Back To Bacteria: A “Big, Rotten Loofah”

Mangrove detritus pulled out of a sediment core at the south edge of the pond.

The surface of a rhizome mat where mangrove overstory was removed four years ago. The surface is soft, and decomposing root fibers protrude into the water. The stringy fragments in the foreground are worm waste.

More on the mangrove story: This Tuesday we took sediment cores from two areas where mangrove overstory (prop roots and trunks) were cut down in 2007 and 2008. In these areas, dead stumps still stick out of the mud, and a thick, fibrous root mat stabilizes the sediments. Even though the overstory was removed four years ago, the rhizome mat is still intact, making it relatively easy to walk on. In most areas, however, it’s riddled with burrows. This brings up an important question– what is the role of these burrowing and other bioturbators in breaking down the rhizome mat? Importantly, does mangrove-based carbon enter the food web more readily when mangrove mat is decomposing, and exposed to wind-mixed water, than when mangroves are actively building fresh (tough, tannin-rich) rhizome? This is a food web approach to mangrove community effects, and a very interesting one. Previous studies suggest that short term carbon cycling in mangrove sediments is dominated by bacteria at first, then macrofauna (crustaceans, worms, mollusks, nematodes), and then back to bacteria (Sweetman et al. 2010). Additionally, in living mangroves in Kaneohe Bay, mangrove-based carbon isn’t taken up into the food web (Demopoulos et al. 2007). Perhaps when crabs and other burrowers are more actively breaking down mangrove material, there are more opportunities for mangrove carbon to subsidize the local food web. This is a question for stable isotopes.

Sweetman, A., Middelburg, J., Berle, A., Bernardino, A., Schander, C., Demopoulos, A., & Smith, C. (2010). Impacts of exotic mangrove forests and mangrove deforestation on carbon remineralization and ecosystem functioning in marine sediments Biogeosciences Discussions, 7 (2), 2631-2671 DOI: 10.5194/bgd-7-2631-2010

Demopoulos AW, Fry B, & Smith CR (2007). Food web structure in exotic and native mangroves: a Hawaii-Puerto Rico comparison.Oecologia, 153 (3), 675-86 PMID: 17587064

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  • Mahalo Nui Loa

    I recently graduated from the Donahue Lab at the University of Hawai'i at Manoa and am currently a graduate student at the University of Washington. This research is funded by a Graduate Research Fellowship from the National Science Foundation, as well a scholarship from the Seattle chapter of the Achievement Rewards for College Scientists (ARCS) Foundation.
  • “Where do ecological ideas come from? …Most do not spring deductively from the minds of ecologists, like Athena from the head of Zeus. Instead, they emerge when ecologists absorb the essential spirit of individual places– their genius loci.”

    ~Mary V. Price & Ian Billick, "The Ecology of Place"
  • “Aloha is the intelligence with which we meet life.”

    ~Olana A'i, Kumu Hula

  • “I no longer say ‘Hawaiian ways of knowing’ anymore. Because people relegate that to the margins. ‘Ways of knowing,’ as if it’s a quaint, anthropologic way of describing something outside us. No, it’s ‘epistemology,’ the philosophy of knowledge. Land educates. ‘Ike ‘aina. The land of your birth educates you. This land here educates you.”

    ~Manu Meyer

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