The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Jamie Macmahan - One of the best experts on this subject based on the ideXlab platform.
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Geometric Roughness Estimates of Surf-Zone Wave-Breaking Foam
Boundary-Layer Meteorology, 2019Co-Authors: Ami Hansen, Jamie MacmahanAbstract:Measurements of small-scale [O (mm)] geometric roughness length ( $$ k_{\text{f}} $$ k f ) associated with Surface foam generated by depth-limited breaking waves were obtained within the Surf Zone on a sandy beach. The parameter $$ k_{\text{f}} $$ k f is described using the vertical standard deviation of the sea Surface elevation for a foamy area as estimated from stereo imagery. A waterproof two-camera system with self-logging and internal power was developed for collecting stereo images using commercial off-the-shelf components and commercial software for operations 1 m above the sea Surface within the middle of the Surf Zone. The Surf-Zone foam had a mean $$ k_{\text{f}} $$ k f value of 3.2 mm, ranging from 1.7 to 6.3 mm. Using an empirical land-based relationship results in a mean aerodynamic roughness length for Surf-Zone foam of 0.82 mm, with a range from 0.4 to 1.6 mm, which provides a reasonable estimate of the Surf-Zone drag coefficient compared with field measurements.
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Persistent Differences in Horizontal Gradients in Phytoplankton Concentration Maintained by Surf Zone Hydrodynamics
Estuaries and Coasts, 2018Co-Authors: Alan L. Shanks, Jamie Macmahan, Jenna Brown, Steven G Morgan, Ad J.h.m. Reniers, Atsushi Fujimura, Marley Jarvis, Lisa Ziccarelli, Chris GriesemerAbstract:Surf Zones, regions of breaking waves, are at the interface between the shore and coastal ocean. Surf Zone hydrodynamics may affect delivery of phytoplankton subsidies to the intertidal Zone. Over a month of daily sampling at an intermediate Surf Zone with bathymetric rip currents and a reflective Surf Zone, we measured Surf Zone hydrodynamics and compared concentrations of coastal phytoplankton taxa in the Surf Zones to concentrations offshore. At the intermediate Surf Zone, ~80% of the variability in the concentration of coastal phytoplankton taxa within the Surf Zone was explained by their variation offshore; however, concentrations were much higher and lower than those offshore in samples from a bathymetric rip current and over the adjacent shoal, respectively. Hydrodynamics at this intermediate Surf Zone did not hinder the delivery of coastal phytoplankton to the Surf Zone, but the bathymetric rip current system appeared to redistribute phytoplankton concentrating them within eddies. At the reflective shore, we sampled Surf Zones at a beach and two adjacent rocky intertidal sites. Concentrations of typical coastal phytoplankton taxa were usually an order of magnitude or more lower than those offshore, even when offshore samples were collected just 20 m beyond the breakers. The phytoplankton assemblages inside and outside the Surf Zone often appeared to be disconnected. Surf Zone hydrodynamics at the steep, reflective shore coupled with low phytoplankton concentrations in near-Surface water appeared to limit delivery of phytoplankton subsidies to the Surf Zone. Surf Zone hydrodynamics may be a key factor in the alongshore variation in phytoplankton subsidies to coastal communities.
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Planktonic Subsidies to Surf-Zone and Intertidal Communities
Annual Review of Marine Science, 2017Co-Authors: Steven G Morgan, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Falk FeddersenAbstract:Plankton are transported onshore, providing subsidies of food and new recruits to Surf-Zone and intertidal communities. The transport of plankton to the Surf Zone is influenced by wind, wave, and tidal forcing, and whether they enter the Surf Zone depends on alongshore variation in Surf-Zone hydrodynamics caused by the interaction of breaking waves with coastal morphology. Areas with gently sloping shores and wide Surf Zones typically have orders-of-magnitude-higher concentrations of plankton in the Surf Zone and dense larval settlement in intertidal communities because of the presence of bathymetric rip currents, which are absent in areas with steep shores and narrow Surf Zones. These striking differences in subsidies have profound consequences; areas with greater subsidies support more productive Surf-Zone communities and possibly more productive rocky intertidal communities. Recognition of the importance of spatial subsidies for rocky community dynamics has recently advanced ecological theory, and inco...
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Planktonic Subsidies to Surf-Zone and Intertidal Communities
Annual review of marine science, 2017Co-Authors: Steven G Morgan, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Falk FeddersenAbstract:Plankton are transported onshore, providing subsidies of food and new recruits to Surf-Zone and intertidal communities. The transport of plankton to the Surf Zone is influenced by wind, wave, and tidal forcing, and whether they enter the Surf Zone depends on alongshore variation in Surf-Zone hydrodynamics caused by the interaction of breaking waves with coastal morphology. Areas with gently sloping shores and wide Surf Zones typically have orders-of-magnitude-higher concentrations of plankton in the Surf Zone and dense larval settlement in intertidal communities because of the presence of bathymetric rip currents, which are absent in areas with steep shores and narrow Surf Zones. These striking differences in subsidies have profound consequences; areas with greater subsidies support more productive Surf-Zone communities and possibly more productive rocky intertidal communities. Recognition of the importance of spatial subsidies for rocky community dynamics has recently advanced ecological theory, and incorporating Surf-Zone hydrodynamics would be an especially fruitful line of investigation.
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Alongshore variation in barnacle populations is determined by Surf Zone hydrodynamics
Ecological Monographs, 2017Co-Authors: Alan L. Shanks, Jamie Macmahan, Steven G Morgan, Ad ReniersAbstract:Author(s): Shanks, AL; Morgan, SG; MacMahan, J; Reniers, AJHM | Abstract: © 2017 by the Ecological Society of America Larvae in the coastal ocean are transported toward shore by a variety of mechanisms. Crossing the Surf Zone is the last step in a shoreward migration and Surf Zones may act as semipermeable barriers altering delivery of larvae to the shore. We related variation in the structure of intertidal barnacle populations to Surf Zone width (Surf Zone hydrodynamics proxy), wave height, alongshore wind stress (upwelling proxy), solar radiation, and latitude at 40 rocky intertidal sites from San Diego, California to the Olympic Peninsula, Washington. We measured daily settlement and weekly recruitment of barnacles at selected sites and related these measures to Surf Zone width. Chthamalus density varied inversely with that of Balanus, and the density of Balanus and new recruits was negatively related to solar radiation. Across the region, long-term mean wave height and an indicator of upwelling intensity and frequency did not explain variation in Balanus or new recruit densities. Balanus and new recruit densities, daily settlement, and weekly recruitment were up to three orders of magnitude higher at sites with wide (g50 m), more dissipative Surf Zones with bathymetric rip currents than at sites with narrow (l50 m) more reflective Surf Zones. Surf Zone width explained 30–50% of the variability in Balanus and new recruit densities. We sampled a subset of sites l5 km apart where coastal hydrodynamics such as upwelling should be very similar. At paired sites with similar Surf Zone widths, Balanus densities were not different. If Surf Zone widths at paired sites were dissimilar, Balanus densities, daily settlement, and weekly recruitment were significantly higher at sites with the wider, more dissipative Surf Zone. The primary drivers of Surf Zone hydrodynamics are the wave climate and the slope of the shore and these persist over time; therefore site-specific stability in Surf Zone hydrodynamics should result in stable barnacle population characteristics. Variations in Surf Zone hydrodynamics appear to play a fundamental role in regulating barnacle populations along the open coast, which, in turn, may have consequences for the entire intertidal community.
Steven G Morgan - One of the best experts on this subject based on the ideXlab platform.
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Persistent Differences in Horizontal Gradients in Phytoplankton Concentration Maintained by Surf Zone Hydrodynamics
Estuaries and Coasts, 2018Co-Authors: Alan L. Shanks, Jamie Macmahan, Jenna Brown, Steven G Morgan, Ad J.h.m. Reniers, Atsushi Fujimura, Marley Jarvis, Lisa Ziccarelli, Chris GriesemerAbstract:Surf Zones, regions of breaking waves, are at the interface between the shore and coastal ocean. Surf Zone hydrodynamics may affect delivery of phytoplankton subsidies to the intertidal Zone. Over a month of daily sampling at an intermediate Surf Zone with bathymetric rip currents and a reflective Surf Zone, we measured Surf Zone hydrodynamics and compared concentrations of coastal phytoplankton taxa in the Surf Zones to concentrations offshore. At the intermediate Surf Zone, ~80% of the variability in the concentration of coastal phytoplankton taxa within the Surf Zone was explained by their variation offshore; however, concentrations were much higher and lower than those offshore in samples from a bathymetric rip current and over the adjacent shoal, respectively. Hydrodynamics at this intermediate Surf Zone did not hinder the delivery of coastal phytoplankton to the Surf Zone, but the bathymetric rip current system appeared to redistribute phytoplankton concentrating them within eddies. At the reflective shore, we sampled Surf Zones at a beach and two adjacent rocky intertidal sites. Concentrations of typical coastal phytoplankton taxa were usually an order of magnitude or more lower than those offshore, even when offshore samples were collected just 20 m beyond the breakers. The phytoplankton assemblages inside and outside the Surf Zone often appeared to be disconnected. Surf Zone hydrodynamics at the steep, reflective shore coupled with low phytoplankton concentrations in near-Surface water appeared to limit delivery of phytoplankton subsidies to the Surf Zone. Surf Zone hydrodynamics may be a key factor in the alongshore variation in phytoplankton subsidies to coastal communities.
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Planktonic Subsidies to Surf-Zone and Intertidal Communities
Annual Review of Marine Science, 2017Co-Authors: Steven G Morgan, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Falk FeddersenAbstract:Plankton are transported onshore, providing subsidies of food and new recruits to Surf-Zone and intertidal communities. The transport of plankton to the Surf Zone is influenced by wind, wave, and tidal forcing, and whether they enter the Surf Zone depends on alongshore variation in Surf-Zone hydrodynamics caused by the interaction of breaking waves with coastal morphology. Areas with gently sloping shores and wide Surf Zones typically have orders-of-magnitude-higher concentrations of plankton in the Surf Zone and dense larval settlement in intertidal communities because of the presence of bathymetric rip currents, which are absent in areas with steep shores and narrow Surf Zones. These striking differences in subsidies have profound consequences; areas with greater subsidies support more productive Surf-Zone communities and possibly more productive rocky intertidal communities. Recognition of the importance of spatial subsidies for rocky community dynamics has recently advanced ecological theory, and inco...
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Planktonic Subsidies to Surf-Zone and Intertidal Communities
Annual review of marine science, 2017Co-Authors: Steven G Morgan, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Falk FeddersenAbstract:Plankton are transported onshore, providing subsidies of food and new recruits to Surf-Zone and intertidal communities. The transport of plankton to the Surf Zone is influenced by wind, wave, and tidal forcing, and whether they enter the Surf Zone depends on alongshore variation in Surf-Zone hydrodynamics caused by the interaction of breaking waves with coastal morphology. Areas with gently sloping shores and wide Surf Zones typically have orders-of-magnitude-higher concentrations of plankton in the Surf Zone and dense larval settlement in intertidal communities because of the presence of bathymetric rip currents, which are absent in areas with steep shores and narrow Surf Zones. These striking differences in subsidies have profound consequences; areas with greater subsidies support more productive Surf-Zone communities and possibly more productive rocky intertidal communities. Recognition of the importance of spatial subsidies for rocky community dynamics has recently advanced ecological theory, and incorporating Surf-Zone hydrodynamics would be an especially fruitful line of investigation.
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Alongshore variation in barnacle populations is determined by Surf Zone hydrodynamics
Ecological Monographs, 2017Co-Authors: Alan L. Shanks, Jamie Macmahan, Steven G Morgan, Ad ReniersAbstract:Author(s): Shanks, AL; Morgan, SG; MacMahan, J; Reniers, AJHM | Abstract: © 2017 by the Ecological Society of America Larvae in the coastal ocean are transported toward shore by a variety of mechanisms. Crossing the Surf Zone is the last step in a shoreward migration and Surf Zones may act as semipermeable barriers altering delivery of larvae to the shore. We related variation in the structure of intertidal barnacle populations to Surf Zone width (Surf Zone hydrodynamics proxy), wave height, alongshore wind stress (upwelling proxy), solar radiation, and latitude at 40 rocky intertidal sites from San Diego, California to the Olympic Peninsula, Washington. We measured daily settlement and weekly recruitment of barnacles at selected sites and related these measures to Surf Zone width. Chthamalus density varied inversely with that of Balanus, and the density of Balanus and new recruits was negatively related to solar radiation. Across the region, long-term mean wave height and an indicator of upwelling intensity and frequency did not explain variation in Balanus or new recruit densities. Balanus and new recruit densities, daily settlement, and weekly recruitment were up to three orders of magnitude higher at sites with wide (g50 m), more dissipative Surf Zones with bathymetric rip currents than at sites with narrow (l50 m) more reflective Surf Zones. Surf Zone width explained 30–50% of the variability in Balanus and new recruit densities. We sampled a subset of sites l5 km apart where coastal hydrodynamics such as upwelling should be very similar. At paired sites with similar Surf Zone widths, Balanus densities were not different. If Surf Zone widths at paired sites were dissimilar, Balanus densities, daily settlement, and weekly recruitment were significantly higher at sites with the wider, more dissipative Surf Zone. The primary drivers of Surf Zone hydrodynamics are the wave climate and the slope of the shore and these persist over time; therefore site-specific stability in Surf Zone hydrodynamics should result in stable barnacle population characteristics. Variations in Surf Zone hydrodynamics appear to play a fundamental role in regulating barnacle populations along the open coast, which, in turn, may have consequences for the entire intertidal community.
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Transport of larvae and detritus across the Surf Zone of a steep reflective pocket beach
Marine Ecology Progress Series, 2015Co-Authors: Alan L. Shanks, Jamie Macmahan, Jenna Brown, Ad Reniers, Steven G Morgan, Atsushi Fujimura, Marley Jarvis, Chris GriesemerAbstract:Larvae of many intertidal species develop offshore and must cross the Surf Zone to complete their onshore migration to adult habitats. Depending on hydrodynamics, the Surf Zone may limit this migration, especially on reflective rocky shores. As a logistically tractable analog of a rocky shore environment, we carried out a comprehensive biological and physical study of the hydrodynamics of a steep reflective sandy beach. Holoplankton and precompetent larval invertebrates were much less abundant within the Surf Zone than offshore, and their concentrations inside and outside the Surf Zone were not significantly correlated, suggesting that they were not entering the Surf Zone. Persistent offshore flow throughout the water column at the outer edge of the Surf Zone may prevent these organisms from entering the Surf Zone. In contrast, the concentrations of detritus and a competent larval invertebrate (i.e. cyprids), while also not significantly correlated with concentrations offshore, were frequently more concentrated in the Surf Zone than offshore. Within the Surf Zone, the concentration of detritus was significantly correlated with concentrations of competent larval invertebrates (barnacles, gastropods, polychaetes, and bopyrid amphipod) and organisms that may be associated with detritus (amphipods and harpacticoid copepods). These concentrations were significantly negatively correlated with average daily wave height. We hypothesize that detritus and larvae enter the Surf Zone near the bottom during calm wave conditions by a process of near-bottom streaming. Near-bottom streaming is associated with all Surf Zones and may be a general mechanism for onshore transport of larvae close to the coast.
Ad Reniers - One of the best experts on this subject based on the ideXlab platform.
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Planktonic Subsidies to Surf-Zone and Intertidal Communities
Annual Review of Marine Science, 2017Co-Authors: Steven G Morgan, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Falk FeddersenAbstract:Plankton are transported onshore, providing subsidies of food and new recruits to Surf-Zone and intertidal communities. The transport of plankton to the Surf Zone is influenced by wind, wave, and tidal forcing, and whether they enter the Surf Zone depends on alongshore variation in Surf-Zone hydrodynamics caused by the interaction of breaking waves with coastal morphology. Areas with gently sloping shores and wide Surf Zones typically have orders-of-magnitude-higher concentrations of plankton in the Surf Zone and dense larval settlement in intertidal communities because of the presence of bathymetric rip currents, which are absent in areas with steep shores and narrow Surf Zones. These striking differences in subsidies have profound consequences; areas with greater subsidies support more productive Surf-Zone communities and possibly more productive rocky intertidal communities. Recognition of the importance of spatial subsidies for rocky community dynamics has recently advanced ecological theory, and inco...
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Planktonic Subsidies to Surf-Zone and Intertidal Communities
Annual review of marine science, 2017Co-Authors: Steven G Morgan, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Falk FeddersenAbstract:Plankton are transported onshore, providing subsidies of food and new recruits to Surf-Zone and intertidal communities. The transport of plankton to the Surf Zone is influenced by wind, wave, and tidal forcing, and whether they enter the Surf Zone depends on alongshore variation in Surf-Zone hydrodynamics caused by the interaction of breaking waves with coastal morphology. Areas with gently sloping shores and wide Surf Zones typically have orders-of-magnitude-higher concentrations of plankton in the Surf Zone and dense larval settlement in intertidal communities because of the presence of bathymetric rip currents, which are absent in areas with steep shores and narrow Surf Zones. These striking differences in subsidies have profound consequences; areas with greater subsidies support more productive Surf-Zone communities and possibly more productive rocky intertidal communities. Recognition of the importance of spatial subsidies for rocky community dynamics has recently advanced ecological theory, and incorporating Surf-Zone hydrodynamics would be an especially fruitful line of investigation.
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Alongshore variation in barnacle populations is determined by Surf Zone hydrodynamics
Ecological Monographs, 2017Co-Authors: Alan L. Shanks, Jamie Macmahan, Steven G Morgan, Ad ReniersAbstract:Author(s): Shanks, AL; Morgan, SG; MacMahan, J; Reniers, AJHM | Abstract: © 2017 by the Ecological Society of America Larvae in the coastal ocean are transported toward shore by a variety of mechanisms. Crossing the Surf Zone is the last step in a shoreward migration and Surf Zones may act as semipermeable barriers altering delivery of larvae to the shore. We related variation in the structure of intertidal barnacle populations to Surf Zone width (Surf Zone hydrodynamics proxy), wave height, alongshore wind stress (upwelling proxy), solar radiation, and latitude at 40 rocky intertidal sites from San Diego, California to the Olympic Peninsula, Washington. We measured daily settlement and weekly recruitment of barnacles at selected sites and related these measures to Surf Zone width. Chthamalus density varied inversely with that of Balanus, and the density of Balanus and new recruits was negatively related to solar radiation. Across the region, long-term mean wave height and an indicator of upwelling intensity and frequency did not explain variation in Balanus or new recruit densities. Balanus and new recruit densities, daily settlement, and weekly recruitment were up to three orders of magnitude higher at sites with wide (g50 m), more dissipative Surf Zones with bathymetric rip currents than at sites with narrow (l50 m) more reflective Surf Zones. Surf Zone width explained 30–50% of the variability in Balanus and new recruit densities. We sampled a subset of sites l5 km apart where coastal hydrodynamics such as upwelling should be very similar. At paired sites with similar Surf Zone widths, Balanus densities were not different. If Surf Zone widths at paired sites were dissimilar, Balanus densities, daily settlement, and weekly recruitment were significantly higher at sites with the wider, more dissipative Surf Zone. The primary drivers of Surf Zone hydrodynamics are the wave climate and the slope of the shore and these persist over time; therefore site-specific stability in Surf Zone hydrodynamics should result in stable barnacle population characteristics. Variations in Surf Zone hydrodynamics appear to play a fundamental role in regulating barnacle populations along the open coast, which, in turn, may have consequences for the entire intertidal community.
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Transport of larvae and detritus across the Surf Zone of a steep reflective pocket beach
Marine Ecology Progress Series, 2015Co-Authors: Alan L. Shanks, Jamie Macmahan, Jenna Brown, Ad Reniers, Steven G Morgan, Atsushi Fujimura, Marley Jarvis, Chris GriesemerAbstract:Larvae of many intertidal species develop offshore and must cross the Surf Zone to complete their onshore migration to adult habitats. Depending on hydrodynamics, the Surf Zone may limit this migration, especially on reflective rocky shores. As a logistically tractable analog of a rocky shore environment, we carried out a comprehensive biological and physical study of the hydrodynamics of a steep reflective sandy beach. Holoplankton and precompetent larval invertebrates were much less abundant within the Surf Zone than offshore, and their concentrations inside and outside the Surf Zone were not significantly correlated, suggesting that they were not entering the Surf Zone. Persistent offshore flow throughout the water column at the outer edge of the Surf Zone may prevent these organisms from entering the Surf Zone. In contrast, the concentrations of detritus and a competent larval invertebrate (i.e. cyprids), while also not significantly correlated with concentrations offshore, were frequently more concentrated in the Surf Zone than offshore. Within the Surf Zone, the concentration of detritus was significantly correlated with concentrations of competent larval invertebrates (barnacles, gastropods, polychaetes, and bopyrid amphipod) and organisms that may be associated with detritus (amphipods and harpacticoid copepods). These concentrations were significantly negatively correlated with average daily wave height. We hypothesize that detritus and larvae enter the Surf Zone near the bottom during calm wave conditions by a process of near-bottom streaming. Near-bottom streaming is associated with all Surf Zones and may be a general mechanism for onshore transport of larvae close to the coast.
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Bathymetric control of Surf Zone retention on a rip-channelled beach
Ocean Dynamics, 2014Co-Authors: Bruno Castelle, Ad Reniers, Jamie MacmahanAbstract:Simulations from a numerical model address the impact of nearshore morphology on Surf Zone retention on, open coast, rip-channelled beaches exposed to shore-normal waves. In the model, rip channels are regularly spaced alongshore with a given spacing λ. For a given reference case bathymetry (λ= 200 m), rip current circulations retain floating material at a hourly rate R of about 80 % which is in line with most existing field and laboratory studies in similar settings. The influence of a Surf Zone rip-channel morphology on Surf Zone retention is evaluated by a number of morphologic parameters. Results show that rip spacing is important. The ratio of the Surf Zone width X s to rip spacing λ controls Surf Zone retention with R rapidly increasing with increasing X s /λ up to a threshold of about 1 above which R levels off to become asymptotic to 100 %. The impact of the presence of a rip head bar is profound but nonlinear. The onset of wave breaking across the rip head bar drives a weak seaward located circulation providing major pathways for Surface water exiting the Surf Zone compartment. Additional simulations suggest that alongshore variations in the offshore bathymetry are important. Patterns in the wave field enforced by wave refraction and potentially wave breaking across offshore bathymetric anomalies can provide a conduit for transporting floating material out of the Surf Zone and into the inner shelf region. This has major implications for Surf Zone flushing by inner-bar rips on multiple-barred beaches and on beaches facing bathymetric anomalies on the inner shelf.
Alan L. Shanks - One of the best experts on this subject based on the ideXlab platform.
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Surf-Zone hydrodynamics alter phytoplankton subsidies affecting reproductive output and growth of tidal filter feeders.
Ecology, 2018Co-Authors: Carlissa D. Salant, Alan L. ShanksAbstract:Surf Zones, classified from reflective to dissipative, separate the ocean from shore and subsidies from the coastal ocean must pass through Surf Zones to reach the shore. We have observed that variations in phytoplankton concentrations in the water over the intertidal Zone varied with Surf-Zone hydrodynamics and we hypothesized that this variation would alter growth rates, population structure, and reproductive output of Mytilus californianus and Balanus glandula. From May 2016 to April 2017, along 7 km of Cape Arago, Oregon, USA Surf-Zone phytoplankton concentrations were determined weekly at nine sites with varying Surf-Zone hydrodynamics as indicated by Surf-Zone widths. Throughout the year, concentrations of phytoplankton in wider, more dissipative Surf Zones were, on average, 16× higher than in narrow, more reflective Surf Zones. Similar to previous observations, Surf-Zone width explained >90% of the variability in phytoplankton concentrations in the Surf-Zone. On average, ~83% of B. glandula had egg lamellae at more dissipative shores compared to only 8% at more reflective. An index of potential reproductive output by barnacle populations as measured by ash free dry mass (AFDM) of egg lamellae was ~243× larger at more dissipative than at reflective shores and Surf-Zone phytoplankton concentrations and Surf-Zone width explained ~96 and 92% of the variability in this index. On average, density of M. californianus was ~2× higher at more reflective shores, but 60% of these individuals were smaller and non-reproductive compared to only 24% at the more dissipative sites. The gonad tissue mass/m2 of medium sized mussels was ~5× greater at more dissipative than reflective shores. Surf-Zone phytoplankton concentrations and Surf-Zone width explained ~80% and 65% of the variability in individual mussel gonad mass and ~69% and 56% of the variability in mussel population gonad mass, respectively. M. californianus were out-planted to assess growth rates and, after 5 months, average body mass was ~3× greater at more dissipative than reflective shores. Surf-Zone phytoplankton concentrations and width explained ~85% and 92% of the mass increase, respectively. Phytoplankton subsidies varied with Surf-Zone hydrodynamics altering the growth and reproductive output of two ecologically important intertidal filter feeders.
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Persistent Differences in Horizontal Gradients in Phytoplankton Concentration Maintained by Surf Zone Hydrodynamics
Estuaries and Coasts, 2018Co-Authors: Alan L. Shanks, Jamie Macmahan, Jenna Brown, Steven G Morgan, Ad J.h.m. Reniers, Atsushi Fujimura, Marley Jarvis, Lisa Ziccarelli, Chris GriesemerAbstract:Surf Zones, regions of breaking waves, are at the interface between the shore and coastal ocean. Surf Zone hydrodynamics may affect delivery of phytoplankton subsidies to the intertidal Zone. Over a month of daily sampling at an intermediate Surf Zone with bathymetric rip currents and a reflective Surf Zone, we measured Surf Zone hydrodynamics and compared concentrations of coastal phytoplankton taxa in the Surf Zones to concentrations offshore. At the intermediate Surf Zone, ~80% of the variability in the concentration of coastal phytoplankton taxa within the Surf Zone was explained by their variation offshore; however, concentrations were much higher and lower than those offshore in samples from a bathymetric rip current and over the adjacent shoal, respectively. Hydrodynamics at this intermediate Surf Zone did not hinder the delivery of coastal phytoplankton to the Surf Zone, but the bathymetric rip current system appeared to redistribute phytoplankton concentrating them within eddies. At the reflective shore, we sampled Surf Zones at a beach and two adjacent rocky intertidal sites. Concentrations of typical coastal phytoplankton taxa were usually an order of magnitude or more lower than those offshore, even when offshore samples were collected just 20 m beyond the breakers. The phytoplankton assemblages inside and outside the Surf Zone often appeared to be disconnected. Surf Zone hydrodynamics at the steep, reflective shore coupled with low phytoplankton concentrations in near-Surface water appeared to limit delivery of phytoplankton subsidies to the Surf Zone. Surf Zone hydrodynamics may be a key factor in the alongshore variation in phytoplankton subsidies to coastal communities.
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Planktonic Subsidies to Surf-Zone and Intertidal Communities
Annual Review of Marine Science, 2017Co-Authors: Steven G Morgan, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Falk FeddersenAbstract:Plankton are transported onshore, providing subsidies of food and new recruits to Surf-Zone and intertidal communities. The transport of plankton to the Surf Zone is influenced by wind, wave, and tidal forcing, and whether they enter the Surf Zone depends on alongshore variation in Surf-Zone hydrodynamics caused by the interaction of breaking waves with coastal morphology. Areas with gently sloping shores and wide Surf Zones typically have orders-of-magnitude-higher concentrations of plankton in the Surf Zone and dense larval settlement in intertidal communities because of the presence of bathymetric rip currents, which are absent in areas with steep shores and narrow Surf Zones. These striking differences in subsidies have profound consequences; areas with greater subsidies support more productive Surf-Zone communities and possibly more productive rocky intertidal communities. Recognition of the importance of spatial subsidies for rocky community dynamics has recently advanced ecological theory, and inco...
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Planktonic Subsidies to Surf-Zone and Intertidal Communities
Annual review of marine science, 2017Co-Authors: Steven G Morgan, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Falk FeddersenAbstract:Plankton are transported onshore, providing subsidies of food and new recruits to Surf-Zone and intertidal communities. The transport of plankton to the Surf Zone is influenced by wind, wave, and tidal forcing, and whether they enter the Surf Zone depends on alongshore variation in Surf-Zone hydrodynamics caused by the interaction of breaking waves with coastal morphology. Areas with gently sloping shores and wide Surf Zones typically have orders-of-magnitude-higher concentrations of plankton in the Surf Zone and dense larval settlement in intertidal communities because of the presence of bathymetric rip currents, which are absent in areas with steep shores and narrow Surf Zones. These striking differences in subsidies have profound consequences; areas with greater subsidies support more productive Surf-Zone communities and possibly more productive rocky intertidal communities. Recognition of the importance of spatial subsidies for rocky community dynamics has recently advanced ecological theory, and incorporating Surf-Zone hydrodynamics would be an especially fruitful line of investigation.
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Alongshore variation in barnacle populations is determined by Surf Zone hydrodynamics
Ecological Monographs, 2017Co-Authors: Alan L. Shanks, Jamie Macmahan, Steven G Morgan, Ad ReniersAbstract:Author(s): Shanks, AL; Morgan, SG; MacMahan, J; Reniers, AJHM | Abstract: © 2017 by the Ecological Society of America Larvae in the coastal ocean are transported toward shore by a variety of mechanisms. Crossing the Surf Zone is the last step in a shoreward migration and Surf Zones may act as semipermeable barriers altering delivery of larvae to the shore. We related variation in the structure of intertidal barnacle populations to Surf Zone width (Surf Zone hydrodynamics proxy), wave height, alongshore wind stress (upwelling proxy), solar radiation, and latitude at 40 rocky intertidal sites from San Diego, California to the Olympic Peninsula, Washington. We measured daily settlement and weekly recruitment of barnacles at selected sites and related these measures to Surf Zone width. Chthamalus density varied inversely with that of Balanus, and the density of Balanus and new recruits was negatively related to solar radiation. Across the region, long-term mean wave height and an indicator of upwelling intensity and frequency did not explain variation in Balanus or new recruit densities. Balanus and new recruit densities, daily settlement, and weekly recruitment were up to three orders of magnitude higher at sites with wide (g50 m), more dissipative Surf Zones with bathymetric rip currents than at sites with narrow (l50 m) more reflective Surf Zones. Surf Zone width explained 30–50% of the variability in Balanus and new recruit densities. We sampled a subset of sites l5 km apart where coastal hydrodynamics such as upwelling should be very similar. At paired sites with similar Surf Zone widths, Balanus densities were not different. If Surf Zone widths at paired sites were dissimilar, Balanus densities, daily settlement, and weekly recruitment were significantly higher at sites with the wider, more dissipative Surf Zone. The primary drivers of Surf Zone hydrodynamics are the wave climate and the slope of the shore and these persist over time; therefore site-specific stability in Surf Zone hydrodynamics should result in stable barnacle population characteristics. Variations in Surf Zone hydrodynamics appear to play a fundamental role in regulating barnacle populations along the open coast, which, in turn, may have consequences for the entire intertidal community.
Bruno Castelle - One of the best experts on this subject based on the ideXlab platform.
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Non-hydrostatic, non-linear processes in the Surf Zone
Journal of Geophysical Research. Oceans, 2020Co-Authors: Kévin Martins, Philippe Bonneton, Arthur Mouragues, Bruno CastelleAbstract:• Sub-Surface pressure and lidar data are used to study the non-linear and nonhydrostatic character of Surf Zone waves • Non-hydrostatic effects are strong even in the inner Surf Zone, where broken waves are sharp-crested and have a steep front • Oscillatory flow under broken waves is dominated by irrotational motions
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Bathymetric control of Surf Zone retention on a rip-channelled beach
Ocean Dynamics, 2014Co-Authors: Bruno Castelle, Ad Reniers, Jamie MacmahanAbstract:Simulations from a numerical model address the impact of nearshore morphology on Surf Zone retention on, open coast, rip-channelled beaches exposed to shore-normal waves. In the model, rip channels are regularly spaced alongshore with a given spacing λ. For a given reference case bathymetry (λ= 200 m), rip current circulations retain floating material at a hourly rate R of about 80 % which is in line with most existing field and laboratory studies in similar settings. The influence of a Surf Zone rip-channel morphology on Surf Zone retention is evaluated by a number of morphologic parameters. Results show that rip spacing is important. The ratio of the Surf Zone width X s to rip spacing λ controls Surf Zone retention with R rapidly increasing with increasing X s /λ up to a threshold of about 1 above which R levels off to become asymptotic to 100 %. The impact of the presence of a rip head bar is profound but nonlinear. The onset of wave breaking across the rip head bar drives a weak seaward located circulation providing major pathways for Surface water exiting the Surf Zone compartment. Additional simulations suggest that alongshore variations in the offshore bathymetry are important. Patterns in the wave field enforced by wave refraction and potentially wave breaking across offshore bathymetric anomalies can provide a conduit for transporting floating material out of the Surf Zone and into the inner shelf region. This has major implications for Surf Zone flushing by inner-bar rips on multiple-barred beaches and on beaches facing bathymetric anomalies on the inner shelf.
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Surf Zone flushing on embayed beaches
Geophysical Research Letters, 2013Co-Authors: Bruno Castelle, Giovanni CocoAbstract:[1] Using a numerical model, we show that the Surf Zone of embayed beaches systematically flushes out more floating material (simulated using passive tracers) than on open beaches, with most exits occurring through the headland rips. For obliquely incident waves, a headland rip acts as a persistent conduit for transporting floating material out of the Surf Zone and into the inner shelf region. Wave angle and embayment size determine which headland rip (upwave or downwave) flushes out more the Surf Zone material. For narrow embayed beaches, passive drifters exit the Surf Zone through the upwave headland rip. For wider embayed beaches, the longshore current has enough room to develop and is further deflected against the downwave headland where most drifters exit the Surf Zone. Our results indicate that wave-exposed rugged coasts strongly enhance exchange of floating matter (e.g., pollutants and nutrients) at the ocean/continent interface.
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Surf Zone retention in a laboratory rip current
Journal of Coastal Research, 2011Co-Authors: Bruno Castelle, Hervé Michallet, Vincent Marieu, Philippe BonnetonAbstract:Castelle, B., Michallet, H., Marieu, V. and Bonneton, P., 2011. Surf Zone retention in a laboratory rip current. Journal of Coastal Research, SI 64 (Proceedings of the 11th International Coastal Symposium), �� – ��. Szczecin, Poland, ISSN 0749-0208 Field and numerical studies recently challenged the traditional paradigm of rip currents systems that states that rip currents produce a continuous interchange of waters between the Surf Zone and shelf. Instead it is suggested tha t ri p current flow fields consist of semi-enclosed, large-scale vortices that retain floating material (e.g. drifters) at a rate of about 80-90%. In this paper is presented a laboratory rip current experiment over eight contrasting nature-like beach morphologies involving deployment of a large number of drifters. When the rip current was symmetric over a typical bar and rip morphology (4 out of the 8 cases), only about 10% of the drifters entering the rip exited the Surf Zone, whereas when the mean rip current was asymmetric, more drifters (~30-45%) entering in the rip exited the Surf Zone compartment. Drifters exiting the Surf Zone compartment were not systematically caught by a pulsating jet. More frequently, these drifters were likely caught in a vortex being shed offshore, as they often looped track in the vicinity of the rip head before exiting the SurfZone compartment. This confirms new thoughts on rip currents that are very important from the perspective of both mixing in the nearshore and beach safety: rip currents systems only sporadically produce intense interchange between the waters of the Surf Zone and the shelf. Results additionally suggest that asymmetric rip current retain less floating material than symmetric rip currents.
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Surf Zone retention in a laboratory rip current
Journal of Coastal Research, 2011Co-Authors: Bruno Castelle, Hervé Michallet, Vincent Marieu, Philippe BonnetonAbstract:Field and numerical studies recently challenged the traditional paradigm of rip currents systems that states that rip currents produce a continuous interchange of waters between the Surf Zone and shelf. Instead it is suggested that rip current flow fields consist of semi-enclosed, large-scale vortices that retain floating material (e.g. drifters) at a rate of about 80-90%. In this paper is presented a laboratory rip current experiment over eight contrasting nature-like beach morphologies involving deployment of a large number of drifters. When the rip current was symmetric over a typical bar and rip morphology (4 out of the 8 cases), only about 10% of the drifters entering the rip exited the Surf Zone, whereas when the mean rip current was asymmetric, more drifters (~30-45%) entering in the rip exited the Surf Zone compartment. Drifters exiting the Surf Zone compartment were not systematically caught by a pulsating jet. More frequently, these drifters were likely caught in a vortex being shed offshore, as they often looped track in the vicinity of the rip head before exiting the SurfZone compartment. This confirms new thoughts on rip currents that are very important from the perspective of both mixing in the nearshore and beach safety: rip currents systems only sporadically produce intense interchange between the waters of the Surf Zone and the shelf. Results additionally suggest that asymmetric rip current retain less floating material than symmetric rip currents.