Tracking the settlement patterns of marine biofouling communities

Abstract

ften focus on surveying after a specific period of settlement, with few regions being able to implement ongoing monitoring systems. Whilst these programs are beneficial, they provide only a snapshot in time and may miss key information about the temporal settlement patterns of alien fouling species and the associated management implications. The current study initiated a temporal settlement study that could 1) track the settlement patterns of fouling species with a focus on detecting alien species and 2) highlight the change in community structure across different months, providing an insight into the ecological succession. The study was conducted in a marina in Cape Town, South Africa, using PVC settlement plates, and serves as a baseline for a longer term monitoring settlement study. The findings indicate that the species richness and abundance differed significantly across the months (Wald test: p < 0.001), with a rapid increase in both measures within a month and a gradual decline in species richness after two to three months. A total of 12 alien species were detected accounting for 55% of the community structure. Within the first month, eight of those species had already settled. Overall, four species (Corella eumyota, Diplosoma listerianum, Neodexiospira brasiliensis and Balanus trigonus) were particularly dominant throughout the study. The ascidian, Corella eumyota currently listed as native, was one of the first species to settle and demonstrated strong competitive traits, raising concerns about its current status in the region. The findings highlight the value of temporal settlement studies revealing patterns that may have been overlooked when sampling at only one point in time. Thus, a longer-term monitoring program that tracks the temporal settlement patterns of alien fouling species could start to provide valuable insights to management authorities