Progress 10/01/04 to 09/30/07
Outputs
OUTPUTS: Our objective was to understand the factors leading to the presence of a clear-water phase (CWP) in Oneida and Onondaga Lakes, New York, and the annual variation in the CWP. Nearly all experimental research was carried out at Oneida Lake because the restoration of zooplanktivorous Alewife to Onondaga Lake caused the elimination of Daphnia and the CWP from this lake 2005-2007. Research on Oneida Lake proceeded along two avenues. (1) Laboratory experiments defined the suitability of algae for the growth and reproduction of Daphnia present at the start and end of the CWP. Ninety 250-ml tubes with mesh bottoms containing 5-10 Daphnia were suspended in tanks of filtered lake water. A food suspension (lab-cultured algae or lake algae) was dripped into each tube. Algal quality was assessed by measuring the growth rates of the Daphnia (from newly hatched to 4 days old) at 20 oC. To test for Daphnia genetic variation in ability to grow on algae from different seasons, we carried out
growth measurements on 10 different Daphnia genotypes. At 3 times (spring bloom, during the maximum water clarity, and late summer) in each of 2 years (2005 and 2006), we measured growth rates, g(j), on 3 replicates of 6 Daphnia for each of 10 clones feeding on 3 different food types: algae from the lake both in natural concentration and concentrated to 1 mg/L (a density sufficient to saturate feeding rate), and a laboratory culture of algae known to be a good food source fed at 1 mg carbon/L. At each time, we analyzed lake algae for food quality: fatty acid content, carbon: phosphorus, carbon: nitrongen and chlorophyll concentration. In general g(j) increased as a function of algal density in spring and CWP. In summer food quality was low due to cyanobacteria and Daphnia growth rate was depressed. During the spring bloom, lake-algal food quality was greater than for our reference (lab) alga. Clones differed in their response to changes in food quality and density, but not as a
function of the time of year that the clones were collected. (2) We used statistical analysis of the long-term data sets to explore relationships between the timing of onset, duration and amplitude, and timing of termination of the CWP with the harshness of the preceding winter, nutrient concentrations at spring turnover, algal biomass during the spring bloom, algal and Daphnia species composition throughout the CWP, and the timing and magnitude of the increase in the YOY fish and predatory invertebrates. Analyses showed that winter conditions have an indirect impact on CWP mediated through the food chain: effects on the algal food resource of the Daphnia. We have categorizing all algal taxa according to their quality as food for Daphnia to find which groups are most important in determining water clarity. Together, parts (1) and (2) of this work show that clear water periods in Oneida Lake are caused by seasonally important Daphnia grazing, the extent of which is determined by
seasonal changes in algal food quality. Annual variation in the timing of water clearing is caused in part by climate variation, especially the start of spring warming.
PARTICIPANTS: Nelson G. Hairston, Jr. (Professor & principal investigator): Designed study; participated in the set up and execution of all experiments; assessed long-term data set; participated in data analysis and write up. Edward L. Mills (Professor & co-principle investigator): Oversaw collection of long-term data set; provided insight into interpretation of long-term data set; provided logistical support; participated in discussion and analysis of data. Colleen M. Kearns (Research Support Specialist): Helped with design of experiments; oversaw and participated in execution of experiment; carried out chemical analyses; participated in data analysis and interpretation. Laura E. Jones (Research Associate): Led statistical analysis of long-term data set. Upstate Freshwater Institute: A private, not-for-profit research organization with long-term expertise on Onondaga Lake; provided the long-term data set for this lake as well as discussion and interpretation of these data; led
retrospective analysis of CWP in this lake.
TARGET AUDIENCES: As well as practicing scientists, this project is targeted at lake managers and members of the public concerned with lake environmental quality. The Upstate Freshwater Institute organizes an annual public meeting in Syracuse about research on Onondaga Lake. Hairston, Mills, Kearns and Jones regularly participate in these meetings, and in some years present results.
PROJECT MODIFICATIONS: At the start of this project, zooplanktivorous fish, Alewife, suddenly and unexpectedly became abundant in Onondaga Lake, and remained so for the duration of this project. The fish eliminated Daphnia from the water column of the lake making experimental study of their effect on water clearing events impossible, but showing quite convincingly that without Daphnia there is no clear-water phase in Onondaga Lake. This latter observation is the subject of a manuscript (co-authored by UFI, Hairston and Kearns), and of a public presentation at the annual Onondaga Conference (see Partner Organizations).
Impacts
The annual water-clearing event in lakes, known as the spring clear-water phase (CWP), is one of the most striking environmental patterns in many freshwater ecosystems. It is characterized by a sudden increase in water transparency (typically in May or June), persists for an extended period that varies from year to year, and then ends later in summer. It is important to understand the processes that produce this phenomenon because lake transparency impacts (1) the feeding efficiency and recruitment success of important sport fish populations, (2) the conditions for growth of nuisance rooted aquatic weeds, and (3) the suitability of lakes for swimming, pleasure boating, and a satisfying lake-shore experience. Where it occurs, the CWP impacts essential ecosystem processes in lakes including primary production at the base of the food chain, rates and routes of nutrient cycling in lakes, and the efficiency of energy and material transfer to higher trophic levels. The CWP
is fundamentally a single oscillation of a predator-prey cycle between algae (the prey) and grazing zooplankton (the predators) and as such provides an opportunity to apply basic ecological theory about consumer-resource interactions including the conditions leading to cycles, and factors that affect their timing, duration and magnitude. This research defined more precisely the factors leading to water clearing, its timing, magnitude and duration, and it identified some of the causes of year-to-year variation in these phenomena. Such knowledge provides a basis for managing lakes for water clarity and for anticipating the impacts of other lake management strategies.
Publications
- No publications reported this period
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Progress 01/01/06 to 12/31/06
Outputs
The objectives of this research are to understand the factors leading to the presence of a clear-water phase CWP in two lakes in upstate New York, Oneida Lake and Onondaga Lake, and the variation in the expression of the CWP. We use statistical analysis of the long-term data sets to explore relationships between the timing of onset, duration and amplitude, and timing of termination of the CWP with the harshness of the preceding winter; nutrient concentrations at spring turnover, algal biomass during the spring bloom, algal and Daphnia species composition throughout the CWP; and the timing and magnitude of the increase in the YOY fish and predatory invertebrates. In initial analyses winter conditions have an indirect impact on CWP mediated through the food chain: effects on the algal food resource of the Daphnia. For further analysis we are working through the algal data categorizing all taxa according to their quality as food for Daphnia. Laboratory experiments have
been undertaken to define the suitability of algal abundance and quality for the growth and reproduction of Daphnia genotypes present at the start and end of the CWP. Our laboratory set-up consists of a large tank containing filtered lake water in which 45 250-ml tubes are suspended upright with 75 percent of each tube submersed beneath the water. Each tube, designed to contain 5-10 Daphnia, is open at the top and has a mesh bottom. A food suspension of either laboratory-cultured algae or lake algae is dripped into the top of a tube providing a steady supply of food to the Daphnia. The quality of the algae is assessed by measuring the growth rates of the animals (from newly hatched to 4 days old at 20 oC). Food is dripped into each tube as an algal suspension drawn from a reservoir using a peristaltic pump. To test for genetic variation within the Daphnia population for ability to grow on algae of different quality that occur in different seasons, we carry out growth measurements on
10 different Daphnia genotypes. Our experimental set-up allows measurements on 3 replicates of 6 Daphnia each for each of 10 clones feeding on three different food types (90 tubes): algae from the lake both in natural concentration and concentrated to 1 mg/L, a density sufficient to saturate feeding rate, and a laboratory culture of algae known to be a good food source fed at 1 mg carbon/L. We measured growth rates, g(j), at 3 times of the year in both 2005 and 2006: during the spring bloom, during the maximum water clarity, and late summer. At the time of each of these measurements, we collected lake algae for analysis of various measures of algal food quality including fatty acid content, carbon: phosphorus, carbon: nitrogen and chlorophyll concentration. In general, g(j) increased as a function of algal density regardless of algal type present. During spring bloom, lake-algal food quality was greater than for our reference (lab) alga; during the CWP and after food quality in 2006
was lower than the reference alga. Clones differ in their response to changes in food quality and density, but not apparently as a function of time of year that the clones were collected.
Impacts
One of the most striking patterns in many lake ecosystems is the annual water-clearing event, known as the spring clear-water phase (CWP). It is characterized by a sudden increase in water transparency (typically in May or June) that persists for an extended period and then ends later in summer. It is important to understand the processes that produce this phenomenon because lake transparency impacts, the feeding efficiency and recruitment success of important sport fish populations, the conditions for growth of nuisance rooted aquatic weeds, and the suitability of lakes for swimming, pleasure boating, and a satisfying lake-shore experience. Where it occurs, the CWP impacts essential ecosystem processes in lakes including primary production at the base of the food chain, rates and routes of nutrient cycling in lakes, and the efficiency of energy and material transfer to higher trophic levels. The CWP is fundamentally a single oscillation of a predator-prey cycle
between algae (the prey) and grazing zooplankton (the predators) and as such provides an opportunity to apply basic ecological theory about consumer-resource interactions including the conditions leading to cycles, and factors that affect their timing, duration and magnitude.
Publications
- Hairston, N.G., Jr., Ellner, S.P., Geber, M.A., Yoshida, T., and Fox, J.A. 2005. Rapid evolution and the convergence of ecological and evolutionary time. Ecology Letters 8:1114-1127.
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Progress 01/01/05 to 12/31/05
Outputs
It is the objectives of this research to understand the factors leading to the presence of a clear-water phase (CWP) in two lakes in upstate New York, Oneida Lake and Onondaga Lake, and the year-to-year and between-lake variation in the expression of the CWP. We are accomplishing this understanding through (1) a statistical analysis of the long-term data sets, and (2) experimental measurements of biological processes. The data sets that exist for the two lakes are being used to explore relationships between the timing of onset, duration and amplitude, and timing of termination of the CWP with the harshness of the preceding winter, nutrient concentrations at spring turnover, algal biomass during the spring bloom, algal and Daphnia species composition throughout the CWP, and the timing and magnitude of the increase in the YOY fish and predatory invertebrates. Initial analyses suggest that winter conditions have an indirect impact of CWP timing mediated through the food
chain, in particular though effects on the algal food resource of the Daphnia. Laboratory experiments are being undertaken to define the suitability of algal abundance and quality for the growth and reproduction of a sampling of Daphnia genotypes present at the start of the CWP. During the first spring and summer of research (2005), we constructed a laboratory set-up for the study of Daphnia growth response to food quality. The set-up consists of a large tank containing filtered lake water in which 45 250-ml tubes are suspended upright with 75 percent of each tube submersed beneath the water. Each tube, designed to contain 5 to 10 Daphnia, is open at the top and has a mesh bottom. A food suspension of either laboratory-cultured algae or lake algae is dripped into the top of a tube providing a steady supply of food to the Daphnia. The quality of the algae is assessed by measuring the growth rates of the animals (from newly hatched to 4 days old at 20 oC). Food is dripped into each tube
as an algal suspension drawn from a reservoir using a peristaltic pump. To test for genetic variation within the Daphnia population for ability to grow on algae of different quality that occur in different seasons, we carry out growth measurements on 10 different Daphnia genotypes. Our experimental set-up allows measurements on 3 replicates of 6 Daphnia each for each of 10 clones feeding on three different food types (90 tubes): algae from the lake both in natural concentration and concentrated to 1 mg/L, a density sufficient to saturate feeding rate, and a laboratory culture of algae known to be a good food source fed at 1 mg carbon/L. We measured growth rates at 3 times of the year: during the spring bloom, during the maximum water clarity, and late summer. At the time of each of these measurements, we collected lake algae for analysis of various measures of algal food quality including fatty acid content, carbon:phosphorus, carbon:nitrongen and chlorophyll concentration. We are
currently analyzing the results from last summers research.
Impacts
One of the most striking patterns in many lake ecosystems is the annual water-clearing event, known as the spring clear-water phase (CWP). It is characterized by a sudden increase in water transparency (typically in May or June) that persists for an extended period and then ends later in summer. It is important to understand the processes that produce this phenomenon because lake transparency impacts, the feeding efficiency and recruitment success of important sport fish populations, the conditions for growth of nuisance rooted aquatic weeds, and the suitability of lakes for swimming, pleasure boating, and a satisfying lake-shore experience. Where it occurs, the CWP impacts essential ecosystem processes in lakes including primary production at the base of the food chain, rates and routes of nutrient cycling in lakes, and the efficiency of energy and material transfer to higher trophic levels. The CWP is fundamentally a single oscillation of a predator-prey cycle
between algae (the prey) and grazing zooplankton (the predators) and as such provides an opportunity to apply basic ecological theory about consumer-resource interactions including the conditions leading to cycles, and factors that affect their timing, duration and magnitude.
Publications
- Hairston, N.G., Jr., Kearns, C.M., Demma, L.P. and Effler, S.W. 2005. Species-specific Daphnia phenotypes: A history of industrial pollution and pelagic ecosystem response. Ecology 86:1669-1678.
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