Floodplains are some of the most productive and diverse ecosystems on Earth. The Usumacinta River Basin, in the Southern Gulf of Mexico, hosts several floodplain lakes, whose integrity is threatened by water resource development. We aimed to investigate how food webs in these ecosystems vary in relation to their hydrological connectivity and seasonal flood cycles. To do this, we combined analysis of water quality and stable isotopes in two lakes with permanent connection to the Usumacinta River and two isolated lakes during dry, early rainy and late rainy season. Significant differences in chlorophyll-a, nutrients and suspended solids were reflected in distinct trophic dynamics among lakes. Stable isotope analysis revealed that fish from all lakes relied predominantly on autochthonous primary production, but while phytoplankton was the dominant resource for fish in the isolated lakes, aquatic macrophytes made the highest contribution to consumers’ production in the connected lakes. Fish tended to have broader isotopic niches during the early rainy season, likely reflecting consumption of a wider range of resources following the first flow pulses of the year. Our study highlights the importance of hydrological connectivity and natural flow regimes to maintain the outstanding biodiversity and fishery yield of these floodplain ecosystems.

洪泛区是地球上生产力最高，种类最多的一些生态系统。墨西哥南部海湾的乌苏马辛塔河流域拥有几个洪泛区湖泊，其完整性受到水资源开发的威胁。我们旨在调查这些生态系统中的食物网在水文连通性和季节性洪水周期方面如何变化。为此，我们结合了两个湖泊的水质和稳定同位素分析，这些湖泊在干旱，早雨和雨季后期与乌苏马辛塔河和两个孤立的湖泊保持永久连接。湖泊之间营养特性的不同反映了叶绿素a，养分和悬浮固体的显着差异。稳定的同位素分析表明，所有湖泊的鱼类主要依赖于土生土长的初级产品，但是，尽管浮游植物是偏僻湖泊中鱼类的主要资源，但水生植物在相连湖泊中对消费者生产的贡献最大。在雨季初期，鱼类往往具有较宽的同位素壁ni，这可能反映了在一年的第一波水流之后对更广泛资源的消耗。我们的研究强调了水文连通性和自然流量机制对于维持这些洪泛区生态系统杰出的生物多样性和渔业产量的重要性。