Alan Covich | The University of Georgia (original) (raw)

Papers by Alan Covich

Hydrobiologia, Mar 25, 2024

Journal of Hydrology, Dec 1, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

River Research and Applications, Sep 12, 2017

In the southeastern United States and globally, increasing human water demand coupled with climat... more In the southeastern United States and globally, increasing human water demand coupled with climate change is diminishing stream flows and increasing stream intermittency in many watersheds. We characterized benthic invertebrate assemblages across a stream flow gradient ranging from intermittent to perennial following a multiyear drought by examining the functional traits that can influence assemblage response to drying. We sampled 13 reaches within the Lower Flint River Basin in southwestern Georgia, from September to December 2013. Reaches included perennial, near-perennial (ceased flowing but maintained a wetted channel during drought), intermittent-dry (seasonally dry), and intermittent-frequent (frequently dry). Distinct assemblages were documented across this gradient. Reaches that dried during the drought had a lower richness of aquatic insects, especially Ephemeroptera, Plecoptera, and Trichoptera taxa, partly due to inadequate time for life cycle completion and lack of adaptations to avoid drying. Intermittent reaches also included abundant and unique noninsect taxa such as Gammarus spp. and Isopoda. Projected trends towards increased water demand and drought severity and frequency in the southeastern United States will magnify shifts towards dominance by drought-tolerant taxa as greater portions of stream networks become intermittent.

American Malacological Bulletin, Dec 28, 1987

Bulletin of the Ecological Society of America, Oct 1, 2013

The complex, interconnected structure and function of ecological systems is apparent in their cou... more The complex, interconnected structure and function of ecological systems is apparent in their countless direct and indirect pathways of energy (e.g., a food web), mass (e.g., a movement corridor), and information (e.g., a social network). This Ignite ESA Session united multiple fields of ecology through the lens of a single, rapidly evolving, analytical framework: network analysis. This session examined basic and applied ecological problems in both naturally formed and anthropogenically altered networks of interactions. In particular, diverse examples were presented from disease transmission, social behavior, mutualistic interactions, and species migration. The five-minute, Ignite ESA format provided a fitting outlet for rapid presentation of methods, and opened lines of communication between somewhat disparate fields of study.

United Nations Conference on Trade and Development, Geneva, 1989

Lake and Reservoir Management, 2018

Changes in submerged aquatic vegetation (SAV) coverage caused by extended drought and flood pulse... more Changes in submerged aquatic vegetation (SAV) coverage caused by extended drought and flood pulses. Lake Reserv Manage. 34:000-000. Previous studies demonstrated that submerged aquatic vegetation (SAV) affects productivity and biogeochemical cycling within freshwater ecosystems. Some invasive submerged macrophytes dominate shallow water bodies and are known to compete for nutrients with native macrophytes and phytoplankton. To evaluate variation in SAV coverage, annual whole-reservoir vegetation surveys were conducted during the peak of the growing season over a 3-yr period that included drought and years with seasonal flood pulses. Physical parameters were directly measured (Photosynthetically Active Radiation: PAR) or obtained from USGS river gauges (river discharge and turbidity) to investigate the relationship between hydrology and SAV coverage. Precipitation was lower in the first year of the study compared to the following 2 yr causing the lowest river discharge observed over the 3-yr study. First-year discharge was also lower than the 50-yr median daily Q (discharge). SAV coverage, particularly of dioecious Hydrilla verticillata, was the greatest during the reduced flow period (35.5 km 2). With increasing precipitation and river discharge, SAV coverage was reduced during subsequent years (22.9 km 2 and 18.3 km 2 , respectively). Increased discharge caused turbidity to increase, which reduced light availability during the early growing season, causing a delay in germination and subsequent reduction in SAV coverage. In shallow reservoirs, SAV is capable of extensive coverage. Thus, large variation in coverage can alter ecosystem functionality. In regulated river systems, managing late spring flood pulses may provide some control of SAV coverage in shallow reservoirs, in addition to providing other environmental flow benefits.

Hydrobiologia, 2018

Lakes and reservoirs are important sites for biogeochemical cycling on both regional and global s... more Lakes and reservoirs are important sites for biogeochemical cycling on both regional and global scales. Shallow lakes often have higher coverage of submerged aquatic vegetation (SAV) because of increased light penetration to the sediment as well as stronger interactions between the sediment and the water column. These biotic and abiotic interactions can strongly affect nutrient cycling. This study evaluated how hydrologically driven changes in SAV coverage affected nutrient processing within a relatively shallow reservoir. To assess these effects, a comprehensive water quality sampling network was established that quantified nutrient concentrations in the inflows and outflow of the lake. Annual vegetation surveys quantified the spatial coverage of SAV. Annual inflow was significantly lower in the first year of the study compared to the following 2 years. Consequently, SAV coverage was also highest during the lowest flows in the first year and was lower in the following 2 years when flows were greater. NO 3-N concentrations were also lowest within Hydrilla beds and in the outflow during the growing season of the first year. Our results suggest that hydrological variation was the main driving variable of SAV coverage, and that the extent of SAV coverage strongly controlled nutrient processing at the whole-reservoir scale.

The Southwestern Naturalist, 1982

This report represents the combined efforts of several faculty at Colorado State University from ... more This report represents the combined efforts of several faculty at Colorado State University from a wide range of academic backgrounds-from fishery and wildlife biology to hydrology, engineering, and sociology. We met to discuss our own individual opinions and perspectives on "ecological integrity. " We also discussed these issues with off-campus groups and individuals to gain their insight with aspects of water law, usage in various contexts, and frustrations with current regulations. We found that we shared a number of concerns regarding the importance of increased coordination and communication regarding sustainable resource development.

Elsevier eBooks, 2013

Energy flows in ecosystems relate biodiversity to recycling of essential nutrients. Ecosystems ar... more Energy flows in ecosystems relate biodiversity to recycling of essential nutrients. Ecosystems are thermodynamically open, hierarchically organized communities of producers, consumers, and decomposers together with the abiotic factors that influence species interactions. Connections among species in food webs typically result in feedback loops and recycling of nutrients and materials within the conceptually defined ecosystem boundaries.

The Korean Journal of Ecology, 2000

Different phenological patterns of leaf and fruit fall among native and non-native riparian speci... more Different phenological patterns of leaf and fruit fall among native and non-native riparian species provide a spatially and temporally heterogeneous series of alternative food resources for detritivores. Relatively little is known about qualitative differences among these different riparian species. Rates of litter inputs, decomposition, and retention for different sources of riparian litter require long-term documentation. Species of freshwater shrimps, crabs. insects. and gastropods are known to consume a wide range of litter inputs but how these dynamic food webs function under changing climatic and land-use conditions is unknown, especially in tropical streams. On-going studies in the Luquillo Experimental Forest. Puerto Rico provide an example of how inputs of fronds and fruits from palms (Prestoea montana) serve as important foods and microhabitat for species of freshwater crabs and shrimp. Native riparian species such as Prestoea montana are commonly distributed in the Luquillo Mountains especially along steep slopes and stream banks. After tropical storms with high winds, the large fronds from these native riparian trees provide important inputs of leaf litter to the stream food web. In some streams, the input of ripe fruit from non-native trees such as Java plum (Syzigium jambos) also provides a major source of detrital food resources, especially during periods when fruit fall from native species of palms may be limited.