Diversity, seasonal abundance, and environmental drivers of chaetognath populations in North Inlet Estuary, South Carolina, USA

Chaetognaths (Phylum: Chaetognatha) are one of the most abundant phyla of
zooplankton worldwide and play an important role in marine trophic
interactions. Although the role of chaetognaths in global ecosystems is
well understood, the spatial variation and environmental drivers of
estuarine chaetognath populations is poorly understood. To provide the
first known record of chaetognath species composition in a coastal estuary
in the south-eastern USA, chaetognaths were identified and quantified from
zooplankton samples collected on a monthly basis in 2019 and 2020 from
North Inlet Estuary in South Carolina. Parasagitta tenuis was the most
abundant species of the five found, making up 33% of total abundance. The
egg presence of these chaetognaths was further analyzed to gauge
reproductive cycles. Abundance and egg presence were compared with surface
and bottom measurements of temperature, salinity, and dissolved oxygen
levels to determine the driving abiotic factors behind chaetognath’s
seasonal variability and reproductive cycles. Temperature, salinity, and
dissolved oxygen all had low (r < ± 0.29), non-significant
correlations with abundance. Chaetognath egg production was most
significantly associated with dissolved oxygen (p < 0.001) and
seasonal changes in temperature (p < 0.001). Our initial findings
indicate the continued abundance of chaetognath in a local estuary is
dependent on abiotic factors that are strongly influenced by a changing
climate.