Freshwater Ecosystems Revitalizing Educational Programs in Limnology (1996) / Chapter Skim
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Fundamental Research Questions in Inland Aquatic Ecosystem Science
Fundamental Research Questions in Inland Aquatic Ecosystem Science
Pages 257-278
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From page 257... ...
O'Melia Department of Geography and Environmental Engineering The Johns Hopkins University Baltimore, Maryland SUMMARY This background paper presents one possible set of fundamental questions for inland aquatic ecosystems. There are other questions that may be more fundamental or more pressing for meeting the needs of society in managing water resources.
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From page 258... ...
INLAND AQUATIC ECOSYSTEMS For the purposes of providing a background for this study, we have chosen to pose questions at a level relevant to the full range of inland aquatic ecosystems (lakes, wetlands, streams, big rivers, ponds, etch. An ecosystem is defined by its boundaries, and an inland aquatic ecosystem can range in size from a small transient desert pool that forms after a storm to the watershed of the Colorado River.
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From page 259... ...
Saline lakes are closed-basin lakes, with high concentrations of dissolved solids. Prairie wetlands and intermittent streams are distinguished because the climatic sensitivity of their hydrologic regimes can cause TABLE 1 Occurrence of Various Classes of Inland Waters in Regions of North America Region Classification 1 2 3 4 5 6 7 8 Streams/rivers Blackwater rivers - X - Alpine streams X X - - X Intermittent streams - X X X X Perennial streams X X X X X X X X Lakes Large lakes X X X X X Saline lakes X X X X X Small lakes/ponds X X X X X X X X Reservoirs X X X X X X X Wetlands Large riparian wetlands X X X X X X X Large swamps - X Prarie wetlands X X Small bogs/fens X X X X X X Large peatlands X X Coastal zone areas X X X X X X NOTE: Numbers correspond to the following regions: 1 Laurentian Great Lakes and Precambrian Shield of the United States and Canada.
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From page 260... ...
Despite its simplicity, this classification illustrates the similarities and differences in the occurrence of inland aquatic ecosystems at the regional scale for the North American continent. Three types of inland waters are commonly found throughout the continent: (1)
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From page 261... ...
, (2) aquatic organisms occurring in inland aquatic ecosystems (the ecological significance of the species)
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From page 262... ...
Complex systems can respond to change in unexpected ways, and deciphering the complexity is the major task ahead. Question: Is a climatic signal local to one particular lake, or does it operate over a regional scale?
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From page 263... ...
Because of decreased light intensities associated with snow and ice cover, the ratio of primary production to heterotrophic degradation undoubtedly decreases greatly in many aquatic ecosystems in the transition from fall to winter. In temperate streams, for example, the extent of heterotrophic degradation during winter of fallen leaves and other (nonliving)
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From page 264... ...
Processes controlling the chemical speciation of biologically reactive constituents are also driven by sunlight or by changes in pH and oxygen concentration associated with photosynthesis. For example, photoreduction of particulate iron and manganese oxides in the water column or in the streambed can release sorbed phosphate, which is then assimilated by algae.
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From page 265... ...
Question: How can we cZeveZop an understanding of inland aquatic ecosystems at regional scales? Most current ecological studies are conducted at local to watershed scales.
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From page 266... ...
Interactions occurring at the mesoscale include benthic invertebrates and predatory invertebrates or fish, and ecosystem responses to episodic disturbances such as floods and fires. To develop useful concepts describing the structure and functioning of aquatic systems, it is necessary to identify fundamental units (such as the streambed)
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From page 267... ...
Although questions may be posed at the level of trophic interactions, in order to examine these interactions in detail in any particular aquatic ecosystem, the questions become focused on which species is doing what, how fast, and when? Question: How do characteristics and habitat requirements of individual species fit together to control ecosystem-scale processes, such as productivity and resilience?
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From page 268... ...
The significance of interannual shifts in algal species, whether within a lake or stream ecosystem, or the presence of particular rare species, may be more difficult to interpret. Question: Is understanding of important microbial processes in aquatic ecosystems (the microbial loop, heterotrophic degradation of natural organic material or organic contaminants)
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From page 269... ...
Questions related to genetic characteristics may seem esoteric at first, but they have important consequences for water quality issues. The following examples involving phytoplankton illustrate this point.
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From page 270... ...
Natural Water A Chemical World "Water quality" is a phrase used commonly in discussing water resources, but the meaning of water quality can be a source of confusion. Quality has many meanings, the principal ones being "peculiar and essential character" and "degree of excellence." The first refers to objective features of water; the second, to value judgments about the water for particular human uses (Averett and Marzolf, 1987~.
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From page 271... ...
A fundamental research question that would lead to better water quality standards for contaminants in the future involves the mechanism of contaminant uptake and biological magnification by organisms. For many important hydrophobic contaminants, for example, a simple hydrophobic partitioning model does not adequately explain uptake.
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From page 272... ...
typically is used in a nominal sense for organic matter passing through a 0.4-~m filter and includes colloidal and truly dissolved forms. Question: How does the chemical composition of this abundant detrital organic material influence heterotrophic degradation and, in turn, the nature of the ecosystem ?
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From page 273... ...
, and many metals during transport through the vegetation canopy, across soil surfaces, through the highly reactive surficial zone of soils, and downward into aquifers is a challenging research area of environmental concern that requires an integration of chemical and hydrologic concepts and field measurements. A Changing Climate Question: What is the relative importance of direct physical changes compared to indirect biogeochemical changes in determining responses to changing climate?
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From page 274... ...
Humans: A Keystone Species Humans play a significant role in all aquatic systems. They alter the physical, chemical, and biological structure and function of aquatic systems through direct interactions (e.g., harvesting fish, discharging chemicals, thermal discharges from industry)
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What is needed is a coherent, integrated theory that fundamentally links human and aquatic systems, and this theory must be a fundamental component of future aquatic research. Questions: What ecological and human metrics are important in quantifying on defining the keystone species role in aquatic systems?
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From page 276... ...
A simple example of a remediation effort for an acid mine drainage stream in the Rocky Mountains illustrates how the questions identified above are relevant to addressing important water resource and environmental issues. In the 1800s and early part of this century, there was a mining boom in the Rocky Mountains, and this boom spurred the development of the western states.
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From page 277... ...
Questions related to the occurrence of particular species are also relevant. Should the success of the treatment be evaluated in terms of the return of ecosystem function, as measured by rates of primary production by periphyton, or should success be based on the return to the remediated stream of species of algae, benthic invertebrates, and fish normally found in pristine streams in the region?
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From page 278... ...
Ann Arbor, Mich.: Ann Arbor Science Publishers. Novotcy, V., and G
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