Physiological and behavioral diagnostics of nitrogen limitation for the toxic dinoflagellate Alexandrium fundyense

Poulton, Nicole

doi:10.1575/1912/3519

Cited by 8 publications

(10 citation statements)

References 74 publications

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“…This was coincident with an increase in the relative percentage of both GTX1, 4, and GTX6. In a review of past work on toxin composition changes, decreases in C1, 2 and increases in GTX1, 4 were observed in response to nitrogen limitation for A. fundyense (Anderson et al 1990a), although these trends were not always consistent between isolates (Poulton 2001).…”

Section: Discussionmentioning

confidence: 99%

“…These cruises occurred during the yearly spring bloom of this species. Although the IMBS technique has not previously been used in the field, it has been extensively tested on cultures and culture-spiked field samples (Aguilera et al 1996(Aguilera et al , 2002Poulton 2001). Furthermore, in culture experiments measures of protein concentration and other physiological parameters were not significantly different in untreated controls versus IMBS treatments (Poulton 2001;Aguilera et al 2002).…”

Section: Discussionmentioning

confidence: 99%

“…Past studies of A. fundyense dynamics in the Gulf of Maine during 1993, and 1998(Martorano 1997Poulton 2001;Townsend et al 2001) often identified A. fundyense populations in low DIN surface water, with DIN : DIP well below Redfield ratios (Redfield 1958), particularly in the later stages of the bloom. These studies suggest that nitrogen physiology may be important to the dynamics of A. fundyense populations in this environment.…”

Section: Discussionmentioning

confidence: 99%

“…There is considerable interest in the environmental factors that affect the growth of this genus in field populations. For example, A. fundyense populations in the western Gulf of Maine are often found in surface waters where inorganic nitrogen concentrations are low (Ͻ2 mol L Ϫ1 ) to undetectable, particularly in the late spring (Martorano 1997;Poulton 2001). In this system it is unclear whether A. fun-1 Corresponding author (sdyhrman@whoi.edu).…”

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confidence: 99%

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Urease activity in cultures and field populations of the toxic dinoflagellate Alexandrium

Dyhrman

Anderson

2003

Limnology & Oceanography

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Nitrogen availability is an important factor controlling phytoplankton abundance and species composition in marine waters. In addition to inorganic nitrogen, some phytoplankton species can use dissolved organic nitrogen sources such as urea for growth. Herein we demonstrate that axenic laboratory cultures of the toxic dinoflagellate, Alexandrium fundyense strain CB301A and A. catenella strain TN9A were able to grow on urea as a sole nitrogen source in the presence of nickel. This nickel dependence suggests that these Alexandrium species hydrolyze urea into ammonia with the enzyme urease rather than adenosine triphosphate urea amidolyase. Cells grown on urea had lower toxin content (15%-30%) than f/2-grown cells. In A. fundyense the urease enzyme appears to be nitrogenregulated. In culture experiments, enzyme activity was highest in nitrate-starved and urea-grown (replete) cells, whereas activity was undetectable in f/2-grown (replete) and phosphate-starved cells. Urease activity in ammoniagrown (replete) cells was also depressed. Urease activity also appeared to increase with decreasing nitrate-limited growth rate in semicontinuous cultures. May and June cruises in the Gulf of Maine followed the yearly bloom of A. fundyense. On average, inorganic nitrogen concentrations in May were higher than in June, whereas cell abundances, urea concentrations, and urease activity in May were lower than in June. The latter measurements relied on an immunomagnetic bead separation to isolate living A. fundyense cells from mixed phytoplankton samples for analysis. The differences between May and June suggest that urea may be important for Alexandrium nutrition as inorganic nitrogen concentrations in surface water decline.Harmful algal blooms cause serious public health and economic impacts on a global scale (Hallegraeff 1993;Anderson et al. 2000). For example, species within the marine dinoflagellate genus Alexandrium are responsible for paralytic shellfish poisoning (PSP) along the coastlines of the United States, Canada, and many other countries (Hallegraeff 1993;Anderson 1997). PSP can result in serious illness or death if humans ingest sufficient shellfish contaminated with the dinoflagellate toxins (Van Dolah 2000). Observations of Alexandrium fundyense and PSP outbreaks in the northeastern United States indicate that populations accumulate in a variety of oceanographic habitats (Anderson 1997). There is considerable interest in the environmental factors that affect the growth of this genus in field populations. For example, A. fundyense populations in the western Gulf of Maine are often found in surface waters where inorganic nitrogen concentrations are low (Ͻ2 mol L Ϫ1 ) to undetectable, particularly in the late spring (Martorano 1997;Poulton 2001). In this system it is unclear whether A. fun-1 Corresponding author (sdyhrman@whoi.edu). AcknowledgmentsWe thank Dave Kulis, Jody Donahue, Mike Lomas, Bruce Keafer, Liz Jablonski, and Dave Townsend for technical assistance and sample processing. Special thanks also go t...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Urease activity in cultures and field populations of the toxic dinoflagellate Alexandrium

Dyhrman

Anderson

2003

Limnology & Oceanography

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“…A potentially more serious shortcoming of this simple formulation is the lack of vertical migration behavior that could allow A. fundyense to exploit nutrients present in subsurface layers (MacIntyre et al, 1997). However, recent evidence suggests that the capability for vertical migration is not universal amongst all strains of A. fundyense from the Gulf of Maine (Poulton, 2001). Moreover, the importance of this behavior has yet to be demonstrated unequivocally in natural populations of A. fundyense in the gulf (Martin et al, submitted; Townsend et al, submitted-a).…”

Section: Circulation Modelmentioning

confidence: 99%

Mechanisms regulating large-scale seasonal fluctuations in Alexandrium fundyense populations in the Gulf of Maine: Results from a physical–biological model

McGillicuddy

Anderson

Lynch

et al. 2005

Deep Sea Research Part II: Topical Studies in Oceanography

150

132

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Observations of Alexandrium fundyense in the Gulf of Maine indicate several salient characteristics of the vegetative cell distributions: patterns of abundance are gulf-wide in geographic scope; their main features occur in association with the Maine Coastal Current; and the center of mass of the distribution shifts upstream from west to east during the growing season from April to August. The mechanisms underlying these aspects are investigated using coupled physical-biological simulations that represent the population dynamics of A. fundyense within the seasonal mean flow. A model that includes germination, growth, mortality, and nutrient limitation is qualitatively consistent with the observations. Germination from resting cysts appears to be a key aspect of the population dynamics that confines the cell distribution near the coastal margin, as simulations based on a uniform initial inoculum of vegetative cells across the Gulf of Maine produces blooms that are broader in geographic extent than is observed. In general, cells germinated from the major cyst beds (in the Bay of Fundy and near Penobscot and Casco Bays) are advected in the alongshore direction from east to west in the coastal current. Growth of the vegetative cells is limited primarily by temperature from April through June throughout the gulf, whereas nutrient limitation occurs in July and August in the western gulf. Thus the seasonal shift in the center of mass of cells from west to east can be explained by changing growth conditions: growth is more rapid in the western gulf early in the season due to warmer temperatures, whereas growth is more rapid in the eastern gulf later in the season due to severe nutrient limitation in the western gulf during that time period. A simple model of encystment based on nutrient limitation predicts deposition of new cysts in the vicinity of the observed cyst bed offshore of Casco and Penobscot Bays, suggesting a pathway of re-seeding the bed from cells advected downstream in the coastal current. A retentive gyre at the mouth of the Bay of Fundy tends to favor re-seeding that cyst bed from local populations.

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Identification and enumeration of Alexandrium spp. from the Gulf of Maine using molecular probes

Anderson

Kulis

Keafer

et al. 2005

Deep Sea Research Part II: Topical Studies in Oceanography

127

101

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Physiological and behavioral diagnostics of nitrogen limitation for the toxic dinoflagellate Alexandrium fundyense

Cited by 8 publications

References 74 publications

Urease activity in cultures and field populations of the toxic dinoflagellate Alexandrium

Urease activity in cultures and field populations of the toxic dinoflagellate Alexandrium

Mechanisms regulating large-scale seasonal fluctuations in Alexandrium fundyense populations in the Gulf of Maine: Results from a physical–biological model

Identification and enumeration of Alexandrium spp. from the Gulf of Maine using molecular probes

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