共查询到4条相似文献,搜索用时 0 毫秒
1.
Lake Okeechobee (surface area = 1830 km2, mean depth = 3.5 m), the largest lake in Florida, is eutrophic and has nitrogen and phosphorus loading rates in excess of nearly all established criteria. The lake is not homogeneous regarding trophic conditions, and spatial and temporal variations occur regarding nutrient limitation. Nonetheless, phosphorus loading rate and trophic state data fit reasonably well to various input-output models developed for temperate lakes. Modification of the models by regression analysis to fit data for Florida lakes resulted in improved predictions for most parameters. Analysis of nutrient management alternatives for the lake indicates that a 75% reduction of phosphorus loading from the largest source (the Taylor Creek-Nubbins Slough watershed) would reduce the average chlorophyll a concentration by less than 20%. Complete elimination of inputs from the largest nitrogen source (the Everglades Agricultural Area) would decrease the average nitrogen concentration in the lake by about 20%. Limitations of nutrient inputoutput models regarding analysis of trophic conditions and management alternatives for the lake are discussed. 相似文献
2.
Phosphorus Loadings Associated with a Park Tourist Attraction: Limnological Consequences of Feeding the Fish 总被引:1,自引:0,他引:1
The Linesville spillway of Pymatuning State Park is one of the most visited tourist attractions in Pennsylvania, USA, averaging
more than 450,000 visitors · year−1. Carp (Cyprinus carpio Linnaeus) and waterfowl congregate at the spillway where they are fed bread and other foods by park visitors. We hypothesized
that the “breadthrowers” constitute a significant nutrient vector to the upper portion of Pymatuning Reservoir. In the summer
of 2002, we estimated phosphorus loadings attributable to breadthrowers, and compared these values to background loadings
from Linesville Creek, a major tributary to the upper reservoir. Items fed to fish included bread, donuts, bagels, canned
corn, popcorn, corn chips, hot dogs, birthday cakes, and dog food. Phosphorus loading associated with park visitors feeding
fish was estimated to be 3233 g day−1, and estimated P export from the Linesville Creek watershed was 2235 g·day−1. P loading attributable to breadthrowers exceeded that of the entire Linesville Creek watershed on 33 of the 35 days of study,
with only a heavy rainfall event triggering watershed exports that exceeded spillway contributions. Averaged across 5 weeks,
breadthrowers contributed 1.45-fold more P to Pymatuning Reservoir than the Linesville Creek watershed. If Linesville Creek
P exports are extrapolated to the entire Sanctuary Lake watershed, spillway contributions of P added 48% to the non-point
source watershed P entering the lake. Park visitors feeding fish at the Linesville Spillway are a significant source of nutrients
entering Sanctuary Lake. 相似文献
3.
Assessing the Effects of Nutrient Management in an Estuary Experiencing Climatic Change: The Neuse River Estuary, North Carolina 总被引:1,自引:0,他引:1
Eutrophication is a serious water quality problem in estuaries receiving increasing anthropogenic nutrient loads. Managers
undertaking nutrient-reduction strategies aimed at controlling estuarine eutrophication are faced with the challenge that
upstream freshwater segments often are phosphorus (P)-limited, whereas more saline downstream segments are nitrogen (N)-limited.
Management also must consider climatic (hydrologic) variability, which affects nutrient delivery and processing. The interactive
effects of selective nutrient input reductions and climatic perturbations were examined in the Neuse River Estuary (NRE),
North Carolina, a shallow estuary with more than a 30-year history of accelerated nutrient loading and water quality decline.
The NRE also has experienced a recent increase in Atlantic hurricanes and record flooding, which has affected hydrology and
nutrient loadings. The authors examined the water quality consequences of selective nutrient (P but not N) reductions in the
1980s, followed by N reductions in the 1990s and an increase in hurricane frequency since the mid-1990s. Selective P reductions
decreased upstream phytoplankton blooms, but increased downstream phytoplankton biomass. Storms modified these trends. In
particular, upstream annual N and P concentrations have decreased during the elevated hurricane period. Increased flushing
and scouring from storms and flooding appear to have enhanced nutrient retention capabilities of the NRE watershed. From a
management perspective, one cannot rely on largely unpredictable changes in storm frequency and intensity to negate anthropogenic
nutrient enrichment and eutrophication. To control eutrophication along the hydrologically variable freshwater–marine continuum,
N and P reductions should be applied adaptively to reflect point-source–dominated drought and non–point-source–dominated flood
conditions. 相似文献
4.
Coastal waters have been significantly influenced by increased inputs of nutrients that have accompanied population growth
in adjacent drainage basins. In Tampa Bay, Florida, USA, the population has quadrupled since 1950. By the late 1970s, eutrophic
conditions including phytoplankton and macroalgal blooms and seagrass losses were evident. The focus of improving Tampa Bay
is centered on obtaining sufficient water quality necessary for restoring seagrass habitat, estimated to have been 16,400
ha in 1950 but reduced to 8800 ha by 1982. To address these problems, targets for nutrient load reductions along with seagrass
restoration goals were developed and actions were implemented to reach adopted targets. Empirical regression models were developed
to determine relationships between chlorophyll a concentrations and light attenuation adequate for sustainable seagrass growth. Additional empirical relationships between
nitrogen loading and chlorophyll a concentrations were developed to determine how Tampa Bay responds to changes in loads. Data show that when nitrogen load
reduction and chlorophyll a targets are met, seagrass cover increases. After nitrogen load reductions and maintenance of chlorophyll a at target levels, seagrass acreage has increased 25% since 1982, although more than 5000 ha of seagrass still require recovery.
The cooperation of scientists, managers, and decision makers participating in the Tampa Bay Estuary Program’s Nitrogen Management
Strategy allows the Tampa Bay estuary to continue to show progress towards reversing many of the problems that once plagued
its waters. These results also highlight the importance of a multi-entity watershed management process in maintaining progress
towards science-based natural resource goals. 相似文献