Macrophyte Index Research Articles

The Trophic Index of Macrophytes (TIM) – a New Tool for Indicating the Trophic State of Running Waters

AbstractIn running waters, apart from structural degradation, nutrient input becomes increasingly important. To investigate the indicator values of as many species of submerged macrophytes as possible numerous samples of the sediment within macrophyte stands and the overlying water were taken in running waters throughout Bavaria, Germany. To develop the Trophic Index of Macrophytes (TIM), the concentrations of soluble reactive phosphorus of both the water body and the sediment pore water were used. Based on a weighted sum of the SRP‐concentrations of the water body and the sediment pore water, indicator values were determined for a total of 49 species of submerged macrophytes. A detailed method is described on how and depending on which preconditions the trophic state of running waters can be determined by the TIM. An example of the TIM in the stream Rotbach is given. It shows that the TIM is a useful means to detect differences in the phosphorus loading of running waters.

Trophieindikation in Fließgewässern — Erprobung des Trophie-Index Makrophyten (TIM) im Fließgewässersystem der Sempt (Bayern)

The macrophyte vegetation of the river Sempt and its major tributaries was mapped and the nutrient concentrations of both the water body and the sediment were measured. By cluster analysis the mapping sections were grouped into four zones which differed in flowing velocity and degree of shading. The phosphorus concentrations of the water body also show differences between these zones. In every mapping section the Trophic Index of Macrophytes (TIM) was calculated according to Schneider (2000) . In the river Sempt and its tributaries the TIM is not influenced by varying composition of species resulting from different flowing velocities or varying degrees of shade. Even with a generally high supply of phosphorus from the sediment TIM is a useful means to detect differences in the phosphorus concentrations of the water body.

Comparative monitoring of diatoms, macroinvertebrates and macrophytes in the Woluwe River (Brussels, Belgium)

The river Woluwe in Brussels and Flanders (Belgium) is a small tributary of 15 km length that drains an area of 9400 ha in the Schelde river basin. The headwaters of the Woluwe are highly fragmented by diverse pond systems and are vaulted in the Brussels agglomeration. Hyporheic zones locally influence the water quality. The downstream stretch of the river receives sewage waters from households and industry. As the river Woluwe within a short distance represents a typical gradient from groundwater-fed sources in the forest towards severely polluted water, a comparative monitoring using diatoms, macroinvertebrates and macrophytes was done. The saprobic index based on diatoms, the Belgian Biotic Index (BBI) for macroinvertebrates and a macrophyte index based on the N-values of Ellenberg were used in this comparison and for estimating the correlation with the bimonthly measured chemical variables in 16 sampling stations. The diatom saprobic index and the macrophyte index were strongly correlated. Both groups showed strong correlations with phosphate, ammonium and chemical oxygen demand. The Belgian Biotic Index showed lower correlations with the nutrient variables, but was slightly better correlated to chemical oxygen demand, chloride and dissolved oxygen. None of the indices showed a correlation with nitrate. Local substrate or light conditions could interfere with the indicator system, especially for the macrophytes and occasionally for the macroinvertebrates. It was concluded that at least in this particular river system, the indices based on the primary producers were more indicative for the trophic status, whereas the BBI showed a broader relationship to the general degree of pollution. Therefore, these three indices are considered as complementary for monitoring the biological quality and the ecological status of a river system.

Combination of two indication systems in pre-alpine lakes — diatom index and macrophyte index

Since the climax of eutrophication in the early 1980s mainly greater lakes have been investigated and monitored in terms of their nutrient charge. In the future there will still be a need to develop guidelines for monitoring the trophic status of smaller lakes. Four small lakes were investigated by the author in the years 1996 and 1997. In order to define the nutrient charge of those lakes more precisely, special emphasis has been put upon the two criteria diatoms and macrophytes. Eventually an evaluation of the lakes' catchment areas will also be an important component of these studies. Benthic diatoms are the main part of periphyton. As unicellular fast reproducing organisms they are excellent indicators for trophic situations in lakes. The diatom index denotes the trophic status of the littoral zone during the last few weeks before sampling. The macrophytes, however, reflect the nutrient charge over a longer period, i.e. several years. The macrophyte index is based on the fact that some species are most prevalent at certain nutrient loads. The effort to combine these two indication systems carries a high resolution of spatial nutrient changes as well as in temporally changes.

Changes in the water quality of Lake Geneva indicated by submerged macrophytes

SUMMARY 1. The distribution of submerged macrophytes along 20 km of lake shore (Lake Geneva, Switzerland) was compared between the years 1972, 1984 and 1995. Lake Geneva underwent rapid eutrophication until 1980, followed by reversal that is still in progress. Potamogeton pectinatus, P. perfoliatus, P. lucens and Elodea canadensis showed no significant changes in their distribution, with the two former species dominant throughout. Chara sp., and to a lesser degree Myriophyllum spicatum, decreased in abundance between 1972 and 1984 but had increased again by 1995. The abundance of P. pusillus increased regularly, while Zannichellia palustris and P. crispus almost disappeared from the study area. Elodea nuttallii was observed for the first time in Lake Geneva in 1995. 2. Two methods of bioindication of water quality by macrophytes are compared. The macrophyte index proposed by Melzer (1988) is based on nutrient load, whereas the saprobic index proposed by Sladecek (1973) measures organic pollution. The saprobic index is sensitive to small changes in species composition and abundance, and also reflects better the changes in eutrophication. It may therefore be a better bioindicator. 3. Geographic Information Systems (GIS) are useful for mapping and storing information on submerged vegetation allowing easy interrogation, updating and plotting of spatial information at various scales, and providing a reference for future comparisons.

Aquatic macrophytes as tools for lake management

Aquatic macrophytes can serve as useful indicators of water pollution along the littoral of lakes. In Bavaria, the submerged vegetation of about 100 lakes has been investigated by SCUBA diving over the past decade to evaluate the state of nutrient pollution. All lakes are marl lakes located in the northern calcareous alps and the prealpine region. The lakes differ in size, morphology, water residence time, nutrient loading, trophic status, recreational activities, and other characteristics. In all cases the entire shoreline of the lakes has been investigated. Among the investigated lakes are the three biggest Bavarian lakes, i.e. Lake Chiemsee, Lake Starnberg and Lake Ammersee. Mapping of the submerged vegetation occurred in four different depth zones, and variable shoreline sections. The length of each section was determined by the uniformity of the vegetation; as it changed, a new section was designated. Within each section and zone species were recorded and abundance of all observed macrophytes was estimated semi-quantitatively on a five-point scale. Nine different groups of macrophytes were recognised, including, in total, 45 different species of macrophytes. On the basis of this catalogue of indicator species, in combination with the abundance of the species, a ‘macrophyte index’ was devised, which ranges from 1 (unpolluted) to 5 (heavily polluted). Six groups of values of the macrophyte index, each represented by a different colour or grey-scale (in this publication), are presented to allow a clear illustration of the results. Important information for the successful restoration of lakes in Upper Bavaria has been obtained from the distribution patterns of the submerged vegetation. Many unknown waste water inflows or diffuse sources could be detected due to abrupt changes in the macrophyte index. Furthermore, the success of waste water removal by ‘ring canalisation’, resulting in a re-oligotrophication of many Bavarian lakes can be followed by changes in the macrophyte index.

Littoral zone — GIS of Lake Constance: a useful tool in lake monitoring and autecological studies with submersed macrophytes

In 1993, the submersed vegetation of the whole littoral zone of Lake Constance was mapped by boat on the basis of aerial photographs. The survey was the third of its kind after 1967 and 1978, including a period of fast eutrophication in the 1960s and 1970s (mainly caused by increasing phosphate concentrations) and a subsequent period of decreasing trophy, due to the international efforts of the countries and states in the catchment area in eliminating phosphate from waste water. The change in distribution of most aquatic macrophytes shows a high relation to the changes in trophic status of the lake. The oligotraphentic species Chara contraria Kützing decreased in the 1960s and 1970s and increased in the 1980s and 1990s, the eutraphentic species Zannichellia palustris L., a very rare species before the 1970s, increased to one of the most dominant species until the late 1970s, but decreased in the 1980s and was rarely found in 1993. The use of GIS for data storage and analyses enabled to plot geographically referenced maps of single species distribution areas, to analyse changes of distribution area of species based on data from the whole littoral zone of the lake and to calculate summarising indices like a macrophyte index of nutrient load in the littoral zone. GIS-based analyses of whole lake above ground biomass and depth niches of selected species for the mappings of 1978 and 1993 show, that the difference in aboveground biomass of Potamogeton pectinatus L. is small, but distribution area and depth distribution are wider, whereas density of stands is lower in 1993. Potamogeton perfoliatus L. in 1993 has a higher aboveground biomass, a wider distribution area and depth distribution and a deeper depth optimum than in 1978

Failure of Submersed Macrophytes to Provide Cover for Rainbow Trout throughout Their First Winter in the Henrys Fork of the Snake River, Idaho

Abstract Submersed aquatic plants that are abundant in some stream reaches have a potential to provide winter concealment cover for juvenile salmonids. We monitored an index of macrophyte abundance in a portion of the Henrys Fork of the Snake River during two winters that differed in severity and assessed the densities of age-0 rainbow trout Oncorhynchus mykiss associated with the macrophytes. The macrophyte index averaged 84–87%, in November 1989 and 1992, and an average of 10–13 fish/100 m2 were concealed there. In 1990, macrophyte cover declined to 59% in January and 46% in early February; fish density declined by about one-third by January and dropped to nearly zero in February. In 1992–1993, the macrophyte index declined to an average of 39% following anchor ice formation in December and to 32% in January. Fish density in December was reduced to about half of the November density and to about 1 fish/100 m2 in January. Movement of marked fish in 1989–1990 was predominantly from macrophytes into cobble...