainbow trout (Oncorhynchus mykiss) stocking rates from zero fish per year for a three-year period (1989-1991) to 30,000 trout per year ( or three times background rates) for a following three-year period (1992-1994). Using a three- variable model they explained 77% of the interannual variability in Castle Lake primary production. This was regulated by negative relationships with total precipitation and winter snowfall and a positive one-year time lag. Whole-lake food web manipulations produced perturbations in mean annual primary production on a scale comparable to those seen for the climatic variables. During the drought, 1989-94, mean annual primar y production values were at or higher than the highest values seen since 1959. While trophic interactions among the microbial components of this and other lake food webs have been studied by other researchers, but direct comparisons of microbial dynamics in response to whole-lake climatic and food web processes have not been made. Continued LTREB support will allow the investigators to complete Phase II of their investigation (30,000 trout stocked per year), and conduct a new cycle of low and high trout stocking rate manipulations. They also will monitor microbial components of the food web (bacteria, picoplankton, mixotrophic phytoplankton, heterotrophic flagellates, and ciliates) into future whole-lake monitoring, food web manipulations. The proposed investigations will span a variety of spatial and temporal scales that will enhance understanding of whole-lake food web and microbial dynamics through longer term climate changes.