Presentation on theme: ""A stench from its inky surface putrescent with the oxidizing processes to which the shadows of the overreaching trees add stygian blackness and the suggestion."— Presentation transcript:
"A stench from its inky surface putrescent with the oxidizing processes to which the shadows of the overreaching trees add stygian blackness and the suggestion of some mythological river of death. With this burden of filth the purifying agencies of the stream are prostrated; it lodges against obstruction in the stream and rots, becoming hatcheries for mosquitoes and malaria. A thing of beauty is thus transformed into one of hideous danger." Texas Department of Health 1925 "There are three kinds of lies. Lies, damned lies, and statistics!" Mark Twain Under carefully controlled laboratory conditions an organism does what it damn well pleases. Harvard Law "What's the use of their having names", the gnat said, "if they won't answer to them?" "No use to them," said Alice; "but it's useful the people who name them, I suppose.“ Through the Looking Glass – Lewis Carroll
Cyclomorphosis Cyclomorphosis is, as the name indicates is a cyclic change in body form. This occurs primarily in female lemnetic species such as Daphnia pulex and Daphnia rosea. A population of cyclomorphic species has a homogeneous “normal”or rounded head, form in the fall, winter and early spring. As the water becomes warmer the populations develops, however, there is a commonly progressive increase in the longitudinal axis produced by a general elongation of the head and the appearance of a “helmet”. Characteristically, the helmets become fully developed by midsummer, when they may be quite bizzarre. Beginning in late summer or early autumn, the morphology of the head progressively reverts so that the “normal” condition prevails by late autumn. In the words of Coker (1939), “The changes in form are not simple functions of external conditions or of any inherent cycle, but rather of a combination of internal and external conditions in a way that becomes exceedingly baffling the more we know about it.” Theories about helmet shapes: Under conditions of low dissolved oxygen Cladocera often produce hemoglobin to facilitate the transfer of oxygen. Studies have been done which strongly suggest that given the choices of red/pink Cladocera and a normal colored Cladocera, fish choose the red/pink Cladocera. There would therefore appear to be a selective disadvantage to becoming red/pink. One theory suggests that the increased size of the helmet of Cladocera functions to increase surface area over which oxygen can be extracted from the water and therefore changing helmet dimensions would be a function of reduced dissolved oxygen. Another theory suggests that as the water temperature increases the density of the water decreases and therefore animals such as Cladocera have to expend more energy to keep from sinking. Since the food of the cladocerans is mostly algae and since algae live near the surface, decreasing the amount of energy necessary to stay higher in the water column would be a selective advantage. One way to counter the tendency to sink would be to increase the helmet dimensions.
D-H are all Daphnia retrocurva
Poikilotherm – having a body temperature that varies with the environment, cold blooded as are amphibians, reptiles, fishes, insects Homiotherm – having a constant body temperature, warm-blooded as are mammals and birds Q 10 law or VanHoft’s Law which states that a doubling of temperature between 10 and 20 ºC increases the metabolic rate by 2 fold. Inverse metabolic rate law – the smaller the organism the greater the metabolic rate on a per gram basis. Therefore, it takes more energy to support 10, 1 gram organisms than it does 1, 10 gram organism. If a rhinoceros had the metabolic rate of a mouse it would have to endure boiling temperature at its surface in order to dissipate heat generated as a result of metabolic processes. Physoclist, physostome, no gas bladder Diurnal Diel Nocturnal
At 25 °C and well fed a female Ceriodaphnia dubia will have its first brood (4 to 6 neonates)on day 4 after its release from the brood pouch. On day 5 it will have a second brood (7 to 10 neonates) and on day 7 it will have its third brood (15 to 20 neonates) All of these offspring will be female unless something happens to induce the sexual part of cyclic parthenogenesis.
Very Early Stages of Development Embryo (0 hours old)
Embryo +3 Hours
Embryo +5 Hours Old
Embryo +8 Hours
Embryo +14 Hours
Young C. dubia In Last Embryonic Membranes
First Antennae of Female Ceriodaphnia dubia
First Antennae of Male Ceriodaphnia dubia
Female With Fertilized Egg In Brood Pouch
Ephippium With Resting Egg
Sampling Devices Ekman Dredge Ponar Dredge Surber Sampler Kick Net ½ meter net – macrozooplankton Microzooplankton closing net Artificial Substrates Diatometer
Mean, Variance, Standard Deviation and Confidence Limits Data Set 1Data Set Total n Ave Variance St. Dev C.I. 10+/-0 10+/-17.7 Variance = (x i 2 ) - (x i ) 2 /n Standard Deviation (St. Dev) = square root of the variance Confidence Interval (CI) = Mean t value (St. Dev.) The t value is chosen based on sample size and or probability level t value for 95% Confidence Interval and n=10 is n-1 nn
1- /2 n-1 d.f. If = 0.05
Data Set Calculate the mean, variance standard deviation and 95% Confidence limits for Data Set 3 Mean = 13.5 Variance (s 2 ) = Standard deviation = 7.43 Mean 5.3 (13.5 5.3) If you have an n of more than one you can calculate a mean and confidence intervals about the mean
Ho: There is no difference in the mean number of benthic organisms above and below the outall. Ha: There is a difference in the mean number of benthic organisms above and below the outfall. Failing to reject the null hypothesis does not mean that there is not a difference!!!!
Correlation and Regression The purpose of correlation analysis is to measure the intensity of association observed between any pair of variables and to test whether the association is greater than can be due to chance alone. Once established, such an association is likely to lead to reasoning about causal relationships between variables. Students of statistics are told at an early stage not to confuse significant correlation with causation. Regression deals primarily with the means of one variable and how their location is influenced by another variable. Regression comes close to implying cause and effect relationships. Thus, where a correlation coefficient tells us something about a joint relationship between variables, a regression coefficient tells us that if we alter the value of the independent variable then we can expect the dependent variable to alter by a certain amount on average. The correlation coefficient r can range between -1 and +1 and the value of r tells us something about the degree of relationship between the two variables. The coefficient of determination r 2 used in regression analysis (the square of the correlation coefficient) tells us how much of the variation in the dependent variable can be explained by its association with the independent variable. An r 2 of 0.90 indicates that 90% of the variation in the dependent variable can be explained by its relationship with the independent variable. In a sample size of 200, an r of 0.2 would be significant at the 1% level of significance, but the would only indicate that 4% of the variation in Y could be explained by its relationship with the X variable. A verdict of statistical significance shows merely that there is a linear relationship with a non-zero slope.
In fact, the condition factor was significantly correlated with DNA damage (R= , P=0.045) and MT levels (R= , P=0.03). Significance in these cases means that the slope is statistically significantly different from 0. At a probability level of 0.05, any value of P less than this would be statistically significantly different = 17% = 39%
Starlings (Sturnus vulgaris) It is the first of February, and everyone is talking about starlings. Starlings came to this country on a passenger liner from Europe. One hundred of them were deliberately released in Central Park. According to Edwin Way Teale, their coming was the result of one man’s fancy. That man was Eugene Schiefflein, a wealthy New York drug manufacturer. Schieffelin formed a club called The American Acclimatization Society who had as their goal the introduction into the US all the birds mentioned by William Shakespeare. The birds were released in Central Park in New York and first nested under the eaves of the Northwest wing of the Museum of Natural History. The birds acclimated splendidly, in less than 60 years the 100 or so birds released into Central Park increased to more than a million and by 1954 had reached Alaska. “The king forbade my tongue to speak of Mortimer. But I will find him when he is asleep, and in his ear I’ll holler ‘Mortimer!’ Nay I’ll have a starling shall be taught to speak nothing but Mortimer, and give it to him to keep his anger still in motion” was the only line in Henry IV that provoked such a reckless act. These birds are controlled in England and other parts of Europe by the normal array of competitors, predators and diseases with which the bird evolved. These controls were not present in the US so the bird spread rapidly, and out competed many of our native birds. You’ll begin to hear pneumatic cannons on our campus a little later in the spring as attempts are made to drive off the starlings and boat tailed grackle that roost on our campus. Anne Dillard in her book Pilgrim at Tinker Creek writes, “Starlings are notoriously difficult to “control”. The story is told of a man who was bothered by starlings roosting in a large sycamore tree near his house. He said he tried everything to get rid of them and finally took a shotgun to them killing three. When asked if that discouraged the birds, he reflected a minute, leaned forward, and said confidently, ‘Those three it did.’
In 1912 The English Sparrow As a Pest? Farmers Bulletin #493, by USDA noted they eat more than ½ their own weight in grain or other food a day. It contained recipe for house sparrows. Passer domesticus Several different versions regarding the introduction of the English sparrow. The sparrow entered the US as a gesture of friendship. As the steamship Europa steamed up the Hudson River the birds were released as a gesture of friendship to the U.S. In reality the English sparrow was introduced numerous times before it finally took hold. Native to the Old World, the bird was first introduced into the United States about 1850 to combat cankerworms, and it rapidly became widespread. Aggressive as well as prolific, it has largely replaced many native birds in urban areas.
By 1887, some states had already initiated efforts to eradicate HOSPs. States such as Illinois ( ) and Michigan ( ) established bounty programs. According to Keith Kridler, since the bounty on "English" Sparrows was only a few cents per bird in many states, young children killed these birds to earn money for "hard candy." The children quickly learned to wait for the eggs to hatch and thus quadruple their bounty. County clerks often felt sorry for these children, and paid out the bounty on any species of sparrow. A 3/16/1892 article in an Indiana PA paper stated "The different county treasurers of Illinois have paid out in round figures $8,000 as bounty money under a law allowing 2 cents for the head of each sparrow killed during December, January and February in that State. This shows that about 450,000 sparrows were killed, but the frisky bird seems more numerous than ever." On 09/06/1888, The Cartersville Courant-American newspaper noted "The English Sparrow, with its grown and growing progeny, is a conspicuous nuisance. Can they be no way devised to abate him, if not totally, at least partially?" An 1883 article in The Messenger (Indiana, PA, 06/27/83) said "The little sparrow has been declared an outlaw by legislative enactment and they can be killed at any time. They were imported into this country from Europe some years ago as a destroyer of insects, but it has been found they are not insectivorous. Besides they drive away all our native song birds and give no equivalent. Let them all be killed." In 1903, W.L. Dawson wrote "Without question the most deplorable event in the history of American ornithology was the introduction of the English Sparrow." (The Birds of Ohio, 1903)
Professor Ettiene Leopold Trouvelot Professor Trouvelot wanted a hardy caterpillar which would feed on oak leaves and spin a cocoon of silk. He thought such a useful creature might be produced by crossing the American Silk Moth, Bombyx mori, which feeds on mulberry and produces a large cocoon, with the Gypsy Moth, Lymantria dispar, which feeds on oak leaves. He was apparently culturing the gypsy moths on trees in his backyard when some of them escaped. Trouvelot understood the potential magnitude of this accident and notified local entomologists, but no action was taken. After the “accident”, outbreaks began to occur in Trouvelot’s neighborhood and in 1890 the State and Federal Government began their attempts to eradicate the gypsy moth. Trouvelot apparently lost interest in entomology and became interested in astronomy. About 10 years after the accident He became famous for his illustrations of astronomical details of Venus and was eventually given a position at Harvard University in Astronomy. A crater on the moon was named in honor of Trouvelot and he won the French Academy’s Valz prize for his astronomical research. The gypsy moth is now one of North America’s most devastating pests. In one of their record breaking years they defoliated almost 13 million acres; in 1993, they devoured a mere 1.8 million acres. This species originally evolved in Europe and Asia where it has existed for thousands of years. Each year about 1 million acres of forest are sprayed aerially with pesticides in order to suppress outbreaks of gypsy moth populations.
Though some areas are treated by private companies under contract with private land owners, most areas are sprayed under joint programs of the state and USDA Forest Service. Millions of dollars of tax money have been spent trying to eradicate and/or control the gypsy moth. More recently, the Asian gypsy moth—traveled as stowaways on boats from Russia to the West Coast in 1991 and from Germany to North Carolina in The Asian moths eat more voraciously than the Europeans and, because the females can fly, may spread four to five times faster. This gypsy moth is known to feed on the foliage of hundreds of species of plants in North America but its common hosts are oak and aspen. Gypsy moth hosts are located throughout most of the conterminous US but the highest concentrations are in southern Appalachian Mountains, the Ozark Mountains, and the Northern Lake States. Every year isolated populations of are discovered beyond the contiguous range of the gypsy moth. Most die out but it is inevitable that the gypsy moth will continue to expand in the future. New studies suggest that Dimilin, one of the most effective pesticides against the gypsy moth, does more damage to the environment than previously thought. Dimilin, also destroys insects vital to the health of the forest ecosystem. Dimilin is the cheapest and most efficacious way to kill gypsy moths but the chemical has also become the “bad boy” of pesticides because of its non-target effects. Studies indicate that of all the arthropods in the tree canopy, the macro- Lepidoptera larvae which includes the butterflies and big moths suffer the greatest loss. These arthropods, and others don’t seem to recover for longer than a year after spraying, play a critical role in the forest ecosystem as food for bats and birds. Dimilin is also incredibly toxic to aquatic invertebrates compared with alternatives.
Under the Toxic Substances Control Act (TSCA) the risk of chemicals to human health and the environment are supposed to be evaluated before a chemical is allowed into commerce. Many of the 100,000 chemicals in commerce have never been evaluated because they were already in commerce when the TSCA was passed in Approximately 2,000 new chemicals come into commerce in the US each year. The ecological risk assessment is done by calculating the ratio between the Predicted Environmental Concentration (PEC) and the Predicted No Effects Concentration (PNEC). For fish medicines*- based on acute data the ratio of these two parameters is 3 or the DT50 in water is greater than 4 days further studies including chronic toxicity are carried out. *the various factors DT (dissipation time), K ow, organisms tested vary depending on the environmental compartment into which the chemical might go (air, water, soil, etc.)
Log K ow for selected environmental contaminants….. DDT 6.19 (1,548,816 times more in octanol than in water). DDD 5.5 DDE 5.7 PCBs congeners range from 4.65 to 7.36 (22,908,676) with the higher the chlorination the greater the log K ow Synthetic musk compounds used in detergents, shampoos, perfumes K ow 6 Triclosan log K ow 4.76, methyl triclosan log K ow 5.2 2,3,7,8-TCDD (dioxin) K ow 6.80 contaminate in 2,4,5,T Dibenzofuran K ow 5.17 contaminate in 2,4,5,T Chloroform K ow 1.97 Benzene K ow 2.13
The use of dimilin (diflubenzuron) is expected to cause adverse acute and chronic effects to both freshwater and estuarine/marine invertebrates, including endangered species. Chitin inhibitor. To lessen the environmental risks posed by diflubenzuron, EPA is requiring the following risk mitigation measures: Row crops and orchard uses must include a 150 foot buffer zone for aerial applications and a 25 foot vegetative buffer strip to decrease runoff in all cases (buffer strip will also serve as a buffer zone for spray drift from ground applications); Aerial applications must include the most current spray drift language; and All products must CONTAIN a hazards statement warning about possible adverse effects to aquatic organisms.
White Pine Blister Rust – Cronartium ribicola Introduced into the US from timber shipments from Europe. It is a heteroecious (requires two hosts) parasite. The two hosts are the white pine tree which is commercially valuable and wild currant and gooseberries of the Genus Ribes. One spore is found associated with the white pine tree and this spore must be transmitted to the intermediate host, the wild currant or gooseberry before the spores infectious to the white pine tree, are formed. The spores that infect the white pine trees may travel long distances; however, the spores that carry the infection from the wild currants and gooseberries to the white pine trees seldom travel more than 1000 feet. The control strategy for this disease was to eradicate the wild currant and gooseberry bushes within 1000 feet of white pine trees. We used 2,4,5-Trichlorophenoxy acetic acid and 2,4-Dichlorphenoxy acetic acid. 2,3,7,8-Tetrachloro-dibenzo- p-dioxin Unlike PCBs dioxins have no uses they are contaminants of manufacturing Agent Orange has been linked to cancers and other diseases in several epidemiological studies. The Agent Orange cancers and diseases include prostate cancer, respiratory cancers, (lung, trachea/bronchus, larynx), soft- tissue sarcoma, non-Hodgkin lymphoma, Hodgkin disease, chronic lymphocytic leukemia (CLL), and multiple myeloma.
Hydrilla sp Most native aquatic vegetation enhances aquatic ecosystems. Some of the benefits that are derived include fish and waterfowl habitat, sediment stabilization, and improved water quality with respect to nutrient removal and water clarity. However, many introduced species can have negative impacts. Aquatic ecosystems are often destroyed as a result of the increased biomass, dense canopy production, and the loss of diversity due to aggressive, weedy growth patterns that overwhelm native vegetation. One such non-native aquatic plant that causes excessive negative impacts is hydrilla (Hydrilla verticillata. Hydrilla is native to Southeast Asia and Australia. It was first discovered in the U.S. in the 1960s. Two distinct biotypes; one monoecious (both sexes on the same plant), and dioecious (one sex per plant) exist in the U.S. Monoecious Hydrilla was discovered in 1982 in the Potomac River, just outside Alexandria, VA. It has since been found in other parts of Virginia, in addition to North Carolina, Delaware, Maryland, California, and Washington. Hydrilla is also found in Texas and in fact is in Lake Ray Roberts, North Lake, Lake Conroe, among others. Once Hydrilla invades an aquatic ecosystem, the plant spreads rapidly either by root crown, and stolon growth or by drifting fragments or turions. Hydrilla also produces an underground tuber, another reproductive strategy for survival. Monoecous Hydrilla produces viable seed, whereas dioecious Hydrilla in the U.S. produces only female flowers. Hydrilla can rapidly produce a dense canopy, shading out desirable native vegetation and reducing plant diversity. To improve Hydrilla management, the U.S. Corps of Engineers’ Aquatic Plant Control Research Program supports studies in four main technology areas. Biological control, chemical control, ecological control, and simulation technologies. Biological control (fungal pathogens, insects), chemical control (exposure time for herbicides, and use at the operational level), ecological control investigates parameters determining the distribution, The simulation technology has been developing growth models for Hydrilla and specific control techniques such as herbicides, harvesting, and/or triploid grass carp.
Polyploid – an individual or species whose chromosome number is a multiple other than two of the haploid number of chromosomes. Polyploidy – a condition in which an individual posses one or more sets of homologous chrmosomes in excess of the normal diploid sets as, triploidy, tetraploidy, hexaploidy, octaploidy, and 16, 32, 64 etc. ploidy. Colchicine Heterosis – hybrid vigor, increased size, faster growth rates, resistance to disease, etc. Homologous chromosomes – a pair of chromosomes which have identical genes on their alleles
Water Hyacinth (Eichhornai crassipes) Hyacinth was allegedly first brought from Brazil as table decorations for the 1884 Cotton States Exposition in New Orleans. A woman brought one from the exposition home to Florida and put it in her backyard fish pond. Within 10 years the colorful plant had become a public menace. Unchecked by natural enemies and nourished by Florida’s nutrient rich waters, the water hyacinth, which can double its population size in two weeks, rapidly displaced native aquatic plants and took over. Transported by boat propellers, river currents, birds, and wind the plant was soon widely spread. The hyacinth is very plastic in its habitat. It has a tenacious ability to multiply. It floats on the surface and extends its roots 6 to 24 inches into the water. It can survive under extreme conditions. If water dries up it extends its roots into the bottom mud. The dense mats block the surface exchange of oxygen from the atmosphere to the water which can lead to anaerobic conditions. The mass can become so dense as to cause floods during spring runoff.
Control of hyacinth…. Efforts to control the water hyacinth began in 1898 with the “help” of the Army Corps of Engineers which was authorized by Congress to remove hyacinth from navigable waters of Florida, Mississippi, Alabama, Louisiana, and Texas. The methods they used were: 1.Mechanical chopper 2.Within two years the COE found a chemical sodium arsenite, which did the job more efficiently. Even though sodium arsenite was recognized as a deadly chemical, the COE used the chemical for hyacinth control for about 35 years between 1902 and In 1937 a new crusher boat was introduced that had a large conveyor belt. Plants were harvested and transported to shore to dry. It did not operate well in shallow water and the cleared areas were quickly re-inhabited by plants that were not removed. 4.In the mid 1940s the hebicide 2,4-D became available and has been used extensively. 5.Amazingly, the integration of mechanical removal along with herbicide application is being used to control infestations.
More recently scientists have sought to join forces with nature to control hyacinth. There are several predators (herbivores) which in large enough numbers could eliminate the constant attention and manpower necessary in mechanical and chemical control. A species of weevil from Argentina is being used. This species feeds exclusively on hyacinths so there is “no danger” it will attack beneficial plants. There is a small snail from Puerto Rico that has been examined but it feeds on plants other than hyacinth. Other mites, fish, turtles have been tested as biological control mechanisms. Studies at the University of Florida in Gainsville analyzed the chemical content and nutritional value of hyacinth as cattle feed. Found that it cannot occupy more than 25% hyacinth or the cattle’s weight will go down. Another problem is that cattle apparently don’t like its taste. More than a century of control efforts with expenditures of millions of dollars with minimal success.
Waif – something found without an owner and especially by chance………
Fire Ants Seven species of fire ants (Solenopsis) are distributed throughout the warm temperate regions of the Americas. Shortly after World War I a dark form S. saevissima from Argentina became established in Mobile, Alabama and slowly spread to surrounding regions. In the 1930’s a smaller reddish form of Solenopsis appeared in the same region, apparently representing a second major introduction. The latter form aggressively made its way beyond the State’s borders swamping out by interbreeding and internecine warfare (violent death marked by slaughter) the established black phase. At present the North American populations are chiefly the red phase, tending to replace native forms as well as the dark phase. In 1957 the U.S. Department of Agriculture requested congressional approval for control of the fire ant. The request was granted and a 2.4 million dollar allocation was approved with the stipulation that matching funds be made available. Most states and many individuals did respond with matching funds, but very often control programs went ahead without them. A massive operation was set up with great speed. The first spraying using 2 pounds of dieldrin (chlorinated hydrocarbon, on the POPs list, log K ow 5.17) or heptachlor (chlorinated hydrocarbon on the POPs list, Log K ow 5.5) per acre began in November Over two and one-half million acres were aerially treated. Not until the operation was well underway were wildlife and health authorities notified. Immediate opposition to the program resulted-opposition was to grow to a national controversy. Fish, wildlife, livestock, and poultry suffered losses, the destruction of wildlife bordered on the catastrophic. The insect was not considered more than a nuisance in any of the southern states; it did not destroy crops, wildlife, and livestock.
However, chemicals did eliminate vertebrates from some areas, it did cause residue problems, it did contribute to insect outbreaks themselves requiring control. It did not eradicate the fire ant; the ants re-infested most of the treated areas. The Plant Pest Control Division of the Dept. of Agriculture had clearly made a massive mistake; the operation was a failure from its inception. Between Mirex was used as a bait to kill fire ant colonies. Mirex was banned for use (it is on the POPs list, Log K ow 5.28) by EPA because it was shown to pose serious human health hazards. Mirex is converted to Kepone (Log K ow 4.07) by photolysis. The imported fire ant now infests more than 230 million acres in Alabama, Florida, Georgia, Louisiana, Mississippi, North and South Carolina, and Texas. Somewhere in the neighborhood of 175 to 200 million federal dollars have been spent trying to first to eradicate and now control this pest. Economic-When soybean combines cut through fire ant mounds their blades and rollers must be replaced two or three times a season compared to once every four years under good conditions. Farmers have been known to leave valuable crops in the field to protect their machinery. Citrus growers in Florida are spending about $110/acre/year to replant some varieties of young trees that die because they are girdled by fire ants. Studies by two U of Florida researchers found that infestations of fire ants actually increased on insecticide treated plots that originally had low infestation levels. The amount of increase on treated plots was somewhere between 200 and 3000 percent. Because the imported fire ants colonize better than other ants you inadvertently select for imported ants when you eradicate all other ants.
Home control can be achieved by using boiling water on the mounds. Tends to kill the grass around the mounds. Farmland and Rangeland controls using synthetic growth hormones like Pro-Drone that prevents the larvae from developing into normal workers. Large areas of Texas have been treated. Some researchers believe that the Pro-Drone will act like the broad spectrum pesticides and actually increase the infestation. Researchers are looking for predators, fungi, or bacteria in native Brazil for control mechanisms. In Brazil the fire ant is not a significant problem. Clearly something in Brazil is controlling the density of fire ants. Our native fire ant species is a minor nuisance at home, but a major pest in India where it was inadvertently introduced. Former Texas Agriculture Commissioner Regan Brown told a national fire ant symposium that, “This is not an infestation it is an invasion.” This is the same guy who, on national TV, stuck his fist into a fire ant mound and then spent the rest of the interview trying to get the dam things off of him.
Zebra Mussel (Dreissena polymorpha) The Zebra mussel is a fingernail sized mussel native to the Caspian Sea. First discovered in the US in 1986 in the St. Clair River near Detroit where larvae were probably discharged along with freshwater ballast, these incredibly prolific bivalves have spread explosively throughout the Great Lakes. Female Zebra mussels can produce up to a million eggs per year, which develop into microscopic, free swimming larvae that form shells and attach to any surface. Unchecked by natural predators—in Europe they are eaten by fish and diving ducks-the mussel can reach population densities of >90,000 per square meter. They clog pipes and shut down water intake systems (steam electric plants). They pile up on boats, buoys, and piers crowding out native species. One utility estimated it will cost 50 to 100 million dollars to scrape the mussels from cooling pipes at their power plants. One “beneficial” effect is that the mussels have made Lake Erie noticeably clearer by filtering water through its feeding apparatus. The exotic Zebra mussel probably invaded the Mississippi Basin via canals linking Lake Michigan to the Illinois River, a major tributary of the Mississippi. First reports in the basin were from these canals in 1989 and 1990, so it is not surprising that the densest and most extensive populations are from the Illinois River (up to 94,504/m 2 ). The percentage of native mussels infested with Zebra’s increase from 3% up river to 99.5% down river. Judging from researchers in the area the Zebra mussels threatens the 23 native species of mussels. Freshly dead native mussels (with meats inside) were found so heavily infested with zebras that their shells could not be forced closed. Others were held shut by byssal threads (mechanism by which Zebra mussels attach themselves to the substrate). Mussels that can neither close nor open will not survive. Researchers recommend that action be taken now to cryogenically preserve gametes or fertilized eggs of native riverine mussels or to move adults to hatcheries where they can be maintained and perhaps propogated. Native mussels might be stocked in the future if the Zebra mussel populations every crash.
Data: 26,000 acre lake (surface acres) “Weed” in the lake is Hydrilla veticillata, native of the old World tropics i.e., Africa Weed is spreading at the rate of 15% per year. Home owners around the lake have collected money and tried: Mowing machines, and Eli Lily Co. spread chemicals, nothing has stopped the spread. Lake is also used as a drinking water source for a major metropolitan area (provides about 40% of its drinking water). Home owners and marina owners claim they are losing 10s of millions of dollars in lost revenue and property values. Weed has choked off recreational area use of shore lines and coves. The weed often traps swimmers and two have drown. Home owners have the opportunity to buy 240,000 grass carp (white amur, Ctenopharyngodon idellas) for $250,000 they have raised from private sources ($1.04 per fish). The grass carp has been imported from the Soviet Union, and is being tried as a water hyacinth control as well. What Lake is it? You work for the Texas Fish and Game Commission and you have to decide whether or not to let them bring in these fish. A law exists that prohibits the import of piranha and walking catfish in addition to the grass carp. The Legislature would have to be convinced to do this. Bass fisherman say that importing the fish will make the best large mouth bass lake in the State the worst.
Characteristics of the grass carp: 1.Known to eat vegetation other than Hydrilla. 2.Requires running water to breed successfully. 3.Resembles a big silver colored goldfish and can weigh up to 100 pounds. Texas legislature was convinced to approve a 5 year study beginning in 1981: 1.By 1984 all significant vegetation in Lake was gone 2.Grass carp are eating leaves off of willow trees, and 2-3 inches of grass up from the shoreline. 3.Largemouth bass are harder to catch (lack of cover and declining population?). Bass catch is down 25%, crappie catch is down 60%; grass carp catch is way up, corn and dog food used as bait, fish is a vegetarian (20 to 25 lbs each), claims are made they are good to eat. Water fowl populations are way down. 4.Grass carp now found in the Trinity and San Jacinto Rivers. Where they came from no one is sure. 5.Some Parks and Wildlife biologists believe: a. the carp will die out in 5 to 10 years because they need running water to spawn. b. Hydrilla which still has roots in the lake bottom will return c. Pressure now on to use grass carp in Houston Lake, Lake Jacsonville, Lake Livingston, Lake Worth, and Lake Plaestine. Triploid carp are available at $5.00 per fish. A triploid grass carp is now in effect on this lake. If a grass carp is caught it must immediately be returned to the water.
There have been repeated instances over time where organisms, for a variety of reasons, have been imported into the U.S. In some cases the organisms were brought in on a whim (starlings), in the name of science (gypsy moth), to attack a specific problem (English sparrow) or as an accident. The current epidemic of the spread of bird flu is an example of how quickly things can spread due to both natural conditions as well as our ability to travel almost anywhere in the world. The zebra mussel entered the US in the ballast of a ship as have many other hitchhikers, the reverse movement from the US to other countries is also possible. A law is before Congress (2008) to require ballast to be dumped and filled with saline water before ships can enter territorial waters. One underlying problem associated with almost all of these introductions is that at “home” they are generally well behaved (their populations are controlled by many forces they have evolved with) when introduced into a foreign area without the control mechanisms the populations almost always explode. Sometimes we introduce new species in an attempt to solve problems created by previous introductions but end up making the situation worse. In Hawaii and several Caribbean Islands for instance, mongoose were imported to help control rats that had escaped from ships and were destroying indigenous birds. Since the mongoose were diurnal, and the rats were nocturnal they tended to ignore one another. Instead the mongoose also killed native birds and further threatened endangered species.