Archives: Publications

Motor skills learned implicitly should be less susceptible to deterioration under psychological pressure (i.e., choking) than skills learned more explicitly. In this systematic review and meta-analysis, we investigated that prediction. A systematic search was conducted for articles that had participants learn a motor skill implicitly relative to a comparison group and had both groups perform the skill under low- and high-pressure conditions. Ten studies with a median of nine participants/group met inclusion criteria. Seven of ten studies reported an advantage of learning a motor skill implicitly when performing under psychological pressure. Moreover, a multivariate random-effects metaanalysis revealed that participants who learned a motor skill implicitly performed better under a high-pressure condition than a low-pressure condition, Hedges’ gav = −1.17, 95% lower CI [−1.61], upper CI [−0.74], whereas participants in the comparison group performed similarly between conditions, Hedges’ gav = 0.19, 95% lower CI [ −0.33], upper CI [ 0.71]. For the implicit learning group, a funnel plot of the relationship between effect size and standard error showed an asymmetrical distribution and a significant relationship, indicating bias. In conclusion, results confirm the prediction that implicit motor learning benefits performance under pressure. However, this effect might be distorted by bias and driven by underpowered studies, likely causing it to be overestimated. We suggest the advantage of learning a motor skill implicitly versus explicitly on performance under pressure be assumed to be moderately sized, pending future research, and encourage preregistered studies with larger sample sizes to estimate the effect more accurately.

This report describes a new screening tool to examine lake and reservoir susceptibility to eutrophication in selected watersheds of the eastern and southeastern United States using estimated nutrient loading and flushing rates with measures of waterbody morphometry. To that end, the report documents the compiled data and methods (R-script) used to categorize waterbodies by Carlson’s Trophic State Index. Assessments were completed for 232 lakes and reservoirs having a surface area greater than or equal to 0.1 square kilometer in watersheds that drain to the Atlantic and eastern Gulf of Mexico coasts of the United States and in watersheds within the Tennessee River Basin. Waterbodies were categorized by type—natural lakes, headwater reservoirs, and downstream reservoirs—and were assessed independently. Recursive partitioning and the model-based boosting routine were used to create four-node regression trees to group waterbodies into five endpoints from low-to-high measures of Secchi depth, and concentrations of chlorophyll a and microcystin according to shared nutrient loading, flushing rate, and morphometric characteristics. Trophic state designations were assigned based on the average value within each of the five endpoints. An application (procedure) is provided using the tool to examine the susceptibility of a given waterbody of interest to eutrophication. Results of this study can aid water-resource managers in prioritizing lake and reservoir protection and restoration efforts based on the susceptibility of these waterbodies to eutrophication relative to nutrient loading, flushing rate, and morphometric characteristics.

Blue-green algae, also known as cyanobacteria, are microscopic organisms frequently found in aquaculture ponds in the southeastern United States.

Although blue-green algae are common in freshwater systems, blooms (dense accumulations of these organisms) can lead to serious issues for catfish farmers. Some, but not all, blue-green algae can produce compounds that are toxic to catfish or may lead to unwanted taste and odors in fish fillets. Bloom formations may also create low oxygen conditions at night or as cells decay following a crash in a bloom. Of the blue-green algal species in the southeast, Microcystis is among the most common and often leads to problems for catfish farmers.

Microcystis blooms often form distinctive Kelly green scums at the water surface (figure 1). Many other kinds of blue-green algae, other kinds of algae, and aquatic plants (such as duckweed or watermeal) form surface blooms or mats during certain times of the year that are army green or various other shades (figures 2a and 2b). So, more formal identification of the algae is needed. Microcystis can be identified using a microscope and is typically distinguishable as groups of small, circular cells (colonies) within a jelly-like mass (figures 3a and b). Your county Extension agent can assist in identification, if needed.