Resistance, resilience, and recovery of salt marshes in the Florida Panhandle following Hurricane Michael

Characterizing the fragility, resistance, and resilience of marshes is critical for understanding their role in reducing storm damages and for helping to manage the recovery of these natural defenses. This study uses high-resolution aerial imagery to quantify the impacts of Hurricane Michael, a category 5 hurricane, on coastal salt marshes in the Florida Panhandle, USA. Marsh damage was classified into several categories, including deposition of sediment or wrack, fallen trees, vegetation loss, and conversion to open water. The marshes were highly resistant to storm damages even under extreme conditions; only 2% of the 173,259 km2 of marshes in the study area were damaged—a failure rate much lower than that of artificial defenses. Marshes may be more resistant than resilient to storm impacts; damaged marshes were slow to recover, and only 16% of damaged marshes had recovered 6 months after landfall. Marsh management mattered for resistance and resilience; marshes on publicly-managed lands were less likely to be damaged and more likely to recover quickly from storm impacts than marshes on private land, emphasizing the need to incentivize marsh management on private lands. These results directly inform policy and practice for hazard mitigation, disaster recovery, adaptation, and conservation, particularly given the potential for more intense hurricane landfalls as the climate changes.

Marsh Restoration: Ribbed Mussels (Geukensia demissa) as a Revival Mechanism to Rebuild the Coastal Salt Marshes of Long Island, New York

Hurricane severity and frequency have been exacerbated by 190 years of anthropogenic climate change. In 2012, Superstorm Sandy decimated Long Island, a 190-kilometer-long island in southeast New York, with up to 4 meters of saltwater inundation due to storm surge, resulting in the highest levels of destruction since the 1938 “Long Island Express.” Sandy was the fifth most costly hurricane on record, after Katrina in 2005, and Harvey, Maria, and Irma in 2017. Synthetic storm-surge barriers such as concrete-and-steel tidal gates are exorbitantly costly to construct and decrease biodiversity by barring habitat expansion. Natural storm barriers, termed “living shorelines,” have recently been suggested as an alternative, owing to their structurally resilient and regenerative properties. Coastal marshes, one type of natural barrier, are key to holding back storm surge; however, the contiguous United States lost coastal wetlands at 0.15 percent per year from 1998 through 2009, the final year for which the data were available. This study investigated ribbed mussels (Geukensia demissa) as a potential regenerative component of living shorelines. Transects and environmental energetic measurements were applied to draw conclusions between mussel abundance and scarcity and coastline erosion in the waters off Freeport, Long Island. It was discerned that the current rate of marsh disintegration on Long Island is 6.5 to 20 times greater than the national rate, as last measured a decade ago, and certain Long Island regions are projected to lose all coastal wetlands by 2079.

The Eastern Nebraska Salt Marsh Microbiome Is Well Adapted to an Alkaline and Extreme Saline Environment

The Eastern Nebraska Salt Marshes contain a unique, alkaline, and saline wetland area that is a remnant of prehistoric oceans that once covered this area. The microbial composition of these salt marshes, identified by metagenomic sequencing, appears to be different from well-studied coastal salt marshes as it contains bacterial genera that have only been found in cold-adapted, alkaline, saline environments. For example, Rubribacterium was only isolated before from an Eastern Siberian soda lake, but appears to be one of the most abundant bacteria present at the time of sampling of the Eastern Nebraska Salt Marshes. Further enrichment, followed by genome sequencing and metagenomic binning, revealed the presence of several halophilic, alkalophilic bacteria that play important roles in sulfur and carbon cycling, as well as in nitrogen fixation within this ecosystem. Photosynthetic sulfur bacteria, belonging to Prosthecochloris and Marichromatium, and chemotrophic sulfur bacteria of the genera Sulfurimonas, Arcobacter, and Thiomicrospira produce valuable oxidized sulfur compounds for algal and plant growth, while alkaliphilic, sulfur-reducing bacteria belonging to Sulfurospirillum help balance the sulfur cycle. This metagenome-based study provides a baseline to understand the complex, but balanced, syntrophic microbial interactions that occur in this unique inland salt marsh environment.

Ecological parameter reductions, environmental regimes, and characteristic process diagram of carbon dioxide fluxes in coastal salt marshes

We investigated the ecological parameter reductions (termed “similitudes”) and characteristic patterns of the net uptake fluxes of carbon dioxide (CO2) in coastal salt marshes using dimensional analysis method from fluid mechanics and hydraulic engineering. Data collected during May–October, 2013 from four salt marshes in Waquoit Bay and adjacent estuary, Massachusetts, USA were utilized to evaluate the theoretically-derived dimensionless flux and various ecological driver numbers. Two meaningful dimensionless groups were discovered as the light use efficiency number (LUE = CO2 normalized by photosynthetically active radiation) and the biogeochemical number (combination of soil temperature, porewater salinity, and atmospheric pressure). A semi-logarithmic plot of the dimensionless numbers indicated the emergence of a characteristic diagram represented by three distinct LUE regimes (high, transitional, and low). The high regime corresponded to the most favorable (high temperature and low salinity) condition for CO2 uptake, whereas the low regime represented an unfavorable condition (low temperature and high salinity). The analysis identified two environmental thresholds (soil temperature ~ 17 °C and salinity ~ 30 ppt), which dictated the regime transitions of CO2 uptake. The process diagram and critical thresholds provide important insights into the CO2 uptake potential of coastal wetlands in response to changes in key environmental drivers.