The fiddlers influencing mangrove ecosystems

The types of bacteria living in and around fiddler crab burrows vary widely between mangroves, but their functional activities are remarkably similar.

Mar 11, 2019

The types of bacteria present in and around mangrove fiddler crab burrows in three different geographic locations were compared by KAUST researchers. They found that the crabs' burrowing activity changed the sediment in a way that attracted different types of bacteria across the three locations: however, the bacteria performed similar functions, such as aerobic respiration, and potential ecological services, such as turnover of organic matter.

“Mangrove crabs act like ecosystem engineers: Their burrows create radial, halo-like microbiological and geochemical modifications to the surrounding sediment compared with soil that has been left undisturbed,” says Jenny Booth, the first author of the study. “This effect was similar in all three locations, with the burrow-dwelling bacteria being taxonomically different but functionally similar,” she adds.

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The researchers estimate that the halo-like ring of biochemical and microbial changes that extend a small distance around the fiddler crab burrows can influence up to 35 percent of mangrove sediment. In Kenyan mangroves, where burrow density is very high, this effect can influence almost 80 percent of the sediment.

“We predict that the bioturbation effect of crabs and similar burrowing species has a large overall impact on mangrove ecosystems by altering the nature of the sediment’s microbiome. These changes ultimately govern environmental processes, like carbon and nutrient fluxes, in this coastal ecosystem,” says Daffonchio.

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