Environmental Engineering Reference
In-Depth Information
2012
). Explosive eruptions from the island of Montserrat in the Caribbean
appear to be linked to considerable mortality events of pteropods and planktonic
foraminifera (Wall-Palmer
et al
.,
2011
). When ash-leachate
ciently
elevated, the high buffering capacity of seawater can be overcome and induce
transient acidic conditions (Frogner
et al
.,
2001
; Jones and Gislason,
2008
).
This can increase the bioavailability of ions such as Cu
2
þ
and Al
3
þ
, which are
toxic to
fluxes are suf
fish and other organisms. A drop in pH also affects the saturation states of
CaCO
3
polymorphs, including calcite and aragonite. Consequently, organisms that
utilize CaCO
3
for shell or skeleton formation experience reduced calci
cation
rates, malformation and enhanced dissolution (Gattuso
et al
.,
1998
; Riebesell
et al
.,
2000
). Given that biogenic carbonate precipitation is dominated by phyto-
plankton, declines in these species would have a knock on effect on the food-web
structure and health. There is, however, evidence that ecosystems can become
acclimatized to such forcings, with some coccolithophore species able to produce
exudates or store toxic metals intra-cellularly in response to high transition
metal concentrations (e.g. Dupont and Ahner,
2005
).
17.4 Long-term climate impacts
Large explosive eruptions have been hypothesized as possible catalysts for
step changes in Earth
'
s climate, although this remains contentious due to the
paucity of data available (e.g. Oppenheimer,
2002
). Terrestrial surface changes,
while potentially devastating to local ecosystems, are predicted not to have a
sustained impact on global climate (Jones
et al
.,
2007
). However, there are
numerous ways in which ash deposition on land and at sea can lead to long-term
carbon removal from the atmosphere.
17.4.1 Primary productivity
One avenue for ash deposition to instigate long-term atmospheric CO
2
change is
through increased photosynthesis (
Figure 17.3L
). The weathering and dissolution
of volcanic products is an integral part of global element cycling, with the re
ux
of key nutrients to the ocean
-
atmosphere system essential to maintaining primary
productivity in both terrestrial and marine environments. Periods of Earth
'
s history
with
flare-ups of large-scale volcanism have been suggested as instigators and/or
contributors to millennial climate change through increased fertilization of
HNLC waters (e.g. Bay
et al
.,
2004
; Cather
et al
.,
2009
). While plausible, there
are several factors that are poorly quanti
ed in this hypothesis. Firstly, given the
ef
cient recycling of organic material and associated respiration in the water
column, it is unclear to what degree increased primary productivity results in
