page_title: Dispersal vector
section_title: Marine dispersal
hierarchical_section_title: Dispersal vector / Water dispersal / Marine dispersal
caption_attribution_description: English: Table icebergs are very rare in the Arctic as they calve from shelf ice, which is rarely found in the north. They are normally a typical form of icebergs in the Antarctic. This one has an estimated height of 10-12m and a size of half a soccer field. Deutsch: Tafeleisberge sind sehr selten in der Arktis zu finden, sie sind eigentlich eine typische Erscheinung für die Antarktis. Sie entstehen durch Kalbung von Schelfeis, das in der Arktis kaum vorkommt. Dieser Tafeleisberg ist geschätzte 10 bis 12m hoch und hat eine Fläche von etwa einem halben Fußballfeld.
context_page_description: A dispersal vector is an agent of biological dispersal that moves a dispersal unit, or organism, away from its birth population to another location or population in which the individual will reproduce. These dispersal units can range from pollen to seeds to fungi to entire organisms.
  There are two types of dispersal vector, those that are active and those that are passive. Active dispersal involves organisms that are capable of movement under their own energy. In passive dispersal, the organisms have evolved dispersal units, or propagules, that use the kinetic energy of the environment for movement. In plants, some dispersal units have tissue that assists with dispersal and are called diaspores. Some dispersal is self-driven, such as using gravity, and does not rely on external vectors. Other types of dispersal are due to external vectors, which can be biotic vectors, such as animals, or abiotic vectors, such as the wind or water.
  In many cases, organisms will be dispersed by more than one vector before reaching its final destination.
context_section_description: A majority of marine organisms utilize ocean currents and movement within the water column to reproduce. The process of releasing reproductive propagules into the water is called broadcast spawning. While broadcast spawning requires parents to be relatively close to each other for fertilization, the fertilized zygotes can be moved extreme distances. A number of marine invertebrates require ocean currents to connect their gametes once broadcast spawning has occurred. Kelp, an important group of sea plants, primarily utilize ocean currents to distribute their spores and larvae. Many coral species reproduce by releasing gametes into the water column with hopes that other local corals will also release gametes before these units are dispersed by ocean currents.
  Some non-submerged aquatic plant species, like palm trees and mangroves, have developed fruits that float in sea water in order to utilize ocean currents as a form of dispersal. Coconuts have been found to travel up to thousands of miles away from their parent tree due to their buoyant nature. A variety of over 100 species of vascular plants utilize this dispersal method for their fruit.
  Many plants have evolved with specific adaptations to maximize the distance that seeds, fruits, or propagules are dispersed in the ocean. For an increased protection against sinking in the water column, seeds have developed hair or slime on their outer seed coats. Seeds with filled with air, cork, or oil are better prepared to float for farther distances.
  Another aspect of dispersal comes from wave and tidal action. Organisms in shallower waters, such as seagrasses, become displaced and dispersed by waves crashing upon them and tides pulling them out into the open ocean.  
  Some smaller marine organisms maximize their own dispersal by attaching to a raft - a biotic or abiotic object that is being moved by the ocean’s currents. Biotic rafts can be floating seeds or fruits, leaves, or other propagules. Abiotic rafts are usually floating woods or plastics, including buoys and discarded trash.
  Sea ice is also an important dispersal vector. Some arctic species rely on sea ice to disperse their eggs, like Daphnia pulex. Drifting, as discussed above, can be an effective dispersal vector for marine mammals. It has been shown that intertidal benthic invertebrates will utilize sea ice as a raft to travel up to multiple kilometers.
caption: An iceberg that may act as a raft for arctic invertebrates.
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