Environmental Engineering Reference
In-Depth Information
Figure 17.6 An ash-laden lahar/jökulhlaup arrives in the coastal waters of
southern Iceland during the Eyjafjallajökull eruption, 14 April 2010. Image
courtesy of Thórdís Högnadóttir (
©
). A black and white version of this
deposition of volcanic ash could enhance CO
2
removal from the atmosphere by
increasing the strength of the biological carbon pump (Spirakis,
1991
; Sarmiento,
1993
), i.e. the
fixation of gaseous CO
2
as organic carbon and as solid CaCO
3
,
and subsequent sinking and removal from the surface ocean upon death. There are
now a range of studies that support volcanic ash as a fertilizer in a range of ocean
surface waters (e.g. Uematsu
et al
.,
2004
; Hamme
et al
.,
2010
; Achterberg
et al
.,
2013
), with anecdotal evidence of the potential for a food-web response (Olgun
et al
.,
2013
). The best candidates for a large increase in biological activity
following ash deposition are surface waters with high nutrients and low chloro-
phyll (HNLC), essentially waters that are limited by the availability of one or
several key nutrients (Duggen
et al
.,
2010
). The utilization of nutrients depends
on the biologically limiting factors within the ecosystem, and any subsequent
impact will vary greatly with the depositional environment.
17.3.3 Poisoning
Some ingredients in the cocktail of elements released are inhibitory to biological
growth, including many that are nutrients at lower concentrations (Brand
et al
.,
1986
; Bruland
et al
.,
1991
). Toxicity thresholds vary considerably between
species, with diatoms appearing to fare better than coccolithophores and cyano-
bacteria in response to toxic-metal release (Hamme
et al
.,
2010
; Hoffmann
et al
.,
