Aquatic Sciences

A common task in data analysis is to model the relationships between two sets of variables, the descriptor matrixX and the response matrixY. A typical example in aquatic science concerns the relationships between the chemical composition of a number of samples (X) and their toxicity to a number of different aquatic species (Y). This modelling is done in order to understand the variation ofY in terms of the variation ofX, but also to lay the ground for predictingY of unknown observations based on their knownX-data. Correlations of this type are usually expressed as regression models, and are rather common in aquatic science. Often, however, the multivariateX andY matrices invalidate the use of multiple linear regression (MLR) and call for methods which are better suited for collinear data. In this context, multivariate projection methods represent a highly useful alternative, in particular, partial least squares projections to latent structures (PLS). This paper introduces PLS, highlights its strengths and presents applications of PLS to modelling aquatic toxicity data. A general discussion of regression, comparing MLR and PLS, is provided.

1. The Ephemeroptera fauna of the World consists of 42 families, 400 genera and 3000 species, while the Ephemeroptera fauna of the Turkey consists of 14 families, 39 genera, 138 species and 5 subspecies.
2. The Ephemeroptera species of Turkey constitutes 4,6% of the Ephemeroptera species in the World.
3. With respect to the genera number, Ephemeroptera genera of Turkey constitutes 9,75%
of the Ephemeroptera genera in the World.
4. Ephemeroptera species play a critical role in order to define the reference sites and their fauna concerning the application of European Union Water Framework Directive (EUWFD) in Turkey.

Canonical correspondence analysis (CCA) is a multivariate method to elucidate the relationships between biological assemblages of species and their environment. The method is designed to extract synthetic environmental gradients from ecological data-sets. The gradients are the basis for succinctly describing and visualizing the differential habitat preferences (niches) of taxavia an ordination diagram. Linear multivariate methods for relating two set of variables, such as two-block Partial Least Squares (PLS2), canonical correlation analysis and redundancy analysis, are less suited for this purpose because habitat preferences are often unimodal functions of habitat variables. After pointing out the key assumptions underlying CCA, the paper focuses on the interpretation of CCA ordination diagrams. Subsequently, some advanced uses, such as ranking environmental variables in importance and the statistical testing of effects are illustrated on a typical macroinvertebrate data-set. The paper closes with comparisons with correspondence analysis, discriminant analysis, PLS2 and co-inertia analysis. In an appendix a new method, named CCA-PLS, is proposed that combines the strong features of CCA and PLS2.

In the Okavango Delta (about 28,000 km2) the number of identified species is 1,300 for plants, 71 for fish, 33 for amphibians, 64 for reptiles, 444 for birds, and 122 for mammals. The local occurrence of different species of these taxonomic groups in the Okavango Delta is mainly due to a hydrological gradient from permanent streams and swamps to seasonal floodplains, riparian woodlands, and dry woodlands. This level of species diversity is normal for the southern African region, and all analyzed aquatic groups are composed of ubiquitous species with an additional significant proportion of species originating from northern, more tropical systems. Cyclical variations in climate over thousands of years have created a huge wetland complex in the upper Zambezi and Okavango Rivers during wet phases. This wetland complex has fragmented into the Okavango Delta and other large wetlands in Zambia during dry phases. There are no endemic species in the Okavango Delta while the South-central African wetland complex is a centre of endemism. Species diversity of the Okavango Delta is a consequence of this unique environment, with dynamic shifts in flooding patterns that in turn force constant changes in patterns of plant succession and dependent animals. Temporal variations in flooding also cause accumulation and sudden mobilization of nutrients which are readily used by well adapted plant species. As a consequence, locally high biological productivity occurs, which in turn results in high numbers of grazing mammals.

Aquatic plants fulfil a wide range of ecological roles, and make a substantial contribution to the structure, function and service provision of aquatic ecosystems. Given their well-documented importance in aquatic ecosystems, research into aquatic plants continues to blossom. The 14th International Symposium on Aquatic Plants, held in Edinburgh in September 2015, brought together 120 delegates from 28 countries and six continents. This special issue of Hydrobiologia includes a select number of papers on aspects of aquatic plants, covering a wide range of species, systems and issues. In this paper, we present an overview of current trends and future directions in aquatic plant research in the early twenty first century. Our understanding of aquatic plant biology, the range of scientific issues being addressed and the range of techniques available to researchers have all arguably never been greater; however, substantial challenges exist to the conservation and management of both aquatic plants and the ecosystems in which they are found. The range of countries and continents represented by conference delegates and authors of papers in the special issue illustrates the global relevance of aquatic plant research in the early twenty first century but also the many challenges that this burgeoning scientific discipline must address.

The Sundarban, covering about one million ha in the delta of the rivers Ganga, Brahmaputra and Meghna is shared between Bangladesh (~60%) and India (~40%), and is the world’s largest coastal wetland. The area experiences a subtropical monsoonal climate with an annual rainfall of 1,600–1,800 mm and severe cyclonic storms. Enormous amounts of sediments carried by the rivers contribute to its expansion and dynamics. Salinity gradients change over a wide range of spatial and temporal scales. The biodiversity includes about 350 species of vascular plants, 250 fishes and 300 birds, besides numerous species of phytoplankton, fungi, bacteria, zooplankton, benthic invertebrates, molluscs, reptiles, amphibians and mammals. Species composition and community structure vary east to west, and along the hydrological and salinity gradients. Sundarban is the habitat of many rare and endangered animals (Batagur baska, Pelochelys bibroni, Chelonia mydas), especially the Royal Bengal tiger (Panthera tigris). Javan rhino, wild buffalo, hog deer, and barking deer are now extinct from the area. Large areas of the Sundarban mangroves have been converted into paddy fields over the past two centuries, and more recently into shrimp farms. The Sundarban has been extensively exploited for timber, fish, prawns and fodder. The regulation of river flows by a series of dams, barrages and embankments for diverting water upstream for various human needs and for flood control has caused large reduction in freshwater inflow and seriously affected the biodiversity because of an increase in salinity and changes in sedimentation. Heritiera fomes (locally called Sundari, from which Sundarban derives its name), Nypa fruticans and Phoenix paludosa are declining rapidly. During the past three decades, large parts of the remaining Sundarban have been protected for wildlife, particularly tiger, through the creation of several sanctuaries and a biosphere reserve. Parts of the Sundarban in both India and Bangladesh have been declared World Heritage sites. However, its biodiversity continues to be threatened by a growing human population that not only places pressure on its biological resources, but also impacts on the freshwater inflows from upstream areas. Oil exploration in coastal areas is also emerging as a new threat. Further threats arise from global climate change, especially sea level rise. The future of the Sundarban will depend upon the management of freshwater resources as much as on the conservation of its biological resources.

Artificial macrophytes were experimentally deployed in Boadella Reservoir (NE Spain) and assessed for fish use throughout the first 3 months of the 2007 summer drawdown. In total, 1,832 individuals of seven fish species were recorded through visual censuses, with introduced perch Perca fluviatilis being the prevalent species. Fish richness and abundance were significantly higher in artificial macrophytes than in rocky shores and sandy beaches, displaying a unimodal variation through time. P. fluviatilis, Rutilus rutilus and Abramis brama were significantly more abundant in artificial macrophytes than in the other two naturally submersed habitats, where no individuals of these species were recorded. The abundances of Squalius laietanus, Lepomis gibbosus, Micropterus salmoides and Cyprinus carpio were overall greater in artificial macrophytes than in rocky shores but displayed significant habitat × time interactions. A decrease in predation risk was apparently the key-factor of the intensive use of artificial macrophytes by small fish (≤100 mm TL) in Boadella Reservoir, since most species reduced drastically or completely the use of submerged structures when body size increased. This study demonstrates that adding artificial structures mimicking aquatic macrophytes can be an interesting tool to mitigate the adverse effects of water level fluctuations on fish assemblages in structure-less and homogeneous ecosystems, and to understand the mechanisms affecting habitat use and species replacement.

Issues of the Study of Detritus in Aquatic Systems. A.P. Sadchikov, S.A. Ostroumov, Russian Journal of General Chemistry, 2017, Vol. 87, No. 13, pp. 3244–3249.

https://www.academia.edu/44042879/Issues_of_the_Study_of_Detritus_in_Aquatic_Systems_A_P_Sadchikov_S_A_Ostroumov_Russian_Journal_of_General_Chemistry_2017_Vol_87_No_13_pp_3244_3249

In this paper, we present the analysis of the ecological roles of detritus and suspended particulate matter in aquatic ecosystems. New data that have been obtained for freshwater ecosystems of the central part of Russian Federation (Moscow Region, e.g., Mozhaiskoe Reservoir) have been included in the analysis. These new data include the results of studies of samples of water and detritus from the aquatic ecosystems. The review analysis addresses both freshwater and marine ecosystems. The multifunctional important role of detritus in aquatic ecosystems has been shown and exemplified using data for aquatic bodies of different trophic level, from oligotrophic to eutrophic.

Pigment concentrations (chlorophylla, chlorophyllidea and pheopigmentsa) were measured by HPLC and spectrophotometry with acidification on 57 samples collected in different marine coastal sediments, containing autochthonous microphytes, and with various organic matter contents (plant detritus, biodeposits or hydrocarbons). Statistical analysis shows that the spectrophotometry with acidification, as compared to HPLC, gives reliable values for chlorophylla. Chlorophyllidea concentrations may be considered as negligible. Though spectrophotometric methods are sometimes questioned when applied to sediments they appear to give easy, quick and good estimates of Chla contents in benthic microphytes for hydrobiological studies in coastal areas.

There is tremendous diversity in species of phytoplankton. Yet one may expect some degree of commonality in the response of similar species to similar conditions. Functional groups are those sets of species that respond similarly to environmental conditions because they have similar properties. The identification of such functional groups can assist model-based prediction of the abundance of phytoplankton as a function of time, space, and environmental conditions. Functional groups can also assist limnologists in the analysis and presentation of field data. We identified functional groups of phytoplankton using a combination of prior knowledge (based on taxonomic divisions and measurable properties) and statistical cluster analysis of long-term, species-level data from three Swiss lakes of different trophic state. For this task, we used the taxonomic division as the basic unit of analysis. Each taxonomic group was subdivided into several further groups by analysing the occurrence pattern of each species of the group and grouping together species with similar patterns. The reasons for the occurrence pattern for each species within a group were then analysed based on the main properties of the species. The results of this analysis were used to merge groups that had similar occurrence for similar reasons across taxonomic boundaries. Groups with different occurrence patterns but similar properties were also merged. This led to suggestions for functional groups at multiple levels of aggregation. The resulting groups were used in a subsequent study for modelling phytoplankton in the three lakes used for this analysis. The general methodology of combining prior knowledge on properties with empirical evidence on occurrence should be useful for finding functional groups of phytoplankton in other lakes as well. Comparisons of studies across lakes can then contribute to the identification of universal functional groups of phytoplankton applicable to a broad class of waters.

In mid latitudes, such as the Mediterranean region, one consequence of global climate change will be a progressive shift of permanent to temporary water courses, altering the life histories of present species or making them disappear. Presented here is a study on the life history of a mayfly species, Serratella ignita, in two Mediterranean streams, one permanent and one temporary. The research focuses on life history parameters such as life cycle, nymphal growth pattern, feeding type, biomass and secondary production. The life cycle was univoltine, showing a fast seasonal nymphal growth during four months in the permanent stream and five months in the temporary stream, with a long egg stage with diapause. The cumulated day-degrees during nymphal growth were similar between streams. Both populations behaved mainly as gatherer-collectors, but the population from the temporary stream also played an important role as a scraper. Animal matter was also consumed by nymphs from both populations. Gut content analysis showed that both S. ignita populations were opportunist/generalists, where changes in diet were correlated with size. Biomass and secondary production were notably higher in the permanent stream, but they were also high in the temporary stream. These data show that S. ignita had a high fitness in both streams. Our results support the idea that species such as this one may cope with future global climate change by maintaining, or even increasing, their populations at the expense of more stenoecic species.

Two new species of the genus Cyclotella are presented which have been discovered during ecological and paleoecological research studies in the littoral zone of two small alkaline eutrophic lakes in France (Lake Paladru) and in Switzerland (Lake Le Loclat). These new species are namedCyclotella costei nov. sp. andCyclotella wuethrichiana nov. sp. Lors d'études écologiques et paléoécologiques sur le littoral de deux lacs alcalins (Lac Paladru, France et Le Loclat, Suisse), les auteurs décrivent deux nouvelles petites Cyclotelles:Cyclotella costei nov. sp. etCyclotella wuethrichiana nov. sp. Es werden zwei neue kleine Arten der Gattung Cyclotella beschrieben, die während ökologischen und paläoökologischen Studien im Litoral der zwei alkalischen Seen Lac Paladru (Frankreich) und Le Loclat (Schweiz) gefunden wurden. Diese beiden neuen Arten werdenCyclotella costei nov. sp. undCyclotella wuethrichiana nov. sp. benannt.

A key ecological role hypothesized for the hyporheic zone is as a refugium that promotes survival of benthic invertebrates during adverse conditions in the surface stream. Many studies have investigated use of the hyporheic refugium during hydrological extremes (spates and streambed drying), and recent research has linked an increase in the abundance of benthic invertebrates within hyporheic sediments to increasing biotic interactions during flow recession in a temporary stream. This study examined spatial variability in the refugial capacity of the hyporheic zone in two groundwater-dominated streams in which flow permanence varied over small areas. Two non-insect taxa, Gammarus pulex and Polycelis spp. were common to both streams and were investigated in detail. Hydrological conditions in both streams comprised a four-month period of flow recession and low flows, accompanied by reductions in water depth and wetted width. Consequent declines in submerged benthic habitat availability were associated with increases in population densities of mobile benthic taxa, in particular G. pulex. The reduction in the spatial extent of the hyporheic zone was minimal, and this habitat was therefore a potential refugium from increasing biotic interactions in the benthic sediments. Concurrent increases in the hyporheic abundance and hyporheic proportion of a taxon’s total (benthic + hyporheic) population were considered as evidence of active refugium use. Such evidence was species-specific and site-specific, with refugium use being observed only for G. pulex and at sites dominated by downwelling water. A conceptual model of spatial variability in the refugial capacity of the hyporheic zone during habitat contraction is presented, which highlights the potential importance of the direction of hydrologic exchange.