A juvenile journey: Using a highly resolved 3D mooring array to investigate the roles of wind and internal tide forcing in across-shore larval transport

Abstract

The across-shore transport of meroplanktonic larvae is predominantly driven by coastal physical processes, resulting in episodic recruitment of benthic species. Historically, due to the sampling challenges associated with resolving these advective mechanisms across the continental shelf, relevant components of larval transport have been difficult to isolate and understand. We use three-dimensional temperature and velocity data from an array of 29 moorings to identify fundamental physical processes that could have generated successful across-shore transport and settlement of meroplankton. The dense spatial and temporal sampling from this array allows us to use Lagrangian particle tracking to estimate the influences of wind conditions and the internal tide on the across-shore transport of planktonic larvae. Settlement was found to be episodic at all depths studied. Above mid-water, modeled larvae were successfully transported onshore by the internal tide during wind relaxations. Surprisingly, abundant pulses of shallow-water larvae were supplied to the coast on occasions when strong, upwelling-favorable winds (> 4 m s⁻¹) drove offshore-flowing surface waters, revealing a complex, potentially topographically influenced flow. These intense upwelling-favorable winds also contributed to subsurface onshore flows that created large pulses of larval settlement in deeper waters (> 20 m). Our analyses from this highly resolved data set provide novel insights into the interactions of physical drivers in creating episodic pulses of coastal larval recruitment.