Contrasts between dystrophic and clearwater lakes in the long‐term effects of acidification on cladoceran assemblages

1. Most studies on zooplankton responses to acidification have focused on clearwater lakes with a dramatic acidification history. The role of dissolved organic carbon (DOC) in moderating zooplankton responses to acidification in naturally acidic, dystrophic lakes is less well understood and is partially impeded by a lack of baseline data. 2. Cladocera leave identifiable remains preserved in lake sediments that can be used to provide information on pre‐industrial species assemblages and their responses to environmental stressors such as acidification. Therefore, we used palaeolimnological approaches to track cladoceran assemblage responses to acidification since c.1850 (inferred from sedimentary diatom assemblages) in three acidified lakes in Kejimkujik National Park (Nova Scotia, Canada) that differ markedly in DOC content. These include two highly dystrophic lakes (Kejimkujik and Pebbleogittch lakes), and one clearwater lake (Beaverskin Lake). 3. In dystrophic Pebbleogittch Lake, an increase in the acid‐tolerant, jelly‐clad, pelagic taxon Holopedium glacialis occurred coincident with diatom‐inferred pH (DI‐pH) declines, but no other notable cladoceran assemblage shifts occurred. Similarly, Cladocera assemblages did not appear to respond to lakewater acidification in dystrophic Kejimkujik Lake. 4. In contrast, in the clearwater Beaverskin Lake, several observed shifts in cladoceran assemblage corresponded to DI‐pH declines, including an increase in the proportion of littoral taxa and an increase in Hill’s N2 species diversity. This may indicate increased water clarity as a result of acidification‐related decreases in DOC, which may have enhanced growth of emergent aquatic macrophytes and improved visibility for planktivorous fish, leading to increased predation on pelagic taxa. Species shifts within the littoral assemblage of Beaverskin Lake may reflect the differing tolerances of littoral taxa to low pH and aluminium toxicity. 5. Overall, our results suggest that cladoceran assemblages in naturally acidic, dystrophic lakes may be resilient against additional pH declines related to industrial emissions of acidifying agents, as dystrophic lakes are less vulnerable to increased aluminium toxicity and acidification‐induced increases in water clarity and often have a pre‐industrial cladoceran assemblage already adapted to acidic conditions.     

The zooplankton-phytoplankton interface in lakes of contrasting trophic status: an experimental comparison

We report here the results of an experimental study designed to compare algal responses to short-term manipulations of zooplankton in three California lakes which encompass a broad range of productivity (ultra-oligotrophic Lake Tahoe, mesotrophic Castle Lake, and strongly eutrophic Clear Lake). To assess the potential strength of grazing in each lake, we evaluated algal responses to a 16-fold range of zooplankton biomass. To better compare algal responses among lakes, we determined algal responses to grazing by a common grazer (Daphnia sp.) over a range ofDaphnia densities from 1 to 16 animals per liter. Effects of both ambient grazers andDaphnia were strong in Castle Lake. However, neither ambient zooplankton norDaphnia had much impact on phytoplankton in Clear Lake. In Lake Tahoe, no grazing impacts could be demonstrated for the ambient zooplankton butDaphnia grazing had dramatic effects. These results indicate weak coupling between phytoplankton and zooplankton in Clear Lake and Lake Tahoe, two lakes which lie near opposite extremes of lake trophic status for most lakes. These observations, along with work reported by other researchers, suggest that linkages between zooplankton and phytoplankton may be weak in lakes with either extremely low or high productivity. Biomanipulation approaches to recover hypereutrophic lakes which aim only to alter zooplankton size structure may be less effective if algal communities are dominated by large, inedible phytoplankton taxa.     

The Contribution of Ciliated Protozoa to Zooplankton Biomass in an Acidic, Subtropical Lake

Ciliated protozoa accounted for up to 50% of the mean daily zooplankton biomass in McCloud Lake, a small (5 ha), oligotrophic, acidic (pH 4.7) lake in north-central Florida. Food resources (algae and bacterioplankton) were limiting for crustacean and rotifer zooplankton during much of the year. Myxotrophic ciliates were a dominant component of the planktonic food web. Stentor niger , an uncommon species in the plankton of lakes, dominated the ciliate assemblage and usually comprised >90% of total ciliate biomass. Stentor niger always contained high densities of photosynthetic zoochlorellae and contributed an estimated 30% to the total autotrophic biomass.     

Algal picoplankton production and contribution to food-webs in oligotrophic British Columbia lakes

The pelagic communities of two contrasting oligotrophic lakes in British Columbia were studied to determine why an interior, dimictic lake (Quesnel) supports a greater biomass of zooplankton and produces larger planktivorous sockeye salmon (Oncorhynchus nerka) than a coastal warm-monomictic lake (Sproat). The ultra-oligotrophic status and differing planktivore densities in Sproat Lake increased the relative importance of algal picoplankton, diminished the abundance of large zooplankton, and increased the significance of rotifers and other small-bodied zooplankton. These picoplankton based food webs result in longer, indirect and less efficient pathways of carbon flow from phytoplankton to fish. In contrast, Quesnel Lake is a more productive oligotrophic lake and its pelagic food webs are based more on nanoplankton and small microphytoplankton that support larger-bodied zooplankton (Daphnia, Diaptomus), and a more direct and efficient two-step transfer to fish. The greater variability of the annual recruitment of sockeye fry in interior lakes may keep zooplankton communities in a non-steady state, this in turn may perpetuate the occurrence of quadrennial cyclic dominance in adult salmon returning to these systems.     

Biomanipulation development in Norway

Since 1974 several studies have been carried out in Norway to investigate the interactions between planktivorous fish, zooplankton, phytoplankton and water chemistry. Since 1978 a long-term national research program has been conducted by the Norwegian Council for Scientific and Industrial Research (NTNF). In this program several whole lake manipulations of the fish stocks have been performed to test hypotheses about trophic interactions. It was predicted that manipulations of planktivorous fish populations, might also improve water quality in lakes undergoing eutrophication. Two examples are given to illustrate the achieved results. I: Whole lake fertilization experiment (1974–1978) carried out by Langeland and Reinertsen. The results revealed the importance of top-down effects in the lake ecosystem. When cladocerans dominated, the zooplankton community was able to maintain a more or less constant phytoplankton biomass and a rather low phytoplankton production even when nutrient levels were increased. During years with rotifer dominance, algal biomass and productivity increased, despite the low amounts of added nutrients. II: Experiment performed by Reinertsen, Jensen, Koksvik, Langeland and Olsen in the eutrophic Lake Haugatjern, total elimination of the fish populations by rotenone in late 1980, resulted in a 4-fold decrease in the algal biomass. The species composition changed from the dominance of large-sizedAnabaena flos-aquae andStaurastrum luetkemuelleri to smaller, fastgrowing species and gelatinous green algae. The results are discussed in relation to management of inland waters by combined techniques of biomanipulation and reduced external nutrient supply which increase food-chain efficiency.     

Community resistance and change to nutrient enrichment and fish manipulation in a vegetated lake littoral

1. High biomass of macrophytes is considered important in the maintenance of a clear‐water state in shallow eutrophic lakes. Therefore, rehabilitation and protection of aquatic vegetation is crucial to the management of shallow lakes. 2. We conducted field mesocosm experiments in 1998 and 1999 to study community responses in the plant‐dominated littoral zone of a lake to nutrient enrichment at different fish densities. We aimed to find the threshold fish biomass for the different nutrient enrichment levels below which large herbivorous zooplankton escapes control by fish. The experiments took place in the littoral of Lake Vesijärvi in southern Finland and were part of a series of parallel studies carried out jointly at six sites across Europe. 3. In 1998, when macrophyte growth was poor, a clear‐water state with low phytoplankton biomass occurred only in unenriched mesocosms without fish or with low fish biomass (4 g fresh mass m^?2). Both nutrient enrichment and high fish biomass (20 g fresh mass m^?2) provoked a turbid water state with high planktonic and periphytic algal biomass. The zooplankton community was dominated by rotifers and failed to control the biomass of algae in nutrient enriched mesocosms. The littoral community thus had low buffer capacity against nutrient enrichment. 4. In 1999, macrophytes, especially free‐floating Lemna trisulca L., grew well and the zooplankton community was dominated by filter‐feeding cladocerans. The buffer capacity of the littoral community against nutrient enrichment was high; a clear‐water state with low phytoplankton biomass prevailed even under the highest nutrient enrichment. High grazing rates by cladocerans, together with reduced light penetration into the water caused by L. trisulca, were apparently the main mechanisms behind the low algal biomass. 5. Effects of fish manipulations were less pronounced than effects of nutrient enrichment. In 1999, clearance rates of cladocerans were similar in fish‐free and low‐fish treatments but decreased in the high‐fish treatment. This suggests that the threshold fish biomass was between the low‐ and high‐fish treatments. In 1998, such a threshold was found only between fish‐free and low‐fish treatments. 6. The pronounced difference in the observed responses to nutrient enrichment and fish additions in two successive years suggests that under similar nutrient conditions and fish feeding pressure either clear or turbid water may result depending on the initial community structure and on weather.     

A comparison of zooplankton densities and biomass in Lakes Peipsi and Võrtsjärv (Estonia): rotifers and crustaceans versus ciliates

The abundance and biomass of ciliates, rotifers, cladocerans and copepods were studied in Lake Peipsi and Lake Võrtsjärv, both of which are shallow, turbid and large. Our hypothesis was that in a large shallow eutrophic lake, the ciliates could be the most important zooplankton group. The mean metazooplankton biomass was higher in Peipsi than in Võrtsjärv (mean values and SD, 1.8 ± 0.7 and 1.3 ± 0.6 mg WM l^?1). In Peipsi, the metazooplankton biomass was dominated by filtrators that feed on large-sized phytoplankton and are characteristic of oligo-mesotrophic waters. In Võrtsjärv, the metazooplankton was dominated by species characteristic of eutrophic waters. The planktonic ciliates in both lakes were dominated by oligotrichs. The biomass of ciliates was much greater in Võrtsjärv (mean 2.3 ± 1.4 mg WM l^?1) than in Peipsi (0.1 ± 0.08 mg WM l^?1). Ciliates formed about 60% of the total zooplankton biomass in Võrtsjärv but only 6% in Peipsi. Thus, the food chains in the two lakes differ: a grazing food chain in Peipsi and a detrital food-chain in Võrtsjärv. Consequently, top-down control of phytoplankton can be assumed to be much more important in Peipsi than in Võrtsjärv. When the detrital food chain prevails, the planktonic ciliates become the most important zooplankton group in shallow, eutrophic and large lake. Neglecting protozooplankton can result in serious underestimates of total zooplankton biomass since two-thirds of the zooplankton biomass in Võrtsjärv comprises ciliates.     

Environmental factors influencing zooplankton species composition of lakes in north-central Ontario,Canada

To assess the relative importance of lake chemistry, morphometry and zoogeography on limnetic zooplankton, we collected zooplankton, water, and morphometric data from 132 headwater Canadian Shield lakes in 6 regions across north-central Ontario. A subset of these lakes (n = 52) were fished with gill nets. We clustered lakes based on their zooplankton species composition (presence/absence). Discriminant analysis was employed to determine how well lake characteristics could predict zooplankton community types. Correct classification of zooplankton communities for three models ranged from 72 to 91%. Lake size, lake location, and buffering capacity were ranked as the most important factors separating lake groups. Fish abundance (CPUE) was not significant in distinguishing between zooplankton communities. Though the range of lake sizes was limited (1–110 ha), larger lakes tended to support more species. Lake location (zoogeography) also influenced species composition patterns. Although Algoma lakes tended to be larger (\-x = 18.0 ha, other lakes \-x = 2.5 ha), they supported relatively depauperate zooplankton communities. Buffering capacity was ranked third in the discriminant analysis models, but pH and alkalinity were not significantly different between lake groups.     

Biological recovery of the Bohemian Forest lakes from acidification

A limnological survey of eight small, atmospherically acidified, forested glacial lakes in the Bohemian Forest (?umava, Böhmerwald) was performed in September 2003. Water chemistry of the tributaries and surface layer of each lake was determined, as well as species composition and biomass of the plankton along the water column, and littoral macrozoobenthos to assess the present status of the lakes. The progress in chemical reversal and biological recovery from acid stress was evaluated by comparing the current status of the lakes with results of a survey four years ago (1999) and former acidification data since the early 1990s. Both the current chemical lake status and the pelagic food web structure reflected the acidity of the tributaries and their aluminium (Al) and phosphorus (P) concentrations. One mesotrophic (Ple?né jezero) and three oligotrophic lakes (?erné jezero, ?ertovo jezero, and Rachelsee) are still chronically acidified, while four other oligotrophic lakes (Kleiner Arbersee, Prá?ilské jezero, Grosser Arbersee, and Laka) have recovered their carbonate buffering system. Total plankton biomass was very low and largely dominated by filamentous bacteria in the acidified oligotrophic lakes, while the mesotrophic lake had a higher biomass and was dominated by phytoplankton, which apparently profited from the higher P input. In contrast, both phytoplankton and crustacean zooplankton accounted for the majority of plankton biomass in the recovering lakes. This study has shown further progress in the reversal of lake water chemistry as well as further evidence of biological recovery compared to the 1999 survey. While no changes occurred in species composition of phytoplankton, a new ciliate species was found in one lake. In several lakes, this survey documented a return of zooplankton (e.g., Cladocera: Ceriodaphnia quadrangula and Rotifera: three Keratella species) and macrozoobenthos species (e.g., Ephemeroptera and Plecoptera). The beginning of biological recovery has been delayed for ～20 years after chemical reversal of the lakes.     

Lake Chapo: a baseline study of a deep, oligotrophic North Patagonian lake prior to its use for hydroelectricity generation: II. Biological properties

The present paper focuses on the biological properties of Lake Chapo prior to the installation of a hydroelectric power station. Most of the biological parameters indicate that the lake is oligotrophic, i.e., it has very low values of chlorophyll a and primary production. The phytoplankton community of 73 species shows a predominance of only a few species in terms of density and biomass. The zooplankton community is poor in species, with one of the lowest densities measured in the North Patagonian lakes. The fish community is dominated by two introduced salmonid species. Comparison with other North Patagonian lakes reveals that Lake Chapo is the most oligotrophic.     

Zooplankton biomass dynamics in oligotrophic versus eutrophic conditions: a test of the PEG model

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Effects of planktivorous and benthivorous fish on organisms and water chemistry in eutrophic lakes

The effects of planktivorous and benthivorous fish on benthic fauna, zooplankton, phytoplankton and water chemistry were studied experimentally in two eutrophic Swedish lakes using cylindrical enclosures. In enclosures in both lakes, dense fish populations resulted in low numbers of benthic fauna and planktonic cladocerans, high concentration of chlorophyll, blooms of blue-green, algae, high pH and low transparency. In the soft-water Lake Trummen, total phosporus increased in the enclosure with fish, but in the hard-water Lake Bysjön total phosphorus decreased simultaneously with precipitation of calcium carbonate. Enclosures without fish had a higher abundance of benthic fauna and large planktonic cladocerans, lower phytoplankton biomass, lower pH and higher transparency.The changes in enclosures with fish can be described as eutrophication, and those in enclosures without fish as oligotrophication. The possibility of regulation of fish populations as a lake restoration method is discussed.This paper was presented at the XXth SIL Congress in Copenhagen in 1977.     

Sixty years of environmental change in the world's largest freshwater lake – Lake Baikal, Siberia

High-resolution data collected over the past 60 years by a single family of Siberian scientists on Lake Baikal reveal significant warming of surface waters and long-term changes in the basal food web of the world's largest, most ancient lake. Attaining depths over 1.6 km, Lake Baikal is the deepest and most voluminous of the world's great lakes. Increases in average water temperature (1.21 °C since 1946), chlorophyll a (300% since 1979), and an influential group of zooplankton grazers (335% increase in cladocerans since 1946) may have important implications for nutrient cycling and food web dynamics. Results from multivariate autoregressive (MAR) modeling suggest that cladocerans increased strongly in response to temperature but not to algal biomass, and cladocerans depressed some algal resources without observable fertilization effects. Changes in Lake Baikal are particularly significant as an integrated signal of long-term regional warming, because this lake is expected to be among those most resistant to climate change due to its tremendous volume. These findings highlight the importance of accessible, long-term monitoring data for understanding ecosystem response to large-scale stressors such as climate change.     

Copepods as environmental indicator in lakes: special focus on changes in the proportion of calanoids along nutrient and pH gradients

Copepods are important contributors to the zooplankton community in lakes. Being “sandwiched” between predators and resources, they are sensitive to changes in the environment. It has been proposed that the proportion of calanoids of total copepod abundance or biomass could be a valuable indicator of eutrophication. We investigated relationships between environmental factors and the abundance, biomass and size of calanoid and cyclopoid copepods as well as their proportions in summer in 68 Danish freshwater lakes (587 lake years) with contrasting nutrient levels and pH. When lake pH was?<?6.0, mean lake depth and trophic state were the most important factors and calanoids completely dominated the copepod community. In shallow lakes with a mean depth?<?2.5 m and with pH?>?6.0, the proportion of calanoids in terms of biomass decreased substantially with increasing phosphorus and chlorophyll a concentrations but stayed around 50% at?>?2.5 m depth irrespective of nutrient level. Time series of the lakes, recovering from eutrophication, confirmed this multi-lake pattern although the trajectory varied from lake to lake. We conclude that the proportion of calanoids in terms of biomass might be a valuable indicator of trophic state in shallow but not deep lakes and only when pH?>?6.

     

Grazing effects of a freshwater bivalve (Corbicula leana Prime) and large zooplankton on phytoplankton communities in two Korean lakes

This study examined the effects of a freshwater filter feeding bivalve (Corbicula leana Prime) and large zooplankton (>200 μm, mostly cladocerans and copepods) on the phytoplankton communities in two lakes with contrasting trophic conditions. A controlled experiment was conducted with four treatments (control, zooplankton addition, mussel addition, and both zooplankton and mussel addition), and each established in duplicate 10-l chambers. In both lakes there were significant effects of mussel grazing on phytoplankton density and biomass. The effects were greater in mesotrophic Lake Soyang than in hypertrophic Lake Ilgam. Effects of zooplankton grazing did not differ between these lakes, and zooplankton effects on phytoplankton were much less than the effects of mussels. Although mussels exerted a varying effect on phytoplankton according to their size, mussels reduced densities of almost all phytoplankton taxa. Total mean filtering rate (FR) of mussels in Lake Soyang was significantly greater than that in Lake Ilgam (p=0.002, n=5). Carbon fluxes from phytoplankton to mussels (977–2,379 μgC l^?1d^?1) and to zooplankton (76–264 μgC l^?1 d^?1) were always greater in Lake Ilgam due to the greater phytoplankton biomass (p<0.01, n=6). Based on the C-flux to biomass ratios, the mussels consumed 170–754% (avg. 412%) of phytoplankton standing stock in Lake Soyang, and 38–164% (avg. 106%) in Lake Ilgam per day. The C-flux to biomass ratio for mussels within each lake was much greater than for large zooplankton. Mussels reduced total phosphorus concentration by 5–34%, while increasing phosphate by 30–55% relative to the control. Total nitrogen also was reduced (by 9–25%), but there was no noticeable change in nitrate among treatments. The high consumption rate of phytoplankton by Corbicula leana even in a very eutrophic lake suggests that this mussel could affect planktonic and benthic food web structure and function by preferential feeding on small seston and by nutrient recycling. Control of mussel biomass therefore might be an effective tool for management of water quality in shallow eutrophic lakes and reservoirs in Korea.     

Seasonal and Spatial Overlap between Cladocerans in Humic Lakes

Seasonal and vertical distribution, migratory patterns and reproductive effort in coexisting cladocerans were investigated in three humic lakes with different, but low phytoplankton abundances and varying fish predation pressure. Seasonal and vertical habitat or niche overlap varied, but were high within most pairs of species in all localities. Migration was conspicuous in presence of planktivorous fish, less so in the fish free lake. Despite algal densities below incipient limiting level (30–200 μg C I⁻¹) and a low ratio (3–10) of algal to cladoceran biomass, zooplankton distribution and reproductive parameters were not clearly related to algal biomass. Bacterial biomass equalled 10–50% of phytoplankton biomass, while detritus by far was the largest of the particulate compartements. It was concluded that with a possible exception of the early summer algal bloom, additional carbon sources (bacteria, detritus) are important to cladoceran nutrition in these humic lakes. A large share of N- and P-poor detritus in the diet would give zooplankton productivity limitation by food quality in terms of elemental composition rather than food quantity. This would permit coexistence even of species with rather high food overlap, but give low production rates for all species in agreement with the observations.     

Response of a shallow Mediterranean lake to nutrient diversion: does it follow similar patterns as in northern shallow lakes?

1. In view of the paucity of data on the response of warm shallow lakes to reductions in nutrient loading, this paper presents a long‐term limnological data set to document changes in the food‐web of a shallow Mediterranean lake (Lake Albufera, Valencia, Spain) that has experienced reductions in phosphorus (P) (77%) and nitrogen (N) (24%) loading following sewage diversion. 2. Nine years after sewage diversion, P concentration in the lake was reduced by 30% but remained high (TP = 0.34 mg L^?1), although the mean water retention time in the lake was only 0.1 years. Nitrate concentrations did not significantly change, probably because the lake continued to receive untreated effluents from ricefields. 3. Chlorophyll a concentration was reduced by half (annual mean of 180 μg L^?1). Cyanobacteria abundance remained high but its composition changed towards smaller species, both filamentous and chroococcal forms. 4. Cladocera abundance increased and reached peaks twice a year (December to March and July to September). After nutrient reduction, short‐term clear‐water phases (up to 5 weeks) occurred during February to March in several years, concomitant with annual flushing of the lake and lower fish densities. The abundance of Cladocera in winter contrasted with the spring peaks observed in northern restored shallow lakes. The zooplankton to phytoplankton biomass ratio remained lower than in northern temperate shallow lakes, probably because of fish predation on zooplankton. 5. Improvement of the water quality of Lake Albufera remained insufficient to counteract littoral reed regression or improve underwater light allowing submerged plants re‐colonise the lake. 6. Sewage diversion from Lake Albufera impacted the food web through the plankton, but higher trophic levels, such as fish and waterfowl, were affected to a lesser degree. Although the fish species present in the lake are mainly omnivorous, long‐term data on commercial fish captures indicated that fish communities changed in response to nutrient level and trophic structure as has been observed in restored shallow lakes at northern latitudes. 7. Phosphorus concentrations produced similar phytoplankton biomass in Lake Albufera as in more northern shallow lakes with abundant planktivorous fish and small zooplankton. However, in Lake Albufera, high average concentrations were maintained throughout the year. Overall, results suggest that nutrient control may be a greater priority in eutrophicated warm shallow lakes than in similar lakes at higher latitudes.     

Interrelations between Microcystis and Cladocera in the highly Eutrophic Lake Kasumigaura,Japan

The zooplankton community in the highly eutrophic Lake Kasumigaura was investigated and its relation to a bloom of Microcystis was analyzed. The zooplankton community was dominated by small cladocerans, whose biomass and production became highest in summer, when Microcystis bloomed. The high cladoceran production is considered to depend on the production of colonial Microcystis, because the production of nannoplankton was apparently too low to ensure the cladoceran production. Microcystis cells were unsuitable as food for the cladocerans inhabiting Lake Kasumigaura, but became utilizable when decomposed. Decomposed Microcystis may be the main food for Cladocera in the lake in summer. High water temperatures occurring in summer probably promoted decomposition of the Microcystis, leading to increased production of the small cladocerans.     

Clay-Turbid Interactions May Not Cascade—A Reminder for Lake Managers

Food web management is a frequently used lake restoration method, which aims to reduce phytoplankton biomass by strengthening herbivorous zooplankton through reduction of planktivorous fish. However, in clay‐turbid lakes several factors may reduce the effectivity of food web management. Increasing turbidity reduces the effectivity of fish predation and weakens the link between zooplankton and phytoplankton. Therefore, the effects of fish stock manipulations may not cascade to lower trophic levels as expected. Additionally, in clay‐turbid conditions invertebrate predators may coexist in high densities with planktivorous fish and negate the effects of fish reductions. For instance, in the stratifying regions of the clay‐turbid Lake Hiidenvesi, Chaoborus flavicans is the main regulator of cladocerans and occupies the water column throughout the day, although planktivorous Osmerus eperlanus is very abundant. The coexistence of chaoborids and fish is facilitated by a metalimnetic turbidity peak, which prevents efficient predation by fish. In the shallow parts of the lake, chaoborids are absent despite high water turbidity. We suggest that, generally, the importance of invertebrate predators in relation to vertebrate predators may change along turbidity and depth gradients. The importance of fish predation is highest in shallow waters with low turbidity. When water depth increases, the importance of fish in the top‐down regulation of zooplankton declines, whereas that of chaoborids increases, the change along the depth gradient being moderate in clear‐water lakes and steep in highly turbid lakes. Thus, especially deep clay‐turbid lakes may be problematic for implementing food web management as a restoration tool.