Foreseeable global warming will differentially affect Chara vulgaris populations from different altitudes

Abstract A 2–4 °C increase in temperature is foreseen for the Mediterranean region by the end of the 21st century due to climate change. This warming is expected to occur as heat waves, and will be particularly important for shallow water bodies which are the main freshwater ecosystems in the Mediterranean. We subjected four populations of Chara vulgaris to a common garden experiment. Each population came from locations at different altitudes, hence living at different mean temperatures. Individual charophyte cultures were initiated with specimens from four origins and acclimatized at 20 °C in a controlled environment for 3 weeks. After this, all the populations were incubated under 3 water…

Zooplankton dynamics during autumn circulation in a small, wind-sheltered, Mediterranean lake

12 pages, and tables statistics.

Managing for resilience: an information theory-based approach to assessing ecosystems

Ecosystems are complex and multivariate; hence, methods to assess the dynamics of ecosystems should have the capacity to evaluate multiple indicators simultaneously. Most research on identifying leading indicators of regime shifts has focused on univariate methods and simple models which have limited utility when evaluating real ecosystems, particularly because drivers are often unknown. We discuss some common univariate and multivariate approaches for detecting critical transitions in ecosystems and demonstrate their capabilities via case studies. Synthesis and applications. We illustrate the utility of an information theory-based index for assessing ecosystem dynamics. Trends in this inde…

Inferring the Relative Resilience of Alternative States

Ecological systems may occur in alternative states that differ in ecological structures, functions and processes. Resilience is the measure of disturbance an ecological system can absorb before changing states. However, how the intrinsic structures and processes of systems that characterize their states affects their resilience remains unclear. We analyzed time series of phytoplankton communities at three sites in a floodplain in central Spain to assess the dominant frequencies or "temporal scales" in community dynamics and compared the patterns between a wet and a dry alternative state. The identified frequencies and cross-scale structures are expected to arise from positive feedbacks that…

The antagonistic effect of UV radiation on warming or nitrate enrichment depends on ecotypes of freshwater macroalgae (Charophytes).

Increases in ultraviolet radiation (UVR), a negative global change factor, affect aquatic primary producers. This effect is expected to be modulated by other global change factors, and to be different for populations adapted to different environments. A common garden experimental approach using freshwater green macroalgae, the cosmopolitan charophyte species Chara hispida and C. vulgaris, allowed us to test whether the beneficial increases in water temperature (T) and nitrate concentration (N) mitigate negative UVR effects. Also, whether these interactions would be not only species-specific but also according to the origin of the population; therefore, two populations of each species were u…

Daily patterns of mixing and nutrient concentrations during early autumn circulation in a small sheltered lake

17 pages, 11 figures, 1 table.-- Printed version published May 2005.

Allelopathic effects of microcystin-LR on the germination, growth and metabolism of five charophyte species and a submerged angiosperm

Abstract Microcystins (MCs) are produced by cyanobacteria in aquatic environments and adversely affect macrophytes at very high concentrations. However, the effects of MC on macrophytes at concentrations of environmental relevance are largely unknown. The main objective of this study was to analyze the allelopathic effects of MC-LR at natural concentrations (1, 8 and 16 μgMC-LR/L) on five charophyte species ( Chara aspera , C. baltica , C. hispida , C. vulgaris and Nitella hyalina ) and the angiosperm Myriophyllum spicatum . Macrophyte specimens were obtained from a restored area located in Albufera de Valencia Natural Park, a protected coastal Mediterranean wetland. Two different experimen…

Zooplankton species as indicators of trophic state in reservoirs from Mediterranean river basins

Zooplankton abundance and composition is sensitive to eutrophication, and its top-down effect in the planktonic food web can alter the classification of the trophic state of waterbodies based on th...

Zooplankton abundance: A neglected key element in the evaluation of reservoir water quality

Abstract Based on our results, we propose the use of zooplankton abundance (density or biomass) as an indicator to complement the information currently being used concerning the quality of water in reservoirs. Until now, the Water Framework Directive (EU) for lakes and reservoirs has not included zooplankton because the classification of the water trophic state is based on a bottom-up model: an increase in nutrients implies an increase in primary producers and, therefore, poorer water quality. The use of zooplankton has recently been claimed due to their sensitivity to environmental changes and their control over primary producers. From our work, carried out from 2006 to 2009 (summer and wi…

Spatial, seasonal and long-term variability of phytoplankton photosynthesis in lakes

The importance of phytoplankton production for carbon budgets in a semiarid floodplain wetland

Phytoplankton production (PP) in wetlands is not measured as often as that of macrophytes. A three year-study during a period of sustained high flooding was undertaken in a central Spanish floodplain wetland (Las Tablas de Daimiel National Park) to determine net PP, its spatial heterogeneity and controlling factors, and compare it with primary production in macrophyte communities. This enabled us to estimate carbon budgets for each community. All PP variables showed high spatial and temporal variability among sites, resulting in low coherence even when flooding connected all sites. Net PP corresponded to 25- 36% of submerged plant production and 3-10% of helophyte production. Net PP was con…

The role of charophytes in a Mediterranean pond created forrestoration purposes

A small, shallow basin was created and flooded with groundwater in a Reserve Area in Albufera de València Natural Park (AVNP) under the scope of a restoration program intended to mimic typical environments such as freshwater springs, abundant in the past but currently suffering from deterioration (desiccation, pollution, etc.), with the ultimate goal of increasing local biodiversity of submerged macrophytes, particularly charophytes. In this study we have monitored, from April 2009 (a few months after its first flooding) to September 2012, the dynamics of charophyte growth and related physical, chemical and biotic variables to highlight the factors determining charophyte success. Just after…

Seasonal wetlands in the Pacific coast of Costa Rica and Nicaragua: environmental characterisation and conservation state.

Seasonal wetlands in the Pacific coast of Costa Rica and Nicaragua: environmental characterisation and conservation status On the Pacific coast of Nicaragua and Costa Rica, rainfall patterns and clay-rich soils allow the development of extensive wetlands. These environments constitute unique habitats for the maintenance of aquatic biodiversity and provide significant ecological services to the surrounding seasonal dry forest. Despite these benefits, wetlands have been severely reduced in the last four decades, and little information is available on their biology and current conservation status. Here, we describe the main limnological traits of 30 sites representing different types of wetlan…

Hydrology Affects Environmental and Spatial Structuring of Microalgal Metacommunities in Tropical Pacific Coast Wetlands

The alternating climate between wet and dry periods has important effects on the hydrology and therefore on niche-based processes of water bodies in tropical areas. Additionally, assemblages of microorganism can show spatial patterns, in the form of a distance decay relationship due to their size or life form. We aimed to test spatial and environmental effects, modulated by a seasonal flooding climatic pattern, on the distribution of microalgae in 30 wetlands of a tropical dry forest region: the Pacific coast of Costa Rica and Nicaragua. Three surveys were conducted corresponding to the beginning, the highest peak, and the end of the hydrological year during the wet season, and species abun…

Long-Term Phytoplankton Dynamics in a Complex Temporal Realm

AbstractFaced with an environment of accelerated change, the long-term dynamics of biotic communities can be approached to build a consistent and causal picture of the communities’ life. We have undertaken a 25-year monthly-sampling study on the phytoplankton of a meso-oligotrophic lake, paying attention to controlling factors of overall biomass (TB) and taxonomical group biomass (TGBs). Long-term series included decreased trends of TB and TGBs, and multi-scale periodicity. A decadal TB periodicity emerged related to nitrogen concentration and Cryptophytes. Annual periodicities were mainly related to air and water temperature controlling the abundance of Chlorophytes or Dinoflagellates. Int…

Differential attributes of phytoplankton across the trophic gradient: a conceptual landscape with gaps

I provide a conceptual landscape of attributes of phytoplankton related to trophic gradients, by reviewing 69 papers and books on eutrophication, with special reference to the ecology of the phytoplankton. Forty-eight ecological variables such as total phosphorus and Chl-a, are used, each related to the trophic gradient measured. They are subdivided in structural features of the phytoplankton, functional or dynamic features, and other relevant properties of the plankton community. Only twelve of the forty-eight variables are statistically related to trophic gradient. In most cases, variability across a trophic gradient is only nominally described. Less attention is given to functional, stru…

Effects of overabundant nitrate and warmer temperatures on charophytes: The roles of plasticity and local adaptation

Global change effects, such as warming and increases in nitrogen loading, alter vulnerable Mediterranean aquatic systems, and charophytes can be one of the most affected groups. We addressed the possible interaction between these factors on two populations of the cosmopolitan charophytes Chara hispida and Chara vulgaris. Populations were taken from two different environments, a nitrate-poor mountain lake and a nitrate-rich Mediterranean coastal spring. The laboratory experiment had a 2 × 2 factorial design based on two nitrate levels (similar to and double the local conditions) and two temperatures. Increased temperatures favoured the growth of the four populations, but an increase in nitra…

Shifts in plankton assemblages promoted by free water surface constructed wetlands and their implications in eutrophication remediation

Abstract Two units of free water surface constructed wetlands (FWSCWs) were created in 2009 in a Mediterranean protected site, the Albufera de Valencia Natural Park, to treat eutrophic inflows to the Albufera de Valencia lagoon, the largest coastal lagoon in the Iberian Peninsula, affected by cultural eutrophication. Data of phytoplankton and zooplankton biomass and richness of the inflows and outflows corresponding to the first 3.5 years of operation of the system have been analyzed to evaluate the role of plankton in the eutrophication reversion. The FWSCWs significantly reduced the exported microalgal biomass, stimulated the potential mixotrophic groups of phytoplankton such as Euglenoph…

Effects of UVB radiation exposure from the molecular to the organism level in macrophytes from shallow Mediterranean habitats

Abstract The available data on the effects of UVB radiation (UVBR) are scarce for submerged macrophytes, particularly charophytes. We studied the effects of UVBR on Chara baltica, Chara hispida, Chara vulgaris, Nitella hyalina and Myriophyllum spicatum, collected from shallow Mediterranean waterbodies. In a short-term laboratory experiment, we subjected these species to three different UVBR treatments corresponding to daily biologically effective integrated doses of 0, 1 and 6 kJ m−2. The analysed response variables were DNA damage, UV-absorbing compounds (both the methanol-soluble–SUVACs- and, for the first time in charophytes, the methanol-insoluble cell wall-bound fraction–WUVACs-), the …

Plankton Ecology and Diversity

In this chapter we describe plankton responses induced by fluctuating hydrology and eutrophication process in the semi-arid TDNP wetland. We have followed the planktonic community since 1992, at seasonal and interannual scales, covering as well the spatial heterogeneity of the wetland. The studied planktonic components were bacterioplankton, autotrophic picoplankton, nano and microphytoplankton and zooplankton, including ciliates. Plankton has been studied in terms of species composition (diversity), functional groups, spatial heterogeneity, population dynamics. The present data from this wetland allow us to determine which factors (resources and conditions) are relevant for each group and …

Las Tablas de Daimiel National Park is a semiarid, hypertrophic wetland located in La Mancha (Ciudad Real, Central Spain). During the period 1996-2002 we carried out monthly samplings at three sites of Las Tablas. Thirty five taxa of Euglenophytes of the genera Astasia (1 taxon), Euglena (15), Lepocinclis (6), Phacus (9), and Trachelomonas (4) were identified. Six taxa are new records for Spain. Abundance, species richness, species groups and absolute and relative biomass of Euglenophytes widely fluctuated spatio-temporally in Las Tablas, without any statistically significant relationship (P > 0.05) with organic carbon (either particulate or dissolved), which has been long considered the ma…

Are there steady-state phytoplankton assemblages in the field?

The difficulty in advancing in Ecology is due, in part, to the fact that this science uses a mainly qualitative language instead of a more formal or mathematical one. Therefore, many ecologists' efforts are expended in controversies resulting from the vagueness of ecological concepts, for example: stability, equilibrium, ecosystem, community, and so on. When approaching the study of steady-state phytoplankton assemblage, the different interpretations of these concepts can paralyse fruitful discussion. In the following pages, there is an endeavour to both restrict and precise the meaning of some of the concepts related to this topic and to broaden the range of possibilities of steady-state i…

Metacommunities from bacteria to birds: stronger environmental selection in mediterranean than in tropical ponds

AbstractThe metacommunity concept provides a theoretical framework that aims at explaining organism distributions by a combination of environmental filtering, dispersal and drift. With the development of statistical tools to quantify and partially isolate the role of each of these processes, empirical metacommunity studies have multiplied worldwide. However, few works attempt a multi-taxon approach and even fewer compare two distant biogeographical regions using the same methodology. Under this framework, we tested the expectation that temperate (mediterranean-climate) pond metacommunities would be more influenced by environmental and spatial processes than tropical ones, because of stronge…

Non‐trophic key players in aquatic ecosystems: a mesocosm experiment

Factors controlling planktonic size spectral responses to autumnal circulation in a Mediterranean lake

14 pages, and figures, and tables statistics.

Autotrophic and Heterotrophic Picoplankton in Wetlands: Differences with Lake Patterns

This study describes the occurrence, importance and seasonal patterns of picoplankton in two wetlands (TDNP and La Safor), and compares them to a system of fifteen interconnected lakes (Ruidera). In TDNP we performed a six-year monthly study in three sites of the wetland. Bacterial abundance increased throughout time and the autotrophic picoplankton (APP) range was wide (up to 33 x 10 6 cells/ml). The annual averaged APP contribution to total picoplankton and phytoplankton biovolumes was 0.5-22% and 0.03-6% respectively. There were large differences among sites in terms of APP absolute and relative abundance and seasonal patterns. In La Safor, the APP relative contribution to picoplankton a…

Controlling factors of phytoplankton assemblages in wetlands: an experimental approach

The aim of this work is to answer some questions like: what factors control the phytoplankton assemblage? What factor or factors are perturbing the assemblage? What factors are driving or maintaining the stability? Are the different responses to the control factors dependent on the hierarchy level? For that, we tested experimentally the influence of herbivory, planktivory, nutrients and sediment on phytoplankton assemblages and its stability from a hypertrophic wetland (Las Tablas de Daimiel National Park, Spain) in three microcosm experiments. The study of the steady state phytoplankton assemblages in this perturbed system could point out some underlying processes instead of competition. T…

Influence of aquatic microbiota on the survival in water of the human and eel pathogen Vibrio vulnificus serovar E

Summary The eel and human pathogen Vibrio vulnificus serovar E (biotype 2) is seldom isolated from natural waters, although it can survive in sterilized artificial seawater microcosms for years. The main objective of the present study was to investigate whether aquatic microbiota can limit its survival and recovery from water samples. A set of preliminary experiments of survival in microcosms containing natural seawater and water from eel farms showed that the persistence of this pathogen was mainly controlled by grazing, and secondarily by bacterial competition. The bacte- rial competition was further analysed in artificial seawater microcosms co-inoculated with selected virulent serovar E…

Environment and Space Rule, but Time also Matters for the Organization of Tropical Pond Metacommunities

Metacommunities are dynamic systems, but the influence of time independently of environmental change in their configuration has been rarely considered. Temporary ponds are excellent ecosystem models, as they have well-defined boundaries in time and space; their communities are relatively isolated through a landscape matrix, and the progress of time leads to major changes through ecological succession and in habitat suitability related to hydroperiod dynamics. Therefore, strong temporal effects are expected to influence their metacommunity structure. We surveyed 30 temporary ponds along the dry tropical region of western Costa Rica and Nicaragua at three different moments of their hydroperio…

The role of eutrophication reduction of two small man-made Mediterranean lagoons in the context of a broader remediation system: Effects on water quality and plankton contribution

In order to meet the requirements of the European Union Water Framework Directive for the Albufera de Valencia (AV) Natural Park, in 2009, several areas of free water surface constructed wetlands (FWSCWs) planted with emergent vegetation and two small shallow lagoons planted with submerged macrophytes were created over a 40-ha area formerly occupied by rice fields. This area is currently a reserve known as Tancat de la Pipa. The dual goal of this programme was to improve the quality of the hyper-eutrophicated waters of the AV lagoon, the largest littoral lagoon in the Iberian Peninsula, and to restore former lost habitats to increase the biodiversity of the area. The lagoons were mainly fed…

Biogeochemical decoupling: how, where and when?

Research has dealt with coupling of chemical element cycles and feedback in recent years. Sometimes, this biogeochemical coupling is reversed through abiotic or biotic (including man-made) processes. It is then called biogeochemical decoupling and is a disconnection between two chemical elements whereby transformations of one affect cycling of the other, and results in asynchronical behavior of chemical elements. It appears to be more important and widespread than earlier reports suggest, and gives rise to important changes in element stoichiometry of resources. These changes in turn modify organismal stoichiometry that, if great enough, can affect biodiversity and food webs, thus altering …

Nitrogen sedimentation in a lake affected by massive nitrogen inputs: autochthonous versus allochthonous effects

12 pages, and tables statics, and figures

Effects of Changing Rainfall on the Limnology of a Mediterranean, Flowthrough-Seepage Chain of Lakes

Relationships between groundwater and lake ecology are often overlooked, but they may be strong, particularly in seepage lakes. As a result, the nature and degree of groundwater effects on lakes are usually neglected. In this study interactions among rainfall, groundwater and surface water and their limnological effects were traced seasonally for two years of changing rainfall in a Spanish flowthrough, seepage lake complex. Cumulative rainfall dictated recharge of groundwater with delays of nine months. Groundwater discharge, in turn, increased surface discharge downstream. Mediated by the geographical setting of lakes, both fluxes impinged on lake water renewal time, but effects of the lat…

Different responses of coexisting Chara species to foreseeable Mediterranean temperature and salinity increases

Abstract An increase in temperature of approximately 4 °C is expected to occur in the Mediterranean by the end of the century. Concomitant to this warming, a foreseeable rise in salinity will affect aquatic species. We addressed the effects of warming and salinity, and their interaction on three coexisting characean species (Chara aspera, C. hispida and C. vulgaris) from a Spanish Mediterranean interdunal pond (spring water temperature 20–23 °C, when charophytes re-grew; salinity 1.3–1.8 PSU). A laboratory experiment was designed with two levels of water temperature treatment (23 and 27 °C), plus two levels of salinity treatment (0.4 and 4.0 PSU). The variables considered were total length,…

Plankton biodiversity in a landscape of shallow water bodies (Mediterranean coast, Spain)

A large spatial heterogeneity was detected in La Safor, a coastal area with different kinds of small and shallow water bodies. The area exhibits a sharp gradient in eutrophication (0.004–20 mgP l−1; 0.6–457 μg Chl a l−1) and varied water body features (morphology: size, depth; hydrology; vegetation, etc.). These factors result in a high diversity of aquatic habitats within the area. One hundred and twenty eight species of microalgae were identified in the 32 sampling stations studied (in the wet and dry periods). The phytoplankton richness varied between 1 and 21 species, the Shannon-Wiener index range was 0–3 bits, the index of floral originality (IFO) range was 0.1 – 0.6. A total number o…

Structure and vulnerability of the multi‐interaction network in macrophyte‐dominated lakes

The network approach is crucial to understand how ecosystems are structured and how they will respond to the disturbances (e.g. the current global change). We have recreated the multi‐interaction network of a shallow freshwater lake dominated by submerged macrophytes (Charophytes), a known system very vulnerable to environmental changes, considering both trophic and non‐trophic relationships among its elements. To minimize the environmental variability, we established it in an experimental mesocosm, including three habitats: the pelagic, the habitat around the meadow and the periphytic community living on macrophytes. We aimed to study the structure of this network and the roles of its elem…

Phytoplankton Fluctuations during an Annual Cycle in the Coastal Lagoon of Cullera (Spain)

The seasonal variation and the vertical distribution of the phytoplanktonic population of the lagoon of Cullera, an elongated coastal lagoon with estuarine circulation of water, has been studied in three sampling stations: mouth, centre and source. Seasonal variation is determined by a marine-freshwater interaction. In winter, the sea influence is important, a marine water wedge of anoxic water arrives at the sampling station located at the source and marine and brackish water species dominate the phytoplankton. Also marine species of zooplankton and fish enter the system, which may then be considered as exploited by the sea. In spring the marine wedge retreats from the source but remains i…

Population dynamics of Cyclotella ocellata (Bacillariophyceae): endogenous and exogenous factors

Population dynamics of Cyclotella ocellata PANTOCSEK were examined from 1991 to 1993 in an oligo-mesotrophic, gravel-pit lake near Madrid (Spain). Monthly and daily sampling was carried out to track seasonal- and auxosporulation dynamics, respectively. This species was the most abundant planktonic diatom in the lake. The population increased steadily in spring until the seasonal peak (3.8.10 6 ind/ L in April) and then abundance declined slowly through late winter. Time series techniques showed that the seasonal dynamics were driven by exogenous factors: there was a relationship between Cyclotella abundance and the chemical environment, both TP (synchronic) and SRSi (with delay). Auxosporul…

Restoration of two small Mediterranean lagoons: The dynamics of submerged macrophytes and factors that affect the success of revegetation

Abstract Two small, shallow lagoons newly created from former rice fields in the Mediterranean coast (Albufera de Valencia Natural Park, Spain) were restored by planting several species of submerged macrophytes (Myriophyllum spicatum, Ceratophyllum demersum, Potamogeton spp., Zannichellia peltata and Ranunculus peltatus) in 2008. Charophytes also appeared spontaneously. M. spicatum was the species that dominated both lagoons and almost completely covered their surface. M. spicatum reached a high biomass and displayed a seasonal pattern, declining during the cold season and reappearing in the spring. No submerged vegetation was observed in the lagoons from 2011 onward. The major purpose of t…

Unravelling the bacterial diversity found in the semi-arid Tablas de Daimiel National Park wetland (central Spain)

Our knowledge of microbial diversity in the environment is still limited, and there are many species as yet unidentified in both soil and water. Studies of the microbial diversity of wetland ecosystems have been neglected for years, as is the case of Tablas de Daimiel National Park (TDNP), a Spanish semi-arid wetland system of international importance in terms of waterfowl. We report the bacterial diversity of water column, sediment (upper and lower layers) and biofilm samples from the TDNP system using a 16S rRNA gene library approach. A sequence comparison of the 703 clones obtained revealed a number of bacterial phylogroups unreported to date. Bacterial diversity was high (Shannon values…

On the tolerance of charophytes to high-nitrate concentrations

Currently a debate exists about whether the reduced growth of macrophytes with increased nitrogen loading in shallow ecosystems is determined by ecological or physiological factors. To discover whe...

Chara hispida beds as a sink of nitrogen: Evidence from growth, nitrogen uptake and decomposition

8 pages, and tables stadistics, and figures.

The allelopathic capacity of submerged macrophytes shapes the microalgal assemblages from a recently restored coastal wetland

Abstract We have tested the efficiency of isolated and combined submerged macrophyte cultures to inhibit, through allelopathy, the natural phytoplankton growth. Both plants and microalgae come from the same wetland, a recently restored area in Albufera de Valencia Natural Park (Spain). The need to replant the area under restoration with submerged macrophytes makes this information essential for wetland management. The selection and culture of the submerged macrophytes used in that restoration (four charophytes: Chara hispida , Chara vulgaris , Chara baltica , Nitella hyalina , and one angiosperm: Myriophyllum spicatum ) provided a good opportunity to test in the laboratory the allelopathic …

Nitrate uptake rates in freshwater plankton: the effect of food web structure

9 pages, 3 figure, 1 table

On the tolerance of charophytes to high-nitrate concentrations

Currently a debate exists about whether the reduced growth of macrophytes with increased nitrogen loading in shallow ecosystems is determined by ecological or physiological factors. To discover whether nitrate in the water is detrimental per se to charophytes, we subjected Chara hispida and Chara vulgaris specimens, collected from two habitats greatly differing in nitrate concentrations (1.5 and 10 mg NO3-N/L, annual means), to a wide nitrate range (0.5–50 mg NO3-N/L) in two experiments (with free-floating specimens using nitrate as the sole N source, and with planted specimens, with other N sources in sediment). Charophytes grew both unplanted and planted in all treatments, and growth redu…

Zooplankton species as indicators of trophic state in reservoirs from Mediterranean river basins

Zooplankton abundance and composition is sensitive to eutrophication, and its top-down effect in the planktonic food web can alter the classification of the trophic state of waterbodies based on the microscopic primary producers. However, this relevant group in aquatic ecosystems is overlooked when lakes and reservoirs are monitored to describe and improve water quality as required by the European Water Framework Directive (WFD). Fortunately, we have data on monitored zooplankton and the physical, chemical, and biological variables prescribed by the WFD in 20 Mediterranean reservoirs over a 4-year period (summer and winter sampled). We related zooplankton composition (90 species) with these…