Profundal zone

About: Profundal zone is a research topic. Over the lifetime, 797 publications have been published within this topic receiving 24819 citations.

PRIMARY CONSUMER δ13C AND δ15N AND THE TROPHIC POSITION OF AQUATIC CONSUMERS

Abstract: Stable nitrogen isotope signatures (δ15N) are increasingly used to infer the trophic position of consumers in food web studies. Interpreting the δ15N of consumers relative to the δ15N characterizing the base of the food web provides a time-integrated measure of trophic position. We use primary consumers (trophic level 2) as baseline indicator organisms and investigate the variation in baseline δ15N values in 14 lakes in Ontario and Quebec. Values of δ15N ranged from −2 to +9‰ and varied significantly as a function of lake habitat (mean littoral = 1.6‰, pelagic = 3.1‰, profundal = 5.2 ‰). Stable carbon isotopic signatures (δ13C) of primary consumers decreased along this same habitat gradient (mean littoral = −23.8‰, pelagic = −28.4‰, profundal = −30.5‰). Primary consumer δ13C and a categorical lake variable explained 72% of the variability in primary consumer δ15N. This relationship was corroborated by primary consumer δ15N and δ13C data from the literature, indicating that habitat-specific variation in ba...

Stratigraphic classification of ancient lakes: Balancing tectonic and climatic controls

Abstract: Lakes and lake deposits present two fundamental paradoxes: (1) Modern lakes are vastly complicated, but the rock records of lakes are relatively simple; extensive observations reveal three distinct facies associations of common and widespread occurrence. These are referred to here as fluvial-lacustrine, fluctuating profundal, and evaporative facies associations. (2) Most explanations of modern and ancient lakes attribute their nature to climate, but neither modern lake parameters (lake size, depth, and salinity) nor the character of ancient-lake strata (thickness, extent, lithology) correlate with measured or inferred climatic humidity. We propose that it is the relative balance of rates of potential accommodation (mostly tectonic) with sediment + water fill (mostly a function of climate) that controls lake occurrence, distribution, and character. Lake basins may be termed overfilled, balanced fill, or underfilled, depending on the balance between these rates. We conclude that climate and tectonics exert coequal influence on lake deposits at both mesoscales (1 m to hundreds of meters) and macroscales (hundreds to thousands of meters).

Chironomid communities as water quality indicators

Abstract: Recent mathematical indices summarizing biological communities of indicators are recapitulated. Improvements of these indices based on weighting according to width of trophic ranges of each species are suggested. Their principle deficiencies, however, are pointed out. Revised lists of characteristic profundal as well as littoral and sublittoral chironomids in Nearctic and Palearctic lakes show that at least 15 characteristic chironomid species communities can be delineated, 6 in each of the oligotrophic and the eutrophic ranges and 3 in the mesotrophic range. It is proposed that these communities be lettered consecutively in the Greek alphabet from α (alpha) to o (omikron). A key to the 15 divisions based on the species associations in the profundal zone of harmonic lakes is put forward. There is very good correlation between the 15 divisions and the ratios of average total phosphorus to mean lake depth and average chlorophyll a to mean lake depth. The ratio of chironomids to oligochaetes and the distribution patterns of single species have proven useful in pin-pointing localized areas of pollution. The primary mechanism governing the distribution of chironomid communities in oligotrophic and mesotrophic lakes appears to be the availability of food materials rather than the annual hypolimnetic oxygen concentration. In eutrophic lakes the relationships between organic matter accumulation and oxygen levels are so interdependent as to be inseparable.

Use of benthos in lake monitoring

Abstract: The paper discusses the rationale behind the use of biological variables in environmental monitoring of lakes, as well as the principles of variable selection and the limitations of data usability. Profundal benthic communities are suggested to be an integral measure of autotrophic and heterotrophic lake processes. Measures of community structure and their relationship to morphometric and edaphic factors are presented and discussed, including indicator species/communities, diversity/species richness, oligochaete/chironomid ratio, and oligochaete abundance.