Urbanization drives the acoustic diversity of mangrove anurans and avifauna in Puerto Rico

Abstract

The mangroves of Puerto Rico occupy a broad gradient of urbanization that offers a chance to test hypotheses on urban faunal communities from both terrestrial and mangrove systems. These hypotheses state that urban avifaunal communities are less diverse, with greater representation by generalists, but that certain mangrove specialists can utilize urban landscapes. Much of this is said to be driven by food resources, with frugivores and nectarivores benefiting from abundant residential flowers and fruits, while insectivores are driven away by low food resources. This study used passive acoustic monitoring to identify the audible anuran and avifaunal species in mangroves across the urban gradient of Puerto Rico. Three anurans and twenty-four avian species were detected across all sites, with eighteen species found at the most diverse site, and six at the least diverse site. The most urban communities were more similar to each other and characterized by low diversity, especially of invertivores, mangrove specialists, and endemics. The least urban communities, however, were less like each other and more diverse than their more urban counterparts. Greater surrounding vegetation cover was the strongest overall predictor of increased faunal diversity, although urban coverage and population density were also strongly correlated with some guilds and species. Soundscape analyses showed that acoustic space use was a strong predictor of site diversity and is thus a sufficiently accurate faster alternative to detecting individual species. This will be an important tool in the continued monitoring of these forests, which may experience changes associated with ongoing urbanization and sea-level rise.

Recent Carbon Storage and Burial Exceed Historic Rates in the San Juan Bay Estuary Peri-Urban Mangrove Forests (Puerto Rico, United States)

“…The Urban Index was previously reported for the SJBE mangrove sites and was derived from five spatial variables: (1) surrounding coverage of mangrove vegetation, (2) non-mangrove vegetation and open water, (3) urban land, (4) population density, and (5) road density, which were calculated within a 500 m buffer from the approximate center of the mangrove site ( Martin et al, 2020 ; Table 1 ). The index was a relative metric of the level of urbanization with a score of 100 being the most disturbed and 1 being the least disturbed ( Branoff, 2019 , 2020b ). The Caño Martin Peña, located in the western half of the estuary, was associated with high population density, impervious surfaces, commercial and industrial development, and had a high Urban Index (88–100), while the expansive Pin in the easternmost part was scored 1 ( Martin et al, 2020 ; Table 1 ).…”

“…Potential organic matter sources were examined by plotting sediment molar C/N ratio vs sediment C stable isotopes in core sediments relative to potential organic matter sources. The source δ 13 C and C/N ratios associated with seagrass, marine algae, particulate organic matter (POM), and mangrove plant matter was based on literature values ( Khan et al, 2019 ; Branoff, 2019 ; Oczkowski et al, unpublished data). Ranges of C/N ratios and δ 13 C for mangrove-derived source material was separated into roots and leaves (green only), and further characterized by dominant species, Red ( R. mangle L.), White [ L, racemosa (L.) C.F.…”

“… Bi-plot of sediment molar C/N ratio vs sediment C stable isotopes in core sediments relative to potential organic matter sources [source δ 13 C, C/N ratios, and particulate organic matter (POM) based on Khan et al, 2019 ; Branoff, 2019 ; Oczkowski et al, unpublished data). Mangrove-derived material was separated into roots and green leaves.…”

“…Now, in the Anthropocene Epoch, with its associated stressors such as global climate change, it is more important than ever to examine the effects of local urbanization on C sequestration in coastal mangroves ( Bosire et al, 2014 ; Ochoa-Gómez et al, 2019 ). The global trends in peri-urban mangrove forests show nitrogen (N) enrichment due to human watershed activities and significantly lower C to N ratios in mangrove biomass ( Branoff, 2017 , 2019 ). In a global review of 66 dated mangrove cores, Pérez et al (2018) reported that mangrove ecosystems receiving domestic or aquaculture effluents had sediment accretion and organic carbon accumulation rates twofold and fourfold, respectively, higher than mangrove systems in conserved sedimentary environments.…”

Recent Nitrogen Storage and Accumulation Rates in Mangrove Soils Exceed Historic Rates in the Urbanized San Juan Bay Estuary (Puerto Rico, United States)

“…Worldwide and over the past century, mangrove systems have been under threat from land clearing and/or filling for agriculture, aquaculture, and urbanization purposes ( Valiela et al, 2001 ; Duke et al, 2007 ; Duke, 2011 ). Peri-urban mangroves (i.e., adjacent to urban areas) are threatened by elevated contamination from sewage and domestic wastewater inputs (i.e., household water from laundry, dishwashing, and bathing), industrial wastes, storm overflow, and sediment runoff ( Bosire et al, 2014 ; Lugo et al, 2014 ; Branoff, 2017 , 2019 ; Pérez et al, 2018 ).…”