- The distribution of life in the ocean
- > Finding answers to the question as to why marine organisms occur in their ancestral habitats and not elsewhere is a major challenge for science. The factors and mechanisms that determine the distribution of species in the ocean are not yet fully understood or documented. For marine animals, water temperature, food supply and interactions with other species are particularly important. But there are other factors at play that need to be considered.
Patterns of marine biodiversity
Determinants of success for marine biodiversity
If we want to conserve marine biodiversity, we need to understand which environmental factors significantly influence the distribution of species in the oceans. Scientists approach this question from two directions: Firstly, they collect and analyze data on the occurrence of species and habitats. They produce distribution maps and seek to recognize patterns and decipher the local conditions to which these patterns are attributable. At the same time, they look at the principles of how microbial, animal and plant life works and try to derive laws. However, whether or not these conceptual explanations do apply to all marine organisms must then be thoroughly tested. This is a task that has not yet been fully accomplished. Our knowledge of the key drivers of species richness and the geographical distribution of marine life is therefore still incomplete. Empirical evidence of the interactions between different environmental factors and the mechanisms behind them is still lacking in some cases or is the subject of controversial debate in the scientific community.
The geographical distribution of animals in the ocean is best understood. Which species can settle where in the sea and find sufficient food is determined by the ambient temperature and availability of oxygen, the overall food supply in the habitat and its complexity. This refers in particular to parameters such as habitat structure and interactions between its inhabitants.
The interplay of all these key factors provides ample explanation of why a much higher number of species live in the light-filled coral reefs of the marginal tropics than in the surface waters of temperate latitudes or the polar seas. At the same time, it is clear that there are exceptions to this rule – such as marine mammals, for example, whose bodies are not dependent on the ocean temperature, and the special case of deep-sea organisms. Because the latter live in marine regions with comparatively stable water temperatures, the food factor plays a much more existential role for them than for organisms in surface waters.
Such detailed knowledge of the geographical distribution of marine species, communities and ecosystems is urgently needed. It helps in the planning and implementation of conservation measures and provides a starting point for the early detection of climate-related changes in marine biodiversity and for the implementation of the best possible adaptation measures.