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Jamie Macmahan - 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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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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field observations of Surf zone inner shelf exchange on a rip channeled beach
Journal of Physical Oceanography, 2015Co-Authors: Jenna Brown, Jamie Macmahan, A J H M Reniers, Edward B ThorntonAbstract:Cross-shore exchange between the Surf zone and the inner shelf is investigated using Lagrangian and Eulerian field measurements of rip current flows on a rip-channeled beach in Sand City, California. Surface drifters released on the inner shelf during weak wind conditions moved seaward due to rip current pulses and then returned shoreward in an arcing pattern, reentering the Surf zone over shoals. The cross-shore velocities of the seaward- and shoreward-moving drifters were approximately equal in magnitude and decreased as a function of distance offshore. The drifters carried seaward by the rip current had maximum cross-shore velocities as they exited the Surf zone and then decelerated as they moved offshore. The drifters moving shoreward accelerated as they approached the Surfzone boundary with maximum cross-shore velocities as they reentered the Surf zone over shoals. It was found that Stokes drift was not solely responsible for the onshore transport across the Surfzone boundary. The cross-shore diffusivity on the inner shelf was greatest during observations of locally contained cross-shore exchange. These field observations provide evidence that the cross-shore exchange between the Surf zone and inner shelf on a rip-channeled beach is due to wave-driven rip current circulations and results in Surface material being contained within the nearshore region.
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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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Numerical simulations of larval transport into a rip-channeled Surf zone
Limnology and Oceanography, 2014Co-Authors: Atsushi Fujimura, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Claire B Paris, Steven G MorganAbstract:Competent larvae of intertidal invertebrates have to migrate toward shore for settlement; however, their migration through the Surf zone is not understood. We investigated larval transport mechanisms at a ripchanneled beach. Because tracking larvae in the Surf zone is infeasible, we used a three-dimensional biophysical model to simulate the processes. The coupled model consists of a physical module for currents and waves, and a biological module for adding larval traits and behaviors as well as Stokes drift to Lagrangian particles. Model calculations were performed with and without onshore wind forcing. Without wind, wave-driven onshore streaming occurs in the bottom boundary layer outside the Surf zone. With onshore wind, onshore currents occur near the Surface. In the Surf zone, offshore-directed rip currents and compensating onshore-directed currents over shoals are formed in both no-wind and wind cases. In the biological module, neutral, negative, and positive buoyant particles were released offshore. Additionally, particles either sank in the presence of turbulence or not. Two scenarios achieved successful onshore migration: Negatively buoyant larvae without wind forcing sink in the turbulent bottom boundary layer and are carried onshore by streaming; positively buoyant larvae drift toward shore in wind-driven Surface currents to the Surf zone, then sink in the turbulent Surf zone and remain near the bottom while transported shoreward. In both cases, the larval concentration is highest in the rip channel, consistent with field data. This successful result is only obtained if turbulence-dependent sinking behavior and Stokes drift are included in the transport of larvae.
Mike Fried - One of the best experts on this subject based on the ideXlab platform.
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isolation and genomic analysis of the human Surf 6 gene a member of the Surfeit locus
Gene, 2000Co-Authors: Charalambos Magoulas, Mike FriedAbstract:Abstract The human Surfeit locus contains at least six tightly clustered genes (Surf-1 to Surf-6) of which five (Surf-1 to Surf-5) have been characterised and found not to share any sequence homology. The organisation and juxtaposition of the Surfeit genes are conserved between human and mouse. The Surf-6 gene that encodes a novel nucleolar-matrix protein with nucleic-acid binding properties has been characterised in mouse. In this work, we have isolated and analysed the human Surf-6 homologue and determined its genomic organisation in the Surfeit locus. The human Surf-6 gene has five exons spread over a distance of 4.3 kb and has features of a housekeeping gene being ubiquitously expressed, having its 5′ end located within a CpG rich island and lacking a canonical TATA box. The intragenic region between the 3′ end of the Surf-5 gene and the 5′ end of the Surf-6 gene is 3.2 kb and contains a pseudogene of the ribosomal protein gene rpL21. The putative human Surf-6 protein is 361 amino acids long and includes motifs found in both the mouse and fish Surf-6 homologues, which may underlie the functions of Surf-6. Three amino acid polymorphisms have been detected at codons 163, 175 and 311 by SSCP analysis.
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the human Surfeit locus
Genomics, 1998Co-Authors: Trevor Duhig, Christiana Ruhrberg, Mike FriedAbstract:The organization of the human Surfeit locus containing the six sequence-unrelated housekeeping genes Surf-1 to Surf-6 (HGMW-approved symbols Surf1-Surf6) has been determined. The human Surfeit locus occupies about 60 kb of DNA, and the tightly clustered gene organization and the juxtaposition of the human genes are similar to the mouse and chicken Surfeit loci with the 5' end of each gene associated with a CpG-rich island. Whereas in the mouse the Surf-2 and Surf-4 genes overlap at their 3' ends, the human Surf-2 and Surf-4 genes have been found to be separated by 302 bp due to a much shorter 3' untranslated region in the human Surf-2 gene. The distance between the 3' ends of the human Surf-1 and Surf-3 genes is 374 bp, and the distance between the 5' ends of the human Surf-3 and Surf-5 genes is only 112 bp. Unusually the human Surf-5 gene contains an intron in its 5' untranslated region not found in the mouse or rat Surf-5 genes. This additional intron is also found in the Surf-5 gene of both Old and New World monkeys, being generated before the divergence of human and prosimians but after the divergence of primates and rodents. A contig of 200 kb containing the human Surfeit locus has been constructed from overlapping cosmid, P1, and PAC clones. Approximately 40 kb proximal to the 3' end of the Surf-6 gene, the 5' region of the ABO glycosyltransferase gene has been detected. This allows us to determine the orientation of the Surfeit and ABO loci with respect to each other and to the telomere and centromere of human chromosome 9.
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the comparative genomic structure and sequence of the Surfeit gene homologs in the puffer fish fugu rubripes and their association with cpg rich islands
Genome Research, 1997Co-Authors: Niall Armes, Jonathan Gilley, Mike FriedAbstract:: The puffer fish Fugu rubripes (Fugu) has a compact genome approximately one-seventh the size of man, mainly owing to small intron size and the presence of few dispersed repetitive DNA elements, which greatly facilitates the study of its genes at the genomic level. It has been shown previously that, whereas the Surfeit genes are tightly clustered at a single locus in mammals and birds, the genes are found at three separate loci in the Fugu genome. Here, Fugu gene homologs of all six Surfeit genes (Surf-1 to Surf-6) have been cloned and sequenced, and their gene structure has been compared with that of their mammalian and avian homologs. The predicted protein products of each gene are well conserved between vertebrate species, and in most cases their gene structures are identical to their mammalian and avian homologs except for the Fugu Surf-6 gene, which was found to lack an intron present in the mouse gene. In addition, we have identified conserved regulatory elements at the 5' and 3' ends of the Surf-3/rpL7a gene by comparison with the mammalian and chicken Surf-3/rpL7a gene homologs, including the presence of a polypyrimidine tract at the extreme 5' end of this ribosomal protein gene. The Fugu Surfeit gene homologs appear to be associated with CpG-rich islands, like the Surfeit genes in higher vertebrates, but these Fugu CpG islands are similar to the nonclassical islands characteristic of other fish species. Our observations support the use of the Fugu genome to study vertebrate gene structure, to predict the structure of mammalian genes, and to identify vertebrate regulatory elements. [The sequence data described in this paper have been submitted to the data library under accession nos. Y15170 (Surf-2, Surf-4), Y15171 (Surf-3, Surf-1, Surf-6), and Y15172 (Surf-5.)]
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the organization and conservation of the human Surfeit gene cluster and its localization telomeric to the c abl and can proto oncogenes at chromosome band 9q34 1
Human Molecular Genetics, 1993Co-Authors: Tania A Jones, Ken Garson, Denise Sheer, Mike FriedAbstract:: The mouse Surfeit locus contains an unusually tight cluster of six housekeeping genes (Surf-1 to -6) which are unrelated by sequence homology. Using a mouse Surfeit locus probe, a 16 kb clone has been isolated which contains the human Surf-1 and Surf-3 genes and regions of the human Surf-2 and Surf-5 genes. The organization and juxtaposition of these human Surfeit locus genes are the same as found in the mouse. Using the human clone as a biotinylated probe for fluorescence in situ hybridization (FISH) we have confirmed the location of the human Surfeit locus to chromosome band 9q34. Metaphase spreads of human chronic myeloid leukemic cells containing the t(9;22)(q34;q11) translocation involving The c-abl gene at 9q34.1 an acute nonlymphocytic leukemic cells containing the t(6;9)(q34;p23) translocation involving the can gene at 9q34.1 were analyzed by FISH using the human Surfeit clone as a probe. These analyses locate the human Surfeit locus telomeric to the c-abl and can genes at chromosome band 9q34.1.
Alan L. Shanks - 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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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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Numerical simulations of larval transport into a rip-channeled Surf zone
Limnology and Oceanography, 2014Co-Authors: Atsushi Fujimura, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Claire B Paris, Steven G MorganAbstract:Competent larvae of intertidal invertebrates have to migrate toward shore for settlement; however, their migration through the Surf zone is not understood. We investigated larval transport mechanisms at a ripchanneled beach. Because tracking larvae in the Surf zone is infeasible, we used a three-dimensional biophysical model to simulate the processes. The coupled model consists of a physical module for currents and waves, and a biological module for adding larval traits and behaviors as well as Stokes drift to Lagrangian particles. Model calculations were performed with and without onshore wind forcing. Without wind, wave-driven onshore streaming occurs in the bottom boundary layer outside the Surf zone. With onshore wind, onshore currents occur near the Surface. In the Surf zone, offshore-directed rip currents and compensating onshore-directed currents over shoals are formed in both no-wind and wind cases. In the biological module, neutral, negative, and positive buoyant particles were released offshore. Additionally, particles either sank in the presence of turbulence or not. Two scenarios achieved successful onshore migration: Negatively buoyant larvae without wind forcing sink in the turbulent bottom boundary layer and are carried onshore by streaming; positively buoyant larvae drift toward shore in wind-driven Surface currents to the Surf zone, then sink in the turbulent Surf zone and remain near the bottom while transported shoreward. In both cases, the larval concentration is highest in the rip channel, consistent with field data. This successful result is only obtained if turbulence-dependent sinking behavior and Stokes drift are included in the transport of larvae.
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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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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Numerical simulations of larval transport into a rip-channeled Surf zone
Limnology and Oceanography, 2014Co-Authors: Atsushi Fujimura, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Claire B Paris, Steven G MorganAbstract:Competent larvae of intertidal invertebrates have to migrate toward shore for settlement; however, their migration through the Surf zone is not understood. We investigated larval transport mechanisms at a ripchanneled beach. Because tracking larvae in the Surf zone is infeasible, we used a three-dimensional biophysical model to simulate the processes. The coupled model consists of a physical module for currents and waves, and a biological module for adding larval traits and behaviors as well as Stokes drift to Lagrangian particles. Model calculations were performed with and without onshore wind forcing. Without wind, wave-driven onshore streaming occurs in the bottom boundary layer outside the Surf zone. With onshore wind, onshore currents occur near the Surface. In the Surf zone, offshore-directed rip currents and compensating onshore-directed currents over shoals are formed in both no-wind and wind cases. In the biological module, neutral, negative, and positive buoyant particles were released offshore. Additionally, particles either sank in the presence of turbulence or not. Two scenarios achieved successful onshore migration: Negatively buoyant larvae without wind forcing sink in the turbulent bottom boundary layer and are carried onshore by streaming; positively buoyant larvae drift toward shore in wind-driven Surface currents to the Surf zone, then sink in the turbulent Surf zone and remain near the bottom while transported shoreward. In both cases, the larval concentration is highest in the rip channel, consistent with field data. This successful result is only obtained if turbulence-dependent sinking behavior and Stokes drift are included in the transport of larvae.
Ad Reniers - One of the best experts on this subject based on the ideXlab platform.
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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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Numerical simulations of larval transport into a rip-channeled Surf zone
Limnology and Oceanography, 2014Co-Authors: Atsushi Fujimura, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Claire B Paris, Steven G MorganAbstract:Competent larvae of intertidal invertebrates have to migrate toward shore for settlement; however, their migration through the Surf zone is not understood. We investigated larval transport mechanisms at a ripchanneled beach. Because tracking larvae in the Surf zone is infeasible, we used a three-dimensional biophysical model to simulate the processes. The coupled model consists of a physical module for currents and waves, and a biological module for adding larval traits and behaviors as well as Stokes drift to Lagrangian particles. Model calculations were performed with and without onshore wind forcing. Without wind, wave-driven onshore streaming occurs in the bottom boundary layer outside the Surf zone. With onshore wind, onshore currents occur near the Surface. In the Surf zone, offshore-directed rip currents and compensating onshore-directed currents over shoals are formed in both no-wind and wind cases. In the biological module, neutral, negative, and positive buoyant particles were released offshore. Additionally, particles either sank in the presence of turbulence or not. Two scenarios achieved successful onshore migration: Negatively buoyant larvae without wind forcing sink in the turbulent bottom boundary layer and are carried onshore by streaming; positively buoyant larvae drift toward shore in wind-driven Surface currents to the Surf zone, then sink in the turbulent Surf zone and remain near the bottom while transported shoreward. In both cases, the larval concentration is highest in the rip channel, consistent with field data. This successful result is only obtained if turbulence-dependent sinking behavior and Stokes drift are included in the transport of larvae.
