A GEE Toolkit for water quality monitoring from 2002-2022 in support of SDG 14 and coral health in Marine Protected Areas in Belize

Coral reefs are highly diverse ecosystems that provide many goods and ecosystem services globally. Coral reef ecosystems are also threatened by environmental stressors from anthropogenic sources and shifting climates. The United Nations Sustainable Development Goal 14 (“Life Below Water”) addresses the need to conserve and sustainably use the ocean, seas, and marine ecosystems, including reef systems. Belize’s coral reef system is the second largest in the world, providing sources of income to Belizeans through tourism and fisheries as well as coastline protection. In order to conserve their marine ecosystems, Belize has a network of Marine Protected Areas (MPAs) throughout their coastal waters. Using Aqua MODIS satellite imagery from 2002-2022, Google Earth Engine, and RStudio, we present a workflow to calculate stress days on MPAs and a coral vulnerability index based on sea surface temperature (SST) and Kd(490), a proxy of water clarity. The Corozal Bay, Swallow Caye, Port Honduras, and South Water Caye MPAs had the highest percentages of stress days and coral vulnerability stress index score based on these two parameters among the 24 MPAs analyzed. Additionally, SST in the warmest month of the year in Belize were seen to increase across all MPAs from 2002-2022 (p < 0.01). This GEE toolkit provides a straightforward and accessible tool to help governments monitor both water quality and risks to coral reefs in accordance with SDG 14.

珊瑚礁是高度多样化的生态系统，在全球范围内提供多种物产与生态系统服务。同时，珊瑚礁生态系统正面临人为来源的环境压力与气候变化带来的威胁。联合国可持续发展目标14（"水下生命"）旨在推动对海洋、海域及包括珊瑚礁系统在内的海洋生态系统进行保护与可持续利用。伯利兹珊瑚礁系统是全球第二大珊瑚礁系统，其通过旅游业、渔业为伯利兹民众提供收入来源，同时兼具海岸线防护功能。为保护本国海洋生态系统，伯利兹在沿海水域布设了海洋保护区（Marine Protected Areas, MPAs）网络。本研究利用2002至2022年的Aqua MODIS卫星影像、Google Earth Engine与RStudio，构建了一套用于计算海洋保护区受胁迫天数的工作流程，并基于海面温度（Sea Surface Temperature, SST）与表征水体透明度的替代指标Kd(490)开发了珊瑚脆弱性指数。在本次分析的24个海洋保护区中，科罗萨尔湾（Corozal Bay）、燕子礁（Swallow Caye）、洪都拉斯港（Port Honduras）与南水礁（South Water Caye）的受胁迫天数占比，以及基于这两项参数的珊瑚脆弱性胁迫指数得分均为最高。此外，2002至2022年间，伯利兹所有海洋保护区内年度最热月份的海面温度（SST）均呈现显著上升趋势（p < 0.01）。本GEE工具包提供了一款简便易用的工具，可协助各国政府依据可持续发展目标14（SDG 14）对水质及珊瑚礁面临的风险开展监测。