DISSERTATION RESEARCH: Testing carbon limitation of cave stream ecosystems via a whole-reach detritus addition

本研究的总体目标是确定能量的可用性是否限制了洞穴溪流生态系统中的生物活动。在洞穴生态系统中，处于食物网底层的资源，也就是潜在地控制整个生物活动的资源，是死亡的有机物（如枯叶、枯枝和枯木，以下简称腐质）。因为进入洞穴系统的物理开口很少，冲进洞穴的碎屑量通常很低，所以洞穴群落被认为是能量有限的。然而，这种能量限制假说从未被验证过，尽管它是对洞穴生态、进化和保护的科学理解的核心。这项研究被设计为对这一假设的第一次严格检验。这项研究的设计非常简单：从2010年2月开始，将玉米凋落物（玉米收获后剩下的叶子、秸秆和谷壳）添加到100米长的洞穴溪流中（杰克逊公司Bluff River cave）。与上游参考河段（不接收凋落物）相比，溪流群落对这一增加的能量的反应将被跟踪一年。此外，已经从两个地区收集了一年多的操纵前数据（2008年10月至2010年2月）。将每月收集样本，以跟踪物种组成、丰度和生长的变化，以及将玉米衍生物质纳入动物组织。这项研究将检查洞穴流的整个食物网的反应，从最基础的消费者（细菌和真菌消耗自然碎屑和添加的玉米垃圾）到顶级捕食者（洞穴小龙虾和蝾螈）。因此，这项研究不仅是第一个测试能量限制假说的研究，也是第一个在很长一段时间内描述洞穴溪流食物网的研究。这项研究的结果将对各种个人和组织有价值。保护人员和洞穴保护组织将使用对极度濒危的田纳西洞穴蝾螈（Gyrinophilus palleucus）和洞穴小龙虾（Cambarus tenebrosus和濒危的Cambarus hamulatus）获得的生活史信息（生长速度和成熟时间）。洞穴系统是研究和监测地下水系统的窗口。因此，一般科学界和整个社会将受益，因为地下水系统知之甚少，但含有地球上约99%的液态淡水，并提供重要的生态服务，包括维持地表水生生态系统，水供应的自然净化，以及维持许多高度地方性和濒危物种。这项研究的结果将通过科学（期刊文章、报告和口头陈述）和公共途径（与洞穴团体、土地所有者、州和联邦机构以及K-12教育工作者的互动）进行分享。作为该项目的一部分，已经为当地高中生制定了一份课程计划，其中教授洞穴和地下水生态学的基本原理，说明生态和进化如何相互作用以构建洞穴群落，并介绍了以碎屑为基础的食物链的概念。为了让更多的学生接触到这些材料，整个课程计划（即指导、讲座和活动）将分发给当地的高中教师。

The overall goal of this study is to determine whether the availability of energy limits biological activity in cave stream ecosystems. In cave ecosystems, the resource at the base of the food web, and thus the resource that potentially controls overall biological activity, is dead organic matter (e.g. dead leaves, twigs, and logs, hereafter referred to as detritus). Because there are few physical openings into cave systems, the amount of detritus washed into caves is typically very low, so cave communities are assumed to be energy-limited. However, this energy-limitation hypothesis has never been tested, despite it being central to scientific understanding of cave ecology, evolution, and conservation. This study has been designed to be the first rigorous test of this hypothesis. The study design is elegantly simple: corn litter (leaves, stalks, and husks leftover from corn harvest) were added to a 100-m reach of a cave stream (Bluff River Cave, Jackson Co., AL) beginning in February 2010. The response of the stream community to this addition of energy will be followed for one year relative to that of a reference reach upstream (which will receive no litter). Additionally, over one year of pre-manipulation data (October 2008 to February 2010) has already been collected from both reaches. Samples will be collected monthly to track changes in species composition, abundance, and growth, as well as the incorporation of corn-derived material into animal tissue. This study will examine the response of the entire food web of the cave stream, from the most basal consumer (the bacteria and fungi that consume natural detritus and the added corn litter) to top predators (cave crayfish and salamanders). Thus, not only is this study the first to test the energy-limitation hypothesis, but it is also the first to characterize a cave stream's food web over an extended period of time. The results from this study will be valuable to various individuals and organizations. Conservation personnel and cave conservation groups will use the life history information (growth rates and time to maturity) obtained for the critically threatened Tennessee cave salamander (Gyrinophilus palleucus) and cave crayfishes (Cambarus tenebrosus and the imperiled Cambarus hamulatus). Cave systems are a window through which groundwater systems can be studied and monitored. Thus the general scientific community and society at large will benefit because groundwater systems are poorly understood but contain about 99% of all liquid freshwater on the planet, and provide important ecological services, including sustaining surface aquatic ecosystems, natural purification of water supplies, and maintenance of many highly endemic and endangered species. Results from this study will be shared both through scientific (journal articles, reports, and oral presentations) and public avenues (interactions with caving groups, landowners, state and federal agencies, and K-12 educators). As part of this project, a lesson plan for local high-school students has been developed, which teaches basic principles of cave and groundwater ecology, illustrates how ecology and evolution interact to structure cave communities, and introduces the concept of detritus-based food chains. To increase the number of students exposed to this material, the entire lesson plan (i.e., instructions, lectures, and activities) will be disseminated to local high-school teachers.