Banca de QUALIFICAÇÃO: VITORIA ERICA DIAS AVELINO DA SILVA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : VITORIA ERICA DIAS AVELINO DA SILVA
DATE: 29/08/2025
TIME: 13:30
LOCAL: Google Meet
TITLE:

Can plastic pollution amplify the impacts of ocean acidification on coral metabolism?

KEY WORDS:

Carbonate system; aragonite saturation; calcification; microplastic; Siderastrea stellata.

PAGES: 36
BIG AREA: Ciências Biológicas
AREA: Ecologia
SUMMARY:

Plastic pollution and ocean acidification are among the main global threats to marine ecosystems. Ocean acidification reduces the availability of carbonate ions dissolved in seawater, which are the primary building blocks for coral skeletons. Plastic degradation can amplify these effects by releasing additional carbon dioxide through both polymer chain breakdown and microbial decomposition of organic compounds. This study aims, for the first time, to investigate the biogeochemical mechanisms involved in ocean acidification triggered by plastic pollution, as well as the role of plastic degradation as a modifier of the seawater carbonate system. We also propose to assess the individual and combined effects of plastic pollution and acidification on coral growth. Laboratory experiments were conducted using plastic particles (2–10 mm) collected from beach sand and incubated in seawater for 14 days under different light conditions (irradiated and dark). The experiment was developed in two phases: (1) abiotic, using sterilized seawater to test the physicochemical effects of plastic degradation; and (2) biotic, in which non-sterilized seawater was inoculated to evaluate the role of microbial decomposition as a potential driver of plastic-induced acidification. Temporal variations in pH, dissolved CO₂ concentrations, and aragonite saturation state (the CaCO₃ form used in coral calcification) were used as proxies to trace plastic as a new pathway for ocean acidification. Plastic significantly increased seawater CO₂ concentrations, rising from 13.03 µmol/kg (SD ± 7.88) on day 0 to 35.01 µmol/kg (SD ± 21.03) by day 14 under irradiated conditions, and from 11.97 µmol/kg (SD ± 7.80) to 24.67 µmol/kg (SD ± 17.10) under dark conditions. pH showed a negative logarithmic relationship with CO₂ concentrations. Consequently, the largest pH decrease occurred in the irradiated treatment, with a mean drop of 0.378 units in just seven days, reaching a minimum of 7.291—comparable to levels projected for the end of the century considering only atmospheric CO₂ emissions. Even under dark conditions, plastic caused pH reductions, with a mean decrease of 0.168 in seven days and a minimum value of 7.610. Aragonite saturation state decreased exponentially with declining pH, from 4.28 units (SD ± 2.06) at the start to 2.037 units (SD ± 0.76) at the end of the experiment. Similarly, the greatest reductions in aragonite occurred in the irradiated plastic treatment, reaching a minimum value of 1.018. These results highlight radiation as a key driver of plastic degradation, breaking polymer chains and accelerating CO₂ leaching into the marine environment. No significant changes were detected in the measured variables during the biotic phase, which may be due to the low concentration of dissolved organic carbon released by the plastic. In the next stage, laboratory experiments will manipulate CO₂ levels in conditions with and without plastic, assessing their individual and combined effects on coral calcification using incubation techniques. Based on previous findings of reduced carbonate levels and aragonite saturation, we expect a decrease in coral calcification rates, especially when plastic and acidification stressors act together. This study contributes to understanding the individual and combined impacts of global stressors on corals and to assessing their potential implications for the functioning of reef ecosystems. Such understanding is essential for developing effective conservation strategies in the face of rapidly changing environmental conditions.

COMMITTEE MEMBERS:
Presidente - 3257898 - Cybelle Menolli Longhini
Interno - ***.178.178-** - EDSON APARECIDO VIEIRA FILHO - UESC-BA
Externa à Instituição - LETICIA COTRIM DA CUNHA - UERJ