Knowledge and implications of global change in the oceans for biology, ecology, and ecosystem services - Ocean Sustainability in the 21st Century - page 147

4.5 Effects of climate change on marine mucilage
Worldwide, the highly productive and shallow Adriatic Sea (and particularly its northern
portion) within the Mediterranean basin is the area most severely affected by the outbreak
of massive marine mucilage (Danovaro et al., 2009 ). Mucilage is made of exopolymeric
compounds with highly colloidal properties that are released by marine organisms through
different processes, including phytoplankton exudation of photosynthetically derived carbo-
hydrates produced under stressful conditions (Fonda Umani et al., 2005 ; Degobbis et al.,
1995 ) . Marine mucilage floating on the surface or in the water column can display a long
life span (up to 2-3 months) and once settled on the sea bottom, these large aggregates coat
the sediments, extending in certain cases for kilometres and causing hypoxic and/or anoxic
conditions (Precali et al., 2005 ) . The consequent suffocation of benthic organisms (includ-
ingbottomassociatednekton)(Danovaro et al., 2005 )provokesseriouseconomicdamageto
tourism and fisheries (Rinaldi et al., 1995 ) . Mucilage is not closely associated with the pres-
ence of eutrophic conditions, as several mucilage outbreaks have recently been observed in
oligotrophic seas, such as the Aegean Sea. Moreover, the frequency of mucilage outbreaks
in the Adriatic Sea has increased in the last two decades concurrently with a significant de-
crease in primary production (Danovaro et al., 2009 ).Recently an analysis based ona record
of approximately 60 years of mucilage appearance in the Mediterranean Sea (1950-2008)
has revealed that patterns of climate anomalies (e.g. the positive anomaly of surface tem-
perature) explained a large proportion of variance in mucilage outbreaks, on an annual and
decadal basis. If the mucilage phenomenon continues to increase in frequency and dura-
tion, and to spread around the coastal areas of the Mediterranean Sea, an increased stress
for benthic ecosystems (anoxia) can occur with important consequences for the biodiversity,
goods, and services of the areas influenced by these events. Moreover, marine diseases may
result with potential consequences to human health (Patz et al., 2005 ) . Mucilage can be pro-
posed as a potentially novel paradigm of ecosystem alteration caused by the synergistic ef-
fect of climate change and misuse of marine resources. Mucilage on one hand represents a