Ecology under lake ice Hampton, Stephanie E.; Galloway, Aaron W. E.; Powers, Stephen M. ...
Ecology letters,
January 2017, Letnik:
20, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Winter conditions are rapidly changing in temperate ecosystems, particularly for those that experience periods of snow and ice cover. Relatively little is known of winter ecology in these systems, ...due to a historical research focus on summer ‘growing seasons’. We executed the first global quantitative synthesis on under‐ice lake ecology, including 36 abiotic and biotic variables from 42 research groups and 101 lakes, examining seasonal differences and connections as well as how seasonal differences vary with geophysical factors. Plankton were more abundant under ice than expected; mean winter values were 43.2% of summer values for chlorophyll a, 15.8% of summer phytoplankton biovolume and 25.3% of summer zooplankton density. Dissolved nitrogen concentrations were typically higher during winter, and these differences were exaggerated in smaller lakes. Lake size also influenced winter‐summer patterns for dissolved organic carbon (DOC), with higher winter DOC in smaller lakes. At coarse levels of taxonomic aggregation, phytoplankton and zooplankton community composition showed few systematic differences between seasons, although literature suggests that seasonal differences are frequently lake‐specific, species‐specific, or occur at the level of functional group. Within the subset of lakes that had longer time series, winter influenced the subsequent summer for some nutrient variables and zooplankton biomass.
Animals can be important in modulating ecosystem-level nutrient cycling, although their importance varies greatly among species and ecosystems. Nutrient cycling rates of individual animals represent ...valuable data for testing the predictions of important frameworks such as the Metabolic Theory of Ecology (MTE) and ecological stoichiometry (ES). They also represent an important set of functional traits that may reflect both environmental and phylogenetic influences. Over the past two decades, studies of animal-mediated nutrient cycling have increased dramatically, especially in aquatic ecosystems. Here we present a global compilation of aquatic animal nutrient excretion rates. The dataset includes 10,534 observations from freshwater and marine animals of N and/or P excretion rates. These observations represent 491 species, including most aquatic phyla. Coverage varies greatly among phyla and other taxonomic levels. The dataset includes information on animal body size, ambient temperature, taxonomic affiliations, and animal body N:P. This data set was used to test predictions of MTE and ES, as described in Vanni and Mclntyre (2016; Ecology DOI: 10.1002/ecy.1582).
Ecological shifts in shallow lakes from clear-water macrophyte-dominated to turbid-water phytoplankton-dominated are generally thought of as rapid short-term transitions. Diatom remains in sediment ...records from shallow lakes in the Prairie Pothole Region of North America provide new evidence that the long-term ecological stability of these lakes is defined by the legacy of large regime shifts. We examine the modern and historical stability of 11 shallow lakes. Currently, four of the lakes are in a clear-water state, three are consistently turbid-water, and four have been observed to change state from year to year (transitional). Lake sediment records spanning the past 150-200 yr suggest that (1) the diatom assemblage is characteristic of either clear or turbid lakes, (2) prior to significant landscape alteration, all of the lakes existed in a regime of a stable clear-water state, (3) lakes that are currently classified as turbid or transitional have experienced one strong regime shift over the past 150-200 yr and have since remained in a regime where turbid-water predominates, and (4) top-down impacts to the lake food-web from fish introductions appear to be the dominant driver of strong regime shifts and not increased nutrient availability. Based on our findings we demonstrate a method that could be used by lake managers to identify lakes that have an ecological history close to the clear-turbid regime threshold; such lakes might more easily be returned to a clear-water state through biomanipulation. The unfortunate reality is that many of these lakes are now part of a managed landscape and will likely require continued intervention.
Shallow lakes process large amounts of carbon (C) via gross primary production (GPP) and respiration (R), but C fluxes are highly variable among lakes. We used a two-prong approach to determine ...whether C fluxes differed between two alternative stable states observed in shallow lakes. First, we used a replicated whole-lake experiment where we manipulated fish densities in four experimental lakes to induce shifts from the phytoplankton-dominated state (turbid state) to a submersed macrophyte-dominated state (clear state), and determined whether whole-lake GPP, R, and net aquatic production (NAP) changed in response to the manipulation. We also compared lake metabolism in the four experimental lakes to four lakes in a turbid state and four lakes in a clear state. Second, we used sediment cores from 68 shallow lakes to test whether modern burial rates of organic C differed between lakes in clear and turbid states. Biomanipulation in the experimental lakes reduced abundance of fish and phytoplankton and increased abundance of aquatic invertebrates and submerged macrophytes. However, there was no significant change in GPP, R, or NAP. Similarly, GPP, R, and NAP did not differ among experimental lakes, turbid-state lakes, or clear-state lakes. Lastly, organic C burial in sediments did not differ between lakes in clear vs. turbid states, though variability among sites was high. High light and nutrient availability facilitate rapid transitions between two alternative groups of competing, rapidly growing primary producers in shallow lakes. These characteristics facilitate relatively uniform C fluxes at the ecosystem scale despite substantial differences in community structure.
We collected two sediment cores and modern submerged aquatic plants and phytoplankton from two sub-basins of Lake Christina, a large shallow lake in west-central Minnesota, and used stable isotopic ...and elemental proxies from sedimentary organic matter to explore questions about the pre- and post-settlement ecology of the lake. The two morphologically distinct sub-basins vary in their sensitivities to internal and external perturbations offering different paleoecological information. The record from the shallower and much larger western sub-basin reflects its strong response to internal processes, while the smaller and deeper eastern sub-basin record primarily reflects external processes including important post-settlement land-use changes in the area. A significant increase in organic carbon accumulation (3–4 times pre-settlement rates) and long-term trends in δ13C, organic carbon to nitrogen ratios (C/N), and biogenic silica concentrations shows that primary production has increased and the lake has become increasingly phytoplankton-dominated in the post-settlement period. Significant shifts in δ15N values reflect land-clearing and agricultural practices in the region and support the idea that nutrient inputs have played an important role in triggering changes in the trophic status of the lake. Our examination of hydroclimatic data for the region over the last century suggests that natural forcings on lake ecology have diminished in their importance as human management of the lake increased in the mid-1900s. In the last 50years, three chemical biomanipulations have temporarily shifted the lake from the turbid, algal-dominated condition into a desired clear water regime. Two of our proxies (δ13C and BSi) measured from the higher resolution eastern basin record responded significantly to these known regime shifts.
► We explore the sediment geochemistry from Lake Christina's two distinct sub-basins. ► Our geochemical data show significant changes in the lake after settlement. ► δ15N values were significantly influenced by land use changes. ► BSi and δ13C values in lake sediments responded to known regime shifts.
The concept of new and regenerated production has been used extensively in marine ecosystems but rarely in freshwaters. We assessed the relative importance of new and regenerated phosphorus (P) in ...sustaining phytoplankton production in Acton Lake, a eutrophic reservoir located in southwestern Ohio, USA. Sources of nutrients to the euphotic zone, including watershed loading, fluxes from sediments, and excretion by sediment-feeding fish (gizzard shad,
Dorosoma cepedianum
), were considered sources of new P input that support new primary production and were quantified over the course of a growing season. Regenerated production was estimated by the difference between new and total primary production. New production represented 32%-53% of total primary production, whereas regenerated production represented 47%-68% of total primary production. P excretion by gizzard shad supplied 45%-74% of new P and 24% of P required for total production. In summary, fluxes of P from the watershed and those from sediment-feeding fish need to be considered in strategies to reduce eutrophication in reservoir ecosystems.
Winter Oxygen Regimes in Clear and Turbid Shallow Lakes Rabaey, Joseph S.; Domine, Leah M.; Zimmer, Kyle D. ...
Journal of geophysical research. Biogeosciences,
March 2021, 2021-03-00, Letnik:
126, Številka:
3
Journal Article
Recenzirano
Dissolved oxygen controls important processes in lakes, from chemical reactions to organism community structure and metabolism. In shallow lakes, small volumes allow for large fluctuations in ...dissolved oxygen concentrations, and the oxygen regime can greatly affect ecosystem‐scale processes. We used high frequency dissolved oxygen measurements to examine differences in oxygen regimes between two alternative stable states that occur in shallow lakes. We compared annual oxygen regimes in four macrophyte‐dominated, clear state lakes to four phytoplankton‐dominated, turbid state lakes by quantifying oxygen concentrations, anoxia frequency, and measures of whole‐lake metabolism. Oxygen regimes were not significantly different between lake states throughout the year except for during the winter under‐ice period. During winter, clear lakes had less oxygen, higher frequency of anoxic periods, and higher oxygen depletion rates. Winter oxygen depletion rates correlated positively with peak summer macrophyte biomass. Due to lower levels of oxygen, clear shallow lakes may experience anoxia more often and for longer duration during the winter, increasing the likelihood of fish winterkills. These observations have important implications for shallow lake management, which typically focuses efforts on maintaining the clearwater state.
Plain Language Summary
In lakes, the amount of oxygen dissolved in the water has a profound impact on lake processes, from chemical reactions to the varieties and quantities of organisms present. In shallow lakes, the amount of dissolved oxygen can vary greatly due to the differences in the rates of production, mostly through photosynthesis, and consumption, mostly through respiration. In this study, we compared dissolved oxygen availability seasonally between two common states found in shallow lakes; a turbid, low clarity state dominated by phytoplankton, and a clear state dominated by submersed aquatic plants. Patterns of oxygen were similar between the two lakes states in all seasons except winter. During the winter under‐ice period, clear lakes had significantly less oxygen compared to turbid lakes, and lost oxygen at a faster rate through the winter. The lower levels of oxygen in clear lakes during the winter could affect many lake processes, such as the winterkill of fish. Lake managers typically try to maintain shallow lakes in the clear state because of better water quality and increased wildlife diversity. Winter fish kills could help maintain lakes in the clear state, but may also select for rough fish that can drive shifts to the turbid state.
Key Points
Winter oxygen regimes differed between clear and turbid shallow lakes
Clear shallow lakes had significantly higher oxygen depletion rates under ice cover than turbid shallow lakes
Oxygen depletion rates were highly correlated with summer macrophyte biomass
To address how various environmental parameters control or constrain planktonic respiration (PR), we used geometric scaling relationships and established biological scaling laws to derive ...quantitative predictions for the relationships among key drivers of PR. We then used empirical measurements of PR and environmental (soluble reactive phosphate SRP, carbon DOC, chlorophyll a Chl-a), and temperature) and landscape parameters (lake area LA and watershed area WA) from a set of 44 lakes that varied in size and trophic status to test our hypotheses. We found that landscape-level processes affected PR through direct effects on DOC and temperature and indirectly via SRP. In accordance with predictions made from known relationships and scaling laws, scale coefficients (the parameter that describes the shape of a relationship between 2 variables) were found to be negative and have an absolute value <1. Biological parameters scaled positively with physical and chemical processes in accordance with those predicted from theory or previous studies (i.e., temperature >1, others <1). We also found evidence of a significant relationship between temperature and SRP. Because our dataset included measurements of respiration from small pond catchments to the largest body of freshwater on the planet, Lake Superior, these findings should be applicable to controls of PR for the great majority of temperate aquatic ecosystems.
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