Golden Algae an Invading Toxic Protist
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Golden Algae An Invading Toxic Protist Karen Glenn Bluestem Chapter – Texas Master Naturalist Austin College – Department of Chemistry Scientist III - University of Oklahoma Biological Station (2007 – 2011) Texas Master Naturalist Annual Meeting October 19, 2019 – Rockwall, Texas What exactly is Golden Alga? • Golden algae is not considered a “true” alga. There are approximately 1000 species of Chrysophytes that are collectively referred to as “golden algae” due to the coloring of the water during an active bloom events. • Kingdom Protista (Five Kingdom System) or Chromista (Seven Kingdom System) – simple eukaryotic organisms Not a plant, animal, or fungi Usually found in an aquatic environment Usually single celled organisms, but may sometimes be multicellular Often have flagella or cilia for movement May be heterotrophs (saprotrophy and phagotrophy) or autotrophs (photosynthesis) Historically grouped with Protozoa, Slime Molds, Sporozoans such as Giardia and Plasmodia, and Amoebas May have the ability to form cysts and/or practice allelopathy when conditions are unfavorable The Five Kingdom System Illustration by Robert G. Howells, TPWD Golden Alga – Prymnesium parvum Characteristics: Single-celled marine species – prefers a saline environment Haptophyta – prominent haptonema, a microtubular appendage Two uneven flagella – provides locomotion Photosynthetic – two prominent chloroplasts Submicroscopic organic scales – requires an electron microscope Golden Algae cannot be detected without magnification due to its size! The Scandinavian Culture Collection of Algae and Protozoa at the University of Copenhagen A microscopic picture of a golden alga cell (1000X magnification). Photo by Greg Southard, TPWD Cells average ~ 10 micrometers (range from 8 to 15 micrometers). (For comparison the thickness of a human hair averages around 90 micrometers.) P. parvum was first identified by Liebert and Deerns during a 1920 fish kill in the Netherlands. Liebert F, Deerns WM. Onderzoek naar de oorzak van een Vischsterfte in den Polder Workumer Nieuwland, nabij Workum. Verhandungen en Rapporten uitgegeven door Rijkinstituten voor Visscherijonderzoek. 1920;1:81–93. P. parvum was confirmed in 5 separate water sheds within Texas in the 1980’s. Note: not all watersheds have experienced fish kills. First confirmed appearance in 1985 in the Pecos River watershed, although earlier fish kills may have been caused by P. parvum. Responsible for an estimated 30-50 million dollar loss to recreation and aquaculture industries in affected areas. Dundee State Fish Hatchery’s striped bass production wiped out in 2001 due to using contaminated lake water. Since the first confirmed arrival of P. parvum, it has been reported in 20 states, and has recently been confirmed in the Rio Grande, San Jacinto and Wichita river watersheds. States Reporting P. parvum Alabama, Arizona, Arkansas, California, Florida, Georgia, Hawaii, Louisiana, Maine, Mississippi, Nevada, New Mexico, North Carolina, Oklahoma, Pennsylvania, South Carolina, Texas, Washington, West Virginia and Wyoming. Texas Parks and Wildlife Where Did Golden Algae Come From? “Everything is everywhere, but, the environment selects” – Baas Becking hypothesis (1934) • P. parvum has always been here in very small numbers until environmental factors favored an increase in its number to detectable (and harmful) limits. • Bilge water from transport ships • Bird guano and possibly feathers • Transfer of resting cysts in sediment • Boats and live wells • Bottom line: no one knows how it first got here, but it is probably a mixture of all the above Confirmed P. Pa r vu m Fish Kills in Lake Texoma First fish kill in Lake Texoma occurred in Jan – Mar of 2004. Density was approximately 144,000 cells mL-1. Bloom was sporadic with fish kills mostly observed in Lebanon Pool and the mouth of the Big Mineral arm. No kills were observed in 2005, but subsequent kills observed 2006 and 2007 (and beyond). Most of the latter kills have been in Lebanon Pool. Full time monitoring program began in Feb 2006 at the University of Oklahoma Biological Station, funded Image: David Hambright, Lebanon Pool Fish Kill, 2004. by the Oklahoma Department of Wildlife Conservation. Plankton Ecology and Limnology Lab (PELL) – University of Oklahoma Biological Station Detecting and Monitoring P. parvum (PELL) Direct cell counts – requires ability to visually detect and count cells under a microscope • Very labor intensive! • Limits of approximately 333-1000 cells/ mL Cell counts with a Flow Cytometer – uses cell’s ability to self-fluoresce vs. size to count cells. • Fast, relatively easy. • Possibility of other cells being counted as target. • Can sometimes be difficult with mobile species (migrate away from “sipper”) Cell counts with qPCR – using specific DNA sequences to detect and quantify algal cells in water samples. • Specific, depending on primers used • Ability to detect very low concentrations (~ 6 - 22 cells/mL, depending on volume of water sampled) • Quick and repeatable • Early detection of low densities • Requires knowledge of copy number for sequence used (how many copies of the sequence are in each cell) Zamor,R.M.; Glenn, K.L.; Hambright, K.D.. 2012. Incorporating molecular tools into routine HAB monitoring programs: Using qPCR to track invasive Prymnesium. Harmful Algae 15, 1-7. Lake Texoma Monitoring (PELL) Nitrogen and Phosphorus Concentrations • Nutrient loads are critical in understanding water quality. • Common ratio of Nitrogen:Phosphorus (N:P) is ~ 16:1 in nature. • N:P ratio varies across sample sites in Lake Texoma. Conductivity • Specific conductivity ranged from 887.6 µS/cm to 3,062 µS/cm, indicating high levels of current conducting ions (chlorides and salts) in the system. • These values are highest within the upper reservoir arms, notability the Red River, and generally decline moving towards the dam. Washita Arm has low conductivity. Salinity • Values ranged from 0.30 ppt in the Washita River arm to 1.70 ppt in the Red River arm. • Texoma has much higher salt content compared to other Oklahoma reservoirs. Chlorophyll • Total chlorophyll can give an idea of algal concentrations, although it is a general measure and cannot give information about species. Hambright, K.D., R.M. Zamor, J.D. Easton, K.G. Looper, E.J. Remmel, & A.C. Easton. 2010. Dynamics of an invasive toxigenic protist in a subtropical reservoir. Harmful Algae 9:568–577. What Causes Golden Algae to Bloom? Nutrient loads – Blooms are associated with changes in the nutrient levels in the water. There have been differences among studies, but generally the ratio of Nitrogen (N) to Phosphorus (P) plays a role. • P. parvum tends to bloom under high N and high P conditions. • When the environment becomes P-limited, P. Parvum becomes more toxic. • Upper Red River ratio of N:P is ~ 11:1, Washita Arm is ~17:1. • Texoma is classified as a P-limited, eutrophic lake. (Washita Arm is mesotrophic) pH – P. parvum growth is optimized at ~ pH 8 • Lake Texoma pH ranges from ~ 7.4 to 8.5, depending on inflow and conditions. What Causes Golden Algae to Bloom? Salinity – P. parvum can tolerate a wide range of salinities from 1 – 15 ppt • Ranges on Texoma vary from ~ 0.5 – 1.8 ppt. Lebanon Pool can reach ~ 2.00 ppt when isolated. Temperature – Historically, blooms happen in the Winter or early Spring. • Blooms on Texoma have shifted from early in the year (Jan – Mar) to early summer (June – July of 2017) • Is this a change or an isolated incident? Sunlight – Some studies have found that UV light reduces toxicity of P. parvum blooms. • Winter blooms may be a response from shifting from an autotroph to an heterotroph? • Less competition from other algal species in winter? How Does Golden Algae Kill Fish? P. Parvum releases several toxic compounds into the water column during a bloom (usually ≥ 50,000 cells/mL). Prymnesins – Hemolysin – Stearidonic acid – Neurotoxins? Toxins tend to concentrate as the bloom subsides • triggered by inflow ( esp. after low water events) Why are toxins released? • Competition for resources? • Stress? • Are toxins endogenous or exogenous? • Difficult to compare natural waters to lab samples. Henrikson, J.C., M.S. Gharfeh, A.C. Easton, J.D. Easton, K.L. Glenn, S.L. Mooberry, K.D. Hambright, R.H. Cichewicz. 2010. Reassessing the ichthyotoxin profile of cultured Prymnesium parvum (Golden Algae) and comparing it to samples collected from recent freshwater bloom and fish kill events in North America. Toxicon 55:1396-1404. Most Recent Lake Texoma Fish Kill June 21 to 24, 2017 - Paradise Cove , Big Mineral arm. • approximately 157,000 dead fish in the area • 90 percent were small (1 inch) threadfin shad Other fish species significantly affected (estimates): • 9,122 freshwater drum • 1,332 crappie • Small numbers of catfish and other game fish • No striped bass observed. Texas Parks and Wildlife Department (press release) What does a Golden Algae Bloom look like? Brazos River Authority and Texas Parks and Wildlife Department Texas Parks and Wildlife Department University of Oklahoma Plankton Ecology and Limnology Lab During full bloom water takes on a golden color. Foam often forms along shoreline, especially in windy conditions. Fish kills usually begin to appear as water becomes discolored. Birds and other animals are often observed eating dead fish and drinking discolored water with no ill effects. What does a P. parvum kill look like? Fish may be spotted “gasping for air” at the surface of the water, even when DO is in the normal range. Dead and dying fish have brightly colored gills, sometimes damage to tissue is obvious Fins and skin areas between scales become bloody. Threadfin shad and drum are usually the first to die off, followed by crappie, sunfish, and game fish. Mussels, salamanders, and other thin-skinned species may be affected. Texas Parks and Wildlife Department © 2006 (Greg Southard) What are the Dangers to Humans, Livestock, and Pets? Complete suite of toxins and allelopathic chemicals are currently unknown. Toxins lethal to fish appear to be photolabile and degrade rapidly when exposed to sunlight. Individual toxins are very difficult to obtain and/or reproduce in the laboratory.