Factors Affecting Aquatic Ecosystems Part 1

Habitat Change

• Habitat change occurs naturally through droughts, disease, fire, hurricanes, mudslides, volcanoes, earthquakes, and slight changes in seasonal temperature or precipitation.
• Human activities like land use change, physical modification of rivers, and water withdrawal from rivers also induce habitat change.
• Habitat loss and fragmentation lead to saltwater intrusion into freshwater wetlands, causing shifts in plant and animal communities.
• Consequences of habitat change include:
  • Replacement of aquatic species with upland species
  • Loss of large, wide-ranging species (diversity loss)
  • Loss of genetic integrity when isolated habitats are too small to support viable populations
  • Increased numbers of competitor, predator, and parasite species tolerant of disturbed environments

Climate Change

• Climate change is a significant variation of average weather conditions over several decades or longer.
• It is attributed directly and indirectly to human activity, altering the composition of the global atmosphere.
• Observed changes over the 20th century include:
  • Increases in global air and ocean temperature
  • Rising global sea levels
  • Long-term sustained widespread reduction of snow and ice cover
  • Changes in atmospheric and ocean circulation, influencing seasonal rainfall conditions
• These changes are caused by extra heat in the climate system due to the addition of greenhouse gases from human activities.

Invasive Species

• Invasive species are alien species introduced outside their natural past or present distribution.
• They outcompete native species for resources like space, light, and food.
• They consume native species, compete with them for food or space, or introduce disease.
• Invasive species produce negative consequences in the environment and human health.
• They cause economic or environmental harm, disrupt native ecological processes, and lead to species extinction and loss of biodiversity.

Overfishing

• Overfishing, by-catch, and destructive fishing practices have depleted fisheries resources in Malaysia since 1970.
• The government has implemented the Fisheries Act 1985 for sustainable management of fisheries.

Industry and Agriculture

• Industrial activities have adverse effects on aquatic ecosystems, including:
  • Reduction of wetland acreage
  • Alteration of wetland hydrology
  • Water temperature increases
  • Point and nonpoint source pollutant inputs
  • pH changes
  • Atmospheric deposition
• Polynuclear aromatic hydrocarbons (PAHs) from industrial effluent and atmospheric deposition can enter estuarine wetlands, contaminating fish and causing external abnormalities.