The role of multiple stressors in a dwarf red mangrove (Rhizophora mangle) dieback

2020 
Abstract Mangroves are habitat-forming foundation species that provide the framework for entire coastal communities. Unfortunately, mangrove forests are declining globally, often due to multiple stressors. We report a recent mangrove dieback on Abaco Island, The Bahamas which appears to be the result of multiple stressors. First, we investigated the role of hurricane and drought events in relation to green vegetation in the dieback area, as measured using Normalized Difference Vegetation Index (NDVI). We used historical Landsat imagery of the dieback region from 1989 to 2013 to identify changes in green vegetation and to determine when the dieback likely began. We determined that the dieback began around 2008, but found little evidence of a relationship between NDVI and hurricane or drought events, particularly in relation to the estimated start of the dieback. Preliminary observations in the dieback area suggested grazing by leaf chewing organisms and disease were both present at high levels. We surveyed individual mangrove trees to determine the intensity of leaf chewing herbivory and foliar disease on mangroves in the dieback area. We found leaf chewing herbivory ranged from 0 to 79%, with a mean of 29% of leaves chewed per tree and disease incidence ranged from 0% to 97% with a mean of 47%. Finally, we conducted a simulated grazing experiment to test if experimental opening mimicking grazing could facilitate disease infection in mangrove plants. Experimental opening of plant tissues showed that grazing can increase disease. Our results suggest that drought and hurricanes did not initiate this dieback, but that herbivory likely facilitated the spread of disease which may have contributed to the dieback.
    • Correction
    • Source
    • Cite
    • Save
    • Machine Reading By IdeaReader
    60
    References
    4
    Citations
    NaN
    KQI
    []