Phytoplankton potential growth rate versus increase in cell numbers: estimation of cell lysis

Garcés, Esther; Masó, Mercedes

doi:10.3354/meps212297

Cited by 19 publications

(13 citation statements)

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“…Efforts to model HAB dynamics are important in order to predict the location and timing of HAB events. However, the required data on the key biological processes in bloom dynamics, such as vegetative growth and loss rates due to mortality, are almost non-existent during natural bloom conditions (Garcés & Masó 2001). Studies reporting in situ specific growth rates during major dinoflagellate proliferations (Chang & Carpenter 1988, Reguera et al 1996 are more abundant than studies of mortality rates (Agusti et al 1998, Agusti & Duarte 2000.…”

Section: Introductionmentioning

confidence: 99%

Taxon-specific analysis of growth and mortality rates of harmful dinoflagellates during bloom conditions

Garcés¹,

Vila²,

Masó³

et al. 2005

Mar. Ecol. Prog. Ser.

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Growth and mortality rates of natural single Alexandrium spp. cells were measured by the Landry-Hassett dilution technique during different phases of blooms. Taxon-specific experiments were conducted between May and October 2002 during 3 intense blooms of A. taylori and A. catenella at different locations of the Mediterranean Sea. In addition, dilution experiments using chlorophyll a as a proxy for total phytoplankton biomass were used to estimate daily rates of net growth and mortality of the total phytoplankton community. A. taylori growth rates ranged from 0.04 to 0. . Growth rates of Gymnodinium sp., an accompanying dinoflagellate species during the A. taylori bloom studied, were similar to those measured for A. taylori, whereas their mortality rates (-0.58 to -0.82 d ) were measured during the decline phase of 2 A taylori blooms. At the decline of the blooms, A. taylori and A. catenella showed considerable mortality, but microzooplankton grazing was not confirmed to be the main cause of the bloom termination. In general, growth was not limited by nutrients in the experiments. There were a few cases of a potential nutrient limitation in these areas and, in general, blooms were not conditioned by nutrients. When changes in biomass (chlorophyll a) were measured, non-linearity of data due to saturation was observed. The interpretation of these results required a split-function model. Saturated grazing (G s ) was 28.9 µg chl a l -1 d -1, during which the saturating phytoplankton population represented a chl a concentration of 16 µg l -1 (P s ). KEY WORDS: Dilution technique · Growth rate · Mortality rate · Dinoflagellates · HAB · Alexandrium · GymnodiniumResale or republication not permitted without written consent of the publisher

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Section: Introductionmentioning

confidence: 99%

Taxon-specific analysis of growth and mortality rates of harmful dinoflagellates during bloom conditions

Garcés¹,

Vila²,

Masó³

et al. 2005

Mar. Ecol. Prog. Ser.

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“…Potential growth is often greater than observed net growth, and differences between the two are attributed to cell losses (Garcés & Masó 2001). Net changes in population density result from the balance between gains (growth and physical accumulation) and losses (grazing, mortality and physical dispersion).…”

Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

“…In this way, integrated values of μ (μ int ) rather than values of μ at specific depths (μ z ) are obtained; however estimates of μ max , i.e. the maximum value of μ in a given scenario, are unobtainable.Potential growth is often greater than observed net growth, and differences between the two are attributed to cell losses (Garcés & Masó 2001). Net changes in population density result from the balance between gains (growth and physical accumulation) and losses (grazing, mortality and physical dispersion).…”

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confidence: 99%

Vertical distribution of division rates in coastal dinoflagellate Dinophysis spp. populations: implications for modelling

Velo‐Suárez¹,

Reguera²,

Garcés³

et al. 2009

Mar. Ecol. Prog. Ser.

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This study explores vertical heterogeneities of in situ division rates (μ) of 3 species of Dinophysis and discusses its implications in modelling the population dynamics of these species. Based on a post-mitotic index approach, estimates of μ from vertical net-haul (integrated) samples (μ int ) were compared with those from a single depth (oceanographic bottle samples) (μ z ) at the cell maximum during 2 daily cell cycle studies in the Galician Rías Baixas (NW Spain). Additionally, vertical profiles of μ z were obtained during a field survey in Ría de Vigo. A 2-fold difference was observed between estimates of μ z from the cell maxima and μ int from integrated samples under stratified conditions. Differences were much larger when the minimum estimates of μ values from different depths (μ min ) were compared within single vertical profiles. An exponential growth model was applied to simulate the dynamics of a D. acuminata population during a daily cycle in June 1994. Results show that actively dividing cells of a target species may be restricted to narrow layers of the water column. Estimates of μ at different relevant depths during cell cycle studies may be key to determining whether if increased numbers of a target species are due to in situ growth or to the balance of imports and exports.KEY WORDS: Dinophysis spp. · Cell cycle · In situ division rate · Mitotic index · Cell maximum · Modelling approach Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 385: [87][88][89][90][91][92][93][94][95][96] 2009 and place, will be observed at its optimum depth in the water column, i.e. the depth where the combination of environmental conditions (resources and physicalbiological interactions) are the most suitable for that species' growth and survival.Dinophysis spp. and other toxin-producing algae (TPA) species that transmit toxins through the food web -even at moderate to low concentrations (10 2 to 10 3 cells l -1) -often constitute a small percentage of the total phytoplankton community. Bulk measurements using chemical indicators such as chlorophyll a concentration and primary production are unsuitable for growth studies of these rare TPA species since they reflect the physiology not of the target organisms but of the whole plankton community. Estimates of μ from in situ cell cycle studies are time-consuming, but provide realistic information on the division capabilities of the species in question (Reguera et al. 2003).Estimates of μ in field populations of Dinophysis spp. have been obtained either from incubations, on deck or in diffusion chambers (Garcés et al. 1997) or from direct in situ high frequency sampling with a mitotic index approach (Table 1). Dinophysis spp. often exhibit sharp heterogeneities in their vertical distribution (reviewed in , Velo-Suárez et al. 2008. To minimize sampling uncertainties derived from low cell concentrations, vertical migration or patchiness (which would result in samples with inadequate numbers of target cells), in situ ...

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“…with their horns/morphology yielding a high surface to volume ratio; elongated diatoms were also distinct to this group. Both have relatively low growth rates (Garcés and Masó 2001) and can be considered K-strategists. The remainder of the diatoms fall into two different groups according to the season.…”

Section: Functional Groups and Hab Speciesmentioning

confidence: 99%

Phytoplankton functional groups and harmful algae species in anthropogenically impacted waters of the NW Mediterranean Sea

Vila¹,

Masó²

2005

Sci. Mar.

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SUMMARY: Phytoplankton assemblages were analysed by multivariate analysis techniques in highly modified waterbodies (harbours) of the northwestern Mediterranean Sea over an annual cycle. The phytoplankton functional groups that characterise these anthropogenically impacted waters were identified and related to HAB events. Four functional groups can be distinguished from the analysis: (1) bloom-forming dinoflagellates, (2) winter diatoms, (3) summer-autumn diatoms, and (4) large dinoflagellates and elongated diatoms. The species that characterise these functional groups occurred at all sampling stations. Potentially harmful species are distributed through all the clusters. However, bloom-forming dinoflagellates occur particularly in large harbours and during summer months. The results indicate that: (1) functional groups indicate where and when there is a high risk of blooms, but they cannot determine the risk of a toxic or fish-killing event; and (2) large harbours in tideless seas must be considered as areas with a high risk of high-biomass bloom occurrences.Key words: phytoplankton assemblages, functional groups, toxic dinoflagellates, Mediterranean Sea, HAB. RESUMEN: GRUPOS FUNCIONALES DE FITOPLÁNCTON Y ESPECIES TÓXICAS O NOCIVAS EN AGUAS DEL MEDITERRANEO NORDOC-CIDENTAL IMPACTADAS ANTRÓPICAMENTE. -Se presentan los resultados de un analisis multivariante de asociaciones fitoplanctónicas en aguas confinadas (puertos) del Mediterráneo nordoccidental a lo largo de un ciclo anual. El objetivo del estudio es identificar los grupos funcionales de fitopláncton que caracterizan aguas impactadas por efectos antrópicos y determinar su relación con las incidencias de especies tóxicas o nocivas (HAB). Se han identificado cuatro grupos funcionales: (1) dinoflageados formadores de proliferaciones, (2) diatomeas de invierno, (3) diatomeas de verano-otoño, y (4) dinoflagelados y diatomeas de gran tamaño. En todas las estaciones muestreadas se detectan las especies que caracterizan los cuatro grupos funcionales. Sin embargo, los dinoflageados formadores de proliferaciones aparecen principalmente en puertos grandes y durante los meses de verano. Los resultados indican que: (1) Los grupos funcionales indican donde y cuando hay riesgo de proliferaciones, pero no pueden determinar el riesgo de un determinado evento tóxico. Y (2) los puertos grandes situados en mares con escasa amplitud mareal deben considerarse con un elevado riesgo de proliferaciones de elevada biomasa.

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Phytoplankton potential growth rate versus increase in cell numbers: estimation of cell lysis

Cited by 19 publications

References 19 publications

Taxon-specific analysis of growth and mortality rates of harmful dinoflagellates during bloom conditions

Taxon-specific analysis of growth and mortality rates of harmful dinoflagellates during bloom conditions

Vertical distribution of division rates in coastal dinoflagellate Dinophysis spp. populations: implications for modelling

Phytoplankton functional groups and harmful algae species in anthropogenically impacted waters of the NW Mediterranean Sea

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