Coastal Wildfires May Nurture Marine Life Off Shore

robertmcgrath

Dec 16

Last summer, much of North America was covered by plumes of smoke from wildfires, often thousands of KM distant. This was a nuisance and sometimes a health hazard.

In and near the burn areas, it wasn't just smoke, the fallout included ash, which fell to the surface.

The fires were very destructive, scarring the landscape in the near term, and releasing Carbon into the atmosphere.

However, in the medium term, the ash and other remains also nourish the surface where they fall, fertilizing new growth of plants and microorganisms.

This winter, researchers at UC Santa Barbara report a study of the effects of a large wildfire that occurred in 2017 [1]. The Thomas fire burned for a month, scarring over 1000 square KM of California. The smoke plume extended more than 1000 KM offshore, so the impact extended to the ocean as well. Nutrients also run off in streams and rivers that eventually discharge into the ocean.

A satellite image of the Thomas Fire's burn scar and active flames on December 7, 2017. UCSB researchers just published a study on the impact of wildfire ash on marine life. Image credit: Joshua Stevens/NASA Earth Observatory (From [2])

The study sampled ash from the fire, and measured the effects of such ash on ocean ecologies. The gasses and windborne ash will fall to the surface of the ocean, and then sink and be transported by currents. This means there will be local areas with a lot of ash or smoke for a short time. Chemicals will dissolve into the water, and then disperse, depending on gravity and currents.

Their experiments show that the chemicals leached from these ash falls are nutrient rich. They estimate that the Thomas fire delivered tens of thousands of kilograms of Nitrogen to the near buy ocean.

This is a tiny amount of the total Nitrogen, but it arrived at a time when upwelling was low, so this was a significant, if short, boost for the productivity of the area. Their study indicates that the effects would feed a broad range of organisms. They also found no evidence of toxicity, at least in this study.

"Our findings suggest that large wildfires can be important sources of nitrogen and other nutrients to coastal marine ecosystems where they can fuel productivity and maintain a highly diverse protistan community assemblage."

([1], p. 9)

If this study is confirmed by other research, then we know that large fires on land probably aren't hurting coastal ecosystems, and may be providing short bursts of growth in some cases.

T. M. Ladd, D. Catlett, M. A. Maniscalco, S. M. Kim, R. L. Kelly, S. G. John, C. A. Carlson, and M. D. Iglesias-Rodríguez, Food for all? Wildfire ash fuels growth of diverse eukaryotic plankton. Proceedings of the Royal Society B: Biological Sciences, 290I (2010) November 8 2023. https://doi.org/10.1098/rspb.2023.1817
Beth Thornton, UCSB study shows ash from Thomas Fire added nutrients for marine life, in KCBX News, December 11, 2023. https://www.kcbx.org/environment-and-energy/2023-12-11/ucsb-study-shows-ash-from-thomas-fire-added-nutrients-for-marine-life