Southern California Coastal Water Research Project

This study monitored four bioretention planters installed at Stevens Institute of Technology providing information on the hydrologic mitigation potential of planters and design considerations for future guidance. Monitoring during 18 months spanning 3 calendar years compared performance against several bioretention system design objectives, including fully captured events, peak flow reduction, and runoff retention. Hydraulic loading ratio and media porosity affected the fraction of captured events, with one-fifth of the events completely captured. The captured storms were less than 2.0 mm/m2 of drainage area 77% of the time. The planters halved the peak flow rate for 61% of observations. The entire media volume was wetted in almost half of the events but rarely fully saturated. A modified available water capacity calculation based on the difference between the field capacity and the lowest measured volumetric water content provided a useful estimate of the median retention per event. To use this estimator, it is proposed to estimate the modified available water capacity as the difference between the laboratory-measured field capacity and a laboratory-measured wilting point increased by a factor of safety to account for the practical issue that the planters never dried fully between rain events in the New Jersey temperate climate.

Harmful Algal Blooms (HABs) are a hazard for coastal environments worldwide; identifying screening thresholds of chlorophyll-a (chl-a) associated with increased risk of HABs is a management priority. Molecular surveillance of coastal phytoplankton and bivalve biotoxins could be used to link chl-a with HAB risk, but requires an understanding of whether the HAB risks increase uniformly as chl-a rises, or whether some taxa are disproportionately favored, and if these relationships vary by season. In this study, we present a novel use of molecular abundance data to investigate the scientific bases for estuarine chl-a thresholds protective against HABs. In San Francisco Bay (SFB), California, the relationship between molecular relative abundance (as measured by 18S metabarcoding) of nine different HAB taxa, absolute quantitative polymerase chain reaction (qPCR) abundance, and mussel toxin concentrations of a subset of the taxa were investigated for thresholds as a function of increasing chl-a. Our results show most HAB taxa did not increase in absolute or relative abundance during SFB's spring bloom interval, when chl-a levels were highest (>10 µg/L) but the assemblage was dominated by non-harmful diatoms. However, several flagellated, mixotrophic taxa did increase above their molecular baseline in fall, and the combined probability of any HAB occurring above baseline was elevated when chl-a reached ∼4.6 µg/L in the fall. This work demonstrates the promise of molecular approaches in disentangling the seasonally complex interplay between stressors and phytoplankton/HAB community responses and has the potential to provide clearer, more cost-effective monitoring and mitigation strategies for managers.

Animal populations often display coherent temporal fluctuations in their abundance, with far-ranging implications for species persistence and ecosystem stability. The key mechanisms driving spatial population synchrony include organismal dispersal, spatially correlated environmental dynamics (Moran effect) and concordant consumer–resource dynamics. Disentangling these mechanisms, however, is notoriously difficult in natural systems, and the extent to which the biotic environment (intensity and types of biotic interactions) mediates metapopulation dynamics remains a largely unanswered question. Here, we test the hypothesis that compositional differences among communities (i.e. beta-diversity), used as a proxy of the differences in biotic interactions experienced by separated populations, reduce population synchrony. Using an extensive dataset of fish population abundance time-series across Europe, we provide evidence that higher beta-diversity is associated with reduced spatial population synchrony within river networks and demonstrate that these effects are independent from geographic separation, environmental dissimilarity, and Moran effects. Although beta-diversity is commonly shown to promote metacommunity stability by reducing spatial synchrony in aggregate community attributes (e.g. total biomass), our study indicates that compositional heterogeneity provides a previously overlooked spatial insurance effect that influences metapopulation dynamics by promoting asynchrony between populations separated in space. These findings illustrate how community assembly across different locations within river networks contributes to metapopulation stability and persistence of individual species and further highlights the implications of the loss in beta-diversity over time via biotic homogenization.

Establishing appropriate restoration targets, tracking progress toward those targets, and determining appropriate adaptive intervention are some of the greatest challenges to successful ecosystem restoration. Addressing these challenges is often informed by the use of “reference sites” that represent relatively unaltered or historical conditions and conceptually can be used to provide context and comparison for restoration projects. In reality, contemporary “unaltered” sites have often been manipulated by centuries of cultural practices and “pristine” conditions cannot be defined. Moreover, in highly altered landscapes or where stressors are continuing to rapidly reshape ecosystem structure, few or no sites may be unaltered enough to serve as pristine or aspirational reference standard sites for restoration. To address this challenge, we adapted the concept of “reference sites” to a framework for developing sentinel site networks, which consist of sites along a gradient of condition. These sites are selected for long‐term monitoring to track ecological conditions through time, to evaluate the effect of regional trends in external conditions or stressors, and to document progress toward site‐specific goals and regional objectives. Developing a sentinel site network involves screening sites based on condition, stressors, representativeness, and feasibility for long‐term monitoring, informed by input from regional experts and stakeholders. The resultant network includes sites along a gradient of condition, geographical representation, and management that can be customized or regionally based on local constraints. We demonstrate the application of this process through the development of a sentinel site network for coastal wetlands in the highly developed southern California (U.S.A.) region. This process can be readily adapted to other habitats globally and may be particularly useful in habitats that have been highly impacted by human activities.

Microbial contamination of urban stormwater, rivers, and creeks during rainstorms is a persistent and widespread problem. Remediation of these waters has proven to be challenging since there are many potential sources for the fecal indicator bacteria on which water quality is regulated. Microbial source tracking markers have allowed for improved identification and quantification of the sources of contamination, but the majority of the source-attributed microbial targets are not responsible for causing the illnesses associated with waterborne human fecal contamination. Thus there is a need to better understand the relationships of human pathogens and human fecal markers in stormwater. In this study, we used a spatially-intensive sampling approach (31 sites) across southern California for the analysis of stormwater. During three storms from 2021-2023, we used droplet digital PCR to quantify the human fecal markers HF183 and Lachno3 along with human adenovirus, human norovirus, Campylobacter spp., and Salmonella spp. This spatially intensive sampling design captures information from a 5900 km2 area with ∼22 million people. We detected human markers HF183 and Lachno3 genes at 90% and 97% of the sites; concentrations ranged from below detection to 104 and 105 gene copies per 100 mL, respectively. We found variable concentrations of human bacterial and viral pathogen genes. HF183 was significantly correlated to human adenovirus and Lachno3. Lachno3 was also significantly correlated with Salmonella. We reported PCR inhibition in 83-90% of the samples but found that separating sediment and adding proteinase K during lysis improved DNA/RNA extraction efficiency and reduced inhibition.

As a result, in the Abstract, "This phenomenon persists for 4 to 6 months of the year over an area of 278,40 km 2 (30% of SCB area)." now reads: "This phenomenon persists for 4 to 6 months of the year over an area of 27,840 km 2 (30% of SCB area)."In addition, in the Results, under the subheading 'Effects of land-based nutrient inputs on phytoplankton biomass, oxygen, and pH' , "The area impacted by these biogeochemical changes is approximately 278,40 km 2 in size."

Abstract This study uses large eddy simulations to investigate nutrient transport and uptake in suspended macroalgal farms. Various farm configurations and oceanic forcing conditions are examined, with the farm base located near the nutricline depth. We introduce the Damkohler number Da to quantify the balance between nutrient consumption by macroalgae uptake and supply by farm‐enhanced nutrient transport. Most cases exhibit low Da, indicating that farm‐generated turbulence drives sufficient upward nutrient fluxes, supporting macroalgae growth. High Da and starvation may occur in fully grown farm blocks, a configuration that generates the weakest turbulence, particularly when combined with densely planted macroalgae or weak flow conditions. Flow stagnation within the farm due to macroalgae drag may constrain the uptake efficiency and further increase the starvation risk. Mitigation strategies involve timely harvesting, avoiding dense macroalgae canopies, and selecting farm locations with robust ocean currents and waves. This study provides insights for sustainable macroalgal farm planning.

Abstract Burrowing ecosystem engineers, such as termites, crabs, marmots, and foxes, can profoundly affect the biological structure and ecosystem functions of their environments. However, the relative importance of the effects of burrowing engineers on sediments are challenging to predict and are expected to be influenced by engineer density, engineer functional traits (e.g., burrow morphology), and environmental conditions (e.g., geomorphology, vegetation presence). To develop robust hypotheses predicting the impacts of burrowing ecosystem engineers, we conducted a systematic meta‐analysis evaluating the effects of burrowing crabs on sediment properties, nutrient stocks, and ecosystem functions in soft‐sediment coastal habitats (e.g., salt marshes, mangrove forests, tidal flats). Additionally, we tested the impacts of crab burrow density, burrowing crab superfamily (a proxy for crab burrow morphology and diet), and biotic conditions (i.e., vegetation) on the effects of burrowing crab engineers on coastal sediments. Burrowing crabs rework and oxygenate sediments and accelerate rates of nutrient cycling (i.e., nitrification and CO2 flux). However, the magnitude and direction of burrowing crab effects depend on burrowing crab superfamily, the presence of vegetation, and their interaction. Crab burrow density did not consistently predict burrowing engineer effects on sediments. Future efforts need to focus on implementing rigorous manipulative experiments to assess crab ecosystem engineering effects, since methodological variation has hindered efforts to generalize their effects. Our findings suggest that crab engineering effects are predictable across environmental contexts, and understanding the context dependency of crab engineering effects may promote the management and restoration of the critical ecosystem services that are mediated by crab engineers.

Extracellular vesicles (EVs) are membrane-bound exosomes secreted into the apoplast. Two distinct populations of EVs have been described in Arabidopsis: PEN1-associated and TET8-associated. We previously noted early leaf senescence in the pen1 single and pen1pen3 double mutant. Both PEN1 and PEN3 are abundant in EV proteomes suggesting EVs might regulate leaf senescence in soil-grown plants. We observed that TET8 is more abundant in the apoplast of early senescing pen1 and pen1pen3 mutant rosettes and in older WT rosettes. The increase in apoplast TET8 in the pen1 mutant did not correspond to increased TET8 mRNA levels. In addition, apoplast TET8 was more abundant in the early leaf senescence myb59 mutant, meaning the increase in apoplast TET8 protein during leaf senescence is not dependent on pen1 or pen3 . Genetic analysis showed a significant delay in leaf senescence in tet3tet8 double mutants after six weeks of growth suggesting that these two tetraspanin paralogs operate additively and are positive regulators of leaf senescence. This is opposite of the effect of pen1 and pen1pen3 mutants that show early senescence and suggest PEN1 to be a negative regulator of leaf senescence. Our work provides initial support that PEN1-associated EVs and TET8-associated EVs may have opposite effects on soil-grown plants undergoing age-related leaf senescence.