There are numerous unique and ecologically significant relationships between living things in the marine environment. These often involve the movement or transfer of energy from one organism to another. These complicated marine food webs are rich in productivity and are responsible for more than 90% of the photosynthetic activity on earth. Without this, life in the terrestrial environment would not exist.
Even in a hostile environment, such as the intertidal zone of a sandy beach, life can be present. Most of the organisms here have adapted to a burrowing existence. Small calms, mole crabs, and annelid worms live deep in the substrate and must survive varying physical conditions. Wave action, sand particle size, and oxygen concentrations will affect the distribution of life in this dynamic environment.
The water column is characterized by a large diversity of microscopic plant and animal plankton, at least in the upper 100 meters where light can penetrate. In fact, there could be thousands of single-celled algae, all photosynthesizing and providing the earth with most of its oxygen supply and marine animals with the energy needed to sustain their populations. Because of the size of the ocean and the abundance of algae, these species account for more than three-quarters of all “plant” life on earth.
All plants and animals have evolved strategies for survival or adaptations to the environment. In the case of phytoplankton, many species form chains or have appendages that enable them to float closer to the surface where there is ample sunlight for photosynthesis. Some animal species, such as marine crabs and sea stars, can regenerate or replace lost limbs and grow back after a short period of time. Fiddler crabs, a burrowing species, can breathe in water but can also store oxygen in gill chambers. Barnacles use their six pairs of legs to beat in the water and push food into their mouths. They are able to close up for protection from desiccation at low tide.
These systems also change over time, a process called succession. Marine environments can exhibit a complicated series of successional stages. Examine a rock jetty or groin for the presence of algae, barnacles, periwinkles, and mussels. Other species such as sea anemones and bryozoans may also be present. Some of the surfaces of the rocks may be completely bare, whereas other sections may contain a single uniform species or even a group of different species that are layered in separate zones. This form of patchiness is quite common and many factors contribute to the colonization of the area. The sweeping motion of algal fronds, the intensity of wave action, and the competitive interactions of species already present will affect the rate of colonization and distribution of other organisms. It’s not always predictable and it may vary from one rock interface to another. Sometimes it’s just a matter of who gets there first. The point is that the ecology of these mini-ecosystems is influenced by a convergence of both physical and biological conditions.
Copyright Gil Newton 2009 Thanks to Chris Dumas for logo image.