Shallow lake ecology

1. Shallow lakes are often cited as classic examples of systems that exhibit trophic cascades but, whilst they provide good model systems with which to test general ecological theory and to assess long-term community change, their food web linkages have rarely been resolved, so changes associated with the structure and dynamics of the ecological network as a whole are still poorly understood.
2. We sought to redress this, and to demonstrate the potential benefits of integrating palaeolimnological and contemporary data, by constructing highly resolved food webs and stable isotope derived measures of trophic interactions and niche space, for the extant communities of two shallow U.K. lakes from different positions along a gradient of eutrophication. The contemporary surface sediment cladoceran and submerged macrophyte assemblages in the less enriched site, Selbrigg Pond, matched the palaeolimnological assemblages of the more enriched site, Felbrigg Hall Lake, in its more pristine state during the 1920s. Thus, Selbrigg was a temporal analogue for
Felbrigg, from which the consequences of long-term eutrophication on food web structure could be inferred. These data represent the first steps towards reconstructing not only past assemblages (i.e. nodes within a food web), but also past interactions (i.e. links within a food web): a significant departure from much of the previous research in palaeolimnology.
3. The more eutrophic food web had far fewer nodes and links, and thus a less reticulate network, than was the case for the more pristine system. In isotopic terms, there was vertical compression in d15N range (NR) and subsequent increased overlap in isotopic niche space, indicating increased trophic redundancy within Felbrigg. This structural change, which was associated with a greater channelling of energy through a smaller
number of nodes as alternative feeding pathways disappear, could lead to reduced dynamic stability, pushing the network towards further simplification. These changes reflected a general shift from a benthic-dominated towards a more pelagic system, as the plant-associated subweb eroded.
4. Although these data are among the first of their kind, the palaeo-analogue approach used here demonstrates the huge potential for applying food web theory to understand how and why these ecological networks change during eutrophication. Furthermore because of the rich biological record preserved in their sediments, shallow lakes represent potentially important models for examining long-term intergenerational dynamics, thereby providing a means by which models and data can be integrated on meaningful timescales – a goal that has long proved elusive in food web ecology.

At the end of the 1990s, the area between the villages of Stevensweert, Ohé and Laak was sacrificed for the excavation. The old layout disappeared, including the agricultural area, the Oude Maas and the Echterweerd. The location of the excavation became known under the name Stevol.
Before and after gravel extraction, there are two fundamentally different situations in the Stevol area. A lot disappeared, but there was also something in return: a pond that was redesigned into a nature reserve with the Molenplas in the middle. In the new area there is again a lot to experience in flora and fauna. This chapter provides an insight into the new situation.

The Water Framework Directive (WFD) requires that the European Union countries determine the biological state of their waters with respect to sites of high quality. Despite bioindicators have been widely applied in running waters and deep lakes throughout all Europe, little is known about their applicability in shallow lakes. In this context, the objective of this work is to check the effectiveness of epiphytic diatoms as indicators of the trophic state in six shallow lakes of León Province (NW Spain). Epiphyton was sampled from helophyte stems in six shallow lakes covering different ecological conditions. A significant correlation was found between the total nitrogen concentration and the diatom indices SPI (Specific Polluosensitivity Index) and BDI (Biological Diatom Index), this correlation being lower with respect to the total phosphorus concentration. The classification of the lakes according to the trophic and saprobic levels based on diatoms corresponds to that obtained from the analysis of the limnological and chemical parameters of the studied systems. Despite the use of these indices has been traditionally limited to rivers and channels, our results show the effectiveness of epiphytic diatoms as biological indicators of the quality of water in Mediterranean shallow lakes and the applicability of common diatom indices for biomonitoring purposes in these aquatic ecosystems.

"A pesar de la importancia socioeconómica de las actividades pesqueras que de forma ancestral se vienen realizando en el Lago de la Albufera de Valencia, documentadas al menos desde el siglo 13, existe un escaso conocimiento acerca de la evolución temporal, situación actual e importancia ecológica de su fauna piscícola. Los datos de que se dispone son en muchos casos antiguos e incompletos, y principalmente son datos cualitativos sobre la composición de especies o basados en capturas comerciales. El objetivo de este trabajo es determinar el estado actual y los cambios de estas asociaciones de especies desde los primeros registros en 1865, así como estimar su papel en la ecología y la conservación del lago. Para ello, se analizaron de forma exhaustiva los datos recogidos en la literatura, los procedentes de los registros de los pescadores, y además se llevó a cabo un estudio de campo de la ictiofauna presente durante el verano de 2000 y la primavera de 2002. Los resultados permiten constatar que: a) se ha producido un notable descenso en la riqueza de especies de peces en el lago, principalmente desde la década de 1950 hasta 2002; b) se observa un aumento notable de las poblaciones de especies introducidas, principalmente Gambusia holbrooki y Lepomis gibbosus, que han desplazado endemismos como Aphanius iberus, Barbus bocagei, Chondrostma arrigonis y Valencia hispanica; c) desde la década de 1950 las capturas de mugílidos se han incrementado (de 80 a 490 t/año), en detrimento de especies como Anguilla anguilla o Dicentrarchus labrax, que han descendido significativamente coincidiendo con la eutrofización del lago, la desaparición de la vegetación sumergida y como resultado de su sobrepesca en periodos anteriores; d) se observan ciclos estacionales en la composición específica de las capturas, asociadas a la dinámica poblacional de cada especie (característica de lagos costeros) y a la regulación del flujo hidrológico del lago para el cultivo del arroz. Las capturas fueron máximas entre octubre y enero, lo que permitió relajar la presión de depredación sobre el macrozooplancton, con consecuencias en la red trófica y en la transparencia del agua; e) se
observó una clara relación entre la fauna piscícola del Lago de la Albufera y sus cambios de estado trófico. El progresivo proceso de eutrofización antropogénica que sufre este ecosistema, la introducción incontrolada de especies exóticas y la escasa conservación y gestión del lago y de sus ecosistemas asociados, así como la de sus recursos pesqueros, se apuntan como algunas de las principales causas de los cambios producidos en su ictiofauna."

Se propone un método para la toma de muestras de diatomeas epífitas en lagos y lagunas con el fin de aplicar dichas comunidades algales en la determinación del estado ecológico de estos sistemas acuáticos de acuerdo con los requisitos de la Directiva Marco del Agua. La metodología se basa en el empleo de muestradores tipo Kornijów para la recolección del epifiton desarrollado sobre helófitos. Los resultados preliminares muestran la eficacia de este método en la evaluación de la calidad del agua. La aplicación de esta sencilla metodología permite el empleo de las diatomeas epífitas como indicadores biológicos de los medio lacustres, generando resultados reproducibles en el tiempo y basados en un protocolo común fácilmente aplicable.

We present an example of how an invasion by a non-native cyprinid (common bream, Abramis brama (Pisces: Cyprinidae), hereafter bream) in a natural shallow lake in southern Europe (Lake Montorfano, northern Italy) may have adversely affected the state of the lake’s ecosystem. In less than two decades, bream became the most abundant species and characterized by a stunted population with asymptotic length 33.5 cm, an estimated mean length at first maturity of 19.6 cm, a total mortality rate of 0.64 y-1 and a diet overwhelmingly dominated by microcrustaceans. Following bream establishment, nutrients and phytoplankton biomass rose, the proportion of Cyanobacteria by numbers increased markedly and water transparency decreased. Total zooplankton abundance increased with a marked increase in small cladocerans and copepods, whereas the abundance of large herbivorous cladocerans did not change. The coverage of submerged macrophytes declined, as did the abundance of native pelagic zooplanktivorous fish. The composition of the fish community shifted towards a higher proportion of zoobenthivorous species, such as bream and pumpkinseed (Lepomis gibbosus). Our results indicate that bream affected water quality through bottom-up mechanisms, while top-down effects were comparatively weak. Selective removal of bream and perhaps stocking of native piscivores might improve the ecological status of the lake.

We revealed 238 species and infraspecific taxa of algae and cyanobacteria in phytoplankton communities in lakes of the Regional Landscape Park “Slavyansky Resort”, Ukraine during 2007-2013 of the total 352 known in the region assigned to nine taxonomic Divisions with Bacillariophyta, Cyanoprocaryota, and Chlorophyta prevailing. The bio-indication methods applied for the first time characterizes the aquatic environments as slightly alkaline, medium-enriched with oxygen, temperate, clear to moderately polluted, of Water Quality Classes II-III, eutrophic, but with photosynthetic algal nutrition attesting to insignificant concentration of toxic substances despite a considerable anthropogenic impact. The algal diversity is depressed with salinity of the lakes. The statistical analysis defines two clusters, the northern with perennial lakes Ripne, Veysove, Garache, and Slipne, and southern of partially drained lakes Levadne, Chervone, and Lake. Aridity is a major factor of water chemistry inflicting high salinity and depletion of species diversity. Historically salinity might have played a leading role in shaping the algal communities of the region.

Unlike in deep stratified lakes, the assessment of eutrophication in shallow aquatic systems (i.e., wetlands, marshes, ponds) should be based on the interaction between water and sediment. The availability of P to primary producers is naturally higher in shallow systems, because the sediment plays an active part via adsorption, precipitation and release processes. Thus, many wetlands in protected areas are naturally eutrophic and have a high trophic status due to intrinsic features and thus, display a high concentration of total-P in the water without necessarily implying pollution or poor quality. We have provided a diagnostic tool based on the chemical equilibrium of dissolved reactive P (operationally-defined as o-P) between water and sediment that distinguish anthropogenic eutrophication from a background of natural eutrophy. When the P-binding capacity of the sediment becomes saturated, the o-P concentration increases in the water as long as both the biological uptake and the sediment adsorption are unable to cope with the rate of P-release from the sediment under a long-term P load (or severe anthropogenic eutrophication). In such conditions, we have found that the ratio of total-P/particulate-P exceeds 2.0 in the water, and have used this threshold to validate this tool in other sets of wetlands.

Fish communities of five shallow Spanish Mediterranean lakes were studied and stomach content analysed to determine the foraging pattern of each species and the influence on the lake food web. Lakes ranged from 0.5 to 2300 ha with less than 3 m mean depth, while the trophic state varied from mesotrophy to hypertrophy. We fished during summer 2000 and 2001, and for one lake also during spring 2002. Almost no piscivores species were recorded and in general omnivorous species dominated independently of lake trophic state. Fish dietary differences were found among lakes and prey availabilities. Maximum fish biomass and diversity were found in the Albufera lake, where mugilids (Mugil cephalus and Liza aurata) and Cyprinus carpio dominated. The other lakes had young populations of Atherina boyeri and Liza ramada, endemic species (Barbus guiraonis, Aphanius iberus) or introduced species (Lepomis gibbosus, Micropterus salmoides, Gambusia holbrooki). Fish were mainly detritivorous and shifted to zooplanktivorous depending on abundance of large zooplankton. Fish demographic changes and facultative preys influenced food webs of the lakes by both direct predation and indirect nutrient recycling from the sediment. Omnivorous structure of fish communities in these Mediterranean warmer lakes resembles that described in some food webs of tropical lakes. Bottom-up mechanisms seem to be more relevant in warmer lakes and submerged plants were special key factors to maintain clear waters in the study lakes.

Tributyltin (TBT) is an organotin compound used since the early 1960s as a biocide in boat antifouling paints. Its use has been linked to a host of negative effects in marine ecosystems including malformations and imposex in Mollusca and acute toxicity in many other aquatic animals. Yet, the consequences of TBT use in freshwaters are largely unknown. Here, for the first time we reveal that TBT may have caused hitherto unsuspected damage to freshwater ecosystems. Through an analysis of dated sediment cores collected from a system of recreationally boated, shallow lakes,weshow that first evidence of TBT is associated with a dramatic loss of submerged vegetation and
associated diverse animal communities. Cause and effect are difficult to unravel in our study. However, we hypothesize that TBT, through reducing populations of grazing organisms in lakes already affected by eutrophication, promoted the replacement of macrophytes by phytoplankton, ultimately leading to a regime shift in the ecosystem. Our findings may have parallels in freshwater ecosystems all over the world.

"The Water Framework Directive requires that the European Union countries
determine the biological state of their waters with respect to sites of high quality. Although bioindicators
have been widely applied in running waters and deep lakes throughout Europe, little
is known about their applicability in shallow lakes and wetlands. The objective of this work is to
check the effectiveness of epiphytic diatoms as indicators of the trophic state in two wetlands of
Álava Province (N Spain). Diatom and water chemical samples were collected during summer
and autumn 2007, following standard methodology. Stems of submerged macrophyte (Carex
riparia, Iris pseudacorus, Veronica anagallis-aquatica) were sampled in each lake. Based on
the number of statistically significant correlations between diatom indices and environmental
factors, the SID index was show as the most suitable method to assess nutrients within these
systems. SID was significantly correlated with TP, NTK and ammonium levels. Among three
different plants, only the indices calculated from I. pseudacorus samples were significantly correlated
with nutrients."

This fauna resource assessment of Lake Danao Natural Park LDNP show that the area has high diversity of vertebrate fauna with correspondingly high numbers of birds and mammals, although reptiles and amphibians are poorly represented in the survey. This survey recorded new species record and high endemicity among the terrestrial vertebrates sampled.

ABSTRACT In aquatic systems, macrophytes play an important role in habitat structuring and can be relevant for the establishment and/or mobility of the organisms and might thus influence species composition. This study evaluates the influence of the structural complexity of aquatic plants on the community composition of Ostracoda in the upper Paraná River floodplain. We tested the hypothesis that non-swimming and small-sized species have a higher association with more complex plants by a threshold indicator taxa analysis. Some small and non-swimming ostracod species had a significant affinity for macrophytes with higher complexity, especiallyEichhornia crassipes. However, most species did not show an association with the structure of aquatic macrophytes, and there was only a slightly distinction among the communities of different plants. The results show that structural complexity is in some cases an important determining factor for the community composition of Ostracoda, but other factors may interact with and even override the effects of complexity. It can thus be concluded that the relation between habitat complexity and the Ostracoda community composition is complex and not always responds to general predictions.

Inlay Lake is the second largest natural lake in Myanmar. Located in Shan State, in the eastern part of the country, it is a known biodiversity hotspot. The lake is negatively affected by an increasing local human population and rapid growth in both agriculture and tourism. In recent decades, several studies have listed faunistic and floristic groups in Inlay Lake, but there is still a general lack of knowledge about the aquatic macrophyte and phytoplankton community composition and abundance, and their interactions. To fill this knowledge gap, field surveys of biological and physical and chemical parameters were carried out in the period 2014-2017. They show that Inlay Lake is a shallow, clear water and calcareous lake, with nutrient concentrations indicating mesotrophic-eutrophic conditions. However, close to the shore, nutrient concentrations are generally higher, reflecting pollution from inflowing rivers, shoreline villages and floating gardens. Both the richness and abundance of aquatic macrophytes in Inlay Lake were high, with several species forming extensive stands in most of the lake over the whole survey period. Total phytoplankton and cyanobacterial biomass were low, but cyanobacteria included toxin-producing strains of Microcystis, suggesting that cyanobacterial and total phytoplankton biomass need to be kept low to avoid potentially harmful cyanobacterial blooms. Submerged macrophyte abundance and phytoplankton biomass were inversely correlated in the heavily vegetated northern lake area. Our survey suggests a great importance of the submerged macrophytes to the general water quality and the clear water state in Inlay Lake. Maintaining high macrophyte abundances should therefore be a goal in management strategies, both for Inlay Lake and other lakes in Myanmar. It is highly desirable to include macrophytes and phytoplankton in the lake monitoring in Myanmar.

Allochthonous or autochthonous disturbances may change waterbodies from a clear to a turbid
state, increasing the availability of nutrients and promoting blooms of harmful cyanobacteria.
Submerged macrophytes may play an important role in alleviating the adverse effects of
phosphorus resuspension and release from bottom sediments. We assessed the effects of
allochthonous disturbances (rainfall and wind) on phosphorus release by constructing models
using data from 2 shallow lakes with contrasting steady states. Using partial least squares path
modeling, we examined submerged macrophytes, phytoplankton, and possible drivers of their
abundance. In the clear-water lake, the concentrations of total phosphorus (TP) had the greatest
direct influence on the macrophyte percentage of volume infested and phytoplankton biomass,
followed by concentrations of TP in the sediment. In the turbid lake, the TP concentration in the
water was the most important factor affecting phytoplankton biomass directly, followed by
disturbances on TP concentration in the sediment and euphotic zone. Our models support the
hypothesis that submerged macrophyte coverage acts as a stabilizing force to prevent the
proliferation of cyanobacteria and stabilize the clear-water phase in semiarid lakes. However,
potential mutual inhibition mechanisms between the submerged macrophyte Nitella cernua and
the cyanobacterium Microcystis aeruginosa need to be better addressed for restoration purposes
in lakes with shallow clear waters.

Theories that link plant strategies and abiotic filters discriminate between three strategies: competitive, ruderal or stress-tolerant species, and suggest that func-tional diversity is higher at intermediate values along the gradients of productivity and disturbance. The mechanism by which abiotic filters screen plant traits in aquatic plant communities has been poorly tested and has led to con-trasting results. The present study aimed to test whether functional diversity and abundance of life-history traits corresponding to morphology, fecundity and longevity of aquatic plants were linked to disturbance and productivity. Fifty-nine shallow lakes that were arranged along a gra-dient of productivity (estimated through total phosphorus concentration) and drought-disturbance frequency were sampled for aquatic plants. Species traits were documented and functional diversity was calculated (richness, disper-sion and evenness) for each lake. Increasing total phosphorus concentration was associated with decreased functional richness and dispersion but not functional evenness. Functional diversity did not differ according to disturbance frequency, regardless of the index that was measured. High productivity favoured floating species with storage organs and vegetative reproduction, especially at low disturbance frequency. For all disturbance frequencies, low productivity favoured small species without storage organs and sexual reproduction. The present study partly supports the theoretical model. At high productivity levels, because phytoplankton is a better competitor for light than aquatic plants, plant traits are screened stringently, and species with traits that allow them to reach the photic zone are selected.

Waterbirds can move into and exploit new areas of suitable habitat outside of their native range. One such example is the little egret (Egretta garzetta), a piscivorous bird which has colonised southern Britain within the last 30 years. Yet, habitat use by little egrets within Britain, and how such patterns of habitat exploitation compare with native piscivores, remains unknown. We examine overlap in habitat preferences within a river catchment between the little egret and two native species, the grey heron (Ardea cinerea) and great cormorant (Phalacrocorax carbo). All species showed strong preferences for river habitat in all seasons, with other habitat types used as auxiliary feeding areas. Seasonal use of multiple habitat types is consistent with egret habitat use within its native range. We found strong egret preference for aquatic habitats, in particular freshwaters, compared with pasture and arable agricultural habitat. Egrets showed greater shared habitat preferences with herons, the native species to which egrets are most morphologically and functionally similar. This is the first study to quantify little egret habitat preferences outside of its native range.

The present study investigates the zooplankton community dynamics and the abiotic environment in the eutrophic Lake Lysimachia (western Greece). The lake is considered to be recovering from eutrophication after the termination of an urban sewage inflow in 2000, and its waters are replenished constantly from the nearby oligotrophic Lake Trichonis. The results show that, although a decrease in nutrient concentrations was observed compared to the past, the lake still has eutrophic characteristics. This was reflected in the zooplankton community which is typical of those found in eutrophic lakes where rotifers prevail. Similarities among this lake and other nearby lakes were found considering the zooplankton community composition and seasonal variation. However, Lake Lysimachia is inhabited also by a number of different and even unique species (e.g., Moina micrura), suggesting that this ecosystem may be an important biodiversity refuge. Most of the zooplankton species were correlated with water temperature and, to a lesser extent, eutrophication key-water quality variables. Although there are few available data on the zooplankton of the lake, the abundance and composition of the community presenting characteristics indicative of intermediate trophic conditions and suggesting that the lake is probably under a kind of “biological” recovery

A sediment core from a Mediterranean karstic lake was studied through its pollen, diatom, chydorid, ostracod, charcoal and authigenic mineral composition. Information about environmental history recorded in the sediment sequence since the Middle Ages is presented. The main fluctuations of water volume and trophic status of the lake occurred during periods of great change in land management and during climatic cold phases. The synergetic effect of these two factors led to a high water level phase and triggered a rising of the trophic level which produced meromixis. The onset of meromictic conditions at about 1700 AD coincides with the Maunder minimum in the Little Ice Age as well as with a period of increasing human population, woodland clearance and agricultural expansion to the detriment of the nomadic livestock breeding or transhumance ("Mesta").

Waterfowl can cause substantial reductions in plant standing crop, which may have ecological and economic consequences. However, what determines the magnitude of these reductions is not well understood. Using data from published studies, we derived the relationship between waterfowl density and reduction in plant standing crop. When waterfowl density was estimated as individuals ha−1 no significant relationship with reduction in plant standing crop was detected. However, when waterfowl density was estimated as kg ha−1 a significant, positive, linear relationship with reduction in plant standing crop was found. Whilst many previous studies have considered waterfowl species as homologous, despite large differences in body mass, our results suggest that species body mass is a key determinant of waterfowl impact on plant standing crop. To examine relative impacts of waterfowl groups based on species body mass, a measure of plant biomass reduction (R s) per bird per hectare was calculated for each group. Comparison of R s values indicated some differences in impact between different waterfowl groups, with swans having a greater per capita impact than smaller-bodied waterfowl groups. We present evidence that this difference is linked to disparities in individual body size and associated differences in intake rates, diet composition and energy requirements. Future research priorities are proposed, particularly the need for experiments that quantify the importance of factors that determine the magnitude of waterfowl impacts on plant standing crop.