Wernberg T and Filbee-Dexter K (2018), Grazers extend blue carbon transfer by slowing ...

ECB-ART-46770

Sci Rep 2018 Nov 21;81:17180. doi: 10.1038/s41598-018-34721-z.

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Grazers extend blue carbon transfer by slowing sinking speeds of kelp detritus.

Wernberg T , Filbee-Dexter K .

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Marine plant communities such as kelp forests produce significant amounts of detritus, most of which is exported to areas where it can constitute an important trophic subsidy or potentially be sequestered in marine sediments. Knowing the vertical transport speed of detrital particles is critical to understanding the potential magnitude and spatial extent of these linkages. We measured sinking speeds for Laminaria hyperborea detritus ranging from whole plants to small fragments and sea urchin faecal pellets, capturing the entire range of particulate organic matter produced by kelp forests. Under typical current conditions, we determined that this organic material can be transported 10 s of m to 10 s of km. We show how the conversion of kelp fragments to sea urchin faeces, one of the most pervasive processes in kelp forests globally, increases the dispersal potential of detritus by 1 to 2 orders of magnitude. Kelp detritus sinking speeds were also faster than equivalent phytoplankton, highlighting its potential for rapid delivery of carbon to deep areas. Our findings support arguments for a significant contribution from kelp forests to subsidizing deep sea communities and the global carbon sink.

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Genes referenced: LOC100887844 LOC100893907 LOC115925415

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References [+] :

Cebrian, Patterns in the Fate of Production in Plant Communities. 1999, Pubmed

	Figure 1. Kelp detrital particles (Laminaria hyperborea) from Malangen, northern Norway. (a) Accumulation of sea urchin faeces in a small depression, (b) small resuspended fragments, (c) whole blade at the bottom of the fjord (400 m depth), (d) medium sized fragments on a sandy bottom, (e) accumulation of fragments attached to, and consumed by, sea urchins (Strongylocentrotus droebachiensis), and (f) a whole plant being shredded by sea urchins. (Photos: (c) K. Filbee-Dexter, all other T. Wernberg).
	Figure 2. Sinking speeds of different kelp detrital particles against (a) area and (b) biomass (log scales).
	Figure 3. Coefficient of variation (CV) between sinking speeds measured for repeated drops (n = 3) of large particles. Boxes show the lower and upper quartile values and the thick line indicates the median (n = 10 for whole plants and old blades, n = 20 for stipes and blades). The whiskers correspond to 1.5 interquartile range (IQR ~ the 95% confidence interval) and the black dots represent observations outside this range.
	Figure 4. Export distances for detrital particles over the range of sinking speeds measured in this study (slowest sea urchin faeces to fastest stipe), and under different horizontal current speeds. Black lines are average ± SD for faeces, whole blades, and stipes (Table 1). Note: whole thalli have similar sinking speeds as stipes (Table 1).