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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.


Advective loss [advsurv dimensionless as defined in equation (10b)] as a function of light attenuation (K500, m−1) for two fjords with a shallow (10 m) and a deep (100 m) sill. (A) Large individuals, (B) small individuals. The bottom depth of the fjords was set equal to 500 m.
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FBQ015F5: Advective loss [advsurv dimensionless as defined in equation (10b)] as a function of light attenuation (K500, m−1) for two fjords with a shallow (10 m) and a deep (100 m) sill. (A) Large individuals, (B) small individuals. The bottom depth of the fjords was set equal to 500 m.

Mentions: The increased light attenuation leads to increased advective loss, i.e. more individuals are transported out of the fjord (Fig. 5A and B). This is clearly seen for the deep sill (100 m) combined with high attenuation which leads to an advective loss above 0.9 for both size groups (Fig. 5A and B). The explanation is that the high light attenuation has shoaled the habitat of P. periphylla so it becomes part of the advective layer. The small individuals always have the lowest advective loss since their preference for lower light (Table I) results in a deeper location than that of the larger individuals. Also for the shallow sill (10 m), the advective loss increases with increased attenuation (Fig. 5A and B) although less than for the deep sill fjord. Thus, while increased attenuation increases survival, it also increases the advective loss which imposes opposite effects on the retention as defined in equation (10).


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

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

Advective loss [advsurv dimensionless as defined in equation (10b)] as a function of light attenuation (K500, m−1) for two fjords with a shallow (10 m) and a deep (100 m) sill. (A) Large individuals, (B) small individuals. The bottom depth of the fjords was set equal to 500 m.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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

FBQ015F5: Advective loss [advsurv dimensionless as defined in equation (10b)] as a function of light attenuation (K500, m−1) for two fjords with a shallow (10 m) and a deep (100 m) sill. (A) Large individuals, (B) small individuals. The bottom depth of the fjords was set equal to 500 m.
Mentions: The increased light attenuation leads to increased advective loss, i.e. more individuals are transported out of the fjord (Fig. 5A and B). This is clearly seen for the deep sill (100 m) combined with high attenuation which leads to an advective loss above 0.9 for both size groups (Fig. 5A and B). The explanation is that the high light attenuation has shoaled the habitat of P. periphylla so it becomes part of the advective layer. The small individuals always have the lowest advective loss since their preference for lower light (Table I) results in a deeper location than that of the larger individuals. Also for the shallow sill (10 m), the advective loss increases with increased attenuation (Fig. 5A and B) although less than for the deep sill fjord. Thus, while increased attenuation increases survival, it also increases the advective loss which imposes opposite effects on the retention as defined in equation (10).

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.