Temporal and Environmental Factors Driving Vibrio Vulnificus and V. Parahaemolyticus Populations and Their Associations With Harmful Algal Blooms in South Carolina Detention Ponds and Receiving Tidal Creeks

Abstract

Incidences of harmful algal blooms (HABs) and Vibrio infections have increased over recent decades. Numerous studies have tried to identify environmental factors driving HABs and pathogenic Vibrio populations separately. Few have considered the two simultaneously, though emerging evidence suggests that algal blooms enhance Vibrio growth and survival. This study examined various physical, nutrient, and temporal factors associated with incidences of HABs, V. vulnificus, and V. parahaemolyticus in South Carolina coastal stormwater detention ponds, managed systems where HABs often proliferate, and their receiving tidal creek waters. Five blooms occurred during the study (2008-2009): two during relatively warmer months (an August 2008 cyanobacteria bloom and a November 2008 dinoflagellate bloom) followed by increases in both Vibrio species and V. parahaemolyticus, respectively, and three during cooler months (December 2008 through February 2009) caused by dinoflagellates and euglenophytes that were not associated with marked changes in Vibrio abundances. Vibrio concentrations were positively and significantly associated with temperature and dissolved organic matter, dinoflagellate blooms, negatively and significantly associated with suspended solids, but not significantly correlated with chlorophyll or nitrogen. While more research involving longer time series is needed to increase robustness, findings herein suggest that certain HAB species may augment Vibrio occurrences during warmer months.

Keywords: South Carolina; Vibrio; harmful algal blooms; phytoplankton; stormwater ponds.

Figure 1

Map depicting study location within South Carolina (SC) USA as (a) a regional overview of study area along the southeastern coast, highlighting Kiawah Island (star and insert), as well as the (b) K075 and (c) K001 systems, with sampling locations indicated (white circles) for both ponds and receiving tidal creeks.

Figure 2

Time series of Vibrio spp. concentrations (mean ln copies 100 mL⁻¹ ± SE) at the four study locations as (a) V. parahaemolyticus (V _p), and (b) V. vulnificus (V _v). Concentrations that were nondetect are set to the limit of detection (ln (11) = 2.4). Black circles denote K001, grey triangles denote K075, with filled and open symbols representing pond and creek data, respectively. Squares indicate dates when a HAB was noted in a field sample such that black denotes the K001 system, grey denotes the K075 system, and speckled denotes a HAB observed in both systems, connected through each system by the solid grey line. Causative bloom organisms were Cylindrospermopsis raciborskii (1 August 2008), Anabaena sp. (15 August 2008), Heterocapsa rotundata (24 November 2008), Karlodinium veneficum (26 January 2009), and Eutreptiella sp. (22 December 2008, 9 February 2009).

Figure 3

Time series of select water quality parameters at the four study locations used for this study. Metrics include (a) water temperature (T), (b) salinity, (c) dissolved organic carbon (DOC), and (d) total suspended solids (TSS). DOC and TSS values represent mean concentrations (n = 3 ± SD). Black circles denote K001, grey triangles denote K075, with filled and open symbols representing pond and creek data, respectively.