Amount Of Fine Organic Matter Research Articles

Colonisation of leaf litter by aquatic invertebrates in an Atlantic Forest stream.

Riparian vegetation along streams in the Atlantic Forest in Brazil contributes to the formation of a highly heterogeneous leaf litter in streambeds. To investigate the structure and composition of the aquatic invertebrate community during the process of leaf decomposition of two plant species present along the banks of the stream studied, 21 plastic mesh bags containing 2.5g (dry weight) of leaf matter from each species (Alchornea glandulosa (Vell) and Cabralea canjerana End. and Poeppig), for a total of 5.0g, were placed in the streambed. Three bags were removed after 3, 6, 9, 12, 24, 48 and 96 days. The taxonomic density was negatively correlated with the remaining weight. The high density of collector organisms, such as Chironomidae, Oligochaeta and Amphipoda, on the last day of incubation, probably occurred due to the increased amount of fine organic matter in the more advanced decomposition stages. The highest α diversity (Shannon-Wiener) values were observed for the 3rd and 96th days of the experiment, while the β diversity values showed that these days presented the highest variation in the taxonomic composition, thus presenting a different faunistic composition. This study showed that the trophic structure and composition of aquatic invertebrates changes during the decomposition of leaf litter. The faunistic abundance and diversity observed in this study indicate that the entrance of material from plants growing along streams provides favorable conditions for the colonisation and establishment of invertebrates in lower-order streams, and thus points to the need to preserve riparian vegetation.

Rotenone Persistence Model for Montane Streams

AbstractThe efficient and effective use of rotenone is hindered by its unknown persistence in streams. Environmental conditions degrade rotenone, but current label instructions suggest fortifying the chemical along a stream based on linear distance or travel time rather than environmental conditions. Our objective was to develop models that use measurements of environmental conditions to predict rotenone persistence in streams. Detailed measurements of ultraviolet radiation, water temperature, dissolved oxygen, total dissolved solids (TDS), conductivity, pH, oxidation–reduction potential (ORP), substrate composition, amount of organic matter, channel slope, and travel time were made along stream segments located between rotenone treatment stations and cages containing bioassay fish in six streams. The amount of fine organic matter, biofilm, sand, gravel, cobble, rubble, small boulders, slope, pH, TDS, ORP, light reaching the stream, energy dissipated, discharge, and cumulative travel time were each significantly correlated with fish death. By using logistic regression, measurements of environmental conditions were paired with the responses of bioassay fish to develop a model that predicted the persistence of rotenone toxicity in streams. This model was validated with data from two additional stream treatment reaches. Rotenone persistence was predicted by a model that used travel time, rubble, and ORP. When this model predicts a probability of less than 0.95, those who apply rotenone can expect incomplete eradication and should plan on fortifying rotenone concentrations. The significance of travel time has been previously identified and is currently used to predict rotenone persistence. However, rubble substrate, which may be associated with the degradation of rotenone by adsorption and volatilization in turbulent environments, was not previously considered.

Moss- and mineral substrata-dwelling meiobenthos in two different low-order streams

The quantitative composition of permanent and temporary meiobenthos inhabiting an aquatic moss Fontinalis antipyretica and the surrounding mineral substrate in two different low-order streams was investigated, as were the amounts of fine organic and mineral matter trapped within both mesohabitats. Densities of moss-dwelling meiofauna were one order of magnitude higher than densities in the surrounding mineral bed. Total meiofauna in the third-order stream Bystřice (Czech Republic) were nearly 3-times more abundant than in the second-order stream Oberer Seebach (Austria), most likely reflecting the higher amount of fine organic matter in the Bystřice. Dominant meiobenthic groups in both streams and substrata were Rotifera, Chironomidae and Nematoda. However, Harpacticoida was the second most abundant group in gravel of the Oberer Seebach. Temporary meiofauna, mostly early-instar chironomid larvae, represented 40-60% of total meiofaunal densities. Most correlations between meiofaunal densities and trapped fine particles likely reflect passive deposition of meiofauna within investigated substrata. However, positive correlations between Monogononta, Nematoda, Oligochaeta, Harpacticoida and Chironomidae densities in moss and organic particles in the size range of 30-100 μm may indicate a feeding relationship. Fine organic matter biomass was significantly lower in moss compared to gravel in the Oberer Seebach; no significant difference was found in the Bystřice. We found an indication that the capacity of moss and surrounding mineral substrata in trapping fine organic particles in relation to flow velocity differed during the sampling period. Moreover, it is questionable whether F. antipyretica can serve as a refuge from current for stream meiobenthos.