International Journal of Marine Science, 2024, Vol.14, No.3, 231-244 http://www.aquapublisher.com/index.php/ijms 236 4.3 Effects on ecosystem services The impacts of ocean acidification extend to ecosystem services, which are the benefits humans derive from marine ecosystems. Coral reefs, which provide coastal protection, tourism opportunities, and fisheries habitats, are particularly at risk. As acidification weakens coral structures, the associated ecosystem services diminish, leading to increased coastal erosion, reduced fishery yields, and loss of biodiversity (Lemasson et al., 2017). Similarly, the degradation of shellfish populations affects water filtration services, as species like oysters and mussels play crucial roles in maintaining water quality. The economic implications are significant, particularly for communities dependent on marine resources for their livelihoods (Zunino et al., 2021). The cumulative effects of acidification on ecosystem services highlight the urgent need for mitigation and adaptation strategies to preserve the functionality and benefits of marine ecosystems. 5 Socioeconomic Impacts 5.1 Effects on fisheries and aquaculture Ocean acidification has wide-ranging socioeconomic impacts, affecting fisheries, coastal communities, and the broader economy. This section explores these impacts in detail. Ocean acidification poses a significant threat to fisheries and aquaculture, particularly those dependent on calcifying organisms such as shellfish. Shellfish, including oysters, mussels, and clams, rely on calcium carbonate for their shells. Reduced carbonate ion availability due to acidification makes it harder for these organisms to build and maintain their shells, leading to increased mortality and reduced growth rates. For instance, the oyster industry on the Pacific coast of North America has already experienced substantial economic losses due to increased larval mortality linked to acidified conditions (Clements and Chopin, 2017). This reduction in shellfish populations directly impacts aquaculture operations and wild capture fisheries, leading to decreased yields and significant economic losses. The Atlantic sea scallop fishery, a high-value industry in the United States, is projected to see a significant decline in biomass under high CO2 emissions scenarios. Under a high CO2 emissions scenario (RCP8.5), sea scallop biomass could decline by more than 50% by the end of the century, which would drastically reduce industry landings and revenues (Rheuban et al., 2018) (Figure 3). Similarly, Europe, a significant producer of marine mollusks, could face annual economic impacts exceeding $1 billion by 2100, with countries like France, Italy, and Spain being the most affected (Narita and Rehdanz, 2017). These economic impacts highlight the need for robust mitigation and adaptation strategies to protect fisheries and aquaculture industries from the adverse effects of ocean acidification. Figure 3 shows contour plots of biomass at three different time points (2020, 2050, and 2100) for RCP8.5 (left panels) and RCP4.5 (right panels). The X-axes represent increasing management levels from low to high: no set catch limit (None), allowable biological catch limits only (Low), ABC and variable fishing mortality at maximum sustainable yield (YPR, Medium), and ABC, YPR, and an additional 10% closed area (High). The Y-axes represent increasing ocean acidification impacts from no impact to high impacts: no ocean acidification impacts, larval impacts only (L), larvae and growth rate impacts (L+G), and larvae, growth, and predation (L+G+P). Biomass is shown in units of 1000 metric tons (mT). The contour lines in the plots illustrate the distribution of biomass under different management levels and ocean acidification impacts. In the RCP8.5 scenario, biomass gradually decreases over time (from 2020 to 2100), with this trend being more pronounced under low management levels and high ocean acidification impacts. Conversely, in the RCP4.5 scenario, even by 2100, biomass remains at relatively high levels under high management levels and lower ocean acidification impacts. These plots clearly indicate that both management measures and ocean acidification impacts jointly influence future biomass changes. Under no or low management levels, the negative impacts of ocean acidification are more significant, while strengthening management measures (such as increasing closed areas) can mitigate these negative impacts to some extent, particularly in the RCP4.5 scenario. 5.2 Implications for coastal communities Coastal communities that depend on fisheries and aquaculture are particularly vulnerable to the impacts of ocean acidification. These communities often rely on the marine environment for their livelihoods, food security, and
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