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The powerful community-structuring roles of foundation species (FS) are well recognized; however, ecological interactions involving their dead structures have yet to be broadly integrated within ecological theory or ecosystem management. As interacting components of ecosystems, dead foundation species (DFS) modify environments and mediate feedbacks underpinning ecosystem resilience. DFS are vulnerable to global change and often respond differently than living FS. Changes in DFS quantity, composition, and frequency of occurrence influence habitat heterogeneity within systems and subsidy dynamics across systems, provoking far-reaching effects on biodiversity and ecosystem functions. Enhanced recognition of DFS traits and ecological roles will improve restoration outcomes, inform ecological forecasts, and guide conservation of ecosystems challenged by global change. Foundation species facilitate communities, modulate energy flow, and define ecosystems, but their ecological roles after death are frequently overlooked. Here, we reveal the widespread importance of their dead structures as unique, interacting components of ecosystems that are vulnerable to global change. Key metabolic activity, mobility, and morphology traits of foundation species either change or persist after death with important consequences for ecosystem functions, biodiversity, and subsidy dynamics. Dead foundation species frequently mediate ecosystem stability, resilience, and transitions, often through feedbacks, and harnessing their structural and trophic roles can improve restoration outcomes. Enhanced recognition of dead foundation species and their incorporation into habitat monitoring, ecological theory, and ecosystem forecasting can help solve the escalating conservation challenges of the Anthropocene. Foundation species facilitate communities, modulate energy flow, and define ecosystems, but their ecological roles after death are frequently overlooked. Here, we reveal the widespread importance of their dead structures as unique, interacting components of ecosystems that are vulnerable to global change. Key metabolic activity, mobility, and morphology traits of foundation species can either change or persist after death with important consequences for ecosystem function, biodiversity, and subsidy dynamics. Dead foundation species frequently mediate ecosystem stability, resilience, and transitions, often through feedbacks, and harnessing their structural and trophic roles can improve restoration outcomes. Enhanced recognition of dead foundation species and their incorporation into habitat monitoring, ecological theory, and ecosystem forecasting can help solve the escalating conservation problems of the Anthropocene. [ABSTRACT FROM AUTHOR]

• Barnacle density increases with increasing distance from the sediment (≥30 cm). • Shipworm damage is concentrated from 0 to 20 cm from the sediment. • Tree species with lower wood densities are more vulnerable to shipworm damage. • Drought can have strong interannual effects mediating shipworm damage in the SE US. • Copper-based paint and duct tape can effectively prevent shipworm burrowing. Annually, shipworms and other biofouling species cause millions of dollars in damage to wooden marine infrastructure across the world. Given their abundant larval supply and high dispersal potential, bioeroders and biofoulers are ubiquitous threats that shorten the lifespan of wooden docks, piers, boats and shoreline stabilization structures in coastal environments. Despite these impacts, there are no treatments that completely protect wood against shipworms and biofouling. To explore potential approaches for extending the lifespan of wooden shoreline stabilization structures, we conducted two field experiments to evaluate the resistance to shipworms and biofouling of small and large diameter branches of four trees – laurel oak (Quercus hemisphaerica) , sweetgum (Liquidambar styraciflua), crepe myrtle (Lagerstroemia spp.), and black mangrove (Avicennia germinans) – positioned at varying distances from the sediment surface in southeastern US estuaries. We discovered that the wood volume lost to shipworm burrows was concentrated near the sediment surface, more prevalent in tree species with lower wood densities, and varied markedly between years. Barnacle fouling was far higher on branches > 30 cm from the surface and on laurel oak and sweetgum branches. In a third field experiment, we tested two chemical and two non-chemical wood treatments and found chemical treatments to be more effective at deterring barnacle fouling and shipworm burrowing of wooden posts, especially beneath the sediment surface. By identifying desirable characteristics of the wood employed and elevations at which the impacts of shipworms and biofouling are especially prevalent, this experimental study informs the design of more durable wooden stabilization structures in coastal environments. [ABSTRACT FROM AUTHOR]

Legacy mining facilities pose significant risks to aquatic resources. From March 30th to April 9th, 2021, 814 million liters of phosphate mining wastewater and marine dredge water from the Piney Point facility were released into lower Tampa Bay (Florida, USA). This resulted in an estimated addition of 186 metric tons of total nitrogen, exceeding typical annual external nitrogen load estimates to lower Tampa Bay in a matter of days. An initial phytoplankton bloom (non-harmful diatoms) was first observed in April. Filamentous cyanobacteria blooms (Dapis spp.) peaked in June, followed by a bloom of the red tide organism Karenia brevis. Reported fish kills tracked K. brevis concentrations, prompting cleanup of over 1600 metric tons of dead fish. Seagrasses had minimal changes over the study period. By comparing these results to baseline environmental monitoring data, we demonstrate adverse water quality changes in response to abnormally high and rapidly delivered nitrogen loads. [Display omitted] • 186 metric tons of total nitrogen from wastewater were added to Tampa Bay. • An initial diatom bloom was observed near the release site. • Filamentous cyanobacteria were observed at high biomass. • Karenia brevis (red tide) was at high concentrations, co-occurring with fish kills. • Seagrasses were unimpacted during the six-month study period. [ABSTRACT FROM AUTHOR]

Boat traffic and resulting wakes are among the major human-mediated stressors on coastal ecosystems. Modulation of sediment transport by wakes and tides in an intertidal waterway with boat traffic is studied here. The hypothesis that boat wakes cause significant increases in sediment transport in intertidal settings is tested. Field observations of tides, currents, boat wakes and turbidity were collected on a transect within the Atlantic Intracoastal Waterway in Northeast Florida, USA. Hydrodynamic and sediment processes were evaluated by analyzing this field data set. A daily average of 60 wake events of varying energies were identified in the observations using time-frequency analysis methods. Due to differences in sediment suspension in response to each wake and unpredictable evolution of the bed state, decomposition of the effects of each individual wake on sediment is not possible. Therefore, the sediment dynamics during the periods of boat activity were compared in their entirety with the sediment dynamics during the periods of boat inactivity. Throughout the experiment, all periods of boat activity had consistently greater suspended sediment concentration near the bed compared to their preceding and succeeding periods of boat inactivity. In the first eight days of the experiment where tidal forcing was relatively similar between boat activity and inactivity periods, sediment transport rates were estimated as 0.048 m3/m/hr and 0.043 m3/m/hr during boat activity and inactivity, respectively, indicating a 12% increase in sediment transport due to boat traffic. A larger increase in sediment transport rates during boat activity compared to boat inactivity occurred over the last three days of the experiment. Volumes of sediment transported in low-tide, mid-tide and high-tide during boat activity were greater than their low-tide, mid-tide and high-tide counterparts during boat inactivity. Therefore, the results confirm the earlier mentioned hypothesis. • Boat traffic increased sediment transport rate by 12%. • Sediment transport in low-tide, mid-tide, and high-tide during boat activity were greater than their low-tide, mid-tide, and high-tide counterparts during boat inactivity. • Boat wakes must be considered to manage wetland stability in high-traffic estuaries. [ABSTRACT FROM AUTHOR]

• The process-based modeling of SWAT was extended by a machine learning algorithm. • The machine learning algorithm based multi-variable statistical analysis was performed. • Land cover percentage of forest and source areas are the identified variables. • The identified variables affect water quality with a threshold effect. • The thresholds for forest and source areas percentage are 37.47 % and 20.26 % respectively. By integrating soil and water assessment tool (SWAT) modeling and land use and land cover (LULC) based multi-variable statistical analysis, this study aimed to identify driving factors, potential thresholds, and critical source areas (CSAs) to enhance water quality in southern Alabama and northwest Florida's Choctawhatchee Watershed. The results revealed the significance of forest cover and of the lumped developed areas and cultivated crops ("Source Areas") in influencing water quality. The stepwise linear regression analysis based on self-organizing maps (SOMs) showed that a negative correlation between forest percent cover and total nitrogen (TN), organic nitrogen (ORGN), and organic phosphorus (ORGP), highlighting the importance of forests in reducing nutrient loads. Conversely, Source Area percentage was positively correlated with total phosphorus (TP) loads, indicating the influence of human activities on TP levels. The receiver operating characteristic (ROC) curve analysis determined thresholds for forest percentage and Source Area percentage as 37.47 % and 20.26 %, respectively. These thresholds serve as important reference points for identifying CSAs. The CSAs identified based on these thresholds covered a relatively small portion (28 %) but contributed 47 % of TN and 50 % of TP of the whole watershed. The study underscores the importance of considering both physical process-based modeling and multi-variable statistical analysis for a comprehensive understanding of watershed management, i.e., the identification of CSAs and the associated variables and their tipping points to maintain water quality. [Display omitted] [ABSTRACT FROM AUTHOR]

Consumers are often overlooked as key drivers of vegetation structure and ecosystem functioning in coastal wetlands. This oversight is particularly apparent in Asia, where much of the variation in coastal wetland plant growth and composition is attributed to physical stress gradients. To address this knowledge gap and quantify the relative importance of consumers in Asian coastal wetlands across temporal variation in environmental stress, we conducted a two-year experiment spanning relatively spring wet (2018) and spring dry (2019) years in which we manipulated the presence of the numerically dominant herbivorous crab, Helice tientsinensis , and evaluated its effects on Phragmites australis growth and structure in a Yellow River Delta salt marsh. In spring wetter 2018, Phragmites biomass and stem density were 75% and 34% higher in Crab Exclusion relative to Ambient Crab plots. In 2019 which experienced spring drought and elevated soil salinity, Phragmites biomass and stem density remained similarly high relative to 2018 in Crab Exclusion plots, but fell further, to only 16% and 39% of levels of 2018 observed in Ambient Crab plots. Phragmites ' inflorescences density was also significantly reduced in Ambient Crab than Crab Exclusion plots in 2019. Together, these results highlight the significant role that crab herbivores can play in regulating Phragmites in Yellow River Delta salt marshes and suggest that the magnitude of their top-down control may be amplified, although in a non-additive manner, with spring drought stress in the region. Unlabelled Image • Quantify the importance of consumers on Phragmites in a salt marsh across temporal variation in abiotic stress. • In the spring wetter year, Phragmites biomass were 75% higher in Crab Exclusion relative to Ambient Crab plots. • In the spring drought year, Phragmites biomass fell to 16% of levels of the spring wetter year in Ambient Crab plots. • The magnitude of top-down control of Phragmites may be amplified with spring drought in salt marsh of the YRD. [ABSTRACT FROM AUTHOR]