Variable survival across low ph gradients in freshwater fish species

Transcription

1 Journal of Fish Biology (2014) 85, doi: /jfb.12497, available online at wileyonlinelibrary.com Variable survival across low ph gradients in freshwater fish species P. G. Jellyman* and J. S. Harding School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand (Received 2 February 2014, Accepted 9 July 2014) A series of 14 day experiments was conducted on five common New Zealand fish species (redfin bully Gobiomorphus huttoni, inanga Galaxias maculatus, brown trout Salmo trutta, longfin eel Anguilla dieffenbachii and koaro Galaxias brevipinnis) to assess the effect of ph on survival and changes in body mass. No species survived in water of ph <4 although there was 100% survival of all adults at ph 4 5, G. maculatus larvae were also tested and had high mortality at this ph. Results suggest that adults are tolerant of low-ph waters; however, successful remediation of anthropogenically acidified streams will require an understanding of the susceptibility to low ph on different life cycle stages The Fisheries Society of the British Isles Key words: experimental ecology; mortality; naturally acidic waters; New Zealand; tolerance. Acidification of fresh waters is widespread owing to the natural leaching of soil acids, pollution resulting in acid rain and human activities such as coal mining (Schindler, 1988; Hogsden & Harding, 2012). Understanding the effect these types of acidification have on freshwater communities can be complex because systems affected by anthropogenic acidity often also have elevated concentrations of bioavailable toxic metals (Petrin et al., 2008). Untangling the separate and interactive effects of stream acidification (i.e. reduced ph) and metal toxicity is critical for the remediation of freshwater environments. Knowing which factors play the most important role in limiting the recovery of riverine communities could greatly improve the chances of successful remediation. For freshwater fish communities, ph can be a major determinant of which species will be present because species vary widely in their tolerance of acidity (West et al., 1997; Mills et al., 2000; Greig et al., 2010). One common remediation strategy has been to treat water so as to improve quality to a level that is suitable for a sub-set of representative species, with the expectation that this will render it acceptable for others as well. Adopting such an approach requires species tolerance values to be measured for *Author to whom correspondence should be addressed at present address: National Institute of Water and Atmospheric Research Ltd., P. O. Box 8602, Christchurch, New Zealand. Tel.: ; phillip.jellyman@niwa.co.nz The Fisheries Society of the British Isles

2 VARIABLE PH TOLERANCE IN FRESHWATER FISHES 1747 representative species and, whilst this can be done in the field, field tolerance values are often confounded in acidified waters by the influence of dissolved metal concentrations and other physico-chemical factors. Moreover, field data are rarely logged continuously so using ph from the day of sampling to determine fish tolerance limits may not reflect the conditions during long-term exposure. Using one-off ph measures increases the risk of over-estimating tolerance limits (or vice versa). For example, if transient migratory species are captured during a field survey, they may skew results because these fishes have not tolerated long-term exposure to water chemistry at a site. Thus, determining accurate fish tolerances to a single factor such as ph is liable to be more robust using an experimental approach. To determine the lower ph tolerance limits for five common New Zealand freshwater fish species (from a region with streams affected by acidified mine leachate), a series of 2 week laboratory experiments was conducted. Acid tolerance experiments were conducted from December 2010 to April Five fish species were exposed to a range of waters with different ph levels. These species were redfin bully Gobiomorphus huttoni (Ogilby 1894), inanga Galaxias maculatus (Jenyns 1842), brown trout Salmo trutta L. 1758, longfin eel Anguilla dieffenbachii Gray 1842 and koaro Galaxias brevipinnis Günther Instead of assessing their survival over a four-day (96 h) period, as per standard ecotoxicology experiments, survival was measured over 14 days. This longer time period was selected because chronic exposure to low ph is relatively common in anthropogenically affected systems and acute 96 h experiments may not accurately reflect whether a species can tolerate longer-term exposure. The water used in each of the five experiments was naturally acidic, brown stream water (ph , 31 2 μs cm 1 ) collected from O Malley Creek (42 09 S; E) on the West Coast, South Island, New Zealand. For each experiment, 1200 l of stream water was transported to a temperature and light cycle-controlled laboratory at the University of Canterbury. The species used were collected from several naturally acidic, brown-water streams (ph range: ) on the west coast because naturally acidic waterways (e.g. as low as ph 4 5) are common in this region and these fishes may be adapted to tolerate more acidic stream water. Fishes were captured by either electrofishing or Gee-minnow trapping, depending on species. Only one fish species was tested during each 14 day experiment. Fish size was controlled to ensure that only juvenile and small adult fishes were used and also of a size that could be held in re-circulating tanks for 2 weeks without ammonium concentrations reaching lethal levels. The size ranges were: G. huttoni (63 74 mm total length, L T, g body mass, M B ), G. maculatus (82 91 mm L T, gm B ), S. trutta (69 82 mm L F, gm B ), G. brevipinnis ( mm L T, gm B ) and A. dieffenbachii ( mm L T,23 77gM B ). Whilst A. dieffenbachii are an order of magnitude heavier than the other fish species, A. dieffenbachii shift from living within substrata to open water only at sizes around 300 mm (Jellyman et al., 2002), so it was important to test eels of approximately this size. Fishes were acclimated in 40 l holding tanks of unmanipulated stream water for 48 h prior to commencing the experiment. The experiment used 30 re-circulating tanks filled with 35 l of stream water. The tanks were split into five ph treatments (ph 3, 3 5, 4, 4 5 and 5 5) and a control (ph c. 6 5), each with five replicates and one fish per replicate. The desired ph level was achieved by adding hydrochloric acid to the stream water; direct acid addition to manipulate ph is the appropriate method given the research objective (Esbaugh et al., 2013). The water was constantly sampled and adjusted during initial ph manipulation and throughout the trials using a laboratory ph

3 1748 P. G. JELLYMAN AND J. S. HARDING meter (Metrohm; All tanks were sealed to prevent fishes escaping and had a flow circulation pump with an external air line fitted that drew in air as the water circulated. Fishes were kept in an 18 C temperature-controlled room with a 12L:12D photoperiod. Fishes were weighed at the start and end of the experiment to determine changes in fish mass in waters of different ph levels. The one exception to this was the A. dieffenbachii experiment where on day 14 (22/2/11) a large earthquake hit Canterbury and the experimental facility could not be accessed for 4 days; all A. dieffenbachii that were alive on the morning of day 14 were still alive after 4 days but they had not been fed for 96 h prior to their final weighing. Tanks were monitored daily to check fish status, food consumption and ph; all treatments became slightly less acidic over a 24 h period (e.g. ph 4 would shift to after 24 h) so ph was sampled and adjusted each morning. In addition, temperature, dissolved oxygen, conductivity and ammonium concentration were also measured daily. If ammonium concentration in the tanks was >1mgl 1, then 1 10 ml of Stress Zyme ( (i.e. a biological filter) was added which decreased ammonium levels without altering ph. All fishes were fed 1 8 g of commercial frozen blood worms Chironomus spp. each afternoon, with any uneaten bloodworms cleaned from the tank the following morning to reduce waste product build-up. As the susceptibility of larval fishes to ph may differ from that of juvenile or adult fishes, larval fish ph tolerance was also tested. Owing to life-history timing issues and difficulties in locating the fish eggs from which to hatch larvae, only G. maculatus larvae could be tested. Galaxias maculatus were collected as eggs (from adult fish site) and were hatched in the laboratory; larvae size was c. 7 mm. Forty-eight hours after hatching, larvae were placed into aerated 2 l containers. As per the trial for juvenile and adult fishes, 30 containers were used and the same ph treatments were applied. The major differences were that this experiment lasted only 96 h (as larvae were not fed) and that five larvae were placed in each container instead of only a single fish. To examine whether temperature, dissolved oxygen, conductivity or ammonium concentration differed over time and between trials, one and two-way analysis of variance (ANOVA) was performed using the R statistical package ( To determine lethal concentration (LC 50 ) and lethal time (LT 50 ) estimates for each species, fish mortality data were fitted using four parameter logistic curves in Sigmaplot (version 12.5; One-way ANOVA was conducted for each species to determine whether the change in mass during the experiment differed significantly between ph treatments. Post hoc Tukey tests were then conducted in the R statistical package to assess which ph treatments had significantly different changes in mass. A P-value of <0 05 was considered significant for all tests. Mean temperature, dissolved oxygen, conductivity and ammonium concentration did not differ significantly among experiments (ANOVA, P > 0 05; for all factors). There were significant increases over time for both dissolved oxygen (time: ANOVA, F 1,55 = 33 0, P < 0 001) and ammonium concentration (time: ANOVA, F 1,55 = 58 2, P < 0 001) but there was no significant difference between species over time for either variable (time species interaction, ANOVA, F 4,55 < 1 0, P > 0 05; for both variables). No fish species survived exposure at ph 3 or 3 5, but after 14 days all juvenile and adult fishes had 100% survival at ph 4 5 (Fig. 1). Adult S. trutta, G. huttoni and G. brevipinnis experienced some or complete mortality at ph 4, whereas all adult G. maculatus and A. dieffenbachii survived at this ph. The LC 50 estimates ranged from 3 74 to 4 24 for these juvenile and adult fishes (Fig. 1). Estimates of LT 50 varied markedly

4 VARIABLE PH TOLERANCE IN FRESHWATER FISHES 1749 (a) (c) (e) Mortality (%) after 14 days Mortality (%) after 14 days Mortality (%) after 14 days ph (b) (d) (f) ph 6 7 Fig. 1. Effect of water of different ph on the mortality of (a) Salmo trutta [lethal concentration (LC 50 ) = 3 99], (b) Gobiomorphus huttoni (LC 50 = 4 24), (c) Galaxias brevipinnis (LC 50 = 3 97), (d) Anguilla dieffenbachii (LC 50 = 3 74), (e) Galaxias maculatus (LC 50 = 3 74) after 14 days. (f) G. maculatus larvae (LC 50 = 4 72) after 4 days. Individual data points represent mean per cent mortality (n = 5) but for G. maculatus larvae, each replicate contained five larvae so error bars were calculated for this 96 h experiment. for each fish species (Table I). Whilst there was 100% mortality at ph 3 5, G. huttoni and S. trutta had an LT 50 of c. 2 6 and 3 1 h (respectively), whereas G. maculatus and G. brevipinnis had LT 50 estimates of 11 9 and 13 0 h, respectively (Table I). In contrast to adult G. maculatus, all G. maculatus larvae died at ph 4 and >75% of G. maculatus larvae died at ph 4 5 resulting in a 96 h LC 50 estimate of 4 72 (Fig. 1). Although high mortality of G. maculatus larvae occurred at ph 4 5, the LT 50 was 72 h and it took 2 days until the first larvae died indicating that they can withstand that ph for short periods (Table I).

5 1750 P. G. JELLYMAN AND J. S. HARDING Table I. Time estimates (h) for 50% fish mortality (LT 50 ) in waters of varying ph. Data for ph 6 5 are not shown as they are identical to data for ph 5 5 for all species Species ph 3 ph 3 5 ph4 ph4 5 ph5 5 Salmo trutta >336 >336 >336 Gobiomorphus huttoni >336 >336 Galaxias brevipinnis >336 >336 >336 Anguilla dieffenbachii >336 >336 >336 Galaxias maculatus >336 >336 >336 Galaxias maculatus (larvae) * >96 *Probable significant over-estimation as larvae were observed after 1 and then after 12 h. At the end of the 14 day experiments, the percentage change in mass observed for G. maculatus, G. huttoni and A. dieffenbachii were not significantly different across the various ph treatments (ANOVA, P > 0 05; for these species) (Table II). Although G. maculatus and G. huttoni gained mass across ph treatments, A. dieffenbachii lost mass across all these ph treatments. A loss of mass in A. dieffenbachii may be partially explained by a lack of feeding for the 4 days prior to their final weighing. Significant percentage changes in mass across the ph treatments were observed for S. trutta (F 3,16 = 27 0, P < 0 001) and G. brevipinnis (F 3,16 = 8 0, P < 0 01). For S. trutta, the loss of mass in the ph 4 treatment was significantly different from fish mass gains in the ph treatments (Table II). The mean percentage change in mass for G. brevipinnis in the ph 4 treatment was 0 3% which was significantly less than the mass gains observed in the ph 4 5 and 5 5 treatments (Table II). Extremes of ph can be a major factor determining abundance and composition of fish communities in lakes and streams (Hesthagen et al., 1999; Greig et al., 2010). The effect of low ph on aquatic biota can differ markedly depending on whether the acidity is natural due to organic acids (ph usually >4) or the result of human impacts (ph <3 5) (Petrin et al., 2008; Greig et al., 2010). This study revealed that no species would survive in the highly acidic waters (ph 3 3 5) of streams affected by mining activities in New Zealand. Instead, the five species tolerated ph more characteristic of naturally acidic water, with all juvenile and adult fishes surviving a two-week exposure Table II. Mean ± s.e. change in percentage fish mass (based on initial wet masses) for the waters of varying ph. Due to rapid mortality in the ph 3 and 3 5 treatments (and ph 4 for Gobiomorphus huttoni), no changes in mass were recorded. Superscript lowercase letters denote significant mass differences between ph treatments as indicated by analysis of variance (ANOVA) followed by post hoc Tukey tests. Sample size for ph 4 varied based on fish mortality (see Fig. 1), n = 5 for ph 4 5 Species ph 4 ph 4 5 ph5 5 ph6 5 Salmo trutta 18 0 ± 2 6 a 6 7 ± 1 7 b 10 6 ± 3 1 b 12 4 ± 1 8 b Gobiomorphus huttoni 15 3 ± ± ± 6 5 Galaxias brevipinnis 0 3 ± 3 8 a 24 3 ± 2 0 b 18 2 ± 2 7 b 12 7 ± 5 2 ab Anguilla dieffenbachii 7 2 ± ± ± ± 1 2 Galaxias maculatus 9 9 ± ± ± ± 3 1

6 VARIABLE PH TOLERANCE IN FRESHWATER FISHES 1751 to ph 4 5. Whilst some species were able to survive, or even gain mass, in water of ph 4 after 2 weeks, medium to long-term survival in water of this acidity would appear to be unlikely for most species given the range of ph waters they are known to occupy (Greig et al., 2010). Had the experiment been conducted using a standard 96 h ecotoxicology approach, the effect of ph 4 water would have appeared markedly different, since two species had 100% survival after 96 h but started to die after a week or so. This study suggests that a ph of at least 4 5 is required for optimal fish survival. This corroborates the field survey findings of Greig et al. (2010), which suggested that ph should be raised above 4 5 to remediate fish communities in naturally acidic, mine-affected streams (in combination with reducing concentrations of dissolved metals). Some species may tolerate lower-ph waters if they are slowly acclimated (Trojnar, 1977) but acclimation does not always improve fish survival in low-ph waters (Audet & Wood, 1988). The survival of <25% of larval G. maculatus at ph 4 5 compared with 100% survival of adults at ph 4 is consistent with previous studies that have suggested that ph sensitivity is highest in early life stages (Fromm, 1980). Mass fish mortalities and extinctions have occurred in countries that have experienced gradual acidification of lakes and rivers during the 20th century (e.g. Sweden, Norway, Canada and the U.S.A.), and the common mechanism has been recruitment failure due to high mortality in early life cycle stages (i.e. eggs, alevins and smolt) (Gjedrem & Rosseland, 2012). From a fisheries perspective, determining an appropriate ph for stream remediation will depend on whether a waterway is suitable for fish spawning and larval rearing or whether the stream habitat is suitable only for juvenile and adult fishes. Since early life stages are generally more sensitive to acidification than larger fishes (Rosseland et al., 2001), the ph needed to restore fish communities may vary depending on whether larvae migrate out to sea or if they develop entirely in fresh water. Prior to any remediation of stream ph, the acidity inherent to the system should be considered because it may be detrimental to try and restore an affected stream to circum-neutral ph when the fish communities are adapted to live in naturally acidic waters. M. Marinov is thanked for assistance with fish collection and H. Stoddart provided laboratory support. Experiments were performed under the University of Canterbury animal ethics permit number 2009/2R. This research was funded by the Foundation for Research Science & Technology (contract CRLX0401) with funding to P.G.J. from NIWA Core Funding (project SA125085) assisting with manuscript preparation. References Audet, C. & Wood, C. M. (1988). Do rainbow trout (Salmo gairdneri) acclimate to low ph? Canadian Journal of Fisheries and Aquatic Sciences 45, Esbaugh, A. J., Mager, E. M., Brix, K. V., Santore, R. & Grosell, M. (2013). Implications of ph manipulation methods for metal toxicity: not all acidic environments are created equal. Aquatic Toxicology , Fromm, P. O. (1980). Review of some physiological and toxicological responses of freshwater fishtoacidstress.environmental Biology of Fishes 5, Gjedrem, T. & Rosseland, B. O. (2012). Genetic variation for tolerance to acidic water in salmonids. Journal of Fish Biology 80, Greig, H. S., Niyogi, D. K., Hogsden, K. L., Jellyman, P. G. & Harding, J. S. (2010). Heavy metals: confounding factors in the response of New Zealand freshwater fish assemblages to natural and anthropogenic acidity. Science of the Total Environment 408, Hesthagen, T., Sevaldrud, I. H. & Berger, H. M. (1999). Assessment of damage to fish population in Norwegian lakes due to acidification. Ambio 28,

7 1752 P. G. JELLYMAN AND J. S. HARDING Hogsden, K. L. & Harding, J. S. (2012). Consequences of acid mine drainage for the structure and function of benthic stream communities: a review. Freshwater Science 31, Jellyman, D. J., Bonnett, M. L., Sykes, J. R. E. & Johnstone, P. (2002). Contrasting use of daytime habitat by two species of freshwater eel Anguilla spp. in New Zealand rivers. In Biology, Management, and Protection of Catadromous Eels (Dixon, D. A., ed.), pp Bethesda, MD: American Fisheries Society. Mills, K. H., Chalanchuk, S. M. & Allan, D. J. (2000). Recovery of fish populations in Lake 223 from experimental acidification. Canadian Journal of Fisheries and Aquatic Sciences 57, Petrin, Z., Englund, G. & Malmqvist, B. (2008). Contrasting effects of anthropogenic and natural acidity in streams: a meta-analysis. Proceedings of the Royal Society B 275, Rosseland, B. O., Kroglund, F., Staurnes, M., Hindar, K. & Kvellestad, A. (2001). Tolerance to acid water among strains and life stages of Atlantic salmon (Salmo salar L.). Water, Air, and Soil Pollution 130, Schindler, D. W. (1988). Effects of acid rain on freshwater ecosystems. Science 239, Trojnar, J. R. (1977). Egg hatchability and tolerance of brook trout (Salvelinus fontinalis) fry at low ph. Journal of the Fisheries Research Board of Canada 34, West, D. W., Boubee, J. A. T., Barrier, R. F. G. (1997). Responses to ph of nine fishes and one shrimp native to New Zealand freshwaters. New Zealand Journal of Marine and Freshwater Research 31,