Spatial and temporal variation in benthic foraminiferal assemblages record history of human activities within the Matagorda Bay system

Abstract

The spatial variability of estuarine ecosystems poses challenges to ecosystem health assessment and makes remediation efforts costly and time-consuming. Benthic foraminiferal fossils preserved in estuarine sediments record past environmental conditions and can be used to assess spatial variability in ecosystem changes across an estuary through time. Here we use changes in the faunal composition and ecological structure of benthic foraminiferal faunas from 6 sediment cores from estuarine settings surrounding Matagorda Bay, Texas to assess the spatial variability of environmental changes over the last ∼400 years. Since ∼1950 CE, when human populations and industrial activity increased in the region, the richness and evenness of benthic foraminiferal assemblages decreased across the bay. The relative abundance of stress-tolerant taxa, such as Ammonia spp., also increased toward the present at all sites. However, the magnitude of change at each site varies and the specific changes in faunal composition reflect spatial differences in the intensity of environmental changes with sites close to protected areas changing less than sites close to point sources of pollution suggesting that benthic foraminifera can record local changes within a single estuary. However, benthic foraminiferal assemblages became more similar among sites after the intensification of human activities, suggesting increased stress is leading to faunal homogenization across the Matagorda Bay system.