Impact of Global Change on Nutrient Dynamics in Mangrove Forests

Alongi, Daniel M.

doi:10.3390/f9100596

Cited by 144 publications

(94 citation statements)

References 56 publications

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“…Mangroves ecosystems are increasingly challenged by anthropogenic activities, which may result in pressure to these ecosystems in terms of increasing nutrient or organic matter loading 80 . Under the pristine conditions of Cananéia region 39 , crab’s biofilm microbiota may be dominated by diazotrophic members, contributing fixed N to the environment, and possibly to the host.…”

Section: Discussionmentioning

confidence: 99%

N2 fixation dominates nitrogen cycling in a mangrove fiddler crab holobiont

Žilius

Bonaglia

Broman

et al. 2020

Sci Rep

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Mangrove forests are among the most productive and diverse ecosystems on the planet, despite limited nitrogen (N) availability. Under such conditions, animal-microbe associations (holobionts) are often key to ecosystem functioning. Here, we investigated the role of fiddler crabs and their carapaceassociated microbial biofilm as hotspots of microbial N transformations and sources of N within the mangrove ecosystem. 16S rRNA gene and metagenomic sequencing provided evidence of a microbial biofilm dominated by Cyanobacteria, Alphaproteobacteria, Actinobacteria, and Bacteroidota with a community encoding both aerobic and anaerobic pathways of the N cycle. Dinitrogen (N 2) fixation was among the most commonly predicted process. Net N fluxes between the biofilm-covered crabs and the water and microbial N transformation rates in suspended biofilm slurries portray these holobionts as a net N 2 sink, with N 2 fixation exceeding N losses, and as a significant source of ammonium and dissolved organic N to the surrounding environment. N stable isotope natural abundances of fiddler crab carapace-associated biofilms were within the range expected for fixed N, further suggesting active microbial N 2 fixation. These results extend our knowledge on the diversity of invertebratemicrobe associations, and provide a clear example of how animal microbiota can mediate a plethora of essential biogeochemical processes in mangrove ecosystems. Among coastal ecosystems, mangrove forests are of great importance as they account for three quarters of the tropical coastline and provide different ecosystem services 1,2. Mangrove ecosystems generally act as a net sink of carbon, although they release organic matter to the sea in the form of dissolved refractory macromolecules, leaves, branches and other debris 3,4. In pristine environments, mangroves are among the most productive ecosystems on the planet, despite growing in tropical waters that are often nutrient depleted 5. The refractory nature of the organic matter produced and retained in mangroves can slow the recycling of nutrients, particularly of nitrogen (N) 3,6. Nitrogen limitation in such systems may be overcome by microbial dinitrogen (N 2) fixation when combined with high rates of bioturbation by macrofauna 7,8. Bioturbation by macrofauna affect N availability and multiple N-related microbial processes through sediment reworking, burrow construction and bioirrigation, feeding and excretion 9. Macrofauna mix old and fresh organic matter, extend oxic-anoxic sediment interfaces, increase the availability of energy-yielding electron acceptors and increase N turnover via direct excretion 10,11. Thus, macrofauna may alleviate N limitation by priming the remineralization of refractory N, reducing plants-microbe competition 12,13. Such activity ultimately promotes N-recycling, plant assimilation and high N retention, as well as favours it loss by stimulating coupled nitrification and denitrification 14. Mangrove sediments are highly bioturbated by decapods such as crabs 15. Crab populations ...

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Section: Discussionmentioning

confidence: 99%

N2 fixation dominates nitrogen cycling in a mangrove fiddler crab holobiont

Žilius

Bonaglia

Broman

et al. 2020

Sci Rep

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“…Nitrogen (N) availability is an important limiting factor for the growth, productivity and distribution of mangroves in intertidal regions [10]. In contrast to terrestrial ecosystems, nitrification and micro-formation of NO 3 − in the sediments of mangroves are greatly inhibited [11][12][13][14]. Consequently, most inorganic N in mangrove sediments exists in the NH 4 + form [15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Effects of Salt on Root Aeration, Nitrification, and Nitrogen Uptake in Mangroves

Zhao

Wang

et al. 2019

Forests

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The potential effects of salt on the growth, root anatomy, radial oxygen loss (ROL), and nitrogen (N) dynamics in mangroves were investigated using the seedlings of Avicennia marina (Forsk.) Vierh. The results showed that a moderate salinity (200 mM NaCl) appeared to have little negative effect on the growth of A. marina. However, higher salt stresses (400 and 600 mM NaCl) significantly inhibited the biomass yield. Concentrations of N in the roots and leaves decreased sharply with increasing salinity. Nevertheless, the presence of salt directly altered root anatomy (e.g., reduced root porosity and promoted suberization within the exodermis and endodermis), leading to a significant reduction in ROL. The results further showed that reduced ROL induced by salt could restrain soil nitrification, resulting in less ammonia-oxidizing archaea and bacteria (AOA and AOB) gene copies and lower concentrations of NO3− in the soils. While increased root suberization induced by salt inhibited NH4+ and NO3− uptake and influx into the roots. In summary, this study indicated that inhibited root aeration may be a defense response to salt, however these root symptoms were not advantageous for rhizosphere nitrification and N uptake by A. marina.

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“…At times, water temperature in Soliman Bay was ~18˚C hotter. Such an extreme water temperature will place very high physiological demands on the flora (Alongi 2018) Benoît et al (2000) report that mosquitofish prefer habitats with lots of cover to avoid predation, but Casterlin & Reynolds (1977) report that mosquitofish do not favour such habitats. Our study highlights that mosquitofish behaviour is driven by water temperature and availability of a mangrove root refuge from predation.…”

Section: Discussionmentioning

confidence: 99%

Mosquitofish avoid thermal stress by moving from open water to the shade of the mangrove Rhizophora mangle

Hendy¹,

Burt

Clough

et al. 2020

Mar. Ecol. Prog. Ser.

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Mangrove trees provide environmental buffering for animals by reducing daytime water thermal maxima. Shade from Rhizophora mangle trees reduces thermal stress for the mosquitofish Gambusia affinis. Data were collected from mangrove forests in Quintana Roo, Mexico, at 2 sites: (1) Soliman Bay, a mangrove forest decoupled from direct ocean water, and (2) La Lunita with semi-direct access to ocean water. During cooler morning hours at Soliman Bay, large numbers of mosquitofish foraged in open channels. At the same time, few mosquitofish utilised shaded areas within the R. mangle prop roots. When channels exceeded water temperatures above 38°C, mosquitofish migrated into the shaded areas provided by R. mangle trees. Channel water reached a daytime maximum temperature of 46°C, while daytime-shaded R. mangle areas remained 6.2°C cooler. Temperature rise and abundance shifts were not found in La Lunita, which has water temperatures of 27 to 28°C throughout the day. Size distributions between both localities showed mosquitofish caught in Soliman Bay to be >10% smaller than the mosquitofish from La Lunita, which had a greater abundance of mature adults. In Soliman Bay, mosquitofish were small, and the thermal stresses may impose serious developmental impacts that would be reduced by occupying water shaded by R. mangle. Refuge from R. mangle provides environmental buffering for fish, and future increasing water temperatures may reveal a greater use of this little-known mechanism. This study provides an example of a mechanism whereby mangroves support intertidal biodiversity through environmental buffering.

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Impact of Global Change on Nutrient Dynamics in Mangrove Forests

Cited by 144 publications

References 56 publications

N2 fixation dominates nitrogen cycling in a mangrove fiddler crab holobiont

N2 fixation dominates nitrogen cycling in a mangrove fiddler crab holobiont

Effects of Salt on Root Aeration, Nitrification, and Nitrogen Uptake in Mangroves

Mosquitofish avoid thermal stress by moving from open water to the shade of the mangrove Rhizophora mangle

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