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

这项研究将在加州圣巴巴拉建立一个长期生态研究站点，重点研究陆地/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，其大小和土地利用各不相同。巨型海带（Macrocystis pyrifera）森林将成为重点沿海生态系统，对南北美洲西海岸沿海地区的生态和经济至关重要。海带林生长在浅海沿岸珊瑚礁上，并受到陆地和开阔海洋的积极和消极影响，这些影响来自不同来源的携水成分（如沉积物、营养物、幼虫、污染物）的移动。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（过滤浮游生物的无根无脊椎动物）争夺空间。大型藻类和无根无脊椎动物之间的竞争可以通过向珊瑚礁提供营养物质和颗粒有机物的相对供应来调节。尽管有几条证据表明，陆地径流对圣巴巴拉海峡海带森林的影响可能很大，但人们对陆地和海洋成分在构建该地区的这一生态系统和其他沿海生态系统方面的相对贡献知之甚少。由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。将具体解决的关键问题是：(1)陆地径流和海洋强迫干扰海带森林生态系统的空间和时间尺度；(2)生态系统中有机质的模式和加工；(3)有机和无机输入的模式及其从陆地向沿海地区的移动；(4)陆地径流对海带森林初级生产的模式和控制的影响；(5)陆地径流对关键海带林物种长期种群动态和营养相互作用的影响。区域研究将结合卫星图像和3个主要流域和12个次要流域的实地测量，并模拟溶质和沉积物-排放关系，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水域的全部出口至关重要的小规模过程。卫星图像与从三个主要集水区近海海带床上的系泊仪器收集的洋流、波浪、悬浮沉积物、地下辐照度和海水化学的详细测量相结合，将用于确定沿海地区径流的时间、空间范围和停留时间，以及它们被海洋过程改变的程度。将调查径流对浮游植物和大型藻类（在海带森林中发现的两大类初级生产者）初级生产模式的影响。浮游植物产量将根据从系泊仪器和卫星收集的光学数据、从系泊仪器和海洋巡航收集的叶绿素浓度数据以及C14吸收实验来估计。海带产量将根据标记个体的生长和存活的原位测量和表面冠层面积的航空照片来估计。将进行试验，评价控制初级生产的因素及其受陆地和海洋过程影响的程度。将进行短期和长期实验和建模，以确定径流引起的营养供应变化在多大程度上改变了独特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.