Primary Production

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PIE LTER benthic microalgal biomass in fiddler-crab plots in a salt marsh of West Creek, Rowley, MA.


It is well known that species across the world are expanding or shifting their ranges because of climate change. Yet, we know little about their impact on the habitats they colonize. In an observational study, we examined the effect of the fiddler crab Minuca pugnax (Smith, 1870) on benthic microalgal biomass in salt marshes in its expanded range (northeastern Massachusetts, USA). We found that plots with M. pugnax had, on average, 74% lower diatom biomass and 77% lower cyanobacteria biomass than plots without M. pugnax. Our results indicate that this climate migrant can impact saltmarsh functioning by limiting benthic microalgal biomass.  

Johnson, D.S., K.S. Martínez-Soto, S. Wittyngham, M. Pant, and E. Goetz. 2020. The fiddler crab Minuca pugnax (Smith, 1870) (Decapoda: Brachyura: Ocypodidae) reduces saltmarsh algae in its expanded range. Journal of Crustacean Biology 40: 668-672

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To test the hypothesis that M. pugnax reduced benthic microalgal biomass, we selected ten plots (0.0625 m2) with fiddler crabs present (determined by the presence of burrows and either feeding pellets or crabs) and counted burrows within the plot. Each crab plot was paired with a reference plot (lacking burrows, feeding pellets, or crabs) that was 1–2 m away, for a total of 20 plots. Plot pairs were at least 10 m apart from each other due to the patchiness of M. pugnax colonies. We estimated the biomass of benthic microalgal functional groups (diatoms, cyanobacteria, and green algae) on the sediment surface with a handheld fluorometer (BenthoTorch, BBe Moldaenke, Germany) in duplicate samples within each plot.


On going collections.

Version 01: February 10, 2021, data and metadata updates to comply with importation to DEIMS7 and LTER Data Portal. Used MarcrosExportEML_HTML (working)pie_excel2007_Sep2020.xlsm 9/17/20 1:11 PM for QA/QC to EML 2.1.0.


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