Eric B. May

Tumor prevalence and biomarkers of exposure and response in brown bullhead (Ameiurus nebulosus) from the Anacostia River, Washington, DC and Tuckahoe River, Maryland, USA

We evaluated liver and skin tumor prevalence and biomarkers of exposure and response in brown bullhead (Ameiurus nebulosus) from three locations in the Anacostia River (Washington, DC, USA), a Chesapeake Bay region of concern. The Tuckahoe River (Maryland, USA) served as a reference. Each river was sampled in fall 2000 and spring 2001. In the Anacostia, prevalence of liver tumors was 50 to 68%, and prevalence of skin tumors was 13 to 23% in large (> or = 260 mm, age > or = 3 years) bullheads. Liver and skin tumor prevalence was 10 to 17% and 0%, respectively, in small (150-225 mm, age 1-2 years) bullheads. Tuckahoe bullhead liver tumor prevalence was 0 to 3% (large) and 0% (small); none had skin tumors. Biliary polynuclear aromatic hydrocarbon (PAH)-like fluorescent metabolites and liver DNA adduct concentrations were elevated in large and small Anacostia bullheads. Mean adduct concentrations were 16 to 28 times higher than those in Tuckahoe fish. Chromatograms revealed a diagonal radioactive zone, indicating polycyclic aromatic compound (PAC)-DNA adducts. The biomarker data and the 10 to 17% liver tumor prevalence at ages 1 to 2 suggest that these year classes are likely to have a high prevalence as they reach age 3 and older. This study provides the strongest evidence to date of the role of PAHs in tumor development in Anacostia bullheads.

Spatial and Temporal Patterns in the Diet of Striped Bass in Chesapeake Bay

Abstract We collected striped bass Morone saxatilis from 1998 to 2001 (n = 2,703) and compared the seasonal feeding patterns of four size-groups (small [150-300 mm total length], medium [301-500 mm], large [501-700 mm], and extra large [>700 mm]) among three general regions (upper, middle, and lower) in Chesapeake Bay. Invertebrates dominated the diet of small striped bass during spring in all regions, and by fall bay anchovy Anchoa mitchilli became the dominant prey in the middle and lower regions. Pelagic schooling fishes were the primary prey for the larger size-groups. For medium striped bass, bay anchovy accounted for most of the prey eaten during spring and represented more than 50% of the diet by weight in summer in the upper and lower regions. Collectively, Atlantic menhaden Brevoortia tyrannus and bay anchovy accounted for more than 60% of the diet by weight in the lower region. Gizzard shad Dorosoma cepedianum and Atlantic menhaden were the dominant prey for medium and large fish from summer thr...

Environmental Variability Affects Distributions of Coastal Fish Species (Maryland)

Abstract We determined how environmental variability affected distributions of seasonally recruiting fishes (i.e., transient species) in coastal lagoons of Maryland from May–October during 1996, 1997, and 1999. A total of 241 monthly sampling events were conducted in the coastal lagoons at 40 sampling stations. Fluctuations in salinity resulting from variation in stream discharge were negatively correlated with intra-annual stability of fish assemblages. Transient, or non-resident species (e.g., recruiting species), were more frequent in habitats where salinity was less variable. When stream discharge lessened during dry years, transient species were more common throughout the coastal lagoons. Thus, environmental variability influenced distributions of young-of-year fishes in coastal estuaries.

Relationships Between Fish Assemblage Structure and Selected Environmental Factors in Maryland's Coastal Bays

Abstract We surveyed little-known ray-finned fish assemblages from Marylands coastal bays in order to establish species-habitat relationships for common species. From 1996–1999, 25 sites were sampled monthly with otter trawls in the coastal bays of Maryland. Anchoa mitchilli (bay anchovy) constituted nearly 50% of the catch for each year, and species composition was largely similar across years, with some differences likely related to variation in recruitment. For example, Clupea harengus (Atlantic herring) was particularly abundant during 1996 and 1999 following their spawning season. We used canonical correspondence analysis to determine how assemblages were related to temperature, dissolved oxygen (DO), salinity, and land-use variables during summer (June–September) and throughout the rest of the year. A gradient correlated with temperature and DO significantly structured assemblages throughout most of the year; during summer, the proportion of wetland habitat was important. We demonstrate that environmental gradients important for structuring fish assemblages differ between summer and non-summer months and there is a general shift in habitat use during summer from the lower estuary to other areas of the coastal bays. Our data also provide support for earlier observations that temperature was the major factor influencing changes in fish assemblage structure in the coastal bays. Our results point to better characterization of fish habitats in order to effectively manage coastal ecosystems of Maryland.

Spatial and temporal differences of Atlantic menhaden (Brevoortia tyrannus) recruitment across major drainages (1966–2004) of the Chesapeake Bay watershed

Atlantic menhaden (Brevoortia tyrannus) is well known for its commercial and ecological importance and has been historically declining in the Chesapeake Bay (Maryland), one of its principal nursery habitats along the eastern coast. Using data from the Striped Bass Seine Survey of the Maryland Department of Natural Resources (2003), we evaluated how the distribution of Atlantic menhaden has changed from 1966 to 2004 for 12 river drainages. We observed significant or marginally significant declines in 42% of the drainages, with drainages of the northern Bay showing the majority of those declines. Continued recruitment to several drainages of the Bay may partly explain why the adult spawning population is not declining. We determined if temporal changes in abundance were related to changes in salinity or water quality for five major drainages of the watershed. For one of these drainages, the Patuxent River, differences in productivity across sites largely explained differences in abundance. For the four remaining drainages, differences in recruitment could not be explained by productivity or salinity gradients. While reducing nitrogen loading and enhancing water clarity may improve Atlantic menhaden production, we suggest that the role of offshore processes on large-scale declines has been largely neglected and studies on larval ingression are necessary for further elucidation of spatial and temporal patterns of juvenile distribution in the Chesapeake Bay.

A protocol for conducting rainfall simulation to study soil runoff.

Rainfall is a driving force for the transport of environmental contaminants from agricultural soils to surficial water bodies via surface runoff. The objective of this study was to characterize the effects of antecedent soil moisture content on the fate and transport of surface applied commercial urea, a common form of nitrogen (N) fertilizer, following a rainfall event that occurs within 24 hr after fertilizer application. Although urea is assumed to be readily hydrolyzed to ammonium and therefore not often available for transport, recent studies suggest that urea can be transported from agricultural soils to coastal waters where it is implicated in harmful algal blooms. A rainfall simulator was used to apply a consistent rate of uniform rainfall across packed soil boxes that had been prewetted to different soil moisture contents. By controlling rainfall and soil physical characteristics, the effects of antecedent soil moisture on urea loss were isolated. Wetter soils exhibited shorter time from rainfall initiation to runoff initiation, greater total volume of runoff, higher urea concentrations in runoff, and greater mass loadings of urea in runoff. These results also demonstrate the importance of controlling for antecedent soil moisture content in studies designed to isolate other variables, such as soil physical or chemical characteristics, slope, soil cover, management, or rainfall characteristics. Because rainfall simulators are designed to deliver raindrops of similar size and velocity as natural rainfall, studies conducted under a standardized protocol can yield valuable data that, in turn, can be used to develop models for predicting the fate and transport of pollutants in runoff.

Transport of dissolved trace elements in surface runoff and leachate from a Coastal Plain soil after poultry litter application

The application of poultry (Gallus gallus domesticus) litter to agricultural soils may exacerbate losses of trace elements in runoff water, an emerging concern to water quality. We evaluated trace elements (arsenic [As], mercury [Hg], selenium [Se], and zinc [Zn]) in surface runoff and leachate from an agricultural soil with and without poultry litter application. Litter from a commercial operation was applied by three methods—broadcast application, subsurface placement, and broadcast application followed by disking—to no-till soils with a history of receiving litter. Soil monolith lysimeters (61 by 61 by 61 cm)(24 by 24 by 24 in) were extracted from each of the treatments and subjected to rainfall simulation (1 hour, 61 mm h−1 [2.4 in hr−1]) 15 and 42 days after litter application. Broadcasting poultry litter significantly increased concentrations (mg L−1) and loads (g ha−1) of As and Zn in runoff during the first event relative to other application methods. Notably, incorporating litter, either by disking after broadcasting or by subsurface placement, lowered As and Zn in runoff to near background levels by the second event, and there were no significant differences in As and Zn between any of the treatments. While Hg and Se were detected in runoff, they likely derived from edaphic sources as they were not detected in the litter nor did they differ significantly between treatments. Results point to poultry litter as a temporary source of some trace elements to runoff. This source can be readily controlled by adjusting application method.

Short-term infection of striped bass Morone saxatilis with Mycobacterium marinum.

Striped bass Morone saxatilis were studied in order to characterize their immune responses over the short term following challenge with Mycobacterium marinum. The expression of immunity-related genes (IL-1beta, TNF-alpha, Nramp and TGF-beta) quickly increased following infection with M. marinum, but these genes were subsequently down-regulated despite the fact that bacterial counts remained high. The number of monocytes and neutrophils also initially increased at 1 d postinfection. This confirms the importance of these types of cells in initial inflammation and mycobacterial infection in striped bass. The phagocytic index of splenic leukocytes over these same time frames did not change significantly following infection. The discrete window in which inflammatory mechanisms were stimulated in striped bass may be related to the intracellular nature of this pathogen.

Historical presence (1975-1985) of mycobacteriosis in Chesapeake Bay striped bass Morone saxatilis.

A retrospective analysis of archived tissue blocks has revealed that mycobacteriosis was apparent in Chesapeake Bay striped bass as early as 1984. Of 37 cases available from the years 1975 to 1985, 2 fish were found positive based on histopathology and genus-specific PCR. Multi-gene sequencing places the bacteria from the 2 positive cases (1984 and 1985) within the Mycobacterium tuberculosis clade with closest resemblance to the recently described fish pathogen M. pseudoshottsii. Our data confirms that mycobacteriosis is not a new disease of Chesapeake Bay striped bass and underscores the value of archived tissues in epidemiological examinations.

Urea Release by Intermittently Saturated Sediments from a Coastal Agricultural Landscape

Urea-N is linked to harmful algal blooms in lakes and estuaries, and urea-N-based fertilizers have been implicated as a source. However, the export of urea-N-based fertilizers appears unlikely, as high concentrations of urea-N are most commonly found in surface waters outside periods of fertilization. To evaluate possible autochthonous production of urea-N, we monitored urea-N released from drainage ditch sediments using mesocosms. Sediments from a cleaned (recently dredged) drainage ditch, uncleaned ditch, forested ditch, riparian wetland, and an autoclaved sand control were isolated in mesocosms and flooded for 72 h to quantify urea-N, NH-N, and NO-N in the floodwater. Sediments were flooded with different N-amended solutions (distilled HO, 1.5 mg L NH-N, 3.0 mg L NH-N, 2.6 mg L NO-N, or 5.1 mg L NO-N) and incubated at three water temperatures (16, 21, and 27°C). Urea-N concentrations in mesocosms representing uncleaned and cleaned drainage ditches were significantly greater than nonagricultural sediments and controls. While flooding sediments with N-enriched solution had no clear effect on urea-N, warmer (27°C) temperatures resulted in significantly higher urea-N. Data collected from field ditches that were flooded by a summer rainstorm showed increases in urea-N that mirrored the mesocosm experiment. We postulate that concentrations of urea-N in ditches that greatly exceed environmental thresholds are mediated by biological production in sediments and release to stagnant surface water. Storm-driven urea-N export from ditches could elevate the risk of harmful algal blooms downstream in receiving waters despite the dilution effect.