Geology topics

G. Coppola

Publications and source records attributed to G. Coppola.

5 recordsLinked to original sources

USGS2021

Retention and dimensional changes of evergreen brush piles within a flood control reservoir

Brush piles (i.e., trees and large woody debris) are often installed in reservoirs to supplement fish habitat. The retention and dimensional change of brush piles after installation is important information that can be used to maximize the effectiveness of this management action. We evaluated the retention and dimensional change of 70 eastern red cedar Juniperus virginiana and bald cypress Taxodium distichum brush piles in an embayment of a drawdown reservoir up to four annual cycles of submergence and exposure. We used satellite imagery to supplement our onsite measurements of retention. We also examined spatial patterns of brush pile retention and dimensional change. Brush piles were lost at 10% per year, and their volume was lost at 14% per year. We compared our rates of brush pile retention and dimensional change with those from a holdout data set of 50 brush piles. Estimates between data sets did not differ statistically. Spatial patterns of retention and dimensional change coincided with morphological features in our study area, suggesting that retention and dimensional change is influenced by variable physical forces (e.g., wave action and flow) at installation locations. Our estimates of brush pile retention and dimensional change can be used to generally sustain desirable brush densities. For example, to maintain a fixed total volume of brush in our study embayment, roughly 23% of the total brush volume installed would need to be replaced annually. Similar research in reservoirs managed for other purposes is needed, as length and cycle of inundation could lead to variable rates of retention and dimensional change. Additionally, advancements into computer-assisted detection and volume estimation could reduce the time and effort needed to monitor brush piles.

Mississippi↗

USGS2021

Selection of habitat-enhancing plants depends on predator-prey interactions

Shallow areas of drawdown reservoirs are often devoid of adequate fish habitat due to degradation associated with unnatural and relatively invariable cycles of exposure and flooding. One method of enhancing fish habitat in these areas is to sow exposed shorelines with agricultural plants to provide structure once flooded. It remains unclear if some plants may be more suitable than others to provide effective fish habitat. To determine the fish habitat potential of various crops, we performed a replicated tank experiment evaluating the selection of agricultural plants by prey and predator fishes with and without the presence of the other. We submerged diverse treatments of potted plants in outdoor mesocosms stocked with prey and/or predator fish and monitored selection of plant species, stem density, and stem height over 0.5-h trials. Prey fish selected the densest vegetation, and selection was accentuated when a predator was present. Predators selected the second highest stem density and were more active when prey were present. Prey schooling was increased by predation risk, suggesting that cover was insufficient to outweigh the advantages of increased group size. Our data indicate that the perception of cover quality is reciprocally context dependent on predator–prey interactions for both predator and prey. Applications of the two most selected plant treatments in this study could enhance structural habitat for both predator and prey fishes in reservoirs, adding to their already reliable functionality as supplemental forage crops for terrestrial wildlife.

Journal of Fish and Wildlife Management↗

USGS2020

Reservoir fish habitats: A perspective on coping with climate change

Climate change is the defining environmental problem for our generation. The effects of climate change are increasingly evident and are anticipated to profoundly affect our ability to conserve fish habitats and fish assemblages. Reservoirs are important structures for coping with projected shifts in water supply, but they also provide refuge for riverine fishes and retain distinct fish assemblages that support diverse fisheries. The effects of climate change on reservoirs are unique among aquatic systems because reservoirs have distinctive habitat characteristics due to their terrestrial origin and strong linkage to catchments. This article reviews (1) the projected effects of rising temperature and shifting precipitation on reservoir fish habitats, and (2) adaptation strategies to cope with the anticipated effects. Climate warming impacts to reservoirs may include higher water temperatures and shifts in hydrology that can result in reduced water levels in summer and fall, altered water residence cycles, disconnection from upstream riverine habitats and backwaters, increased stratification, eutrophication, anoxia, and a general shift in biotic assemblages including plants, invertebrates, and fishes. What is needed to adapt to these changes is a perspective that focuses on maintaining ecosystem functionality rather than on retaining a certain species composition. To that end, various strategies organized into planning, monitoring, and managing compartments are identified.

Reviews in Fisheries Science & Aquaculture↗

USGS2020

Assessing establishment and growth of agricultural plantings on reservoir mudflats

Winter drawdowns in flood control reservoirs create expansive mudflats that lack the vegetation typical of littoral zones, which reduces the amount of structure available for fish habitat. This study investigated the feasibility of establishing agricultural plantings as a management action to ameliorate mudflats by providing structural cover following reservoir refilling. We tested cool-season annual grasses and clovers applied in several mixed and monoculture treatments that were sown on the mudflats of Enid Reservoir, Mississippi, during the winter drawdown in three consecutive years. Soil samples were taken for analysis of pH and macronutrients prior to planting. Plantings were monitored until the following spring to evaluate effectiveness of establishment through ground coverage, height, and stem density sampling. Plots were assigned a seeding treatment of either grasses (ryegrass Lolium spp. or triticale x Triticosecale sp.), clovers (balansa clover Trifolium michelianum or berseem clover Trifolium alexandrinum ), or both (mixed plantings) or left as an unseeded control. Differences among plant treatments were assessed via repeated measures analysis of variance and differences among means evaluated with Tukey's honestly significant difference test. Soil productivity within the study area was poor all 3 years. Grasses germinated both when disked into the soil and when top sown, while clover only germinated when disked. Plots seeded with grasses performed better than control plots with respect to stem density, height, and ground coverage, while plots seeded with grass and clover mixtures performed better than control plots only with respect to height, and plots seeded with only clover did not perform significantly better than control plots. Results serve as an evaluation of the efficacy of agricultural plant establishment on the mudflats of a flood control reservoir, inform the direction of future research, and identify considerations regarding the application of agricultural plantings as a management tool to create fish habitat.

Mississippi↗

USGS2019

Fish assemblages in a Mississippi reservoir mudflat with low structural complexity

In shallow reservoirs, seasonal water drawdowns expose littoral areas and over time produce barren mudflats. When flooded, mudflats provide homogeneous substrates, turbid water, and eroding shorelines of limited ecological value. We hypothesized that in mudflats structurally complex habitats are occupied by more fish, smaller fish of a larger range in sizes, more species, and fish assemblages that are different from those in simpler habitats. We tested these hypotheses over two consecutive years with fish collections made in sites with varying structural complexity. Results indicated that structural complexity harbors more fish in transects and enclosures. Structural complexity did not influence median length, but length range increased with structural complexity. Average species richness increased with structural complexity. Fish assemblage composition changed as structural complexity increased. The ability of cover to provide survival, growth, and carrying capacity benefits is fundamental to programs aimed at increasing structural complexity. Results suggest observed effects on fish assemblages can lead to such benefits. Considering mudflats are a major component of reservoirs, expand as reservoirs age, and there is a potential to exert meaningful change on fish assemblages of impounded rivers by managing mudflats, we suggest additional attention is needed to develop practical habitat restoration options.

Mississippi↗