Aquatic Pest Research Articles

Methanization Test of Water Hyacinth and Azolla in Co-digestion and Fertilizing Value of Digestates in Benin (West Africa)

Faced with the need for an alternative energy source following the extreme pressure exerted on woody resources accompanied by the increase of aquatic pests which invade water resources, the construction of mini reactors producing clean energy, biogas based on these invasive plants becomes a challenge. This investigation aims to assess the methane production potential of water hyacinth and Azolla in co-digestion and the fertilizing quality of the digestates obtained. A bio methanization test based on various combinations of organic substrates composed of water hyacinth and Azolla alone or in co-digestion under laboratory conditions at mesophilic temperature and neutral pH after 27 days was carried out. The source of enrichment in anaerobic microorganisms for fermentation processes in micro bioreactors consists of fresh pig manure. It appears that the combination of organic substrates including 75% of water hyacinth generated the maximum quantity of methane which is 1234 liters for one ton of organic substrates. This methane production is 1.93 times greater than that of the bioreactor containing water hyacinth alone, 1.90 times that containing azolla, 1.5 times that containing 25% water hyacinth +75% azolla then 3.04 times that containing the bioreactor composed of a high proportion of crushed Azolla filiculoides. The digestates are rich in N, P, K, Ca and Mg and had an amending power according to the NFU 44051 standard. For the construction of bioreactors with aquatic pests for the benefit of communities, co-digestion with a combination of substrates with a high proportion of water hyacinth is suggested.

Effects of a Popular Aquatic Pest Control Agent among Carp Aqua-culturists on Aquatic Microfauna Dynamics

Cypermethrin is gaining popularity among fish farmers community to control aquatic insect pests and ectoparasites. Effect of cypermethrin application at farmer select dose (@0.003 ppm) on aquaculture pests (Notonecta & small prawn) commonly found in tropical ponds along with fish fry was assessed. Effect of cypermethrin application on the composition and survivability dynamics of aquatic microfauna namely rotifer, copepod and cladocera for 8 days was studied in tropical pond conditions. Cypermethrin cause significantly higher mortality to notonecta and prawn compared to fish fry within 24 h of exposure (P<0.05).

A united front against marine invaders: Developing a cost‐effective marine biosecurity surveillance partnership between government and industry

Abstract Successful detection of introduced marine pests (IMP) relies upon effective surveillance. However, the expedience of responding following IMP detection is often dependent upon the relationship between regulators and stakeholders. Effective detection of IMP in areas such as commercial ports requires a collaborative approach, as port environments can be highly complex both above and below the water. This complexity can encompass physical, logistical, safety and legislative issues. With this in mind, the aquatic pest biosecurity section within the Department of Primary Industries and Regional Development (DPIRD) developed the State‐Wide Array Surveillance Program (SWASP) in collaboration with Western Australian Port Authorities and port industry stakeholders. The SWASP is primarily based on passive settlement arrays for IMP detection. Arrays are deployed at strategic locations within Ports. Marine growth samples collected from the arrays are processed using Next‐Generation Sequencing (NGS) to identify the presence of IMP within a specific geographical location. Over 8 years, participation in SWASP has grown from 3 to 11 ports, spanning over 11,000 km, from the tropical north to temperate south of Western Australia. The programme has proven to be highly effective as a means of fostering stakeholder involvement and, importantly for IMP surveillance. The growth and success of SWASP has continued primarily because of the commitment and farsightedness of the ports involved. The regular presence of the biosecurity regulator as a partner in SWASP has provided a consistent face for biosecurity and fostered good stakeholder relationships, ensuring there is a reliable and effective ongoing marine surveillance programme for the state. Synthesis and applications. Through a united and collaborative approach to marine biosecurity surveillance, port authorities, industry and biosecurity regulators have developed the State‐Wide Array Surveillance Program (SWASP) and closed a major gap in biosecurity surveillance. The SWASP collaboration uses passive settlement arrays and molecular analyses to provide regular marine pest surveillance from the tropics to temperate regions of Western Australia. The continued commitment has embedded valuable relationships between stakeholder and regulator ensuring ongoing surveillance in marine biosecurity for the state. The Western Australian SWASP example has inspired other jurisdictions around Australia to develop similar collaborative approaches which will have far‐reaching marine biosecurity benefits.

An Integrated Pest Management Tactic for Quagga Mussels: Site‐Specific Application of Fish Biological Control Agents

AbstractThe quagga mussel Dreissena bugensis is a harmful aquatic pest that invaded the southwestern USA in 2007. Challenges with managing this pest have been encountered because the invaded systems are primarily open‐water sources used for human consumption and/or are connected to freshwater habitats containing threatened and endangered species. Existing chemical and physical control methods are undesirable, and the use of some methods is restricted or prohibited because they pose risks to humans and ecosystems more broadly. To address this problem, we investigated the efficacy of using resident fishes as biocontrol agents for managing different life stages of quagga mussels on different spatial scales in a site‐specific manner. We conducted field experiments to test whether planktivorous Bluegill Lepomis macrochirus reduced mussel infestations on substrates of varying orientations in small and large pens through predation on larval mussels. We also performed an experiment to evaluate whether carnivorous Redear Sunfish L. microlophus reduced mussel infestations established on substrates of varying orientations in small pens through predation on juvenile and adult mussels. Bluegill significantly reduced mussel infestations on all substrates in the pens through predation on larvae and small juvenile mussels. Redear Sunfish reduced existing juvenile and adult mussel populations in some cases, with consumption varying among individuals and substrate orientations. Our results indicate that fishes, specifically Bluegill, may represent effective site‐specific biocontrol agents for quagga mussels, reducing impacts on targeted infrastructure (e.g., water towers, docks, and pipes) and habitats having different surface orientations by controlling more than one life stage of the pest. Development of an integrated pest management strategy that considers application of this tactic in combination with others would undoubtedly improve the management of quagga mussels—and potentially that of congeneric zebra mussels D. polymorpha—within lake and reservoir ecosystems.

Chemical Controls for an Integrated Pest Management Program

AbstractChemical controls ranging from natural products to synthesized chemicals are widely used in aquatic pest management activities. Chemicals can be used to lure organisms to traps or can cause direct mortality by altering the physiological function of an organism. Much of what is known about controlling pests with chemicals is from research done on terrestrial pesticides. This paper focuses on how chemicals might be used as aquatic pesticides to control or eradicate aquatic invasive species. Current control tools are described, as are new technologies designed to selectively target the pest to reduce risks to nontarget organisms and the environment.

Toxicity of the aquatic herbicide, reward®, to the northwestern salamander.

Diquat dibromide (DB) is the active ingredient in several herbicide products used around the world for industrial and recreational control of terrestrial and aquatic pest plants. This study aimed to assess the adverse effects of the commercial formulation of the aquatic herbicide, Reward®, on the Pacific Northwest amphibian species, the northwestern salamander (Ambystoma gracile). Larvae were exposed to the Reward® herbicide in a 96-h acute bioassay (0.37-151.7 mg/L DB) and a continuous 21-day exposure (0.37-94.7 mg/L DB). The 96-h LC50 was 71.5 mg/L and the 21-day LC50 was 1.56 mg/L. Collectively, the results of this study demonstrate that early life stage A. gracile larvae appear largely insensitive to acute Reward® exposures compared to early life stage fish. However, A. gracile larvae are considerably more sensitive during sub-chronic exposure (21 days) with lethal and sub-lethal effects on growth occurring in the 1-2 mg/L range, which more closely resembles the larval fish lethal sensitivity to this active ingredient. This is the first study examining the toxicity of the aquatic herbicide formulation Reward® on A. gracile under acute and sub-chronic exposure scenarios.

Effectiveness of Predator Control Set-up for Aquatic Pest Control in Earthen Ponds for Extensive Culture of Penaeus monodon (Fabricius, 1798)

Effectiveness of Predator Control Set-up for Aquatic Pest Control in Earthen Ponds for Extensive Culture of Penaeus monodon (Fabricius, 1798)

Water hyacinth: Potential and Threat

Abstract Water hyacinth in scientific name is known as Eichhornia crassipes. As an aquatic pest plant, water hyacinth are growing in water flow, rivers and lakes. Water hyacinth can spread rapidly from the normal size to two times in a few weeks to configure a mat on water surface. The presence of water hyacinth reduced the oxygen amount and nutrient around the area where water hyacinth are growing. Furthermore, the water flow and water traffic will be blocked by water hyacinth. However, water hyacinth not only a problematic plant but also a rich plant due to valuable chemicals such as lignin, cellulose and hemicellulose inside. These chemicals contribute to the utilization of water hyacinth as a biofuel. In addition, the performance of water hyacinth as absorber of various heavy metals has been proved. Objective of this paper is to comprehensive review on potential and threat of water hyacinth in environment.

Experimental evaluation of vinegar (acetic acid) for control of invasive corals (Tubastraea spp.) and a review of knowledge for other aquatic pests

Vinegar/acetic acid (V/AA) has been used to control unwanted marine and freshwater species. As a naturally occurring, available and ubiquitous substance most countries’ legislations do not consider V/AA as harmful to the environment. We investigated the toxicity of household vinegar for the invasive corals Tubastraea coccinea and T. tagusensis (Dendrophylliidae), using injection (1, 2 or 4 of 10, 20 or 40 ml of vinegar) and immersion (full and half concentration; periods of 15, 30, 45, 60 or 120 min) treatments. For Tubastraea spp., immersion treatment always resulted in the death of the corals. In contrast, the lethality of injected vinegar depended on the number and volume of injections per coral colony; partially damaged colonies may be able to recover after vinegar injection. We also carried out a critical review and analysis regarding the use of V/AA in other aquatic species. V/AA has been tested and used as a biocide from virus and bacteria to fish; as for Tubastraea spp., three quarters of studies investigated the positive effects of V/AA as a biocide, the rest negative collateral effects on non-target species. We conclude that V/AA is an effective agent for killing Tubastraea spp. and most other aquatic organisms, can be applied using different methods and in different environments for controlling: (1) invasive or outbreak species; and (2) biofouling by native or invasive species on aquaculture systems and vectors. V/AA may be used applied pre-border to shipping vectors potentially transporting non-indigenous marine biofouling species such as Tubastraea spp.

A hybrid-hierarchical genome assembly strategy to sequence the invasive golden mussel, Limnoperna fortunei.

BackgroundFor more than 25 years, the golden mussel, Limnoperna fortunei, has aggressively invaded South American freshwaters, having travelled more than 5000 km upstream across 5 countries. Along the way, the golden mussel has outcompeted native species and economically harmed aquaculture, hydroelectric powers, and ship transit. We have sequenced the complete genome of the golden mussel to understand the molecular basis of its invasiveness and search for ways to control it.FindingsWe assembled the 1.6-Gb genome into 20 548 scaffolds with an N50 length of 312 Kb using a hybrid and hierarchical assembly strategy from short and long DNA reads and transcriptomes. A total of 60 717 coding genes were inferred from a customized transcriptome-trained AUGUSTUS run. We also compared predicted protein sets with those of complete molluscan genomes, revealing an exacerbation of protein-binding domains in L. fortunei.ConclusionsWe built one of the best bivalve genome assemblies available using a cost-effective approach using Illumina paired-end, mate-paired, and PacBio long reads. We expect that the continuous and careful annotation of L. fortunei’s genome will contribute to the investigation of bivalve genetics, evolution, and invasiveness, as well as to the development of biotechnological tools for aquatic pest control.

Characterization of the pre-treated biomass of Eichhornia crassipes (water hyacinth) for the second generation ethanol production

ABSTRACTEichhornia crassipes (water hyacinth), is considered an aquatic pest. An alternative to solve the excess water hyacinth problem is to use the biomass for second generation ethanol. This process can be divided into: collection of biomass pre-treatment, enzymatic hydrolysis, fermentation and distillation. Some chemical processes for pre-treatment of biomass water hyacinths were evaluated to determine which procedure degrades the greater amount of lignin and hemicellulose which least affects the cellulose. Characterization was made from the analysis techniques: TG-DTA, XRD and FTIR. The results revealed that the biomass to water hyacinth the most efficient pre-treatment is chemical hydrolysis with sulfuric acid.

Fine-tuning for the tropics: application of eDNA technology for invasive fish detection in tropical freshwater ecosystems.

Invasive species pose a major threat to aquatic ecosystems. Their impact can be particularly severe in tropical regions, like those in northern Australia, where >20 invasive fish species are recorded. In temperate regions, environmental DNA (eDNA) technology is gaining momentum as a tool to detect aquatic pests, but the technology's effectiveness has not been fully explored in tropical systems with their unique climatic challenges (i.e. high turbidity, temperatures and ultraviolet light). In this study, we modified conventional eDNA protocols for use in tropical environments using the invasive fish, Mozambique tilapia (Oreochromis mossambicus) as a detection model. We evaluated the effects of high water temperatures and fish density on the detection of tilapia eDNA, using filters with larger pores to facilitate filtration. Large-pore filters (20μm) were effective in filtering turbid waters and retaining sufficient eDNA, whilst achieving filtration times of 2-3min per 2-L sample. High water temperatures, often experienced in the tropics (23, 29, 35°C), did not affect eDNA degradation rates, although high temperatures (35°C) did significantly increase fish eDNA shedding rates. We established a minimum detection limit for tilapia (1 fish/0.4megalitres/after 4days) and found that low water flow (3.17L/s) into ponds with high fish density (>16fish/0.4megalitres) did not affect eDNA detection. These results demonstrate that eDNA technology can be effectively used in tropical ecosystems to detect invasive fish species.

Epidemiological principles applied to design of detection/ delimitation surveys for aquatic pests and diseases

Event Abstract Back to Event Epidemiological principles applied to design of detection/ delimitation surveys for aquatic pests and diseases Anjali Pande1*, Hernando Acosta2 and Naya A. Brangenberg1 1 Ministry for Primary Industries, Biosecurity, New Zealand 2 Ministry for Primary Industries, New Zealand Surveillance for aquatic animal diseases can be challenging given the lack of boundaries in a fluid environment and often limited baseline knowledge about the demographics and spatial clustering of the organisms in question. Hydrodynamic modelling presents a way to estimate an epidemiologic unit based on probability of exposure. The authors have successfully used this technique to design spread models for OsHV-µ1 in New Zealand (Pande, et al, 2015). The same epidemiological principles applied to surveillance for aquatic animal diseases can also be used to determine the likelihood of establishment/ detection of aquatic pests. Using an incursion of the Mediterranean fanworm (Sabella spallanzanii), an unwanted and notifiable organism under the New Zealand Biosecurity Act 1993, into a new area in New Zealand, as an example we show how epidemiological risk based principles can be used to design a robust detection/ delimitation survey. The design of the detection/ delimitation surveys used predefined zones of highest potential larval propagule density, and an arbitrary survey boundary was delineated, based on modelling the hydrodynamics of the Coromandel harbour. These zones were identified by overlaying suitable habitat for Sabella and the hydrodynamic dispersal pattern from the cleaning location in ARC GIS. The dispersal pattern was based on the results of a validated lagrangian model run for the two weeks following the cleaning operation. Habitat suitability was defined based on expert opinion elicited using the Analytical Hierarchy Process (AHP) technique and a self-administrated questionnaire. The zones were then assigned a risk ranking. Sampling sites were proportionately allocated to the different zones taking into account the estimated search efficiency (specificity) of the field team and the assumed density (sensitivity) of Sabella. Since this method incorporates habitat type, hydrodynamics and characteristics such as search efficiency and assumed density (or sensitivity and specificity) specific to a given situation, it can be employed in many different circumstances to develop delimitation or detection surveys for marine pests or diseases. References References Cited: Pande, A, Acosta, H, Brangenberg, N.A and Keeling, S.E. 2015. Design of a detection survey for Ostreid herpesvirus -1 using hydrodynamic dispersion models to determine epidemiological units. Preventive Veterinary Medicine 119; 80-84. http://dx.doi.org/10.1016/j.prevetmed.2015.02.009 Other relevant references: Peeler E.J, Taylor, N.G.H, 2011. The application of epidemiology in aquatic animal health –opportunities and challenges. Veterinary Research. 42; 94. Keywords: Hydrodynamic dispersion, surveillance, Risk based, Ostreid herpesvirus, meditteranean fanworm, Aquatic epidemiology Conference: AquaEpi I - 2016, Oslo, Norway, 20 Sep - 22 Sep, 2016. Presentation Type: Oral Topic: Aquatic Animal Epidemiology Citation: Pande A, Acosta H and Brangenberg NA (2016). Epidemiological principles applied to design of detection/ delimitation surveys for aquatic pests and diseases. Front. Vet. Sci. Conference Abstract: AquaEpi I - 2016. doi: 10.3389/conf.FVETS.2016.02.00040 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 29 Apr 2016; Published Online: 14 Sep 2016. * Correspondence: Dr. Anjali Pande, Ministry for Primary Industries, Biosecurity, Wellington, Wellington, 5018, New Zealand, Anjali.Pande@maf.govt.nz Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Anjali Pande Hernando Acosta Naya A Brangenberg Google Anjali Pande Hernando Acosta Naya A Brangenberg Google Scholar Anjali Pande Hernando Acosta Naya A Brangenberg PubMed Anjali Pande Hernando Acosta Naya A Brangenberg Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

The Historic Role of Crocodiles and Other African Aquatic Pests in Current Sport Championships

Top achievements in modern sports are not distributed evenly among humans of various origins. Athletes of African origin dominate several fields of athletics, especially short- and long-distance running, which differ in their physiological and muscle structure characters and requirements. This contrasts dramatically with their near absence from the group of leading swimmers at all distances. The conspicuous absence of world-class swimmers of African origin cannot be explained by current or recent social aspects or by the history of their discrimination, and therefore deserves an alternative explanation. I propose that the conspicuous weakness of athletes of African origin in swimming is related to their evolution in the natural African environment with the probable inherited and a certain biological and/or cultural fear of predation by crocodiles and of infection by various pathogens and parasites. Members of the genus Homo that emigrated from Africa during the last 1.8 million years or have evolved outside Africa had sufficient time to get rid of the biological and/or cultural fear of swimming directly, or by gene exchange with contemporary groups that left Africa long ago and had adapted to safer water habitats. The release from the fear of crocodiles, pathogens and parasites at higher latitudes must have influenced other aspects of environmental exploitation of aquatic habitats by various hominin types, an issue outside the scope of his assay.

Are non‐native species more likely to become pests? Influence of biogeographic origin on the impacts of freshwater organisms3

Some ecologists have claimed that non‐native species are no more likely to cause ecological or economic harm than native species. We evaluated this claim by testing whether the pest status of a species is independent of its origin, using data on freshwater plants and animals established in North America and Europe. Pests were defined as those whose presence resulted in socioeconomic damage. All species were classified on the basis of whether they were native to the continent, transplanted beyond their native range within the continent (transplant invaders), or non‐native to the continent (foreign invaders). Non‐native species comprised the majority (60%) of aquatic pests in North America and Europe and were six times as likely to be pests as compared with native species. The incidence of pest species was greatest among foreign invaders. These results counter the assertion that the potential for a species to cause socioeconomic damage is independent of its biogeographic origin.

Spread and status of seven submerged pest plants in New Zealand lakes

The distribution of seven submerged aquatic pest plants is reported. Lake vegetation surveys recorded pest plants in 27.9% of 344 lakes, with two species co‐occurring in 5.8%, and three species in 2.6% of lakes. Egeria densa was most frequent (15.4% of lakes), followed by Ceratophyllum demersum (9.0%), Lagarosiphon major (7.3%), and Utricularia gibba (5.5%). Spread since 2000 has continued for five pest plants, with 34 lakes invaded by U. gibba over 2004–08 alone. Early regional sites in proximity to human population centres were likely plant liberations and numerous potential founder colonies remain in garden ponds. Human activities were important for inter‐lake dispersal, with the exception of bird‐dispersed U. gibba. Significant lake associations between pest plants, and with presence of six exotic fish species, suggest common dispersal pathways and similar introduction risks. Therefore, predictions of future spread should be possible based on sources, dispersal pathways, and identifying key risk factors for lakes.

Movement, social cohesion and site fidelity in adult koi carp, Cyprinus carpio

Abstract Koi carp is an ornamental variant of the common carp, Cyprinus carpio L., that was introduced to New Zealand in the 1960s and has since become a major aquatic pest. A total of 1265 wild adult koi carp were caught by boat electric fishing, dart tagged and released at multiple sites in the lower Waikato River and associated lakes and wetlands between September 2002 and February 2005. Subsequent recaptures by boat electric fishing and recreational fishing returned 76 koi carp (6% of all tagged fish). Of these, 85% were recaptured less than 5 km from their release site; only one fish moved more than 50 km. On seven occasions, pairs or small groups of koi carp (20% of all tag returns) that had previously been tagged and released at the same locations and times were subsequently recaptured together after considerable periods of time at liberty (mean 551 days ± 419 SD). Adult koi carp in the Waikato River showed a high degree of site fidelity, exhibited prolonged social groupings and females moved downstream more often than males.

Globalization of an Aquatic Pest: Economic Costs, Ecological Outcomes, and Positive Applications of Zebra Mussel Invasions and Expansions

AbstractThe development of trade and tourism has been as important as the biological adaptations of zebra mussels and quagga mussels in mediating the historic spread of these organisms in Europe and their invasion of North America. Canals and increased commerce mediated the spread of zebra mussels in Europe at the beginning of the Industrial Revolution and facilitated their introduction to North America near the end of the 20th century. However, recreational boating is the most likely vehicle for the more recent intracontinental invasions of alpine and subalpine lakes in Europe and the recent leap of these freshwater mussels across the Continental Divide in North America. Although viewed as pests due to their biofouling effects, their economic costs to drinking water and electrical power plant companies have been smaller than once feared, and their negative impacts on other organisms have been smaller than predicted in the more than 20 years since the start of their invasion of North America. This review of recent publications reveals that positive outcomes of the presence of zebra mussels and quagga mussels have begun to be apparent, which help ameliorate the economic costs and negative ecological outcomes that have accompanied the globalization of this aquatic pest.

Development of Sustainable Solutions for Zebra Mussel Control Through Chemical Product Engineering

The zebra mussel is an important aquatic pest that causes great damage to freshwater-dependent industries, due to biofouling. The main goal of the project discussed here is to develop improved solutions to control this species. Three approaches have been explored in an attempt to design innovative application strategies for existing biocides: (i) encapsulation of toxins; (ii) combination of toxins; (iii) investigation of the seasonal variation of the species' tolerance to toxins. In this paper, the principles behind these approaches and the major results on each topic are presented. The benefits of adopting a chemical product engineering approach in conducting this project are also discussed.

Putting Poison into Water: EPA's Toxic Interpretation of Pollutant Under the Clean Water Act

EPA's interpretation exempting certain pesticide applications to and over waters from the definition of in the Clean Water Act, in a December 2006 final rule, is harmful to water quality, and legally impermissible in light of the text, structure, and protective purposes of the Act. This paper provides an overview of the Clean Water Act and the Federal Insecticide, Fungicide, and Rodenticide Act, recent court decisions on the interaction of the two acts, and the rulemaking process that lead to EPA's final rule exempting certain pesticide applications from requiring NPDES permits. The text, structure, and purpose of the Clean Water Act do not allow the interpretation of the term pollutant set out by EPA in its final rule, and the second circumstance of pesticide applications excepted, those over, including near, waters, is not even justified by EPA's own flawed rationale. EPA's reliance on FIFRA in reaching its conclusion that certain pesticide applications are not covered by the Clean Water Act's prohibition on discharges of pollutants is misplaced; not only is FIFRA not adequate for protecting water quality, it is legally irrelevant in interpreting the term pollutant under the CWA. In addition, the pesticide applications at issue are still prohibited by the Refuse Act and regulated by CWA § 401; this further suggests that Congress did not intend for such applications to be exempted from the coverage of the CWA's prohibition on the discharge of pollutants. The paper will endorse the proposals of certain commenters that while the pesticide applications discussed in EPA's final rule should require NPDES permits, the interests of controlling aquatic pests and disease and effective protection of water quality can be balanced through the use of special general permits under the Clean Water Act.