Since 2007, the U.S. Geological Survey (USGS) National Wetlands Research Center (NWRC) has been home to a global effort to improve management outcomes for massive deltaic coastal systems like that of the Mississippi River Delta by comparing the ecological, hydrological, geological, and biogeochemical processes of large deltaic systems across the globe. The Delta Research and Global Observation Network (DRAGON) is developing a science framework for comparing, integrating, and ultimately predicting the effects of key drivers and management practices in these large ecosystems. The DRAGON brings together scientists and managers to model the large river deltas around the world (http://deltas.usgs.gov). Forecast Mekong is part of the U.S. Department of State’s Lower Mekong Initiative, which was launched in 2008 by Secretary Clinton and the Foreign Ministers of Cambodia, Laos, Thailand and Vietnam to enhance U.S. engagement with the Lower Mekong countries in the areas of environment, health, education, and infrastructure. The USGS is using research and data from the Mekong River Delta in Southeast Asia to compare restoration, conservation, and management efforts there with those of the Mississippi River Delta in the USA. The project provides a forum to engage regional partners in the Mekong Basin countries to share data and support local research efforts. Ultimately, Forecast Mekong is intended to support more informed decisions about how to make the Mekong and Mississippi deltas resilient in the face of climate change, economic stresses, and other impacts.
This session focuses upon current and developing understanding of sources, sinks, and chemistry of chromophoric dissolved organic matter (CDOM), and the power of CDOM as an interpretive prism through which the cycling of the greater DOM pool can be resolved. CDOM is increasingly recognized as a significant component of and useful tracer for dissolved organic matter (DOM). Thus, understanding the processes that govern the spatial and temporal distributions of different pools of CDOM and fluorescent DOM (FDOM) is of importance to a comprehensive understanding of global CDOM and DOM cycles. Consequently, the distributions, production, transport and fate of CDOM are being charted throughout the oceans. Terrestrial-sources and photochemical-sinks for CDOM have long been recognized. Yet, recent research highlights the production of bio-refractory, photo-labile CDOM in the deep ocean and that CDOM and FDOM can serve as tracers of labile and refractory DOC pools. Coupling of advanced analytical techniques, such as high resolution mass spectrometry, with CDOM and FDOM datasets is revealing the molecular character of DOM’s optical signatures. Presentations detailing ocean CDOM production, photochemistry and chemical composition are welcome.
Conveners: Ruben Sommaruga, University of Innsbruck, Institute of Ecology, Innsbruck, Austria, email@example.com; Tom Battin, University of Vienna, Department of Limnology, Vienna, Austria, firstname.lastname@example.org; Eran Hood, University of Alaska Southeast, Environmental Science Program, Juneau, USA, email@example.com
The rapid current retreat of glaciers constitutes one of the most prominent signs of climate change. Most glaciers are expected to significantly shrink within a generation, and many of the glaciers at low altitude could disappear in the next 20 years. In addition to the long-term loss of natural freshwater storage and their contribution to sea-level rise, the retreat of glaciers affects aquatic ecosystems in several ways, sometimes even in a catastrophic manner such as when glacial lake outburst floods occur. Glacial ecosystems are also increasingly understood as an hitherto poorly recognized player in the global carbon cycle. The accelerated deglaciation may thus have numerous and complex consequences for downstream aquatic ecosystems and for large-scale biogeochemistry. For instance, rapid glacial retreat is creating new lakes where topography is suitable and is changing the water transparency of turbid lakes. Furthermore it is altering the ecohydrology of glacier-fed streams and may even mobilize pollutants that can be transported to downstream ecosystems. This session invites presentations that contribute to understand the consequences of vanishing glaciers for the hydrology, biogeochemistry, biodiversity, and ecological function of glacier-fed streams, lakes, and near-shore marine ecosystems.
Conveners: Alexander S. Kolker, Louisiana Universities Marine Consortium, firstname.lastname@example.org; Mead A. Allison, University of Texas Institute of Geophysics, University of Texas, email@example.com; Karen H. Johannesson, Department of Earth and Environmental Sciences, Tulane University, firstname.lastname@example.org
The complex land-ocean interface of large rivers, which includes fluvial channels, estuaries, deltaic wetlands, and the adjacent continental shelf, has a significant control on the global flux of water, sediments, organic matter, and dissolved ions to the oceans. Relative to smaller systems, their size, long life-span, and geomorphological complexity can engender unique surface and subsurface transport across the land-ocean interface, many of these exchange processes remain poorly studied. Closing these knowledge gaps for both surface fluxes and submarine groundwater discharge is critical to the development of accurate geochemical, hydrological and sediment budgets. Furthermore, these knowledge gaps have important societal implications, as large river-dominated coastal systems have large populations, are home to critical infrastructure, provide valuable ecosystem services, and are threatened by changes in land use, patterns of water utilization, climate and relative sea level. This session will explore land-ocean exchange processes in large rivers and their societal implications. Presentations that build cross-disciplinary connections from both theoretical and empirical perspectives are particularly encouraged.
Conveners: Miroslav Macek, National Autonomous University of Mexico, campus Iztac, email@example.com; Rosaluz Tavera, National Autonomous University of Mexico, Faculty of Science, firstname.lastname@example.org
Studies of spatial and annual development of autotrophic picoplankton (APP) in oligotrophic, stratified monomictic and meromictic lakes are scarce. Some studies (e.g., lakes Biwa, Kivu, Tanganyika) lacked comprehensive information on heterotrophic bacteria, protists and viruses. Even the more detailed studies (e.g., lakes Kinneret, Alchichica) also did not provide any clear explication for the high APP abundances compared to the total phytoplankton or their low rate of removal. Although APP accumulation in suboxic layers has been observed, its importance is not well understood. It has been hypothesized that water column stratification along with bottom-up control are dominant mechanisms regulating APP development, while APP removal is driven by mixotrophic flagellate- and ciliate-feeding combined with the use of sequestered APP photosynthate under an optimum light and suboxic condition. The aim of the session is to discuss up-to-date information on the annual pattern of APP and their contribution within the microbial-loop, and their relationships with limnological conditions (temperature, dissolved oxygen, photosynthetically-active radiation, nutrients) and protistan feeding. The importance of suboxic layers in these processes are of particular interest.
The future of coastal communities will depend on informed use of fresh and saltwater resources. Groundwater discharge is distinct from other coastal freshwater inputs due to its diffuse nature and in the quantity and composition of nutrients it delivers. Although the detection and quantification of coastal groundwater inputs has advanced considerably, understanding of its ecological role for microbial communities and coastal food webs has not. Groundwater-derived inputs of nutrients and organic matter are mediated by microbial communities in aquifers and sediments and play an important but under- recognized role in coastal water quality. The subsequent effect of groundwater inputs on the ecology of benthic and pelagic microbes such as phytoplankton is also poorly understood, even though it has been linked to phenomena such as harmful algal blooms (HABs). This session will address how within-aquifer microbial processes control the flux of groundwater-derived materials to coastal water bodies as well as the consequences of this flux for microbial and phytoplankton communities. Studies that integrate physical and chemical measurements of groundwater with biological processes are especially encouraged. Groundwater is often out of sight and out of mind, so studies that bring related issues into the public sphere or policy discussions are also encouraged.
Conveners: Jennifer J Mosher, Stroud Water Research Center, email@example.com; Richard Devereux, US Environmental Protection Agency, Devereux.Richard@epamail.epa.gov; Anthony V Palumbo, Oak Ridge National Lab, firstname.lastname@example.org
Aquatic ecosystems are globally connected by hydrological and biogeochemical cycles. Microorganisms inhabiting aquatic ecosystems form the basis of food webs, mediate essential element cycles, decompose natural organic matter, transform inorganic nutrients and metals, and degrade anthropogenic pollutants. The geochemical milieu determines the availability of resources that can be physiologically exploited by microorganisms. It is these interactions between the microorganisms and their resources that most likely contribute to metabolic diversity and determine whether one aquatic ecosystem is a source or sink for organic or inorganic materials with another. Understanding linkages among aquatic microorganisms, geochemical cycling, and hydrological transport is a vital step for managing anthropogenic inputs to aquatic environments and developing sustainable solutions for ecosystem protection. The goal of this session is to explore these linkages through presentations that include ecophysiological capacities of microbial communities in the transformation of matter through hydrologically connected ecosystems from streams and rivers to lakes or coastal zones and oceans. Research and policy focused contributions addressing these interactions in aquatic ecosystems are welcome.
Conveners: Stephanie Hampton, National Center for Ecological Analysis and Synthesis, UC-Santa Barbara, email@example.com; Paul Hanson, Center for Limnology, University of Wisconsin, firstname.lastname@example.org; Emily Stanley, Center for Limnology, University of Wisconsin, email@example.com
Long-term limnological data sets are increasingly valued for the unique perspective they provide on the complex dynamics of organisms and ecosystems, particularly as they respond to both anthropogenic perturbations and climate phenomena. Recent studies provide powerful examples of the role of multi-decadal data sets in elucidating major ecological processes in lakes, from documenting surprising patterns of ecosystem response to shifting climate, to unraveling complex underlying mechanisms. Typically, these high-value long-term studies are based on lakes that have long histories of limnological research. However, long-term limnological data collection is far more extensive than is suggested by either the current state of the literature or the current availability of long-term limnological data in public repositories. Many government and citizen-based programs have produced a wealth of lake data that have received limited attention in both research and management arenas, and most long-term lake studies result from independent efforts without coordinated data sharing. In this session, we hope to emphasize the need for community effort to develop, share, and safe-guard these long-term data sets by highlighting examples of their use in revealing patterns of multi-scale temporal change in lakes, informing management decisions, and engaging the public in the science and stewardship of lakes.
Conveners: Tom Shatwell, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), firstname.lastname@example.org; Bertram Boehrer, Helmholtz Centre for Environmental Research – UFZ, email@example.com; Klaus Jöhnk, CSIRO Land and Water, Klaus.Joehnk@csiro.au
Poorly mixed lakes are characterized by vertical gradients in physical and chemical parameters like temperature, salinity, density, light, nutrients, oxygen, redox potential, or ionic composition. Biological gradients, like the distribution of plankton and fish, also form as a result. Strong gradients such as the thermocline in holomictic lakes or the chemocline in meromictic lakes can be hotspots of matter conversion, impose barriers to the movement of organisms, particles and dissolved substances, or establish ecological niches. The metalimnion and other internal transition zones are thus highly active regions but also semi-permeable barriers. While limnologists often reduce poorly mixed lakes into two or three separate layers of interest (e.g., surface water, deep water, and sediment), little attention is paid to such interfaces and transition zones. This session will therefore focus on the role of the metalimnion and other internal transition zones in the structure and function of the whole lake system. We invite contributions covering all aspects of physical, chemical and biological processes, where the emphasis lies on the interactions between processes or their effects and feedbacks on the wider lake ecosystem. Examples of interesting questions include: What role does a deep chlorophyll layer play in nutrient cycling and food web dynamics? What are the effects of internal waves on biological and chemical processes? How does a metalimnion or chemical transition zone mediate the transformation and vertical flow of matter and energy? Does a chemocline in a meromictic lake act solely as a trap? Just how big is the sampling error when mixed samples are only drawn from the epilimnion? We hope to achieve an improved understanding of how processes across internal boundaries like the metalimnion influence lakes as a whole, generate new research themes, and highlight new advances towards lake and reservoir management.
Conveners: Alan D. Christian, University of Massachusetts Boston, firstname.lastname@example.org; Robyn E. Hannigan, University of Massachusetts Boston, email@example.com; Alonso Ramirez, University of Puerto Rico-Rio Piedras, firstname.lastname@example.org; Alex Eisen-Cuadra, University of Massachusetts Boston, email@example.com; Helenmary Hotz, University of Massachusetts Boston, Helenmary.Hotz@umb.edu
Global change can be defined as planetary scale changes of the Earth’s system that includes large-scale changes in human society. Societies need to respond to these changes through the use of science and policy. Furthermore, global change is likely to have impact on national security as these changes influence the distribution and abundance of resources. This session will focus on the effects of global change on stream and lake watersheds in the Caribbean and other climate-sensitive regions in terms of science and food and resource security, and how policy (including education/outreach) are being developed in response to global change.
River basins connect the land to the coastal ocean. They integrate and process signals in their drainage basins and transmit processed signals to the coast. This session invites contributions that advance our understanding of land-derived signals transmitted to the coastal ocean. We especially invite contributions dealing with dynamic features of all scales from a variety of subdisciplines (hydrology, landscale evolution, tectonics, ecology, biogeochemistry) in river basins that are triggered by natural or anthropogenic forcings. Contributions focusing on processes in estuaries and the coast should be presented in companion session #27, whereas contributions dealing with cycling of organic matter should be submitted to companion session # 45.
Conveners: Daniel Nover, AAAS Sci. and Tech. Policy Fellow/EPA Global Change Research Program, firstname.lastname@example.org; S. Geoffrey Schladow, UC Davis - Tahoe Environmental Research Center, email@example.com; Christopher Clark, EPA Global Change Research Program, firstname.lastname@example.org; Craig Williamson, Miami University - Global Change Limnology Laboratory, email@example.com
The impact of climate change on air temperature and watershed hydrology is increasingly well documented. These impacts will have dramatic implications for lakes and reservoirs in terms of ecosystem health, ecosystem services, biodiversity, human health, and water supply. Increasing air temperature will lead to increasing surface water temperature and increasing density stratification which will lead to numerous impacts on water quality, aquatic habitat, and water supply. Changes to hydrology are less well understood and likely to vary regionally. However, such changes will similarly lead to shifts in lake/reservoir water quality. This symposium will bring together resource managers, academics and other stakeholders to 1) explore the scientific evidence for climate change impacts on lakes and reservoirs, 2) identify key regional vulnerabilities of lakes and reservoirs, and 3) explore available adaptation strategies for managing lakes and reservoirs under climate change. The objective of the symposium will be to bring together the major stakeholders in the field to develop a broader understanding of these issues and initiate a nationwide assessment of lake/reservoir vulnerability to climate change.
Conveners: Katherine McMahon, University of Wisconsin Madison, USA, firstname.lastname@example.org; Stefan Bertilsson, Uppsala University, Sweden, email@example.com; Hans-Peter Grossart, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, IGB-Berlin, firstname.lastname@example.org
Freshwater microbial communities are highly dynamic, with drivers of change operating at multiple time scales ranging from minutes to years. Regular and consistent sampling of communities and rich contextual environmental data across these time scales is necessary in order to develop a deep and predictive understanding of how communities assemble and perform key ecosystem functions. This session will feature research that embraces the use of time series and high-resolution spatial sampling to study freshwater microbial communities with a variety of techniques including next- generation sequencing-enabled tag sequencing, metagenomics, fluorescent in situ hybridization, automated samplers, and high-frequency in situ sensor monitoring. The potential for near-real-time monitoring of harmful cyanobacterial blooms to enable now-casting water quality models and early warning systems for public health authorities will be emphasized. A recent new joint initiative launched by the Earth Microbiome Project (http://www.earthmicrobiome.org/) and the Global Lakes Ecological Observatory Network (GLEON) (http://www.gleon.org/) will be highlighted.