Valle-Levinson Arnoldo

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Valle-Levinson
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Arnoldo
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  • Article
    Biophysical mechanisms of larval fish ingress into Chesapeake Bay
    (Inter-Research, 2005-11-21) Hare, Jonathan A. ; Thorrold, Simon R. ; Walsh, Harvey J. ; Reiss, Christian S. ; Valle-Levinson, Arnoldo ; Jones, Cynthia M.
    Selective tidal stream transport is hypothesized as a dominant mechanism by which larvae of marine animals move through estuarine openings. For larvae moving from the shelf to estuarine habitats, selective tidal stream transport proposes that larvae are higher in the water column during flood tide and lower in the water column during ebb tide. Although a number of studies conclude that selective tidal stream transport is the mechanism responsible for larval ingress, few studies consider alternative mechanisms or consider passive explanations for tidal patterns in larval distributions. We examined the biophysical mechanisms responsible for larval ingress into Chesapeake Bay using an Eulerian approach. We made flux calculations for 3 species and partitioned flux estimates among 3 different ingress mechanisms (wind forcing, residual bottom inflow and tidal). For the Atlantic croaker Micropogonias undulatus (Sciaenidae), all 3 mechanisms of ingress contributed to the net up-estuary flux of larvae, but tidal mechanisms become more important for larger sizes. Net up-estuary flux of the Atlantic menhaden Brevoortia tyrannus (Clupeidae) was dominated by residual bottom inflow and wind forcing. Ingress of the summer flounder Paralichthys dentatus (Paralichthyidae) was dominated by tidal mechanisms, and the importance of tides increased with developmental stage. We found little evidence for the hypothesis that tidal patterns in larval distributions resulted from passive processes (water mass-specific distributions, buoyancy, vertical mixing), thereby supporting the hypothesis that tidal patterns resulted from active behaviors. However, our estimates of vertical mixing were not direct and additional work is needed to examine the role of vertical mixing in influencing vertical distributions in areas with strong tides. We conclude that a combination of wind forcing, residual bottom inflow, and selective tidal stream transport are responsible for the ingress of larval fishes into Chesapeake Bay, and that the relative importance of the 3 mechanisms differs among species and changes with larval development.
  • Article
    Intraseasonal variation in southeast Pacific blue whale acoustic presence, zooplankton backscatter, and oceanographic variables on a feeding ground in Northern Chilean Patagonia
    (Elsevier, 2021-11-09) Buchan, Susannah J. ; Pérez-Santos, Iván ; Narváez, Diego ; Castro, Leonardo ; Stafford, Kathleen M. ; Baumgartner, Mark F. ; Valle-Levinson, Arnoldo ; Montero, Paulina ; Gutierrez, Laura ; Rojas, Constanza ; Daneri, Giovanni ; Neira, Sergio
    Seasonal variation in the acoustic presence of blue whale calls has been widely reported for feeding grounds worldwide, however variation over the submonthly scale (several days to <1 month) has been examined to a much lesser extent. This study combines passive acoustic, hydroacoustic, and in situ oceanographic observations collected at a mooring in the Corcovado Gulf, Northern Chilean Patagonia, from January 2016-February 2017, to examine the temporal variation in blue whale acoustic occurrence and prey backscatter over seasonal and submonthly scales. Time series data for a) Southeast Pacific blue whale song calls and D-calls, b) zooplankton backscatter, c) tidal amplitude, and d) meridional and zonal wind stress were examined visually for seasonal trends. To examine submonthly timescales over the summer feeding season (January-June), wavelet transforms and wavelet coherence were applied; generalized linear models (GLM) were also applied. There was a 3-month lag between the seasonal onsets of high zooplankton backscatter (October) and blue whale acoustic presence (January), and an almost immediate drop in blue whale acoustic presence with the seasonal decrease of backscatter (June). This may be due to the use of memory by animals when timing their arrival on the feeding ground, but the timing of their departure may be related to detection of low prey availability. Over the summer feeding season, blue whale acoustic presence was strongly associated with zooplankton backscatter (GLM coefficient p ≪ 0.0001). Song calls followed a seasonal cycle, but D-calls appeared to respond to short term variations in environmental conditions over submonthly scales. Results suggest that spring tides may increase prey aggregation and/or transport into the Corcovado Gulf, leading to increased blue whale acoustic presence over 15-day or 30-day cycles; and short-lived events of increased wind stress with periodicities of 2–8 days and 16–30 days, may also contribute to the aggregation of prey. We discuss the strengths and limitations of coupling passive and active acoustic data to examine drivers of blue whale distribution.