Inundation Duration Shapes Germination of Native and Non‐Native Plant Assemblages From Floodplain Soil Seedbanks

Wetlands are highly productive and biodiverse ecosystems and provide many ecosystem services for humans. They are a key component of the natural hydrological cycle and are involved in important biophysical processes, such as the exchange of sediments, nutrients and organisms which influence water quality and functional integrity of rivers. Owing to their high productivity, fertile soils, and importance for water provision, many of the world’s wetlands have a long history of human occupation and intensive use. As a consequence, extensive degradation and modification of wetland ecosystems by human activities has occurred worldwide. In seasonal wetlands, the timing and duration of soil saturation and inundation are the main determinants of geomorphological and ecological characteristics that give rise to a great variety of ecosystem types. Although the ecological functioning of seasonal wetlands relies on this strong temporal driver, wetland conservation decisions often are based on static maps of wetland boundaries that fail to depict their dynamic hydrological variability and connectivity. Another challenge in wetland conservation is accounting for multiple dimensions of wetland connectivity in the riverine landscape. For example, the ecological integrity of large floodplain rivers, such as the Amazon River system, depends on the maintenance of a diversity of waterbodies with variable degrees of connectivity between themselves and with the main river channel. Lack of adequate frameworks in wetland conservation planning to account for these different sources of connectivity can compromise the long-term persistence and integrity of wetlands in the landscape. This is a critical issue because human activities such as land use change, levee construction and flow regime alterations can lead to the disruption of connectivity, thus greatly affecting wetlands downstream and compromising their ecological integrity and provision of ecosystem services. The overall objective of this thesis is to develop a new framework of systematic conservation planning for river-floodplain ecosystems that adequately accounts for the multidimensional connectivity of wetlands in riverine landscapes. To achieve that, I have combined the use of remote sensing tools at multiple scales with statistical modelling and spatial planning to address three main issues in wetland conservation: (1) the lack of comprehensive assessments to determine conservation status of the world’s wetlands, (2) the limitations of representing wetland seasonality in traditional static maps that often delineate wetland boundaries based on minimum or maximum extents, and (3) the lack of adequate spatial frameworks in systematic conservation planning to deal with wetland connectivity in the riverine landscape. To address the first issue, I developed a global-scale portrait of the threats and protection status of the world’s inland wetlands. This was achieved by combining a global map of inundation extent derived from satellite images with data on threats from human influence and on protected areas. Inland wetlands represent only ~6% of the world’s land surface, and about 89% of these areas have no formal protection (as defined by protected areas IUCN I-VI and Ramsar sites). Wetland protection was variable across the world, ranging from 20% in Central and 18% in South America to only 8% in Asia. Particularly high human influence was found in Asia, which contains the largest wetland area of the world. High human influence was observed in wetlands even when they are within protected areas. This demonstrated that terrestrial protected areas do not always adequately protect wetland ecosystems and underscores the urgent need for more effective conservation measures worldwide. To tackle the second issue, I undertook a hydrological classification of the Amazon wetlands according to the timing and duration of inundation. The classification was based on remotely sensed monthly inundation maps, and also investigated how precipitation regimes affect wetland distribution and hydrological dynamics. Permanently inundated wetlands accounted for the largest area and were mainly floodplains located in the lowlands of the catchment. Seasonally inundated wetlands varied greatly in duration of inundation over the course of the year, ranging from one to nine months. Distinct seasonal timing was detected among large wetland complexes, reflecting rainfall regimes as well as time lags for recession and drying. For example, inundation in the extensive Llanos the Moxos region of the southern Amazon was protracted and lasted well after the rainy season, compared to the Roraima region of the northern Amazon where inundation was shorter and tracked the rainy season. This integration of inundation dynamics into wetland classification captures regional differences in timing and duration of inundation in major wetlands of the basin that should be considered in conservation planning and other ecological applications. Finally, I developed a new framework in systematic conservation planning to account for the multidimensional connectivity of floodplain river ecosystems and provide more adequate protection of wetlands, and applied this to the entire Amazon basin. Accounting for both within-floodplain and longitudinal river connectivity in the riverine landscape, the new spatial framework combines two types of planning units – wetland hexagons and subcatchments – which were connected using two distance-based approaches. Four prioritization scenarios were tested comparing only within-floodplain connectivity versus integrated within-floodplain and upstream connectivity and resulted in varying levels of reduced impact. When only considering within-floodplain connectivity, propagation of impacts from the surroundings and upstream catchment was ignored. In contrast, the scenario that included both within-floodplain and longitudinal river connectivity agglomerated subcatchments around the priority wetlands, achieving catchment integration that efficiently reduced impact. This thesis contributes to the field of wetland conservation by integrating cutting edge data science with novel planning methods. It highlights the conservation status of inland wetlands and quantifies global and continental threat patterns. The innovative classification approach that spatially represents seasonal patterns in wetland inundation can be used to explore the role of seasonality on the ecological characteristics and functions of different wetlands complexes. It represents an important step towards including temporal dynamics in wetland conservation planning and management. Furthermore, including the multidimensional connectivity of wetlands in a comprehensive spatial framework can offer more ecologically meaningful protection to floodplains. This is crucial to plan for safeguarding wetland ecosystem functions at the landscape context. Finally, the use of global remotely sensed data sets make all approaches presented here readily adaptable for use in other regions of the world.

Several studies of temporary floodplain wetlands suggest that flood history is important to microcrustacean egg bank composition and hatching responses. However, these studies have largely focussed on contrasts among less frequently flooded areas (areas flooded every year to areas flooded once every 10–20 years) and less is known about variation at the more frequently flooded end of the gradient (from multiple floods per year to once every 2 years). Similarly, the effects of flood duration on egg banks have not been examined in detail. Thus, this study examines spatial variation in microcrustacean hatching at higher flood frequencies and in relation to inundation duration. Surface sediment samples were collected from dry anabranches of the Macintyre River floodplain in Australia during February 2018, with a range of flood frequency from approximately four times per year to one in 2 years. Anabranches were selected randomly from predefined flood frequency classes and clustered into three different flood history groups based on flood history variables. Soil samples were collected from deep and shallow locations within anabranches, with depth assumed to be a proxy for the duration of inundation. Sediment samples were inundated in mesocosms and hatched microcrustaceans sampled over 6 weeks. Microcrustacean abundance and assemblage composition varied by sites, relative depth, and duration of inundation. There was no variation by flood history groups. Highest numbers hatched from the deeper areas of anabranches, which is assumed to reflect differences in the egg banks of deep and shallow areas due to the longer duration of inundation in deeper areas. Duration also influenced hatching response from the egg bank, with more microcrustaceans hatching per unit time in the first 2 and final 2 weeks of the 6‐week trial than the middle 2 weeks. Species richness also varied by relative depth and duration of inundation with more taxa hatching from the deeper areas of anabranches. The study highlights the critical influence of flood duration on hatching patterns of microcrustaceans from inundated sediments. Therefore, changes to flood duration have the potential to influence microcrustacean assemblages and thus further changes to trophic interactions in temporary floodplain wetlands. ​

Freshwater wetlands are significant carbon sinks, however, altering a wetland’s hydrology can reduce its ability to sequester carbon and may lead to the release of previously stored soil carbon. Rehabilitating a wetland’s water table has the potential to restore the natural process of wetland soil carbon sequestration and storage. Further, little is known about the role of microbial communities that mediate carbon cycling during wetland rehabilitation practices. Here, we examined the carbon emissions and microbial community diversity during a wetland rehabilitation process known as ‘environmental watering’ (rewetting) in an Australian, semi-arid freshwater floodplain wetland. By monitoring carbon dioxide (CO2) and methane (CH4) emissions during dry and wet phases of an environmental watering event, we determined that adding water to a degraded semi-arid floodplain wetland reduces carbon emissions by 28-84%. The watering event increased anoxic levels and plant growth in the aquatic zone of the wetland, which may correlate with lower carbon emissions during and after environmental watering due to lower anaerobic microbial decomposition processes and higher CO2 sequestration by vegetation. During the watering event, areas with higher inundation had lower CO2 emissions (5.15 ± 2.50 g CO2 m-2 d-1) compared to fringe areas surrounding the wetland (11.89 ± 4.25 g CO2 m-2 d-1). CH4 flux was inversely correlated with CO2 emissions during inundation periods, showing a 38% (0.013 ± 0.061 g CO2-e m-2 d-1) increase when water was present in the wetland. During the dry phases of environmental watering, there was CH4 uptake within the fringe and aquatic zones (-0.013 ± 0.063 g CO2-e m-2 d-1). A clear succession of soil microbial community was observed during the dry-wet phases of the environmental watering process. This suggests that wetland hydrology plays a large role in the microbial community structure of these wetland ecosystems, and is consequently linked to CO2 and CH4 emissions. Overall, the total carbon emissions (CO2 + CH4) were reduced within the wetland during and after the environmental watering event, due to increasing vegetative growth and subsequent CO2 sequestration. We recommend environmental watering practices in this degraded arid wetland ecosystem to improve conditions for wetland carbon sequestration and storage.

Hydrologic extremes of flooding and drought typically occur each year in prairie streams. Two experiments were conducted in a fifth-order, gallery forest reach of Kings Creek, Kansas, to assess the effect of hydrologic conditions on decomposition of leaves in the stream channel and on the adjacent floodplain. Temporal patterns of weight loss were examined in the first experiment. Leaves of bur oak and hackberry decomposed more rapidly in the channel than on the adjacent bank. A sharp drop in percent remaining for hackberry in the 2nd month (mid-December to mid-January) coincided with a period of high shredder densities on hackberry leaves. On the bank, decomposition of hackberry leaves was fastest during intervals that included one or more inundations of the leaf packs. Bur oak leaves decomposed more slowly than hackberry leaves and were influenced less by the hydrologic history. In the second experiment, spatial variation in decomposition rate of hackberry leaves was examined by placing 20 pairs of leaf packs in a transect extending from the center of the stream channel to the top of the upper bank. Position on the transect affected the frequency and duration of inundations on the floodplain, which ranged from once (minimum of 0.2 hr) to 17 times (272 cumulative hr under water), while three pairs of packs in the channel were always under water. The logarithm of percent remaining after 274 days was significantly correlated with number of hours inundated and number of times inundated, although other factors such as soil moisture or amount of flood-deposited silt may have influenced differences in decomposition rates along the transect. We concluded that flood frequency, duration and timing affected both spatial and temporal patterns of decomposition, especially of a fast-decomposing species, in the riparian forest of an intermittent prairie stream. INTRODUCTION Hydrologic extremes of flooding and drought typically occur each year in prairie streams. Periodic flooding may cause increases in decomposition rates in channels of prairie streams, while desiccation slows decomposition (Tate and Gurtz, 1986). Storm flows can dislodge stored organic materials from the stream bottom and either export them to downstream reaches or deposit them laterally on the stream bank. Organic matter deposited on the floodplain remains there until it is decomposed, returned to the stream by lateral movement, or resuspended by another storm flow. Residence time of organic matter in the channel and on the floodplain is therefore affected by hydrologic conditions, which in turn may influence decomposition rates. Flooding in seasonally inundated wetlands or floodplain forests generally promotes faster decomposition, whereas decomposition in freshwater systems is faster than in terrestrial systems (Webster and Benfield, 1986). Cellulose sheets placed in a North Carolina alluvial swamp forest decomposed in the sequence (fast to slow) of river > swamp > levee environments, probably due to differences in moisture conditions (Brinson, 1977). In that wetland system, increased frequency or duration of flooding did not always lead to faster decomposition rates for all species. Rather, the fastest loss rates may occur under aerobic conditions and some optimum regime of wetting and drying (Brinson et al., 1981). Day (1983) found that faster decomposition rates were directly related to flooding in microcosms that remained aerobic. In a floodplain hardwood forest along the Appalachicola River, Florida, rates of leaf decomposition were much slower in dry 'Present address: P.O. Box 2857, Raleigh, N. Carolina 27602.

Long‐lived vegetation is a key attribute of lowland river floodplains; yet dieback is increasingly being reported globally, with prior studies identifying salinity, drought and altered flow regimes as key stressors. In the Murray–Darling Basin (Australia), many floodplain/wetland areas have management strategies that aim to maintain the condition of floodplain tree communities. Environmental water delivery is a key tool used to achieve such outcomes. Currently, one of the primary tools for determining the need for environmental water delivery is a qualitative visual assessment of tree crown condition. To advance to more quantitative assessment and understanding of tree condition, we present a suite of techniques ranging from low‐cost, rapid visual assessment of tree crown condition to laboratory analysis of components of soil condition and in situ measurement of tree physiology. The aim is to address a number of key knowledge gaps on how to use the linkages between soil water availability ↔ tree physiology ↔ tree visual condition to quantitatively inform environmental water delivery decisions to meet management objectives. We have developed a multiple‐lines‐of‐evidence management assessment framework that presents a pathway to enable managers to improve prioritisation management actions. Furthermore, increased confidence in predicted outcomes should assist water holders and floodplain managers to optimise timing and maximise the benefits of environmental watering. Application of outcomes of this research will increase the efficiency of environmental water use.

The increasing number and duration of inundations is reported to be a consequence of climate change and may severely compromise non-adapted macroorganisms. The effect of flooding events on terrestrial and aquatic microbial communities is, however, less well understood. They may respond to the changed abiotic properties of their native habitat, and the native community may change due to the introduction of alien species. We designed an experiment to investigate the effect of five different flooding durations on the terrestrial and aquatic communities of eukaryotic microorganism, using the AquaFlow mesocosms. With amplicon sequencing of the small subunit (SSU)and internal transcribed spacer (ITS)rRNA gene regions, we analyzed community compositions directly before and after flooding. Subsequently, they were monitored for another 28days, to determine the sustainability of community changes. Our results revealed a temporary increase in similarity between terrestrial and aquatic communities according to OTU composition (operational taxonomic unit, serves as a proxy for species). Increased similarity was mainly caused by the transmission of OTUs from water to soil. A minority of these were able to persist in soil until the end of the experiment. By contrast, the vast majority of soil OTUs was not transmitted to water. Flooding duration affected the community structure (abundance) more than composition (occurrence). Terrestrial communities responded immediately to flooding and the flooding duration influenced the community changes. Independent from flooding duration, all terrestrial communities recovered largely after flooding, indicating a remarkable resilience to the applied disturbances. Aquatic communities responded immediately to the applied inundations too. At the end of the experiment, they grouped according to the applied flooding duration and the amount of ammonium and chloride that leached from the soil. This indicates a sustained long-term response of the aquatic communities to flooding events.

Floodplains downstream of urban catchments are sinks for potentially toxic trace elements. An intensification of the hydrological cycle and changing land use will result in floodplains becoming inundated for longer durations in the future. We collected intact soil cores from a floodplain meadow downstream of an urban catchment and subjected them to an inundation/drainage cycle in the laboratory to investigate the effect of flood duration on trace element concentrations in the soil porewater. The porewater concentrations of Ni, Cr, and Zn increased, whereas Cu and Pb decreased with flood duration. All the Cr present in porewaters was identified as Cr(III). Copper concentrations increased after drainage but Pb mobility remained suppressed. Both pH and dissolved organic carbon (DOC) increased with flood duration but were lower in treatments that were drained for the longest duration (which were also the treatments flooded for the shortest duration). The porewater concentrations of Cr and Ni decreased after drainage to levels below those observed before inundation, mirroring the DOC concentrations. We concluded that the duration of floodplain inundation does have an influence on the environmental fate of trace elements but that flooding does not influence all trace elements in the same way. The implications of an intensification of the hydrological cycle over the coming decades are that floodplains may become a source of some trace elements to aquatic and terrestrial ecosystems. Environ Toxicol Chem 2020;39:2124-2135. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Daily 3-m cell size Dove multispectral satellite images were used to estimate the duration of flooding in topographic depressions in the approximately 12-km2 Shores Road focus area, central Tennessee. Flooding happened after rainfall events February 4–6 and 10–12, 2020. The filling and draining of 60 topographic depressions (mostly sinkholes) were observed by visually inspecting images for eight dates. The average duration of inundation was approximately 15 days, and all depressions were dry 30 days after the end of the first event. Satellite observations were consistent with ground-based water elevation measurements in three sinkholes and eight wells. Depression volume, elevation, and depth were estimated with a 0.76-m cell size LiDAR 3D Elevation Program (3DEP) digital terrain model (DTM). Long-duration (21 or more days) inundation was statistically more likely in larger-volume, lower-elevation, and deeper depressions at the p < 0.01 level. When combined in a probit model, these three factors accurately sorted 80 percent of depressions into long-duration and short-duration categories, and the accurately classified depressions accounted for approximately 95 percent of depression volume. Duration of inundation was not related (p > 0.05) to percentage of depression covered by slow-permeability soils, as determined from the Soil Survey Geographic Database. This study shows how to use repeat Dove satellite imagery and a LiDAR 3DEP DTM to assess how multiple topographic factors contribute to the duration of inundation in sinkholes.

In temporary ponds, seed germination largely determines how well aquatic plant assemblages recover after dry periods. Some aquatic plants have terrestrial morphotypes that can produce seeds even in dry years. Here, we performed an experiment to compare germination patterns for seeds produced by aquatic and terrestrial morphotypes of Ranunculus peltatus subsp. saniculifolius over the course of five inundation events. During the first inundation event, percent germination was higher for terrestrial morphotype seeds (36.1%) than for aquatic morphotype seeds (6.1%). Seed germination peaked for both groups during the second inundation event (terrestrial morphotype: 47%; aquatic morphotype: 34%). Even after all five events, some viable seeds had not yet germinated (terrestrial morphotype: 0.6%; aquatic morphotype: 5%). We also compared germination patterns for the two morphotypes in Callitriche brutia: the percent germination was higher for terrestrial morphotype seeds (79.5%) than for aquatic morphotype seeds (41.9%). Both aquatic plant species use two complementary strategies to ensure population persistence despite the unpredictable conditions of temporary ponds. First, plants can produce seeds with different dormancy periods that germinate during different inundation periods. Second, plants can produce terrestrial morphotypes, which generate more seeds during dry periods, allowing for re-establishment when conditions are once again favorable.

This study evaluated the hydrologic sensitivity of vernal pool ecosystems in the Central Valley of California to climatic changes projected for 2100. A vernal pool water-balance model was used to evaluate rain-fed vernal pools at four locations under future conditions projected by two contrasting global climate models. The potential for change in the duration of continuous inundation, frequency of reproductively suitable inundation events, and the seasonal distribution of inundation was quantified. The potential impact of hydrologic changes varied by species and by location. Three scales of response were identified: (a) At the regional scale, pools in the middle of the Central Valley near Merced were the most responsive to climatic changes. (b) At the local scale, smaller, shallower pools had the greatest potential to change the distribution of reproductively suitable habitat available to branchiopods. (c) At the individual pool scale, changes in precipitation will dominate changes in temperature, resulting in relatively linear responses in the duration of inundation. The ecological impact of these changes will be determined by a balance between the increasing suitability of vernal pools for branchiopod predators and the hydrologic improvement of currently marginal habitats.

Floodplain wetlands play a significant role in the storage of sediment and water and support high levels of nutrient cycling that is driven by intermittent inundation. In regulated rivers, there is often a reduction in the frequency and duration of inundation and managed floodplain inundation is used as a tool to help restore wetlands. It is important to quantify the outcomes of re-introducing water to floodplain wetland systems. We examined the effects of environmental floodplain watering on water quality and three groups of invertebrates, including benthic and pelagic microinvertebrates and macroinvertebrates, in two wetlands systems on the Gwydir River system in the north of the Murray-Darling Basin. We hypothesised that a wetland inundated for longer periods of time would have altered water quality and support a greater richness and abundance of invertebrates, thus altering their assemblage structures. Water quality and the assemblage structure of all three invertebrate groups in the wetlands was significantly influenced by the time since connection (TSC) to their rivers and therefore the length of inundation. However, the response of water quality and the microinvertebrate assemblages to TSC differed between the two wetlands. Water quality was affected by an increase in six variables, including the nutrient TN and a decrease in the nutrient SRP. Microinvertebrate abundance was positively associated with TSC, but the abundance of macroinvertebrates was not. The relationships demonstrated between TSC and invertebrates indicate that the duration of inundation is important in maintaining the ecology and food webs in these and other semi-arid floodplain wetlands.

The bottom-up and top-down interactions of the abiotic and biotic components of Iyieke Lake were studied for eleven months covering a pre-flood, flood and post-flood periods. During the study, some water quality parameters were measured while plankton samples were collected for identification in the laboratory using standard method. The results of the water quality parameters measured showed that water temperature was highest (35.00R”C) in February. pH (7.10) and transparency (0.98 m) were highest in August. Highest TDS (28.0 mg/L) and conductivity (56.00 μS/cm) were recorded in March (pre-flood period) while dissolved oxygen level was lowest (4.00 mg/L) in the pre-flood period (February and March). Nitrate (0.18 mg/L) was highest in August (flood period) and phosphate (0.25 mg/L) at the two extreme periods (pre-flood and post flood). The depth of the lake was highest (3.2 m) in August which was the period of inundation. The phytoplankton (Bacillariophyta, Chlorophyta, Cyanobacteria) and zooplankton (Rotifera, Cladocera, Copepoda) of the lake were made of three divisions and taxa each, respectively. Bacillariophyta dominated among the phytoplankton while Rotifera was the most abundant among the zooplankton. The study revealed that nutrients and zooplankton grazing were the major factors that affected phytoplankton abundance and biomass during the study.
 Keywords: Flood; phytoplankton; Iyieke; water quality; zooplankton

Influence of flood depth and duration on growth of lowland rice weeds, Cote d’Ivoire

Some plant species retain mature seeds in plant canopies aboveground which are released later during opportune windows for germination and establishment. This process, known as serotiny, can lead to aerial seedbanks that exist simultaneously with soil seedbanks. However, little is known about how serotiny affects the persistence of weed seeds in the aerial seedbank. A randomized-stratified survey of 117 sites in southern Alberta, Canada, was conducted in 2022 to determine whether the summer-annual tumbleweed Russian thistle (Salsola tragus L.) exhibits seed serotiny. The observational study confirmed that Russian thistle plants exhibit serotiny and that the seeds can exist simultaneously in aerial and soil seedbanks. On average, the plants sampled retained 332 ± 62 viable seeds plant-1 seven to eight months after senescence. This time frame followed winter and emergence of the subsequent generation of plants from the soil seedbank. Russian thistle plants that were attached to the soil retained about double (P = 0.0274) the number of seeds (549 ± 133 viable seeds plant-1) than those detached from the soil (270 ± 71 viable seeds plant-1), likely due to seeds dislodging during movement of the tumbleweeds with prevailing winds. Seeds persisting in aerial seedbanks could evade decay, predation, or lethal germination leading to seed mortality in the soil seedbank, and increase the likelihood of seed persistence and successful establishment of new plants in stressful environments.

The study presents the results of lichenological research conducted in 2012–2016, based on my fieldwork carried out in mountain streams in the Polish Western Carpathians, revision of herbarium materials, and published data on lichen species in freshwater habitats in the study area. Field work was performed on 98 research plots divided into three zones related to duration of immersion (294 sampling sites in total). As the result of the work, 94 freshwater lichen species were found (91 based on my field work and/or revision of herbarium material), including 56 aquatic species. For all species, detailed descriptions of morphological and anatomical characters, information on their habitat, occurrence in the study area, worldwide and country distribution, and brief taxonomic notes are given. A key for species identification is also provided. From the present lichenological study, Verrucaria acrotella is reported as new for the Polish Western Carpathians. In total, 30 new species were recorded in particular mountain ranges in the study area. New records of Sarcogyne privigna and Thelidium fontigenum, very rare species in Poland, are given. The streams of the Polish Western Carpathians are characterized by high species diversity in various mountain ranges. The richest lichen biota was observed in streams of the Tatra Mts, where 76 species were found, representing more than 80% of the total number of freshwater lichens known from the Western Carpathians. In the Beskidy Mountains, species diversity in the streams remains within the range of 38–46 species. Two mountain ranges are distinguished by the presence of more species: the Beskid Sądecki Mts (60) and Beskid Żywiecki Mts (57). Thirtysix taxa were noted in the Carpathian foothills. A frequency analysis of lichens shows that very rare species (38 taxa; 40%) and rare species (32; 35%) dominate in the study area. Frequent lichens are the poorest group in the Polish Western Carpathians, accounting for only 4 species (slightly over 4%). Of all the lichens noted in the study area, 34 (~36%) are on the red list of the lichens in Poland. In the case of Carpathian streams, the substrate and the duration of inundation seem to be the most important factors for the occurrence of freshwater lichens. The duration of immersion also affects the species distribution. The submerged zone was the least diverse, in the terms of both number of species and represented families. The only species found there exclusively in the submerged zone were Ionaspis lacustris, Sporodictyon cruentum, Staurothele fissa, Thelidium submethorium, Verrucaria devensis and V. pachyderma. The splash zone provides a habitat transitional between the submerged and riparian zones. Lichens in this zone are constantly exposed to frequent changes between periods of inundation and desiccation. In the splash zone, both species found in the submerged zone as well as those occurring in the riparian zone were found. Species typical for the splash zone included Bacidina inundata, Gyalidea rivularis, Thelidium fontigenum, T. pluvium, Verrucaria humida and V. sublobulata. The most diverse group of lichens was associated with the riparian zone. Many lichens found in this zone are terrestrial lichens commonly found in non-freshwater habitats. They are considered to be rare in aquatic and semi-aquatic habitats but frequent in terrestrial habitats.