Мarine biogeomorphology: biotic transformation of marine bottom landforms
Biogenic transformation is one of the leading factors responsible for the state of the modern sea bottom. The goal of marine biogeomprphology is to understand all of the processes responsible for biological modification of the sea bottom. This review includes description, classification and quantitative analysis of the influence of biota on the sea bottom landscapes. The living organisms create biogenic structures and marine sediments, change bottom landscape, and physical and chemical properties of sediments and bedrock. They participate in biological weathering, redistribution of sediments at the sea bottom and within the near-bottom layer, convert dissolved calcium and silica into stable carbonates and silicates. Examples of marine biogenic forms include coral and polycaetes reefs, mussel and oyster banks. The organisms create both, positive and negative marine landform that may reach 10 and more meters in size. Borrows, holes, ditches, funnels created by walruses, turtles, whales, scouts etc. may persist on the bottom from weeks to months. Micro and macro orga-nisms create notches at the sea level (bio-karst). Mangroves, algae and seagrass protect sea bottom from erosion and trap fine grain sediments. Fish transport sediments from reefs to lagoons. Macrophyte algae are capable to move cobbles and pebble size material to long distances (rafting). Many bivalve mollusks and other filter feeder organisms sieve mineralogic fraction filtering large volumes of water. Bioturbation performed by borrowing worms change physical and chemical properties, stabilize and compact marine sediments. The same species of organisms may both, increase and decrease strength properties of marine sediments. Diversity and variability of biological processes obstruct the understanding and quantitative assessment of the role of biota in geomorphological processes. With rare exceptions, the impact of single organisms on marine landscape is limited to a few cm, but integrated activities of organisms within the same habitat are causing noticeable changes. Practical applications of biogeomorphology are particularly useful in developing measures to protect coast from erosion.