Macrophyte and macroinvertebrate patterns in unimpacted mountain rivers of two European ecoregions

Authors

Krzysztof Szoszkiewicz, Szymon Jusik, Iga Lewin, Izabela Czerniawska-Kusza, Jerzy Mirosław Kupiec, Marta Szostak

The aim of the study was to compare the patterns of development of macrophytes and macroinvertebrates in different types of reference mountain rivers. The study is based on reference river sites surveyed throughout the mountains in Poland and Slovakia in two European ecoregions (9—Central Highlands, 10—The Carpathians). A wide range of environmental variables were estimated, including water chemistry, hydromorphology, geology, and the spatial factor. Based on the Jaccard index, macrophyte and macroinvertebrate variation was confirmed between four mountain and upland river types. It was found that the biological diversification is mainly influenced by geological and associated chemical factors. In the case of macroinvertebrates, additionally, the importance of the spatial factor was revealed (difference between ecoregions). Finally, the habitat preferences of various taxa were identified. It was found that extreme mountain conditions can sometimes distort bioindicative response, as was detected in the case of macroinvertebrates in the highest mountain sites. We concluded that consideration of two groups of organisms enables more comprehensive and reliable monitoring than assessment based on a single group, especially when standard bioindicative methods can be distorted by extreme local conditions.

Characteristics of the elemental stoichiometry of submerged macrophytes and their relationships with environments in Honghu Lake (China)

Authors

Huang Wenmin, Liu Jinling, Shi Qiao, Xing Wei

Ecological stoichiometry is the study of the balance of energy and elements in ecological interactions. We investigate 18 representative sampling sites in Honghu Lake (China) here to compare the elemental stoichiometry of submerged macrophytes and the corresponding environments in different parts of a large lake. We hypothesized that differences in elemental concentrations of water and sediments between the western and eastern parts of Honghu Lake can cause significant differences in the elemental stoichiometry of submerged macrophytes between the western and eastern parts. At the species level, significant differences in tissue C, C:N and C:P ratios of Potamogeton pectinatus and Myriophyllum spicatum are found between the western and eastern parts of Honghu Lake. Significant differences in the tissue N of P. pectinatus are found between the two parts of the lake, whereas no significant difference in tissue P of submerged macrophyte species is found between the two parts. A markedly higher tissue C and C:P is found in the western part of the lake compared with that in the eastern part. Pearson correlation analysis showed the significantly positive correlation between tissue C:P and sediment N (r = 0.76, p < 0.01), as well tissue N:P and sediment N (r = 0.86, p < 0.01), which suggest that sediment N is closely related with the elemental stoichiometry of submerged macrophytes in Honghu Lake. In addition, the submerged macrophytes had significant effects on sediment N and sediment N:P at the whole-lake level. Based on these results, we successfully tested our hypothesis, and conclude that the elemental stoichiometry of submerged macrophytes can vary spatially within lakes, which is probably the result of differences in sediment N availability.

The use of Chara spp. (Charales: Characeae) as a bioindicator of physico-chemical habitat suitability for an endangered crayfish Austropotamobius pallipes in lentic waters

Authors

David Beaune, Yann Sellier, Élisabeth Lambert, Frédéric Grandjean

1. Austropotamobius pallipes is an endangered decapod attracting much attention in freshwater conservation programmes. In some cases population transfers or reintroductions are carried out in lentic ecosystems such as ponds or quarries. Such conservation actions require rapid, low cost and powerful tools to census suitable habitat.
2. Some species of the Characeae family (Chara spp.), share ecological needs with A. pallipes and are proposed as bioindicators of suitable habitat. Chara species were tested, among other plants, as bioindicators, and to see whether Chara species are a stronger indicator than water chemistry.
3. The Pinail Nature Reserve, with 3000 permanent ponds, is inhabited by white-clawed crayfish probably introduced historically into ponds used for fish production. This allows a replicated study of suitable habitats where plant communities are bioindicators of crayfish presence.
4. Crayfish presence is associated with Chara species (such as Chara aspera, Chara virgata, Chara fragifera, Chara polyacantha and Chara vulgaris). Austropotamobius pallipes is present in ponds with Chara spp. (N = 10/10) while other ponds without crayfish are lacking charophytes (N = 1/23). Algae of the genus Chara are thus a simple and low-cost additional tool for determining suitable habitat for crayfish introductions within enclosed waters protected from exotic invasive species and disease. Cladium mariscus also appears to be another useful bioindicator for crayfish habitat.

Recovery of lake vegetation following reduced eutrophication and acidification

Authors

Lars Baastrup-Spohr, Kaj Sand-Jensen, Sissel C. H. Olesen, Hans Henrik Bruun

1. In recent decades, many aquatic ecosystems in Europe and North America have experienced reduced inputs of nutrients and acidifying substances because of improved sewage treatment and reduced emission of sulphur oxides. We evaluated the consequences of these efforts to changes in water chemistry, species richness and community composition of aquatic macrophytes in 56 lakes in Denmark around 1990 and again around 2010.
2. Reductions in lake water concentrations of phosphorus and nitrogen were strongest in eutrophic and hypertrophic lakes, for example, lakes which had been heavily affected by domestic sewage. These changes translated into decreased algal biomass in the most eutrophied lakes. Oligo- and mesotrophic lakes did not change significantly in terms of nutrients or algal biomass. Water clarity increased across all lakes but not significantly in specific trophic lake groups. Alkalinity and pH increased significantly (up to 2 pH-units) in low-alkaline lakes, while well-buffered high-alkaline lakes (>0.5 meq/L) did not show any change.
3. Macrophyte species richness per lake increased, on average, by 13% during the 20-year study period. The increase was strongest in species preferring nutrient-rich conditions and could be directly attributed to reductions in phytoplankton biomass in lakes of medium water clarity. The similarity among all lakes in terms of species composition increased over the study period. This development was closely related to higher average species richness and was mainly caused by recolonisation of lakes, recovering from past eutrophication, by relatively common species (e.g., Lemna trisulca, Sparganium emersum and Potamogeton berchtoldii). Higher pH in low-alkaline lakes was accompanied by a shift from acid-tolerant to more acid-sensitive species.
4. Our results demonstrate that investment in pollution control has been successful in terms of markedly improving water quality of lakes and, with a time lag, macrophyte species richness. Although relatively common species have spread across lakes and resulted in homogenised macrophyte communities, continued efforts to reduce pollution could ensure the survival of rare specialist species and perhaps even increase their abundance in the future.

Identifying riparian vegetation as indicator of stream water quality in the Gilgel Gibe catchment, southwestern Ethiopia

Authors

Tibebu Alemu, Tadesse Weyuma, Esayas Alemayehu, Argaw Ambelu

Riparian land use has substantial effects on aquatic habitats and biological communities resulting in a dramatic loss of natural riparian vegetation and affecting the physicochemical properties of streams. The study investigates the relationships among indigenous riparian plants and water quality in the upper Gilgel Gibe catchment in southwestern Ethiopia. The floristic composition of the riparian vegetation and the water quality of streams were studied at selected sites, ranging from first to third order streams. We quantified relationships between disturbance level and both physicochemical characters and traits of riparian plant species during two sampling periods (December 2013 and April 2014). Data were collected from a priori designated three land use types (forest, plantation and agriculture) and ranked along nine streams. Ranks were based on surrounding land use characteristics and deforestation categories. We used analysis of variance (ANOVA) and the Tukey’s post-hoc test to conduct pair-wise comparisons among different land use types. Both species richness and diversity values of forest sites were significantly (p<0.001) higher than agricultural sites. Whereas, stream water quality deterioration indicator gradient such as total suspended solid (TSS), water turbidity, and orthophosphate were significantly (p<0.001) higher in agricultural sites than forest sites. We identified species such as Croton macrostachyus, Ficus sur, Maytenus arbutifolia, and Millettia ferruginea as indicator species of water quality (p<0.05). Our study is the first assessment of the role of indigenous plant species as indicator of highland stream water quality in the tropical area. The study contributes to the on-going discussion on the assessment and monitoring of stream ecosystems and for following stream restoration projects in tropical regions around the globe.

Plant Species Diversity in Restored and Created Delmarva Bay Wetlands

Authors
Kimberley N. Russell, Vanessa B. Beauchamp

A primary goal of wetland restoration is to produce biologically diverse and resilient habitat, often to mitigate losses elsewhere. Many factors influence wetland biodiversity including hydrologic regime, soil chemistry, texture, and microtopographic variation. A better understanding of these relationships can provide valuable information to practitioners. This study sampled plant communities of eight created or restored Delmarva Bay wetlands a decade after project completion to identify drivers of plant diversity at multiple scales. Study wetlands varied in terms of size, hydroperiod, soil fertility, coarse woody debris application, and straw mulch type. Wetlands with shorter hydroperiods had higher herbaceous plant diversity, but both herbaceous and woody diversity declined as soil fertility increased. Coarse woody debris density was not related to any of the diversity variables measured. There was no difference in species richness, soil carbon, total N, C:N or exotic species cover between wetlands treated with wheat or barley straw. We found that alpha and beta diversity were significantly correlated with different independent variables in our study and were not intercorrelated, suggesting that beta diversity may be an additional tool to assess diversity in heterogeneous habitats like depression wetlands.