Dr. ASMA ALI (Ecologist)
Plants are described as aquatic, if the plant parts involved in photosynthesis are submerged or float on the water surface either permanently or at least for several months each year. The term macrophytes referred to all plants large enough to be visible to the necked eye, not only flowering plants but also ferns, brayophytes and algae.
In view of their varying requirements, the composition of macrophyte species in a water body makes it possible to draw conclusions about a local chemical and physical conditions. Species that prefer low nutrients concentrations, in particular, have become much less prevalent. Also in decline of species that are dependent on natural river banks withstanding and gravely substrate. Aquatic plants are especially sensitive to changes in nutrient concentrations and to organic pollutants.
[A] Aquatic macrophytes as a link in the food chain
- Effect of fish grazing on nutrient release:-
Herbivorous fish have a limited ability to convert plant material into animal tissue and to remove excess nutrients from the system. But being relatively efficient grazers and insufficient assimilators, they may play a significant part in initiating the internal, biologically mobilized nutrients source, or accelerate their recirculation. Thus, if with advancing eutrophication, the rate of macrophyte consumption increases due to the increase in number of herbivores, a new part of their biomass may finally be converted into additional algal biomass- the main troublemaker in lake of the temperate zone. Considerable information is available on the impact of grass carp grazing on water quality. Grass carp partially digest its food and the faeces are a large source of nutrients. Nutrients are readily utilised by phytoplankton, resulting in elevated algal Biomass, and in some situations leading to algal blooms.
2) Periphyton function:-
Periphyton is graze by a diversity of both invertebrate and vertebrate aquatic organisms. The invertebrates include molluscs, nematodes, microcrustaceans, amphipod and isopod crustaceans, crayfish, mysids, chironomid larvae, caddisfly and mayfly larvae. Invertebrate grazers may play an extremely important role in controlling Periphyton and showed cascading trophic interactions and also propose that fish predation on snails would enhance macrophyte biomass.
3) Zooplankton:-
Aquatic macrophytes provides shelter or refuge to zooplanktons, and the presence of especially large zooplanktons control small phytoplankton. If the larger zooplanktons becomes scare, the phytoplankton community will change to slow- growing bigger, mainly inedible blue-green species. These bigger, often colonial algae compete more successfully with the small algae for nutrients and establish high-density populations, sometimes leading to algal bloom. In turn ; this restrict light penetration into deeper water and leads to the death of submerged macrophytes.
4) Aquatic macroinvertebrates:-
Aquatic macrophytes are an important habitat for aquatic macroinvertebrates. The plants provide protection from predators and current, and are a direct and indirect source of food of fish and aquatic birds. In plant beds, benthic invertebrates are generally more numerous and more diverse than in open water. Indirectly, macrophytes are also important for the benthic macroinvertebrates, for which they provide protection against foraging by fish and aquatic birds, as well as providing the invertebrates with a supply of organic matter from the decomposing plants.
[B] The role of macrophytes in sustaining water level fluctuation:-
Shorelines are often defined by the relative influence of inflows of water, such as groundwater, precipitation and surface flow. The water level fluctuation of any water body is controlled by the water budget, as well as physical aspects of the surrounding environment such as soil permeability and most important the abundance of shoreline macrophytes, which directly modifies the physicochemical factors of the aquatic ecosystem such as soil makeup, redox potential and nutrient availability.
[C] The role of macrophytes in nutrient recycling among trophic levels and denitrification :-
Eutrophication of Lake water caused by excess nutrients level. Nonpoint source runoff from agricultural fields may contains high levels of nutrients, particularly nitrogen and phosphorus and can be a major contributor to eutrophication of water body. Water temperature and pH are driving factors in the rate of denitrification in an aquatic ecosystem and availability of carbon and nitrate work like a limiting factors. On the other hand various aquatic macrophytes also regulate nutrient level in aquous solutions.
Macrophytes are beneficial for nutrient mitigation since they are capable of some direct update in the water, increase hydraulic retention time by decreasing water flow, provide soil oxygenation and provides surface area for microbial biofilms. Macrophytes induced multiple beneficial effects for the conservation of the wetland, including sustaining water level, nutrients recycling among various trophic levels, provide shelter and growth to macro and micro invertebrates belonging to various orders.
Aquatic macrophytes interacts with the physico-chemical environment as well as the biological community. These Complex interactions determine the community which is present in every wetland. It is important to have a good understanding of the interactions between plants and their environment.
No comments:
Post a Comment