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Surfzone mixing and transport on a sandy, steep (∼1/8 slope), reflective beach at Carmel River State Beach, California, are described for a range of wave and alongshore flow conditions. Depth-limited wave breaking occurred close to the shore due to the steepness of the beach, creating a narrow surf/swash zone (∼10 m wide). Fluorescent Rhodamine dye was released as a slug in the surfzone, and the temporal and spatial evolution was measured using in-situ dye sensors. Dye concentration measured as a function of time reveals sharp fronts that quickly decay resulting in narrow peaks near the dye release, which subsequently broaden and decrease in peak concentration with alongshore distance. The measurements indicate two stages of mixing and transport occur inside the surfzone on the steep beach. 1) In the near-field (50 m downstream from the dye release location), the mass transport was dominated by advection. The distance to the far-field is much shorter in the alongshore on a steep beach compared with a dissipative beach. Estimates of cross-shore and alongshore diffusion coefficients (κ x , κ y ) were found to be similar in magnitude within the surfzone. Outside the surfzone in the far-field, the results suggest that the mixing processes are independent of those inside the surfzone. The mixing and transport of material observed on this steep beach are found to be analogous to that previously measured on dissipative beaches, however the diffusion coefficients within and outside the surfzone were found to be smaller on this steep beach.

Understanding the conditions that drive variation in recruitment of key estuarine species can be important for effective conservation and management of their populations. The Olympia oyster (Ostrea lurida) is native to the Pacific coast of North America and has been a target of conservation efforts, though relatively little information on larval recruitment exists across much of its range. This study examined the recruitment of Olympia oysters at biweekly to monthly intervals at four sites in northern San Francisco Bay from 2010 to 2015 (except 2013). Mean monthly temperatures warmed at all sites during the study, while winter (January–April) mean monthly salinity decreased significantly during a wet year (2011), but otherwise remained high as a result of a drought. A recurring peak in oyster recruitment was identified in mid-estuary, in conditions corresponding to a salinity range of 25–30 and >16 °C at the time of settlement (April–November). Higher average salinities and temperatures were positively correlated with greater peak recruitment. Interannual variation in the timing of favorable conditions for recruitment at each site appears to explain geographic and temporal variation in recruitment onset. Higher winter/spring salinities and warmer temperatures at the time of recruitment corresponded with earlier recruitment onset within individual sites. Across all sites, higher winter/spring salinities were also correlated with earlier onset and earlier peak recruitment. Lower winter salinities during 2011 also resulted in a downstream shift in the location of peak recruitment.

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.

Surf zone hydrodynamics vary along shorelines potentially affecting the delivery of larvae and zooplankton subsidies to intertidal communities, and, hence, the intensity of postsettlement interactions, growth and reproduction of filter-feeding foundation species and planktivorous fishes. We investigated the ability of zooplankton assemblages to enter the wide surf zone of the rip-channeled, more dissipative beach at Sand City, California, and the narrow surf zone of the steep reflective beach at nearby Carmel River State Beach. Every day for a month, we surveyed zooplankton inside and outside the surf zone and concomitant larval settlement of the dominant invertebrate onshore at each site in this upwelling regime. At the more dissipative surf zone, all zooplankters were far more concentrated inside than outside the surf zone. Many taxa increased in the surf zone and the predominant invertebrate on beaches, Emerita analoga, settled abundantly when prevailing northwesterly winds relaxed and waves were small. At the reflective surf zone, concentrations of zooplankters of most taxa were far greater outside than inside the surf zone, and many taxa increased in the surf zone when waves were small. Twice as many taxa were positively correlated inside and outside the surf zone at the dissipative than the reflective surf zone, indicating that zooplankters were more freely exchanged although behavior also played a role. Thus, spatial and temporal variation in surf zone hydrodynamics may regulate subsidies of zooplankton food and larval recruits to nearshore communities with potential cascading effects on community dynamics and structure.

Recruitment of marine fishes is largely determined by biological and environmental factors acting on early-life stages. Subtle changes in larval condition in response to their environment can result in order-of-magnitude differences in year-class-strength. Overlap of larval production and favorable feeding conditions drives recruitment for many temperate marine fishes, but challenges associated with studying marine larvae have made it difficult to assess how environmental processes act on individual larvae to affect their growth and survival. We conducted a 2-yr study in an upwelling system to assess the influence of regional productivity, temperature, and larval condition in explaining growth in rockfishes (Sebastes spp.). We employed otolith microstructure and satellite imagery to measure initial larval growth and estimate the productivity and temperature experienced by individuals to determine their relative importance in subsequent growth at metamorphosis. We compared model performance using indexed environmental conditions scaled over three different regions. In both years, net primary productivity explained the most variation in pre-metamorphic growth relative to temperature and initial growth. This relationship was consistent across spatial regions, although model fit was highest using indices scaled to the south continental shelf region. Recent settlement, juvenile recruitment, and individual growth were significantly higher in a year when productivity bloomed earlier and individual larvae experienced higher levels of productivity. Thus, this link between regional scale productivity, growth, and subsequent year-class strength supports the hypothesis that large-scale oceanographic processes stimulating upwelling and secondary production are primary drivers of larval growth and recruitment in rockfishes.

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 rip-channeled 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. © 2014, by the Association for the Sciences of Limnology and Oceanography, Inc.

The effectiveness of larval behavior in regulating transport between well-mixed, low-inflow estuaries and coastal waters in seasonally arid climates is poorly known. We determined the flux of an assemblage of benthic crustacean larvae relative to physical conditions between a shallow estuary and coastal waters on the upwelling coast of northern California (38°18′N, 123°03′W) from 29 to 31 March 2006. We detected larval behaviors that regulate transport in adjacent coastal waters and other estuaries for only two taxa in the low-inflow estuary, but they were apparent for taxa outside the estuary. Vertical mixing in the shallow estuary may have overwhelmed larvae of some species, or salinity fluctuations may have been too slight to cue tidal vertical migrations. Nevertheless, all larval stages of species that complete development in nearshore coastal waters were present in the estuary, because they remained low in the water column reducing seaward advection or they were readily exchanged between the estuary and open coast by tidal flows. Weak tidal flows and gravitational circulation at the head of the estuary reduced seaward transport during development for species that completed development nearshore, whereas larval release during nocturnal ebb tides enhanced seaward transport for species that develop offshore. Thus, nonselective tidal processes dominated larval transport for most species back and forth between the low-inflow estuary and open coastal waters, whereas in adjacent open coastal waters, larval behavior in the presence of wind-induced shear was more important in regulating migrations between adult and larval habitats along this upwelling coast. © 2014 Coastal and Estuarine Research Federation.

We capitalized on a long-term record of larval recruitment and a distinctive oceanographic signature to reveal how changes in ocean conditions affect larval advection, behavior, and recruitment in a region of strong, persistent upwelling and recruitment limitation. We repeatedly sampled the vertical and horizontal distribution of a larval assemblage and ocean conditions during infrequent relaxations of prevailing upwelling winds near Bodega Bay, California. During prolonged relaxation events, a poleward, coastal, boundary current imported low-salinity surface waters that were devoid of larvae to the study area. The resident larval assemblage was restricted to cold, saline, bottom waters and pushed offshore while diel vertical migrations were suppressed. Hence, changes in oceanographic conditions strongly affected behaviorally mediated larval distributions, revealing the reason that few species recruit during relaxation events in this region. During relaxation events in upwelling regions, poleward coastal boundary currents will force larvae offshore throughout the water column at small headlands and in seaward-flowing bottom currents at straight coastlines, but recruitment may decrease markedly only near estuaries where few larvae will arrive in low-salinity surface waters. Targeted profiling of larval assemblages complements widespread monitoring of recruitment from shore and is necessary to determine how changing ocean conditions affect larval distributions, recruitment dynamics, and the connectivity of populations. © 2012, by the Association for the Sciences of Limnology and Oceanography, Inc.

We surveyed crustacean larvae in the plankton in the lee of Bodega Head, California, for 2 months during late spring and summer and cross-correlated the larval abundance and stage of development of 16 taxa with 8 indicators of upwelling-relaxation conditions. Larvae in all stages of development for 11 of these taxa were entrained and accumulated in a recirculation feature in Bodega Bay, found in the lee of this small headland as soon as upwelling-favorable winds began, and persisted until winds weakened. The remaining taxa were more prevalent during relaxation events when the recirculation feature dissipated and a poleward coastal current transported larvae into and through the bay. During upwelling conditions, a vertically sheared flow occurs in the lee of the headland that accounts for the accumulation of plankton. However, larval behavior did not have a substantial effect on density and persistence in the lee of the headland, regardless of whether taxa were more prevalent during upwelling or relaxation conditions or whether they developed entirely nearshore or migrated offshore later in development. Thus, larvae and postlarvae of many, diverse taxa are concentrated in the plankton in the lee of small headlands in upwelling areas, which is consistent with previously reported recruitment hot spots in small upwelling bays. These headland-related hot spots increase spatial structure in population density and community structure in recruitment-limited upwelling regions and other wind-driven coasts. © 2011, by the American Society of Limnology and Oceanography, Inc.

Advantages of dispersal on the scales that are possible in a long pelagic larval period are not apparent, even for benthic species. An alternative hypothesis is that wide dispersal may be an incidental byproduct of an ontogenetic migration from and then back to the parental habitat. Under this hypothesis, the water column is a better habitat than the bottom for early development. Because the parental area is often an especially favorable habitat for juveniles and adults, selection may even favor larval retention or larval return rather than dispersal. Where larval capabilities and currents permit, a high percentage of recruits may then be produced from local adults. Expected consequences of a high proportion of local recruitment are stronger links between stock and recruitment, greater vulnerability to recruitment overfishing and local modifications of habitat, greater local benefits from fishery reserves, and possibly more localized adaptation within populations. Export of some larvae is consistent with a high proportion of retained or returning larvae, could stabilize populations linked by larval exchange, and provide connectivity between marine reserves. Even a small amount of larval export could account for the greater gene flow, large ranges, and long evolutionary durations seen in species with long pelagic larval stages.

The uptake, assimilation, and retention of Se, Co, Ag, Ce, Eu, and Gd by crustacean larvae were measured to assess the suitability of these elements as tags for determining larval dispersal patterns and mortality rates. Gamma-emitting radioisotopes were used to determine the uptake and retention of each element by larvae of three crabs, Dyspanopeus sayi, Uca pugnax, and Sesarma reticulatum, and one barnacle, Semibalanus balanoides. Selenium was readily taken up by larvae from their food, was assimilated at efficiencies of 61-93%, was retained at concentrations detectable above background levels for weeks, and did not consistently affect larval survival or development in the laboratory. The other elements were not absorbed sufficiently from food or were not retained long enough to serve as appropriate tags for monitoring larval dispersal. Thus, only Se seemed to be transferred efficiently between trophic levels and is suitable as a larval tag.

Unlike most zooplankters, larvae of decapod crustaceans and fish often are pigmented and may hatch and ascend to the sea surface during the day. Chromatophores possibly protect these larvae from ultraviolet radiation (UVR), but may increase their visibility to planktivorous fish. We exposed larvae of four species of tropical crabs to sunlight and to planktivorous fish in the field to address this paradox. Most lightly pigmented larvae of three species died from exposure to sunlight within 1 d, and 94- 97.5% of them died after 2 d. The more darkly pigmented Pachygrapsus transversus larvae survived significantly better; only 57% of them died after 2 d of exposure to sunlight. These darkly pigmented larvae survived encounters with fish as well as or better than larvae of two other species that did not have large melanophores. Larval chromatophore systems may block UVR without greatly increasing the visibility of larvae to fish. Larvae that migrate from adult habitats to nursery grounds in surface waters throughout the day likely have chromatophore systems that are effective against both of these countervailing selective pressures; however, increasing UVR may stress larvae. The timing of larval release relative to the diel cycle was not related to the susceptibility of larvae to photodamage.

Specimens of the larval crustacean genus Cerataspis were found during analysis of the stomach contents of pelagic fishes from the North Atlantic; 87% of the specimens collected were C. monstrosa, 13% C. petiti. Surface-feeding skipjack tuna Katsuwonus pelamis, yellowfin tuna Thunnus albacares, blackfin funa T. atlanticus and dolphin Coryphaena hippurus preyed upon the last 3 mysis stages of Cerataspis. Yellowfin and skipjack tunas accounted for 95% of the Cerataspis collected. Fishes feeding around Sargassum are more likely to feed on Cerataspis as evidenced by co-occurrence of the crustaceans and algae in the stomachs. Cerataspis are opportunistically preyed upon when encountered. C. petiti have a nearly circumglobal distribution between 40oN and 40oS. -from Authors