Environmental DNA Reveals Patterns of Biological Invasion in an Inland Sea

Abstract

Non-native species have the potential to cause ecological and economic harm to coastal and estuarine ecosystems. Understanding which habitat types are most vulnerable to biological invasions, where invasions originate, and the vectors by which they arrive can help direct limited resources to prevent or mitigate ecological and socio-economic harm. Information about the occurrence of non-native species can help guide interventions at all stages of invasion, from first introduction, to naturalization and invasion. However, monitoring at relevant scales requires considerable investment of time, resources, and taxonomic expertise. Environmental DNA (eDNA) metabarcoding methods sample coastal ecosystems at broad spatial and temporal scales to augment established monitoring methods. We use COI mtDNA eDNA sampling to survey a diverse assemblage of species across distinct habitats in the Salish Sea in Washington State, USA, and classify each as non-native, native, or indeterminate in origin. The non-native species detected include both well-documented invaders and species not previously reported within the Salish Sea. We find a non-native assemblage dominated by shellfish and algae with native ranges in the temperate western Pacific, and find more-retentive estuarine habitats to be invaded at far higher levels than better-flushed rocky shores. Furthermore, we find an increase in invasion level with higher water temperatures in spring and summer across habitat types. This analysis contributes to a growing understanding of the biotic and abiotic factors that influence invasion level, and underscores the utility of eDNA surveys to monitor biological invasions and to better understand the factors that drive these invasions.

Invasive European green crab (Carcinus maenas) predation revealed with quantitative DNA metabarcoding

“…From this processed taxonomic dataset, we used a process modified from Duprey et al (2023) to manually categorize each taxon as a (1) native taxon, (2) previously detected non-native taxon, or (3) previously undetected non-native taxon. If the Washington coast was included within the taxon’s indigenous distribution in one or more of the World Register of Marine Species (WORMS), the Biodiversity of the Central Coast database, the National Estuarine and Marine Exotic Species Information System (NEMESIS), the Encyclopedia of the Puget Sound, or a peer-reviewed primary source, the taxon was considered native.…”

Invasive European green crab (Carcinus maenas) predation in a Washington State estuary revealed with DNA metabarcoding

“…From this processed taxonomic dataset, we modified methods from Duprey et al [46] to manually categorize each taxon as a (1) native taxon, (2) previously detected non-native taxon, or (3) previously undetected non-native taxon. This classification was performed using multiple databases, including: the World Register of Marine Species (WoRMS; [47]), the Biodiversity of the Central Coast database ( [48]), the National Estuarine and Marine Exotic Species Information System (NEMESIS; [49]), the Encyclopedia of the Puget Sound [50], and the peer-reviewed literature.…”