Aquatic environments

Aquatic environments (marshes, ponds, ditches, canals, weirs, dams and wastewater treatment plants)

1. Identification and general characterisation

Aquatic environments encompass freshwater or brackish ecosystems, natural or artificial, including marshes, ponds, drainage ditches, irrigation canals, weirs, dams and wastewater treatment infrastructures. These systems present high hydrological, chemical and biological variability, performing essential functions in water regulation, natural purification, support to biodiversity and provision of ecosystem services.

2. Ecological and functional importance

These environments are fundamental for:

• maintenance of aquatic and riparian biodiversity
• support to biogeochemical cycles (carbon, nitrogen, phosphorus)
• retention and purification of nutrients and contaminants
• flood regulation and water storage
• habitat for species of ecological, economic or sanitary interest
• support to agricultural, industrial and urban activities (irrigation, supply, drainage, water treatment)

Their integrity directly influences water quality, public health and the balance of surrounding ecosystems.

3. Physical and biological characterisation

These systems present:

• Variable hydrology: still waters (ponds, weirs), currents (canals, ditches), or with intermittent flows.
• Depth and transparency: variable according to origin, management and nutrient load.
• Aquatic vegetation: submerged, emergent and floating macrophytes (e.g.: Typha, Phragmites, Lemna).
• Associated fauna: aquatic invertebrates, fish, amphibians, waterfowl and microorganisms.
• Key ecological processes: decomposition, sedimentation, aquatic photosynthesis, nutrient cycling.

4. Environmental requirements and conditioning factors

The quality and functionality of these environments depend on:

• water availability and flow regime
• water quality (nutrients, organic matter, pollutants)
• temperature and solar radiation
• soil and sediment characteristics
• presence of riparian vegetation
• anthropogenic pressure (agriculture, urbanisation, discharges, hydraulic works)

Eutrophic environments or those with low water renewal are more susceptible to proliferation of algae, mosquitoes and invasive species.

5. Main pests and problematic organisms

• Mosquitoes: Culex spp., Aedes spp. (proliferation in still waters).
• Aquatic snails: intermediate hosts of parasites.
• Invasive aquatic plants: Eichhornia crassipes, Azolla filiculoides, Elodea canadensis.
• Cyanobacteria: Microcystis spp. and other toxin producers.
• Invasive fish: Gambusia holbrooki and other opportunistic species.

6. Main diseases and associated risks

• Proliferation of cyanotoxins: associated with cyanobacteria blooms.
• Microbiological contamination: Escherichia coli, Salmonella spp., Giardia, Cryptosporidium.
• Vector-borne diseases: mosquitoes associated with stagnant waters.
• Rots and diseases of aquatic plants: Pythium and Phytophthora in waterlogged areas.
• Chemical risks: accumulation of heavy metals, pesticides and nutrients.

7. General environmental management

The management of these environments must include:

• regular monitoring of water quality (nutrients, oxygen, pH, contaminants)
• control of excessive or invasive aquatic vegetation
• maintenance of flows and water renewal when possible
• management of agricultural and urban discharges to reduce eutrophication
• mosquito control through environmental measures (removal of stagnant waters, improvement of circulation)
• protection of riparian vegetation for bank stabilisation
• maintenance and cleaning of ditches, canals and hydraulic structures
• adequate management of sludge in WWTPs and weirs

Bibliographic references

• EPPO Global Database – relevant invasive aquatic species.
• CABI – Invasive Species Compendium (various aquatic species).
• European Environment Agency (EEA) – reports on aquatic ecosystems.
• FAO – Guidelines for Integrated Water Resources Management.
• Wetzel, R. G. (2001). Limnology: Lake and River Ecosystems. Academic Press.
• Mitsch, W. J., & Gosselink, J. G. (2015). Wetlands. Wiley.