Research in the Ambrose lab encompasses a wide variety of habitat types and taxa, but most research focuses on the effects on humans on ecosystem health and ways to mitigate those impacts. By conducting research at the interface of science and policy, we have been able to make valuable contributions to issues such as resource mitigation, restoration, and wetland regulation.
  Most of my previous research has centered on natural ecosystems, albeit often ecosystems that have been substantially affect by human activities. Recently I began focusing on urban environments to evaluate the ecological functions and values that exist in cities, how these could be expanded by new management actions, and how ecological systems could be used to make cities more sustainable. This research dovetails nicely with UCLA’s new Sustainable Los Angeles Grand Challenge initiative.
  This page describes some of the current research being conducted in the lab, but it is only a sample of the range of topics studied, especially by graduate students. Brief descriptions about these projects can be found on the People page.

Determining Long-Term Changes in Species Abundances and Community Structure in Southern California Rocky Intertidal Habitats

 Our monitoring and assessment research aims at detecting both long-term (as from global climate change) and short-term (as from oil spills,stormwater discharges, etc.) changes in ecological communities. Several projects involve collecting baseline information on coastal resources. Since 1991 we have been studying rocky intertidal habitats in Santa Barbara County. In 1994, the studies were extended to Los Angeles and Ventura Counties and the northern Channel Islands, and since then the network of sites has developed into the Multi-Agency Rocky Intertidal Network (MARINe; see www.marine.gov and www.pacificrockyintertidal.org) with many agencies and scientists monitoring hundreds of sites along the west coast of North America. These studies have been funded primarily to provide baseline information about resources in case there is an oil spill along this section of coast. If a major spill should occur, these data would be invaluable for assessing the impacts of the spill, and would form the basis for studies of the recovery of the communities from the spill. In fact, these monitoring data in conjunction with new data collected by the same team of researchers has been used extensively in assessing the effects of several oil spills, including the Torch oil spill in San Luis Obispo County, the Cosco Busan oil spill in San Francisco Bay, and the recent pipeline spill in Santa Barbara County. In addition, there are at least three additional benefits from this research. First, these data are the beginning of a dataset that can be used to detect long-term changes in ecological communities. Concerns about global climate change, cumulative impacts, and other factors have highlighted the need for long-term ecological data, yet there are surprisingly few datasets available, especially for coastal communities. Second, we have been working to develop monitoring methodologies and approaches that can be employed in coastal habitats worldwide. Some of these methodologies were implemented in the Cosco Busan post-spill assessment. Finally, this research will be used to help elucidate important basic ecological processes, particularly in intertidal and wetland communities. Several papers have already been published from this work, but the richness of the data set improves with time, so we expect many more publications from this effort.

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Restoration and Mitigation

 Our studies on mitigation and restoration include the development and evaluation of techniques for mitigating impacts of coastal developments, especially techniques for restoring or enhancing coastal habitats. Mitigation is one of the most controversial aspects of the continued development and use of natural resources. Much of the controversy stems from an inadequate scientific basis for mitigation decisions, so we have been working to develop the science of mitigation. This effort includes an ambitious research program to assess the effectiveness of wetland mitigation projects throughout California. This research expands on studies conducted by several Environmental Science and Engineering students, particularly Mark Sudol, who has served as Chief of the Regulatory Branch of the U.S. Army Corps of Engineers. We have evaluated the effectiveness of the main wetland protection laws and policies (especially Sections 401 and 404 of the Clean Water Act) by assessing how well mitigation projects comply with the conditions of 401 and 404 permits, as well as how the ecological functioning of the mitigation sites compare to natural wetlands. Our state-wide field assessment was unprecedented in scope and has provided both an important evaluation of the effectiveness of mitigation projects and guidance on how to modify policies and procedures to improve the success of wetland mitigation. The results of this study have already resulted in new policies for wetland protection at the state level, and continue to influence wetland mitigation activities on the federal and state level.

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Effects of Climate Change

 With increasing concern about climate change and the particular vulnerability of coastal communities, research related to coastal wetlands and climate change is critically important. We are addressing three main areas: (1) the effects of climate change on coastal wetland habitats, particularly vegetation patterns; (2) tools for climate change adaptation in coastal wetlands, and (3) the potential for mitigation climate change by sequestering carbon in coastal wetlands.
 We are undertaking a range of studies assessing the likely effects of climate change, especially sea level rise, on coastal wetlands. We use laboratory experiments, field observations, and physical models to predict the stability of salt marshes in the face of sea level rise and how sea level rise is likely to affect the distribution of vegetation communities in coastal wetlands.
 Although the elevation of the marsh plain of coastal wetlands is influenced by many factors, the ability of a wetland to accrete (add) sufficient sediment to maintain its position in the face of rising sea level will be critical for maintaining salt marsh habitats. We are studying sediment accretion through a variety of approaches. In collaboration with Glen MacDonald’s lab, we have been studying accretion rates through the entire lifetimes of California salt marshes, a period of several hundred years in most marshes. We have also been using marker horizons (feldspar plots) and sediment stakes to examine contemporary accretion rates. We use suspended sediment samplers and physical modeling to examine sediment flux in different coastal wetlands. To date, these results have documented a range of accretion rates in different wetlands, with some wetlands unlikely to keep pace with predicted sea level rise over the next few decades while others may be able to maintain their marsh plain elevations for a longer period. In all cases, this information is critical for management decisions about managing sediment inflow to wetlands as a climate change adaptation strategy.
 In addition to sediment dynamics as related to climate change, we have assessed the likely response of vegetation to climate change. The rising sea level will change the inundation regime in tidal salt marshes, so we have been examining the relationship between inundation patterns and plant distributions in southern California salt marshes. We are currently conducting mesocosm experiments linking different inundation patterns to plant physiological performance (i.e., photosynthesis) and physiological stress. These studies will provide information needed to refine current models of vegetation response to sea level rise.

Adaptation to Climate Change

 Studies on adaptation to climate change examine ways to minimize the ecological effects of climate change. For coastal wetlands, there are limited opportunities for adaptation to climate change, particularly sea level rise. The main mechanism by which coastal wetlands adapted to paleoclimate changes was by migrating landward (transgression) or seaward as sea level rose or fell. In southern California, changes in land use have eliminated most opportunities for transgression.
 If transgression is not possible, the main mechanism by which coastal wetlands can adapt to sea level rise is by increasing elevation of the marsh plain. As discussed above, many factors influence the elevation of a marsh plain but sediment accretion is a major factor influencing wetland resilience, and the studies described above examine this factor. Where sediment supply from the watershed is high, natural accretion may be sufficient to maintain the stability of marsh plains. In many cases, changes in land use in the watershed or hydrologic connectivity to the wetland have reduced sediment supply, but even if that is not the case, sea level is likely to rise faster than southern California salt marshes can adjust to by the end of the century. In these cases, more active management may be necessary to prevent the disappearance of salt marshes.
 Thin layer sediment augmentation is one active management technique that could increase the resilience of salt marshes to sea level rise, but very little research has been done on this technique and it has never been applied in southern California. In collaboration with the Seal Beach National Wildlife Refuge, USGS, Cal State Long Beach, and the California Coastal Conservancy, we are studying an experimental thin layer sediment augmentation project in the Seal Beach wetland. Our focus is on sediment dynamics after the sediment is added and possible geomorphic changes, such as changes to tidal creeks. The results of this pilot experiment will be used to inform managers about the feasibility of using dredged materials to improve the long-term stability of southern California salt marshes.

Climate Change Mitigation - Carbon Sequestration

 Climate change mitigation techniques either reduce the amount of greenhouse gases emitted to the atmosphere or remove carbon dioxide from the atmosphere. There is a great deal of interest in using natural ecosystems to take up carbon, and recent attention has been paid to “blue carbon,” the carbon sequestered by marine and coastal ecosystems. We are evaluating the potential for using coastal wetlands to sequester carbon as a strategy to mitigate greenhouse gas emissions. It is known that wetlands are among the most effective habitats for sequestering carbon, but virtually nothing is known about carbon sequestration rates in the type of coastal wetland occurring in southern California and other Mediterranean-type regions of the world, and very little is known about carbon sequestration rates in restored wetlands anywhere. Through extensive field collections, we are assessing carbon sequestration rates in natural and restored coastal wetlands in southern California. The carbon sequestration research has particularly important state and international policy implications because of the great interest in a carbon market (which has recently been developed in California as part of the implementation of AB32, which would mean that carbon sequestration in wetlands would have potentially large economic consequences.

Ecological Aspects of Stormwater Management

  This work started with my 2012 Science paper, with the co-authors (led by Stan Grant at UC Irvine) subsequently receiving an NSF PIRE (Partnership in International Research and Education) grant. Our overall goal is to improve urban water sustainability by promoting low energy treatment of wastewater (defined broadly to include grey water and stormwater) by, for example, constructed wetlands or stormwater biofilters. My own focus is on ecological aspects of stormwater biofilters, which include rain gardens, bioswales and bioretention systems. We have drawn on the extensive experience Melbourne, Australia, has from grappling with an extended drought called the Millennium Drought.
  My postdoc Brandon Winfrey and I have a number of current research projects in southern California. We have just completed an intensive laboratory experiment in Melbourne using laboratory mesocosms to assess the effects of harvesting biofilter vegetation on the effectiveness of the biofilters. These experiments were collaborations with Lisa Levin and Andrew Mehring at Scripps Institution of Oceanography, who focused on the effects of soil fauna (earthworms). We are conducting similar mesocosm experiments at UCLA looking at the effects of different native plant species, saturated zones, and different watering regimes on biofilter performance. In addition to these experiments, we are conducting studies of installed biofilters. We have looked at some aspects of the microbial communities in biofilters in Australia and southern California as well as the occurrence of different plant species.
  The goal of these studies is to understand how ecological components of stormwater retention systems (plants, soil animals, soil microbes) affect the performance of these systems in terms of retaining runoff and removing pollutants, but also how these systems can enhance the ecological values and ecosystems services in urban and suburban environments. Stormwater retention systems are a critical element in urban water sustainability, and their contribution to local water supply is increasingly being recognized, but their contribution to ecological sustainability is generally not appreciated. Through our research, we hope to influence stormwater biofilter design to improve urban ecosystem services as well as local water supply and water quality.

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Effects of Urbanization on Aquatic Ecosystems

  We are interested in the factors influencing the health of aquatic ecosystems. Being based in Los Angeles, we focus on the effects of urbanization on aquatic ecosystems. We have studied stream fish, benthic macroinvertebrates, and algae in coastal watersheds with different levels of urbanization and different land uses. One common stressor is excess nutrients, and we have examined factors influencing the development of nuisance algal cover. Some of this research was conducted in collaboration with engineers in UCLA’s Center for Embedded Network Sensors (CENS), utilizing novel sensor systems to acquire data on a finer temporal and spatial scale than was previously possible, thus providing new insights into the dynamics of nutrient fluxes in the Malibu Creek watershed. We have also evaluated the influence of the pervasive invasive species giant reed (Arundo donax) on riparian communities, demonstrating its effect on wildfires, competition with other species, and facilitation by nutrients in urbanized watersheds.

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