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Journal ArticleDOI

Predicting marine phytoplankton community size structure from empirical relationships with remotely sensed variables

TL;DR: In this article, the authors describe relationships between the environment and the size composition of phytoplankton communities, using a collation of empirical measurements of size composition from sites that include polar, tropical and upwelling environments.
Abstract: The size composition of primary producers has a potential influence on the length of marine food chains and carbon sinking rates, thus on the proportion of primary production (PP) that is removed from the upper layers and available to higher trophic levels. While total rates of PP are widely reported, it is also necessary to account for the size composition of primary producers when developing food web models that predict consumer biomass and production. Empirical measurement of size composition over large space and time scales is not feasible, so one approach is to predict size composition from environmental variables that are measured and reported on relevant scales. Here, we describe relationships between the environment and the size composition of phytoplankton communities, using a collation of empirical measurements of size composition from sites that include polar, tropical and upwelling environments. The size composition of the phytoplankton communities can be predicted using two remotely sensed variables, chlorophyll-a concentration and sea surface temperature. Applying such relationships in combination allows prediction of the slope and location of phytoplankton size spectra and estimation of the percentage of different sized phytoplankton groups in communities.

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Citations
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Journal ArticleDOI
TL;DR: Kocum et al. as mentioned in this paper investigated microscale spatial variation in phytoplankton size structure at two coastal stations having different nutrient environments and found a significantly higher contribution of larger cells and diminishing abundance of picoplankton under increasing nutrient concentrations.
Abstract: Kocum, E. and Sutcu, A., 2014. Analysis of variations in phytoplankton community size-structure along a coastal trophic gradient. The phytoplankton community size structure is a significant factor in the ecological and biogeochemical functioning of marine ecosystems. Various environmental factors, including nutrients, can cause variations in the size structure of phytoplankton community, ultimately determining the potential for downward carbon transport and productivity in marine ecosystems. In the present study, microscale spatial variation in phytoplankton size structure was investigated at two coastal stations having different nutrient environments. The variation in phytoplankton size structure was characterized by a significantly (p < 0.05) higher contribution of larger cells and diminishing abundance of picoplankton under increasing nutrient concentrations observed at both sites, although at different threshold unfractionated phytoplankton chlorophyll a biomass levels. The average percent co...

10 citations

Journal ArticleDOI
TL;DR: The results indicate that the ratio of the grazing mortality of the large size category to that of the small size category best explains the variation of NBSS slopes across environments, suggesting that higher grazing deaths of large microphytoplankton may release the small phytoplANKton from grazing, which in turn leads to a steeperNBSS slope.
Abstract: Allometric scaling of body size versus growth rate and mortality has been suggested to be a universal macroecological pattern, as described by the metabolic theory of ecology (MTE). However, whether such scaling generally holds in natural assemblages remains debated. Here, we test the hypothesis that the size-specific growth rate and grazing mortality scale with the body size with an exponent of −1/4 after temperature correction, as MTE predicts. To do so, we couple a dilution experiment with the FlowCAM imaging system to obtain size-specific growth rates and grazing mortality of natural microphytoplankton assemblages in the East China Sea. This novel approach allows us to achieve highly resolved size-specific measurements that would be very difficult to obtain in traditional size-fractionated measurements using filters. Our results do not support the MTE prediction. On average, the size-specific growth rates and grazing mortality scale almost isometrically with body size (with scaling exponent ∼0.1). However, this finding contains high uncertainty, as the size-scaling exponent varies substantially among assemblages. The fact that size-scaling exponent varies among assemblages prompts us to further investigate how the variation of size-specific growth rate and grazing mortality can interact to determine the microphytoplankton size structure, described by normalized biomass size spectrum (NBSS), among assemblages. We test whether the variation of microphytoplankton NBSS slopes is determined by (1) differential grazing mortality of small versus large individuals, (2) differential growth rate of small versus large individuals, or (3) combinations of these scenarios. Our results indicate that the ratio of the grazing mortality of the large size category to that of the small size category best explains the variation of NBSS slopes across environments, suggesting that higher grazing mortality of large microphytoplankton may release the small phytoplankton from grazing, which in turn leads to a steeper NBSS slope. This study contributes to understanding the relative importance of bottom-up versus top-down control in shaping microphytoplankton size structure.

9 citations


Cites methods from "Predicting marine phytoplankton com..."

  • ...For the correlation analysis, considering the strong correlation between the growth rate and grazing mortality (Barnes et al., 2011; Chen et al., 2009; Landry et al., 2000; Murrell et al., 2002), we used univariate linear models instead of stepwise selection to avoid the issue of colinearity....

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Journal ArticleDOI
01 Jul 2017
TL;DR: The data suggest seasonal and spatial variability in the composition of midwater forage communities exploited by A. ferox across the NPSG, and demonstrate that sustained monitoring of diet could provide valuable insights into long-term changes in these understudied communities.
Abstract: We examined the diet of a common midwater predator, the longnose lancetfish ( Alepisaurus ferox , n=1371), with respect to fork length, season, and capture location within the North Pacific Subtropical Gyre (NPSG). While A. ferox fed diversely across 97 prey families, approximately 70% of its diet by wet weight consisted of seven prey families (fishes: Sternoptychidae, Anoplogastridae, Omosudidae, Alepisauridae; hyperiid amphipods: Phrosinidae; octopods: Amphitretidae; polychaetes: Alciopidae). Altogether, these micronekton prey families constitute a poorly known forage community distinct from those exploited by other pelagic predators and poorly sampled by conventional methods. We demonstrate ontogenetic variation in diet between two size classes of A. ferox ( A. ferox consumed more fish and octopods, fewer crustaceans, and were more cannibalistic than small A. ferox . Ontogenetic shifts in vertical foraging habitat were observed as the consumption of larger and more mesopelagic prey with increasing fork length. Spatial and seasonal variation in the diet of A. ferox is consistent with expected patterns of variation in prey distribution with respect to oceanographic features of the NPSG. Within both size classes, the diets of specimens collected from the oligotrophic core of the NPSG were more diverse than those collected near the boundaries of the gyre and appeared to track seasonal variation in the position of the northern boundary of the gyre. Our data suggest seasonal and spatial variability in the composition of midwater forage communities exploited by A. ferox across the NPSG, and demonstrate that sustained monitoring of diet could provide valuable insights into long-term changes in these understudied communities.

9 citations

Dissertation
30 Aug 2011
TL;DR: It is shown how models with diffusive growth stabilise the observed power-law steady state in marine systems, and stability is explicitly linked to parameters involved in feeding, in a model derived from a stochastic process.
Abstract: Aquatic ecosystems are observed to follow regular patterns in abundance. The frequency distribution of all individuals across the spectrum of body mass, irrespective of their taxonomic identity (known as a ’size spectrum’), follows a power law and this has mathematically been explained by the processes of growth and mortality primarily driven by predation. In this theory of the size spectrum, predation is driven by body size: as organisms grow bigger the size of their prey also increases. This process is thought to be particularly important for marine organisms such as fish, where individual body size is an important determinant for what they eat because they are mostly limited by the size of their mouths. Models need to capture the behaviour of real systems if reliable predictions are to emerge from them. Here, new equations for size-based predation are derived from a stochastic process, allowing variability in organism growth. The new equations are postulated to capture real feeding behaviour better than classical models often used to simulate size spectra. Marine systems are often perturbed by seasonal processes, environmental factors and exploitation. I show how models with diffusive growth stabilise the observed power-law steady state in marine systems, and stability is explicitly linked to parameters involved in feeding. Seasonal plankton blooms are introduced into the model, along with time-dependent reproduction, both of which are widely observed in aquatic systems. The population dynamics, along with growth and survival rates during blooms are investigated, and preliminary results are reflected in empirical data. The match/mismatch hypothesis is tested, with theoretical findings in agreement with observed seasonal trends. Adding factors such as these will make the behaviour of size-based models more indicative of real ecosystems, and thus well-informed management decisions about exploitation can be made.

7 citations


Cites background or methods from "Predicting marine phytoplankton com..."

  • ...The power-law steady state in aquatic communities appears to be ubiquitous, repeatedly observed at different scales, seasons and locations globally (see e.g. Sheldon et al., 1972; Boudreau and Dickie, 1992; San Martin et al., 2006; Barnes et al., 2011)....

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  • ...…size classes (Sheldon et al., 1972); this pattern has been observed over different size ranges, from phytoplankton (San Martin et al., 2006; HueteOrtega et al., 2010; Barnes et al., 2011) up to large fish species (Boudreau and Dickie, 1992; Jennings and Mackinson, 2003; Jennings et al., 2007)....

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  • ...The slope of the size spectrum is observed to be close to -1 (Jennings and Mackinson, 2003; Huete-Ortega et al., 2010; Barnes et al., 2011), indicating that there are equivalent amounts of biomass in logarithmically increasing weight brackets....

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  • ..., 1972); this pattern has been observed over different size ranges, from phytoplankton (San Martin et al., 2006; HueteOrtega et al., 2010; Barnes et al., 2011) up to large fish species (Boudreau and Dickie,...

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  • ...In more recent studies water samples have been collected and analysed using inverted microscopy to count individuals (e.g. Irigoien et al., 2005; Cermeño et al., 2006; Wang et al., 2006; Barnes et al., 2011)....

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Dissertation
30 Nov 2017
TL;DR: In this article, the authors present mesures de production primaire (PP) for the ecosystem of the estuaires of the Seine, in which le phytoplancton and le microphytobenthos sont les principalaux contributeurs.
Abstract: Les estuaires, de par leur position strategique a l'interface entre les eaux continentales et les eaux marines jouent un role ecologique de premiere importance et sont le siege de nombreuses activites humaines. L’estuaire de Seine est caracteristique des grands estuaires anthropises. Le management a long terme de ces ecosystemes soumis a des pressions croissantes reside notamment en une meilleure connaissance de la dynamique spatiale et temporelle des reseaux trophiques estuariens. Le phytoplancton et le microphytobenthos sont les principaux contributeurs de la production primaire (PP) dans ces ecosystemes et sont a la base des reseaux trophiques. Ces compartiments sont souvent reduits a la teneur en chlorophylle du milieu et leur productivite n’a jamais ete mesuree a l’echelle de l’estuaire de Seine. L’objectif de ces travaux a ete d’estimer la PP de ces compartiments le long du gradient halin. Afin d’acceder a des mesures a une haute resolution spatiale, des mesures de fluorescence modulee (PAM) a haute frequence ont ete couplees a des mesures d’incorporation de carbone (13C) a basse frequence. Les mesures de production primaire ont ete mises en perspective avec la dynamique des parametres physico-chimiques du milieu et la structure communautes phytoplanctoniques determines par differentes techniques (microscopie, cytometrie, biologie moleculaire). La dynamique du carbone excrete sous forme de TEP (Transparent Exopolymeric Particules) et EPS (Exopolymeric substances) a egalement ete etudiee pour chacun des compartiments. Au-dela des methodologies innovantes mises en place qui montre l’interet des mesures a haute frequence dans ces ecosystemes tres dynamiques, ce travail apporte une nouvelle vision de la dynamique du phytoplancton et de la richesse specifique du microbiome estuarien et apporte une estimation fiable de la production primaire.

6 citations


Cites background from "Predicting marine phytoplankton com..."

  • ...prédominant dans les propriétés de transfert de cette matière vers les niveaux trophiques supérieurs (Barnes et al. 2011)....

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  • ...La taille des particules (microalgues, débris de macroalgues) va également jouer un rôle prédominant dans les propriétés de transfert de cette matière vers les niveaux trophiques supérieurs (Barnes et al. 2011)....

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References
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Journal ArticleDOI
TL;DR: If the organisms are randomly distributed, a single count is sufficient to obtain an estimate of their abundance and confidence limits for this estimate, even if pipetting, dilution or concentration are involved.
Abstract: Various methods for the estimation of populations of algae and other small freshwater organisms are described. A method of counting is described in detail. It is basically that of Utermohl and uses an inverted microscope. If the organisms are randomly distributed, a single count is sufficient to obtain an estimate of their abundance and confidence limits for this estimate, even if pipetting, dilution or concentration are involved. The errors in the actual counting and in converting colony counts to cell numbers are considered and found to be small relative to the random sampling error. Data are also given for a variant of Utermohl's method using a normal microscope and for a method of using a haemocytometer for the larger plankton algae.

2,572 citations


"Predicting marine phytoplankton com..." refers background or methods in this paper

  • ...Sub-samples (100 ml) were settled (Utermıhl technique (Lund et al. 1958)) and individuals counted at the species level with an inverted microscope....

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  • ...technique (Lund et al. 1958)) and individuals counted at the species level with an inverted...

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Journal ArticleDOI
TL;DR: Cellular carbon and nitrogen content and cell volume of nutritionally and morphologically diverse dinoflagellate species were measured to determine carbon to volume and nitrogen to volume relationships.
Abstract: Cellular carbon and nitrogen content and cell volume of nutritionally and morphologically diverse dinoflagellate species were measured to determine carbon to volume (C : vol) and nitrogen to volume (N : vol) relationships. Cellular C and N content ranged from 48 to 3.0 3 10 4 pgC cell 21 21 5

2,137 citations


"Predicting marine phytoplankton com..." refers background in this paper

  • ...0 −− = µvolumeyearCpg Equation 5 reported for taxonomically diverse protist plankton (Menden-Deuer and Lessard 2000)....

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  • ...reported for taxonomically diverse protist plankton (Menden-Deuer and Lessard 2000)....

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Journal ArticleDOI
TL;DR: In this paper, an estimate of global net primary production in the ocean has been computed from the monthly mean near-surface chlorophyll fields for 1979-1986 obtained by the Nimbus 7 CZCS radiometer.
Abstract: An estimate of global net primary production in the ocean has been computed from the monthly mean near-surface chlorophyll fields for 1979-1986 obtained by the Nimbus 7 CZCS radiometer. Our model required information about the subsurface distribution of chlorophyll, the parameters of the photosynthesis-light relationship, the sun angle and cloudiness. The computations were partitioned among 57 biogeochemical provinces that were specified from regional oceanography and by examination of the chlorophyll fields. Making different assumptions about the overestimation of chlorophyll by the CZCS in turbid coastal areas, the global net primary production from phytoplankton is given as 45-50 Gt C year"1. This may be compared with current published estimates for land plants of 45-68 Gt C year"' and for coastal vegetation of 1.9 Gt C year"1.

1,381 citations


"Predicting marine phytoplankton com..." refers background or methods in this paper

  • ...All changes from the implementation of Longhurst et al. (Longhurst et al. 1995) are detailed in Mélin (Mélin 2003)....

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  • ...ocean area (Longhurst et al. 1995), and to regional differences in phytoplankton community...

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  • ...PP was computed from a wavelength- and depthresolved model (Mélin 2003), building on the approach of Longhurst et al. (Longhurst et al. 1995)....

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  • ...This is due to variations in absolute productivity among regions, with 50% of production estimated to come from 27% of ocean area (Longhurst et al. 1995), and to regional differences in phytoplankton community structure....

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  • ...(Longhurst et al. 1995) are detailed in Mélin (Mélin 2003)....

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Journal ArticleDOI
TL;DR: This study provides evidence that reduced body size is the third universal ecological response to global warming in aquatic systems besides the shift of species ranges toward higher altitudes and latitudes and the seasonal shifts in life cycle events.
Abstract: Understanding the ecological impacts of climate change is a crucial challenge of the twenty-first century. There is a clear lack of general rules regarding the impacts of global warming on biota. Here, we present a metaanalysis of the effect of climate change on body size of ectothermic aquatic organisms (bacteria, phyto- and zooplankton, and fish) from the community to the individual level. Using long-term surveys, experimental data and published results, we show a significant increase in the proportion of small-sized species and young age classes and a decrease in size-at-age. These results are in accordance with the ecological rules dealing with the temperature–size relationships (i.e., Bergmann's rule, James' rule and Temperature–Size Rule). Our study provides evidence that reduced body size is the third universal ecological response to global warming in aquatic systems besides the shift of species ranges toward higher altitudes and latitudes and the seasonal shifts in life cycle events.

1,292 citations


"Predicting marine phytoplankton com..." refers background in this paper

  • ...There is evidence that reduced body size is the third universal ecological response to global warming besides the shift of species ranges toward higher altitudes and latitudes and the seasonal shifts in life-cycle events (Daufresne et al. 2009)....

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  • ...higher altitudes and latitudes and the seasonal shifts in life-cycle events (Daufresne et al. 2009)....

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Journal ArticleDOI
TL;DR: In this paper, the frequency distributions of particIe size between sizes of about I and 100 p are given for both surface and deep water of the Atlantic and Pacific Oceans.
Abstract: Frequency distributions of particIe size between sizes of about I and 100 p are given for both surface and deep water of the Atlantic and Pacific Oceans. The form of the size spectra varies predictably both geographically and with depth. A hypothesis is presented to show that, to a first approximation, roughly equal concentrations of material occur at all particle sizes within the range from 1 p to about 10” p, i.e. from bacteria to whales.

1,116 citations