Modeling the vertical distribution of oyster larvae in response to environmental conditions

Abstract

A size-structured, time and vertically-dependent model was used to investigate the effects of water column structure on the distribution of larvae of the oyster Crassostrea virginica. Formulations used to model larval growth and behavior are based upon laboratory studies. Simulated vertical larval distributions obtained for conditions representative of a well-mixed, partially stratified and strongly stratified water column illustrate the effect that salinity and temperature gradients have on moderating larval swimming and hence on larvae vertical location. For well-mixed conditions, smaller larvae are dispersed throughout most of the water column. For strongly stratified conditions, the smaller-sized larvae cluster within the region of strong salinity change. Intermediate-sized larvae cluster within or directly below the region of strong salinity change. The oldest larvae are found near the bottom for all salinity conditions since their location is determined primarily by sinking rate. Additional simulations show that diurnal salinity changes interact with larval behavioral responses to create patchy larval distributions Finally, simulations show that the inclusion of an upwelling or downwelling velocity can overwhelm the behavioral responses of smaller larvae and result in much different vertical distributlons. The simulated vertical larval distributions show that changes in larval migratory b e h a v~o r which are brought about by changes in the vertical sal~nity gradient can significantly alter larval distribution patterns. These, when combined with horizontal advective flows, have important implications for larval dispersal.

Ocorrência de larvas Pedivéliger de ostras do genero Crassostrea Sacco, 1897 no setor euhalino do Complexo Estuarino de Paranaguá – PR.

“…(LE PENNEC, 1980;ABSHER et al, 2000;CHRISTO et al, 2010). Neste estágio, as larvas nadam ativamente pelo uso do velum (DEKSHENIEKS et al,1996), sendo as espécies diferenciadas através do número de dentes da prodissoconcha (CHRISTO et al, 2010).…”

Plankton distribution and ocean dispersal

“…Biological models, which range in complexity, attempt to mimic processes occurring during the larval lifespan. Results from coupled biological-physical numerical models show that pelagic larval duration, larval behavior and larval mortality have pronounced effects on larval distribution and dispersal patterns (Dekshenieks et al, 1996;Dekshenieks et al, 1997;Paris and Cowen, 2004;Pfeiffer-Herbert et al, 2007;North et al, 2008).…”

“…The ability to change depth allows larvae to move into different strata of the water column, where current direction can differ significantly. Observations of larval behavior in the laboratory and observations of ontogenetic position in the field have been used to parameterize behavioral components for biological models (Dekshenieks et al, 1996;Pfeiffer-Herbert et al, 2007). Coupled biological-physical numerical models including larval behavior show that behavior significantly changes larval dispersal trajectories (Rothlisberg, 1983) and ultimately population connectivity (Paris et al, 2007).…”

Behavioral responses of invertebrate larvae to water column cues

“…Self-governed vertical position in the water column affects simulated large-scale dispersal patterns (e.g. [14,15]) except when vertical mixing is strong [16]. Vertical position can be especially important for larvae accumulating in vertically sheared flows or fronts, as such flows may facilitate larval transport to nearshore settlement environments (e.g.…”