Sunday, June 28, 2009

all washed up, reproductively

From maritima

While walking to our field site at Mt. Hope Farm in Bristol, RI on Friday, we found this jelly-like egg mass washed up in the high intertidal. I don't know if it is indeed an egg mass or what type of organism it belongs to. The photos capture it fairly well - it was nearly two feet in diameter, and made of many translucent, nodular strings. Anyone have any ideas?
From maritima

Saturday, June 13, 2009

marsh restoration in the Gulf of Mexico

Here is a photo of the type of wave protection being put on salt marsh restorations in the Gulf of Mexico, like the ones referred to in Rusty Feagin's comment. Thanks for the photo, Rusty!

Tuesday, June 9, 2009

plants vs. soil - a meaningless fight

Salt marshes and mangroves are reported to protect coasts from erosion and reduce storm surges. Salt marsh area has been correlated with reduced property damage from hurricanes along the Gulf Coast (Costanza et al. 2008, Ambio), and mangrove forest purportedly protected villages and reduced the death toll of a 1999 Indian cyclone (Das and Vincent 2009, PNAS).

However, a new study about to be published in Proceedings of the National Academy of Sciences (PNAS) reports that the soil, not the vegetation, in marshes is the important the feature preventing coastal erosion. The study, led by Rusty Feagin of Texas A&M, put large cores of marsh with and without vegetation in a wave tank and observed erosion patterns. Vegetation did not affect the rate of erosion, but sandy soils eroded more quickly than organic soils. The report questions the efficacy of salt marsh restorations that aim to prevent coastal erosion.

I look forward to reading the full publication. While I am sure it is a worthy scientific contribution, I think drawing conclusions about restoration efforts from these findings is misguided. The key about marshes is that they are biogenic - the organisms (in this case, plants) build the habitat. Were the plants not present, there would not be bare soil, but rather open water. Therefore, the idea of erosion protection from marsh soils without plants is nonsensical. Additionally, the key to maintaining the habitat is not erosion resistance, but sediment balance: how quickly sediment is added compared to the rate it is eroded. The plants likely act on the sediment addition end, even if they don't always contribute to the prevention of erosion (although they likely also do this in peaty soils, like in New England marshes). Finally, the coastal protection value of marshes comes from erosion prevention AND wave attenuation. In models, it is mostly the wave attenuation process that affords coastal protection from storms.

You can read a brief about the article published online at Nature.