Marine (ocean) biology is the study of the function, biodiversity, and ecology of the animals and plants that live in the ocean. An organism’s function is how it lives and grows in its environment. Biodiversity refers to the wide range of species of plants, animals, and microorganisms such as bacteria that live in the ocean.
Ecology is the study of the relationships between organisms as well as the relationships between organisms and their environment. In order to do their work, marine biologists incorporate information and techniques from a broad range of disciplines, including chemistry, physics, geology (the study of rocks), paleontology (the study of fossils), and geography (the study of locations on Earth).
Many factors make the marine environment a unique place for animals and plants to live. The marine environment is fluid, which affects the way organisms move and breathe. A variety of chemicals are dissolved in the water that bathes marine organisms and many have special ways to use these chemicals or to prevent them from entering their bodies. Ocean water is salty, which affects the organism’s ability to obtain and hold water in its body.
The ocean has relatively constant temperatures, especially compared to land. This means that animals do not need to exert a lot of energy to stay warm. Sunlight generally reaches only the surface layers of the oceans so plants must live in surface waters in order to perform photosynthesis (process where they convert energy from the Sun into food).
History of marine biology
Greek philosopher and natural historian Aristotle (384-322 b.c.e.), is generally regarded as the first marine biologist. Aristotle believed that observation, along with induction and reasoning, would lead to an accurate understanding of the natural world. These pioneering ideas set the stage for the modern scientific method.
Aristotle identified, described, and named 24 species of marine worms and crustaceans (animals that have a hard external covering and jointed limbs like crabs, shrimp, lobsters), 40 species of molluscs (clams, scallops, oysters) and echinoderms (a group of invertebrate animals that includes sea stars, sea urchins, and sea cucumbers) and 116 species of fish. He also correctly identified whales and dolphins as mammals (warm-blooded animals that have hair and feed young with milk).
Between Aristotle’s time and the Renaissance (about 1500 c.e.), very little work was done in marine biology because most people assumed that Aristotle had already accomplished everything. In the sixteenth century, explorers made many important observations about marine life.
Alexander von Humboldt (1769-1859) was a German naturalist who journeyed through Central and South America identifying marine animals and plants. British sea captain James Cook (1728-1779) was a renowned explorer who traveled throughout the Pacific describing and identifying marine organisms.
In the nineteenth century, work in marine biology became more active. British naturalist Charles Darwin (1809-1882) studied many marine organisms during his travels aboard the H.M.S. Beagle (1831-1836). Darwin’s work led to the theory of evolution, a theory that the organisms best suited to their environment live and reproduce to eventually form new species while those not suited to the environment will die.
His work also led to a theory of how coral reefs form atolls (a type of island) and to a classification of barnacles (a type of crab that attaches itself to hard surfaces) that is still in use today. Edward Forbes was a British naturalist and one of the first scientists to focus his attention on organisms in the ocean.
His azoic theory put forward the idea that there was no life at depths below about 1,800 feet (554 meters). Although this theory was accepted as true for nearly a century, it was later proved to be false. The first large expedition to study life in the ocean was undertaken by the British ship H.M.S. Challenger between 1872 and 1876. The biologists aboard found and described a large number of new marine species.
During the twentieth century, great advances in marine biology occurred. Submersible submarines, the Self Contained Breathing Apparatus (SCUBA), and underwater photography allowed scientists to observe life throughout the oceans.
Technological advances have led to electronic instrumentation that measure the characteristics of the ocean such as temperature, salinity (saltiness), intensity of light, and concentrations of dissolved gasses that provides important information on the distribution of organisms throughout the oceans. Tracking devices that use satellites (instruments sent into orbit in order to observe Earth) to report the locations of large animals, such as whales, sharks, and tuna, are used to understand migration (travel) patterns.
Techniques from the fields of biotechnology (the use of modern equipment and tests to understand biological processes), molecular biology (the study of molecules within cells), neurobiology (the study of nerves), and biochemistry (the study of chemicals that are found in organisms) are used routinely to provide a greater understanding of marine organisms.
Types of organisms studied
Marine biology involves the study of all types of organisms that live in the ocean, from the very small to the very large. The patterns and distributions of microscopic organisms called plankton involve one area of research. Plankton include viruses (small molecules like DNA or RNA that have the ability to reproduce when they are in a host), bacteria, phytoplankton (small plants that float in the ocean water) and zooplankton (small animals that float in the ocean).
Another focus of marine biology includes the larger animals called neckton that swim through the water. These animals include marine invertebrates (animals without a backbone) such as squid, most species of fish and marine mammals, such as dolphins and whales.
Another group of marine organisms are those that live on the ocean floor. These organisms are called benthic and can include animals and plants as well as microorganisms. Some examples of benthic plants include the giant kelp, sea grasses, and algae (plant-like organisms that photosynthesize, but have simpler bodies without veins) that grow on a thin layer on rocks.
Many invertebrates are benthic, like corals, sea anemones, sea cucumbers, sea stars, clams, snails, and crabs. A few fish that live close the bottom of the ocean are also considered benthic, such as halibut and some gobies. Many microorganisms, like bacteria and protozoans, are found in among the sand and clay at the bottom of the ocean.
Important research areas in marine biology
Marine biology contributes a large amount of information to the fields of environmental biology, economics, fisheries research, and biotechnology. Because the field is relatively young, there is still much to be learned from and about the animals and plants that live in the ocean.
Marine organisms influence local environmental conditions and economies. A simple, but powerful example of this is the red tide, which is usually caused by a particular type of phyto-plankton called a dinoflagellate. Under certain environmental conditions, these dinoflagellates grow extremely quickly, blooming in bays and near shore regions of the ocean.
In some instances they can cause fish kills and infect shellfish with poisonous substances, which could make the people that eat them sick. Much work is underway by marine biologists in order to understand the conditions that cause these harmful blooms so that they can predict their effects and when they will occur.
Many marine biologists study ways to improve mariculture, which is the farming of marine fish, shellfish, and seaweeds. Work includes developing types of animals and plants that are easy and economical to farm. For example, the triploid oyster is an oyster that has a longer harvest period than those found in nature. In addition, work is underway to improve the health of fish raised in pens and to decrease the pollution caused by marine farms.
Much research in marine biology contributes to the fields of biotechnology and molecular biology. Many marine animals and plants have been found to contain chemicals with industrial uses. For example, some phytoplankton produce sunscreens that can be incorporated into lotions.
Other marine invertebrates produce chemicals that are mixed with paint to discourage the growth of barnacles on ships and moorings. Molecular probes (special molecules that can identify other molecules) are used in marine ecology to detect the presence of harmful viruses and bacteria on beaches and near-shore waters.
Other techniques from molecular biology are used to determine if fish and marine invertebrates have been exposed to poisonous pollutants. Molecular biological techniques are also being used to analyze the DNA (genetic substance) in various marine organisms to try to understand the past relationships among species.