A general pattern of trade-offs between ecosystem resistance and resilience to tropical cyclones.

Tropical cyclones drive coastal ecosystem dynamics, and their frequency, intensity, and spatial distribution are predicted to shift with climate change. Patterns of resistance and resilience were synthesized for 4138 ecosystem time series from n = 26 storms occurring between 1985 and 2018 in the Northern Hemisphere to predict how coastal ecosystems will respond to future disturbance regimes. Data were grouped by ecosystems (fresh water, salt water, terrestrial, and wetland) and response categories (biogeochemistry, hydrography, mobile biota, sedentary fauna, and vascular plants). We observed a repeated pattern of trade-offs between resistance and resilience across analyses. These patterns are likely the outcomes of evolutionary adaptation, they conform to disturbance theories, and they indicate that consistent rules may govern ecosystem susceptibility to tropical cyclones.

Effects of maternal genotypic identity and genetic diversity of the red mangrove Rhizophora mangle on associated soil bacterial communities: A field-based experiment.

Loss of plant biodiversity can result in reduced abundance and diversity of associated species with implications for ecosystem functioning. In ecosystems low in plant species diversity, such as Neotropical mangrove forests, it is thought that genetic diversity within the dominant plant species could play an important role in shaping associated communities. Here, we used a manipulative field experiment to study the effects of maternal genotypic identity and genetic diversity of the red mangrove Rhizophora mangle on the composition and richness of associated soil bacterial communities. Using terminal restriction fragment length polymorphism (T-RFLP) community fingerprinting, we found that bacterial community composition differed among R. mangle maternal genotypes but not with genetic diversity. Bacterial taxa richness, total soil nitrogen, and total soil carbon were not significantly affected by maternal genotypic identity or genetic diversity of R. mangle. Our findings show that genotype selection in reforestation projects could influence soil bacterial community composition. Further research is needed to determine what impact these bacterial community differences might have on ecosystem processes, such as carbon and nitrogen cycling.

Postglacial expansion pathways of red mangrove, Rhizophora mangle, in the Caribbean Basin and Florida.

PREMISE OF THE STUDY: The Last Glacial Maximum (LGM) was a period of massive range contraction. Post-LGM, water-dispersed coastal species, including the red mangrove (Rhizophora mangle), expanded poleward as propagules were transported by ocean currents. We assessed postglacial marine expansion pathways for R. mangle within the Caribbean Basin and Florida. METHODS: Six microsatellite loci were used to genotype 237 individuals from nine R. mangle populations in the Caribbean, Florida, and Northwest Africa. We evaluated genetic variation, population structure, gene flow along alternative post-LGM expansion pathways to Florida, and potential long-distance dispersal (LDD) from West Africa to Caribbean islands. KEY RESULTS: These R. mangle populations had substantial genetic structure (FST = 0.37, P < 0.0001) with three discrete population clusters (Caribbean mainland, Caribbean islands, and Florida). Genetic connectivity along the mainland pathway (Caribbean mainland to Florida) vs. limited gene dispersal along the Antilles Island pathway (Caribbean islands to Florida) supported Florida recolonization from Caribbean mainland sources. Genetic similarity of Northwest Africa and two Caribbean islands provided evidence for trans-Atlantic LDD. We did not find a pattern of decreasing genetic diversity with latitude. CONCLUSIONS: We outline a complex expansion history for R. mangle, with discrete pathways of recolonization for Florida and Caribbean islands. Contrary to expectation, connectivity to putative Caribbean mainland refugial populations via ocean currents, and not latitude, appears to dictate genetic diversity within Caribbean island and Florida R. mangle. These findings provide a framework for further investigation of additional water-dispersed neotropical species, and insights for management initiatives.

Nutrient enrichment intensifies hurricane impact in scrub mangrove ecosystems in the Indian River Lagoon, Florida, USA.

Mangroves are an ecological assemblage of trees and shrubs adapted to grow in intertidal environments along tropical, subtropical, and warm temperate coasts. Despite repeated demonstrations of their ecologic and economic value, multiple stressors including nutrient over-enrichment threaten these and other coastal wetlands globally. These ecosystems will be further stressed if tropical storm intensity and frequency increase in response to global climate changes. These stressors will likely interact, but the outcome of that interaction is uncertain. Here, we examined potential interaction between nutrient over-enrichment and the September 2004 hurricanes. Hurricanes Frances and Jeanne made landfall along Florida's Indian River Lagoon and caused extensive damage to a long-term fertilization experiment in a mangrove forest, which previously revealed that productivity was nitrogen (N) limited across the forest and, in particular, that N enrichment dramatically increased growth rates and aboveground biomass of stunted Avicennia germinans trees in the interior scrub zone. During the hurricanes, these trees experienced significant defoliation with three to four times greater reduction in leaf area index (LAI) than control trees. Over the long-term, the +N scrub trees took four years to recover compared to two years for controls. In the adjacent fringe and transition zones, LAI was reduced by > 70%, but with no differences based on zone or fertilization treatment. Despite continued delayed mortality for at least five years after the storms, LAI in the fringe and transition returned to pre-hurricane conditions in two years. Thus, nutrient over-enrichment of the coastal zone will increase the productivity of scrub mangroves, which dominate much of the mangrove landscape in Florida and the Caribbean; however, that benefit is offset by a decrease in their resistance and resilience to hurricane damage that has the potential to destabilize the system.