Southern California Coast Research Articles

The Southern California Coast

The purpose of this map was to create a landscape view of my home region of Southern California that adequately displayed the complexity of it’s natural and man-made terrain. One of the challenges I faced was the amount of labeling in the greater Los Angeles (LA) area. I decided to not include any city borders because moving around LA feels more like moving across various neighborhoods and regions than crossing from one city to another. Slanting the text provided more space without making it too difficult to read. The orientation creates a more interesting layout than the usual north-up orientation, and allowed me to better restrict the map extent to the coast and inland cities. It did introduce a bathymetry challenge, as I had to include the islands and ocean in a way that suited the complexity of the land. I created a hillshade for the ocean floor to give it motion and shape; contour lines were filled with a deepening blue scale and blended together to provide depth. Other details include the shading used to subtly display elevation, the density of developed area, and vegetation and canopy density.

Community reorganization revealed by exploring shifts in the diet of an apex predator, the Golden Eagle Aquila chrysaetos, with stable isotopes and prey remains

Golden Eagles Aquila chrysaetos colonized the northern California Channel Islands, an archipelago located off the coast of southern California, USA, in the early 1990s, owing in part to the presence of Feral Pigs Sus scrofa. Eagles preyed on piglets and on the endemic Island Fox Urocyon littoralis, driving three endemic subspecies of the Island Fox (U. l. santacruzae, U. l. santarosae and U. l. littoralis) toward extirpation. Using stable isotopes (δ13C and δ15N) measured from feathers and blood of Golden Eagles and from meat and bone of their prey, along with the proportion of prey consumed estimated from nest excavations as informative priors, we show that shifts in Eagle isotopic signatures tracked community reorganization: when pigs and foxes were abundant, Eagles consumed them in higher proportions than other prey; when foxes became scarce owing to Eagle predation, Eagle diet shifted toward pigs, but also diversified to include Common Ravens Corvus corax and seabirds (Larus spp. and Phalacrocorax spp.); and finally, after pigs were eradicated and 35 Golden Eagles had been captured and removed from Santa Cruz Island, a lone remaining pair of Eagles reversed their diet to include more foxes. Our findings reveal that shifts in stable isotope signatures from tissues of an apex predator can be used as a general proxy to monitor changes in the prey community; however, if sample sizes are small, informative priors are both essential and overwhelmingly influential, and changes in abundance of preferred prey may mask or fail to reveal changes in less preferred prey. Given that apex predators are at the top of trophic hierarchies, that they are often important drivers of community structure and that they sample prey continuously from their community, isotopic signatures of their tissues may be useful for monitoring community change.

Net Community Production in a Productive Coastal Ocean From an Autonomous Buoyancy‐Driven Glider

AbstractNet community production (NCP), an analog of carbon export out of the surface ocean, is often estimated using budgets of dissolved oxygen. Accurate estimates of oxygen‐based NCP, especially in dynamic coastal regions, require constraints on vertical transport of water with O2 out of equilibrium with the atmosphere, nonsteady state change in the oxygen inventory, heating/cooling‐driven O2 disequilibrium, and the rate of bubble injection from wave activity. The latter two are typically evaluated by using discrete measurements of the O2/Ar ratio in lieu of O2 only. Because sophisticated sampling and measurement techniques are required to make these measurements, they are often limited in spatiotemporal resolution. However, high‐resolution estimates of NCP may be useful in determining small‐scale patchiness in export. In this study, we calculated high‐resolution NCP in coastal Southern California using dissolved oxygen measurements made by an autonomous buoyancy‐driven Slocum glider and an empirical relationship derived using discrete measurements of O2/Ar in the surface mixed layer to remove the influence of bubble injection, which accounted for approximately one fourth of the O2 supersaturation observed. Using estimates of vertical transport from wind speed‐based parameterizations, previously validated using a 7Be budget, we were able to correct for the physical biases to the signal, which are known to significantly influence dissolved oxygen budgets in this region. Our results agree well with previously published NCP estimates for the study area but also reveal higher‐frequency variability that discrete sampling was unable to resolve, suggesting that this approach may be useful in other regions with well‐constrained vertical transport rates.

Molecular evidence for the retention of the Thaumatopsyllidae in the order Cyclopoida (Copepoda) and establishment of four suborders and two families within the Cyclopoida

The classification of the Thaumatopsyllidae within the Copepoda has been an issue of ongoing discussion since the discovery of Thaumatopsyllus paradoxus G.O. Sars, 1913 from the Norwegian coast. The family has been formally placed in the Monstrilloida, the Cyclopoida and even in its own order, the Thaumatopsylloida, based on different morphological criteria. We examined for the first time, the phylogenetic position of the Thaumatopsyllidae using gene sequences of 28S and 18S rRNA, as well as COI mtDNA, obtained from two thaumatopsyllid species occurring off the coast of southern California. We also fortuitously explored the phylogenetic relationships of the Cyclopoida in more detail than Khodami et al. (2017) by including a wider sample of key families such as the Erebonasteridae and Gisellinidae. Both Maximum Likelihood and Bayesian analyses revealed the Thaumatopsyllidae is nested in the Cyclopoida and is related to the marine Speleoithonidae. In addition, 16 families of the Cyclopoida are supported to be monophyletic, but surprisingly, the Cyclopidae is paraphyletic. The Cyclopicinidae is the first monophyletic offshoot of the cyclopoid tree, followed by two derived clades. The first clade contains a monophylum consisting of the Schminkepinellidae + Giselinidae which is sister to a clade including the monophyletic Erebonasteridae and all other poecilostome families. The second clade is divided into two main, well-supported family clusters. One includes the Cyclopidae encompassing two subfamilies (Eucylopinae and Cyclopinae), but unexpectedly the parasitic Lernaeidae cluster as a sister-group to the brackish water Halicyclops (subfamily Halicyclopinae) and the Euryteinae is the sister to all the rest of Cyclopidae s. l., making the Cyclopidae paraphyletic. To resolve this conundrum, we erected two families, Euryteidae and Halicyclopidae. The Cyclopidae s. str. retains the subfamilies Eucyclopinae and Cyclopinae, although our phylogeny does not support the reciprocal monophyly of these subfamilies. Our results support the gradual invasion of fresh water by the four families in this cluster. The highly supported monophyletic marine Euryteidae is the first offshoot followed by the brackish-water, free-living Halicyclopidae and the freshwater, parasitic Lernaeidae. The Cyclopidae fulfilled the colonization of freshwater bodies. The other clade of families comprises 12 monophyletic families recovered by our analysis, including the Pterinopsyllidae (at first offshoot), the Smirnovipinidae sister to the Hemicyclopinidae + Psammocyclopinidae, the Thaumatopsyllidae + Speleoithonidae, an undescribed family sister to the Archinotodelphyidae + Notodelphyidae and the Cyclopinidae sister to the Oithonidae + Cyclopettidae. We propose suborder ranks for each of the four main phylogenetic subdivisions of the Cyclopoida. These are named Cyclopicinida, Ergasilida, Cyclopida and Oithonida after the type genus of the oldest described family in the respective group.

The Effect of El Niño on Flood Damages in the Western United States

Abstract This paper quantifies insured flood losses across the western United States from 1978 to 2017, presenting a spatiotemporal analysis of National Flood Insurance Program (NFIP) daily claims and losses over this period. While considerably lower (only 3.3%) than broader measures of direct damages measured by a National Weather Service (NWS) dataset, NFIP insured losses are highly correlated to the annual damages in the NWS dataset, and the NFIP data provide flood impacts at a fine degree of spatial resolution. The NFIP data reveal that 1% of extreme events, covering wide spatial areas, caused over 66% of total insured losses. Connections between extreme events and El Niño–Southern Oscillation (ENSO) that have been documented in past research are borne out in the insurance data. In coastal Southern California and across the Southwest, El Niño conditions have had a strong effect in producing more frequent and higher magnitudes of insured losses, while La Niña conditions significantly reduce both the frequency and magnitude of losses. In the Pacific Northwest, the opposite pattern appears, although the effect is weaker and less spatially coherent. The persistent evolution of ENSO offers the possibility for property owners, policy makers, and emergency planners and responders that unusually high or low flood damages could be predicted in advance of the primary winter storm period along the West Coast. Within the 40-yr NFIP history, it is found that the multivariate ENSO index would have provided an 8-month look-ahead for heightened damages in Southern California.

An economic analysis of shipping costs related to potential changes in vessel operating procedures to manage the co-occurrence of maritime vessel traffic and whales in the Channel Islands region

The Channel Islands region off the coast of southern California provides habitat to endangered whale populations and is home to the nation's two busiest ports: Long Beach and Los Angeles. The increase in number, size, and speed of ocean going vessels raises the potential for lethal vessel strikes on whales, and potentially the recovery of whale populations. This vessel strike issue has prompted several suggested changes in vessel operations, including vessel re-routing and speed reductions, to reduce the occurrence and lethality of vessel strikes. However, these changes may affect vessel transit times and costs to the shipping industry. This study characterizes the 2015 maritime shipping industry within the Channel Islands region and estimates the shipping costs associated with five alternative vessel operating procedures. Results suggest that shipping costs will decrease with re-routing vessels (1.6%–3.4%), but increase with vessel speed reductions (1.3%–2.0%), and that these changes will vary significantly across vessel categories. These differences can be explained by predicted changes in transit time and fuel consumption. The results of this study will not only provide local and federal management with additional information on the possible effects of each vessel operating procedure, but also provide a well-detailed framework for conducting future analyses.

The Impact of Regime Shifts on Long‐Range Persistence and the Scaling of Sea Surface Temperature Off the Coast of California

AbstractWe employ power law scaling using Detrended Fluctuation Analysis to examine sea surface temperature (SST) in Monterey Bay and at Scripps Pier. SSTs from 1920 to 2014 provide the database. The data were first detrended to remove the annual cycle and long‐term trends. Next, Detrended Fluctuation Analysis was applied to the data to estimate the temporal scaling exponents (TSEs). El Niño–Southern Oscillation appeared to influence our scaling results at scales of 2.8 and 5.6 years, but this influence did not adversely affect the interpretation of the results that form the basis for this study. Next, 76‐year time series of TSEs were generated for the period from 1930 to 2005 using a 20‐year moving window. They reveal maxima during the 1930s and 1940s, significantly lower values during the 1950s and 1960s, and higher values from the 1970s to the early 1990s. The period of lower TSEs falls within a 30‐year window bounded by major regime shifts in 1945–1946 and 1976–1977, clearly suggesting a cause and effect relationship. Changes in the SSTs and coastal winds off southern California before and after these events further support this interpretation. Although the annual cycle at Scripps Pier far exceeds that at Pacific Grove, the scaling properties are similar. The TSEs at both locations converge toward unity at longer maximum timescales consistent with long‐range persistence and stationarity and with similar results obtained elsewhere in the North Pacific. Finally, we conclude that power law scaling can be an effective tool for detecting changes in system behavior.

Heterogeneity of Toxin-Producing Cyanobacteria and Cyanotoxins in Coastal Watersheds of Southern California

Freshwater and marine harmful algal blooms are expanding on a global scale. Recent reports of toxic events have sparked a growing awareness of the importance of cyanobacteria and cyanotoxins at the land-sea interface and estuaries in general. A recent survey in the Southern California Bight documented a wealth of cyanobacteria-dominated communities at a variety of locations. To gain further insight into these assemblages, we repeatedly sampled several sites with different proximity and degrees of connectivity to the Pacific Ocean in four coastal watersheds along the coast of southern California. Our findings revealed temporal and spatial heterogeneity in the occurrence of potential toxin-producing cyanobacteria and associated toxins. Multiple toxins were measured in 45% of all samples (and 25% of shellfish examined), including samples testing positive for anatoxin-a, cylindrospermopsin, three congeners of microcystins, or the eukaryotic toxin domoic acid. The ecosystems are hydrologically connected to the Pacific Ocean and provide a source of cyanotoxins to marine and estuarine environments. Collectively, potential toxin-producing cyanobacteria were prevalent at all study sites and appeared to persist throughout the year in some locations. These findings indicate a need for implementation of coordinated monitoring programs across the land-sea interface.

Predator-mediated effects of severe drought associated with poor reproductive success of a seabird in a cross-ecosystem cascade.

Despite the profound impacts of drought on terrestrial productivity in coastal arid ecosystems, only a few studies have addressed how drought can influence ecological cascades across ecosystem boundaries. In this study, we examine the consequences of rainfall pulses and drought that subsequently impact the breeding success of a threatened nocturnal seabird, the Scripps's Murrelet (Synthliboramphus scrippsi). On an island off the coast of southern California, the main cause of reduced nest success for one of their largest breeding colonies is egg predation by an endemic deer mouse (Peromyscus maniculatus elusus). Mice on the island have an opportunistic diet of primarily terrestrial sources, but drastic declines in terrestrial productivity from drought might be expected to increase their reliance on marine resources, including murrelet eggs. We compiled data on terrestrial and marine productivity between 1983 and 2013 to determine how conditions in these ecosystems influence murrelet nest success. We found that the severity of drought had the strongest negative impact on murrelet nest success. We calculated that the reduction in fecundity during drought years due to increased egg predation by mice was substantial enough to produce a declining population growth rate. Nest success was much higher under normal or high rainfall conditions, depending on whether oceanic conditions were favorable to murrelets. Therefore, the more frequent and severe drought that is projected for this region could lead to an increased risk of murrelet population decline on this island. Our study highlights the need for understanding how species interactions will change through the effects of increasing drought and altered rainfall regimes under global change.

Behavioral responses of individual blue whales (Balaenoptera musculus) to mid-frequency military sonar.

This study measured the degree of behavioral responses in blue whales (Balaenoptera musculus) to controlled noise exposure off the southern California coast. High-resolution movement and passive acoustic data were obtained from non-invasive archival tags (n=42) whereas surface positions were obtained with visual focal follows. Controlled exposure experiments (CEEs) were used to obtain direct behavioral measurements before, during and after simulated and operational military mid-frequency active sonar (MFAS), pseudorandom noise (PRN) and controls (no noise exposure). For a subset of deep-feeding animals (n=21), active acoustic measurements of prey were obtained and used as contextual covariates in response analyses. To investigate potential behavioral changes within individuals as a function of controlled noise exposure conditions, two parallel analyses of time-series data for selected behavioral parameters (e.g. diving, horizontal movement and feeding) were conducted. This included expert scoring of responses according to a specified behavioral severity rating paradigm and quantitative change-point analyses using Mahalanobis distance statistics. Both methods identified clear changes in some conditions. More than 50% of blue whales in deep-feeding states responded during CEEs, whereas no changes in behavior were identified in shallow-feeding blue whales. Overall, responses were generally brief, of low to moderate severity, and highly dependent on exposure context such as behavioral state, source-to-whale horizontal range and prey availability. Response probability did not follow a simple exposure-response model based on received exposure level. These results, in combination with additional analytical methods to investigate different aspects of potential responses within and among individuals, provide a comprehensive evaluation of how free-ranging blue whales responded to mid-frequency military sonar.

Propagation of future climate conditions into hydrologic response from coastal southern California watersheds

As a biodiverse region under a Mediterranean climate with a mix of highly developed and natural watersheds, coastal Santa Barbara County (SB), located in southern California, is susceptible to the hydrologic impacts of climate change. This study investigates the potential changes in hydro-meteorological variables in this region as well as their societal and ecological implications for projected climate conditions during the twenty-first century. Daily streamflow ensembles from 135 coastal watersheds for the period 2021–2100 are developed using the Hillslope River Routing (HRR) model forced with downscaled precipitation and temperature projections derived from 10 climate models in the Coupled Model Inter-Comparison Project, Phase 5, and two emission scenarios (Representative Concentration Pathways, RCP, 4.5 and 8.5). Analysis of the projected ensemble precipitation and streamflow series relative to historical conditions (1961–2000) shows (i) minimal change in annual precipitation (median change within ±3%); (ii) an altered seasonal rainfall distribution with a decrease in rainfall at the beginning of the rainy season (Oct–Dec), an increase during the Jan–Mar period, and a decrease at the end of the season (Apr–Jun); (iii) increases in the magnitude and frequency of large storms (> 36 mm/day) which combined with a shorter rainy season, lead to increases in annual peak flows; and (iv) the propagation of the altered precipitation characteristics resulting in nonlinear changes in the magnitude and variability of annual maximum discharges (i.e., mean, standard deviation, skew) impacting estimated return period discharges (e.g., estimated 100-year flood discharges for the period 2061–2100 under 8.5 increase by up to 185%). While these results are specific to southern coastal California, the nature of nonlinear hydrologic response to altered precipitation characteristics underscores the value of regional studies investigating potential impacts of climate projections on streamflow dynamics.

Hourly Analyses of the Large Storms and Atmospheric Rivers that Provide Most of California’s Precipitation in Only 10 to 100 Hours per Year

California is regularly impacted by floods and droughts, primarily as a result of too many or too few atmospheric rivers (ARs). This study analyzes a two-decade-long hourly precipitation dataset from 176 California weather stations and a 3-hourly AR chronology to report variations in rainfall events across California and their association with ARs. On average, 10-40 and 60-120 hours of rainfall in southern and northern California, respectively, are responsible for more than half of annual rainfall accumulations. Approximately 10-30% of annual precipitation at locations across the state is from only one large storm. On average, northern California receives 25-45 rainfall events annually (40-50% of which are AR-related). These events typically have longer durations and higher event-precipitation totals than those in southern California. Northern California also receives more AR landfalls with longer durations and stronger Integrated Vapor Transport (IVT). On average, ARs contribute 79%, 76%, and 68% of extreme-rainfall accumulations (i.e., top 5% events annually) in the north coast, northern Sierra, and Transverse Ranges of southern California, respectively. The San Francisco Bay Area terrain gap in the California Coast Range allows more AR water vapor to reach inland over the Delta and Sacramento Valley, and thus, influences precipitation in the Delta’s catchment. This is particularly important for extreme precipitation in the northern Sierra Nevada, including river basins above Oroville Dam and Shasta Dam. This study highlights differences between rainfall and AR characteristics in coastal versus inland northern California, differences that largely determine the regional geography of flood risks and water-reliability. These analyses support water resource, flood, levee, wetland, and ecosystem management within the catchment of the San Francisco estuary system by describing regional characteristics of ARs and their influence on rainfall on an hourly timescale.

Assessment of Topsoil Salvage and Seed Augmentation in the Restoration of Coastal Sage Scrub on Santa Catalina Island, California

The Catalina Island Conservancy manages over 22,000 acres of coastal (California) sage scrub (CSS) habitat off the coast of Southern California, including much of the infrastructure, roads, and recreation associated with habitat disturbance. Restoration trials were initiated to establish best management practices for roadside and disturbed site revegetation under local site conditions. Site treatments compared excavated native subsoil and surface soil (±20 cm) reapplication practices with and without seed augmentation. Evaluation of native and nonnative germinants indicated that salvaged surface soil alone may not be sufficient to restore native cover. Seeding improved native cover and reduced establishment of nonnative species on unirrigated sites. Evaluation of water potential of seedlings indicated that high-frequency irrigation may favor establishment of nonnative annual grasses. Most compelling for land managers is the indication that CSS habitats may contain a significant nonnative seed bank in spite of the composition of aboveground vegetation, such that disturbance may facilitate habitat-type conversion without seed augmentation or weed control.

Larval Food Limitation in a Speyeria Butterfly (Nymphalidae): How Many Butterflies Can Be Supported?

For herbivorous insects the importance of larval food plants is obvious, yet the role of host abundance and density in conservation are relatively understudied. Populations of Speyeria butterflies across North America have declined and Speyeria adiaste is an imperiled species endemic to the southern California Coast Ranges. In this paper, we study the link between the food plant Viola purpurea quercetorum and abundance of its herbivore Speyeria adiaste clemencei to better understand the butterfly’s decline and aid in restoration of this and other Speyeria species. To assess the degree to which the larval food plant limits adult abundance of S. a. clemencei in 2013, we compared adult population counts to population size predicted from a Monte Carlo simulation using data for number of V. pur. quercetorum plants, number of leaves per plant, and leaf area per plant, with lab estimates of leaf area consumed to reach pupal stage on the non-native host V. papilionacea. Results indicated an average estimate of 765 pupae (median = 478), with 77% of the distribution being <1000 pupae. However, this was heavily dependent on plant distribution, and accounting for the number of transect segments with sufficient host to support a pupa predicted 371 pupae. The adult population empirical estimate was 227 individuals (95% CI is 146 to 392), which lies near the first quartile of the simulated distribution. These results indicate that the amount of host available to larvae was more closely linked to adult abundance than the amount of host present, especially when considering assumptions of the analyses. The data also indicate that robust populations require host density well in excess of what is eaten by larvae, in combination with appropriate spacing, to mitigate factors such as competition, starvation from leaving host patches, or unrelated to food plant, such as mortality from drought, predators, parasites, or disease.

Vertical Profiles of the Wave-Induced Airflow above Ocean Surface Waves

AbstractAn analysis of coherent measurements of winds and waves from data collected during the ONR Southern California 2013 (SoCal2013) program from R/P FLIP off the coast of Southern California in November 2013 is presented. An array of ultrasonic anemometers mounted on a telescopic mast was deployed to resolve the vertical profile of the modulation of the marine atmospheric boundary layer by the waves. Spectral analysis of the data provides the wave-induced components of the wind velocity for various wind-wave conditions. Results show that the wave-induced fluctuations depend both on the spectral wave age and the normalized height , where c is the linear phase speed of the waves with wavenumber k and is the mean wind speed measured at the height z. The dependence on the spectral wave age expresses the sensitivity of the wave-induced airflow to the critical layer where . Across the critical layer, there is a significant change of both the amplitude and phase of the wave-induced fluctuations. Below the critical layer, the phase remains constant while the amplitude decays exponentially depending on the normalized height. Accounting for this double dependency, the nondimensionalization of the amplitude of the wave-induced fluctuations by the surface orbital velocity collapses all the data measured by the array of sonic anemometers, where a is the amplitude of the waves.

Southern California Coastal Response to the 2015–2016 El Niño

AbstractWidespread erosion associated with energetic waves of the strong 2015–2016 El Niño on the U.S. West Coast has been reported widely. However, Southern California was often sheltered from the northerly approach direction of the offshore waves. The few large swells that reached Southern California were not synchronous with the highest tides. Although west coast‐wide tidal anomalies were relatively large in 2015–2016, in Southern California, total water levels (sum of tides, anomalies, and wave superelevation) were lower than during the 1997–1998 Niño, and comparable to the 2009–2010 Niño. Airborne lidar surveys spanning 300 km of Southern California coast show the beach response varied from considerable erosion to accretion. On average, the shoreline moved landward 10 m, similar to the 2009–2010 El Niño. Some San Diego county beaches were narrower in the 1997–1998 El Niño than in 2015–2016, consistent with the higher erosion potential in 1997–1998. Beach retreat exceeded 80 m at a few locations. However, 27% of the shoreline accreted, often in pocket beaches, or near jetties. While adjacent beaches eroded, estuary mouths accreted slightly, and several estuaries remained or became closed during the study period. Only 12% of cliffs eroded (mostly at the base), and the average cliff face retreat was markedly less than historical values. Only two cliff‐top areas retreated significantly. Although some areas experienced significant change, the potential for coastal erosion and damage in Southern California was reduced compared to the 1997–1998 El Niño, because of low rainfall, a northerly swell approach, and relatively limited total high‐water levels.

High-resolution environmental magnetic study of a Holocene sedimentary record from Zaca Lake, California

Mineral magnetic studies of Holocene lake sediments recovered from Zaca Lake, in coastal southern California have yielded a 3000-year high-resolution record of terrestrial hydrologic variability and paleolimnology. Samples for magnetic analysis were obtained from an 8.73 m core recovered from the central region of Zaca Lake. Ages, constrained using a combined paleomagnetic and radiocarbon chronostratigraphy, yield sedimentation rates of 2–10 mm/yr with an average rate of 3 mm/yr over the 3000-year interval. Parameters reflecting decadal-scale variability in magnetic concentration (susceptibility, ARM, SIRM) and grain size (ARM/Chi) were measured every 2 cm. Additional rock magnetic tests on whole rock samples and magnetic separates indicate that magnetite and an iron sulfide are the chief magnetic carriers. Detailed analysis of the rock magnetic record reveals four major temporal intervals: 0–135 cm (~AD 2009–1757) the period of European settlement; 135–270 cm (~AD 1757–1275) the period of Native American, Chumash occupation of the watershed encompassing the bulk of the wet interval known as the little ice age (LIA); 270–600 cm (AD 1275–100) encompassing the drier Medieval Climate Anomaly (MCA); and 600–875 cm (2000–3000 ybp) an era dominated by a long interval of low magnetic mineral intensity and concentration that has been interpreted as a time of epic drought. Beginning with the cessation of drought conditions at Zaca Lake around ~2000 ybp, the magnetic proxy record of rock magnetic cyclicity and hydrologic variability shows a pronounced decadal to centennial-scale periodicity. We interpret these periodicities as oscillations between summer-dominated sedimentary sequences, characterized by whiting events with their resulting carbonate deposits, and winter dominated sedimentary sequences, typified by sulfide-rich clastics, reflecting lacustrine overturn and enhanced advection of detrital flux during winter storm events. The long-term variation of summer versus winter-dominated weather patterns reflects the climate variability of central California coast-ranges.

Morphological Divergence among Populations ofXantusia riversiana,a Night Lizard Endemic to the Channel Islands of California

Morphological variation between closely related island endemics offers a unique system to study ecological and evolutionary processes. The Island Night Lizard, Xantusia riversiana (Cope, 1883), is endemic to three of the Southern Channel Islands off the coast of Southern California: Santa Barbara, San Clemente, and San Nicolas. Some authors treat the species as polytypic with the night lizards on San Nicolas (X. r. riversiana) distinct from those on Santa Barbara and San Clemente (X. r. reticulata). Previous studies failed to find strong morphological divergence, but it remains uncertain if those studies were hampered by a combination of small sample size, small number of characters, and/or the lack of modern morphometric techniques. Here we examined 172 Island Night Lizards from the three islands for nine morphometric and five meristic characters, increasing the number and types of morphological characters examined over previous studies and applying modern morphometric techniques to test for divergence a...

Predicting rates of consumer-mediated nutrient cycling by a diverse herbivore assemblage

Herbivores mediate the abundances of primary producers both from the top-down, by consuming them, and from the bottom-up, by recycling nutrients. Whereas the top-down effects of herbivores on algae in marine ecosystems are well-documented, less is known about their roles as mediators of local-scale nutrient availability. We conducted a series of surveys and measurements of tide pools and the grazers in those pools between October of 2016 and June of 2017 at an intertidal site on the coast of Southern California, USA (33°35′16.3″N, 117°52′1.5″W). We surveyed grazer abundances in the field, measured biomass of representatives from four different grazer groups (littorine snails, limpets, chitons, and turban snails), measured ammonium excretion rates, and quantified ammonium accumulation rates in tide pools at our study site. We found that different grazer groups were characterized by different per-biomass ammonium excretion rates. Some grazer groups—turban snails and chitons—contributed more ammonium than predicted by their biomass, whereas other grazer groups—littorine snails and limpets—contributed less ammonium than predicted by biomass. Because of these differences between grazer groups, ammonium accumulation rates in tide pools at our study site were effectively predicted based on the ammonium excretion rates of the different grazer groups. However, ammonium accumulation rates were not related to total herbivore biomass. Our results highlight the importance of grazer identity—and particularly the role of species such as turban snails that contribute disproportionately to nutrient recycling—in understanding the contributions of grazers as mediators of bottom-up processes in marine systems.

Aerial surveys and distribution models enable monitoring of fishing in Marine Protected Areas

Marine Protected Areas are rapidly becoming a central method for conservation of aquatic resources, but quantifying the success of these reserves in restricting fishing remains a challenge. Monitoring fishing has long been difficult - there are many types of fishers accessing resources in remote places from a diverse set of platforms (e.g., boat types). We used aerial surveys in conjunction with a novel application of species distribution modeling to develop a method for monitoring the change in fisher distributions following the implementation of MPAs. Aerial survey transects were conducted for 3.5 years before and after the implementation of 25 MPAs along the mainland southern California coast in 2012 and resulted in 13,558 vessel observations representing 19 different boat types. We compared actively fishing commercial and recreational vessels with non-fishing vessels to evaluate the use of MPA areas. There was a statistically significant decrease in proportion of vessels observed within MPAs from 17.5% before to 11.4% after MPA implementation, with MPA-implementation, fishing type, and the interaction all predicting the probability of a vessel being observed within MPA boundaries. Distribution models showed both an overall shift in distributions across all boat types and a decrease in predicted probability of habitat suitability of fishing within MPA boundaries after MPA implementation, although results differed among boat types. We illustrate the utility of distribution modeling for evaluating spatial patterns in human activities, providing a powerful tool for conservation biologists and demonstrate the importance of monitoring programs for establishing both baseline and response data needed for adaptive management of marine ecosystems.