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Buley, R. P., A. Kelly, L. Roy, E. G. Fernandez-Figueroa, M. Gladfelter, A. Belfiore, and A. E. Wilson. 2021. Controlling Microcystis blooms in Alabama catfish aquaculture. Alabama Cooperative Extension Fact Sheet ANR-2757.  5pp.

Abstract

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.

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Clark, A., B. Howell, A. E. Wilson, and T. Schwartz. 2021. Draft genomes for one Microcystis-resistant and one Microcystis-sensitive strain of the water flea, Daphnia pulicaria. G3 11(11):jkab266

Abstract

Daphnia species are well-suited for studying local adaptation and evolutionary responses to stress(ors) including those caused by algal blooms. Algal blooms, characterized by an overgrowth (bloom) of cyanobacteria, are detrimental to the health of aquatic and terrestrial members of freshwater ecosystems. Some strains of Daphnia pulicaria have demonstrated resistance to toxic algae and the ability to mitigate toxic algal blooms. Understanding the genetic mechanism associated with this toxin resistance requires adequate genomic resources. Using whole-genome sequence data mapped to the Daphnia pulex reference genome (PA42), we present reference-guided draft assemblies from one tolerant and one sensitive strain of D. pulicaria, Wintergreen-6 (WI-6), and Bassett-411 (BA-411), respectively. Assessment of the draft assemblies reveal low contamination levels, and high levels (95%) of genic content. Reference scaffolds had coverage breadths of 98.9–99.4%, and average depths of 33X and 29X for BA-411 and WI-6, respectively. Within, we discuss caveats and suggestions for improving these draft assemblies. These genomic resources are presented with a goal of contributing to the resources necessary to understand the genetic mechanisms and associations of toxic prey resistance observed in this species.

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Hyman, M., Q. Wang, A. E. Wilson, S. Adhikari, and B. T. Higgins. 2021. Production of Daphnia zooplankton on wastewater-grown algae for sustainable conversion of waste nutrients to fish feed. Journal of Cleaner Production 310:127501.

Abstract

This study investigates the upcycling of nutrients in anaerobic digestate via algal biomass to zooplankton which is a natural fish feed. There are no published studies, to the authors’ knowledge, on the viability of growing zooplankton on digestate-grown algae. Here, the viability of digestate-grown Chlorella sorokiniana as a feed for the large-bodied generalist zooplankter, Daphnia, was tested. It was found that Daphnia fed with digestate-grown C. sorokiniana led to 1.5- to 14-fold greater Daphnia population growth than Daphnia fed with Ankistrodesmus sp., an established feed. A sterol analysis of C. sorokiniana found 4–6 mg/g of the sterol, ergosterol, and nearly double the α-linolenic acid content of Ankistrodesmus. Sterols and α-linolenic acid are often-limiting nutrients in Daphnia diets. Other factors hypothesized to influence nutrient transfer from algae to Daphnia were also tested, including algal feed concentration, sterol supplementation, and the presence of digestate bacteria in the algal feed. The presence of bacteria and exogenous cholesterol had no significant impacts on Daphnia growth. The higher feed concentration (5 mg C/L) led to 3 times higher Daphnia growth than the low feed concentration (1.5 mg C/L) even though the latter concentration has frequently been used by other researchers. Finally, it was determined that the feed conversion ratio of algae to Daphnia fell in the range of 0.19–0.31 and that trophic transfer of carbon was 25–28% while that of nitrogen was 29–34% in this un-optimized system. These values compare favorably to livestock feed conversion efficiency but additional losses will occur when Daphnia are fed to fish. These results show that cultivation of Daphnia on digestate-grown algae is technically feasible.

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Fernandez-Figueroa, E. G., A. P. Belfiore, and A. E. Wilson. 2021. Drones for monitoring “blue-greens” in catfish aquaculture ponds. Fish Farming News 2021(1):16-17.

Abstract

Drones, unoccupied aerial vehicles, are commonly used in agriculture to determine the health of economically important crops, such as corn and wheat. Similar methods are currently being developed to measure the abundance of beneficial green algae and potentially toxic cyanobacteria, commonly called “blue-green algae”, in aquaculture ponds. While currently in the developmental stages, these methods could be instrumental in informing important management decisions. Blue-green algae thrive in aquaculture ponds throughout the southeastern US during much of the year, especially during the summer, due to the high nutrient inputs in the form of catfish feed. Blue-green algae blooms can lead to fish kills through the production of toxins (i.e., cyanotoxins) or when bacteria decompose dead organic matter leading to depleted dissolved oxygen levels. Off-flavor issues are also commonly associated with blue-green algae blooms, as some species produce compounds such as geosmin and 2-methylisoborneol (MIB) that affect the flavor and reduce the market value of catfish fillets. To mitigate the economic impacts associated with blue-green algae, aquaculture managers employ EPA-approved algaecides, such as copper sulfate, to reduce cyanobacterial abundance. While copper treatment is an effective tool for managing blue-green algae, it can also remove beneficial green algae and diatoms that make up the base of aquatic food webs, as well as other microbes, such as bacteria, that play a role in reducing ammonia and nitrite concentrations. Therefore, determining if blue-green algae concentrations are high enough to warrant chemical treatment is important for maintaining healthy pond ecosystems

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Chislock, M. F., B. K. Olsen, J.J. Choi, A. Abebe, T. L. Bleier, and A. E. Wilson. 2021. Contrasting patterns of 2-methylisoborneol (MIB) vs. geosmin across depth in a drinking water reservoir are mediated by cyanobacteria and actinobacteria. Environmental Science and Pollution Research 28:32005-32014.

Abstract

Taste and odor episodes caused by off-flavor secondary metabolites, such as 2-methylisoborneol (MIB) and geosmin, pose one of the greatest challenges for drinking water utilities around the world. The prevalence of these compounds is predicted to increase in the future as a function of nutrient enrichment and elevated temperatures of surface drinking water sources. We conducted a manipulative field experiment in a drinking water reservoir to elucidate patterns for two taste and odor compounds, MIB and geosmin, as well as two taxa known to produce these compounds, phytoplankton (more specifically, cyanobacteria) and actinobacteria, across different depths in response to nutrient enrichment with two common dissolved nitrogen forms, organic urea or inorganic nitrate. In general, we found that MIB levels increased by greater than 250% with nutrient enrichment mediated by increased phytoplankton biomass. However, the effect of the fertilization treatments on MIB decreased with depth with a 35% reduction at 7 m versus 1.5 m. In contrast, geosmin levels reached a maximum at the lowest measured depth (7 m), were unaffected by the fertilization treatments, and followed a similar pattern to the abundance of actinobacteria. Thus, our data suggest that the positive response of phytoplankton (e.g., cyanobacteria, such as Oscillatoria species) to the fertilization treatments is likely responsible for increased MIB, while geosmin concentrations may be a function of actinobacteria-mediated decomposition in the hypolimnion in our study system.

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Fernandez-Figueroa, E. G., R. P. Buley, M. U.G. Barros, M. F. Gladfelter, W. D. McClimans, and A. E. Wilson. 2021. Carlson’s trophic state index is a poor predictor of cyanobacterial dominance in drinking water reservoirs. AWWA Water Science 3(2):e1219.

Abstract

A 20-month survey of 71 surface drinking water utilities across 44 waterbodies was conducted to determine whether the commonly used Trophic State Index (TSI) is a reliable indicator of eutrophication in drinking water sources. Raw water quality results showed that cyanobacteria, cyanotoxins (i.e., microcystin), and taste and odor (T&O) compounds (i.e., 2-methylisoborneol and geosmin) were generally low in the utilities sampled. TSI values based on chlorophyll concentrations (TSI Chl-a) were closely related to phytoplankton, cyanotoxin, and T&O concentrations and indicated that most drinking water sources were mesotrophic or eutrophic. However, TSI values based on total phosphorus (TSI TP) indicated that the drinking water sources were eutrophic or hypereutrophic. These results suggest that TSI Chl-a is a better predictor of cyanobacteria and their compounds than TSI TP. Phytoplankton abundance decreased with depth; therefore, managers should consider switching to deeper intakes when TSI Chl-a values increase to reduce removal costs.

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Valle-Pombrol, A., A. Comas-Gonzalez, D. Castro-Rodriguez, A. Garcia-Moya, and A. E. Wilson. 2021. Planktonic cyanobacteria from the Abreus Reservoir, Cienfuegos, Cuba. Pan-American Journal of Aquatic Sciences 16(1):20-29.

Abstract

The study of the cyanobacteria that make up the phytoplankton community of reservoirs is very important due to the production of toxins by some phytoplankton taxa. The composition and abundance of cyanobacteria and their relationship to physicochemical variables was determined during six months (March, April, June, September, November and December) in 2018 at five stations in the Abreus Reservoir, which is located in the south center of the Cienfuegos province (Cuba). Eleven new taxa were observed in the reservoir grouped into seven families, 14 genera, and 34 species. The toxigenic genera Microcystis and Raphidiopsis were observed at all collection points throughout the year, presenting a potentially persistent toxicity threat in this reservoir. Semi-accumulative blooms were reported in September. Microcystis sp. and Raphidiopsis sp. were the most abundant genera during observed blooms. The abundance of some cyanobacterial genera, including Microcystis, Aphanocapsa, Raphidiopsis and Dolichospermum, were strongly correlated with water temperature and transparency. Microcystin values are reported for the first time in Abreus Reservoir.

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Bird, G., A. E. Wilson, G. R. Williams, and N. B. Hardy. 2021. Parasites and pesticides act antagonistically on honey bee health. Journal of Applied Ecology 58(5):997-1005.

Abstract

1. Pesticides and parasites have each been linked to increased mortality in western honey bees (Apis mellifera). Currently, it is uncertain if one makes the other worse; several studies have tested for potential synergistic stressor effects, but results have been mixed.

2. Here, we use a hierarchical meta-analysis of 63 experiments from 26 studies to gain a clearer view of the combined effects of parasites and pesticides on honey bee health.

3. We found that combined pesticide-parasite treatments do tend to be deadlier than uncombined treatments but are significantly less deadly than predicted additive or multiplicative effects. In other words, combined treatment effects are not synergistic, but antagonistic.

4. Much of the previous uncertainty about the combined effects of pesticides and parasites on honey bee health can be attributed to a bias in the previous research against stressor antagonism; many researchers have excluded the possibility of antagonism a priori.

5. Synthesis and applications: Meta-analysis shows that when honey bees are stressed by a combination of pesticides and parasites, the combined stress effect is antagonistic, that is, less than the sum of its parts. A better understanding of the mechanisms underlying this antagonism could prove critical for effective management of honey bee health.

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Buley, R. P., C. Adams, A. P. Belfiore, E. G. Fernandez-Figueroa, M. F. Gladfelter, B. Garner, D. L. Straus, and A. E. Wilson. 2021. Field evaluation of seven products to control cyanobacterial blooms in aquaculture. Environmental Science and Pollution Research 28:29971-29983.

Abstract

Harmful algal blooms negatively impact water quality in hypereutrophic systems that are common in aquaculture. However, few algaecides are approved for use in food-fish aquaculture. This study assessed the effectiveness of seven products, including hydrogen peroxide (as a concentrated liquid or in granular form (PAK-27)), peracetic acid (as VigorOx SP-15 and Peraclean), copper (as copper sulfate in unchelated (powder) or chelated (Captain) forms), and a clay-based product (as Phoslock) on phytoplankton (including cyanobacteria) and zooplankton biomass. Each product was tested in a 14-day laboratory and 35- day field experiment to assess their short- and long-term performance. Although some products (i.e., copper-based and liquid hydrogen peroxide) quickly reduced phytoplankton, effects were short-lived given that chlorophyll concentrations returned to starting concentrations within 21 days. In contrast, all but one product (i.e., concentrated liquid hydrogen peroxide) maintained low phycocyanin concentrations for 35 days. Zooplankton biomass trends showed large, negative effects for most algaecides; however, zooplankton rebounded for most treatments except for copper-based products. In general, copper-based products remain the most efficient and cheapest choice to reduce total phytoplankton biomass in aquaculture systems. However, peracetic acid-based products effectively and quickly reduced cyanobacteria while having marginal effects on beneficial algae and zooplankton. Such algaecides could be effective alternatives to copper-based products for aquaculture farmers.   Hydrogen peroxide . Peracetic acid . Copper . Clay . Harmful algal blooms . Chemical control

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Barros, M. U.G., J. I.R. Leitão, T. R.B.T. Aranha, S. Simsek, R. P. Buley, E. G. Fernandez-Figueroa, M. F. Gladfelter, A. E. Wilson, and J. Capelo-Neto. 2020. Icyano: A cyanobacterial bloom vulnerability index for drinking water treatment plants. Water Supply 20(8):3517-3530. 

Abstract

Managing freshwater systems has become a challenge for global water utilities given that cyanobacterial blooms have been increasing in frequency and intensity. Consequently, a water quality index that uses conventional measurements to assess toxic cyanobacterial hazards and guide the selection of proper treatment technologies could benefit water resource managers about water quality parameters routinely analyzed in line with environmental changes. An index model, called Icyano, showed that chlorophyll-a, cyanobacterial concentration, and total nitrogen were most important for the index. All reservoirs classified as good by Icyano used direct filtration water treatment technology. Many of the medium Icyano-classified reservoirs used a pre-treatment unit followed by a direct filtration unit. Two reservoirs that were classified as bad or very bad have been utilizing pre-treatment þ direct filtration or a complete cycle technology, respectively. As the Icyano index increases, water treatment plants should switch from direct filtration to using a pre-treatment to improve finished water quality. Findings from this project suggest that the direct filtration technology initially used in water treatment plants is not capable of meeting the current water quality guidelines in reservoirs that contain adverse water quality conditions, mostly related to an increase in toxic cyanobacterial blooms. As such, based on our findings, we recommend prioritizing financial resources towards pre-treatment technology or changes to more advanced technologies when Icyano index values increase.

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