Assessment of the Structure and Function of Macrobenthic Communities Affected by Port Activities

Abstract

Ports are vital for international trade and economic growth, but they also have a significant impact on the environment. The Port of Mar del Plata, located in the southwestern Atlantic coast, Argentina, is subject to challenges, including maritime traffic, human disturbances, storm water discharges, and coastal drift. Nevertheless, since 2016, projects have been initiated with the objective of improving storm water drainage in the surrounding area. This study assesses the macrobenthic community of the port using both taxonomic and functional approaches and comparing data from 2001 and 2021. The results demonstrate a 25% increase in species abundance during this interval. However, this increase was accompanied by a 42.7% decline in diversity and a 50% reduction in evenness. Changes in diversity of species composition were observed between both sampling years, with opportunistic and tolerant species, such as Nematoda and Capitella sp., representing the majority in 2001. By contrast, the 2021 data set showed a greater abundance in Nematode, as well as Neanthes sp., Jassa marmorata, and Polydora sp. Functional diversity analyses revealed significant spatial and temporal changes in the community, with an increase in functional groups and greater niche specialization in 2021. This was driven by the adaptation of certain functional traits to environmental stress. Low-energy areas favored high concentrations of organic matter in fine sediments that support deposit-feeding and burrowing organisms. The data indicate that medium and large-sized individuals dominate the breakwaters areas, suggesting that these structures provide refuges for the benthic community. Furthermore, an increase in species mobility was observed near the outlet of the Del Barco Creek in 2021, associated to sediment composition and currents generated by water discharges. Despite these findings, the AMBI index classified these sites as moderately disturbed. The study provides valuable insights for environmental port management, highlighting the urgent need for strategies to ensure ecosystem recovery and sustainability while underscoring the importance of long-term monitoring to detect ecological shifts and efforts to mitigate human impacts in ports.