Gurung, D.P.; Chen, N.; Waguespack, Y.; Ishaque, A.B., and Chigbu, P., 2024. Assessment of alkaline phosphatase activity in the water column of Maryland Coastal Bays. Journal of Coastal Research, 40(2), 319–337. Charlotte (North Carolina), ISSN 0749-0208.

Understanding maximum alkaline phosphatase activity (V_max) is essential to understand the phosphorus (P) cycle in Maryland Coastal Bays (MCBs). The objectives of this study were to measure V_max in the samples collected from different locations in MCBs and to examine the relationship between V_max and dissolved reactive phosphorus (DRP) concentrations. Water samples were collected at 13 sites from 2014 to 2016, and V_max was measured in whole water by using 4-methylumbelliferyl phosphate as the fluorogenic substrate. Although the measured V_max was affected by multiple factors, P limitation events were recognized from spatial/temporal distributions in V_max values, which might not be reflected by DRP condition. Regression analysis did not yield a significant relationship between DRP and V_max, and monthly averages of DRP and V_max provide better evidence of the connection between DRP and V_max, including P limitation (high V_max) and alkaline phosphatase inhibition (low V_max). Results from this study support the view that V_max is a good indicator of availability of DRP in aquatic environments. More work is needed to further understand the relationship between V_max and DRP, in particular, when strong P limitation occurs in the Bays. Moderate to strong positive relationships were observed between V_max and chlorophyll a. Moderately negative relationships were observed between V_max and salinity and between V_max and pH, which may be attributed to freshwater inputs. Likewise, a moderate positive relationship was observed between V_max and temperature for only some months.