Tidal freshwater wetlands provide valuable ecosystem services such as nutrient cycling, coastal flood control, and reproductive habitat for early life stages of economically and ecologically important fishes. The nutrient rich environments that tidal freshwater wetlands occur in support high levels of primary productivity of phytoplankton and vegetation that provide essential reproductive habitat for anadromous clupeid fishes (Alosa spp., Brevoortia tyrannus) in Chesapeake Bay tributaries. Seasonal retention of clupeid eggs and larvae within tidal freshwater habitats may enhance early growth, survival, and year class strength. The primary goal of the present study was to characterize the relative importance of tidal freshwater wetlands to the early life history stages of anadromous, migratory, and resident clupeid fishes in the lower James River. From 2014-2018, conical tow nets were used to collect ichthyoplankton samples from representative locations within the tidal freshwater marsh-creek complex of Curles Neck Creek, Virginia during the period of February through May. Boat electrofishing was used to sample juvenile target clupeids within the marsh-creek complex during March through November 2014-2018. A strong positive correlation between larval and juvenile Blueback Herring and Atlantic Menhaden, supported the hypothesis of seasonal in-system retention. This was the first published study to describe spatial and temporal patterns of occurrence of clupeid fishes with varying life history strategies in a tidal freshwater marsh and highlighted the importance of tidal freshwater marshes as nursery habitat.

Tidal freshwater wetlands (TFW) are at significant risk of loss or alteration due to global climate change, and saltwater intrusion from sea level rise is of particular concern for these habitats due to their proximity to coastal areas. A space-for-time model was used to investigate the effects of saltwater intrusion on soil methanogen communities along naturally occurring salinity gradients on the Waccamaw, James, and Hudson Rivers. Amplification of the methyl coenzyme-M reductase (mcrA) functional gene was used in qPCR, reverse transcription qPCR, and T-RFLP to measure the abundance, activity, and community composition of soil methanogens. Both the abundance and activity of methanogens decreased with increasing salinity, and the both total and active methanogen community composition shifted in response to changes in salinity. This research demonstrates that saltwater intrusion will alter carbon cycling in TFWs, potentially altering their ability to sequester carbon and keep pace with rising sea level.