2.2.1 Water quality
During each sampling event, a grab sample is collected for FC analysis.
To enumerate FC, NCDMF uses a five-tube decimal dilution, method SM 9221
(NSSP, 2019). Data records also include monitoring type to indicate the
type of sampling (either conditional or routine), coded SGA designation
(i.e., names listed in Figure 1b), station name, date of the sample,
tide at the time of sample, salinity, and water temperature. The data
are publicly available through NCDMF, and have been reorganized into a
normal form database called “ShellBase”, which is freely available
through the Southeast Coastal Ocean Observing Regional Association’s
Data Portal (SECOORA, 2022).
In our study, the data were filtered to only include routine samples
from stations that had 20 years of continuous water quality sampling
data from 1999 to 2021. 466 stations met these conditions. We chose the
time period of 1999 to 2021 due to changes in management procedures in
the NCDMF in the 1990’s. Throughout the 1990’s, NCDMF progressively
introduced conditional management plans to many of the growing areas.
Therefore, by confining the dataset from 1999 to 2021, we are safely
ensuring that the conditional management plans have been introduced and
that the sampling would be reflective of that. Observations collected
through conditional sampling were not considered in the analysis because
the varied conditions under which conditional sampling occurs results in
skewed FC concentrations and is not as representative of the system as
the data collected through routine sampling design.