Laminaria

Laminaria is a genus of 31 species of brown algae commonly called 'kelp'. Some species are also referred to as tangle. This economically important genus is characterized by long, leathery laminae and relatively large size. Some species are referred to by the common name Devil's apron, due to their shape, or sea colander, due to the perforations present on the lamina. It is found in the north Atlantic Ocean and the northern Pacific Ocean at depths from 8 to 30 m (26 to 98 ft) (exceptionally to 120 m (390 ft) in the warmer waters of the Mediterranean Sea and off Brazil). Laminaria form a habitat for many fish and invertebrates.  The life cycle of Laminaria has heteromorphic alternation of generations which differs from Fucus. At meiosis the male and female zoospores are produced separately, then germinate into male and female gametophytes. The female egg matures in the oogonium until the male sperm fertilizes it. Life-Cycle: The most apparent form of Laminaria is its sporophyte phase, a structure composed of the holdfast, the stipe, and the blades. While it spends its time predominately in the sporophyte phase, it alternates between the sporophyte and its microscopic gametophyte phase. Laminaria japonica (J. E. Areschoug – Japón) is now regarded as a synonym of Saccharina japonica and Laminaria saccharina is now classified as Saccharina latissima. Laminaria arrived in China from Hokkaido, Japan in the late 1920s. Once in China, Laminaria was cultivated on a much larger industrial scale. The rocky shores at Dalian, the northern coast of the Yellow Sea, along with its cold waters provided excellent growing conditions for these species. Laminaria was harvested for food and 1949 yielded 40.3 metric tons of dry weight. Laminaria need cold water to survive and can only live above 36° N latitude. In 1949, the Chinese started to commercially grow laminaria as a crop. This increased the production of dry weight to 6,200 metric tons. Farming laminaria is still a large production for China. However, since the 1980s production has dropped due to new mariculture technology . Laminaria is generally farmed using the floating raft method, in which young laminaria sporophytes are attached to submerged ropes. These ropes are then attached to floating rafts. Laminaria is found in colder ocean waters, such as arctic regions. Preferring to stay in regions where there are rocky shores, this allows the laminaria to attach. Due to the height of the Laminaria, they provide protection for creatures that the open ocean does not often give. Invertebrates are just one of the organisms that live among the algae. Sea snails and other invertebrates feed on the blades (leaves) of the laminaria. Other organisms, such as sea urchins, feed on the holdfasts, which can kill the algae. red sea urchins, found on the North America Pacific Coast, can decimate kelp, including Laminaria,, if the urchins are not managed by sea otters.  Laminaria expresses a haplo-diplophasic life history, in which it alternates from a macroscopic thallic sporophyte structure, consisting of the holdfast, a stipe, and the blades, to a filamentous, microscopic gametophyte. The sporophyte structure of laminaria can grow to 7 metres (23 ft), which is large in comparison to other algae, but still smaller than the giant kelps such as Macrocystis and Nereocystis, which can grow up to 40–50 metres (130–160 ft). On the other hand, the gametophyte structure is no more than a few millimeters in length. In opposition to the gametophyte phase, which only consists of one type of tissue, the more complex sporophyte phase is made up of different types of tissue. One of these tissues includes a sieve-like element which translocates photoassimilates . These structures are very similar to mesophyll cells found in higher plant leaves.