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Simulation of optically conditioned retention and mass occurrences of Periphylla periphylla.

Dupont N, Aksnes DL - J. Plankton Res. (2010)

Bottom Line: Our results suggest that light attenuation, in combination with advection, has a two-sided effect on retention and that three fjord categories can be defined.In category 3, further increase in light attenuation, however, shoals the habitat so that individuals are increasingly exposed to advection and this results in loss of individuals and decreased retention.This classification requires accurate determinations of the organism's light preference, the water column light attenuation and topographical characteristics affecting advection.

View Article: PubMed Central - PubMed

Affiliation: Department of biology , University of Bergen , PO Box 7803, N-5020 Bergen , Norway.

ABSTRACT
Jellyfish blooms are of increasing concern in many parts of the world, and in Norwegian fjords an apparent increase in mass occurrences of the deep water jellyfish Periphylla periphylla has attracted attention. Here we investigate the hypothesis that changes in the water column light attenuation might cause local retention and thereby facilitate mass occurrences. We use a previously tested individual-based model of light-mediated vertical migration in P. periphylla to simulate how retention is affected by changes in light attenuation. Our results suggest that light attenuation, in combination with advection, has a two-sided effect on retention and that three fjord categories can be defined. In category 1, increased light attenuation turns fjords into dark "deep-sea" environments which increase the habitat and retention of P. periphylla. In category 2, an optimal light attenuation facilitates the maximum retention and likelihood for mass occurrences. In category 3, further increase in light attenuation, however, shoals the habitat so that individuals are increasingly exposed to advection and this results in loss of individuals and decreased retention. This classification requires accurate determinations of the organism's light preference, the water column light attenuation and topographical characteristics affecting advection.

No MeSH data available.


Conceptual scheme of the swimming model modified after Dupont et al. (Dupont et al., 2009). (A) How Zmax and Zmin (in m) are related to Emax and Emin (dimensionless). (B) The arrows represent the possible swimming directions depending on the location of the individual in the water column (upward corresponds to α = 1 and downward to α = −1, see text). The shaded areas represent individual variations in Zmax and Zmin as a result of individual variances in Emax and Emin.
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FBQ015F1: Conceptual scheme of the swimming model modified after Dupont et al. (Dupont et al., 2009). (A) How Zmax and Zmin (in m) are related to Emax and Emin (dimensionless). (B) The arrows represent the possible swimming directions depending on the location of the individual in the water column (upward corresponds to α = 1 and downward to α = −1, see text). The shaded areas represent individual variations in Zmax and Zmin as a result of individual variances in Emax and Emin.

Mentions: The ambient light (Emed) at the depth (Zmed) of an individual determines which value α takes at each time step (see what follows). Emed is calculated according to the Beer–Lambert law, Emed = E0exp(−KZmed), E0 is the surface irradiance and K is the attenuation for downwelling irradiance between the surface and the depth Emed. We used the mechanism that gave the best fit with observations in Dupont et al. (Dupont et al., 2009) to set the α value for each individual at each time step (Fig. 1). If the value of Emed is between Emin and Emax (Fig. 1A), α is set randomly at either −1 or 1. Otherwise if Emed is lower than Emin (which means that Zmed is deeper than Zmin) or higher than Emax (Zmed is shallower than Zmax), α is set to 1 and −1, respectively (Fig. 1B). The individual values of the Emin and Emax parameters are distributed according to a gamma distribution with the mean values and and the variances and .


Simulation of optically conditioned retention and mass occurrences of Periphylla periphylla.

Dupont N, Aksnes DL - J. Plankton Res. (2010)

Conceptual scheme of the swimming model modified after Dupont et al. (Dupont et al., 2009). (A) How Zmax and Zmin (in m) are related to Emax and Emin (dimensionless). (B) The arrows represent the possible swimming directions depending on the location of the individual in the water column (upward corresponds to α = 1 and downward to α = −1, see text). The shaded areas represent individual variations in Zmax and Zmin as a result of individual variances in Emax and Emin.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2864668&req=5

FBQ015F1: Conceptual scheme of the swimming model modified after Dupont et al. (Dupont et al., 2009). (A) How Zmax and Zmin (in m) are related to Emax and Emin (dimensionless). (B) The arrows represent the possible swimming directions depending on the location of the individual in the water column (upward corresponds to α = 1 and downward to α = −1, see text). The shaded areas represent individual variations in Zmax and Zmin as a result of individual variances in Emax and Emin.
Mentions: The ambient light (Emed) at the depth (Zmed) of an individual determines which value α takes at each time step (see what follows). Emed is calculated according to the Beer–Lambert law, Emed = E0exp(−KZmed), E0 is the surface irradiance and K is the attenuation for downwelling irradiance between the surface and the depth Emed. We used the mechanism that gave the best fit with observations in Dupont et al. (Dupont et al., 2009) to set the α value for each individual at each time step (Fig. 1). If the value of Emed is between Emin and Emax (Fig. 1A), α is set randomly at either −1 or 1. Otherwise if Emed is lower than Emin (which means that Zmed is deeper than Zmin) or higher than Emax (Zmed is shallower than Zmax), α is set to 1 and −1, respectively (Fig. 1B). The individual values of the Emin and Emax parameters are distributed according to a gamma distribution with the mean values and and the variances and .

Bottom Line: Our results suggest that light attenuation, in combination with advection, has a two-sided effect on retention and that three fjord categories can be defined.In category 3, further increase in light attenuation, however, shoals the habitat so that individuals are increasingly exposed to advection and this results in loss of individuals and decreased retention.This classification requires accurate determinations of the organism's light preference, the water column light attenuation and topographical characteristics affecting advection.

View Article: PubMed Central - PubMed

Affiliation: Department of biology , University of Bergen , PO Box 7803, N-5020 Bergen , Norway.

ABSTRACT
Jellyfish blooms are of increasing concern in many parts of the world, and in Norwegian fjords an apparent increase in mass occurrences of the deep water jellyfish Periphylla periphylla has attracted attention. Here we investigate the hypothesis that changes in the water column light attenuation might cause local retention and thereby facilitate mass occurrences. We use a previously tested individual-based model of light-mediated vertical migration in P. periphylla to simulate how retention is affected by changes in light attenuation. Our results suggest that light attenuation, in combination with advection, has a two-sided effect on retention and that three fjord categories can be defined. In category 1, increased light attenuation turns fjords into dark "deep-sea" environments which increase the habitat and retention of P. periphylla. In category 2, an optimal light attenuation facilitates the maximum retention and likelihood for mass occurrences. In category 3, further increase in light attenuation, however, shoals the habitat so that individuals are increasingly exposed to advection and this results in loss of individuals and decreased retention. This classification requires accurate determinations of the organism's light preference, the water column light attenuation and topographical characteristics affecting advection.

No MeSH data available.