Exchange of Plankton, Pollutants, and Particles Across the Nearshore Region

Abstract

Exchange of material across the nearshore region, extending from the shoreline to a few kilometers offshore, determines the concentrations of pathogens and nutrients near the coast and the transport of larvae, whose cross-shore positions influence dispersal and recruitment. Here, we describe a framework for estimating the relative importance of cross-shore exchange mechanisms, including winds, Stokes drift, rip currents, internal waves, and diurnal heating and cooling. For each mechanism, we define an exchange velocity as a function of environmental conditions. The exchange velocity applies for organisms that keep a particular depth due to swimming or buoyancy. A related exchange diffusivity quantifies horizontal spreading of particles without enough vertical swimming speed or buoyancy to counteract turbulent velocities. This framework provides a way to determine which processes are important for cross-shore exchange for a particular study site, time period, and particle behavior. Expected final online publication date for the Annual Review of Marine Science, Volume 15 is January 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Rip Currents Off Rocky‐Shore Surge Channels

“…Contrary to bathymetrically-controlled rip currents on a sandy shore, which tend to be retained within the surf zone (Castelle et al, 2014;MacMahan et al, 2010;Moulton et al, 2023;Reniers et al, 2009), all the surge-channel rip currents on the HMS rocky shore appeared to exit the surf zone. When drifters did exit the surf zone on bathymetrically-controlled sandy shores, the offshore extent of the rip currents was approximately 3 times the width of the surf zone (Brown et al, 2018;O'Dea et al, 2021).…”

“…Contrary to bathymetrically‐controlled rip currents on a sandy shore, which tend to be retained within the surf zone (Castelle et al., 2014; MacMahan et al., 2010; Moulton et al., 2023; Reniers et al., 2009), all the surge‐channel rip currents on the HMS rocky shore appeared to exit the surf zone. MacMahan et al.…”

Detecting the most effective cleanup locations using network theory to reduce marine plastic debris: a case study in the Galapagos Marine Reserve

“…We did not include the effect of wind and waves on the movement of macroplastic through the marine reserve and neglected the impact of tides. Furthermore, coastal processes such as rip currents and wind shadow are not included in the macroplastic flow model and likely play an important role for beaching (Moulton et al, 2023). These limitations could to some extent be removed if observational data sets are improved for both flow patterns of macroplastic through the reserve and estimates of macroplastic retention rate on coastlines of the Galapagos Islands.…”

“…The aim of this paper is to investigate the use of network centralities for effective cleanup strategies; a methodology that is independent of the transition matrix used. We have therefore chosen to solely use the Eulerian surface flow for constructing the network, but the method can be easily extended to incorporate more realistic macroplastic dynamics (e.g., Moulton et al, 2023). We address the implications of this choice in Sect.…”

Modeled Coastal‐Ocean Pathways of Land‐Sourced Contaminants in the Aftermath of Hurricane Florence

“…This was separated in time from the elevated river discharge following the storm (9/17–9/27) (Figure 3), when surface waves were observed to be small (wave height ∼1 m) and thus not expected to have a substantial impact on the large‐scale behavior of the river plumes. Near the beach, detailed pathways of contaminants could be modeled more accurately with a higher resolution model with surface wave coupling (Brasseale et al., 2023; Feddersen et al., 2021) to simulate rip currents and other nearshore processes that affect the longshore transport, dilution, and cross‐shore exchange of material (Moulton et al., 2023).…”