Inter-lake Comparison Research Articles

Intra-lake trends and inter-lake comparisons of Mysis diluviana life history variables and their relationships to food limitation

The opossum shrimp, Mysis diluviana, is an important member of the offshore food webs of the Laurentian Great Lakes, but its response to ecosystem changes that have occurred over the past several decades is not well understood. We combined the data of four long-term sampling programs, adding several years of data (post and prior) to previously published analyses to offer a longer-term, cross-basin analysis of M. diluviana populations in the Great Lakes from 1997 to 2019. Densities were high in lakes Superior and Ontario (summer values 100–300/m2), high and variable but declining (from 200–300/m2 in 1997–2004 to less than 100/m2 in 2017–2019) in Lake Michigan, low (∼20–50/m2 since 2005) in Lake Huron, and very low in shallower eastern Lake Erie (<1/m2). Biomass showed similar trends. Life history parameters (mortality, fecundity, and growth) were consistently highest in eastern Lake Erie, followed by lakes Ontario, Michigan, Huron, and Superior. Generation time was 1 year in Lake Erie and 2 years in the other lakes. Cross-basin relationships between annual M. diluviana areal densities and food indices (chlorophyll-a concentration and zooplankton biomass) were non-linear, increasing with food levels up to about 250 mysids/m2 and about 650 mg dry wt/m2. Annual growth rates were also positively correlated to both food indices in the four deep lakes, but fecundity and mortality rates were not. Our results suggest food availability is a primary factor predicting M. diluviana density and biomass. Density-dependent mortality and fish predation could explain some of the inter-lake differences, but these relationships could benefit from further investigations.

Harmonizing heterogeneous multi-proxy data from lake systems

When performing spatial-temporal investigations of multiple lake systems, geoscientists face the challenge of dealing with complex and heterogeneous data of different types, structure, and format. To support comparability, it is necessary to transform such data into a uniform format that ensures syntactic and semantic comparability. This paper presents a data science approach for transforming research data from different lake sediment cores into a coherent framework. For this purpose, we collected published and unpublished data from paleolimnological investigations of Arctic lake systems. Our approach adapted methods from the database field, such as developing entity-relationship (ER) diagrams, to understand the conceptual structure of the data independently of the source. We demonstrated the feasibility of our approach by transforming our ER diagram into a database schema for PostgreSQL, a popular database management system (DBMS). We validated our approach by conducting a comparative analysis on a set of acquired data, hereby focusing on the comparison of total organic carbon and bromine content in eight selected sediment cores. Still, we encountered serious obstacles in the development of the ER model. Heterogeneous structures within collected data made an automatic data integration impossible. Additionally, we realized that missing error information hampers the development of a conceptual model. Despite the strong initial heterogeneity of the original data, our harmonized dataset leads to comparable datasets, enabling numerical inter-proxy and inter-lake comparison.

Calibration of the zooplankton community size spectrum as an indicator of change in Canadian Shield lakes

Developing the crustacean zooplankton community size spectrum into an indicator of change in lakes requires quantification of the natural variability in the size spectrum related to broad-scale seasonal, annual, and spatial factors. Characterizing seasonal patterns of variation in the size spectrum is necessary so that monitoring programs can be designed to minimize the masking effects that seasonal processes can have on detecting longer-term temporal change. We used a random effects model to measure monthly, annual, and interlake variability in the slope (i.e., relative abundance of small and large organisms) and centered height (i.e., total abundance) of the crustacean zooplankton normalized abundance size spectrum from 1981 to 2011 among eight Canadian Shield lakes. Consistent with theoretical predictions, the slope was a relatively stable characteristic of the zooplankton community compared with the height, which varied significantly among lakes. We identified a seasonal signal in height and slope and used a mixed effects model to characterize the linear rate of change from May to October; there was an overall decline in height and an overall increase in slope. Seasonal variance was greater than annual variance for both the height and the slope, suggesting that long-term monitoring of lakes and interlake comparisons using zooplankton size spectra should be based on temporally standardized sampling protocols that minimize the effects of seasonal processes. We recommend sampling the zooplankton community in midsummer because this results in size spectrum estimates close to seasonal mean values.

Sources contribution for benthic invertebrates: an inter-lake comparison in a flood plain system

To explore temporal variation in trophic relationships of benthic invertebrates in the Middle Parana River floodplain, we performed stable isotopes analysis (SIA) in two lakes with contrasting morphologies during both dry and flooding periods. Lake 1 is permanently connected, large and deep with a narrow aquatic–terrestrial transition zone (ATTZ), and Lake 2 is temporarily connected, small and shallow with a wide ATTZ. The source contribution analysis showed that macrophytes and sediment particulate organic matter are important basal resources. We found sharp temporal variations with regard to gatherer–collectors in Lake 2, being sediment particulate organic matter the most important source during dry period. However, during flooding, macrophytes and epiphyton increased their importance. Our results reveal temporal variations in trophic interactions, suggesting that hydrologic and morphologic characteristics of water bodies can be important factors determining food web structure. Besides, we provide evidence from floodplain lakes of the Middle Parana River, which contradicts the general idea that algae is the main carbon source in floodplain rivers.

Inter-lake comparisons indicate that fish predation, rather than high temperature, is the major driver of summer decline in Daphnia and other changes among cladoceran zooplankton in subtropical Florida lakes

The mid-summer disappearance of Daphnia and the small size of cladocerans in subtropical lakes have been explained as phenomena caused by high water temperature. Recent experimental and observational studies suggest that instead, fish predation could be the cause. In the present study, we evaluated effects of temperature and fish predation by comparing summer occurrence of Daphnia and seasonality of other cladocerans in subtropical lakes where there was (a) vegetation and a high abundance and diversity of planktivorous fish; versus (b) no vegetation, turbid water, and primarily benthivorous and piscivorous fish. Daphnia disappeared from mid-summer plankton samples at all locations with vegetation, yet it persisted year-round at the turbid vegetation-free location despite identical water temperatures (all lakes were shallow and isothermal). Body size of cladocerans, in general, was twofold lower at vegetated locations, and biomass was threefold lower. Smaller species dominated at the locations with vegetation, especially in summer. Our results demonstrate that in subtropical lakes Daphnia is able to tolerate high summer water temperatures, and suggest that fish predation may be a more important regulator than temperature for cladoceran size, biomass and taxonomic structure.

Mass-dependent and mass-independent variations in the isotope composition of mercury in cores from lakes polluted by a smelter: Effects of smelter emissions, natural processes, and their interactions

Analysis of sediment cores from three lakes polluted by a smelter and located 3.8, 9.4, and 21.0km from it revealed that mercury (Hg) in smelter fallout has an isotope signature which denotes enrichment in lighter isotopes by mass-dependent fractionation (MDF), suggesting volatilisation as isotopically light Hg(0) followed by oxidation to reactive gaseous Hg(II) by flue gas constituents. However, the signature was detected only in the lake closest to the smelter; elsewhere it was obliterated by MDF and mass-independent fractionation (MIF) due to natural processes, whose effects varied with environmental factors, including smelter emissions. MIF caused depletion in 199Hg and 201Hg in all three lakes and was enhanced by dissolved organic matter but inhibited by heavy metals from the smelter; yet inter-lake comparison showed that the inhibition increased with decreasing metal concentration (i.e. with increasing distance from the smelter). Inhibition of MIF by metals was strongest in acidic and oxidising environments, and the inhibitory effects of individual metals depended on the metal's atomic polarisability. MDF was controlled by different processes, was more sensitive to local conditions, correlated with sulphate concentrations in lake water, and showed weaker net inhibition by metals; and inhibition by individual metals depended on the standard enthalpy of formation of the aqueous metal cation. Moreover, the combined effects of MDF and MIF varied with the sediment's Zn/Cu ratio but not with its Zn or Cu concentration alone. MIF is attributable to activities of anaerobic heterotrophic bacteria which were inhibited by the metals, whose toxicity depended on the properties, speciation, bioavailability, and interactive effects of the metals. The exacerbation of metal toxicity under acidic and oxidising conditions, and with increasing distance from the smelter, can be explained by enhanced bioavailability. MDF, too, is attributable to effects of bacteria, metals, and environmental variables but involved different mechanisms and pathways.

Rotifer communities in the Laurentian Great Lakes, 1983–2006 and factors affecting their composition

Rotifer communities were examined from the open waters of the Laurentian Great Lakes between 1983 and 2006 in the first inter-lake comparison involving all five lakes. Seventy rotifer taxa were found in summer samples, although most (> 80%) individuals were drawn from the following taxa: Conochilus unicornis, Polyarthra vulgaris, Keratella cochlearis, Kellicottia longispina, Keratella crassa, Synchaeta spp., Polyarthra major, Ploesoma truncatum, Keratella earlinae, and Keratella quadrata. Distributions of Filinia longiseta and several species of Brachionus and Trichocera were restricted to regions of higher trophy, notably the western basin of Lake Erie, but most taxa were widely distributed, differing in relative dominance rather than presence or absence. Rotifer community structure appeared to respond in tractable ways to differences in trophic state, with the four most common genera exhibited the following preferences, in order of decreasing trophy: Polyarthra, Keratella, Conochilus, and Kellicottia. Recent oligotrophication in Lake Huron was reflected in decreases in Keratella dominance and increased dominance of Conochilus, while in Lake Michigan oligotrophication was associated with decreases in Polyarthra and Keratella and increases in Conochilus, and Kellicottia. In Lake Ontario, the appearance of the exotic predatory Cercopagis pengoi was strongly associated with dramatic reductions in Polyarthra, while more gradual sequential increases in the dominance of Keratella, Conochilus and Kellicottia were probably the result of decreasing trophic state. Bythotrephes was identified in multivariate analyses as correlating strongly with rotifer composition, although only in Lake Michigan was a clear relationship between the predatory cladoceran and rotifer species shifts observed.

The use of littoral mesohabitats and their macroinvertebrate assemblages in the ecological assessment of lakes

Abstract Historically, ecological assessment of lakes has depended on open‐water chemical and phytoplankton analysis, with trophic status determined by chlorophyll a and total phosphorus following the general protocol of the OECD lake classification scheme. This has been accompanied by a prevailing opinion that the littoral zone of lakes is too heterogeneous to allow meaningful inter‐lake comparisons. Council of the European Communities Directive 2000/60/EC establishing a framework in the field of water policy (the Water Framework Directive) requires a broader approach to ecological assessment, including the need to incorporate a range of biotic variables. This paper describes the results of a monitoring programme designed to determine within‐ and among‐lake variation of macroinvertebrate communities found in defined mesohabitats of 22 lakes incorporating a range of lake types. Three sampling approaches were applied to the study. Triplicate macroinvertebrate samples from a cobble/pebble mesohabitat of 11 lakes showed that community composition from a standard habitat was robust. Twinned samples from contrasting habitats of pebble/cobble and macrophyte dominated mesohabitats of 21 lakes had greater similarity within than among lakes. This showed that even across contrasting habitat structure, macroinvertebrate assemblages can provide a reliable lake‐specific indicator. Multivariate analysis of replicate samples from 15 visually distinct mesohabitats in one lake showed that within‐lake variation could, nevertheless, be identified as distinct clusters of invertebrate assemblages. Conclusions from the work are that variations within lakes were nested in among‐lake variation across a range of lake types, and that macroinvertebrate assemblages can provide meaningful assessment of ecological differences across lakes. Monitoring can, however, produce a substantial amount of ‘noise’ from the data that reflects the complexity of macroinvertebrate community structure in littoral zones. It is recommended that incorporation of macroinvertebrates in ecological assessment is most useful when confined to well defined mesohabitats rather than attempt to incorporate a complete range of mesohabitats within a single lake. Copyright © 2003 John Wiley &amp; Sons, Ltd.

A paleomagnetic record from Lake Lama, northern Central Siberia

Abstract Two cores from Lake Lama, northern Central Siberia, with lengths of 19 and 11 m, respectively, were subjected to detailed magnetostratigraphic investigations. Directions of the characteristic remanent magnetisation (ChRM) were derived from vector analysis of the results from alternating field (A.F.)-demagnetisation, yielding records for the last 18,000 years BP. The sediments show a distinct change in sedimentation pattern at around 14,500 years BP from a highly variable to a monotonous sedimentation with anoxic conditions in the lake sediments during the last 11,500 years BP. The oxic/anoxic boundary is reflected in all rock-magnetic parameters measured and the magnetic mineral fraction is affected by reductive dissolution of iron-bearing minerals, here mainly magnetite. Therefore, no record of relative paleointensity could be achieved. But, as intra- and inter-lake comparison of the obtained inclination and declination records have shown, the directions of the geomagnetic field recorded in the sediments from Lake Lama were not severely affected by the partial dissolution of the remanence carrying minerals.

Sublethal responses of largemouth bass to parasites and organochlorines

Largemouth bass (Micropterus salmoides) at the Rocky Mountain Arsenal National Wildlife Refuge (RMA) experience chronic organochlorine exposures and parasitism by nematodes (Contracaecum spiculigerum) and digenean flukes (Posthodiplostomum minimum centrarchi). We investigated the influences of nematode intensity, fluke intensity, and whole-body organochlorine concentrations on growth of juvenile RMA bass. Lifetime growth, or age-specific lengths, of bass in three RMA lakes were within the range observed for bass in five reference lakes. However, interlake comparisons can be confounded by differing environmental conditions. Therefore, we conducted mesocosm and laboratory studies to compare growth, consumption, and feeding behavior between RMA bass and bass that had little contaminant or parasite exposure. Mean growth rates of RMA bass were 45% lower compared with hatchery bass in experimental ponds. However, regression analysis revealed that parasite and organochlorine burdens were not negatively associated with either short-term growth or age-specific lengths of RMA bass. Hatchery bass growth was likely higher due to their experience with culture pond conditions. In feeding trials, RMA bass exhibited similar food conversion efficiency and consumption rates and significantly elevated feeding activity compared with hatchery bass. This research demonstrates that current parasite and organochlorine loads had benign influences on growth of juvenile RMA bass.

National Center for Ecological Analysis and Synthesis, Santa Barbara, California 93101 and Center for Limnology,University of Wisconsin, Madison, Wisconsin 53706

Anthropogenic alterations of nutrient inputs and food‐web structure are two of the primary stressors affecting lake phytoplankton. This paper explores the independent and interactive effects of nutrients and food‐web structure (as indexed by zooplankton size) on phytoplankton size structure by fitting time‐series models to data from three lakes where both factors have been manipulated. I assessed phytoplankton size structure using three different approaches: small and large size classes, normalized size spectra, and average phytoplankton size. Increased phosphorus loading and increased zooplankton size had positive effects on large phytoplankton, slope of size spectra, and mean phytoplankton size, but negative effects on the relative abundance of small phytoplankton. The absolute abundance of small phytoplankton was increased by increased nutrients and decreased by increased zooplankton size. There was some evidence for nutrient 3 zooplankton interactions, particularly from interlake comparisons which revealed that phytoplankton size structure responded to enrichment in qualitatively similar but quantitatively different ways in lakes with different food webs. Specifically, small phytoplankton increased more strongly with enrichment in lakes with many planktivores and few large zooplankton, while large phytoplankton increased more in lakes with few planktivores and many large zooplankton. Thus, food‐web structure may influence the extent to which small vs. large phytoplankton respond to nutrient enrichment. Overall, size structure was an excellent descriptor of shifts in phytoplankton communities following manipulation of nutrient inputs and food‐web structure. Size spectra and size classes were highly effective approaches for summarizing size structure; average phytoplankton size was somewhat less effective.

The effects of lake acidification on aquatic macrophytes—A review

Acidification of lakes results in a number of chemical, physical and biological changes. This review initially outlines the major floristic changes that occur in acidifying and limed lakes. The different types of evidence (historical comparisons, inter-lake comparisons and palaeoecological studies) are considered. These studies emphasise the replacement of calcicole species and others such as the isoetids with Juncus bulbosus and Sphagnun spp. in acidifying lakes. The review then discusses the way in which the various alterations in lake conditions affect the physiology of the macrophytes, particularly with changes in the availability of carbon, a change from nitrate to ammonium as a nitrogen source and the effects of an alteration in the Lake light climate. The population biology, community ecology and ecosystem functioning of macrophytes are discussed, especially where competitive processes may seem more important in determining community change than physiological processes. Particular consideration is paid to the types of evidence of floristic change that are useful and the importance of undertaking experimental studies at the correct scale to determine which factors may be causally related to the floristic evidence.

Accumulation of Cadmium by White Suckers (Catostomus commersoni) in Relation to Fish Growth and Lake Acidification

The liver, kidney, muscle, and bone tissues of white suckers (Catostomus commersoni) captured from six lakes in south-central Ontario were analyzed for Cd content. The lakes ranged in pH from 4.8 to 6.4 and contained elevated Cd concentrations in the recently deposited sediments. Cd was found to be bioaccumulating in the livers of fish from both acid and circumneutral lakes, with fish from (acid) George Lake (ages 2–5) and (neutral) Red Chalk Lake (ages 7–14) containing similar concentrations. Calculated growth constants for each of the six populations revealed considerable variations in fish growth rates. A method is presented which represents the age, weight, and tissue Cd concentrations data for the six populations such that interlake comparisons of metal bioavailability can be made with the possible effects that the different fish growth rates may have on rates of metal accumulation factored out. When presented in this manner, our results imply that, on the linear portion of the growth curve, the growth rates of each population, and not effects due to lowered lake pH, can account for the concentrations of Cd in five of the six fish populations. Therefore, since tissue-metal concentrations in fish from stressed lakes will be dependent on both metal bioavailability and fish growth rates, it is essential that these be reported together.

Empirical Relationships Between Phytoplankton and Zooplankton Biomass in Lakes

Empirical models based on regression analysis were derived using published values of phytoplankton and crustacean zooplankton biomass from lakes. Equations presented predict crustacean zooplankton biomass from measures of phytoplankton biomass. Zooplankton biomass was shown to be positively related to phytoplankton biomass based on an inter-lake comparison. Analyses of functional regression equations suggest that the ratio of zooplankton to phytoplankton biomass decreases as phytoplankton biomass increases among lakes. It is hypothesized that variation in the biomass of nannoplankton, representing the principal food source for crustaceans present in the phytoplankton community, can account for the variation in the biomass of the crustacean zooplankton community.Key words: phytoplankton, zooplankton, biomass, nannoplankton

The areal hypolimnetic oxygen deficit: An empirical test of the model1

The areal hypolimnetic oxygen deficit (AHOD) model was tested by examining the relationship between rates of hypolimnetic oxygen depletion and three measures of lake trophic status. Measurements of AHOD were positively correlated with the measured total phosphorus concentration and with annual 14C pelagic primary production and inversely correlated with mean summer Secchi depth. Because each of the correlations between AHOD and trophic status explained &lt;45% of the observed variation in A HOD values, other factors must also influence the AHOD of a lake. Significant amounts of the residual variation were explained by including the mean depth of the lake and mean hypolimnetic temperature as additional independent variables in a multiple regression analysis. A lake with a thicker or warmer hypolimnion had a higher AHOD than a lake with a shallow or colder hypolimnion. The AHOD model was developed to eliminate the influence o f lake morphometry on interlake comparisons of hypolimnetic oxygen depletion, but it does not do this and a new model must be developed.

Freshwater ecology in the Mato Grosso, Central Brazil, IV: Associations of testate Rhizopoda

Summary Samples from five meander lakes in the valley of the Rio Suia Missu and from the Rio das Mortes at Xavantina, contained a total of 43 species of testate rhizopods, including a new genus with a complex multiporate mouth. Only one of the species is restricted to S. America in its known distribution. Analysis of the associations in the samples revealed that they were inadequate for inter-lake comparisons, and that the samples were representative of more restricted habitats. A comparison of the total list of species with the known fauna of the River Sokoto in Nigeria gave a higher index of similarity than any of the inter-lake comparisons in the Suia Missu. This is taken as an indication of the existence of an association that might be widespread in tropical riverine meander-lake systems.