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4. Acidification and loss of biodiversity
Figure 5
Acidification is caused by the increase in region of the east-southeast platform where
the absorption of atmospheric CO by the they are found. banks of rhodoliths (red cal-
ocean, causing changes in the chemistry of careous algae) are made (Figure 6).
seawater, namely: i) decrease in water pH, Overall, almost all major coral reef sys-
caused by the reaction of dissolved CO2 tems (shallow and deep) are vulnerable to
with water, ii) decrease in the availability of climate change with regional differences in
0 0
carbonate ions [CO3(2-)] and the calcium their sensitivities and projected global loss-
carbonate saturation index (Ω). Carbonate es reaching over 70% even under the min-
ions are essential for marine organisms that imum global warming scenario (Represen-
15 S produce calcium carbonate structures in tative Concentration Pathway 2.6 W/m2,
0
the form of aragonite and calcite (CaCO3), or RCP2.6, BINDOFF et al., 2019). Warm-
30 S such as corals, bivalve and gastropod mol- ing oceans, acidification, rising sea levels
0
lusks, calcareous macroalgae, in addition and intensifying storms impede greater
to certain primary planktonic producers, resilience of reefs globally and increase
45 S such as coccolithophorids (DONEY et al., their destruction. Shallow coral reefs that
0
30 W 0 W 2009). According to the latest global car- are not degraded by other impacts, such
0
0
60 W bon balance (FRIEDLINGSTEIN et al., 2021), as extensive bottom trawling and nutrient
0
the oceanic CO2 sink captured an average enrichment, can provide an important ref-
Accumulated Intensity Trend (ºC per decades) of 26% of global CO2 emissions into the uge for reefs degraded by climate change.
atmosphere in the decade 2011-2020, and The loss of deepwater coral reef habitat is
-20 -10 0 10 20 in the year 2021, it is estimated that has virtually certain, considering the projection
assimilated about 2.9 GtC a-1. of increasing ocean acidification (BINDOFF
Source: Reynolds et al., 2007 According to the IPCC’s Sixth Climate et al., 2019). In addition to ocean acidifi-
Assessment Report (AR6 – WGI and WGII), cation and warming, ecosystem fragmen-
Figure 5. Trend of cumulative intensity multiplied by the intensity of the tem-
of MHW events for the period 1982- perature increase in the day (value of it is virtually certain that ocean acidification tation and pollution in coastal regions are
2020 during the summer months (De- the sea surface temperature anomaly). will continue to occur under all CO2 emis- other major threats to marine ecosystems
cember to February). Units are in ˚C The data for the calculation was taken sion scenarios (IPCC, 2021; 2022) through- across the planet (IPCC, 2022).
per decade. Cumulative intensity is the from the Optimum Interpolation Sea out the 21st century. However, the acidifica- Regarding the effects of acidification,
sum of the number of days of MHWs Surface Temperature tion rate will be due to the amount of CO2 coastal regions can respond to excess CO2
emitted in future years. It can be stated with dissolved in seawater in a heterogeneous
high reliability that climate change, includ- way, since other processes, such as eutro-
ing acidification, has already caused chang- phication, can amplify or partially mitigate
with oxygen depletion during the summer the frequency and intensity of COMs is one es in coastal and oceanic ecosystems (IPCC, the effect of acidification, notably through
of 2020. Carneiro et al. (2020) showed of the factors for the decline of this bivalve 2022). Among the most vulnerable Brazilian increased primary production. location
that the bivalve Anomalocardia flexuosa, in recent decades. MHWs also affect oys- ecosystems, according to the 2016 assess- (CAI et al., 2011; COTOVICZ et al., 2022).
of economic and cultural importance for ter cultivation in the region, responsible for ment carried out by the Brazilian Research However, the potential aspect of mitiga-
the region, is quite sensitive to temperature a movement of BRL 29,709,300.00 (US$ Network on Ocean Acidification – BrOA tion through eutrophication must be care-
increases. It is believed that the increase in 13.81 million), to the state (SEBRAE, 2018). (KERR et al., 2016), are coral reefs and the fully examined, as the natural variability of

412 BLUE ECONOMY Ocean and Climate: New Challenges 413