JoAnn Burkholder - Academia.edu (original) (raw)

Papers by JoAnn Burkholder

Harmful Algae, 2008

This report represents the synopsis of a ''roundtable discussion'' on the links between water qua... more This report represents the synopsis of a ''roundtable discussion'' on the links between water quality and eutrophication and the occurrence of harmful algal blooms (HABs). This meeting,

Limnology and Oceanography, 2006

We used a decadal data set, with weekly to biweekly sampling in April—October and monthly samplin... more We used a decadal data set, with weekly to biweekly sampling in April—October and monthly sampling in November—March, to characterize climatic (hurricane‐level storms, a sustained 3‐yr drought) and anthropogenic influences on N and P concentrations and loadings to a large eutrophic, poorly flushed estuary, the Neuse Estuary of the Albemarle—Pamlico Estuarine System. Mass volume transport data were obtained with cross‐estuary transect flow measurements taken near the entrance to the estuary. Although trends were minimally influenced by hurricanes, analyses were significantly affected by the sustained drought near the end of the study. As examples, decreasing trends in total N (TN), total P (TP), and bottom‐water dissolved oxygen concentrations, and in TN loadings were significant considering all data, but these trends were not significant when the sustained drought was excluded from analysis. In addition, the trend in TN loading was especially sensitive to the initial sampling period...

Applied and Environmental Microbiology, 1990

We report a direct comparison of phosphate uptake by adnate and loosely attached microalgae in an... more We report a direct comparison of phosphate uptake by adnate and loosely attached microalgae in an intact biofilm matrix, with resolution at the level of individual cells. Track scanning electron microscope autoradiography enabled assay of [ 33 P]phosphate uptake from the overlying water by adnate algae left undisturbed on mature leaves of the macrophyte Potamogeton illinoensis or on artificial plant mimics. The epiphyte communities developed in either phosphate-poor or moderately phosphate-enriched water, and they were assayed on both natural and artificial plants. All adnate taxa examined from both natural and artificial plants in both habitats took up significantly less radiolabel when assayed beneath the overlying matrix than when they were exposed to the water upon removal of the overstory material. Track scanning electron microscope autoradiography and track light microscope autoradiography were intercalibrated to enable comparison of [ 33 P]phosphate uptake by adnate and loose...

Environmental Science and Pollution Research, 2018

Anthropogenic inputs of chemical environmental contaminants are frequently associated with develo... more Anthropogenic inputs of chemical environmental contaminants are frequently associated with developing harmful algal blooms, but little is known about how estuarine phytoplankton assemblages respond to multiple, co-occurring chemical stressors in chronically disturbed habitats. The goals of this research were to establish a robust protocol for testing the effects of atrazine on estuarine phytoplankton, and then to use that protocol to compare the effects of atrazine exposure with and without nutrient enrichment on a cosmopolitan estuarine/marine alga, Dunaliella tertiolecta (Chlorophyta). Atrazine sensitivity in nutrient-replete media (96-h growth inhibition x) was 159.16 μg l −1 , but sensitivity was influenced by exposure duration, and inhibitory effects of herbicide on algal growth decreased under imbalanced nutrient regimes and low nitrogen and phosphorus supplies. These findings advance knowledge about how nutrient regimes and herbicides interact to control estuarine phytoplankton population dynamics.

Journal of Phycology, 2019

Pleurocapsales are one of the least understood groups of cyanobacteria in terms of molecular syst... more Pleurocapsales are one of the least understood groups of cyanobacteria in terms of molecular systematics and biochemistry. Considering the high number of cryptic taxa within the Synechococcales and Oscillatoriales, it is likely that such taxa also occur in the Pleurocapsales. The new genus described in our research is the first known pleurocapsalean cryptic taxon. It produces off‐flavor and a large number of bioactive metabolites (n = 38) some of which can be toxic including four known microcystins. Using a polyphasic approach, we propose the establishment of the genus Odorella with the new species O. benthonica from material originally isolated from the California Aqueduct near Los Angeles.

The Quarterly Review of Biology, 2016

Archiv Fur Hydrobiologie Supplementband Monographische Beitrage, 1989

Oecologia, 1992

We began this experiment to test specific hypotheses regarding direct and indirect effects of fis... more We began this experiment to test specific hypotheses regarding direct and indirect effects of fish predation on the littoral macroinvertebrate community of Bays Mountain Lake, Tennessee. We used 24 m2 enclosures in which we manipulated the presence and absence of large redear sunfish (Lepomis microlophus&amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;150 mm SL), and small sunfish (L. macrochirus and L. microlophus &amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;50 mm SL) over a

This module addresses the complex interface of research and the media; this interface necessarily... more This module addresses the complex interface of research and the media; this interface necessarily involves issues of public policy, however, for the purposes of this module we will focus on media issues and touch on public policy in the Thinking Outside the Box section. For simplicity, when we refer to “media” we are speaking of journalists covering the science beat. In the Introduction we talk about the special collaboration between the media and the researcher and the challenges both face in communicating science to the public at large. We note the ethical component inherent in all communication and include quotations from various experts as to the difficulty of reporting research clearly; the role of rhetoric in discussing science is touched upon. In the Central Essay portion, Dr. JoAnn Burkholder talks about her experiences when dealing with the media and conducting her research in the glare of the public eye. Using specific situations in her work with Pfiesteria as an example, ...

Oceanography, 2005

Cultural eutrophication, the pollution of coastal waters by nutrients, is a result of population ... more Cultural eutrophication, the pollution of coastal waters by nutrients, is a result of population growth, food production (agriculture, animal operations and aquaculture), and energy production and consumption, and is considered one of the largest pollution problems globally (Howarth et al., 2002). Population growth and food production result in major changes to the landscape, in turn, increasing sewage discharges and runoff from agriculture and populated lands. In addition to population growth, eutrophication arises from the large increases in the use of chemical fertilizers that began in the 1950s and which are projected to continue to escalate in the coming decades (Smil, 2001). Both nitrogen and phosphorus are of concern in eutrophication, but nitrogen has received far more attention because it often limits primary production in estuaries and coastal waters and because the global application of nitrogen from synthetic fertilizers is far greater than that of phosphorus (more information available at www.ut.ee/~olli/eutr/). Although cultural eutrophication is occurring globally, nutrient export is not evenly distributed (Seitzinger et al., 2002a).

Limnology and Oceanography, 1990

Chemical speciation of chromium in sea water. Part 2. Effects of manganese oxides and reducible o... more Chemical speciation of chromium in sea water. Part 2. Effects of manganese oxides and reducible organic materials on the redox processes of chromium. Anal. Chim. Acta 130: 401-404.- ,-, H. KOKORO, AND T. FUJINAGA. 198 1 d. Chemical speciation of chromium in sea water. Part 1. Effect of naturally occurring organic materials on the complex formation of chromium(IIT). Anal. Chim. Acta 130: 289-294.

Limnology and Oceanography, 1992

... Many un-armored cells with diameter > 15 lim were observed with peduncles or nets; occasio... more ... Many un-armored cells with diameter > 15 lim were observed with peduncles or nets; occasion-ally cells were found with both extensions. ... (APH), Elakatothrix gelatinosa (ELAK), and unar-mored gymnodinoid dinoflagellates (GYM) is desig-nated on the basis of cell number (A ...

Journal of Phycology, 1995

The community structure and productivity of epiphytic microalgae on field populations of eelgrass... more The community structure and productivity of epiphytic microalgae on field populations of eelgrass (Zostera marina L.) from a high flow regime were characterized under water‐column nitrate enrichment over a 30–d period during the autumn growing season for the macrophyte. Epiphyte communities in replicate low‐nitrogen sites (LOW‐N, median water‐column nitrate concentrations below detection) were compared to communities in replicate N‐enriched sites wherein nitrate was leached from clay pots filled with enriched agar (N‐ENRICH, median concentration ca. 6 μM NO3−‐N; pots replaced at 8– to 12–d intervals). In experimental chambers, total epiphyte community productivity as 14C‐bicarbonate uptake was determined from short‐term (3–h) laboratory assays. Track light microscope‐autoradiography enabled estimates of species‐specific productivity for abundant algal taxa. After 6 d in the LOW‐N and N‐ENRICH communities, the crustose adnate red alga Sahlingia subintegra (Rosenvinge) Kornmann was dominant in terms of cell number and codominant in biovolume. Photosynthetic dinoflagellates, not previously reported as abundant in eelgrass epiphyte communities, were dominant in biovolume contribution after both 6 and 30 d in LOW‐N communities. Nitrate enrichment stimulated the adnate monoraphid diatom Cocconeis placentula Ehr. but apparently inhibited dinoflagellates and the diatom Melosira sp. Total productivity of the epiphyte communities remained comparable in both the LOW‐N and N‐ENRICH sites. Shifts in community structure and species‐specific productivity, however, indicated a controlling influence of nitrate supply on microalgal epiphytes in the field eelgrass community.

Journal of Phycology, 1989

... so ned io forth« horriogrin/e ifie material and lo sep .11.111 small Otiti 1ец blue green alg... more ... so ned io forth« horriogrin/e ifie material and lo sep .11.111 small Otiti 1ец blue green algar) Itom or цаш« arni i ai ,ie dehris Cefo Wen settled ... il / ..ninnimi foul weekM, »uh aunair tpiphyWI Siali-bar - NQ um; (D) ihr lonsek atta, hrd rommunill ol ihr 4inr ainlii i.il Irai s. ale bar - SO ...

Journal of Phycology, 1986

In the first two .iummen, a dense riparian canopy reduced the light penetration nt the stream sur... more In the first two .iummen, a dense riparian canopy reduced the light penetration nt the stream surface to a range of 5 to 18% of incident radiation. Thf lotic inacroalgnf community-during this period was limited to 1 to 4 species coirring < I to 55^c of the stream bottom. Howex'er, in June and July, 1981, the surrounding leaf canopy was removed h\ a massive gyp.s\ moth larval outbreak. Light penetration to the stream during this summer increased to 737c by early July, thereby resulting in a rise in water temperatures by 3.7*'C. Even though there was a partial regrowth of leaves in late July and August of 1981, macroalgal cover values continued to rise to an early August peak of 80%. During the third summer, 88% of the macroalgal abundance could be attributed to illumination and water temperature. The filamentous diatom F.unotia prctinalis (O.F. Miill.) Rabh. teas the predominant species in the midsummer of all four years, accounting for at least 60% of the total cover. In 1981. an important taxon was the desmid Hyalotheca dissilicns (5. Smith) Breb., a species which was not seen in other years. A less sei'ere gyps\ moth defoliation occurred in 1982 but did not produce significant differences in light, temperature or macroalgal cover from 1979and 1980. Theresults indicate that light and temperature can be limiting during the summer in springfed, headwater streams and that seed populations of some species are present in unrletectable lex'els during these periods of suboptimal growth conditions, in addition, it appears that stream macroalgal communities can be quiie re.silient, recovering rapidly follou*ing a major perturbation.

Journal of Phycology, 1984

Suspended and benthic algal communities from a mildly acidic, third‐order Rhode Island stream wer... more Suspended and benthic algal communities from a mildly acidic, third‐order Rhode Island stream were examined to determine the seasonal distribution, abundance and diversity of the lotic desmids. Within a one‐year sampling period, 148 species and 202 subspecific taxa of desmids were identified, representing 23 genera. Species of Cosmarium and Closterium accounted for approximately 70% of the desmids present, and were the most diverse and abundant taxa during all seasons except spring, when Hyalotheca dissiliens was the dominant desmid species. Average abundance and species richness generally were greatest during summer for both suspended and benthic desmids. Most desmids occurred in benthic habitats, and were randomly distributed among substrata. Average seasonal abundance was 7.4 × 104 cells·g−1 dry wt substratum, among 13 types of substrata. Highest desmid abundance was measured among substrata with intricate morphologies, such as Fontinalis spp., which was associated with 1.2 × 106 desmid cells·g−1 dry wt substratum, or 1.7 × 103 cells·cm−2 substratum. Cell division was observed for 70 desmid taxa, and average seasonal reproduction (based on cell numbers) among all substrata ranged from 4% in winter to 20% during summer. In addition, sexually produced zygospores were found occasionally for H. dissiliens. Desmids were distributed among most substrata examined in this stream, with abundance comparable to reported estimates from softwater lakes and acid bogs. In contrast to established dogma, lotic desmids are not incidental drift organisms, but rather comprise a viable and persistent component of the stream periphyton.

Journal of Experimental Marine Biology and Ecology, 1994

In experimental mesocosms the community structure, total community productivity, and speciesspeci... more In experimental mesocosms the community structure, total community productivity, and speciesspecific productivity of loosely attached epiphytic microalgae were compared across a gradient of water-column nitrate enrichment during the fall season of high microalgal growth. Eelgrass (&stem marina L.) and its epiphytes were maintained for 6 wk under low water exchange (109, day-') to simulate conditions in poorly flushed lagoons and upper embayments, in control (ambient nitrate at < 1 PM NO; N) and treated mesocosms (enriched with pulsed daily watercolumn additions to 3.5 PM and 7.0 PM NO, N, respectively, for low [LOW] and moderate [MOD] treatments). In experimental chambers productivity was estimated as 14C-bicarbonate uptake for the total epiphyte community from liquid scintillation counts, and for abundant microalgal species using track light microscope-autoradiography. After 3 wk MOD nitrate enrichment stimulated total epiphyte community productivity, mostly as blue-green algae, whereas LOW enrichment was insufficient to cause a stimulatory effect. After 6 wk, however, community productivity was enhanced in both LOW and MOD enrichment, mostly contributed by small diatoms such as Nitzschia closterium (biovolume 70-560 pm3). At the population level, the response of larger diatom taxa such as Nitzschiu longissima and Bacillaria parudoxa (biovolume > 3000 pm3) varied depending on the degree of nitrate enrichment. The data indicate a controlling influence of nitrate supply on community structure and species dominance of the microalgal epiphytes.

Journal of Environment Quality, 1997

During July 1995, a poultry waste lagoon ruptured in Duplin County, North Carolina, sending 32.6 ... more During July 1995, a poultry waste lagoon ruptured in Duplin County, North Carolina, sending 32.6 million L of chicken waste effluent into a nearby creek and the Northeast Cape Fear River. In August 1995 a breach of a hog waste lagoon released approximately 7.6 million L of waste into a system of blackwater creeks in Brunswick County, North Carolina. The poultry waste spill occurred under high rainfall-high river flow conditions, while the swine waste lagoon spill occurred during dry conditions. Both spills caused high turbidity and low dissolved oxygen (DO) in receiving waters, and DO levels in the Northeast Cape Fear River displayed a "sag curve" 10 d after the poultry waste spill, reaching a minimum of 1.0 mg L-1 90 km downstream. Both spills delivered high N loads to receiving waters (maxima of 92.1 mg L-~ from the poultry spill and 47.0 mg L-1 from the swine waste spill). Phosphorous concentrations reached 6.0 and 11.5 mg L-1 in receiving waters of the poultry and swine waste spills, respectively. Dense phytoplankton blooms (>100 p~g chlorophyll a L l) were measured in the blackwater creeks after the swine spill. High fecal coliform concentrations were delivered by both spills, and concentrations of the pathogenic bacterium Ciostridium perfringens ranged up to 40 000 colony-forming units (CFU) mL inthereceiving wate rs afte r the poultry spill. In 1995 and 1996 more than 30 animal waste lagoon breaches, overtoppings, and inundations were reported in North Carolina, demonstrating the major pollution potential of these treatment systems. N ORTH CAROLINA is one of the largest swine and poultry-producing states in the USA (Barker and Zublena, 1995). As of 1 June 1997, the state hosted total of 9.8 million head of swine (NCDA, 1996), and the poultry industry currently consists of approximately 60 million turkeys and 680 million chickens (NCDA, 1997). The large swine population has demonstrated most of its growth in the past several years. Swine and poultry wastes are highly-concentrated sources of organic and inorganic nutrients, fecal coliforms, and other pathogenic microorganisms, and chemical oxygen demand (Westerman et al., 1990; Sobsey, 1996). In addition, bioassays have shown that poultry litter leachate can be more toxic to test organisms than other farm animal manures (Gupta and Kelly, 1992). Waste from concentrated animal operations (particularly swine and poultry) are commonly discharged into waste-holding lagoons to receive some anaerobic digestion before being sprayed onto fields (Westerman et al., 1990; Huffman and Westerman, 1995). In North Carolina, many of these operations are concentrated in the coastal plain region, particularly in the southeast portion of the state

Hydrobiologia, 1985

... Phormidium incrustatum and Schizothrix calcicola (Blum, 1959 ; Pentecost, 1982) were not foun... more ... Phormidium incrustatum and Schizothrix calcicola (Blum, 1959 ; Pentecost, 1982) were not found, further substantiating the fact that Rhode Island streams ... ions (Patrick & Rei-mer, 1966; Cholnoky 1968; Sreenivasa & Duthie, 1973 ; Eloranta & Kunnas, 1979 ; van Dam et al ...