Patterns in phytoplankton taxonomic composition across temperate lakes of differing nutrient status

نویسندگان

  • Susan B. Watson
  • Edward McCauley
  • John A. Downing
چکیده

We describe the relationships between summer average total phosphorus (TP) and the biomass of six major phytoplankton taxonomic groups from 91 north temperate lakes. Both regression and a locally weighted smoothing (LOWESS) analyses show that all groups increase with TP but over different nutrient ranges. At nutrient extremes, i.e. very low and high levels of TP, the few taxonomic groups that dominate total biomass are generally dissimilar. In oligotrophic and eutrophic lakes, most group biomass curves show corresponding increases or decreases, but different rates of change. The curves converge at intermediate TP levels (-10-30 p,g liter-l) where there is increased equitability among algal groups. In highly eutrophic lakes, the slope of the total biomass curve decreases, as do all the relative abundances of all groups except blue-greens and diatoms. We conclude that the curvilinearity of the TP-total biomass curve is not attributable to a single taxonomic group, because all groups show some nonlinearity in relation to TP We suggest that morphological diversity, differential herbivory, and, in particular, mixing regime may explain some of the-observed patterns.There is a well-established, positive relationship between nutrient loading and productivity in lakes (e.g. Schindler 1978), which is most readily apparent as increasing phytoplankton biomass with eutrophication (Nicholls and Dillon 1978). Growth of phytoplankton may be limited by one of several nutrients (e.g. phosphorus, nitrogen, carbon, silica) in a manner that has been related to cellular stochiometric ratios (e.g. Hecky and Kilham 1988), but in the majority of temperate zone lakes, annual productivity is most frequently phosphorus limited (e.g. Smith 1982). Numerous studies have shown that phytoplankton taxonomic composition and species diversity change with increasing nutrient levels (e.g. LaZerte and Watson 198 1; Smith 1990) and that these changes are related to differences among taxa in nutrient uptake, storage, growth, and loss rates (Kalff and Knoechel 1978; Reynolds 1984). In temperatezone lakes, oligotrophic systems support minimal phytoplankton biomass with low species diversity and are generally dominated by nanoflagellates belonging to the Chrysophyceae and Cryptophyta or by cyanobacterial or chlorophyte picoplankton (e.g. Pick and Caron 1987; Willen et al. 1990). Moderate enrichment results in higher and more seasonally variable levels of phytoplankton biomass, along with increased taxonomic diversity (Sommer et al. 1986). In these mesotrophic systems, most algal taxonomic groups are represented over the growing season, especially Bacillariophyceae (diatoms), Chlorophyta (green algae), Cryptophyta, and Dinophyta, as well as Cyanobacteria and Chrysophyceae (e.g. Rosen 1981; Eloranta 1986). Eutrophic and hypereutrophic lakes sustain very high average algal biomass often I Present address: Iowa State University, Department of Animal Ecology, 124 Science II, Ames, Iowa 50011-3221. Acknowledgments This study was supported by Natural Sciences and Engineering Research Council of Canada operating grants to E.M. and J.A.D. dominated by very few taxa, usually Cyanobacteria, diatoms, or in some water-bodies, chlorococcales or dinoflagellates (e.g. Paerl 1988b; Padisak and Dokulil 1994; Jensen et al. 1994). Surprisingly, there are few quantitative comparisons of changes in the average biomass of major phytoplankton taxa with nutrient levels among lakes, although some studies have measured changes in the average proportions (%), or dominance, of some algal divisions (Smith 1990; Duarte et al. 1992; Chow-Frazer et al. 1994). Shifts in phytoplankton taxonomic structure with enrichment have been documented by extensive single sample surveys of lakes (e.g. Rosen 1981; Eloranta 1986; Willen et al. 1990) and have been qualitatively described in excellent reviews of general successional dynamics (e.g. Reynolds 1984; Hecky and Kilham 1988) and of individual taxonomic groups (e.g. Paerl 1988a; Sandgren 1988; Willen 1991). These shifts have been successfully predicted for individual species on a local scale (i.e. within lakes) using resource-competition models (e.g. Tilman 1982; Sommer 1993) and more complex mechanistic models (e.g. Smith et al. 1987; Varis 1993). Furthermore, several studies have empirically described the increase of cyanobacterial biomass with total phosphorus in north temperate (Smith 1986; McQueen and Lean 1987) and subtropical lakes (Canfield et al. 1989); however, similar quantitative relationships for other major groups have not, to our knowledge, been derived. In previous work, we and other authors have shown that algal biomass measured as either chlorophyll a (Chl a) or algal biovolume varies nonlinearly with total phosphorus (TP) (McCauley et al. 1989; Prairie et al. 1989; Watson et al. 1992), and we suggested that this curvilinear&y reflects nonuniform growth and loss rates of one or more components of the total phytoplankton community. We tested the idea that this nonlinearity can be explained by differences in the responses to enrichment of two functional size fractions with high and low susceptibility to zooplankton grazing

برای دانلود رایگان متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Potamoplankton size structure and taxonomic composition: Influence of river size and nutrient concentrations

We measured the size structure and taxonomic composition of phytoplankton in temperate rivers during base flows of summer to investigate the influence of river size, ambient nutrient concentration, and light availability on potamoplankton community structure. Algal biomass was measured in three size classes (2–20, 20–64, and .64 mm) by microscope enumeration of water samples collected in 31 riv...

متن کامل

Perspectives for an integrated understanding of tropical and temperate high-mountain lakes

High mountain lakes are extreme freshwater ecosystems and excellent sentinels of current global change. They are likely among the most comparable ecosystems across the world. The largest contrast occurs between lakes in temperate and tropical areas. The main difference arises from the seasonal patterns of heat exchange and the external loadings (carbon, phosphorus, metals). The consequence is a...

متن کامل

Phytoplankton lipid content influences freshwater lake methanogenesis

1. Rates of methanogenesis in freshwater sediments have been shown to increase with inputs of phytoplankton biomass. Although many studies have shown the importance of resource quality for decomposition, little is known of the importance of substrate quality on rates of methanogenesis. 2. Here, we studied the effects of lipid content and taxonomic affiliation of phytoplankton biomass on rates o...

متن کامل

Have we overlooked the importance of small phytoplankton in productive waters?

The idea that phytoplankton size structure increases with elevated nutrient content in lakes may be inaccurate because phototrophic picoplankton (Ppico) abundance was not accounted for in studies that originally described this phenomenon. The biomass, composition, and production of an entire phytoplankton community was evaluated in hypereutrophic Lake Apopka, Florida (avg chlorophyll = 105 pg l...

متن کامل

A short term study on vertical distribution of phytoplankton biomass and nutrients in the pelagic zone in Lake Tanganyika Student: Bigeyo Kuboja

Phytoplankton are microscopic plants that gain energy from the sun through photosynthesis. They are important primary producers in most lakes. Lake Tanganyika exhibits a greater relative range between annual maximum and minimum phytoplankton biomass than most tropical lakes or temperate Great Lakes (Hecky and Kling, 1981; Hecky and Fee, 1981). This is due in part to the permanent stratification...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 1999