British Columbia Water Quality Guidelines for Dissolved Gas Supersaturation September, 1994 Prepared for BC Ministry of Environment Canada Department of Fisheries and Oceans Environment Canada Prepared by L. E. Fidler and S. B. Miller of Aspen Applied Sciences Ltd. Valemount, BC V0E 2Z0 Table of Contents Acknowledgments The authors wish to acknowledge the assistance of several people and agencies in the preparation of this report. The authors wish to express their appreciation to the BC Ministry of Environment, Lands and Parks for supporting the development of this document and in particular the advice and encouragement of Dr. Narender Nagpal and George Butcher of that agency. The authors also wish to thank Fred Mah of Environment Canada for supporting the development of these guidelines. The many discussions over the years with Dr. Don Alderdice, John Jensen, and Bill McLean of the Department of Fisheries and Oceans, with Dr. Mark Shrimpton and Dr. Dave Randall of the University of British Columbia, and with Dr. John Colt of Montgomery Watson, Bellevue, Washington provided considerable insight into the phenomena associated with Gas Bubble Trauma (GBT) in fish and contributed immensely to the authors' understanding of the subject. In addition, the authors wish to express their appreciation to Ms. Dorit Mason for her efficient retrieval of papers from the scientific literature. The photographs showing signs of GBT in fish, which were supplied by Dr. Robert White of Montana State University, added greatly to this report. Ministry of Environment Water Protection and Sustainability Branch Mailing Address: Telephone: 250 387-9481 Environmental Sustainability PO Box 9362 Facsimile: 250 356-1202 and Strategic Policy Division Stn Prov Govt Website: www.gov.bc.ca/water Victoria BC V8W 9M2 1.0 INTRODUCTION Dissolved Gas Supersaturation (DGS) and Gas Bubble Trauma (GBT) in fish is a physical cause - biological effect relationship which has received the attention of environmental scientists for the past several decades. In British Columbia, DGS has been identified as a potential threat to fish populations in many water courses throughout the province. In this report, DGS is examined in terms of its causes, environmental levels, and potential impacts on fresh water and marine environments. Where sufficient information exists, DGS water quality guidelines are developed for the protection of fresh water and marine life. These guidelines are derived primarily from information describing the adverse physiological effects of DGS on fish and invertebrates. Additional factors, such as environmental variables and organism behavioural patterns which can intensify or mitigate these effects, are considered in the guideline derivation. At this time, no other water uses (i.e., drinking water, agricultural, recreational, or industrial) could be identified which would require guidelines for DGS. The scientific literature upon which this report is based was identified through computer searches of several North American scientific database providers. These included: · ASFA (AQUATIC SCIENCES AND FISHERIES ABSTRACTS): 1978 to January, 1993 · AQUAREF (ENVIRONMENT CANADA): 1970 to March, 1993 · BA (BIOSIS PREVIEWS): 1969 to March, 1993 · CA (AMERICAN CHEMICAL SOCIETY): 1977 to March, 1993 · CAB (CAB ABSTRACTS): 1972 to February, 1993 · ELIAS (ENVIRONMENT CANADA LIBRARY NETWORK): 1976 to September, 1992 · ENVIRO (ENVIROLINE DATABASE): 1971 to January, 1993 · NTIS (NATIONAL TECHNICAL INFORMATION SERVICE): 1964 to March, 1993 · WAVES (ENVIRONMENT CANADA): to March, 1993 In addition, many papers were identified in bibliographies from the primary literature. For example the review of DGS and GBT by Weitkamp and Katz (1980) provided 138 references which were not identified by the computer database searches. This was also true of several other papers (Colt et al. 1986, White et al. 1991). In all, over 380 papers were examined for their suitability for the guideline derivation process. 1.1 Dissolved Gas Supersaturation Dissolved gas supersaturation is a condition which exists in many natural and man- made water bodies throughout the world. It occurs when the partial pressures of atmospheric gases in solution exceed their respective partial pressures in the atmosphere. Figure 1 shows the relationship between gas solubility and temperature for the two major atmospheric gases, oxygen and nitrogen. When dissolved gas concentrations of oxygen and nitrogen are above their respective saturation lines in the figure, they are in a supersaturated state. Conversely, when concentrations of these gases are below the saturation lines, they are under-saturated. Also shown in Figure 1 is the vapour pressure of water as a function of temperature. Water vapour plays an important role in the reporting of dissolved gas levels and in the biological effects of DGS. However, it is generally treated as always being in a saturated state at the prevailing water temperature. Figure 1: Solubility of Oxygen and Nitrogen in Water Individual atmospheric dissolved gases (oxygen, nitrogen, and trace gases such as argon and carbon dioxide) can often be supersaturated without adverse effects on aquatic and marine organisms. However, when the sum of the partial pressures of all dissolved gases exceeds atmospheric pressure, there is the potential for gas bubbles to develop in water and in the aquatic and marine organisms which inhabit the water. This causes a condition known as gas bubble trauma. GBT and its physiological consequences to fish and other organisms will be described more fully in Section 1.2. Throughout the literature, a variety of methods have been used for the reporting of dissolved gas tensions. The sum of the partial pressures of all dissolved gases is referred to as the Total Gas Pressure (TGP), while the difference between TGP and atmospheric pressure is defined as Delta P. Both TGP and Delta P are usually reported in mm Hg (millimetres of mercury) or sometimes in sea level or local atmospheres. Many authors report TGP as a percent of sea level or local atmospheric pressure (TGP%). For reasons which will be presented in Section 4.1, Colt (1984) recommends that delta P, rather than TGP or TGP%, be used as the preferred method of reporting dissolved gas tensions. 1.2 Gas Bubble Trauma Dissolved gas super-saturation can produce a variety of physiological signs which are harmful or fatal to fish and other aquatic and marine organisms (Renfro 1963, Stroud and Nebeker 1976, Weitkamp and Katz 1980, Cornacchia and Colt 1984, Johnson and Katavic 1984, Gray et al. 1985, Fidler 1988, White et al. 1991). As a class, these signs are referred to as gas bubble trauma (Fidler 1984) or gas bubble disease (Bouck 1980). The major signs of GBT which can cause death or high levels of stress in fish are: · Bubble formation in the cardiovascular system, causing blockage of blood flow and death (Jensen 1980, Weitkamp and Katz 1980, Fidler 1988). · Overinflation and possible rupture of the swim bladder in young (or small) fish, leading to death or problems of overbuoyancy (Shirahata 1966, Jensen 1980, Fidler 1988, Shrimpton et al. 1990a and b). · Extracorporeal bubble formation in gill lamella of large fish or in the buccal cavity of small fish, leading to blockage of respiratory water flow and death by asphyxiation (Fidler 1988, Jensen 1988). · Sub-dermal emphysema on body surfaces, including the lining of the mouth. Blistering of the skin of the mouth may also contribute to the blockage of respiratory water flow and death by asphyxiation (Fidler 1988, White et al. 1991). Other signs of GBT include exopthalmia and ocular lesions (Blahm et al. 1975, Bouck 1980, Speare 1990), bubbles in the intestinal tract (Cornacchia and Colt 1984), loss of swimming ability (Schiewe 1974), altered blood chemistry (Newcomb 1976), and reduced growth (Jensen 1988, Krise et al. 1990), all of which may compromise the survival of fish exposed to DGS over extended periods. Each sign of GBT involves the growth of gas bubbles internal and/or external to the animal. However, for each sign there is a threshold level of delta P which must be exceeded before bubble formation or swim bladder overinflation can begin (Fidler 1988, Shrimpton et al. 1990a). Still, the activation of GBT signs is not an easily demonstrated cause and effect relationship. This is because bubbles which develop internal to the animal may form in many body compartments, disrupting neurological, cardiovascular, respiratory, osmoregulatory, and other physiological functions (Stroud and Nebeker 1976, Weitkamp and Katz 1980, Fidler 1988, Shrimpton et al. 1990a and b). Thus, depending on the level of DGS, there may be multiple signs present in affected animals. GBT may also increase the susceptibility of aquatic and marine organisms to other stresses such as bacterial, viral, and fungal infections (Meekin and Turner 1974, Nebeker et al. 1976b, Weitkamp and Katz 1980). All signs of GBT weaken fish, especially juvenile life stages, thereby increasing their susceptibility to predation (White et al. 1991). Consequently, mortality can result from a variety of both direct and indirect effects caused by DGS. Figures 2 through 5 show some of the signs of GBT in rainbow trout exposed to high levels of DGS. Figure 2 shows skin blistering which has occurred in the mouth of an adult rainbow trout while Figure 3 shows sub-dermal emphysema on external surfaces of the head. Figure 4 shows a severe case of exopthalmia in a juvenile trout. Figure 5 is a microphotograph of gill lamella from a fish which has died from GBT. Bubbles in the afferent arteries are clearly visible. Recent research (Fidler 1984 and 1988, Alderdice and Jensen 1985a and b, Colt 1986) suggests that GBT in fish can be divided into acute and chronic responses depending on the levels of DGS. Acute GBT: Acute GBT usually involves delta P levels in excess of 76 mm Hg (Sea Level TGP% about 110%). However, the susceptibility of fish to these levels of DGS is highly dependent on age class or size. For example, Nebeker et al.