We conducted a monthly field study from January to December 2021 to characterize the benthic invertebrate community dynamics of three tidal wetlands experiencing Phragmites australis invasion in Suisun Marsh, located in the San Francisco Bay-San Joaquin Delta region of California. We sought to understand whether benthic invertebrate community composition (species richness, diversity) was impacted by the invasive plant canopy. The surveyed wetlands were Tule Red (38.128880, -121.980554), Hill Slough (38.232834, -122.020285), and Blacklock (38.183957, -121.889321). At Tule Red and Hill Slough, semi-permanent transects (n=19) were distributed in a paired design with Phragmites-invaded and native canopy areas along secondary and tertiary tidal channels within the wetlands, positioned perpendicular to the water channel. Transects were 20m in length with benthic invertebrates collected every five meters in a 1m2 quadrat, except at the 15m mark. At Blacklock, we established general plot areas, at which three quadrat measurements were taken instead of sampling along the transect. This was done because of high inundation of the site and an ongoing herbicide study by the California Department of Water Resources, which we incorporated into our dataset. Benthic mud cores (14.5cm deep and 6cm in diameter) were collected using a PVC pipe and stored into a plastic Ziploc bag. All invertebrate samples were transported to the UC Davis Center for Aquaculture and Aquatic Biology within two hours of collection in coolers. Benthic samples were weighed, rinsed with deionized water to remove sediment, and filtered using a 0.5mm sieve. Retained invertebrates and vegetation were preserved in a rose bengal-dyed 70% ethanol solution. Invertebrates were identified to morphospecies level. Benthic samples were quantified and identified on a quarterly basis for the dataset (January, March, June, September, December 2021). Invertebrate sample processing, identification, and quantification followed a standardized US Geological Survey protocol with a quality assurance/quality control (QA/QC) step. This step determined that 50% of each benthic invertebrate collection was a sufficient representative sample, which was determined using a portioned tray and a random number generator to select sample material for processing.
Species counts are total number of species group in the sample, counted in 50% of the total sample; samples were collected as vegetation in 8oz deli container and observed under dissecting microscope.
