Showing papers in "Virginia journal of science in 2002"

Autotrophic Picoplankton: Their Presence and Significance In Marine and Freshwater Ecosystems

Abstract: This Article is brought to you for free and open access by the Biological Sciences at ODU Digital Commons. It has been accepted for inclusion in Biological Sciences Faculty Publications by an authorized administrator of ODU Digital Commons. For more information, please contact digitalcommons@odu.edu. Repository Citation Marshall, Harold G., \"Autotrophic Picoplankton: Their Presence and Significance in Marine and Freshwater Ecosystems\" (2002). Biological Sciences Faculty Publications. Paper 91. http://digitalcommons.odu.edu/biology_fac_pubs/91

Identifying Sources of Fecal Pollution in the Roanoke River, Roanoke County, Virginia

Abstract: Antibiotic Resistance Patterns (ARPs) of Enterococcus spp. were used as a phenotypic fingerprint to compare and categorize unknown-source isolates in an impaired segment of the Roanoke River, Roanoke County, Virginia. Antibiotic resistance analysis (ARA) of enterococci has been effectively used to differentiate among sources of fecal contamination in many geographic regions in the United States. Enterococcus spp. were used as a fecal indicator in a library consisting of 1,562 known-source isolates. Two-way analysis indicated that approximately 95% of the unknown-source isolates collected were of animal origin. A 3-way analysis indicated that 61 % of the unknowns were of livestock origin while 34% were of wildlife origin. Of the isolates determined to be of wildlife origin, almost all were from raccoons and geese while enterococci from deer were present at low percentages. For one sample date, 20% of the isolates at one site were of human origin. This bacterial source tracking (BST) data will prove valuable for the development of TMDLs for this impaired waterway. INTRODUCTION To date 3,486 km of the 78,000 km of streams and rivers in Virginia are listed as impaired, with only one third being adequately monitored (FOR VA). The Roanoke River, used as a source of drinking water and recreation, originates in the mountains of Montgomery County, runs eastward through the highly populated areas of Roanoke County, Salem City, and Roanoke City, continues into North Carolina and empties into Albemarle Sound, North Carolina. In the Roanoke area, land usage is both agricultural, on which horses, cattle and other agriculturally important animals are present, as well as urban from which human indicator bacteria may originate. Large numbers of resident geese and ducks as well as other wildlife are also present. Of the 803 stream segments in Virginia that are listed as impaired waters, fecal indicator bacteria are the leading cause of the impairment (DEQ). In the next 10 years, Virginia must develop TMDLs (Total Maximum Daily Load) for 600 impaired segments (DEQ). Public watersheds can be restricted from human recreational use if they exceed the Environmental Protection Agency (EPA) standard of 126 Escherichia coli or 33 Enterococcus colony forming units (cfu) per 100 mL (geometric mean) in fresh water (EPA). Diseases caused by enteric pathogens potentially transmitted through contaminated water include cholera (Vibrio cholerae), gasteroenteritis (Escherichia coli) , giardiasis (Giardia) , salmonellosis and typhoid fever (Salmonella sp.), shigellosis (dysentery, Shigella sp.), and viruses, such as hepatitis A and Norwalk group viruses (Parveen et al., 1999; United States Environmental Protection Agency, 2001). 158 VIRGINIA JOURNAL OF SCIENCE With current water testing procedures, the presence of fecal indicator organisms indicate the presence of fecal material but not the source of the contamination. Transforming a non-point source into a point source is valuable in order to improve water quality, reduce the nutrient load leaving the watershed, and prevent possible transmission of disease (Hagedorn et al, 1999). Several methodologies have been implemented to determine human and non-human sources of contamination. While many methods exist, several have been used extensively and successf\\illy, or show promise. These methods include antibiotic resistance analysis (ARA; Wiggins; 1996; Hagedorn et al, 1999; Wiggins et al., 1999; Bowman et al., 2000; Harwood et al., 2000; Bower, 2001), ribotyping (Parveen et al, 1999; Hartel etal., 2000; Carson et al., 2001), pulsed-field gel electrophoresis (PFGE; Simmons, 2000), and utilization of specific carbon sources (Hagedorn, et al., in review). In the work presented here, Enterococci were used as a fecal indicator for our library of known-source isolates. While fecal coliforms are the standard indicator in Virginia, ARA using the enterococci has been highly successful (Hagedorn et al., 1999; Wiggins et al., 1999; Bower, 2000; Bowman et al., 2000; Harwood et al., 2000). Enterococci are an appropriate indicator in brackish and salt water primarily because they are more apt to survive in marine environments than fecal coliforrns because they can tolerate high (6 .5%) salt concentrations (Hagedorn et al, 1999). Enterococci also have a higher survival rate through wastewater treatment processes than fecal coli forms making them an attractive target in fresh water (Harwood et al., 2000). This provides the basis for using antibiotic resistance patterns (ARPs) as a \"phenotypic fingerprint\" to compare and categorize unknown Enterococcus spp. isolates. Although antibiotics are primarily used in humans and livestock, we find antibiotic resistance is widespread and common, even in wildlife such as Canada goose, white-tailed deer, muskrat, and raccoon. We report here that ARA of fecal enterococci from known fecal sources, used in conjunction with discriminate analysis (DA), effectively predicted the sources of isolates taken from four Roanoke river sample sites over three sample dates. We have reinforced the bacterial source tracking method and we report both the extent of fecal contamination in the Roanoke River on these dates and the source of fecal contamination. MATERIALS AND METHODS Bacterial Library Fresh fecal material, ranging from a swab to several grams, from known sources (horse, human, raccoon, sheep, chicken, cow, white-tailed deer, Canada goose, and muskrat), was diluted in sterile distilled water. Samples from humans are presumed to be a mixture of isolates from several individuals from a portable toilet or pump out truck. Multiple manure samples were collected and mixed, while goose isolates were from single individuals. Several horses were swabbed to obtain fecal material. One hundred L fecal suspension was pipetted onto each mEnterococcus agar (Difeo) plate and spread with a sterile glass hockey stick. Plates were inverted and incubated at 37C for 48h . Burgundy and pink colonies were picked off with sterile toothpicks and placed into 200μL enterococcosel broth (BBL) in sterile 96-well plates. Black wells (positive for Enterococcus spp.) were noted. A 48 prong replicaplater was used to transfer isolates onto Trypticase Soy Agar with lecithin and polysorbate 80 (BBL) Antibiotic Plates (Table 1). Antibiotic plates were inverted and incubated for 48h at 37C, and SOURCE TABLE 1. Antibiotics and Final Plate

Longevity Record for a Wild Allegheny Woodrat (Neotama magister) in West Virginia

Abstract: The Allegheny woodrat (Neotoma magister) is found throughout much of the central and southern Appalachians and adjacent portions of the Interior Highlands. Allegheny woodrats have declined in the northern portions of their range and are state-listed as threatened, endangered or sensitive species of concern in every state where they occur. Until recently, biologists have had to rely on biological data collected from the closely related eastern woodrat (N.jloridana) because oflimited research on the Allegheny woodrat. We have been studying the ecology and natural history ofwoodrats in Virginia and West Virginia since 1990. On 8 August 1997 we caught and ear-tagged a juvenile female woodrat. She was caught a total of 24 times in the same outcrop from 1997 through 2002. A conservative estimate of her age on 25 January 2002 was 1,734 days or 57.8 months. This extends the record longevity for a wild Allegheny woodrat by 70 days or 2.3 months. Regardless, her known time alive (from first capture to last) of 1,630 days still surpasses previous estimates of longevity for the Allegheny woodrat INTRODUCTION The Allegheny woodrat (Neotoma magister) is found throughout much of the central and southern Appalachians and adjacent portions of the Interior Highlands. It is widespread but uncommon in Virginia and West Virginia (Mengak, 1998). It is a habitat specialist closely associated with rock outcrops, cliffs, talus slopes, boulder fields and cave entrances. Allegheny woodrats are tolerant of a wide range of macrohabitats but select specific habitats based on microhabitat features (Castleberry et al., 2002b). The Allegheny woodrats' natural history and role in the local food web and in forest dynamics is unclear. Fungi and mast (hard and soft) are major components of the woodrats diet (Castleberry et al., 2002a) but it is not known what role wo.odrats play, if any, in the distribution of mycorrhizal fungi and forest regeneration. In this ecoregion, the rough and inaccessible areas inhabited by woodrats generally have not been subject to direct, large-scale disturbances from human activities such as logging, agriculture, or second-home development. The long-term effect of disturbances to Corresponding Author: (Phone) 706-583-8096, (E-mail) mmengak@smokey.forestry.uga.edu 168 VIRGINIA JOURNAL OF SCIENCE adjacent habitats on woodrat populations is unclear even as regional land use activities such as forest management and mining continue to increase in intensity. Natural history information on woodrats is needed to assess population status and recommend actions to ensure the long-term survival of this species. Allegheny woodrats have declined in the northern portions of their range and are state-listed as threatened, endangered or sensitive species of concern in every state where they occur (Beans, 1992; Laerm et al. , 2000; Castleberry et al., 2002a). Nonetheless, they still appear to be abundant in appropriate habitat ·in the central Appalachians of Kentucky, Virginia and West Virginia. Reasons for decline are unclear and are the subject of debate but likely include severe weather (Nawrot and Klimstra, 1976), increased avian and meso-mammal predation (Balcom and Yahner, 1996), reduced hard mast production brought about by the elimination of the American chestnut (Castanea dentata) and gypsy moth (Lymantria dispar) infestation in oak (Quercus spp.) forests (Hall , 1985), vegetation change from white-tailed deer (Odocoileus virginianus) herb ivory (Hassinger et al., 1996), raccoon roundworm (Baylis ascaris procyonis) parasitism (McGowan and Hicks, 1996) and habitat fragmentation (Balcom and Y ahner, 1996). Until recently, biologists have had to rely on biological data collected from the closely related eastern woodrat (N. jl.oridana) because of limited research on the Allegheny woodrat. However, numerous recent reports have addressed the ecology and natural history of the Allegheny woodrat including studies on landscape characteristics (Balcom and Yahner, 1996), population genetics (Castleberry et al., in review), effects of timber management ( Castleberry et al., 2001 ), summer microhabitat selection (Castleberry et al., 2002b), food habits (Castleberry et al., 2002a), ectoparasites (Castleberry et al. in review), reproduction and juvenile growth (Mengak, 2002), and longevity (Mengak, 1997; 2000). With this note, we extend the record for longevity in a wild Allegheny woodrat and comment on reproductive strategy. Previous records for longevity by a wild Allegheny woodrat were 1,468 days and 1,502 days (Mengak, 1997). An additional record for longevity was reported as 1,664 days (Mengak, 2000). Prior to the work by Mengak (1997; 2000) reported lifespans for Allegheny woodrats were up to 48 months in captivity (Poole, 1940). Other reports for the genus include 991 days for wild eastern woodrats (Fitch and Rainey, 1956), 67 months for captive desert woodrats (N. lepida; Landstrom, 1971) and 60 months for captive white-throated woodrats (N. albigula; Landstrom, 1971 ). A juvenile woodrat (#607) was first caught on 8 August 1997 on Mead-Westvaco Corporation's Wildlife and Ecosystem Research Forest (WERF) in Randolph County, West Virginia (38° 42'N, 80°3 'W). The WERF is a 3360 ha area reserved for the study of industrial forestry impacts on ecosystems and ecological processes in an Appalachian setting (Ford and Rodrigue, 2001 ). The WERF has been described in detail in previous reports (Castleberry et al., 2001; Castleberry et al. , 2002a; Castleberry et al., 2002b). Mengak (1997; 2000) described the capture and marking methods. She was caught in a large rock outcrop in the Rocky Run drainage at an elevation of 920 m. The 2.5-3 ha site's vegetation primarily was a small sawtimber-sized northern hardwood forest with an abundant rhododendron (Rhododendron maximum) and greenbrier (Smilax spp.) shrub layer. Her weight at initial capture was 150 g. She was caught a total of 24 times in the same outcrop from 1997 through 2002. At her most recent capture on 25 January 2002, she weighed 285 g. Assuming a birth weight of 17 g (Mengak 1997; 2000) and an average weight gain of 1.26 g/d (Mengak, 2002), her estimated birth date was 25 April 1997. Therefore, a conservative estimate of her age on 25 January 2002 was 1,734 days or 57 .8 months. This extends the record longevity LONGE'1 for a wild Allegheny woodrat b) alive (from first capture to las( longevity (Mengak 1997; 2000). Because we were conducti1 individual woodrat has contribut1 She was radio-tagged for three m study (Castleberry et al., 2001). a study of population genetic st were collected from her month! habits (Castleberry et al., 2002a: occasions (Castleberry et al., in 1999 and thus is presumed to ha The Allegheny woodrat is Appalachians. Information on r controversial (Mengak, 2002). long-term trends in capture data; rate (Mengak, 2002) and long pc is functioning more like a K-sele< be attributed to most small mam1 strategies designed to protect i Allegheny woodrats . We sugges rat population demographics w critical for formulating future m;

Chromium Tolerant Microbial Communities from the Chesapeake Bay Watershed

Abstract: Chromium tolerant bacteria were enumerated from portions of the Chesapeake Bay watershed and examined for their potential to reduce Cr(VI). Water and sediment samples were collected from various locations in Baltimore Harbor and Bear Creek, as well as Sandy Point State Park in Maryland and the Anacostia River in Washington, DC. Samples were spread onto agar plates with Cr042-(5 ppm) as the sole terminal electron acceptor. Plates were incubated anaerobically and colony forming units (CFU) enumerated. CFU arising on minimal-Cr042medium ranged from 10 -10 mC or f 1 and community estimates from sites in proximity to Baltimore City were approximately 6-30X higher than distal sites. Bacterial identification by BIO LOGTM or l 68 rRNA sequencing indicated the presence of bacteria of the genera Klebsiella, Pseudomonas, Burkholderia, Kluyvera and others. Typical Cr(VI) reduction rates by these isolates were significantly lower than Shewanella oneidensis, a known metal-reducing bacterium. Results suggested that microbial communities in the Chesapeake Bay watershed, particularly in Baltimore Harbor and Bear Creek, had a high tolerance for Cr(VI) and/or could grow slowly with Cr(VI) as a terminal electron acceptor. However, the isolates did not rapidly degrade Cr(VI) in the laboratory. INTRODUCTION The Chesapeake Bay is the largest estuary in the U.S. and is fed by a broad watershed that includes six states (New York, Pennsylvania, Delaware, Maryland, Virginia and West Virginia) and the District of Columbia, encompassing an area of approximately 12,000 km (Pritchard and Schubel, 2001). Forests, cultivated and abandoned agricultural land, wetlands and residential areas surround the Bay and its adjacent watershed. It is home to a wide range of aquatic wildlife and has regional economic importance in the fishery and shipping industries (Lippson and Lippson, 1997). In addition, the Chesapeake Bay is ·a popular site for recreational boaters and tourists. * To whom correspondence should be addressed. E-mail: jonesmee@cc(nrl.navy.mil; Telephone: (202)404-6361; Fax: (202)404-8515 142 VIRGINIA JOURNAL OF SCIENCE As a result of past and recent human activities, pollutants and other contaminants (i.e., pesticides, herbicides, organophosphates, polychlorinated biphenyls [PCBs], petroleum products and heavy metals) have accumulated in the Bay (Lynch, 2001). Pollutants reach the Bay through river drainage, runoff and direct discharge ( Curtin, 2001 ). One of the more problematic contaminants is chromium, which was mined north of the Bay in the 19th and 20th centuries. Chromium is an important industrial metal used in the manufacture of many diverse products, including ferrous and nonferrous alloys, paints, pigments, wood preservatives and corrosion inhibitors (Fendorf et al., 2000). Such manufacturing industries have operated in and around the Bay region during the past two centuries. Chromium is a redox active transition metal with a wide range of possible oxidation states, although, only two (+6 and +3) are stable in the environment. It is a widespread contaminant in the environment and is recognized as a toxic substance and carcinogen (Kimbrough et al., 1999). Cr(VI) is highly water soluble and is easily transported through aquatic environments. In contrast, Cr(III) is much less soluble and precipitates as a hydroxide above pH 5.5. Due to its lower solubility, Cr(III) is considered less toxic and is, in fact, a necessary micronutrient for humans and other animals (Hamilton and Wetterhahn, 1987). Chromium tolerance may occur by several potential mechanisms including plasmid-encoded resistance, transport mechanisms and reduction (Wang, 2000; Cervantes et al., 2001 ). Reduction of soluble (more toxic) Cr(VI) to less soluble (less toxic) Cr(III) is influenced by several factors ( e.g., pH, temperature 2 redox potential) and can be mediated by various chemical species (i.e., Fe(II), S ), some plants and several microorganisms (Fendorf et al., 2000; Lytle et al., 1998; Wang, 2000). A metal-reducing microorganism, Shewane/la oneidensis, has been shown in laboratory experiments to reduce Cr(VI) at high rates (Daulton et. al., 2001 ). Thus, one potential strategy for environmental Cr(VI) removal would be the addition of S. oneidensis into contaminated sites. However, it is not known at this time whether S. oneidensis can compete with native microflora at Cr(VI) contaminated sites. Therefore, a possible remediation plan would be to stimulate naturally-occurring Cr-tolerant and Cr(VI)-reducing bacteria (CRB) in contaminated environments by fertilization or other environmental manipulation. Alternatively, wastewater treatment schemes could be developed using naturally-occurring CRB in bioreactor systems. In situ, naturally-occurring CRB may have Cr(VI) reduction capabilities superior to those of S. oneidensis. To assess the feasibility of such bioremediation strategies, we evaluated the prevalence of Cr-tolerant and other bacterial communities in the Chesapeake Bay watershed, which includes regions previously shown to contain high levels of contaminants including chromium (Baker et. al., 199,7). Environmental isolates were identified and tested for their ability to reduce Cr(VI) in the laboratory.

A Baseline Assessment of Furbearers on the Upper Coastal Plain of Virginia

Abstract: We assessed the status of furbearing mammals on Fort A.P. Hill, Caroline County, Virginia during the 199 8-1999 trapping season with the cooperation of local licensed trappers. Our analyses were based on 345 captures representing of 10 mammal species, ranging from one bobcat (Lynx rufus) to 157 beavers (Castor canadensis). Mean number of captures per 100 trap nights was 17.0. Captures varied from 11.9 to 17.9 per 100 trap nights for conibear traps and 9.7 to 18.3 per 100 trap nights for leg-hold traps. External measurements of six species were similar to those reported for other populations in the region. We suggest that valuable insights into the ecology and trends of furbearer populations can be obtained from studies conducted on government installations such as Fort A. P. Hill. Management plans that include evaluations of infectious disease reservoirs and transmission and impacts of furbearers on wetlands, other wildlife, and human activities would aid in long-term evaluation of these mammals from ecosystem and health perspectives.

Reproduction of Black Drum, Pogonias cromis, from the Chesapeake Bay Region

Abstract: Ovaries of black drum, Pogonias cromis, collected fromthe Chesapeake Bay region in 1992, were used to describe reproductive strategy and fecundity. Histological examination showed that black drum spawn in the Chesapeake Bay region from April through early June. Distributions of oocyte diameter showed distinct oocyte-developmental groups indicating that Chesapeake Bay black drum are group-synchronous batch spawners. Female black drum are extremely fecund ranging from 414,000 to 3,736,000 hydrated oocytes (mean = 1,389,000) per batch with a spawning periodicity of 3.8 days. Estimates of spawning strategy, spawning periodicity, and batch fecundity for black drum from the Chesapeake Bay region were similar to reported estimates from the Gulf of Mexico. INTRODUCTION In U.S. waters, where the primary range for black drum, Pogonias cromis, in the Northwest Atlantic is from the Delaware .Bay south to Florida and through the Gulf of Mexico (Welsh and Breder, 1923; Hildebrand and Schroeder, 1928; Silverman, 1979), there are at least two known populations: one along the U.S. East Coast and one or more in the Gulf of Mexico (Gold et al. 1995; Jones and Wells 1998). Many essential elements of the reproductive life history are well understood for stocks in the Gulf of Mexico (Fitzhugh et al. , 1993; Nieland and Wilson, 1993; Saucier and Baltz, 1993; Fitzhugh and Beckman, 1987). Specifically, black drum fromthe Gulf of Mexico mature at five years, are group-synchronous spawners, with a batch fecundity of 1.4 to 1.6 million hydrated oocytes, and have a spawning periodicity of 3 4 days (Fitzhugh et al. , 1993; Nieland and Wilson, 1993). In contrast to the Gulf of Mexico black drum, littl~ is known about the reproductive biology of black drum along the U.S. East Coast. Studies of adult black drum in Eastern Florida and in the Chesapeake Bay have been limited to estimating the age at maturity and spawning season. Murphy and Taylor (1989) showed that the age at first maturity is five to six years and the spawning season along Northeast Florida is from January to May with peak spawning in March and April, while Alshuth and Gilmore ( 1995) found a more protracted spawning season from October to late March. In Virginia waters Bobko (1991) observed a spawning season of April through May, and noted that all fish were mature by age six. Although the length of the spawning season and age of maturity have been documented, spawning strategy has not been described nor batch fecundity estimated for black drum from along the U.S. East Coast. Estimates of batch fecundity are essential to understanding life-time reproductive output. However, this information is difficult to obtain because an age-specific migration pattern exists for this population. Although black drum of all ages are present E-mail : bkwellswork@cs.com

Reproductive Differences among Delmarva Grass Shrimp (Palaemonetes pugio and P. vulgaris) Populations

Abstract: Populations of female grass shrimps (Palaemonetes pugio and P. vulgaris) were sampled from five coastal embayments in Delaware, Maryland, and Virginia (Delmarva) and compared with respect to reproductive and life history attributes. We observed interspecific differences in timing ofreproduction, carapace length, ratio of carapace length to total body length, body weight, clutch weight, clutch size, and egg volume. Onset of reproduction in P. vulgaris lagged behind P. pugio. Although there was no difference in the relationship between clutch size and carapace length for the two species, carapace length/total body length in P. pugio was greater than that in P. vulgaris. A multivariate analysis of variance indicated significant differences in carapace length, clutch weight, body weight, clutch size, and egg volume attributable to effects of species, population, and interactions between them. At all sites, P. pugio produced larger eggs than P. vulgaris. Although the two species did not differ in reproductive effort, both species exhibited increases in reproductive effort with latitude. Clutch size also tended to increase with latitude for both species. In populations where both species were abundant, adult females of P. pugio were longer and heavier and produced heavier egg masses comprised of fewer, larger eggs. INTRODUCTION In a classic paper, Hutchinson (1961) raised the issue of how so many similar species are able to coexist in the plankton given the prediction, from the principle of competitive exclusion (Gause, 1934; Hardin, 1960), that one species should outcompete the others. Coexistence of similar species is exemplified by the "grass shrimps" Palaemonetes pugio Holthuis and Palaemonetes vulgaris (Say) that abound in marshes and bays of the Atlantic and Gulf coasts of North America. These two closely related species often co-occur in estuarine sites (Williams, 1984). Although both species exhibit similar distribution patterns across their geographic ranges, they exhibit differences in within-habitat usage. In previous studies, it has been shown that habitat partitioning in these species is a consequence of interspecific differences in physiological tplerances toward salinity (Thorp and Hoss, 1975; Knowlton and Kirby, 1984; Present address: Department of Entomology & Center for Population Biology, One Shields Avenue, University of California, Davis, CA 95616. 2 Corresponding author. 36 VIRGINIA JOURNAL OF SCIENCE Knowlton and Schoen, 1984; Khan et al., 1995, 1997) and dissolved oxygen (Welsh, 1975), substrate and cover preferences (Arguin et al., 1989; Knowlton et al., 1994; Khan et al., 1995, 1997), and interference competition (Thorp, 1976). In the present study, we examine whether differences in reproductive strategies could also promote resource partitioning between P. pugio and P. vulgaris and how these differences are maintained across a range of environmental conditions. There is some evidence to suggest that reproductive strategies differ between the two species. Chambers (I 982) and Yan (1987) found that Massachusetts populations of P. pugio exhibit greater mean clutch size than P. vulgaris with the same reproductive effort (ratio of gonadal weight to body weight). Although seasonal breeding periods of P. pugio and P. vulgar is are thought to be similar (Knowlton, 1970), Hoffman ( 1980) observed that Delaware populations of P. pugio produced three or more clutches while P. vulgaris produced no more than two clutches within a single season. Within a species, reproductive characteristics might be expected to vary according to season and geographic location due to differences in temperature, photoperiod, and salinity. Latitudinal clines in egg number have been observed in birds, fishes, and mammals such that clutch size increases with latitude (reviewed by Fleming and Gross, 1990). Such variation in clutch size may reflect differences in the growing season. Salinity may also influence clutch size in estuarine organisms. For example, Alon and Stancyk (1982) found that P. pugio fecundity increased with prolonged exposure to lower salinities. The purposes of this study were to explore the extent to which P. pugio and differ reproductively and to examine these differences across a range of environmental conditions. Accordingly, we compared reproductive attributes of P. pugio and P. vulgaris from five marine and estuarine sites in Chesapeake and "outer" (Atlantic) bays of Virginia, Maryland, and Delaware, spanning a substantial salinity gradient and a wide range of latitude. We examined the effects of species and population level variation on reproductive characteristics. To determine broader geographical patterns in reproductive strategies, we compared results of this study of Delmarva populations with studies from populations in other regions. METHODS Palaemonetes pugio and P. vulgaris populations were sampled during the breeding period (May, July, and September 1987) at five locations (Figure 1; see Knowlton et al., 1994 for details). Collecting locations were selected so that two pairs of Chesapeake and Atlantic sites occurred at similar latitudes and spanned a broad range of salinities. Values at Chesapeake sites ranged from about 12 ppt at Station 5 to about 25 ppt at Station 3 while those at both Atlantic sites (Stations 1 and 2) were about the same, averaging about 30 ppt (Figure 1, Appendix A). Collections at each site were timed to occur at roughly the same time of day and stage of tide (about two hours prior to low tide, Appendix A). Samples, obtained using long-handled D-frame dip nets, were preserved on site in 95% ethanol. At time of collection, salinity was measured with a hand-held refractometer, air and water temperatures with a pocket thermometer. Dissolved oxygen (mg/L) was determined using a modified Winkler method (Hach Chemical Co., 1977). In the laboratory, we used a dissecting microscope to separate species per sample according to criteria in Holthuis ( 1952). Sex was determined by noting the form of the SHRIMP REP: ,-----:1a1t,. 1.., .:1.... ':b. FIGURE 1. Locations of collection sit, Bay, Chincoteague, VA; 3 = Kings Cre( near Saxis, VA; and 5 = Mezick Pond, ~ SHRIMP REPRODUCTIVE DIFFERENCES 37

Environmental Factors Contributing to the Disaggregation of a Colonial Cyanoprokaryote and Its Influence on Picoplankton Abundance within Lake Joyce, Virginia

Abstract: A colonial cyanoprokaryote, Aphanocapsa holsatica and autotrophic picoplankton abundance were monitored weekly over a two year period in Lake Joyce, Virginia. Significant differences were observed in both the cyanoprokaryote and picoplankton abundance over the study period and an inverse relationship was observed between these two plankton groups. Disaggregation of colonies was shown to contribute to picoplankton populations where water temperature and precipitation input apparently trigger colony dispersion. This relationship is suggested to occur in other aquatic habitats. Results of this work and its implications for ecosystem dynamics are discussed. INTRODUCTION Picoplankton is defined as plankton between 0.2 and 2.0μm in size (Sieburth et al., 1978) and may include a variety of both heterotrophic and autotrophic organisms (Marshall, 2002). Numerous studies have shown picoplankton as an abundant and productive component within a variety of oceanic, estuarine and freshwater environments (Li, et al., 1983; Fahnensteil and Carrick, 1992; Marshall and Nesius, 1993; Affronti and Marshall, 1994). However, questions remain as to the relationship of picoplankton in aquatic food web dynamics (Stockner and Shortreed, 1989; Fogg, 1995; Marshall, 2002). To answer these questions, more detailed information is required on factors which influence picoplankton composition dynamics. With this information, a better understanding of the availability of picoplankton as a link or sink for nutrients can be determined. The objectives of this study are: 1) identify variation in both autotrophic picoplankton and colonial cyanoprokaryotic abundance using a high frequency sampling regime and 2) identify the effects, if any that water temperature and storm water runoff have on colonial cyanoprokaryotic and autotrophic picoplankton population dynamics in Lake Joyce, Virginia. Lake Joyce, Virginia (36° 54' 44\" Lat., 76° 7' 19\" Long.) is a 60ha freshwater lake whose overflow empties via Pleasure House Creek and the Lynnhaven River into the lower Chesapeake Bay. The Virginia Department of Environmental Quality ( 1994) has described this water body as an unstratified, hypereutrophic system whose average depth is 1.1 m. The major nonpoint source input is from urban storm water runoff. Lake Joyce is representative of other lakes in the Norfolk/Virginia Beach area where its general usage includes fishing, boating, and water skiing. METHODS During this study, three replicate surface grab samples (125 mL) were collected weekly at one station in Lake Joyce over a 24 month period (May 29, 2000 to May 20, 200 VIRGINIA JOURNAL OF SCIENCE Plcoplankton Abundance