Southern California Coastal Waters Research Articles

The Second National Workshop on Marine eDNA: A workshop to accelerate the incorporation of eDNA science into environmental management applications

AbstractThe Second National Workshop on Environmental DNA was held on September 12–15, 2022, at the Southern California Coastal Water Research Project (SCCWRP) in Southern California and was focused on transitioning eDNA from research to management applications. The Workshop was attended by 150 people in‐person and an additional 200 more online. Workshop attendees represented a broad cross‐section of disciplines and backgrounds, including research scientists, state, and federal agencies, and those in the environmental management sector. This diverse collection of attendees assembled with the goal of achieving cross‐sector collaboration and working together to identify the necessary next steps to move eDNA methods into the management application mainstream. The Workshop structure included a Training Day oriented towards environmental managers and those new to eDNA science, to facilitate a common ground for discussions on subsequent days. The Plenary Day focused on case studies about eDNA applications and culminated with a roundtable panel discussion with local, state, and federal agency representatives on eDNA method readiness and the road to method adoption. Among the key takeaways from the Workshop was bridging the communication gap between researchers and managers because scientists often focus on technical details and the unknowns, giving the impression that eDNA science is not yet mature, whereas managers want to hear consensus statements about readiness and a roadmap for method adoption, including standard operating procedures, lab accreditation, and unified sequence libraries. This outcome was a clear directive for many scientists in attendance that it is time to stop letting perfect be the enemy of good and to focus future efforts on method harmonization and a national strategy towards method adoption. The Workshop concluded with a working session of invited participants to identify key priorities and needs to achieve the goals highlighted in the Workshop discussions.

Characterization of suspended particulate matter in contrasting coastal marine environments with angle-resolved polarized light scattering measurements.

Optical proxies based on light scattering measurements have potential to improve the study and monitoring of aquatic environments. In this study, we evaluated several optical proxies for characterization of particle mass concentration, composition, and size distribution of suspended particulate matter from two contrasting coastal marine environments. We expanded upon our previous study of Southern California coastal waters, which generally contained high proportions of organic particles, by conducting angle-resolved polarized light scattering measurements in predominantly turbid and inorganic-particle dominated Arctic coastal waters near Prudhoe Bay, Alaska. We observed that the particulate backscattering coefficient bbp was the most effective proxy for the mass concentration of suspended particulate matter (SPM) when compared with particulate scattering and attenuation coefficients bp and cp. Improvements were seen with bbp as a proxy for the concentration of particulate organic carbon (POC), although only if particulate assemblages were previously classified in terms of particle composition. We found that the ratio of polarized-light scattering measurements at 110º and 18º was superior in performance as a proxy for the composition parameter POC/SPM in comparison to the particulate backscattering ratio bbp/bp. The maximum value of the degree of linear polarization DoLPp,max observed within the range of scattering angles 89°-106° was found to provide a reasonably good proxy for a particle size parameter (i.e., 90th percentile of particle volume distribution) which characterizes the proportions of small- and large-sized particles. These findings can inform the development of polarized light scattering sensors to enhance the capabilities of autonomous platforms.

Macroalgal detrital systems: an overlooked ecological niche for heterotrophic nitrogen fixation.

Diazotrophic macroalgal associations (DMAs) can contribute fixed nitrogen (N) to the host macroalgae. Biological nitrogen fixation (BNF) rates investigated using acetylene reduction assays with living macroalgae surrounding Santa Catalina Island were low (maximum: 36 nmol N×g-1 (dw)×h-1 ) and probably insufficient towards helping meet macroalgal N demand. However, DMAs were observed during periods of low nitrate availability in Southern California coastal waters, highlighting the potential importance of diazotrophs during N depleted conditions. Eleven long-term (16-32 days) litter bag decomposition experiments with various macroalgae, especially those with high (> 10) C:N ratios, resulted in much higher BNF rates (maximum: 693 nmol N×g-1 (dw)×h-1 ) than observed with living macroalgae. BNF rates were lower at the beginning of macroalgal decomposition but rapidly increased during the second phase before declining towards the end of decomposition. Labile carbon availability is likely influencing BNF rates throughout macroalgal degradation and limits BNF in the final decomposition stage. Comparable dark and light BNF rates with most macroalgae surveyed suggest macroalgal detrital systems are an overlooked, potentially global, niche for heterotrophic N2 fixation. Lastly, suppressed BNF rates with sodium molybdate additions highlight the prevalence of sulfate reducing diazotrophs.

Bacterial Colonization and Partial Degradation of Plastic Debris in California Coastal Waters

Several studies have addressed the role of microbes associated with plastic marine debris. However, little is known about the nature of microbes attaching to plastic in coastal areas, and how it could potentially impact humans.The goal of this project is to evaluate the microbial diversity on plastic marine debris, specifically the more abundant types of floating plastic (ex. single‐use plastic bags) made of polyethylene (PE) and polypropylene (PP) in coastal waters. Our hypothesis is that microbes will colonize plastic and that the diversity and abundance of microbial communities will be directly influenced by plastic resin type. We are also interested in colonization of plastic by pathogenic species and/or species with potential to degrade plastic.Three plastic resin types (high density polyethylene (HDPE), low density polyethylene (LDPE), and polypropylene (PP)) were placed in stainless steel cages, submerged to approx. 50 cm depth in Southern California coastal waters and retrieved at 4 different time points between 3 and 40 days along with water samples for comparative purposes. Two sample sets were collected between May 2016 and May 2017. DNA was extracted and 16S rRNA metagenomic tag sequencing was used to differentiate the microbial community. Colonies grown parallel on Salt Water Agar and Vibrio‐specific media were characterized by 16S amplicon sequencing. In addition, Fourier Transform Infrared Spectroscopy (FTIR) was used to analyze the breakdown of plastic over time and scanning electron microscopy (SEM) to visualize the biofilms attached to plastic on day 40.Our results indicate that over 40% of the sequences obtained are from unclassified organisms. The three plastic resin types exhibited a diverse assemblage of heterotrophic bacterial taxa, while in water samples photosynthetic genera were the most prevalent. There were differences between plastic resin types and the surrounding water, as well as temporal differences. We did not find evidence of Vibrio cholerae either by 16S metagenomic sequencing or by 16S sequencing of colonies isolated on ChromAgar Vibrio. However, other potentially pathogenic genera such as Francisella and Rickettsia were present on plastic at earlier sampling time points. In addition, all three plastic resins showed signs of chemical degradation over time, and SEM revealed a rich biofilm containing diatoms, bacterial, and protist populations.Together, this study indicates that there are differences in the microbial communities growing on coastal marine plastic debris with potential implications for human health and the environment.Support or Funding InformationThis work was supported by NU College of Letters & Sciences internal grants, the 2016 NU Presidential Award, as well as crowd funding through the Experiment website (DOI 10.18258/7301).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Molecular Alternatives to Indicator and Pathogen Detection: Real-time PCR

Microbial quality of water is a prime public health concern in today's world. To protect public health, the World Health Organization and the U.S. Environmental Protection Agency have established microbial pollution indicator standards and recommended routine monitoring of water for both total and fecal coliforms (Dufour, 1984, U.S. EPA 1986,1994, WHO 1993). However, the adequacy of current water quality standards to indicate the presence or absence of human pathogens is still questionable. For example, human viruses are more resistant to sewage treatment processes and environmental conditions than bacterial indicators and therefore may pose a substantial threat. It is now recognized that the absence, or a low concentration, of indicator organisms in water may not adequately reflect the absence of human viruses. In our previous study of southern California coastal waters, we found over 30% of coastal waters tested contained human viruses, and the presence of these viruses did not correlate with an elevated level of bacterial indicators (Jiang et al. 2000). The goal of this research is to develop and validate a molecular method for rapid and specific detection of microbial contaminants including human viruses and bacterial indicators in treated sewage effluents and receiving waters. This title belongs to WERF Research Report Series ISBN: 9781843397359 (Print) ISBN: 9781780404486 (eBook)

“Salty” conversation

Thiel replies: When thinking about potential toxicity, which Neal Reid mentions, it’s key to remember that almost all the material in the brine originated in the ocean. Nevertheless, ensuring environmentally friendly disposal continues to be an active area of research, and modern outfalls are very effective at dispersing the brine flow so as to minimize local increases in the concentration of salts and other dissolved compounds. A study for the Carlsbad desalination project in California concluded that properly designed outfalls have “impacts that extend only a few tens of meters from the discharge.”11. S. Jenkins et al., Management of Brine Discharges to Coastal Waters: Recommendations of a Science Advisory Panel, tech. rep. 694, Southern California Coastal Water Research Project (March 2012), p. ii. The Carlsbad plant also mixes the reverse-osmosis brine with seawater used for cooling a colocated power plant prior to discharge, which reduces its salinity before it hits the ocean. And as for the comparison to nuclear waste, let’s not forget that the diffusion time for the salt in the disposed brine is orders of magnitude less than the half-life of radioactive waste!To answer Jonathan Allen’s concern, the kWhe values given for the evaporative systems are exergetic values of the heat input. That approach uses the Carnot efficiency between the desalination system’s top temperature, which often reaches 70 °C, and an ambient temperature of 25 °C to convert between heat and work. The cost of the thermal energy input itself may be less than for electricity, but the costs associated with constructing, for example, a solar-thermal collector or a heat exchanger required to use waste heat can be significant. Lower energy consumption may not imply lower cost, but reverse osmosis is far and away the dominant choice of recent installed desalination capacity.Desalination powered by renewable energy is a topic of great interest to many in the desalination community—myself included!REFERENCESSection:ChooseTop of pageREFERENCES <<CITING ARTICLES1. S. Jenkins et al., Management of Brine Discharges to Coastal Waters: Recommendations of a Science Advisory Panel, tech. rep. 694, Southern California Coastal Water Research Project (March 2012), p. ii. Google Scholar© 2015 American Institute of Physics.

Temporal variation in optical properties of chromophoric dissolved organic matter (CDOM) in Southern California coastal waters with nearshore kelp and seagrass

Optical properties of chromophoric dissolved organic matter (CDOM) were measured in surf zone waters in diurnal field studies at a Southern California beach with nearshore kelp and seagrass beds and intertidal plant wrack. Absorption coefficients (aCDOM(300 nm)) ranged from 0.35 m−1 to 3.7 m−1 with short-term variability 2.5, BIX > 1.1) were consistent with microbial aquatic sources. Leachates of senescent kelp and seagrass had protein and humic-type EEM peaks. After solar simulator irradiation (4 h), protein peaks rapidly photochemically degraded, humic-type peak C increased in intensity and peak M disappeared. Optical characteristics of kelp leachates were most similar to field samples, consistent with minimal contributions from sea grass, a small component of the biomass at this site. Increases in aCDOM(300 nm) with decreases in S are attributed to the input of freshly produced autochthonous organic material at ebbing and flooding tides, from exudation and microbial processing of senescent plant wrack and nearshore macroalgal vegetation. Other allochthonous sources are hypothesized to be ground water seepage and terrestrial runoff.

Death from below: Investigation of inhibitory factors in bloom development during a wastewater effluent diversion

Eutrophication of coastal waters is an urgent and globally increasing problem. A significant source of nutrients to Southern California coastal waters is direct discharge of secondarily treated wastewater effluent from regional Publicly Owned Treatment Works. The planned diversion of treated wastewater from the Orange County Sanitation District's main (5-mile) pipe to a shallow 1-mile pipe off Huntington Beach, CA in autumn 2012 provided an unprecedented opportunity to monitor the response of the coastal phytoplankton community to a major anthropogenic loading event. Despite the continuous release of approximately 11.07 × 106 m3 of effluent containing 1743 μM ammonium, there was virtually no detectable change in phytoplankton biomass, in striking contrast to the harmful algal bloom dominated community that quickly developed in response to a comparable diversion in Santa Monica Bay in 2006. Field and laboratory studies demonstrate that disinfection byproducts associated with enhanced dechlorination were present in the discharged water, and that these compounds had a strong inhibitory impact on phytoplankton photophysiology and growth, lasting 24 h for photosynthetic performance and at least 3 d for growth, assessed as change in chlorophyll. Thus, the perhaps fortuitous unintended consequence of enhanced chlorination was the production of inhibitory compounds that suppressed the potential phytoplankton response over a large swath of the continental shelf during the diversion.

A shallow-diving seabird predator as an indicator of prey availability in southern California waters: A longitudinal study

We tested the hypothesis that the Elegant Tern (Thalasseus elegans), a plunge-diving predator, is an indicator of changes in the prey community in southern California coastal waters. Shannon diversity (H′) of the tern's diet determined from dropped fish collected variously at the three nesting sites for 18years over a 21-year interval (1993–2013) showed no significant change in diet diversity. Based on a species–accumulation curve, total diet species represented about 70% of an extrapolated asymptotic richness. Abundance patterns of five prey species making up >75% of prey numbers for all years were compared with abundance patterns of the same species in independent surveys obtained from zooplankton tows, bottom trawls and power-plant entrapments. Three of the five species – northern anchovy, kelp pipefish and California lizardfish – showed significant, positive correlations between diet and survey abundances. Even though the tern's diet has been dominated by anchovy and pipefish, its diet is still broad, with prey taxa representing >75% of the 42 species groups making up the California shelf fish fauna. Altogether, our results support the hypothesis that the Elegant Tern, with its flexible diet, is a qualitative indicator, a sentinel, of changes in the prey communities in southern California coastal waters.

Anthropogenic nutrient sources rival natural sources on small scales in the coastal waters of the Southern California Bight

Anthropogenic nutrients have been shown to provide significant sources of nitrogen (N) that have been linked to increased primary production and harmful algal blooms worldwide. There is a general perception that in upwelling regions, the flux of anthropogenic nutrient inputs is small relative to upwelling flux, and therefore anthropogenic inputs have relatively little effect on the productivity of coastal waters. To test the hypothesis that natural sources (e.g., upwelling) greatly exceed anthropogenic nutrient sources to the Southern California Bight (SCB), this study compared the source contributions of N from four major nutrient sources: (1) upwelling, (2) treated wastewater effluent discharged to ocean outfalls, (3) riverine runoff, and (4) atmospheric deposition. This comparison was made using large regional data sets combined with modeling on both regional and local scales. At the regional bight‐wide spatial scale, upwelling was the largest source of N by an order of magnitude to effluent and two orders of magnitude to riverine runoff. However, at smaller spatial scales, more relevant to algal bloom development, natural and anthropogenic contributions were equivalent. In particular, wastewater effluent and upwelling contributed the same quantity of N in several subregions of the SCB. These findings contradict the currently held perception that in upwelling‐dominated regions anthropogenic nutrient inputs are negligible, and suggest that anthropogenic nutrients, mainly wastewater effluent, can provide a significant source of nitrogen for nearshore productivity in Southern California coastal waters.

The use of kelp sieve tube sap metal composition to characterize urban runoff in southern California coastal waters

This study introduces an innovative method for biomonitoring using giant kelp (Macrocystis pyrifera) sieve tube sap (STS) metal concentrations as an indication of pollution influence. STS was sampled from fronds collected from 10 southern California locations, including two reference sites on Santa Catalina Island. Using ICP-MS methodology, STS concentrations of 17 different metals were measured (n=495). Several metals associated with pollution showed the highest STS concentrations and most seasonal variation from populations inside the Port of Los Angeles/Long Beach. Lowest concentrations were measured at less-urbanized areas: Santa Catalina Island and Malibu. Some metals showed a spatial gradient in STS metal concentration with increasing distance from point sources (i.e. Los Angeles River). Cluster analyses indicate that polluted seawater may affect kelp uptake of metals essential for cellular function. Results show that this method can be useful in describing bioavailable metal pollution with implications for accumulation within an important ecosystem.

Earth Science in the Urban Ocean: The Southern California Continental Borderland

This 481-page collection, published in 2009, contains 26 papers, primarily by U.S. Geological Survey (USGS) authors but including a few papers from non-USGS agencies, such as the Southern California Coastal Water Research Project and various university authors. The book is divided into six sections: (1) Surficial Seafloor Mapping and Characterization, (2) Source to Sink Sedimentation, (3) Southern California Physical Oceanography and Sediment Transport, (4) Regional Tectonic Structure: Earthquake and Tsunami Hazards, (5) Coastal Aquifers of Southern California, and (6) Contaminant and Biological Implications of Earth Science Studies in the Southern California Bight. Each section contains an introduction that summarizes the papers that follow. The study area comprises the Southern California Continental Borderland and the Southern California Bight, physiographic features resulting from the unique tectonic evolution of the region. The Bight consists of the coast from Point Conception south past Santa Monica and San Pedro Bays to the United States–Mexico border, as well as the Channel Islands. The Bight is isolated from the major currents of the eastern Pacific and is characterized by the presence of islands, submarine canyons, and active faults. Filled basins, now above sea level, are home to a population of over 20 million people. A comprehensive map of this area near the beginning of the book would better orient the reader; however, an adequate figure is found on page 233. Perhaps the most striking aspect of the book is the abundance of detailed illustrations, including seafloor maps produced using multi-beam, high-resolution echosounders (MBES) and seismic reflection profiles produced by “deep-tow boomers.” The seafloor maps depict the various bathymetric features, such as …

Transfer of cholera toxin genes from O1 to non‐O1/O139 strains by vibriophages from California coastal waters

Vibrio cholerae is an important bacterial pathogen that causes global cholera epidemic. Although they are commonly found in coastal waters around the world, most environmental isolates do not contain cholera toxin genes. This study investigates vibriophages in southern California coastal waters and their ability to transfer cholera toxin genes. Lytic phages infecting V. cholerae were isolated from Newport Bay, California, between May and November, while none was found in winter. Some of the phage isolates can infect multiple environmental V. cholerae strains and El Tor strains. All phages contained double-stranded DNA. Transduction experiments using kanamycin-resistant gene marked CTXPhi demonstrated that some environmental vibriophages can transfer CTXPhi genes from O1 El Tor strain to environmental non-O1/O139 V. cholerae via generalized transduction. Vibriophages are important components of the natural aquatic ecosystem. They play an important role in influencing the dynamics and evolution of V. cholerae in the environment. This study demonstrates the significance of vibriophages in the coastal environment and transduction as one of the mechanisms of pathogenicity evolution among environmental V. cholerae.

Ecology of coliphages in southern California coastal waters

This study aims to investigate the ecology of coliphages, an important microbial pollution indicator. Specifically, our experiments address (i) the ability of environmental Escherichia coli (E. coli) to serve as hosts for coliphage replication, and (ii) the temporal and spatial distribution of coliphages in coastal waters. Water samples from three locations in California's Newport Bay watershed were tested for the presence of coliphages every 2 weeks for an entire year. A total of nine E. coli strains isolated from various sources served as hosts for coliphage detection. Coliphage occurrence was significantly different between freshwater, estuarine and coastal locations and correlated with water temperature, salinity and rainfall in the watershed. The coliphages isolated on the environmental hosts had a broad host-range relative to the coliphages isolated on an E. coli strain from sewage and a US EPA recommended strain for coliphage detection. Coliphage occurrence was related to the temperature, rainfall and salinity within the bay. The adaptation to a broad host-range may enable the proliferation of coliphages in the aquatic environment. Understanding the seasonal variation of phages is useful for establishing a background level of coliphage presence in coastal waters. The broad host-range of coliphages isolated on the environmental E. coli host calls for investigation of coliphage replication in the aquatic environment.

Photochemical production of hydrogen peroxide in size-fractionated Southern California coastal waters

Hydrogen peroxide (H 2O 2) photochemical production was measured in bulk and size-fractionated surf zone and source waters (Orange County, California, USA). Post-irradiation (60 min; 300 W ozone-free xenon lamp), maximum H 2O 2 concentrations were ∼10 000 nM (source) and ∼1500 nM (surf zone). Average initial hydrogen peroxide production rates (HPPR) were higher in bulk source waters (11 ± 7.0 nM s −1) than the surf zone (2.5 ± 1 nM s −1). A linear relationship was observed between non-purgeable dissolved organic carbon and absorbance coefficient (m −1 (300 nm)). HPPR increased with increasing absorbance coefficient for bulk and size-fractionated source waters, consistent with photochemical production from CDOM. However, HPPR varied significantly (5×) for surf zone samples with the same absorbance coefficients, even though optical properties suggested CDOM from salt marsh source waters dominates the surf zone. To compare samples with varying CDOM levels, apparent quantum yields ( Φ) for H 2O 2 photochemical production were calculated. Source waters showed no significant difference in Φ between bulk, large (>1000 Da (>1 kDa)) and small (<1 kDa) size fractions, suggesting H 2O 2 production efficiency is homogeneously distributed across CDOM size. However, surf zone waters had significantly higher Φ than source (bulk 0.086 ± 0.04 vs. 0.034 ± 0.013; <1 kDa 0.183 ± 0.012 vs. 0.027 ± 0.018; >1 kDa 0.151 ± 0.090 vs. 0.016 ± 0.009), suggesting additional production from non-CDOM sources. H 2O 2 photochemical production was significant for intertidal beach sand and senescent kelp (sunlight; ∼42 nM h −1 vs. ∼5 nM h −1), on the order of CDOM production rates previously measured in coastal and oceanic waters. This is the first study of H 2O 2 photochemical production in size-fractionated coastal waters showing significant production from non-CDOM sources in the surf zone.

Saltmarshes as a source of chromophoric dissolved organic matter (CDOM) to Southern California coastal waters

To determine chromophoric dissolved organic matter (CDOM) sources in Southern California coastal waters, optical properties of a river outlet and adjacent tidally flushed salt marshes were monitored (dry season; June‐July 2001). Average absorption coefficients doubled at ebb vs. flood tides (4.8 ± 1.5 vs. 2.1 ± 0.9 m‐1; 300 nm), suggesting significant salt marsh CDOM inputs into coastal waters. Average spectral slopes were not statistically different for any sites or tides (0.010 ± 0.002 nm−1), consistent with salt marsh CDOM dominating coastal waters. Three‐dimensional fluorescence excitation‐emission matrices (EEMs) at ebb tide showed contributions from terrestrial, protein, and marine humic‐like peaks, suggesting production and output of these materials from the marsh. A marine humic signal at the river outlet during an offshore upwelling event indicated an additional sporadic nonmarsh marine humic‐like source. EEMs of six common salt marsh plant leachates showed protein, terrestrial, and marine humic‐like peaks. To estimate CDOM photodegradation in the marsh, fluorescence intensity decays from photobleaching experiments were fit to first‐order kinetics. Most humic peaks degraded with a half‐life of t1/2 = 10‐20 h, which overlaps the estimated residence time of water in the marshes (∼12 h). Most protein peaks were resistant to photodegradation, suggesting that the low levels of protein vs. humic‐like material measured in natural waters was due to rapid bioutilization of proteinaceous material. The rapid photodegradation of plant leachate humic material and the low spectral slopes for the field sites suggest that marsh sediments would be an important source of CDOM.

Yessotoxin detected in mussel ( Mytilus californicus) and phytoplankton samples from the U.S. west coast

Yessotoxin (YTX) was detected in an algal sample and two mussel samples (0.07–0.10 μg g −1) collected from Scripps Pier in La Jolla, California during a bloom of Lingulodinium polyedrum. Mussel samples collected from Monterey Bay, California also contained measurable YTX (levels up to 0.06 μg g −1) in samples obtained during a 6-month (weekly) sampling period. Gonyaulax spinifera and L. polyedrum were identified in background concentrations in Monterey Bay during the time of contamination. An algal sample from Washington coastal waters collected during non-bloom conditions also contained YTX, possibly originating from Protoceratium reticulatum. Three strains of L. polyedrum (CCMP1931, CCMP1936, 104A) isolated from southern California coastal waters and one strain of G. spinifera (CCMP409) isolated from Maine were tested for YTX production using two methods, competitive ELISA and liquid chromatography–mass spectrometry (LC–MS). The ELISA method detected YTX in the particulate phase in two of three L. polyedrum strains. The LC–MS method did not detect YTX in the particulate or dissolved phase of any of the strains. To our knowledge, this is the first study to test and confirm YTX in environmental samples from California and Washington coastal waters. It is highly likely that L. polyedrum was responsible for the YTX contamination in the southern California samples. Future research needs to conclusively determine the biological origin(s) of YTX contamination in central California and Washington coastal waters.

Beach attendance and bathing rates for Southern California beaches

Annual beach attendance (BA) was collected for 75 beaches along the 350 km of coastline in Southern California for the years 2000–2004. On average, over 129 million beach visits occur each year, with the majority (54%) of visits occurring at only 15 beaches. Almost half of all visits (48%) occur on weekends. BA displays distinct seasonality with 53% of visits occurring in June, July and August. On average only 45% of individuals attending the beach have physical contact with the coastal waters; water exposure rates are low (26%) during colder winter months, and peak during warmer summer months (54%). An average of 56 million recreational bathing events (BE) occurs in Southern California's coastal waters every year. This quantification and statistical analysis of the magnitude and distribution of beach visitations across the region produce important data that have direct implications for beach management, tourism, public health and the environment.

Structure and function of the stomachless digestive system in three related species of New World silverside fishes (Atherinopsidae) representing herbivory, omnivory, and carnivory

We explored possible diet-related specializations in the digestive tract of stomachless fishes by summarizing the diets, verifying the absence of a stomach, and comparing gut lengths, microvilli surface areas, and activities of five digestive enzymes in four taxa of silversides from southern California coastal waters. For the comparisons, we examined these gut features in Atherinops affinis from both estuarine and kelp-forest habitats, and Atherinopsis californiensis and Leuresthes tenuis from open coastal habitats. A. affinis was found to be primarily herbivorous in estuaries and carnivorous in kelp forests, whereas As. californiensis was shown to be somewhat omnivorous but mainly carnivorous, and L. tenuis strictly carnivorous. Estuarine A. affinis exhibited the longest gut, largest microvilli surface area, and highest amylase and maltase activities, all arguably reflecting responses to an algal diet. In contrast, kelp-forest A. affinis displayed the highest trypsin activity and generally similar microvilli surface areas and aminopeptidase, amylase, and maltase activities to the two other carnivorous taxa. All four taxa showed similar lipase activities that compared closely with published values for other fishes. Taken together, our results reveal striking differences in gut structure and function among the four taxa, but especially between the estuarine and kelp-forest populations of A. affinis. Further studies are required to assess the roles of genetic variation and phenotypic plasticity in explaining the differences in these herbivorous and carnivorous taxa.

Sources and growth dynamics of fecal indicator bacteria in a coastal wetland system and potential impacts to adjacent waters

Coastal wetlands are receiving increased attention as a putative source of fecal indicator bacteria (FIB) in Southern California coastal waters. We examined temporal trends of water and sediment-associated FIB after rain events along with spatial sediment characteristics at two sites within the Santa Ana River wetlands and made comparisons to FIB levels observed in adjacent surf zone waters. During the first two rain events, total coliforms (TC), Escherichia coli (EC) and enterococci (ENT) in wetland water and sediment samples peaked either on the same day or within several days of the rain event, while the third resulted in elevated wetlands sediment TC levels only. TC in adjacent coastal waters consistently peaked on the same day as the rain event and decreased quickly thereafter (within 1 day). The TC/EC ratios of surf zone samples consistently fell below 10, indicating an increased probability of human fecal contamination whereas wetland TC/EC ratios were higher, averaging approximately 60 and 14 at each site. These results suggest sediment-associated FIB populations may be distinct from those found in the water samples, or at least have internal dynamics independent of water-borne populations. Increases in sediment-associated FIB may be due to in situ population growth and/or increased survival due to changes in environmental parameters (salinity, moisture and nutrient input) resulting from the rain events. Spatial differences in between the two sites may be due to sediment differences such as organic content and finer grain size and/or discrete sources of FIB.