Responses of phytoplankton to varied resource availability in large lakes of the Greater Yellowstone Ecosystem

Abstract

We assessed phytoplankton dynamics in three lakes in the Greater Yellowstone Ecosystem to better understand the connections between changing environmental conditions and aquatic communities. This work primarily describes the connections between resource availability and phytoplankton seasonal succession in these lakes. We hypothesized that algal species efficient at utilizing a given resource (including N, P, Si, and light) would be correlated with low relative concentrations of those resources. The lakes generally exhibited moderate resource limitation, which is characteristic of lakes in subalpine and subarctic regions. Although in proximity, the lakes all exhibited different resource relationships: Lewis Lake was most P limited, Jackson Lake was most N limited, and Yellowstone Lake exhibited a moderate degree of N limitation along with periodic Si limitation. Mixing depths and light penetration were also variable among lakes. In 1996, spring diatom biomass was dominated by Stephanodiscus minutulus, Asterionella formosa, Aulacoseira subarctica, and Synedra sp. Relative abundances and dominance varied among the lakes. A. formosa and Synedra sp. abundances were positively correlated with total N : total P (TN : TP) levels in an analysis of data from all three lakes. A. subarctica was negatively correlated with TN : TP and all light : nutrient ratios. Species exhibiting late season maxima included Cyclotella bodanica, Fragilaria crotonensis, and Stephanodiscus niagarae. C. bodanica abundances corresponded to high-light/low-N situations, whereas S. niagarae maxima were found in high-TN : TP/low-light conditions. F. crotonensis abundances were most strongly positively correlated with total Si : TP and TN : TP. Environmental correlations were generally in good agreement with the measured physiological requirements of these species. Additionally, local population maxima of major species of diatoms never coincided.Seasonal succession of phytoplankton has been extensively studied and is generally assumed to be a function of changing environmental variables, including but not limited to temperature, light, nutrients, mixing, and herbivory. A number of investigators have attempted to quantitatively correlate these environmental factors with individual species' abundance and relative dominance with a modest degree of success (Lund 1954;Reynolds 1976;Tilman 1977Tilman , 1982Talling 1987;Sommer 1993). Following these and other examples, we analyzed phytoplankton dynamics over one season in three lakes in the Greater Yellowstone Ecosystem (GYE) to determine whether species-specific patterns could be correlated with measured environmental parameters and whether these patterns were consistent with experimental observations of the physiology of particular species of phytoplankton.Mechanistic resource competition theory (Tilman 1982)Acknowledgments We thank J. Bognar for field assistance and Jackson Lake phytoplankton counts. Also, thanks to the entire staff of the National Park Service Aquatic Resources Office in Yellow...

A diatom record of late Holocene climate variation in the northern range of Yellowstone National Park, USA

“…In this case, the coincidence of increased benthic diatom abundance with times of prolonged summer stratification likely reflects high water clarity. This is consistent with the low summer nutrient concentrations in the epilimnion, as suggested by the dominance of Cyclotella species (see above), and with limnological studies of modern Yellowstone lakes that show high Secchi depth during times of summer stratification (Interlandi et al, 1999).…”

“…Both the species are extremely efficient under low-phosphorus conditions and, in the Yellowstone region lakes, increase in relative abundance after S. minutulus blooms (Interlandi et al, 1999) but prior to the onset of stratification. Thus, these species may be indicative of years of particularly long periods of isothermal mixing.…”

“…It often forms a layer of cells near the thermocline, where nitrogen is higher in concentration than in the rest of the water column. S. minutulus populations are characteristic of low N:P and Si:P ratios, and this species blooms, in Yellowstone lakes, in early spring during times of isothermal mixing (Kilham et al, 1996;Interlandi et al, 1999). Because S. minutulus and C. bodanica bloom during two different times of the year, spring and summer, the two species are never in direct competition for nutrients.…”

“…C. michiganiana occurrences of greater than 20% are the darkest gray (yellow) (zone 2, sub-zones 2B, 2D, and 2F). abundant, and overall phytoplankton biomass is low (Interlandi et al, 1999). In the Yellowstone region lakes, it is most common in the summer months during times of water-column stratification.…”

“…a Not used in the construction of the age-depth model. diatoms in Crevice Lake are most likely related to changes in water-column mixing and internal regeneration of phosphorus, rather than supply from the lake catchment (Theriot et al, 1997;Interlandi et al, 1999). During mixing, phosphorus is regenerated from the hypolimnion, which creates conditions favorable for species that can utilize the nutrient quickly or that require high phosphorus concentrations to flourish, such as S. minutulus or S. medius.…”