Non-stationary and interactive effects of climate and competition on pink salmon productivity.

Pacific salmon (Oncorhynchus spp.) are exposed to increased environmental change and multiple human stressors. To anticipate future impacts of global change and to improve sustainable resource management, it is critical to understand how wild salmon populations respond to stressors associated with human-caused changes such as climate warming and ocean acidification, as well as competition in the ocean, which is intensified by the large-scale production and release of hatchery reared salmon. Pink salmon (O. gorbuscha) are a keystone species in the North Pacific Ocean and support highly valuable commercial fisheries. We investigated the joint effects of changes in ocean conditions and salmon abundances on the productivity of wild pink salmon. Our analysis focused on Prince William Sound in Alaska, because the region accounts for ~50% of the global production of hatchery pink salmon with local hatcheries releasing 600-700 million pink salmon fry annually. Using 60 years of data on wild pink salmon abundances, hatchery releases, and ecological conditions in the ocean, we find evidence that hatchery pink salmon releases negatively affect wild pink salmon productivity, likely through competition between wild and hatchery juveniles in nearshore marine habitats. We find no evidence for effects of ocean acidification on pink salmon productivity. However, a change in the leading mode of North Pacific climate in 1988-1989 weakened the temperature-productivity relationship and altered the strength of intraspecific density dependence. Therefore, our results suggest non-stationary (i.e., time varying) and interactive effects of ocean climate and competition on pink salmon productivity. Our findings further highlight the need for salmon management to consider potential adverse effects of large-scale hatchery production within the context of ocean change.

Ecosystem response persists after a prolonged marine heatwave.

Some of the longest and most comprehensive marine ecosystem monitoring programs were established in the Gulf of Alaska following the environmental disaster of the Exxon Valdez oil spill over 30 years ago. These monitoring programs have been successful in assessing recovery from oil spill impacts, and their continuation decades later has now provided an unparalleled assessment of ecosystem responses to another newly emerging global threat, marine heatwaves. The 2014-2016 northeast Pacific marine heatwave (PMH) in the Gulf of Alaska was the longest lasting heatwave globally over the past decade, with some cooling, but also continued warm conditions through 2019. Our analysis of 187 time series from primary production to commercial fisheries and nearshore intertidal to offshore oceanic domains demonstrate abrupt changes across trophic levels, with many responses persisting up to at least 5 years after the onset of the heatwave. Furthermore, our suite of metrics showed novel community-level groupings relative to at least a decade prior to the heatwave. Given anticipated increases in marine heatwaves under current climate projections, it remains uncertain when or if the Gulf of Alaska ecosystem will return to a pre-PMH state.

Glacier Retreat and Pacific Salmon.

Glaciers have shaped past and present habitats for Pacific salmon (Oncorhynchus spp.) in North America. During the last glacial maximum, approximately 45% of the current North American range of Pacific salmon was covered in ice. Currently, most salmon habitat occurs in watersheds in which glacier ice is present and retreating. This synthesis examines the multiple ways that glacier retreat can influence aquatic ecosystems through the lens of Pacific salmon life cycles. We predict that the coming decades will result in areas in which salmon populations will be challenged by diminished water flows and elevated water temperatures, areas in which salmon productivity will be enhanced as downstream habitat suitability increases, and areas in which new river and lake habitat will be formed that can be colonized by anadromous salmon. Effective conservation and management of salmon habitat and populations should consider the impacts of glacier retreat and other sources of ecosystem change.

Benefits and risks of diversification for individual fishers.

Individuals relying on natural resource extraction for their livelihood face high income variability driven by a mix of environmental, biological, management, and economic factors. Key to managing these industries is identifying how regulatory actions and individual behavior affect income variability, financial risk, and, by extension, the economic stability and the sustainable use of natural resources. In commercial fisheries, communities and vessels fishing a greater diversity of species have less revenue variability than those fishing fewer species. However, it is unclear whether these benefits extend to the actions of individual fishers and how year-to-year changes in diversification affect revenue and revenue variability. Here, we evaluate two axes by which fishers in Alaska can diversify fishing activities. We show that, despite increasing specialization over the last 30 years, fishing a set of permits with higher species diversity reduces individual revenue variability, and fishing an additional permit is associated with higher revenue and lower variability. However, increasing species diversity within the constraints of existing permits has a fishery-dependent effect on revenue and is usually (87% probability) associated with increased revenue uncertainty the following year. Our results demonstrate that the most effective option for individuals to decrease revenue variability is to participate in additional or more diverse fisheries. However, this option is expensive, often limited by regulations such as catch share programs, and consequently unavailable to many individuals. With increasing climatic variability, it will be particularly important that individuals relying on natural resources for their livelihood have effective strategies to reduce financial risk.

Changes in Size and Age of Chinook Salmon Oncorhynchus tshawytscha Returning to Alaska.

The average sizes of Pacific salmon have declined in some areas in the Northeast Pacific over the past few decades, but the extent and geographic distribution of these declines in Alaska is uncertain. Here, we used regression analyses to quantify decadal trends in length and age at maturity in ten datasets from commercial harvests, weirs, and spawner abundance surveys of Chinook salmon Oncorhynchus tshawytscha throughout Alaska. We found that on average these fish have become smaller over the past 30 years (~6 generations), because of a decline in the predominant age at maturity and because of a decrease in age-specific length. The proportion of older and larger 4-ocean age fish in the population declined significantly (P < 0.05) in all stocks examined by return year or brood year. Our analyses also indicated that the age-specific lengths of 4-ocean fish (9 of 10 stocks) and of 3-ocean fish (5 of 10 stocks) have declined significantly (P < 0.05). Size-selective harvest may be driving earlier maturation and declines in size, but the evidence is not conclusive, and additional factors, such as ocean conditions or competitive interactions with other species of salmon, may also be responsible. Regardless of the cause, these wide-spread phenotypic shifts influence fecundity and population abundance, and ultimately may put populations and associated fisheries at risk of decline.

Proof of concept for the use of macroinvertebrates as indicators of polychlorinated biphenyls (PCB) contamination in Lake Hartwell.

The US Environmental Protection Agency (USEPA) develops methods and tools for evaluating risk management strategies for sediments contaminated with polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and other legacy pollutants. Monitored natural recovery is a risk management alternative that relies on existing physical, chemical, and biological processes to contain, destroy, and/or reduce the bioavailability or toxicity of in-place contaminants. These naturally occurring processes are monitored to ensure that management and recovery are progressing as expected. One approach frequently used to evaluate the recovery of contaminated sediments and associated biota is the assessment of contaminant tissue levels, or body burden concentrations, in top trophic level fish. In the present study, aquatic invertebrates were examined as an indicator of recent exposure to PCBs. The approach aimed to determine whether invertebrates collected using artificial substrates (i.e., Hester-Dendy samplers) could be used to discriminate among contaminated sites through the analyses of PCBs in whole homogenates of macroinvertebrates. Macroinvertebrates were sorted, preserved, and analyzed for total PCBs (t-PCBs), by summing 107 PCB congeners. Macroinvertebrate body burden concentrations showed similar trends to sediment t-PCB concentrations at the sites sampled. The results indicate that macroinvertebrates can be used to assess sediment contamination among sites that have different PCB contamination levels.

Frequency and timing of nonconvulsive status epilepticus in comatose post-cardiac arrest subjects treated with hypothermia.

BACKGROUND: Therapeutic hypothermia (TH) improves outcomes in comatose patients resuscitated from cardiac arrest. However, nonconvulsive status epilepticus (NCSE) may cause persistent coma. The frequency and timing of NCSE after cardiac arrest is unknown. METHODS: Review of consecutive subjects treated with TH and receiving continuous EEG (cEEG) monitoring between 8/1/2009 and 11/16/2010. Demographic data, survival, and functional outcome were prospectively recorded. Each cEEG file was analyzed using standard definitions to define NCSE. Data were analyzed using descriptive and nonparametric statistics. RESULTS: Mean age of the 101 subjects was 57 years (SD 15) with most subjects being male (N = 55, 54%) and experiencing out-of-hospital cardiac arrest (N = 78; 77%). Ventricular fibrillation was the initial cardiac rhythm in 39 (38%). All subjects received TH. Thirty subjects (30%) awoke at a median of 41 h (IQR 30, 61) after cardiac arrest. A total of 29/30 (97%) subjects surviving to hospital discharge were awake. Median interval from arrest to placement of cEEG was 9 h (IQR 6, 12), at which time the mean temperature was 33.9°C. NCSE occurred in 12 (12%) subjects. In 3/12 (25%) subjects, NCSE was present when the cEEG recording began. In 4 subjects, NCSE occurred within 8 h of cEEG recording. One (8%) subject with NCSE survived in a vegetative state. CONCLUSIONS: NCSE is common in comatose post-cardiac arrest subjects receiving TH. Most seizures occur within the first 8 h of cEEG recording and within the first 12 h after resuscitation from cardiac arrest. Outcomes are poor in those who experience NCSE.

Generalized paroxysmal fast activity and tonic seizures in older adults.

Generalized paroxysmal fast activity is an uncommon ictal EEG pattern usually associated with tonic seizures. Patients with generalized paroxysmal fast activity typically have multiple seizure types beginning in childhood and are refractory to antiepileptic drug therapy. We describe 3 hospitalized adult patients (age, older than 55 years) with new-onset tonic movements, noted during an acute illness, associated with generalized paroxysmal fast activity on EEG. These seizures were characterized by subtle stiffening of the arms, trunk, and face for up to 3 seconds. All patients had multiple medical problems and polypharmacy. None had a history of static encephalopathy, other epileptiform abnormalities on EEG, other seizure types, or significant neuroimaging abnormalities. In contrast to previously described reports in children, all three adults responded to antiepileptic drug monotherapy. EEG played a critical role in differentiating tonic seizures from nonepileptic movements in these three cases.

Effect of biostimulation on the microbial community in PCB-contaminated sediments through periodic amendment of sediment with iron.

Reductive dehalogenation of polychlorinated biphenyls (PCBs) by indigenous dehalorespiring microorganisms in contaminated sediments may be enhanced via biostimulation by supplying hydrogen generated through the anaerobic corrosion of elemental iron added to the sediment. In this study, the effect of periodic amendment of sediment with various dosages of iron on the microbial community present in sediment was investigated using phospholipid fatty acid analysis (PLFA) over a period of 18 months. Three PCB-contaminated sediments (two freshwater lake sediments and one marine sediment) were used. Signature biomarker analysis of the microbial community present in all three sediments revealed the enrichment of Dehalococcoides species, the population of which was sustained for a longer period of time when the sediment microcosms were amended with the lower dosage of iron (0.01 g iron per g dry sediment) every 6 months as compared to the blank system (without iron). Lower microbial stress levels were reported for the system periodically amended with 0.01 g of iron per g dry sediment every 6 months, thus reducing the competition from other hydrogen-utilizing microorganisms like methanogens, iron reducers, and sulfate reducers. The concentration of hydrogen in the system was found to be an important factor influencing the shift in microbial communities in all sediments with time. Periodic amendment of sediment with larger dosages of iron every 3 months resulted in the early prevalence of Geobacteraceae and sulfate-reducing bacteria followed by methanogens. An average pH of 8.4 (range of 8.2-8.6) and an average hydrogen concentration of 0.75% (range of 0.3-1.2%) observed between 6 and 15 months of the study were found to be conducive to sustaining the population of Dehalococcoides species in the three sediments amended with 0.01 g iron per g dry sediment. Biostimulation of indigenous PCB dechlorinators by the periodic amendment of contaminated sediments with low dosages of iron metal may therefore be an effective technology for remediation of PCB-contaminated sediments.

Fate of sex hormones in two pilot-scale municipal wastewater treatment plants: conventional treatment.

The fate of seven sex hormones (estrone (E1), estradiol (E2), estriol (E3), ethinylestradiol (EE2), testosterone, androstenedione, and progesterone) was determined in two pilot-scale wastewater treatment plants operated under conventional loading conditions. The levels of hormones in both the liquid and the solid matrixes of the plants were determined. Each of the two 20-l/h pilot-scale plants consisted of a primary clarifier followed by a three-stage aeration tank and a final clarifier. The primary sludge and the waste activated sludge (WAS) were digested anaerobically in one pilot plant and aerobically in the other. The pilot plants were fed a complex synthetic wastewater spiked with the hormones. Levels of testosterone, androstenedione and progesterone were close to method detection limit (MDL) concentrations in the final and digester effluents (both liquid and solid phases) and were considered as completely removed. Average mass flux removals from the liquid streams (plant influent minus secondary clarifier effluent) for the natural estrogens were 82% for E1, 99% for E2, and 89% for (E1+E2). An average overall removal of only 42% was achieved for EE2. These values reflect removals averaged for the two pilot plants.

Increasing the yield of EEG.

The EEG is the most common neurodiagnostic test performed to evaluate patients with suspected seizures. The majority of EEGs are requested in patients because of suspected seizures or for seizure management. It is unlikely that the patient's usual spell will be recorded during a routine EEG. Therefore, several activation techniques have been used in clinical EEG to help increase the occurrence of interictal epileptiform abnormalities, which are highly correlated with the diagnosis of a seizure disorder. EEG laboratories have long employed these techniques, which include hyperventilation, intermittent photic stimulation, sleep, and sleep deprivation. However, despite being utilized in routine clinical EEGs for decades, a number of differing views on the usefulness and indications for these procedures exist. This review will evaluate these procedures and review their history, technique, effectiveness, controversies, and unanswered questions.

Successional and physical controls on the retention of nitrogen in an undisturbed boreal forest ecosystem.

Floristic succession in the boreal forest can have a dramatic influence on ecosystem nutrient cycling. We predicted that a decrease in plant and microbial demand for nitrogen (N) during the transition from mid- to late-succession forests would induce an increase in the leaching of dissolved inorganic nitrogen (DIN), relative to dissolved organic nitrogen (DON). To test this, we examined the chemistry of the soil solution collected from within and below the main rooting zones of mid- and late-succession forests, located along the Tanana River in interior Alaska. We also used a combination of hydrological and chemical analyses to investigate a key assumption of our methodology: that patterns of soil water movement did not change during this transition. Between stands, there was no difference in the proportion of DIN below the rooting zone. 84-98% of DIN at both depths consisted of nitrate, which was significantly higher in the deeper mineral soil than at the soil surface (0.46+/-0.12 mg NO(-) (3) -N l(-1) vs 0.17+/-0.12 mg NO(-) (3) -N l(-1), respectively), and 79-92% of the total dissolved N consisted of DON. Contrary to our original assumption that nutrients were primarily leached downward, out of the rooting zone, we found much evidence to suggest that the glacially-fed Tanana River (>200 m from these stands) was contributing to the influx of water and nutrients into the soil active layer of both stands. Soil water potentials were positively correlated with river discharge; and ionic and isotopic (delta(18)O of H(2)O) values of the soil solution closely matched those of river water. Thus, our ability to elucidate biological control over ecosystem N retention was confounded by riverine nutrient inputs. Climatic warming is likely to extend the season of glacial melt and increase riverine nutrient inputs to forests along glacially-fed rivers.

The interpretation of the EEG in stupor and coma.

This review discusses a variety of causes of stupor and coma and associated electroencephalographic (EEG) findings. These include metabolic disturbances such as hepatic or renal dysfunction, which are often characterized by slowing of background rhythms and triphasic waves. Hypoxia and drug intoxications can produce a number of abnormal EEG patterns such as burst suppression, alpha coma, and spindle coma. Structural lesions, either supra- or infratentorial, are reviewed. EEGs in the former may show focal disturbances such as delta and theta activity, epileptiform abnormalities, and attenuation of faster frequencies. In infratentorial lesions, the EEG may appear normal, particularly with a pontine lesion. Some patients may be encephalopathic because of ongoing epileptic activity with minimal or no motor movements. This entity, nonconvulsive status epilepticus (NCSE), is difficult to diagnose in obtunded/comatose patients, and an EEG is required to verify the diagnosis and to monitor treatment. Several EEG patterns and their interpretation in suspected cases of NCSE such as periodic lateralized epileptiform discharges (PLEDs), bilateral independent periodic lateralized epileptiform discharges (BIPLEDs), generalized periodic epileptiform discharges (GPEDs), and triphasic waves are reviewed. Other entities discussed include the locked-in syndrome, neocortical death, persistent vegetative state, brainstem death, and brain death.

Long-term recovery of PCB-contaminated sediments at the Lake Hartwell superfund site: PCB dechlorination. 1. End-member characterization.

Under anaerobic conditions, such as those typically found in buried sediments, the primary metabolic pathway for polychlorinated biphenyls (PCBs) is reductive dechlorination in which chlorine removal and substitution with hydrogen by bacteria result in a reduced organic compound with fewer chlorines. Vertical sediment cores were collected from Lake Hartwell (Pickens County, SC) and analyzed in 5-cm intervals for 107 PCB congeners in a total of more than 280 samples from 18 sediment cores and surface samples. This paper reports on extensive PCB dechlorination measured in Lake Hartwell sediments and the characterization of dechlorination end-member (EM) patterns using chemical forensic methods. PCB congener fingerprinting and a multivariate receptor modeling method, polytopic vector analysis (PVA), were used for identification and characterization of weathered and dechlorinated PCB congener patterns. Dechlorination resulted in a substantial shift in buried sediments from tetra- through decachlorobiphenyl congeners to mono- through trichlorobiphenyl congeners. Mono- through trichlorobiphenyls comprised approximately 80% of the PCBs in buried sediments that underwent maximum dechlorination as compared to approximately 20% in surface sediments. The major concentration decreases were seen in the tetra- through hexachlorobiphenyl homologues, which accounted for over 90% of the dechlorination. Octa- through decachlorobiphenyl congeners also were dechlorinated, but their overall contribution to dechlorination was relatively small due to their low initial concentrations (< 5%). The net accumulation of 2-CB, 2,2'/2,6-DCBs, 2,4'-DCB, 2,2',4-TCB, and 2,2',6-TCB at Lake Hartwell matched characteristic PCB dechlorination products reported in the literature, such as those for Processes M, Q, and C; and the persistence of tetrachlorobiphenyls (TeCBs) that contained 24- and 25-congener groups resembled dechlorination Processes H or H'. Although dechlorination tended to be very extensive in most of the cores, it was not always consistent from core to core or at various depth intervals within a single core. The reason for this variability in dechlorination extent could not be determined from the existing data and did not appear to correlate with such factors as PCB concentration, total organic carbon, or age. The authors used fingerprinting analysis and a PVA multivariate receptor model as exploratory data analysis tools to characterize PCB sources and their alteration patterns. Dominant sources and alteration patterns were determined in this large data set by comparing PVA EM patterns with known source patterns (i.e., Aroclors or Aroclor mixtures) and literature-reported alteration patterns. PVA also afforded an opportunity to characterize the vertical and lateral distributions of the weathered and unweathered PCB source patterns and dechlorination patterns, a task that would have been much more difficult to accomplish through comparison of chromatograms alone.

Long-term recovery of PCB-contaminated sediments at the Lake Hartwell superfund site: PCB dechlorination. 2. Rates and extent.

This paper reports on extensive polychlorinated biphenyl (PCB) dechlorination measured in Lake Hartwell (Pickens County, SC) sediments. Vertical sediment cores were collected from 18 locations in Lake Hartwell (Pickens County, SC) and analyzed in 5-cm increments for PCB congeners. The preferential loss of meta and para chlorines with sediment depth demonstrated that PCBs in the sediments underwent reductive dechlorination after burial. Notably, ortho chlorines were highly conserved for more than 5 decades; since the first appearance of PCBs, ca. 1950-1955. These dechlorination characteristics resulted in the accumulation of lower chlorinated congeners dominated by ortho chlorine substituents. Dechlorination rates were determined by plotting the numbers of meta plus para chlorines per biphenyl molecule (mol of chlorine/mol of PCB) with sediment age. Regression analyses showed linear correlations between meta plus para chlorine concentrations with time. The average dechlorination rate was 0.094 +/- 0.063 mol of Cl/mol of PCB/yr. The rates measured using the 2001 cores were approximately twice those measured using the 2000 cores, most likely because the 2001 cores were collected only at transects O, L, and I, which had the highest rates measured in 2000. An inverse of the dechlorination rates indicated that 16.4 +/- 11.6 yr was required per meta plus para chlorine removal (ranging from 4.3 to 43.5 yr per chlorine removal). The rates determined from this study were 1-2 orders of magnitude lower than rates reported from laboratory microcosm studies using Hudson River and St. Lawrence River sediments, suggesting that dechlorination rates reported for laboratory experiments are much higher than those occurring in situ.

EEG in convulsive and nonconvulsive status epilepticus.

Seizures and status epilepticus (SE) are serious complications in intensive care unit (ICU) patients. SE is often divided into convulsive and nonconvulsive types, based on clinical features. The EEG is helpful in further dividing SE into those that are generalized from onset, or have a partial onset, because this may be difficult to do clinically. This is particularly true in patients with tonic-clonic seizures, which may be generalized from onset, or secondarily generalized. Rarely in the ICU, although not infrequently in epilepsy monitoring units, the EEG may indicate that the event is nonepileptic, such as pseudostatus epilepticus. Nonconvulsive SE is often difficult to diagnose, be it partial or generalized, and the diagnosis is usually delayed. Furthermore, although an EEG is required to verify the diagnosis, there are not widely accepted criteria to diagnose this entity, particularly in obtunded/comatose patients. For example, it is controversial whether several EEG patterns, such as periodic lateralized and generalized periodic epileptiforms, are ictal or interictal. This article reviews EEG findings in different types of SE in adults and provides numerous examples.

Determination of sex hormones and nonylphenol ethoxylates in the aqueous matrixes of two pilot-scale municipal wastewater treatment plants.

Two analytical methods were developed and refined for the detection and quantitation of two groups of endocrine-disrupting chemicals (EDCs) in the liquid matrixes of two pilot-scale municipal wastewater treatment plants. The targeted compounds are seven sex hormones (estradiol, ethinylestradiol, estrone, estriol, testosterone, progesterone, and androstenedione), a group of nonionic surfactants (nonylphenol polyethoxylates), and their biodegradation byproducts nonylphenol and nonylphenol ethoxylates with one, two, and three ethoxylates. Solid phase extraction using C-18 for steroids and graphitized carbon black for the surfactants were used for extraction. HPLC-DAD and GC/MS were used for quantification. Each of the two 20 L/h pilot-scale plants consists of a primary settling tank followed by a three-stage aeration tank and final clarification. The primary and the waste-activated sludge are digested anaerobically in one plant and aerobically in the other. The pilot plants are fed with a complex synthetic wastewater spiked with the EDCs. Once steady state was reached, liquid samples were collected from four sampling points to obtain the profile for all EDCs along the treatment system. Complete removal from the aqueous phase was obtained for testosterone, androstenedione, and progesterone. Removals for nonylphenol polyethoxylates, estradiol, estrone, and ethinylestradiol from the aqueous phase exceeded 96%, 94%, 52%, and 50%, respectively. Levels of E3 in the liquid phase were low, and no clear conclusions could be drawn concerning its removal.

Long-term recovery of PCB-contaminated surface sediments at the Sangamo-westonl Twelvemile Creek/lake Hartwell Superfund Site.

Natural recovery of contaminated sediments relies on burial of contaminated sediments with increasingly clean sediments over time (i.e., natural capping). Natural capping reduces the risk of resuspension of contaminated surface sediments, and it reduces the potential for contaminant transport into the food chain by limiting bioturbation of contaminated surface or near-surface sediments. This study evaluated the natural recovery of surface sediments contaminated with polychlorinated biphenyls (PCBs) at the Sangamo-Weston/Twelvemile Creek/Lake Hartwell Superfund Site (Lake Hartwell), Pickens County, SC. The primary focus was on sediment recovery resulting from natural capping processes. Total PCB (t-PCB), lead-210 (210Pb), and cesium-137 (137Cs) sediment core profiles were used to establish vertical t-PCB concentration profiles, age date sediments, and determine surface sedimentation and surface sediment recovery rates in 18 cores collected along 10 transects. Four upgradient transects in the headwaters of Lake Hartwell were impacted by historical sediment releases from three upgradient sediment impoundments. These transects were characterized by silt/ clay and sand layering. The highest PCB concentrations were associated with silt/clay layers (1.8-3.5% total organic carbon (TOC)), while sand layers (0.05-0.32% TOC) contained much lower PCB concentrations. The historical sediment releases resulted in substantial burial of PCB-contaminated sediment in the vicinity of these four cores; each core contained less than 1 mg/kg t-PCBs in the surface sand layers. Cores collected from six downgradient Lake Hartwell transects consisted primarily of silt and clay (0.91-5.1% TOC) and were less noticeably impacted by the release of sand from the impoundments. Vertical t-PCB concentration profiles in these cores began with relatively low PCB concentrations at the sediment-water interface and increased in concentration with depth until maximum PCB concentrations were measured at approximately 30-60 cm below the sediment-water interface, ca. 1960-1980. Maximum t-PCB concentrations were followed by progressively decreasing concentrations with depth until the t-PCB concentrations approached the detection limit, where sediments were likely deposited before the onset of PCB use at the Sangamo-Weston plant. The sediments containing the maximum PCB concentrations are associated with the period of maximum PCB release into the watershed. Sedimentation rates averaged 2.1 +/- 1.5 g/(cm2 yr) for 12 of 18 cores collected. The 1994 Record of Decision cleanup requirement is 1.0 mg/kg; two more goals (0.4 and 0.05 mg/kg t-PCBs) also were identified. Average surface sedimentation requirements to meet the three goals were 1.4 +/- 3.7, 11 +/- 4.2, and 33 +/- 11 cm, respectively. Using the age dating results, the average recovery dates to meet these goals were 2000.6 +/- 2.7, 2007.4 +/- 3.5, and 2022.7 +/- 11 yr, respectively. (The 95% prediction limits for these values also are provided.) Despite the reduction in surface sediment PCB concentrations, PCB concentrations measured in largemouth bass and hybrid bass filets continue to exceed the 2.0 mg/kg FDA fish tolerance level.