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I examine, through an extensive compilation of published reports, the nature and variability of carbon flow (i.e., primary production, herbivory, detrital production, decomposition, export, and biomass and detrital storage) in a range of aquatic and terrestrial plant communities. Communities composed of more nutritional plants (i.e., higher nutrient concentrations) lose higher percentages of production to herbivores, channel lower percentages as detritus, experience faster decomposition rates, and, as a result, store smaller carbon pools. These results suggest plant palatability as a main limiting factor of consumer metabolical and feeding rates across communities. Hence, across communities, plant nutritional quality may be regarded as a descriptor of the importance of herbivore control on plant biomass (“top‐down” control), the rapidity of nutrient and energy recycling, and the magnitude of carbon storage. These results contribute to an understanding of how much and why the trophic routes of carbon flow, and their ecological implications, vary across plant communities. They also offer a basis to predict the effects of widespread enhancement of plant nutritional quality due to large‐scale anthropogenic eutrophication on carbon balances in ecosystems.

Coastal vegetated ecosystems are acknowledged for their capacity to sequester organic carbon (OC), known as blue C. Yet, blue C global accounting is incomplete, with major gaps in southern hemisphere data. It also shows a large variability suggesting that the interaction between environmental and biological drivers is important at the local scale. In southwest Atlantic salt marshes, to account for the space occupied by crab burrows, it is key to avoid overestimates. Here we found that southern southwest Atlantic salt marshes store on average 42.43 (SE = 27.56) Mg OC·ha −1 (40.74 (SE = 2.7) in belowground) and bury in average 47.62 g OC·m −2 ·yr −1 (ranging from 7.38 to 204.21). Accretion rates, granulometry, plant species and burrowing crabs were identified as the main factors in determining belowground OC stocks. These data lead to an updated global estimation for stocks in salt marshes of 185.89 Mg OC·ha −1 ( n  = 743; SE = 4.92) and a C burial rate of 199.61 g OC·m −2 ·yr −1 ( n  = 193; SE = 16.04), which are lower than previous estimates. This study provides a comprehensive characterization of blue C for South American Atlantic salt marshes and reveals that environmental and biological variables are important for an understanding of blue C storage leading to lower global estimates.

Increases in temperature are expected to facilitate encroachment of tropical mangrove forests into temperate salt marshes, yet the effects on ecosystem services are understudied. Our work was conducted along a mangrove expansion front in Louisiana (USA), an area where coastal wetlands are in rapid decline due to compounding factors, including reduced sediment supply, rising sea level, and subsidence. Marsh and mangrove ecosystems are each known for their ability to adjust to sealevel rise and support numerous ecosystem services, but there are some differences in the societal benefits they provide. Here, we compare carbon and nitrogen stocks and relate these findings to the expected effects of mangrove encroachment on nitrogen filtration and carbon sequestration in coastal wetlands. We specifically evaluate the implications of black mangrove (Avicennia germinans) encroachment into Spartina alterniflora-dominated salt marsh. Our results indicate that black mangrove encroachment will lead to increased aboveground carbon and nitrogen stocks. However, we found no differences in belowground (that is, root and sediment) nitrogen or carbon stocks between marshes and mangroves. Thus, the shift from marsh to mangrove may provide decadal-scale increases in aboveground nitrogen and carbon sequestration, but belowground nitrogen and carbon sequestration (that is, carbon burial) may not be affected. We measured lower pore water nitrogen content beneath growing mangroves, which we postulate may be due to greater nitrogen uptake and storage in mangrove aboveground compartments compared to marshes. However, further studies are needed to better characterize the implications of mangrove encroachment on nitrogen cycling, storage, and export to the coastal ocean.

Exotic species are a growing global ecological threat; however, their overall effects are insufficiently understood. While some exotic species are implicated in many species extinctions, others can provide benefits to the recipient communities. Here, we performed a meta-analysis to quantify and synthesize the ecological effects of 76 exotic marine species (about 6% of the listed exotics) on ten variables in marine communities. These species caused an overall significant, but modest in magnitude (as indicated by a mean effect size of g  < 0.2), decrease in ecological variables. Marine primary producers and predators were the most disruptive trophic groups of the exotic species. Approximately 10% (that is, 2 out of 19) of the exotic species assessed in at least three independent studies had significant impacts on native species. Separating the innocuous from the disruptive exotic species provides a basis for triage efforts to control the marine exotic species that have the most impact, thereby helping to meet Aichi Biodiversity Target 9 of the Convention on Biological Diversity. A meta-analysis reveals that the presence of exotic species has a modest but significantly negative impact on the ecological properties of native marine communities and identifies the exotic species that exert the most harmful effects.

Tidal marshes are a key component of coastal seascape mosaics that support a suite of socially and economically valuable ecosystem services, including recreational opportunities (e.g., fishing, birdwatching), habitat for fisheries species, improved water quality, and shoreline protection. The capacity for tidal marshes to support these services is, however, threatened by increasingly widespread human impacts that reduce the extent and condition of tidal marshes across multiple spatial scales and that vary substantially through time. Climate change causes species redistribution at continental scales, changes in weather patterns (e.g., rainfall), and a worsening of the effect of coastal squeeze through sea level rise. Simultaneously, the effects of urbanization such as habitat loss, eutrophication, fishing, and the spread of invasive species interact with each other, and with climate change, to fundamentally change the structure and functioning of tidal marshes and their food webs. These changes affect tidal marshes at local scales through changes in plant community composition, complexity, and condition and at regional scales through changes in habitat extent, configuration, and connectivity. However, research into the full effects of these multi-scaled, interactive stressors on ecosystem service provision in tidal marshes is in its infancy and is somewhat geographically restricted. This hinders our capacity to quickly and effectively curb loss and degradation of both tidal marshes and the services they deliver with targeted management actions. We highlight ten priority research questions seeking to quantify the consequences and scales of human impacts on tidal marshes that should be answered to improve management and restoration plans.

New aspects and advancements in classical uncertainty propagation methods were used to develop a nutrient budget with associated uncertainty for a northern Gulf of Mexico coastal embayment. Uncertainty was calculated for budget terms by propagating the standard error and degrees of freedom. New aspects include the combined use of Monte Carlo simulations with classical error propagation methods, uncertainty analyses for GIS computations, and uncertainty propagation involving literature and subjective estimates of terms used in the budget calculations. The methods employed are broadly applicable to the mathematical operations employed in ecological studies involving step-by-step calculations, scaling procedures, and calculations of variables from direct measurements and/or literature estimates. Propagation of the standard error and the degrees of freedom allowed for calculation of the uncertainty intervals around every term in the budget. For scientists and environmental managers, the methods developed herein provide a relatively simple framework to propagate and assess the contributions of uncertainty in directly measured and literature estimated variables to calculated variables. Application of these methods to environmental data used in scientific reporting and environmental management will improve the interpretation of data and simplify the estimation of risk associated with decisions based on ecological studies.

Describing the relative magnitude and controls of herbivory and decomposition is important in understanding the trophic transference, recycling, and storage of carbon and nutrients in diverse ecosystems. We examine the variability in herbivory and decomposition between and within a wide range of aquatic and terrestrial ecosystems. We also analyze how that variability is associated with differences in net primary production and producer nutritional quality. Net primary production and producer nutritional quality are uncorrelated between the two types of system or within either type. Producer nutritional quality is correlated to the percentage of primary production consumed by herbivores or percentage of detrital production decomposed annually, regardless of whether the comparison is made between the two types of systems or within either type of system. Thus, producer nutritional quality stands out as a consistent indicator of the importance of consumers as top-down controls of producer biomass and detritus accumulation and nutrient recycling. However, absolute consumption by herbivores and absolute decomposition (both in$g C\\cdot m^{-2}\\cdot yr^{-1}$) are often associated with absolute primary production and independent of producer nutritional quality, because the variability in net primary production across systems largely exceeds that in the percentage consumed or decomposed. Thus, primary production often stands out as an indicator of the absolute flux of producer carbon transferred to consumers and of the potential levels of secondary production maintained in the system. These patterns contribute to our understanding of the variability and control of herbivory and decomposition, and implications on carbon and nutrient cycling, in aquatic and terrestrial ecosystems. Furthermore, in view of their robustness, they may offer a template for global change models seeking to predict anthropogenic effects on carbon and nutrient fluxes.

Microplastics (<5 mm) pollution is a growing problem affecting coastal communities, marine ecosystems, aquatic life, and human health. The widespread occurrence of marine microplastics, and the need to curb its threats, require expansive, and continuous monitoring. While microplastic research has increased in recent years and generated significant volumes of data, there is a lack of a robust, open access, and long-term aggregation of this data. The National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental Information (NCEI) now provides a global open access to marine microplastics data on an easily discoverable and accessible GIS web map and data portal ( https://www.ncei.noaa.gov/products/microplastics ). The objective of this data portal is to develop a repository where microplastics data are aggregated, archived, and served in a user friendly, consistent, and reliable manner. This work contributes to NCEI’s efforts towards data standardization, integration, harmonization, and interoperability among national and international collaborators for monitoring global marine microplastics. This paper describes the NOAA NCEI global marine microplastics database, its creation, quality control procedures, and future directions.

Tidal marshes are increasingly vulnerable to degradation or loss from eutrophication, land-use changes, and accelerating sea-level rise, making restoration necessary to recover ecosystem services. To evaluate effects of restoration planting density and sea-level rise on ecosystem function (i.e., nitrogen removal), we restored three marshes, which differed in elevation, at Weeks Bay National Estuarine Research Reserve, Alabama, USA and planted them with Juncus roemerianus sods at 0, 25, 50, 75, or 100% initial cover. We simulated future sea level using passive weirs that increased flooding during low tide. Because additional species emerged shortly after transplantation, we also tested for treatment effects on community structure. In all marshes, species richness increased following restoration, regardless of treatments, while relative abundances of new species tended to increase with increasing initial cover. Plant percent cover increased with increasing initial cover in all marshes, with similar vegetated cover at 50, 75, and 100% after 3 years in the highest elevation marsh. Porewater dissolved inorganic nitrogen concentrations ([DIN]) decreased with increasing initial cover in all marshes, and were significantly lower in 50, 75, and 100% treatments than 0 or 25% after 1 year. Furthermore, [DIN] was similarly low among 50, 75, and 100% treatments when elevation capital was highest. These results suggest that intermediate initial cover (50%) can recover plant cover and promote nitrogen removal when elevation capital is adequate at relatively lower labor and material costs than planting at higher cover, thereby maximizing restoration outcomes in the face of low to moderate sea-level rise.