Reproductive Impairment of the Crayfish Orconectes virilis in Response to Acidification of Lake 223

1987 ◽  
Vol 44 (S1) ◽  
pp. s97-s106 ◽  
Author(s):  
Robert L. France
Keyword(s):  
Egg Production ◽  
Lake Acidification ◽  
Orconectes Virilis ◽  
Experimental Lakes Area ◽  
Rate Of Development ◽  
Northwestern Ontario ◽  
Reproductive Impairment ◽  
Cement Compound ◽  
Acidification Of Lake ◽  
Egg Capsule

Reproductive characteristics of crayfish (Orconectes virilis) were examined during 1979–81 in four small Canadian Shield basins in the Experimental Lakes Area, northwestern Ontario. One of these lakes, Lake 223 (L223), has been experimentally acidified since 1976. Egg resorption, fertilization, and rate of development were not seriously affected by lake acidification to pH 5.1. Incomplete hardening of the glair–cement compound forming the egg capsule membrane and stalk resulted in a loss of eggs from the pleopods, causing the L223 population to suffer decreased reproduction. On an egg production basis, the reproductive impairment (defined as the % decrease in number of viable eggs prior to hatching) in reference populations averaged 3.2 ± 1.8 (95% C.I.) compared to levels of 18.7, 36.2, and 29.4% during 1979–81 in L223 at pH 5.2–5.6. Direct mortality of eggs accounted for little of the reduced natality in the L223 population and did not occur in reference lakes. Loss of crayfish populations exposed to lake acidification will probably result from reproductive failure before lake water becomes acid enough to be directly toxic to mature crayfish.

Population Collapse of the Crayfish Orconectes virilis in Response to Experimental Whole-Lake Acidification

1989 ◽  
Vol 46 (6) ◽  
pp. 910-922 ◽  
Author(s):  
I. J. Davies
Keyword(s):  
Population Size ◽  
Population Decline ◽  
Fish Predation ◽  
Reference Population ◽  
Lake Acidification ◽  
Orconectes Virilis ◽  
Microsporidian Parasite ◽  
Experimental Lakes Area ◽  
Recruitment Failure ◽  
Northwestern Ontario

A population of Orconectes virilis in Lake 223 at the Experimental Lakes Area, northwestern Ontario, was monitored from 1976 to 1982 during an acidification experiment. O. virilis from nearby Lake 240 served as a reference population. Crayfish abundance remained stable as average epilimnion pH was gradually lowered from 6.49 (1976) to 5.93 (1978). In 1979 (pH 5.64) recruitment of young was poor and the overall population size [Formula: see text] fell from 105 800 to 60 300 animals. The decline continued in the complete absence of recruitment during 1980 (pH 5.59, [Formula: see text] and 1981 (pH 5.02, [Formula: see text]. Few crayfish survived until the spring of 1982. None were present from mid-summer 1982 to fall 1983 (average pH 5.09 to 5.13). Hatchling mortality and some egg loss appeared to have been the causes of recruitment failure. Acidification also produced a noticeable softening in the carapace of all intermoult crayfish. Growth, mortality, behaviour, and the basic reproductive functions of juvenile and adult crayfish did not change in response to acidification. Fish predation and the incidence of a microsporidian parasite apparently contributed little to the population decline.

Decreased Survival and Calcium Uptake by the Crayfish Orconectes virilis in Low pH

1980 ◽  
Vol 37 (3) ◽  
pp. 364-372 ◽  
Author(s):  
D. F. Malley
Keyword(s):  
Acid Rain ◽  
Lake Water ◽  
Calcium Uptake ◽  
Physiological Responses ◽  
Low Ph ◽  
Lake Acidification ◽  
Orconectes Virilis ◽  
Molt Cycle ◽  
Experimental Lakes Area ◽  
Acidification Of Lake

As part of a study of the effects of the experimental whole-lake acidification of Lake 223 in the Experimental Lakes Area on the population of the crayfish Orconectes virilis physiological responses of adults from this population to low pH were examined in the laboratory. Crayfish survived pH 4.0 for 10 d when they were not moulting but suffered mortality when they were in postmolt stages. Postmolt crayfish held at pH 5.0 for 10 d survived but showed slower progression of molt cycle stages and of calcification of the exoskeleton than individuals held at pH 6.0 or in lake water at about pH 6.7. Uptake of Ca++ by postmolt crayfish measured by the use of 45Ca as a tracer was inhibited by pH below 5.75 and ceased altogether below pH 4.0 when these levels of acidity were applied acutely.Key words: Orconectes virilis, crayfish, molt cycle, mortality, pH, calcification, postmolt calcium uptake, acid rain, lake acidification

Relationship of Crayfish (Orconectes virilis) Growth to Population Abundance and System Productivity in Small Oligotrophic Lakes in the Experimental Lakes Area, Northwestern Ontario

1985 ◽  
Vol 42 (6) ◽  
pp. 1096-1102 ◽  
Author(s):  
R. L. France
Keyword(s):  
Sexual Maturity ◽  
Egg Production ◽  
Maximum Size ◽  
Reproductive Capacity ◽  
Phytoplankton Production ◽  
Orconectes Virilis ◽  
Experimental Lakes Area ◽  
System Productivity ◽  
Frequency Distributions ◽  
Northwestern Ontario

Crayfish growth in four lakes in the Experimental Lakes Area (ELA) was examined by analysis of size-frequency distributions, molt increment data, and calculation of instantaneous growth and mean size at onset of sexual maturity. Orconectes virilis growth rates at ELA are only 27–38% of those reported for other areas. Growth varied both among study lakes and between years. Higher temperatures and a longer growing season during 1980 increased growth an average of 12% over that of the preceding year. Crayfish growth and maximum size in four to six lakes were significantly correlated with phytoplankton production and chlorophyll a concentration. Growth regulated both the number of age 1 animals attaining sexual maturity and the per capita egg production, and was also directly related to the proportion of mature females that were fertilized. I believe population regulation is mediated through alterations in reproductive capacity that is correlated with system productivity.

Decline of Mysis relicta During the Acidification of Lake 223

1983 ◽  
Vol 40 (11) ◽  
pp. 1905-1911 ◽  
Author(s):  
R. W. Nero ◽  
D. W. Schindler
Keyword(s):  
Confidence Limits ◽  
Experimental Lakes Area ◽  
Mysis Relicta ◽  
Ph Values ◽  
Northwestern Ontario ◽  
Population Comparisons ◽  
Acidification Of Lake ◽  
Ph Range ◽  
Shield Lakes ◽  
Direct Toxicity

The population size of Mysis relicta in Lake 223 of the Experimental Lakes Area, northwestern Ontario, decreased from 6 700 000 ± 1 330 000 (± 95% confidence limits) during August of 1978, to 270 000 ± 75 000 during August of 1979, a 96% decrease. Because Mysis, a cold stenotherm, is restricted to the metalimnion and hypolimnion of lakes during summer, the pH range encountered by the population was 5.51 to 6.32 in 1978 and 5.23 to 6.10 in 1979, even though mean pH values in epilimnion waters for the 2 yr were 5.84 and 5.60. A decrease in pH of its habitat from 6.2 to 5.6 during fall overturn in 1979 caused the elimination of the remaining 4% of the population. Comparisons with four control lakes suggested that the decline and disappearance were not normal occurrences in unstressed lakes. Concentrations of Zn, Al, Mn, Fe, Cd, Cu, Ni, and Hg in Lake 223 water were low, and concentrations in Mysis were less than or equal to those in animals from five control lakes, suggesting that the decline in this species was not due to the toxic effects of metals. All size classes were affected, so that direct toxicity of hydrogen ion may be responsible for this abrupt population collapse. These results suggest that Mysis may be a useful early indicator of acidification damage to Precambrian Shield lakes.

Measurements of Specific Rates of Net Methyl Mercury Production in the Water Column and Surface Sediments of Acidified and Circumneutral Lakes

1987 ◽  
Vol 44 (4) ◽  
pp. 750-757 ◽  
Author(s):  
Luying Xun ◽  
N. E. R. Campbell ◽  
John W. M. Rudd
Keyword(s):  
Water Column ◽  
Water Samples ◽  
Methyl Mercury ◽  
Lake Acidification ◽  
Sediment Surface ◽  
Mercury Methylation ◽  
Experimental Lakes Area ◽  
Northwestern Ontario ◽  
Decreasing Ph ◽  
Mercury Production

Specific rates of mercury methylation and demethylation were determined for water and surficial sediment samples taken from several lakes located in the Experimental Lakes Area, northwestern Ontario. Specific rates of mercury methylation were found to increase with decreasing pH in epilimnetic water samples in which pH was adjusted prior to incubation and in epilimnetic water samples taken from lakes of different pH. Reduction of pH also increased methyl mercury production at the sediment surface. Both increases and decreases in pH reduced specific rates of mercury demethylation. However, these changes were smaller than for methylation. Proportionally, specific rates of methylation increased faster than increasing concentrations of Hg2+, while specific rates of mercury demethylation increased linearly with increasing concentrations of methyl mercury. Overall, this study predicts that the net rate of methyl mercury production in the water column and at the sediment–water surface will increase as a result of lake acidification, and this may at least partially explain why the mercury concentration of fish appears to increase during lake acidification.

Calcium and Trace Metal Composition of Crayfish (Orconectes virilis) in Relation to Experimental Lake Acidification

1987 ◽  
Vol 44 (S1) ◽  
pp. s107-s113 ◽  
Author(s):  
Robert L. France
Keyword(s):  
Trace Metal ◽  
Dry Weight ◽  
Lake Acidification ◽  
Orconectes Virilis ◽  
Tissue Concentrations ◽  
Experimental Lakes Area ◽  
Background Levels ◽  
Metal Composition ◽  
Mn Content ◽  
Subjective Estimates

Subjective estimates indicate that the carapaces of crayfish from experimentally acidified Lake 223 (pH 5.4–5.6) in the Experimental Lakes Area are becoming less rigid. Decreased carapace rigidity was inversely correlated with carapace dry weight and Ca++ content. Orconectes virilis from L223 have 25–35% less Ca++ in their exoskeletons (mean % dry wt ± SE = 13.90 ± 0.54) than do those from reference lakes (19.82 ± 0.33, 20.34 ± 0.63, and 22.18 ± 0.51). Lake 223 crayfish have accumulated higher tissue concentrations of both Mn (L223 value of 240 μg∙g−1 dry wt compared to a mean ± SE for reference populations of 48 ± 11 μg∙g−1 dry wt) and Hg(L223 value of 0.52 μg∙g−1 dry wt compared to reference mean of 0.26 ± 0.05 μg∙g−1 dry wt). Mn content of carapaces in crayfish from acidified L223 were also elevated threefold over background levels for the ELA region.

Land water linkages: influences of riparian deforestation on lake thermocline depth and possible consequences for cold stenotherms

1997 ◽  
Vol 54 (6) ◽  
pp. 1299-1305 ◽  
Author(s):  
Robert France
Keyword(s):  
Thermal Stratification ◽  
Lake Trout ◽  
Salvelinus Namaycush ◽  
Thermocline Depth ◽  
Experimental Lakes Area ◽  
Northwestern Ontario ◽  
Riparian Trees ◽  
Tree Removal ◽  
Riparian Tree ◽  
Land Water

The purpose of the present study was to determine if riparian deforestation would expose lake surfaces to stronger winds and therefore bring about deepening of thermoclines and resulting habitat losses for cold stenotherms such as lake trout (Salvelinus namaycush). Removal of protective riparian trees through wind blowdown and two wildfires was found to triple the overwater windspeeds and produce thermocline deepening in two lakes at the Experimental Lakes Area. A survey of thermal stratification patterns in 63 northwestern Ontario lakes showed that lakes around which riparian trees had been removed a decade before through either clearcutting or by a wildfire were found to have thermocline depths over 2 m deeper per unit fetch length compared with lakes surrounded by mature forests. Riparian tree removal will therefore exacerbate hypolimnion habitat losses for cold stenotherms that have already been documented to be occurring as a result of lake acidification, eutrophication, and climate warming.

Phosphorus Budgets and Stoichiometry during the Open-Water Season in Two Unmanipulated Lakes in the Experimental Lakes Area, Northwestern Ontario

1994 ◽  
Vol 51 (12) ◽  
pp. 2739-2755 ◽  
Author(s):  
P. Campbell
Keyword(s):  
Water Column ◽  
Bottom Sediments ◽  
Open Water ◽  
Short Term ◽  
Experimental Lakes Area ◽  
Northwestern Ontario ◽  
Phosphorus Budgets ◽  
Mass Balance Approach ◽  
Primary And Secondary Producers ◽  
Column Total

A comparative mass-balance approach is used to describe and quantify phosphorus (P) cycles during the open-water season in two unmanipulated Experimental Lakes Area (ELA) lakes. A bimodal cycle generally prevailed, in which water-column total phosphorus (TP = total dissolved P plus sestonic particulate P) peaked just after ice-out and again late in the summer. Changes in mass of water-column TP were often much larger than corresponding net external inputs. Shifts of P to and from either zooplankton or fish in the water column do not explain the P residuals. Rather, the bottom sediments must have been adding P to the water column. Short-term regeneration of P from the bottom sediments also probably occurs in artificially eutrophied ELA lakes. The mechanism of regeneration is probably biological. Other aspects of P cycling and P stoichiometry are discussed, particularly in relation to nutrient control of population structure and the function of primary and secondary producers.

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