Environmental monitoring program for Prymnesium parvum in Lake Texoma
Objective of program:
The objective of this proposed research is to gain understanding of the environmental conditions in Lake Texoma that are conducive to, and prevalent during, Prymnesium parvum blooms.   Specifically, we would monitor the lake at selected sites for basic physical, chemical, and biological parameters to allow a better understanding of environmental conditions prevalent in the lake when P. parvum is blooming, but also when P. parvum is absent.

Problem and need:
The toxic golden algae, Prymnesium parvum , first appeared in Lake Texoma during the winter of 2004 (January – March), causing substantial fish kills in several embayments, such as Lebanon Pool and the mouth of Big Mineral Creek.   We know little regarding factors affecting susceptibility to P. parvum toxins of the various sport and recreational fishes in Lake Texoma, nor of the ecological role that P. parvum may play at the base of the Lake Texoma food web as both food for and competitors with herbivorous zooplankton, the primary food base for all YOY fish in the lake, as well as for most forage species, such as threadfin shad.   Current ODWC-funded research at UOBS is addressing these factors using EPA-approved toxicity experiments (LC 50 assays) and laboratory feeding experiments with dominant Lake Texoma zooplankton.

Although the 2004, 2006, and 2007 blooms of P. parvum was limited to a few areas around the lake, primarily Lebanon Pool, experience from lakes in Texas (Watson 2001), where P. parvum has existed since 1985, indicate that such blooms could become a common feature of Lake Texoma and that the blooms could even intensify in their effects on the ecosystem.   Future blooms of P. parvum could potentially wreak havoc, both ecologically and economically, on the Lake Texoma fishery.   Our present laboratory-based research will provide basic toxicological and ecological knowledge of this invading species that will enhance the capabilities of lake managers in their efforts to predict and possibly control these harmful blooms.   However, without a solid and continual monitoring program on the lake itself, we lack information on specific environmental conditions that are conducive to, or possibly even deleterious to, a P. parvum bloom.   Knowledge of these specific environmental conditions that are either favorable or deleterious to P. parvum will be crucial in future efforts to regulate P. parvum blooms in Lake Texoma and other freshwater lakes and reservoirs in Oklahoma.

Research:
Our monitoring program aims to identify physical, chemical, and biological environmental conditions in the lake that may be conducive to or deleterious to P. parvum bloom development, as well as to toxicity of P. parvum during a bloom.   Published literature and experienced gained in Texas by the Texas Parks and Wildlife Department and various collaborating institutions suggests that P. parvum blooms seem to be favored under conditions of relatively high salinities (Watson 2001, J. Glass, TPWD pers. comm. ). Blooms tend to be more common in cooler periods (winter and spring), but P. parvum has also bloomed during summer in some Oklahoma and Texas lakes. Little is known regarding biological interactions such as competition from native phytoplankton and predation (i.e, grazing) by herbivorous and omnivorous zooplankton.

Regarding toxicity of P. parvum , research suggests that toxicity of the primary P. parvum toxins (prymnesins) may be higher at low nutrient (nitrogen and phosphorus) concentrations (Johansson and Graneli 1999).   We here hypothesize that the nutrient-dependent toxicity is related to the stoichiometry of nutrient availability.   Prymnesins are long-chain carbon (C) molecules with only one nitrogen (N) molecule and no phosphorus (P). Based on biological stoichiometry theory (Sterner and Elser 2002), C-based toxins should only be produced when C is in sufficient supply relative to the other major nutrients (N&P).   Hence at either N-limiting or P-limiting conditions (i.e., when, by definition, C would be in sufficient supply relative to N and P) toxin production would not be expected to be costly. Therefore, toxin production aimed at killing competing algal species, thereby making the nutrients in those algae available to P. parvum , would be beneficial to P. parvum . In contrast, when N and P are in sufficient supply (i.e., available at ratios near 16:1, when, by definition, C would expected to be the major limiting nutrient), toxin production would be extremely costly and subsequent increased availability of N and P (through death of competing algae) would not be beneficial to P. parvum (because N and P are already in sufficient supply). Therefore, we would predict prymnesin production during P. parvum blooms only if N or P are in limiting supplies (i.e., when N or P concentrations in the lake are at low relative concentrations; at N:P ratios substantially higher or lower than 16:1).

In Lake Texoma, since the advent of P. parvum blooms is relatively recent, we have little information regarding environmental conditions in the lake that favor or deter P. parvum bloom development. As such, we have begun a lake-wide monitoring program in Lake Texoma to establish baseline environmental conditions in the lake that may or may not be conducive to P. parvum bloom development.   Physical and chemical parameters of interest include temperature, mixing depth, light availability, salinity, and nitrogen and phosphorus concentrations.   Biological parameters of interest include potential competitors (other phytoplankton) and grazers (zooplankton) of P. parvum .   All environmental parameters are monitored at selected sites around Lake Texoma at weekly (Dec-Mar) or bi-weekly (Apr-Nov) intervals. This monitoring program is complementary of an on-going laboratory study of P. parvum and thereby increase our understanding of factors conducive to P. parvum blooms, not only in Lake Texoma, but in other Oklahoma freshwater systems. [back]