Cold Stenotherms Research Articles

Impact of predation by Mysis relicta on zooplankton in Flathead Lake, Montana, USA

We documented major changes in the zooplankton community of Flathead Lake following the appearance of Mysis relicta. The three common cladocerans found in the lake decreased in abundance, most notably Daphnia longiremis which virtually disappeared from the lake. Copepods were also affected by M.relicta, especially Diacyclops thomasi which decreased in abundance by an order of magnitude. The only macrozooplankton species which seemed to benefit from the presence of M.relicta was Leptodiaptomus ashlandi. The varied responses of dominant zooplankton species appeared to be the result of a combination of factors. Laboratory feeding studies indicate that M.relicta preferred Cladocera over Copepoda, with the following order of feeding preference: Bosmina longirostris > D.longiremis > Daphnia thorata > L.ashlandi > D.thomasi. The two zooplank- ton species which declined most following the appearance of M.relicta showed the greatest degree of habitat overlap with M.relicta. Daphnia longiremis and D.thomasi, together with M.relicta, are cold stenotherms and were concentrated in the hypolimnion during the summer. Finally, another trait shared by D.longiremis and D.thomasi was the absence of a diapause stage, which made them vulner- able to predation by M.relicta throughout the year.

Effects of evolutionary thermal environment on temperature-preference relationships in fishes

Fishes exhibit a perplexing variety of temperature-preference relationships, ranging from positive to negative functions of acclimation temperature. However, these relationships tend to be consistent within species even across broad geographic ranges. We developed and tested an hypothesis that temperature-preference relationships are related to the amplitude of the annual thermal-cycle experienced by species during their recent evolutionary histories. Species experiencing annual cycles of relatively high amplitude (temperate species) were predicted to exhibit temperature-preference relationships that are positive functions of acclimation temperature. Those with low thermal amplitudes, such as cold stenotherms, or relatively high short-term amplitudes, such as tropical mesotherms, were predicted to exhibit relationships that are either independent or negative functions of acclimation temperature. This hypothesis was tested and strongly supported by a synthesis of studies from the literature. Of 42 species, for which data were available, 40 exhibited the class of temperature-preference relationships that we predicted on the basis of their thermal cycle. The concept of thermal guilds can be expanded by taking into consideration the capacity of fishes to adjust preferred temperatures through acclimation. This work shows the adaptive nature of temperature-preference behavior and may be useful for predicting general characteristics of temperature-preference relationships for the many species not yet examined in this regard.

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

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.

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

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

The effects of climatic warming on the properties of boreal lakes and streams at the Experimental Lakes Area, northwestern Ontario

A period of prolonged warmer, drier‐than‐normal weather in northwestern Ontario during the 1970s and 1980s resulted in severe forest fires that caused dramatic changes to lake and stream catchments. The changed interactions of weather with catchments and hydrological processes caused unexpected changes in physical, chemical, and biological processes in lakes and streams. Permanent first‐order streams became ephemeral. Flows at spring melt were lower, and chemical exports from catchments were reduced. Although catchments burned by forest fire had slightly higher flows and chemical exports than unburned basins in the years following fires, chemical exports generally declined due to lower streamflow. Decreased exports of silica indicated lower rates of weathering. Base cation exports also decreased, as did the ratio of base cations to strong acid anions in streams.Changes in lakes included warmer temperatures, clearer waters, deeper thermoclines and euphotic zones, higher alkalinities, and higher concentrations of base cations and nitrogen, but lower concentrations of dissolved organic C, silica, and P. The increase in alkalinity was caused by increases in the ratio of base cations to strong acid anions, resulting from the interaction of increased water retention, microbial sulfate reduction, and exchanges of cations between water and sediments. Declines in chlorophyll and increases in phytoplankton biomass were observed, but there was no detectable effect on areal phytoplankton production. Summer subthermocline habitats for cold stenotherms were reduced slightly in extent as the results of thermocline deepening and lower hypolimnetic oxygen. There is considerable potential for interaction between climatic change and other human perturbations affecting boreal lakes, including acidification, increased incident UV radiation, eutrophication, and overharvesting.

Interaction of acid rain and global changes: Effects on terrestrial and aquatic ecosystems

Both acid deposition and changes in the global atmosphere and climate affect terrestrial and aquatic ecosystems. In the atmosphere sulphate aerosols tend to increase haze, altering the global radiation balance. Increased nitrogen deposition to N-limited systems such as boreal forests results in increased growth and increased sequestration of atmospheric CO2, slowing the increase in CO2 levels in the atmosphere. Future reduction in S and N emissions may result in a trade-off -- better with respect to some effects of acid deposition and greenhouse warming, but worse with respect to others. Global warming may cause the incidence and severity of drought to increase. Mineralisation of N and oxidation of organic S compounds release pulses of SO4, acid and Al to surface waters. Effects in lakes may include reduced deep water refugia for cold stenotherms, lower nutrient concentrations, and greater penetration of harmful UV radiation. Longer water renewal times cause declines in SO4 and NO3, due to increased in situ removal, but increases in base cations. The net result is increased internal alkalinity production. In areas characterised by cold winters, global warming may result in a major shift in hydrologic cycle, with snowmelt episodes occurring during the winter rather than the typical pattern of accumulation in the winter and melting in the spring. Increased storm frequency predicted for the future will cause increased frequency and severity of sea salt episodes in coastal regions. Predicting the interactions of regional and global environmental factors in the coming decades poses new challenges to scientists, managers and policy-makers.

Climatic and limnological changes associated with the Younger Dryas in Atlantic Canada

Pollen, diatom and chironomid fossils from the sediments of a core from Brier Island Bog Lake, Nova Scotia were studied in an attempt to relate changes in microfossil composition to a climatic cooling in Atlantic Canada correlative with the European Younger Dryas ca. 10 to 11 ka. Our paleolimnological data were then compared to similar types of data from Splan Pond, New Brunswick to determine if there were any significant differences between a coastal and a more inland site. Nonarboreal pollen was dominant throughout the Brier Island core and the interval 10.0–11.0 ka did not show the typical decline in Picea and increases in tundra-like vegetation characteristic of many sites in Atlantic Canada. However, the limnological indicators did undergo marked changes in taxon composition. The chironomid assemblage was initially dominated by shallow-water, warm-adapted chironomid taxa followed by abundant Sergentia (a cold stenotherm) during 10–11 ka. Sergentia disappeared in the “post Younger Dryas” interval and the warm-adapted genera resumed dominance. Chironomid-inferred paleotemperature reconstructions revealed that at both Brier Island Bog Lake and Splan Pond, summer surface-water temperatures dropped abruptly to between 13 and 17°C during the 10–11 ka interval, suggesting that a cooler climate was present in Atlantic Canada correlative with the European Younger Dryas. Diatom assemblage changes during the same period corroborate the occurrence of limnological fluctuations.

An association between Exspina typica Lang (Tanaidacea) and deep-sea holothurians

First reports of the association between Exspina typica and three species of abyssal holothurian are presented. These records suggest that the association is a real one, and not an artefact of sampling, but throw no light on the nature of the association. The geographic and bathymetric distributions of E. typica are summarized, and the species is shown to be a widely distributed cold water stenotherm.

Effects of Impoundment and Diversion on the Crustacean Plankton of Southern Indian Lake

Planktonic crustaceans in Southern Indian Lake were surveyed in 1972 before impoundment, during 1975 when water levels rose above the recorded high level, and then annually from 1977 to 1980 after full impoundment and diversion. Synoptic data were collected in each of these years in midsummer during July or August from a set of 53 stations covering all regions of the lake. Vertical hauls were made at each station using twin nets of 77-μm mesh and 25-cm mouth diameter. In 1972, the crustacean plankton fauna of Southern Indian Lake was composed mainly of 15 copepod and 15 cladoceran species. At least 25 of these species were truly pelagic, while 5 were littoral. Cyclopoids comprised 46% of total crustacean abundance, calanoids 33%, and cladocerans 21%. Dominant species within these three groups were Cyclops bicuspidatus thomasi (37.6% of total abundance), Diaptomus ashlandi (20.1%), and Chydorus sphaericus (8.9%). Total abundance averaged 76 individuals (ind)∙L−1, comparable to more southerly waters such as Lake Ontario (80 ind∙L−1) and Lake Winnipeg (53–108 ind∙L−1) (K. Patalas. 1975. Int. Ver. Limnol. Verh. 19: 504–511). Throughout the lake, total crustacean abundances varied from 10 ind∙L−1 near the Churchill River inflow to between 100 and 200 ind∙L−1 in a few well protected areas. From 50 to 100 ind∙L−1 occurred within the main body of Southern Indian Lake. In 1975, an unusually high water year, lake mean plankton abundance was 61 ind∙L−1. Following diversion in 1976, no dramatic changes in species composition were observed. However, the mean abundance of crustaceans decreased to 40–46 ind∙L−1 during the period 1977–80. Regional zooplankton responses were varied. No significant changes occurred in areas adjacent to the Churchill River inflow, with pre- and post-diversion densities being 35 and 36 ind∙L−1, respectively. In the main water bodies north of the diversion route, abundances declined by 60% and biomass by 50%. A 2–3 °C drop in northern basin water temperatures, related to diversion, reduced growth rates by approximately 20% and resulted in a 60% decline in crustacean production. Not all groups of crustaceans responded similarily to impoundment and diversion. Lakewide average numbers of cladocerans declined from 16 to 4 ind∙L−1 and the area of their distribution was reduced particularly in northern regions of the lake following impoundment. Cyclopoids declined from 35 to 16 ind∙L−1 but showed no change in their distribution. These reductions were related to decreased water temperatures, lower midsummer chlorophyll a concentrations, and decreased water transparencies. The mean abundance of calanoids as a group did not change, but the abundance and distribution of individual species were variably altered. Smaller calanoid species showed either no change or a decrease in their numbers and distribution. Larger species, e.g. Limnocalanus macrurus, Senecella calanoides, and Diaptomus sicilis, were significantly more abundant and widespread following diversion. Similar increases in Mysis relicta were also observed. These large species, preferred food items for both whitefish and cisco, are cold stenotherms, inhabiting deeper water layers. Their increased abundance is likely associated with decreased water transparency offering better protection against predatory fish, decreased water temperature creating more favorable conditions, and increased water depth enlarging the volume of deeper waters suitable for these species.

Decline of Mysis relicta During the Acidification of Lake 223

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.

Zooplancton limnétique de 46 lacs et 17 rivières du territoire de la baie de James

From June through October 1973, 335 samples of limnetic plankton were collected from 46 lakes and 17 rivers of the James Bay area. Sixty zooplanktonic species were identified (20 Copepoda, 27 Cladocera, and 13 Rotifera). The most common and widespread species are cold stenotherms (Leptodiaptomus minutus, Diacyclops bicuspidatus thomasi, Epischura lacustris, Holopedium gibberum, Bosmina longirostris, Daphnia longiremis, and Kellicottia longispina). In order to study the typology of the lake samples, the data were subjected to three types of statistical analyses: principal components analysis, single linkage, and complete linkage clustering. Five groups of lakes emerged from these analyses: types IV and V are located in the northeastern portion of the studied area, whereas types I and II were identified in the western portion, corresponding with the area occupied by the Tyrrell glacial sea. Type III fills an intermediate position. Types II, III, and V are smalt lakes. The characteristic zooplanktonic communities of each group are described, whereas the principal components and the components of the diversity are correlated with the environmental data.

Biological features of Pupu Springs

Abstract The flora and fauna of Pupu Springs (40°51'S, 172° 46'E) and five other New Zealand cold springs are described. In Pupu Springs there are 16 species of algae, 10 species of bryophytes (including three species of liverworts), and 5 species of angiosperms. The fauna includes a phreatic form (an eyeless planarian, Dugesia sp.), a possible glacial relict (the caddis fly Rakiura vernale), and cold stenotherms (e.g., the caddis fly Psilochorema tautoru). The most abundant animals in the New Zealand springs are Mollusea, Crustacea, and’ larvae of Plecoptera, Diptera, and Trichoptera. Pupu Springs consist of five biotopes and associated biocoenoses.

Notholca laurentiae and N. michiganensis, New Rotifers from the Laurentian Great Lakes Region

The descriptions of two new planktonic rotifers, both cold stenotherms, is presented. Notholca laurentiae n.sp. is a predominant winter rotifer of the Laurentian Great Lakes, but to date has not been found in inland lakes of the region. Morphologically its closest relative is the European brackish water species, N. salina Focke.Notholca michiganensis n.sp. has been recorded only in the oligotrophic inland lakes of the northern portion of Michigan’s lower peninsula during winter and early spring (water temperatures 0.5–5.2 C). Morphologically, N. michiganensis is similar to, but distinctly smaller than N. frigida Jaschnov.