Notes on <i>Alexandrium</i> population dynamics

Wyatt, Tim; Jenkinson, Ian R.

doi:10.1093/plankt/19.5.551

Cited by 120 publications

(66 citation statements)

References 46 publications

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“…Under such conditions, plankton populations are often not homogeneously distributed, but rather show a spatially structured distribution, for instance as patches or thin layers [2][3][4]72]. Flagellar movement may favour accumulation in patches [72], which is presumably also required for sexual reproduction in the life cycle of Alexandrium [17], as increased encounter rates in patches may allow Alexandrium gametes to find their corresponding mating type [73]. The fine-scale analysis of the spatial distribution of dinoflagellates in the water column indicates that they tend to accumulate.…”

Section: Discussionmentioning

confidence: 99%

Intraspecific facilitation by allelochemical mediated grazing protection within a toxigenic dinoflagellate population

et al. 2015

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Dinoflagellates are a major cause of harmful algal blooms (HABs), with consequences for coastal marine ecosystem functioning and services. Alexandrium fundyense (previously Alexandrium tamarense) is one of the most abundant and widespread toxigenic species in the temperate Northern and Southern Hemisphere and produces paralytic shellfish poisoning toxins as well as lytic allelochemical substances. These bioactive compounds may support the success of A. fundyense and its ability to form blooms. Here we investigate the impact of grazing on monoclonal and mixed set-ups of highly (Alex2) and moderately (Alex4) allelochemically active A. fundyense strains and a non-allelochemically active conspecific (Alex5) by the heterotrophic dinoflagellate Polykrikos kofoidii. While Alex4 and particularly Alex5 were strongly grazed by P. kofoidii when offered alone, both strains grew well in the mixed assemblages (Alex4 þ Alex5 and Alex2 þ Alex5). Hence, the allelochemical active strains facilitated growth of the non-active strain by protecting the population as a whole against grazing. Based on our results, we argue that facilitation among clonal lineages within a species may partly explain the high genotypic and phenotypic diversity of Alexandrium populations. Populations of Alexandrium may comprise multiple cooperative traits that act in concert with intraspecific facilitation, and hence promote the success of this notorious HAB species.

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Section: Discussionmentioning

confidence: 99%

Intraspecific facilitation by allelochemical mediated grazing protection within a toxigenic dinoflagellate population

et al. 2015

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“…The microscopic movements of individual cells in the field during a dinoflagellate bloom are unknown, but when cells are in salinity-stratified conditions similar to those that occur during a bloom, they are known to accumulate in the halocline (e.g. Wyatt & Jenkinson 1997, Smayda 2002. Durham et al (2009) describe a model for hydrodynamic trapping of motile microorganisms in layers.…”

Section: Discussionmentioning

confidence: 99%

Cell density-dependent swimming patterns of Alexandrium fundyense early stationary phase cells

Persson¹,

Smith²

2013

Aquat. Microb. Ecol.

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Different life-history stages of Alexandrium fundyense have different swimming behaviors and show different responses to water movement. Early stationary phase cells assemble in bioconvection patterns along the water surface and as stripes in the water, while cells in exponential growth do not. We studied the swimming behavior of early stationary phase A. fundyense cells, both on the individual level and on the population level. Cells assembled in spots in shallow Petri dishes, and were studied using an inverted microscope. We analyzed 53 videos of cells at different distances from the center of accumulated spots of cells with the program CellTrak for swimming behavior of individual cells. The closer the cells were to the center of spots, the faster they swam (> 600 µm s −1 in the center of spots compared to ca. 300 µm s −1 outside) and the more often they changed direction (>1400 degrees s −1 in the center compared to < 400 degrees s −1 outside). On a population level, the behavior of spots of assembled cells was studied using time-lapse photo graphy. The spots entrained more and more cells as they grew and fused with each other; the closer the spots came to each other, the faster they moved until they fused. We suggest that chemical attraction between gametes causes the observed behavior. KEY WORDS: Alexandrium fundyense · Swimming pattern · Stationary phase · Gamete · Cell density Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 68: [251][252][253][254][255][256][257][258] 2013 amounts that they cause an unstable density stratification that triggers instability in the form of descending plumes of cells (Kessler 1985, 1986, Pedley & Kessler 1992, Bees & Hill 1997, Hopkins & Fauci 2002, Nguyen-Quang et al. 2009). In such a plume, the fluid velocity is higher than the swimming velocity of individual cells -the collective behavior of cells has changed the density distribution in such a way that patterns are formed at a scale greater than individual cells. The underlying cause of the assemblage of cells is a tactic behavior of individual cells, being attracted to light, nutrients, oxygen, etc., or swimming upwards to avoid sinking (gravit axis). When geometry of cells, density distribution within cells, placement of flagella, etc. affects the swimming direction, the term used is gyrotaxis. Gyrotaxis is directional swimming due to a combination of upward swimming and rotational drag due to shear (e.g. Kessler 1985, Durham et al. 2009). Bioconvection patterns concentrate microorganisms into dense regions separated by regions with few organisms, which can facilitate mating (Wager 1911, Kessler 1986, Pedley & Kessler 1992.In many dinoflagellate species, including all that produce resting cysts, gametes are formed at the end of the growth season. Attraction between gametes is necessary, otherwise sexual fusion and production of resting cysts for survival during the winter would be impossible. The 'season cue' for gamete formation may be composed of many diff...

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“…Townsend et al 2001;Anderson et al 2005). Perhaps the organism's life history strategy, including a resting cyst stage, lends intrinsic stability to the population on interannual to interdecadal time periods (Wyatt and Jenkinson, 1997). Table 1 for depths sampled in each survey.…”

Section: Discussionmentioning

confidence: 99%

Interannual variability of Alexandrium fundyense abundance and shellfish toxicity in the Gulf of Maine

McGillicuddy

Anderson

Solow

et al. 2005

Deep Sea Research Part II: Topical Studies in Oceanography

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Six years of oceanographic surveys of Alexandrium fundyense concentrations in the Gulf of Maine are combined with shellfish toxicity records from coastal monitoring stations to assess covariations of these quantities on seasonal to interannual time scales. Annual mean gulf-wide cell abundance varies by less than one order of magnitude during the time interval examined (1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002). Fluctuations in gulf-wide annual mean cell abundance and shellfish toxicity are not related in a consistent manner. This suggests that interannual variations in toxicity may be regulated by transport and delivery of offshore cell populations, rather than the absolute abundance of the source populations themselves.2

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Notes on Alexandrium population dynamics

Cited by 120 publications

References 46 publications

Intraspecific facilitation by allelochemical mediated grazing protection within a toxigenic dinoflagellate population

Intraspecific facilitation by allelochemical mediated grazing protection within a toxigenic dinoflagellate population

Cell density-dependent swimming patterns of Alexandrium fundyense early stationary phase cells

Interannual variability of Alexandrium fundyense abundance and shellfish toxicity in the Gulf of Maine

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