Macrophytes indicators

BCF factors in fish ranging from 1.08 to 1.85, indicating that bioconcentration of methyl parathion is not an important fate process (Crossland and Bennett 1984). In another study, methyl parathion was added to the water of a carp-rearing pond and the concentration of methyl parathion was measured in water, soil, macrophytes, and carp over a 35-day period. Results showed that methyl parathion accumulated in macrophytes for 1 day and in carp for 3 days following exposure, and then dissipated. The concentrations of methyl parathion decreased in macrophytes by 94% by day 35 and by 98% in carp tissue by day 28 (Sabharwal and Belsare 1986). These data indicate the potential for biomagnification in the food chain is likely to be low because methyl parathion appears to be metabolized in aquatic organisms. 

Allelochemic effects of aquatic macrophytes on algae are discussed. Bloassays of chromatographic fractions from Eleocharls mlcrocarpa Torr. Indicate that oxygenated fatty acids are the causative agents. Methods of Isolation of these materials from aquatic macrophytes and from natural waters are described. Purification and structure determinations show that prominent components of the fraction are C q tri-hydroxycydopentyl and hydroxycydopentenone... 

Wong and coworkers118 analyzed fish and other environmental samples (clam, macrophytes, sediments and waters) from areas upstream and downstream from alkyllead manufacturing sites beside the St. Lawrence and St. Clair Rivers, Ontario, and found a clear indication of elevated alkyllead levels in samples near the industries. Most species of fish contained alkyllead compounds with tetraethyllead and triethyllead as the predominant forms. Most fish from the contaminated areas contained 70% or more of the total lead as alkyllead. Average alkyllead levels varied from year to year but declined steadily after 1981. For example, the mean value of alkyllead in carp from the St. Lawrence River decreased from 4207 H g kg-1 in 1981 to 2000 H g kg-1 in 1982 and to 49 Xg kg 1 in... 

Fig. 1. Model depicting nitrogen flows in a kelp bed community. Primary production by macrophytes is partitioned into particulate (POM) and dissolved (DOM) components. Filter-feeders feed on detritus consisting of POM, bacteria and animal faeces. Recycling of nitrogen via the feedback loop provided by faeces is indicated by heavy lines. Fig. la) shows the model under downwelling conditions, when phytoplankton is imported with surface water from offshore. Fig. lb) shows the model under upwelling conditions when it is assumed that phytoplankton in the upwelling water is negligible and excess detritus is exported in surface water.

FIGURE 1 Fate and major transformation pathways of phytoplankton- and macrophyte-derived DOM in aquatic systems. Arrows indicate fluxes POC denotes particulate organic matter LMW and HMW DOM refer to the monomeric (low molecular weight) and polymeric (high molecular weight) fractions, respectively. 

As with phytoplankton, macrophytes generate DOM either through extracellular release of photosynthate or following aging and subsequent release of dissolved and particulate constituents to the surrounding water. Information about extracellular release of DOM from macrophytes is scant. Available data indicate that extracellular release varies widely, with esti-... 

Cole, M. L., Kroeger, K. D., McClelland, J. W., and Valiela, 1. (2005). Macrophytes as indicators of land-derived wastewater Application of a 5 N method in aquatic systems. Water Resour. Res. 41, W01014, doi 10.1029/2004WR003269. 

The chemical and biochemical behaviors of humic substances can also be changed by GPC. Frimmel and Sattler (1982) studied the complexation/ adsorption of trace metals by dissolved humic substances and discovered that the affinity of humic substances for metals markedly increased following GPC. Similarly, Stewart and Wetzel (1982) observed that all Sephadex G-lOO fractions of dissolved humic material obtained from the aquatic macrophyte Typha were more stimulatory to C assimilation by algae than were the same humic substances that had not been fractionated. The observations indicated that the gel, eluent, or processing procedure (e.g., lyophilization, reconstitution, cleavage during separation) either reduced the toxicity of the humic substances or enhanced its stimulatory nature or affinity toward trace substances. 

High precursor concentrations, coupled with an abundance of phenolic materials, suggest that humification should be readily observable in estuaries. There are indications that humification may occur in the dissolved phase, particularly if algal exudates are abundant. Macrophytic debris may be an important site for humification. Sediment humification processes have been suggested on the basis of downcore increases in high-molecular-weight DOC, along with stable isotope data. However, the actual or relative importance of all these sites of humification in estuaries has yet to be demonstrated. 

Traditionally, lake monitoring has focused on physico-chemical parameters (nutrients, oxygen profiles, etc.) and on phytoplankton biomass as indicated by chlorophyll a, on which several classification schemes exist (e.g. OECD, 1982 Cailson, 1977). Only recently, following the new requirement introduced by the WFD to assess lake ecological status (see Cardoso et al., 2006 for a review) have most European countries included several other biological quality elements in their routine monitoring programmes, such as phytoplankton, macrophytes and phytobenthos, benthic invertebrates and fish. 

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