Column: Nature Notes - KELP FORESTS

In ideal conditions where water is cold and rich in nutrients, kelp can grow to significant heights of up to 
80 metres and also can grow very rapidly up to 45 cm in a single day.

Kelp superficially resemble plants but are actually a form of algae. Kelp absorbs nutrients through all parts of its tissues and unlike plants, does not have a vascular system. There are around 30 species of kelp, and a variety of kelp species may be found within one forest.

Kelp is anchored to the seafloor by a holdfast, stemlike structure called a stipe. Stipes are flexible, allowing the kelp to sway with ocean movements; leaf-like structures called blades grow from the stipes; gas filled bladders (pneumatocysts) provide buoyancy to keep the blades exposed to sunlight. Kelp forests are restricted to shallow, relatively clear, coastal waters to facilitate photosynthesis - this process uses sunlight to convert carbon dioxide to sugar which can be used for energy, with oxygen produced as a by product.

Reproduction is a two-stage life cycle which alternates generations, one producing sexually and one producing asexually. The large mature kelp fronds are the asexual form called sporophites. They release spores which germinate into male and female gametophytes, which are very small sexually reproducing kelp. These individuals produce gametes (sperm or eggs). When fertilisation occurs, a zygote is produced, and this develops into a sporophyte. The juvenile sporophyte finds a place on the seafloor and attaches, then grows towards the sea surface, in time developing into a mature specimen.

Kelp is a dynamic, resilient, often under-valued ecosystem influenced by natural conditions such as storms and sea urchin populations However, human impacts of overharvesting, fishing, loss of keystone predators, pollution, boat damage and climate change are negatively affecting kelp forests globally.



Kelp are a cold water species, and climate change brings warmer waters, acidification, and low nutrients, and extends the range of herbivorous predators, particularly sea urchins who devour kelp. Giant kelp forests are now considered endangered. Research published recently has found that 95 per cent of the giant kelp forests of Tasmania's east coast have disappeared, with the primary driver being the extension of the East Australian

Current into Tasmanian waters bringing higher sea temperatures and nutrient poor water.