In broad terms, Ecology is the scientific study of how organisms interact with each other and with their environment (Hatfield 2008). Aquatic ecology includes the study of these relationships in all aquatic environments, including oceans, estuaries, lakes, ponds, wetlands, rivers, and streams.
An ecosystem is a community of living organisms and their physical and chemical environment, linked by flows of energy and nutrients. Ecosystems function as a discrete ecological unit, and can be defined at a variety of scales. For example, the Orange-Senqu River basin can be considered an ecosystem, as can a small pond, a log, or the entire planet. The boundaries of an aquatic ecosystem are somewhat arbitrary, but generally enclose a region for which inflows and outflows can be estimated. Ecosystem ecologists study how nutrients, energy, and water flow through an ecosystem.
The physical characteristics of aquatic habitats affect both the type and variety of organisms (biodiversity) found. Organisms in a particular environment are directly affected by its characteristics, such as nutrient concentrations, temperature, water flow, and shelter. Only those best adapted to these conditions, and best able to use the available resources, will thrive. Interactions between organisms also matter, as predation and competition for resources (e.g., food, habitat) affect species abundance and diversity. In turn, the organisms in an environment can influence some aspects of their environment.
Understanding aquatic ecosystems and the interaction between organisms and their environment can help manage human effects better. Key topics that will be discussed in this section include:
Chapter Summary
This chapter covers the following concepts and material:
- The principles of aquatic ecology and the aquatic ecosystems of the Orange-Senqu River basin
- The importance and functions of wetlands and their distribution in the Orange-Senqu River basin
- The ecoregions of southern Africa that fall within the Orange-Senqu River basin
- Endemic and invasive species and the threats that invasive species pose to the ecosystems of the Orange-Senqu River basin
- The principles laid out in the Millennium Ecosystem Assessment and the nature and importance of ecosystem goods and services
Orange River at Upington.
Source:Paffy 2006
( click to enlarge )
