Abstract
For many organisms, the reconstruction of source-sink dynamics is hampered by limited knowledge of the spatial assemblage of either the source or sink components or lack of information on the strength of the linkage for any source-sink pair. In the case of marine species with a pelagic dispersal phase, these problems may be mitigated through the use of particle drift simulations based on an ocean circulation model. However, when simulated particle trajectories do not intersect sampling sites, the corroboration of model drift simulations with field data is hampered. Here, we apply a new statistical approach for reconstructing source-sink dynamics that overcomes the aforementioned problems. Our research is motivated by the need for understanding observed changes in jellyfish distributions in the eastern Bering Sea since 1990. By contrasting the source-sink dynamics reconstructed with data from the pre-1990 period with that from the post-1990 period, it appears that changes in jellyfish distribution resulted from the combined effects of higher jellyfish productivity and longer dispersal of jellyfish resulting from a shift in the ocean circulation starting in 1991. A sensitivity analysis suggests that the source-sink reconstruction is robust to typical systematic and random errors in the ocean circulation model driving the particle drift simulations. The jellyfish analysis illustrates that new insights can be gained by studying structural changes in source-sink dynamics. The proposed approach is applicable for the spatial source-sink reconstruction of other species and even abiotic processes, such as sediment transport.
Highlights
Jellyfish Biomass and Study Region Jellyfish biomass and distribution for the period 1982–2004 were obtained from quantitative bottom trawl surveys of groundfish on the eastern Bering Sea (EBS) shelf conducted by the Alaska Fisheries Science Center (AFSC) [22,28,29], the data of which can be downloaded from the RACE groundfish data base http://www. afsc.noaa.gov/RACE/groundfish/survey_data/data.htm
Since jellyfish are distributed throughout the water column (30–40 m mean depth; [29,32]), the medusa biomass estimated from the bottom trawl catch used here are considered an index of relative abundance that is comparable among stations and years
By comparing Regional Ocean Modeling System (ROMS) simulated ocean velocities with observed velocities derived from satellite tracked drifters, we found that the ROMS simulation captures the observed current directions reasonably well, but the simulation tends to underestimate the current amplitude
Summary
The process of reconstructing the spatial assemblage of source-sink systems involves the simulation of propagules drifting from the putative source to the putative sink locations, and the comparison of the model outcome with the field observations. In marine ecology this practice is becoming increasingly common, with the development of high resolution ocean circulation models coupled to individual based models, which simulate ocean currents and individual behavior during the drifting phase [16].
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