Long-term and interactive effects of seaweed diversity and herbivory on intertidal community structure and functioning

受地球大多数生态系统生物组成和丰富度迅速变化的部分刺激，相当多的理论和经验研究侧重于了解物种丰富度对群落和生态系统的影响。这项研究取得了重大进展，并表明多样性可以影响生态系统过程。然而，我们目前对这些超越生态系统的影响得出一般性结论并将这些知识应用于养护和管理工作的能力有限，因为：(1)大多数实验持续时间短，相对较少的实验是在自然基质上的田间条件下进行的；(2)大多数实验只操纵多样性，因此无法评估相对于其他已知生态系统功能驱动因素的多样性强度。之前NSF资助的工作发现，海藻的物种多样性确实增加了生产者生物量的积累，以及与这些海藻相关的可移动无脊椎动物的多样性和丰富度。在这个项目中，调查者将通过(A)继续我们正在进行的多样性操作(B)在这些地块内建立更多的控制食草动物的实验，以及(C)进行新的实验来检查食草动物丰富度对藻类组合的影响，来研究植物和食草动物丰富度对海藻生产力和群落从干扰中恢复的交互影响。主要实验包括加利福尼亚州博德加湾岩石潮间带72个直径1.5m的样地，分为6个不同的处理：4种藻类的单一养殖，每种藻类占本系统藻类覆盖率的85%；4种藻类的混养，以及未经操纵的控制区。PI通过在前一笔NSF拨款的赞助下除草，创造了这些“多样性”地块。该项目的目标是：(1)在多样性小区内筑巢，允许或禁止食草动物进入的较小空旷区域，以测试藻类多样性和草食对藻类群落从干扰(或恢复)中恢复的交互影响。(2)进行单独的添加剂和置换组合系列实验，以研究草食动物的特性和丰富度对藻类补充和演替的影响。(3)在巢式除草试验进行期间，继续在这些地块的未清理部分除草和收集数据，继续测试藻类丰富度对藻类和固着无脊椎动物盖度以及移动无脊椎动物丰富度、丰富度和多样性的单变量影响。结合以前的结果，这将产生一个关于海藻丰富度对岩石潮间带群落影响的7年记录，然后将与存档的环境数据相关联。(4)在巢式捕食者排除实验完成后，停止除草并追踪杂草物种的重新入侵，以评估维持多年生藻类多样性的机制。了解捕食者丰度或多样性和藻类多样性同时变化的后果以及两者对藻类群落面对干扰的恢复能力的长期影响，将有助于更好地理解人类入侵这些生境的后果，以及为最大限度地减少影响和维持生态系统功能所需的适当管理措施。考虑到人类的收获和践踏正在改变加州岩石潮间带草食动物和藻类的多样性和组成，这一点尤其关键。PI最近向加利福尼亚州的立法和机构工作人员简要介绍了NSF之前关于海洋生物多样性后果的工作结果，因此政策制定者感兴趣。PI将继续与COMPASS和Aldo Leopold Leopold领导力计划等外展组织合作，帮助将这项研究的结果尽可能广泛地传播给普通公众和决策者。此外，通过博德加海洋实验室开放日和访问当地学校等外联工作，调查员将继续促进公众对维护生物多样性的重要性以及更广泛地了解科学是如何运作的认识。最后，该项目将培养未来的科学家，包括一名技术人员、研究生和本科生研究人员，包括那些来自代表性不足的群体的人。

Stimulated in part by rapid changes in the biological composition and richness of most of Earth's ecosystems, considerable theoretical and empirical research has focused on understanding the effects of species richness on communities and ecosystems. This research has resulted in major advances and has shown that diversity can affect ecosystem processes. However, we are currently limited in our ability to draw generalities regarding these effects that transcend ecosystems and to apply this knowledge to conservation and management efforts because: (1) most experiments are of short duration and relatively few are conducted under field conditions on natural substratum; and (2) most experiments manipulate only diversity and so cannot assess the strength of diversity relative to other known drivers of ecosystem functioning. Previous NSF-funded work found that species diversity of seaweeds does increase the accumulation of producer biomass and the diversity and richness of mobile invertebrates associated with those seaweeds. In this project, the investigator will examine the interactive effects of plant and grazer richness on seaweed productivity and assemblage recovery from disturbance by (a) continuing our ongoing diversity manipulations (b) nesting additional experiments manipulating grazers within these plots, and (c) performing new experiments to examine effects of grazer richness on algal assemblages. The main experiment consists of 72 1.5 m diameter plots in the rocky intertidal at Bodega Bay, California, split into 6 different treatments: a monoculture of each of the 4 algal species that comprise 85% of the algal cover in our system; a 4-species polyculture, and an unmanipulated control plot. The PI created these "diversity" plots by weeding under the auspices of a previous NSF grant. Objectives of this project are: (1) To nest within the diversity plots smaller cleared areas that either allow or prohibit access by grazers in order to test the interactive effects of algal diversity and herbivory on recovery of the algal assemblage from disturbance (or resilience). (2) To conduct a separate combined additive and replacement series experiment to examine the effects of herbivore identity and richness on algal recruitment and succession. (3) While the nested grazer-exclusion experiment is in progress, to continue weeding and collecting data in the uncleared portion of these plots as a continued test of the univariate effect of algal richness on the cover of algae and sessile invertebrates, and on mobile invertebrate abundance, richness, and diversity. Together with previous results, this will produce a 7 year record of the effects of seaweed richness on rocky intertidal communities, which will then be correlated with archived environmental data. (4) After the nested grazer exclusion experiment is complete, to cease weeding plots and track their reinvasion by weeded species in order to evaluate the mechanisms maintaining diversity of perennial algae.Understanding the consequences of simultaneous changes in grazer abundance or diversity and algal diversity as well as the long-term effects of both on the resilience of algal communities in the face of disturbance will provide a better understanding of both the consequences of human encroachment into these habitats and the appropriate management efforts needed to minimize impacts and maintain ecosystem functioning. This is especially critical given that harvesting and trampling by humans are altering the diversity and composition of herbivores and algae in the California rocky intertidal zone. The PI recently briefed legislative and agency staff in California on the results of previous NSF work on the consequences of marine biodiversity, so there is interest from policymakers. The PI will continue to work with outreach groups like COMPASS and the Aldo Leopold Leadership Program to help disseminate the findings of this research as broadly as possible to the general public and decision-makers. In addition, through outreach efforts such as the Bodega Marine Lab Open House and visits to local schools the investigator will continue to foster public understanding of the importance of maintaining biodiversity and more generally of how science works. Finally, this project will develop future scientists including a technician, graduate and undergraduate researchers including those from underrepresented groups.