Marine algal toxins and their vectors in southern California cetaceans.

Published baseline data on biotoxin exposure in cetaceans is sparse but critical for interpreting mortality events as harmful algal blooms increase in frequency and duration. We present the first synthesis of domoic acid (DA), saxitoxin (STX), okadaic acid (OA), and microcystin detections in the feces and urine of stranded and bycaught southern California cetaceans, over an 18 year period (2001-2018), along with corresponding stomach content data. DA was detected in 13 out of 19 cetacean species, most often in harbor porpoise (Phocoena phocoena) (81.8%, n = 22) and long-beaked common dolphins (Delphinus delphis bairdii) (74%, n = 231). Maximum DA concentrations of 324,000 ng/g in feces and 271, 967 ng/ml in urine were observed in D. d. bairdii. DA was detected more frequently and at higher concentrations in male vs. female D. d. bairdii. Higher fecal DA concentrations in D. d. bairdii were associated with a greater proportion of northern anchovy (Engraulis mordax) in the diet, indicating it may be a primary vector of DA. Fecal DA concentrations for D. d. bairdii off Point Conception were greater than those from animals sampled off Los Angeles and San Diego counties, reflecting greater primary productivity and higher Pseudo-nitzschia spp. abundance in that region and a greater abundance of E. mordax in the diet. STX was detected at low levels (fecal max = 7.5 ng/g, urine max = 17 ng/ml) in 3.6% (n = 165) of individuals from 3 out of 11 species. The occurrence of E. mordax in 100% of the 3 examined stomachs suggests this species could be a primary vector of the detected STX. OA was detected in 2.4% of tested individuals (n = 85) at a maximum fecal concentration of 422.8 ng/g. Microcystin was detected in 14.3% (n = 7) of tested individuals with a maximum liver concentration of 96.8 ppb.

Recurrent microbial community types driven by nearshore and seasonal processes in coastal Southern California.

A multitude of concurrent biological and physical processes contribute to microbial community turnover, especially in highly dynamic coastal environments. Characterizing what factors contribute most to shifts in microbial community structure and the specific organisms that correlate with changes in the products of photosynthesis improves our understanding of nearshore microbial ecosystem functions. We conducted high frequency sampling in nearshore Southern California in order to capture sub-weekly microbial community dynamics. Microbial communities were characterized by flow cytometry and 16S rRNA gene sequencing, and placed in the context of physicochemical parameters. Within our time-series, season and nutrient availability corresponded to changes in dominant microbial community members. Concurrent aseasonal drivers with overlapping scales of variability were also apparent when we used network analysis to assess the microbial community as subsets of the whole. Our analyses revealed the microbial community as a mosaic, with overlapping groups of taxa that varied on different timescales and correlated with unique abiotic and biotic factors. Specifically, a subnetwork associated with chlorophyll a exhibited rapid turnover, indicating that ecologically important subsets of the microbial community can change on timescales different than and in response to factors other than those that govern turnover of most members of the assemblage.

Distribution of dissolved iron and bacteria producing the photoactive siderophore, vibrioferrin, in waters off Southern California and Northern Baja.

Phytoplankton blooms can cause acute effects on marine ecosystems due either to their production of endogenous toxins or to their enormous biomass leading to major impacts on local economies and public health. Despite years of effort, the causes of these Harmful Algal Blooms are still not fully understood. Our hypothesis is that bacteria that produce photoactive siderophores may provide a bioavailable source of iron for phytoplankton which could in turn stimulate algal growth and support bloom dynamics. Here we correlate iron concentrations, phytoplankton cell counts, bacterial cell abundance, and copy numbers for a photoactive siderophore vibrioferrin biosynthesis gene in water samples taken from 2017 cruises in the Gulf of California, and the Pacific Ocean off the coast of northern Baja California as well as during a multiyear sampling at Scripps Pier in San Diego, CA. We find that bacteria producing the photoactive siderophore vibrioferrin, make up a surprisingly high percentage of total bacteria in Pacific/Gulf of California coastal waters (up to 9%). Vibroferrin's unique properties and the widespread prevalence of its bacterial producers suggest that it may contribute significantly to generating bioavailability of iron via photoredox reactions.

Predicting coastal algal blooms in southern California.

The irregular appearance of planktonic algae blooms off the coast of southern California has been a source of wonder for over a century. Although large algal blooms can have significant negative impacts on ecosystems and human health, a predictive understanding of these events has eluded science, and many have come to regard them as ultimately random phenomena. However, the highly nonlinear nature of ecological dynamics can give the appearance of randomness and stress traditional methods-such as model fitting or analysis of variance-to the point of breaking. The intractability of this problem from a classical linear standpoint can thus give the impression that algal blooms are fundamentally unpredictable. Here, we use an exceptional time series study of coastal phytoplankton dynamics at La Jolla, CA, with an equation-free modeling approach, to show that these phenomena are not random, but can be understood as nonlinear population dynamics forced by external stochastic drivers (so-called "stochastic chaos"). The combination of this modeling approach with an extensive dataset allows us to not only describe historical behavior and clarify existing hypotheses about the mechanisms, but also make out-of-sample predictions of recent algal blooms at La Jolla that were not included in the model development.

Evaluation of photo-reactive siderophore producing bacteria before, during and after a bloom of the dinoflagellate Lingulodinium polyedrum.

Evidence is increasing for a mutualistic relationship between phytoplankton and heterotrophic marine bacteria. It has been proposed that bacteria producing photoactive iron binding compounds known as siderophores could play an important role in such mutualistic associations by producing bioavailable iron utilizable by phytoplankton and in exchange receive autotrophically derived DOM. In order to understand the potential role photoactive siderophores might be playing in bacterial-algal mutualism or marine biogeochemistry in general, it is important to be able to detect and quantify their presence in various environments. One approach to accomplish that end is to make use of high sensitivity genomics technology (qPCR) to search for siderophore biosynthesis genes related to the production of photoactive siderophores. In this way one can access their "biochemical potential" and utilize this information as a proxy for the presence of these siderophores in the marine environment. In this report we studied the correlation of the presence of bacteria producing one of the three photoactive siderophores relative to total bacterial and dinoflagellate numbers from surface water at the Scripps Pier before, during, and after fall bloom of the dinoflagellate Lingulodinium polyedrum. We believe that these findings will aid us in gauging the importance of photoactive siderophores in the marine environment and in harmful algal bloom dynamics in particular.

Proteomic analysis of germinating urediniospores of Phakopsora pachyrhizi, causal agent of Asian soybean rust.

Phakopsora pachyrhizi is an obligate pathogen that causes Asian soybean rust. Asian soybean rust has an unusually broad host range and infects by direct penetration through the leaf cuticle. In order to understand the early events in the infection process, it is important to identify and characterize proteins in P. pachyrhizi. Germination of the urediniospore is the first stage in the infection process and represents a critical life stage applicable to studies with this obligate pathogen. We have applied a 2-DE and MS approach to identify 117 proteins from the National Center of Biotechnology Information nonredundant protein database and a custom database of Basidiomycota EST sequences. Proteins with roles in primary metabolism, energy transduction, stress, cellular regulation and signaling were identified in this study. This data set is accessible at http://world-2dpage.expasy.org/repository/database=0018.