Marine communities on oil platforms in Gabon, West Africa: high biodiversity oases in a low biodiversity environment

The marine biodiversity of Gabon, West Africa has not been well studied and is largely unknown. Our examination of marine communities associated with oil platforms in Gabon is the first scientific investigation of these structures and highlights the unique ecosystems associated with them. A number of species previously unknown to Gabonese waters were recorded during our surveys on these platforms. Clear distinctions in benthic communities were observed between older, larger platforms in the north and newer platforms to the south or closer to shore. The former were dominated by a solitary cup coral, Tubastraea sp., whereas the latter were dominated by the barnacle Megabalanus tintinnabulum, but with more diverse benthic assemblages compared to the northerly platforms. Previous work documented the presence of limited zooxanthellated scleractinian corals on natural rocky substrate in Gabon but none were recorded on platforms. Total estimated fish biomass on these platforms exceeded one ton at some locations and was dominated by barracuda (Sphyraena spp.), jacks (Carangids), and rainbow runner (Elagatis bipinnulata). Thirty-four percent of fish species observed on these platforms are new records for Gabon and 6% are new to tropical West Africa. Fish assemblages closely associated with platforms had distinct amphi-Atlantic affinities and platforms likely extend the distribution of these species into coastal West Africa. At least one potential invasive species, the snowflake coral (Carijoa riisei), was observed on the platforms. Oil platforms may act as stepping stones, increasing regional biodiversity and production but they may also be vectors for invasive species. Gabon is a world leader in terrestrial conservation with a network of protected areas covering >10% of the country. Oil exploration and biodiversity conservation currently co-exist in terrestrial and freshwater ecosystems in Gabon. Efforts to increase marine protection in Gabon may benefit by including oil platforms in the marine protected area design process.

西非加蓬的海洋生物多样性尚未得到系统研究，相关认知整体较为匮乏。本研究针对加蓬近海石油平台相关的海洋群落展开调查，这是全球首次针对此类海洋设施的科学探究，同时揭示了其关联的独特生态系统。本次平台调查期间，我们记录到多种此前未在加蓬海域被报道的物种。研究观察到，北部老旧大型平台与南部或近岸新建平台的底栖生物群落（benthic communities）存在显著差异：前者以单体杯状珊瑚——树孔珊瑚属（Tubastraea sp.）为优势类群，后者则以钟形巨藤壶（Megabalanus tintinnabulum）为优势类群，且相较于北部平台，其底栖组合（benthic assemblages）的物种多样性更为丰富。既往研究显示，加蓬自然岩质基底上仅存在少量具虫黄藻的石珊瑚（zooxanthellated scleractinian corals），但本次调查未在石油平台上记录到此类珊瑚。部分平台区域的鱼类总生物量估算值超过1吨，优势类群包括金梭鱼属（Sphyraena spp.）、鲹科鱼类（Carangids）以及曳丝鲹（Elagatis bipinnulata）。本次调查中记录的鱼类物种里，34%为加蓬海域新记录种，6%为热带西非海域新记录种。与平台紧密关联的鱼类群落具有显著的跨大西洋分布亲缘性，石油平台或可推动此类物种的分布范围向西非近岸海域拓展。本次调查还在平台上发现至少一种潜在入侵物种——雪花珊瑚（Carijoa riisei）。石油平台可作为生物扩散的踏脚石，在提升区域生物多样性与生产力的同时，也可能成为入侵物种的传播媒介。加蓬在陆地保护领域处于全球领先地位，其保护地网络覆盖该国超过10%的陆地面积。目前，加蓬的陆地与淡水生态系统中，石油勘探与生物多样性保护实现了协同共存。若将石油平台纳入海洋保护区的规划设计环节，或将助力加蓬提升海洋保护工作的整体成效。