Brenda M. Miskimmin, William E Donahue, Dainna Watson. University of Alberta, Department of Biological Sciences, Biological Sciences Building, Edmon-.
Aquatic Sciences 57/1, 1995
1015-1621/010020-11 $1.50 + 0.20/0 © 1995 Birkh~iuser Verlag, Basel
Invertebrate community response to experimental lime (Ca(OH)2) treatment of an eutrophic pond B r e n d a M. Miskimmin, William E D o n a h u e , D a i n n a W a t s o n University of Alberta, Department of Biological Sciences, Biological Sciences Building, Edmonton, Alberta, Canada, T6G 2E9
Key words:Lime, calcium hydroxide, p H shock, habitat loss, m a c r o p h y t e s .
ABSTRACT Calcium hydroxide (Ca(OH)2), or hydrated lime, has recently been reintroduced in western Canada as a treatment to reduce macrophytes and algae in eutrophic waters. We examined the effects and recovery of aquatic invertebrates of the Ca(OH)2 treatment (250 mg L -z) of one half of a divided eutrophic pond compared to the untreated half. Nine weeks following treatment, total invertebrates on the untreated side were present at 1917 + 555 individuals m -z, and on the treated side at 822 + 186 individuals m -2. Notably, Chironomidae represented 13 % of invertebrates on the untreated half, but dominated numerically with 72 % on the treated half of the pond. The remaining five most abundant taxa in the untreated side were 88 % - 99 % less abundant in the treated half of the pond. Diversity and evenness were twice as high for the untreated half as for the treated half of the pond. Because macrophytes were also extirpated with the Ca(OH)2 treatment, macrophyteassociated taxa were absent or at low numbers in the treated half. The death of organisms on the treated side of the pond may have been caused (directly or indirectly) by the pH shock associated with Ca (OH)2 treatments. Slow recolonization by most invertebrates during the year of treatment was probably due to the lack of heterogeneous macrophyte habitat. Follow-up sampling 3 years later indicated that the pond completely regained the abundance and biological diversity of flora and fauna.
Introduction L i m e in the forms of C a ( O H ) 2 and C a C O 3 have historically b e e n used to increase the alkalinity and p H of acidified lakes (Hasler et al., 1951; Scheider and Dillon, 1976; Bengtsson et al., 1980; Driscoll et al., 1982). C a C O 3 was f o u n d by m o s t to be m o r e effective and to have longer lasting effects than C a ( O H ) 2 and also not to cause a rapid rise in p H ( " p H shock") within lake ecosystems (Driscoll et al., 1982; Kretser and C o l q u h o u n , 1984; Weatherley, 1988). O t h e r s have f o u n d that alkalinity, calcium and b i c a r b o n a t e have r e m a i n e d high for years in a software lake t r e a t e d with C a ( O H ) 2 (Elser et al., 1986). In the past few years, C a ( O H ) 2 has b e e n experimentally a d d e d to a variety of h a r d w a t e r lakes and p o n d s in western C a n a d a to r e d u c e m a c r o p h y t e s and algae
Invertebrate response to lime (Ca(OH)2) treatment
21
(Murphy and Prepas, 1990; Prepas et al., 1990; Babin et al., 1992; Murphy et al., 1993). The effects on the plant communities and lake chemistry were studied (Prepas et al., 1992; Babin et al., 1994); however, reports on the effects on fauna have been limited. The desired effect of reducing primary producers is generally temporary (e.g. Prepas et al., 1992), perhaps because nutrients are not removed from the systems. The reasons have yet to be determined experimentally. Studies of the response of invertebrates to hydrated lime applications in eutrophic, high pH systems have been inconclusive. Leeches were temporarily controlled in localized areas with high daily applications of 45 kg m 2 of powdered lime (Pennak, 1989). Toxicity to chironomids and chaoborids at 100 mg g -1 Ca(OH)2 in combination with a herbicide (trifluralin) was reported by Snyder (1990). While the organisms on the herbicide-only half of a pond were unaffected, synergistic effects could not be discounted on the herbicide-lime treated side. One review paper reported that invertebrates in ponds were observed to be killed by Ca(OH)2 treatments at concentrations similar to those applied by Prepas et al. (1992) to the pond we report on here (not quantified; Murphy et al., 1993). In another case, while no detectable impact on invertebrates was suggested for Ca(OH)2 treatments to a hypereutrophic lake (Prepas et al., 1990), supporting data were absent. For other eutrophic lakes that received lower doses of Ca(OH)2, an investigation of the effects on Chironomidae and Chaoboridae is in progress (K. Yee, pers. commun.). On the other hand, effects on invertebrates were quantified for some softwater lakes that were treated with lime to alleviate acidification. A pH excursion from 4.5 to 7.5 created by Ca(OH)2 additions caused an immediate decline in the standing stock of phytoplankton, zooplankton and zoobenthos in two softwater lakes in eastern Canada (Scheider and Dillon, 1976). Phytoplankton increased the year following treatment, but zooplankton and zoobenthos failed to recover to pretreatment levels for two years, and the long-term recovery was partially augmented by fertilization of the lakes. Macrophyte removal in the absence of a pH excursion is also known to affect invertebrates negatively. Loss of habitat by mechanical removal of macrophytes was considered the cause of the decline of invertebrates and other organisms in rivers (Murphy and Eaton, 1981), wetlands (Newbold, 1981) and lakes (Bryan, 1975). Whether invertebrates are removed by mechanical means, by pH shock or for other reasons, their recovery is inherently dependent upon the recuperation of their habitat. The response and recovery of invertebrate communities following Ca(OH)2 treatment has not previously been examined in detail, particularly in naturally eutrophic systems that typically have a natural pH greater than 8. The objective of this study was to determine the response and recovery of benthic invertebrates to the Ca(OH)2 treatment of a hardwater pond. Such fundamental studies are critical because of the revival of interest in the use of Ca(OH)2 in the management of eutrophic waters.
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Miskimmin,Donahue and Watson
Materials and methods
Study site and lime application Helbig Pond (53°11'N 114°23'W) is a high pH (8-9.5) prairie pond of moderate alkalinity (3.5 + 1.2 meq L -1) located in central Alberta, Canada. The pond has an area of 1720 m 2 and a maximum depth of 1.8 m. Helbig Pond was one of many naturally eutrophic water bodies in Alberta that were treated by Prepas et al. (1992) to determine the effectiveness of lime for controlling macrophytes and algae. The pond was partitioned in half with a polyethylene sea curtain in July 1990, three weeks prior to treating one side with 250 mg L -1 of hydrated lime, Ca(OH)2. This gave an approximate areal coverage of 35 mg cm -2 on the treated half. A slurry of hydrated lime mixed with water was sprayed over the pond surface from a "slurrymaker" that was mounted on a trailer (Murphy et al., 1990). The pH and alkalinity of the pond just prior to treatment were 8.9 and 2.4 meq L-1, respectively. The pH was not measured immediately after treatment, but 9 days later it was 9.5 and alkalinity was 1.7 meq L -a (Prepas et al., 1992). In other cases, the pH of similar small ponds has been elevated to 10.5 (Murphy et al., 1990) or more (up to 12.1, Prepas et al., 1992) when measured a few days after application of comparable doses of Ca(OH)2. Macrophytes were effectively killed on the lime treated half of the pond, while abundant macrophytes remained on the untreated half (Prepas et al., 1992). Open water chlorophyll a concentrations were reduced on the treated half relative to the untreated half for 3 weeks (Prepas et al., 1992). The partitioning curtain was removed from the pond in late September 1990, at which time few macrophytes had yet regrown on the treated side.
Sample collection Triplicate samples for benthic invertebrates from each of the treated and untreated sides of the pond were collected three weeks after the curtain was removed (October 1990; 9 weeks after treatment), Samples were collected again from both sides of the pond in August 1993 to examine the extent of recovery of the invertebrate community three years after treatment. Each sample represented invertebrates collected with a dipnet (mesh size 0.5 mm) within pre-marked 1.0 m 2 quadrats. The dipnet was swept through the macrophytes and sediments for about 5 minutes within each quadrat. Some macrophytes were incidentally collected along with invertebrates. These were removed for qualitative identification. Samples of invertebrates were preserved in 80% ethanol on site and returned to the laboratory for sorting and enumeration. Invertebrates were sorted using a range of sieve sizes and were handpicked and identified using a key to aquatic invertebrates of Alberta (Clifford, 1991). Results are reported as the number of organisms per m -2, from which Simpson's dominance index (D) as well as Bulla's evenness and diversity (Bulla, 1994) were calculated. Bulla's indices differ from Simpson's in heavily weighting rare species rather than favouring more abundant species. Taxa were further numerically combined according to their
23
Invertebrate response to lime (Ca(OH)2) treatment
Table 1. List of Taxa found in sampies from Helbig Pond in either of Treated, Untreated or Recovery (3 yrs later) collections. ABBR. = abbreviation used in Figs. 1 and 2; ASSOCIATION = preferred habitat used in Fig. 3: The first habitat listed in the one preferred by the taxon, i.e. Water indicates migration potential, Macro indicates more sedentary macrophyte association, Seds indicates living on or in sediments. (Association in brackets in secondary, not used for Fig. 3) Major taxon
Family
Identification
Abbr.
Association
Amphipoda
Gammaridae Talitridae Dytiscidae
Gammarus lacustris Hyalella azteca Agabus sp. Colymbetes sp. Hydroporus sp. Ilybius sp. Laccophilus sp, Liodessus sp. HaIiplus sp. Peltodytes sp.
AMP AMP DYT DYT DYT DYT DYT DYT HAL HAL CER CHA CHI TAN BAE BAE BAE CAE
Water (Macro) Water (Macro) Water (Macro) Water (Macro) Water (Macro) Water (Macro) Water (Macro) Water (Macro) Macro (Water) Macro (Water) Water (Seds) Water (Seds) Seds (Macro) Seds (Macro) Water (Macro) Water (Macro) Water (Macro) Seds (Macro) Macro (Seds) Macro (Seds) Macro (Seds) Macro (Seds) Macro (Seds) Macro (Seds) Macro (Seds) Macro (Seds) Macro (Seds) Macro (Seds) Macro (Seds) Macro (Seds) Water (Macro) Water (Macro) Water (Macro) Water (Macro) Seds (Macro) Seds (Macro) Seds (Macro) Macro (Water) Seds Macro (Sed) Macro (Water) Macro (Water) Macro (Water) Macro (Water) Macro (Seds) Seds Macro (Seds)
Coleoptera
Halipliidae Diptera
Ceratopogonidae Chaoboridae Chironomidae
Ephemeroptera
Baetidae
Gastropoda
Caenidae Heptageniidae Hydrobiidae Lymnaeidae Physidae Planorbidae
Hemiptera Hirudinea
Valvatidae Corixidae Notonectidae Erpobdellidae Glossiphoniidae
Hydrachnidia Nematoda Zygoptera Anisoptera Oligochaeta Pelecypoda Trichoptera
Coenagrionidae Lestidae Corduliidae Libellulidae Lumbriculidae Sphaeriidae Phryganeidae
Ceratopogoninae Chaoborus sp. Chironominae Tanypodinae Catlibaetis sp. Centropti!um sp. Cloeon sp. Caenis sp. -
Amnicola limosa ProbythineUa sp. Bakerlymnaea sp. Fossaria sp. Stagnicola sp. Aplexa sp. Physa sp. Armiger crista Gyraulus sp. Promenetus sp. Vatvata sp. Hesperocorixa sp. Notonecta sp. Dina sp. Nephelopsis obscura Glossiphonia complanata Helobdella stagnalis Theromyzon sp. Hydracarina Lestes sp.
PHY ARM GYR PRO CRX NOT
HYD NEM ZYG ZYG
Sornatochlora sp. Leucorrhinia sp. Sympetrum sp. -
Pisidium sp. Phryganea sp.
LUM PIS
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Miskimmin, Donahue and Watson
preferred habitat association (see Table 1; using Ward, 1992; Clifford, 1991 or Pennak, 1978), and the fractions of invertebrates associated with macrophytes, sediments and the water column were c o m p a r e d between the treated and untreated halves. Significant differences between sites in abundances and diversity variables were assessed by analysis of variance.
Results
Abundances during year of lime application A t least twenty-eight families of benthic invertebrates were represented in Helbig Pond (Table 1, includes samples taken 3 years later). Nine weeks after treatment, invertebrate abundances were 1917 _+555 m -2 on the untreated and 822 + 186 m -2 on the treated side. The Bulla evenness and diversity values were also significantly higher (P < 0.01) for the untreated side of the p o n d than for the limed side (Table 2). Simpson's dominance index was 3.5 times higher for the limed side (Table 2), clearly because of the dominance of chironomids nine weeks after treatment (Figure 1). Nine taxa were present at abundances greater than 50 m -2 in the untreated side, with no one taxon dominating numerically (Figure 1). By comparison, the lime treated side of the p o n d had two taxa numbering m o r e than 50 m -2, with an overwhelming numerical dominance of the Chironomidae (589+ 85 m-2; Figure 1). Chironomidae overall represented 13 % of invertebrates in the untreated half and 72% in the treated half. The remaining five most abundant taxa in the untreated side were on average 88 % - 99 % less abundant in the treated half of the p o n d (Figure 1). Aside from Chironomidae, of the 11 taxa that numerically represented m o r e than 1% of samples, 5 were significantly less abundant on the treated side (P_O.05).
Abundances three years after treatment Both halves of the pond had similar types, abundances and diversities of invertebrates when sampled three years after Ca(OH)2 treatment. No significant differ-
Table 2. Abundance, diversity, evenness (Bulla 1994) and Simpson's dominance (Washington 1984) values from each half of Helbig Pond, both nine weeks and three years following treatment of one half with hydrated lime. Values are means + 1 SD of triplicate samples 9 weeks after treatment Unlimed Limed
3 years after treatment Unlimed Limed
No. of Taxa Total organisms
17_+4 1917 + 555
14___2 822 + 186
22+3 953_+529
23_+1 1687 +_288
Evenness Diversity Dominance
0.452__+0.040 7.6 + 1.3 0.154 + 0.02
0.253 + 0.227 3.6 + 0.5 0.542 + 0.06
0.361 + 0.095 7.9 + 1.8 0.228 + 0.11
0.407 + 0.008 9.2 + 0.1 0.185 + 0.03
Invertebrate response to lime (Ca(OH)~) treatment
25
700 -
9 wee]cs after treatment 600 ]
500 -
E
~
400
O. (~
[--] 300-
Untreated Treated
Z 200 J
10o o.J
Taxon
Figure 1. Year of Treatment: 16 most abundant invertebrate taxa in Helbig Pond 9 weeks following Ca(OH)2 treatment to one half. Values are means _+1 SD of three samples taken on each side of the pond. Abbreviations for taxa are listed in Table 1
800
•
3 years after treatment 700 -
t
e,,I
I Untreated Treated
E 500 -
~
400 500 -
Z
200 100
0.05, Figure 2). T a n y p o d i n a e w e r e not a n u m e r i c a l l y major taxon, but w e r e m o r e abundant on the treated half 3 years later ( P < 0.05). D i v e r s i t y values did n o t differ b e t w e e n the treated and untreated sides (Table 2). M a c r o p h y t e s w e r e abundant t h r o u g h o u t the p o n d and included Myriophyllum exalbescens (water milfoil), Ceratophyllum demersum and Potomogeton spp.
26
Miskimmin, Donahue and Watson lOO 80
9 weeks after treatment
F-q
60
40
"~ 20 >
0;
_z
3 years after treatment
a0 z r~ la.l
60
o. 40 20 0
-WATER
MACROPHYTES SEDIMENTS
Figure 3. Mean percent (+ 1SD) of invertebrates grouped according to habitat association (see Table 1) with either water (i.e. good swimmers), macrophytes or sediments in Hetbig Pond. Upper panel is samples taken 9 weeks following Ca(OH)2 treatment to one side; lower panel is recovery phase (all bars show mean +ISD of three samples). ++ significant (P
