LTER: Land/Ocean Interactions and the Dynamics of Kelp Forest Ecosystems

本研究将在加利福尼亚州圣巴巴拉建立一个LTER（长期生态研究）站点，重点关注陆地/海洋边缘的生态系统。这个位置是许多半干旱地区的典型，因为它包括大量的流域，这些流域的大小和土地使用情况各不相同。重点沿海生态系统将是巨藻（Macrocystis pyrifera）森林，这是极其重要的生态和经济的沿海地区沿着北美和南美的西海岸。海带森林生长在浅海岸的珊瑚礁上，通过来自这些不同来源的水携带成分（例如沉积物、营养物、幼虫、污染物）的移动，受到陆地和公海的积极和消极影响。海带森林具有独特的营养结构，其中生产者（大型藻类）和消费者（过滤浮游生物的固着无脊椎动物）争夺空间。大型藻类和固着无脊椎动物之间的竞争可以通过对珊瑚礁的营养物质和颗粒有机物的相对供应来调节。 虽然有几条证据表明，陆地径流对圣巴巴拉海峡海藻林的影响可能很大，但对该地区陆地与海洋衍生成分在构建该生态系统和其他沿海生态系统方面的相对贡献知之甚少。22名研究人员协调的跨学科研究将检查与LTER站点共享的所有五个核心研究领域相关的问题和假设。将具体讨论的关键问题是（1）陆地径流和海洋强迫扰动海带森林生态系统的时空尺度，（2）生态系统中有机物质的模式和处理，（3）有机和无机投入的模式及其从陆地到沿海地区的移动，（4）陆地径流对海带森林初级生产力的格局和控制的影响;（5）陆地径流对海带森林关键物种的长期种群动态和营养相互作用的影响。区域研究将结合联合收割机卫星图像和3个主要和12个次要流域流量的实地测量，并建立溶质和沉积物-流量关系模型，以确定进入圣巴巴拉海峡的径流模式。将在三个主要流域进行详细的水化学取样和短期和长期实验，以确定对控制向沿海沃茨的总体输出至关重要的较小规模的过程。卫星图像结合洋流，波浪，悬浮沉积物，次表层辐照度和海水化学的详细测量，从三个主要集水区近海海带床的系泊仪器收集，将用于确定沿海区径流的时间，空间范围和停留时间以及它们被海洋过程修改的程度。 径流对初级生产模式的影响将调查浮游植物和大型藻类（海带森林中发现的两大主要初级生产者）。将根据从系泊仪器和卫星收集的光学数据、从系泊仪器和海洋航行收集的叶绿素浓度数据以及C14吸收实验来估计浮游植物产量。海带生产将估计从现场测量的增长和生存的标记个人和空中照片的表面树冠面积。将进行实验，以评估控制初级生产的因素以及它们受陆地和海洋过程影响的程度。短期和长期的实验和建模将进行，以确定在何种程度上的营养供应的变化，由于径流改变独特的食物网的营养相互作用。

This study will establish an LTER (Long-Term Ecological Research) site in Santa Barbara, CA that will focus on ecological systems at the land/ocean-margin. This location is typical of many semi-arid regions in that it includes a large number of watersheds with episodic stream flow that vary in size and land use. The focal coastal ecosystem will be giant kelp (Macrocystis pyrifera) forests, which are extremely important to the ecology and economy of coastal areas along the West Coast of North and South America. Kelp forests occur on shallow coastal reefs and are affected in both positive and negative ways by land and open ocean through the movement of water carrying constituents (e.g. sediments, nutrients, larvae, pollutants) from these different sources. Kelp forests have a unique trophic structure in which producers (macroalgae) and consumers (sessile invertebrates that filter plankton) compete for space. Competition between macroalgae and sessile invertebrates can be mediated by the relative supply of nutrients and particulate organic matter to the reef. Although several lines of evidence suggest that the effects of terrestrial runoff on kelp forests in the Santa Barbara Channel can be large, the relative contributions of land vs. ocean derived constituents in structuring this and other coastal ecosystems in the region is poorly understood. Interdisciplinary research coordinated among 22 investigators will examine questions and hypotheses related to all five core areas of research shared by LTER sites. The key issues that will specifically be addressed are (1) spatial and temporal scales over which terrestrial runoff and ocean forcing perturbs kelp forest ecosystems, (2) patterns and processing of organic matter in the ecosystem, (3) patterns of organic and inorganic inputs and their movement from the land to the coastal zone, (4) the effects of terrestrial runoff on patterns and controls of primary production in kelp forests, and (5) the effects of terrestrial runoff on the long-term population dynamics of key kelp-forest species and on trophic interactions. Regional studies will combine satellite imagery and field measurements of discharge from 3 primary and 12 secondary watersheds with modeling of solute and sediment-discharge relationships to determine patterns of runoff entering the Santa Barbara Channel. Detailed sampling of water chemistry and short and long-term experiments will be done in the three primary watersheds to determine smaller scale processes that are critical in controlling overall export to coastal waters. Satellite imagery combined with detailed measurements of ocean currents, waves, suspended sediment, subsurface irradiance, and seawater chemistry collected from moored instruments in the kelp beds offshore of the three primary catchments will be used to determine the timing, spatial extent, and residence time of runoff in the coastal zone and the degree to which they are modified by ocean processes. The effects of runoff on patterns of primary production will be investigated for both phytoplankton and macroalgae (the two major groups of primary producers found in kelp forests). Phytoplankton production will be estimated from optical data collected from moored instruments and satellites, chlorophyll concentration data collected from moored instruments and ocean cruises and C14 uptake experiments. Kelp production will be estimated from in situ measurements of growth and survival of tagged individuals and aerial photos of surface canopy area. Experiments will be done to evaluate factors that control primary production and the degree to which they are influenced by land and ocean processes. Short and long-term experiments and modeling will be performed to determine the extent to which changes in nutrient supply due to runoff alter trophic interactions of the unique food web.