Environmental Risk from Land Use Changes in the Mangrove Ecosystem El Morro Island, North of Manabí – Ecuador
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Abstract
The El Morro Island Ecosystem, north of Manabí, Ecuador, is a tropical coastal ecosystem of high biological productivity, with mangroves and intertidal zones. This study evaluated the environmental risks associated with changes in land use and concentration of heavy metals in sediments, using a mixed approach that integrated multitemporal analysis, sediment analysis and community perception. WV02 (0.5 m) and Landsat 8 (30 × 30 m) satellite images were processed in QGIS 3.28, generating decadal maps (1985–2025) to identify trends in degradation, aquaculture expansion and their relationship with mangroves. 10 representative points of the mangroves were selected, considering proximity to sources of pollution and state of conservation. Surface sediments (0–100 cm) were analyzed by ICP-MS following EPA and ISO standards. Enrichment Factor (EF), Environmental Risk Code (ARC) and Geocumulative Pollution Index (Igeo) indices were calculated to evaluate anthropogenic influence and biological risk. The results show progressive loss of vegetation cover and expansion of shrimp farms: 30,102 ha deforested (1985–1995), an additional 10,719 ha (1995–2005) and 66,791 ha allocated to aquaculture activities. By 2025, the total vegetation was 22,204 ha. Cd and Hg were undetectable (<0.01 mg/kg) and Cr slightly exceeded the permissible limit at some points; the rest of the metals remained within safe ranges according to TEL, PEL, ERL and ERM. The EF indicated a predominance of natural processes (EF ≤ 1.99), except for Na with moderate enrichment (2 ≤ EF < 5). CRA and Igeo showed low mobility and no significant pollution.
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