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Climate-change driven increases in water temperature pose challenges for aquatic organisms. Predictions of impacts typically do not account for fine-grained spatiotemporal thermal patterns in rivers. Patches of cooler water could serve as refuges for anadromous species like salmon that migrate during summer. We used high-resolution remotely sensed water temperature data to characterize summer thermal heterogeneity patterns for 11,308 km of second–seventh-order rivers throughout the Pacific Northwest and northern California (USA). We evaluated (1) water temperature patterns at different spatial resolutions, (2) the frequency, size, and spacing of cool thermal patches suitable for Pacific salmon (i.e., contiguous...
Categories: Publication; Types: Citation; Tags: Aquatic Sciences
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Habitat fragmentation impedes dispersal of aquatic fauna, and barrier removal is increasingly used to increase stream network connectivity and facilitate fish dispersal. Improved understanding of fish community response to barrier removal is needed, especially in fragmented agricultural streams where numerous antiquated dams are likely destined for removal. We examined post-removal responses in two distinct fish communities formerly separated by a small aging mill dam. The dam was removed midway through the 6 year study, enabling passage for downstream fishes affiliated with a connected reservoir into previously inaccessible habitat, thus creating the potential for taxonomic homogenization between upstream and downstream...
Categories: Publication; Types: Citation; Tags: Aquatic Sciences
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Drought and summer drying can be important disturbance events in many small streams leading to intermittent or isolated habitats. We examined what habitats act as refuges for fishes during summer drying, hypothesizing that pools would act as refuge habitats. We predicted that during drying fish would show directional movement into pools from riffle habitats, survival rates would be greater in pools than in riffles, and fish abundance would increase in pool habitats. We examined movement, survival and abundance of three minnow species, bigeye shiner (Notropis boops), highland stoneroller (Campostoma spadiceum) and creek chub (Semotilus atromaculatus), during seasonal stream drying in an Ozark stream using a closed...
Categories: Publication; Types: Citation; Tags: Aquatic Sciences
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The biogeochemical cycle of mercury will be influenced by climate change, particularly at higher latitudes. Investigations of historical mercury accumulation in lake sediments inform future predictions as to how climate change might affect mercury biogeochemistry; however, in regions with a paucity of data, such as the thermokarst-rich Arctic Coastal Plain of Alaska (ACP), the trajectory of mercury accumulation in lake sediments is particularly uncertain. Sediment cores from three thermokarst lakes on the ACP were analyzed to understand changes in, and drivers of, Hg accumulation over the past ~ 100 years. Mercury accumulation in two of the three lakes was variable and high over the past century (91.96 and 78.6...
Categories: Publication; Types: Citation; Tags: Aquatic Sciences
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Drought and summer drying can be important disturbance events in many small streams leading to intermittent or isolated habitats. We examined what habitats act as refuges for fishes during summer drying, hypothesizing that pools would act as refuge habitats. We predicted that during drying fish would show directional movement into pools from riffle habitats, survival rates would be greater in pools than in riffles, and fish abundance would increase in pool habitats. We examined movement, survival and abundance of three minnow species, bigeye shiner (Notropis boops), highland stoneroller (Campostoma spadiceum) and creek chub (Semotilus atromaculatus), during seasonal stream drying in an Ozark stream using a closed...
Categories: Publication; Types: Citation; Tags: Aquatic Sciences
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Impoundments alter connectivity, sediment transport and water discharge in rivers and floodplains, affecting recruitment, habitat and resource availability for fish including benthic invertivorous fish, which represent an important link between primary producers and higher trophic levels in tropical aquatic ecosystems. We investigated long-term changes to water regime, water quality, and invertivorous fish assemblages pre and post impoundment in three rivers downstream of Porto Primavera Reservoir in south Brazil: Paraná, Baía and Ivinhema rivers. Impacts were distinct in the Paraná River, which is fully obstructed by the dam, less evident in the Baía River which is partially obstructed by the dam, but absent in...
Categories: Publication; Types: Citation; Tags: Aquatic Sciences
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Selenium is an essential micronutrient for the growth of the dinoflagellate Peridinium gatunense that dominates the spring algal bloom in Lake Kinneret (LK). The relationship between the levels of dissolved selenium species and the occurance of algal blooms in this lake was studied. During algal blooms of P. gatunense in spring and of the blue-green Aphanizomenon ovalisporum in fall (in 1994) the concentration of epilimnetic dissolved organic Se (Se(org)) increased whereas that of selenite (SeIV) decreased, to levels below the limit of detection: 5 ng/l. The disappearance of SeIV during these blooms is attributed to algal uptake and it is suggested that the growth of both algae may have depended on Se(org) regeneration....
Categories: Publication; Types: Citation; Tags: Aquatic Sciences
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We investigated functional responses of benthic invertebrates to deposited sediment in four Missouri USA streams. In each stream, invertebrates were sampled along continuums of deposited sediment (particles <2 mm in size) from 0 to 100% surface cover in reaches of fairly homogeneous substrate composition, current velocity, and water depths. Correlations, graphical representations, and the cumulative response curves of feeding and habit groups provided strong empirical support for distinct community functional changes due to deposited sediment. Feeding groups were more sensitive to deposited sediment than habit groups. Densities of all the feeding groups decreased significantly with increasing deposited sediment,...
Categories: Publication; Types: Citation; Tags: Aquatic Sciences
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Tissue residues of total mercury (Hg), total polychlorinated biphenyls (PCBs), and lipid-based PCBs; plasma concentrations of endocrine biomarkers; and reproductive and histologic biomarkers were assessed in 460 carp (Cyprinus carpio), bass (Micropterus salmoides and Micropterus dolomieui), and bullhead (Ameiurus nebulosus) collected from eight sites across the Hudson River Basin in the spring of 1998 to determine if endocrine disruption was evident in resident fish species and to evaluate contaminant-biomarker interrelations. Total PCBs in bed sediments (maximum 2,500 ??g kg-1) could explain 64 to 90% of the variability in lipid-based PCB residues in tissues (maximum 1,250 ??g PCB g-lipid-1) of the four species....
Categories: Publication; Types: Citation; Tags: Aquatic Sciences
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Freshwater littoral zones harbor diverse ecological communities and serve numerous ecosystem functions that are controlled, in part, by natural water level fluctuations. However, human alteration of lake hydrologic regimes beyond natural fluctuations threaten littoral zone ecological integrity. One type of hydrologic alteration in lakes is winter water level drawdowns, which are frequently employed for hydropower, flood control, and macrophyte control, among other purposes. Here, we synthesize the abiotic and biotic responses to annual and novel winter water level drawdowns in littoral zones of lakes and reservoirs. The dewatering, freezing, and increased erosion of exposed lakebeds drive changes in the littoral...
Categories: Publication; Types: Citation; Tags: Aquatic Sciences
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Inferences about ecological structure and function are often made using elemental or macromolecular tracers of food web structure. For example, inferences about food chain length are often made using stable isotope ratios of top predators and consumer food sources are often inferred from both stable isotopes and fatty acid (FA) content in consumer tissues. The use of FAs as tracers implies some degree of macromolecular conservation across trophic interactions, but many FAs are subject to physiological alteration and animals may produce those FAs from precursors in response to food deficiencies. We measured 41 individual FAs and several aggregate FA metrics in two filter-feeding taxa to (1) assess ecological variation...
Categories: Publication; Types: Citation; Tags: Aquatic Sciences
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We explored the underlying patterns of temporal stream CO2 partial pressure (pCO2) variability using highfrequency sensors in seven disparate headwater streams distributed across the northern hemisphere. We also compared this dataset of [40,000 pCO2 records with other published records from lotic systems. Individual stream sites exhibited relatively distinct pCO2 patterns over time with few consistent traits across sites. Some sites showed strong diel variability, some exhibited increasing pCO2 with increasing discharge, whereas other streams had reduced pCO2 with increasing discharge or no clear response to changes in flow. The only ‘‘universal’’ signature observed in headwater streams was a late summer pCO2 maxima...
Categories: Publication; Types: Citation; Tags: Aquatic Sciences
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Depth reduction is a natural process in floodplain lakes, but in many basins has been accelerated by anthropogenic disturbances. A diverse set of 42 floodplain lakes in the Yazoo River Basin (Mississippi, USA) was examined to test the hypothesis of whether depth reduction was a key determinant of water quality and fish assemblage structure. Single and multiple variable analyses were applied to 10 commonly monitored water variables and 54 fish species. Results showed strong associations between depth and water characteristics, and between depth and fish assemblages. Deep lakes provided less variable environments, clearer water, and a wider range of microhabitats than shallow lakes. The greater environmental stability...
Categories: Publication; Types: Citation; Tags: Aquatic Sciences