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At least 145 records · Page 8Linked to original sources
USGS2018

Groundwater contributions to excessive algal growth in the East Fork Carson River, Carson Valley, west-central Nevada, 2010 and 2012

Excessive algal growth and low dissolved oxygen concentrations were observed during low streamflow conditions during summer months along a 5,800-foot reach of the East Fork Carson River in Carson Valley, west-central Nevada. Algal growth from nutrient enrichment of a stream reduces aquatic diversity, threatens fish ecology and stream health, and can be a recreational nuisance. In response to concerns that groundwater discharging to the 5,800-foot reach of the East Fork Carson River may be a source of nutrients to the stream, the U.S. Geological Survey, in cooperation with the Carson Water Subconservancy District and the Nevada Division of Environmental Protection, conducted studies during the summers of 2010 and 2012 to gain an improved understanding of the contributions of nutrients to the stream from groundwater, characterize algal conditions and algal effects on water quality, assess potential sources of nitrate in groundwater discharging to the stream, and evaluate nitrate reduction in groundwater from denitrification. A reconnaissance study in the summer of 2010 along the 5,800-foot study reach located a subreach with clear evidence of nutrient-rich groundwater discharging to the stream. At the subreach, nitrate plus nitrite (referred to hereafter as nitrate) concentrations in groundwater discharging to the stream were high (average 2.75 milligrams per liter as nitrogen) along the right bank. The stream at this location had the highest stream nitrate concentrations (average 0.056 milligrams per liter as nitrogen) compared to other locations upstream and downstream of the subreach. As a result, the 2012 study focused on a 405-foot subreach of the East Fork Carson River centered where results from the 2010 study found the highest stream and groundwater concentrations of nitrate, as well as the greatest observed contributions of groundwater discharge to the stream. Groundwater nutrient concentrations were much higher than stream nutrient concentrations during the summer of 2012 during low streamflow conditions at the 405-foot subreach of the East Fork Carson River. Average groundwater nitrate and orthophosphate concentrations along the right bank of the 405‑foot subreach were 9 and 12 times higher, respectively, than in the stream at this subreach. Groundwater discharge rates to the study reach based on different methods varied from 0.09 to 1.2 cubic feet per second per mile. Estimated groundwater discharge rates to the right bank of the study subreach were used to calculate groundwater nutrient load estimates to the subreach right bank, which were found to be low when compared to stream nutrient loads. Elevated algal biomass levels above nuisance thresholds were observed during the summers of 2010 and 2012. The study reach was characterized as mesotrophic-eutrophic during the 2010 study and eutrophic during the 2012 study. The presence of algae caused daily dissolved oxygen and pH fluctuations in the stream, resulting in exceedances of the State of Nevada water-quality standards owing to low dissolved oxygen concentrations and high pH concentrations, although the standards might not have been applicable during 2012 because of extremely low streamflow. The addition of nutrients to the stream from the constant supply in groundwater discharge sustains the growth of algae during low streamflow conditions. In the summer when streamflow is low or very low, nutrient-rich groundwater discharge enters the stream through the sediment-water interface at the streambed. Because the attached algae is thick and stream velocity is low, the nutrient-rich water pools at the sediment-water interface. Higher nutrient concentrations at the streambed create a favorable microenvironment for algae attached to the substrate to consume available nutrients from the groundwater before the groundwater mixes with overlying stream water. The source of nitrate in groundwater in this subreach is anthropogenic because nitrate concentrations are greater than background groundwater nitrate concentrations in Douglas County, high groundwater nitrate concentrations are only found at the right bank of the stream near a housing development, and organic wastewater compounds indicative of human-derived sources were also detected in groundwater wells on the right bank of the stream. Nitrogen and oxygen isotope concentrations of nitrate in shallow groundwater were used to determine the specific source of the nitrate, but the isotopic values indicated denitrification was occurring. Further investigation is needed to determine the specific anthropogenic source of the nitrate in the groundwater because the denitrification present in all samples obscures the original source of nitrogen.

Nevada↗
USGS1982

Aquatic biology in Nederlo Creek, southwestern Wisconsin

This report presents the results of biologic investigations by the U.S. Geological Survey and the Wisconsin Department of Natural Resources during a study of hydrology and water quality in a small drainage basin in the "Driftless Area" of southwest Wisconsin. The investigation included aquatic macrophytes, periphytic and planktonic algae, benthic invertebrates, and trout population dynamics during 1967-78. The aquatic community is diverse and reasonably stable with little indication of environmental disturbance. Aquatic macrophyte population (dominated by Ranunculus aquatilis L., Veronica catenata Penn., and Nasturtium offlcinale) varies little from spring to fall. Periphytic and planktonic algae are predominantly diatoms, with the genus Achnanthes dominating both communities. Most genera of planktonic algae originate in the periphyton, but some true planktonic algae were identified. The benthic invertebrate population is dominated by Trichoptera and is a major food source for trout and forage fish. Biotic index values calculated from benthic invertebrate data indicate that water quality is very good to excellent. The trout population is low and represents only a small part of the total fish population both in biomass and numbers. Brown trout are usually stocked annually in the spring to enhance sport fishing, but by fall most trout are wild. The major environmental factors limiting trout population seem to be insufficient cover, insufficient pool depth and volume, and small spawning areas. The wild trout population is highly dependent on spawning success the previous fall.

Wisconsin↗
USGS1996

Assessment of water quality, nutrients, algal productivity, and management alternatives for low-flow conditions, South Umpqua River basin, Oregon, 1990-92

This report is an evaluation of the effects of nutrient loading on water quality in the South Umpqua River Basin. The study was done by the U.S. Geological Survey in cooperation with Douglas County, Oregon. Five wastewater-treatment plants were shown to contribute less than 15 percent of the flow, but more than 90 percent of the nitrogen and phosphorus, in the South Umpqua River during low streamflows in summer. These nutrient inputs were associated with, and largely responsible for, the dense growth of periphytic algae that covered the rocky channel and produced biomass values as large as 340 grams of ash-free dry weight per square meter. The nighttime respiration of periphytic algae caused violations of the Oregon water-quality standard, which requires a dissolved oxygen concentration of at least 90 percent of saturation, at most sites along the South Umpqua River. Photosynthesis by algae during daylight resulted in many exceedances of the Oregon pH standard of 8.5. Net productivity, calculated from hourly measurements of dissolved oxygen concentrations, was as much as 3.8 grams of oxygen per square meter per day. The magnitude of productivity increased with increases in dissolved inorganic nitrogen concentration and load. The large amount of nutrient uptake by algae resulted in lowered nutrient concentrations downstream from nutrient point sources. Management alternatives for the South Umpqua River Basin include several methods to reduce nutrient concentrations and loads. The reduction of dissolved-inorganic-nitrogen and soluble- reactive-phosphorus loads from wastewater- treatment-plant effluent would reduce the frequency of violations of water-quality standards. Flow augmentation probably would decrease water-quality problems in the river, but it is difficult to predict the magnitude of the effects of increased velocity and decreased temperature on algal growth. Land application and storage of wastewater-treatment-plant effluent during the summer months would reduce the input of nutrients from point sources. Three exceedances of the Oregon standard for fecal coliform of 200 colonies per 100 milliliters were associated with large streamflows, suggesting that nonpoint sources affect the river during periods of high runoff. Fecal-streptococcus counts were larger than historical values and require confirmation. Ammonia from wastewater-treatment-plant effluent, high pH values, and high temperatures present a potential for chronic ammonia toxicity in the lower reaches of the South Umpqua River; however, actual violations of standards for chronic concentrations were not detected because of diel fluctuations in pH and water temperature.

Oregon↗
USGS1997

Summary of information on aquatic biota and their habitats in the Willamette Basin, Oregon, through 1995

Available information on aquatic biota of the Willamette Basin was reviewed and summarized to describe current and historical conditions as part of the U.S. Geological Survey's National Water-Quality Assessment Program. Biological parameters emphasized include the status, distribution, and trends of aquatic biota, particularly algae, macroinvertebrates, and fish; the condition of aquatic and riparian habitat in which these biota reside; and the response of these biota to natural and human-associated impacts, including the level, type, and effect of contaminants. Considerable data are available on aquatic biota in the Willamette Basin, although the information is highly uneven relative to taxa and spatial scope. Extensive information exists for high-profile taxa, such as salmonid fishes, but less information is available for macroinvertebrates, and relatively little data exist for algae. Additionally, some areas such as the H.J. Andrews Experimental Forest and the main stem Willamette River have been extensively studied, whereas data are limited for many other areas. The basin supports a diverse aquatic macroinvertebrate fauna. Available data indicate a relatively high diversity of taxa and a high richness of Ephemeroptera, Plecoptera, Trichoptera (EPT) taxa in the upper reaches of the basin. In the lower main stem reaches, macroinvertebrate assemblages are dominated by pollution tolerant organisms and those adapted to low dissolved oxygen levels. Most of the limited data on algae are from sampling in the main stem Willamette River. Diatoms and blue-green algae are the dominant algal forms. Approximately 61 fish species occur in the basin, although nearly half are introduced. Species richness and distribution are highly correlated with elevation, stream gradient, and water temperature. High elevation, cold water, mountain streams are characterized by a few species of salmonids, sculpins, suckers, and whitefish. Low elevation, main stem reaches of major rivers and streams are dominated by warm water species, such as bass, catfish, and several species in the pan fish group. The only species of fish listed as threatened or endangered is the Oregon chub (Oregonichthys crameri). The effect of an expanding human presence in the Willamette Basin has substantially altered aquatic and riparian habitats, and the biota that use or reside in these habitats. Construction of dams, channelization and bank stabilization of rivers, species introductions, supplementations of fisheries through aquaculture, timber harvesting, agricultural activities, and urbanization have contributed to changes in aquatic habitats and biota from historical conditions. Aquatic toxicological investigations in the basin have focused primarily on fish. These studies have addressed chlorinated pesticides, polychlorinated biphenyls (PCBs), dioxins and furans, polycyclic aromatic hydrocarbons (PAHs), and trace elements in aquatic tissue, as well as fish health assessments, skeletal abnormalities, and aquatic toxicological responses. Several pesticides exceeded U.S. Environmental Protection Agency and State water-quality criteria for the protection of aquatic life. Elevated PCB, dioxin, and furan concentrations were associated with point sources, such as pulp and paper mills. Elevated concentrations of mercury in aquatic tissue were associated with several reservoirs. Fish health assessments and skeletal abnormality studies detected high levels of abnormalities in fish from the main stem Willamette River. Few investigations have examined aquatic toxicological responses, such as enzyme induction assays, growth assays, and biomarker studies.

Oregon↗
USGS1996

Physical, chemical, and biological characteristics of the Charlotte Harbor basin and estuarine system in southwestern Florida: A summary of the 1982-89 U.S. Geological Survey Charlotte Harbor assessment and other studies

The Charlotte Harbor estuarine system, having a surface area of about 270 square miles, averages about 7 feet in depth and is connected to deep water of the Gulf of Mexico through several passes and inlets between barrier islands. Three major rivers flow into the estuary--the Peace, the Myakka, and the Caloosahatchee. Freshwater and tidal flushing transport nutrients and other constituents from the basin through the estuary into the gulf. Flushing characteristics were evaluated using a two-dimensional hydrodynamic model. The model indicated that the time required to flush injected dye (simulated) from some subareas of the harbor was longer for reduced freshwater inflow than for typical freshwater inflow. After 30 days of simulation of reduced freshwater inflow, 42 percent of the dye injected into the upper harbor remained in the upper harbor, compared to 28 percent for typical freshwater inflow. The Charlotte Harbor estuary is usually well mixed or partially mixed in the vertical, but vertical salinity stratification does occur, primarily during late summer when freshwater inflows are greatest. A box model was developed that incorporated vertically averaged salinities to account indirectly for three-dimensional transport processes associated with vertical stratification. The box model predicts that under high (7,592 cubic feet per second) and average (2,470 cubic feet per second) freshwater inflows from the Peace and Myakka Rivers, 50 percent of the original water (present at the start of the model run) would be flushed from the northern part of the estuarine system into the Gulf of Mexico in 10 days and 20 days, respectively. The distribution of plant nutrients in the Charlotte Harbor Estuary is affected by nutrient inputs, freshwater and tidal flushing, mixing, and recycling processes in the estuary. The distributions of total phosphorus and orthophosphate are affected mainly by river input and physical mixing. The distribution of ammonia nitrogen is variable and is related more to recycling within the estuary than to input from the rivers. Ammonia concentrations increase in deeper water, probably in response to vertical salinity stratification and low concentrations of dissolved oxygen that foster regeneration of ammonia from bottom sediments. The distribution of nitrite plus nitrate nitrogen is nonconservative--concentrations are high in the rivers and decrease more rapidly in the estuary than expected due to dilution with sea water, probably because of phytoplankton uptake. Phytoplankton productivity and biomass are usually greatest during late summer near the mouths of the tidal rivers when freshwater inflow and nutrient loading are greatest. The highly colored freshwater runoff reduces light penetration and phytoplankton productivity in regions of the estuary where salinity is less than about 10 parts per thousand, but the nutrient-rich, colored water is diluted by seawater at midsalinities (10-20 parts per thousand) so that availability of light increases and inorganic nitrogen concentrations are still high enough to stimulate productivity and growth of phytoplankton. In much of the estuary, salinity is greater than 20 parts per thousand, and availability of inorganic nitrogen, not light, limits productivity and growth. Although the Charlotte Harbor estuarine system is relatively undisturbed, much of its basin has been altered by human activities. Streamflow decreased substantially during 1931-84 in parts of the Peace River, probably because of ground-water withdrawals in the basin. Nutrient concentrations generally increased in the rivers during 1970-85, because of an increase in the flow of wastewater and agricultural runoff. The concentrations of phosphorus are naturally high in the Peace River because of extensive phosphate deposits in the basin. The phosphate deposits also are relatively rich in radionuclides of the uranium-238 series, including radium-226. In the upper basin, these deposits are exposed in the riverbed. Extensive phosphate mining and processing have exposed additional deposits to surface runoff. Periodic spills of phosphate sediments (slimes) have contributed additional phosphorus and radium-226 to the river and estuary. A single spill can contribute a phosphorus load equal to the annual loading in the Peace River at Arcadia. The projected increase in population in the basin by the year 2020 would generate an additional 60 million gallons per day of domestic wastewater over that generated during 1980, which would increase nitrogen loading in the basin by more than 3 tons per day. Intensified agricultural and industrial developments, particularly expanding citrus production and phosphate mining, could generate additional loads of nutrients and a variety of inorganic and organic contaminants. Increased inputs of nutrients, particularly nitrogen, could encourage growth and increase abundance of phytoplankton and benthic and epiphytic algae. If water were less colored as a result of reduced freshwater inflow, undesirable algal growth could be exacerbated because of increased availability of light. Increased abundance of phytoplankton and other algae could likely change dissolved-oxygen concentrations in the estuary, resulting in greater day-to-night fluctuations and the possible depletion of dissolved oxygen in deep water. At the present time, near-anaerobic conditions occur for days or weeks in the deep water (more than 9 feet) of the northern harbor during late summer. These conditions could become more persistent with time and over wider areas, if phytoplankton and other algae increase in abundance and in their contribution to benthic oxygen demand. An increased abundance of phytoplankton and other algae also would reduce light penetration and adversely affect seagrasses.

Florida↗
USGS2009

Cascading effects of fishing on Galapagos rocky reef communities: reanalysis using corrected data

This article replaces Sonnenholzner et al. (2007; Mar Ecol Prog Ser 343:77–85 ), which was retracted on September 19, 2007, due to errors in entry of data on sea urchins. We sampled 10 highly fished and 10 (putatively) lightly fished shallow rocky reefs in the southeastern area of the Galapagos Marine Reserve, Ecuador. After the correction, these are the new results: there was a negative association between slate-pencil urchins Eucidaris galapagensis and non-coralline algae. In addition, pencil urchins were less abundant where there were many predators. An indirect positive association between predators and non-coralline algae occurred. Fishing appeared to affect this trophic cascade. The spiny lobster Panulirus penicillatus , the slipper lobster Scyllarides astori , and the Mexican hogfish Bodianus diplotaenia were significantly less abundant at highly fished sites. Urchin density was higher at highly fished sites. Non-coralline algae were nearly absent from highly fished sites, where a continuous carpet of the anemone Aiptasia sp. was recorded, and the algal assemblage was mainly structured by encrusting coralline and articulated calcareous algae.

Marine Ecology Progress Series↗
USGS2010

The Sargassum Frogfish ( Histrio histrio Linnaeus) observed in mangroves in St. John, US Virgin Islands

The Sargassum Frogfish ( Histrio histrio ), the only pelagic member of the frogfish family Antennariidae, is considered an obligate associate of floating mats of the brown algae Sargassum natans and S. fluitans (Adams 1960; Dooley 1972; Pietsch and Grobecker 1987). Between February and April 2010, 20 of these fish were observed in three mangrove-fringed bays in Virgin Islands Coral Reef National Monument, St. John, US Virgin Islands. All of them were clinging to clumps of the red alga Acanthophora spicifera growing on the submerged prop roots of red mangrove trees ( Rhizophora mangle ) distributed along an estimated total of 2,160 mof shoreline (Fig. 1). All of the fish were at a depth of less than 0.5 meters. Two individuals were seen on one prop root, but the other 18 were solitary. Their estimated standard lengths ranged from about 20 to 100 mm. Littler and Littler (2000, p. 295) published a photograph of one individual in blades of the green alga Ulva lactuca growing on a prop root in Belize. This is the first report of the Sargassum Frogfish living in association with attached algae.

Virgin Islands Coral Reef National Monument;St. Jo↗
USGS2001

Microbial lime-mud production and its relation to climate change

Microbial calcification has been identified as a significant source of carbonate sediment production in modern marine and lacustrine environments around the globe. This process has been linked to the production of modern whitings and large, micritic carbonate deposits throughout the geologic record. Furthermore, carbonate deposits believed to be the result of cyanobacterial and microalgal calcification suggest that the potential exists for long-term preservation of microbial precipitates and storage of carbon dioxide (CO 2 ). Recent research has advanced our understanding of the microbial-calcification mechanism as a photosynthetically driven process. However, little is known of the effects of this process on inorganic carbon cycling or of the effects of changing climate on microbial-calcification mechanisms. Laboratory experiments on microbial cellular physiology demonstrate that cyanobacteria and green algae can utilize different carbon species for metabolism and calcification. Cyanobacterial calcification relies on bicarbonate (HCO 3 – )utilization while green algae use primarily CO 2 . Therefore, depending on which carbonate species (HCO 3 – or CO 2 ) dominates in the ocean or lacustrine environments (a condition ultimately linked to atmospheric partial pressure PCO 2 ), the origin of lime-mud production by cyanobacteria and/or algae may fluctuate through geologic time. Trends of cyanobacteria versus algal dominance in the rock record corroborate this conclusion. These results suggest that relative species abundances of calcareous cyanobacteria and algae in the Phanerozoic may serve as potential proxies for assessing paleoclimatic conditions, including fluctuations in atmospheric PCO 2 .

AAPG Studies in Geology↗
USGS2022

Dietary composition and fatty acid content of giant salmonflies (Pteronarcys californica) in two Rocky Mountain rivers

Many aquatic invertebrates are declining or facing extinction from stressors that compromise physiology, resource consumption, reproduction, and phenology. However, the influence of these common stressors specifically on consumer–resource interactions for aquatic invertebrate consumers is only beginning to be understood. We conducted a field study to investigate Pteronarcys californica (i.e., the “giant salmonfly”), a large-bodied insect that is ecologically and culturally significant to rivers throughout the western United States. We sampled gut contents and polyunsaturated fatty acid composition of salmonflies to compare resource consumption across river (Madison or Gallatin, Montana), sex (male or female), and habitat (rock or woody debris). We found that allochthonous detritus comprised the majority of salmonfly diets in the Gallatin and Madison Rivers, making up 68% of the gut contents on average, followed by amorphous detritus, diatoms, and filamentous algae. Diets showed little variation across river, sex, or length. Minor differences in diets were detected by habitat type, with a higher proportion of diatoms in the diets of salmonflies collected from rocky habitat compared to woody debris. Fatty acid composition generally supported the results of gut content analysis but highlighted the importance of primary producers. The presence of eicosapentaenoic acid (20:5n-3) and alpha linolenic acid (18:3n-3) indicated consumption of diatoms and filamentous green algae, respectively. Our research underscores the importance of a healthy riparian zone that provides allochthonous detritus for invertebrate nutrition as well as the role of algae as an important source of fatty acids.

Montana↗
USGS1993

Bioaccumulation of organic and inorganic selenium in a laboratory food chain

Aquatic organisms accumulated selenium (Se) from inorganic and organic Se species via aqueous and food-chain exposure routes. We measured aqueous and food-chain Se bioaccumulation from selenate, selenite, and seleno-L-methionine in a laboratory food chain of algae ( Chlamydomonas reinhardtii ), daphnids ( Daphnia magna ), and fish (bluegill, Lepomis macrochirus ). Selenium concentrations were monitored radiometrically with 75 Se-labeled compounds. All three organisms concentrated Se more strongly from aqueous selenomethionine than from either inorganic Se species. Bioconcentration factors (BCFs) estimated from 1 μg Se/L Se-methionine exposures were approximately 16,000 for algae, 200,000 for daphnids, and 5,000 for bluegills. Algae and daphnids concentrated Se more strongly from selenite (BCFs = 220–3,600) than selenate (BCFs = 65–500) whereas bluegills concenrated Se about equally from both inorganic species (estimated BCFs = 13 to 106). Bioaccumulation of foodborne Se by daphnids and bluegills was similar in food chains dosed with different Se species. Daphnids and bluegills did not accumulate Se concentrations greater than those in their diet, except at very low dietary Se concentrations. Food-chain concentration factors (CFs) for daphnids decreased from near 1.0 to 0.5 with increases in algal Se concentrations, whereas CFs estimated from bluegill exposures averaged 0.5 over a range of foodborne Se concentrations. In exposures based on selenite, bluegills accumulated greater Se concentrations from food than from water. Aqueous and food-chain Se uptakes were approximately additive, and depuration rates were similar in aqueous, food-chain, and combined exposures. Our results suggest that bluegills in Secontaminated habitats accumulate inorganic Se species primarily via food-chain uptake, although organoselenium compounds such as Se-methionine may contribute significantly to Se bioaccumulation by bluegills via both aqueous and food-chain uptake.

Environmental Toxicology and Chemistry↗
USGS2025

Water residence time and water depth influence on nutrient conditions, eutrophication endpoints and habitat quality in backwater lakes of a large floodplain river

Many eutrophication studies focus on the external supply of critical nutrients like nitrogen and phosphorus, but hydrology and geomorphology can enhance or dampen the effects of excessive nutrient supply. We studied six backwater lakes in the Upper Mississippi River that varied in water residence time and water depth. Eutrophication in these systems is responsible for negative impacts such as cyanobacterial blooms and toxicity, and floating plant and algal mats that disrupt recreational water uses. Increasing backwater residence time was associated with more nitrate removal and a greater likelihood of nitrogen limitation, as well as greater accumulations of duckweed. Backwaters with greater depth and lower nitrogen concentration had less likelihood of filamentous algal accumulations. The median water residence time of backwaters with low duckweed (11.7 days) and no filamentous algae (16.9 days) approached the 12-day target to maintain overwintering conditions in backwaters for fisheries survival, supporting that water residence times in this range would likely improve both winter and summer water quality. Mean depth in backwaters with low duckweed and no filamentous algae was ~1.3 m, while shallower backwaters were more likely to produce duckweed and filamentous algae mats. This indicates that deeper backwaters might reduce the likelihood of eutrophication impacts. Natural resource management at the local level may not always be able to answer global and regional threats, but habitat restoration of hydrology and geomorphology can possibly alleviate or reduce large-scale threats at the local level.

Minnesota, Wisconsin↗
USGS1996

A new assay for quantifying brown algal phlorotannins and comparisons to previous methods

Quantitative measurement of phlorotannins (polyphenolics) in brown algae (Phaeophyta) by colorimetric assays can be confounded because: (1) most such assays also react to nonphlorotannin substances (interferences) and (2) the appropriate reference compound for such assays is not always clear, although phloroglucinol is typically used. We developed a new assay in which 2,4-dimethoxybenzaldehyde (DMBA) reacts specifically with 1,3-and 1,3,5-substituted phenols (e.g., phlorotannins) to form a colored product. This new assay, as well as eliminating the problem of measuring interferences, is inexpensive, rapid, and can be used with small sample volumes. We recommend it for all assays of phlorotannins from one or a set of closely related species where the structural types of phlorotannins present are likely to be similar among samples. It is also appropriate for broader surveys of phlorotannin levels across many species, but in this case a reference must be chosen with care. We also compared the DMBA assay to existing assays, including the Folin-Denis [both before and after the samples were mixed with polyvinylpolypyrrolidone (PVPP)] and the Prussian blue assays. PVPP was not 100% efficient (and often much less) at removing phlorotannins from solution, and its effectiveness varied among different phlorotannins. Thus, in contrast to previous studies, measuring phenolic levels in extracts before and after treatment with PVPP will not necessarily result in an interference-free measure of phlorotannins. Based on an analysis of reactive substances in red and green algae (which do not contain phlorotannins) in the Folin-Denis and Prussian blue assays, we estimate that the average level of interferences (nonphlorotannins) in brown algae measured in these two assays is on the order of 0.5% by dry weight.

Journal of Chemical Ecology↗
USGS2005

Characterizing lesions in corals from American Samoa

The study of coral disease has suffered from an absence of systematic approaches that are commonly used to determine causes of diseases in animals. There is a critical need to develop a standardized and portable nomenclature for coral lesions in the field and to incorporate more commonly available biomedical tools in coral disease surveys to determine the potential causes of lesions in corals. We characterized lesions in corals from American Samoa based on gross and microscopic morphology and classified them as discoloration, growth anomalies, or tissue loss. The most common microscopic finding in corals manifesting discoloration was the depletion of zooxanthellae, followed by necrosis, sometimes associated with invasive algae or fungi. The most common microscopic lesion in corals manifesting tissue loss was cell necrosis often associated with algae, fungi, or protozoa. Corals with growth anomaly had microscopic evidence of hyperplasia of gastrovascular canals, followed by necrosis associated with algae or metazoa (polychaete worms). Several species of apparently normal corals also had microscopic changes, including the presence of bacterial aggregates or crustacea in tissues. A single type of gross lesion (e.g., discoloration) could have different microscopic manifestations. This phenomenon underlines the importance of using microscopy to provide a more systematic description of coral lesions and to detect potential pathogens associated with these lesions.

Coral Reefs↗
USGS2020

Possible control of acute outbreaks of a marine fungal pathogen by nominally herbivorous tropical reef fish

Primary producers in terrestrial and marine systems can be affected by fungal pathogens threatening the provision of critical ecosystem services. Crustose coralline algae (CCA) are ecologically important members of tropical reef systems and are impacted by coralline fungal disease (CFD) which manifests as overgrowth of the CCA crust by fungal lesions causing partial to complete mortality of the CCA host. No natural controls for CFD have been identified, but nominally herbivorous fish could play a role by consuming pathogenic fungi. We documented preferential grazing on fungal lesions by adults of six common reef-dwelling species of herbivorous Acanthuridae and Labridae, (surgeonfish and parrotfish) which collectively demonstrated an ~ 80-fold higher grazing rate on fungal lesions relative to their proportionate benthic coverage, and a preference for lesions over other palatable substrata (e.g. live scleractinian coral, CCA, or algae). Furthermore, we recorded a ~ 600% increase in live CFD lesion size over an approximately 2-week period when grazing by herbivorous fish was experimentally excluded suggesting that herbivorous reef fish could control CFD progression by directly reducing biomass of the fungal pathogen. Removal rates may be sufficient to allow CCA to recover from infection and explain historically observed natural waning behaviour after an outbreak. Thus, in addition to their well-known role as determinants of macroalgal overgrowth of reefs, herbivorous fish could thus also be important in control of diseases affecting crustose coralline algae that stabilize the foundation of coral reef substrata.

Palmyra Atoll National Wildlife Refuge↗
USGS2010

A comparison of algal, macroinvertebrate, and fish assemblage indices for assessing low-level nutrient enrichment in wadeable Ozark streams

Biotic indices for algae, macroinvertebrates, and fish assemblages can be effective for monitoring stream enrichment, but little is known regarding the value of the three assemblages for detecting perturbance as a consequence of low-level nutrient enrichment. In the summer of 2006, we collected nutrient and biotic samples from 30 wadeable Ozark streams that spanned a nutrient-concentration gradient from reference to moderately enriched conditions. Seventy-three algal metrics, 62 macroinvertebrate metrics, and 60 fish metrics were evaluated for each of the three biotic indices. After a group of candidate metrics had been identified with multivariate analysis, correlation procedures and scatter plots were used to identify the four metrics having strongest relations to a nutrient index calculated from log transformed and normalized total nitrogen and total phosphorus concentrations. The four metrics selected for each of the three biotic indices were: algae—the relative abundance of most tolerant diatoms, the combined relative abundance of three species of Cymbella , mesosaprobic algae percent taxa richness, and the relative abundance of diatoms that are obligate nitrogen heterotrophs; macroinvertebrate—the relative abundance of intolerant organisms, Baetidae relative abundance, moderately tolerant taxa richness, and insect biomass; fish—herbivore and detritivore taxa richness, pool species relative abundance, fish catch per unit effort, and black bass ( Micropterus spp.) relative abundance. All three biotic indices were negatively correlated to nutrient concentrations but the algal index had a higher correlation (rho = −0.89) than did the macroinvertebrate and fish indices (rho = −0.63 and −0.58, respectively). Biotic index scores were lowest and nutrient concentrations were highest for streams with basins having the highest poultry and cattle production. Because of the availability of litter for fertilizer and associated increases in grass and hay production, cattle feeding capacity increases with poultry production. Studies are needed that address the synergistic effect of poultry and cattle production on Ozark streams in high production areas before ecological risks can be adequately addressed.

Arkansas, Oklahoma↗
USGS2020

Characterizing benthic macroinvertebrate and algal biological condition gradient models for California wadeable Streams, USA

The Biological Condition Gradient (BCG) is a conceptual model that describes changes in aquatic communities under increasing levels of anthropogenic stress. The BCG helps decision-makers connect narrative water quality goals (e.g., maintenance of natural structure and function) to quantitative measures of ecological condition by linking index thresholds based on statistical distributions (e.g., percentiles of reference distributions) to expert descriptions of changes in biological condition along disturbance gradients. As a result, the BCG may be more meaningful to managers and the public than indices alone. To develop a BCG model, biological response to stress is divided into 6 levels of condition, represented as changes in biological structure (abundance and diversity of pollution sensitive versus tolerant taxa) and function. We developed benthic macroinvertebrate (BMI) and algal BCG models for California perennial wadeable streams to support interpretation of percentiles of reference-based thresholds for bioassessment indices (i.e., the California Stream Condition Index [CSCI] for BMI and the Algal Stream Condition Index [ASCI] for diatoms and soft-bodied algae). Two panels (one of BMI ecologists and the other of algal ecologists) each calibrated a general BCG model to California wadeable streams by first assigning taxa to specific tolerance and sensitivity attributes, and then independently assigning test samples (264 BMI and 248 algae samples) to BCG Levels 1–6. Consensus on the assignments was developed within each assemblage panel using a modified Delphi method. Panels then developed detailed narratives of changes in BMI and algal taxa that correspond to the 6 BCG levels. Consensus among experts was high, with 81% and 82% expert agreement within 0.5 units of assigned BCG level for BMIs and algae, respectively. According to both BCG models, the 10th percentiles index scores at reference sites corresponded to a BCG Level 3, suggesting that this type of threshold would protect against moderate changes in structure and function while allowing loss of some sensitive taxa. The BCG provides a framework to interpret changes in aquatic biological condition along a gradient of stress. The resulting relationship between index scores and BCG levels and narratives can help decision-makers select thresholds and communicate how these values protect aquatic life use goals.

California↗
USGS2015

Prevalence of toxin-producing Clostridium botulinum associated with the macroalga Cladophora in three Great Lakes: Growth and management

The reemergence of avian botulism caused by Clostridium botulinum type E has been observed across the Great Lakes in recent years. Evidence suggests an association between the nuisance algae, Cladophora spp., and C. botulinum in nearshore areas of the Great Lakes. However, the nature of the association between Cladophora and C. botulinum is not fully understood due, in part, to the complex food web interactions in this disease etiology. In this study, we extensively evaluated their association by quantitatively examining population size and serotypes of C. botulinum in algal mats collected from wide geographic areas in lakes Michigan, Ontario, and Erie in 2011–2012 and comparing them with frequencies in other matrices such as sand and water. A high prevalence (96%) of C. botulinum type E was observed in Cladophora mats collected from shorelines of the Great Lakes in 2012. Among the algae samples containing detectable C. botulinum , the population size of C. Botulinum type E was 10 0 –10 4 MPN/g dried algae, which was much greater (up to 10 3 fold) than that found in sand or the water column, indicating that Cladophora mats are sources of this pathogen. Mouse toxinantitoxin bioassays confirmed that the putative C. botulinum belonged to the type E serotype. Steam treatment was effective in reducing or eliminating C. botulinum type E viable cells in Cladophora mats, thereby breaking the potential transmission route of toxin up to the food chain. Consequently, our data suggest that steam treatment incorporated with a beach cleaning machine may be an effective treatment of Cladophora -borne C. botulinum and may reduce bird mortality and human health risks.

Lake Erie, Lake Michigan, Lake Ontario↗
USGS2004

Habitat of endangered white abalone, Haliotis sorenseni

Surveys with a submersible at offshore islands and banks in southern California found that white abalone were most abundant at depths between 43 and 60 m. This is deeper than estimates taken when white abalone were more abundant. Densities were highest at sites far from fishing ports. Controlling for depth and site found that white abalone were significantly more abundant in areas with Laminaria farlowii (an alga) but abalone were not associated with areas high in the cover of other algae ( Pelagophycus porra or Eisenia arborea ) or the amount of sand in the habitat (except that abalone always occurred on rock). Within an area with abalone, the particular rock they occurred on was significantly larger than unoccupied neighboring rocks. Occupied rocks were not significantly different in algal cover or in sea urchin density than unoccupied neighboring rocks. The position of abalone on a rock was nearer to the rock–sand interface than would be expected based on a random distribution. More white abalone were feeding when in association with red urchins, perhaps because both grazers capture drift algae to eat. These data may aid future efforts to locate white abalone brood stock and identify locations for outplanting.

Biological Conservation↗