Water quality associations and spatiotemporal distribution of the harmful alga Prymnesium parvum in an impounded urban stream system

Abstract

The Jim Bertram Lake System consists of several stream impoundments within the City of Lubbock, Texas (USA). Baseflow in the upstream reach is dominated by nitrogen-rich-treated wastewater. While toxic blooms of Prymnesium parvum have occurred in this system for ∼2 decades during fall or winter-spring, little is known about water quality variables that facilitate blooms or the alga’s spatiotemporal distribution. Water quality associations were examined monthly over a 1-year period. Total phosphorus was largely below the detection limit, suggesting that the system is phosphorus limited. Algal abundance was low during the assessment period and associations were determined using multiple logistic regression. Algal incidence was negatively associated with temperature and positively with organic nitrogen and calcium hardness. These findings conform with earlier reports but positive associations with the latter two variables are noteworthy because they have not been widely confirmed. Spatiotemporal distribution was evaluated in fall and winter-spring of three consecutive years. Prymnesium parvum incidence was higher in the upper than in the lower reach, and detections in the lower reach occurred only after a dense bloom developed in the upper reach contemporaneously with stormwater runoff-associated flooding. Thus, the upstream reach is a major source of propagules for downstream sites. Because urban runoff is a source of phosphorus and its nitrogen: phosphorus ratio is lower than prevailing ratios in the upper reach, what triggered the bloom was likely relief from phosphorus limitation. This study provided water quality, geographic and hydrological indices that may inform prevention and control methods for harmful algae in nitrogen-enriched urban systems.

Toxic Algae in Inland Waters of the Conterminous United States—A Review and Synthesis

“…High-and low-toxicity strains of P. parvum can coexist in time and space [86], further complicating our understanding of the association between cell density and toxicity. Indeed, although they seem to be relatively uncommon, high-density blooms with no overt signs of ichthyotoxicity (e.g., dead or dying fish) have been reported in the USA [85,87,88] and in England [89]. The true frequency of non-toxic blooms is unknown because they can go unnoticed and unreported.…”

“…Toxic blooms of P. parvum in U.S. inland waters largely occur during the cooler months of the year, with peak bloom conditions often coinciding with temperatures in the range of 8 to 15 • C [36,85,87,88,94,135] Although rare, there are a few instances of toxic blooms occurring in the summer. For example, a highly toxic bloom was recorded in Moss Creek Lake, Texas, at a temperature of ~29 • C in the summer [135].…”

“…In the Pecos River, the spatiotemporal presence of P. parvum was positively associated with total organic phosphorus, and the spatiotemporal abundance was positively associated with total organic nitrogen [95]. In an impounded urban stream system in the upper reaches of the Brazos River (Texas), the spatiotemporal presence of P. parvum was positively associated with the total organic nitrogen [88]. These observations are generally consistent with a scenario where elevated concentrations of organic nutrients may favor the growth of P. parvum, a mixotrophic species.…”

“…The timing of P. parvum's growth in U.S. inland waters is not what would be expected if light (increased daylength and light intensity) were its primary driver. With rare exceptions, toxic blooms of P. parvum typically occur during the cooler months of the year (<15 • C), either in the fall or spring [88] or from the fall to the spring (Figure 7). The growth period of this species thus has been described as beginning in the fall and ending in the spring, with variability in population density and toxicity (including the absence of blooms) along this timeline being a function of other environmental variables [88].…”

“…With rare exceptions, toxic blooms of P. parvum typically occur during the cooler months of the year (<15 • C), either in the fall or spring [88] or from the fall to the spring (Figure 7). The growth period of this species thus has been described as beginning in the fall and ending in the spring, with variability in population density and toxicity (including the absence of blooms) along this timeline being a function of other environmental variables [88]. In view of this information, temperature seems to be more important than light as driver of P. parvum's growth period in U.S. inland waters.…”