Editing Algae (section)

===Morphology===
[[File:Kelp-forest-Monterey.jpg|thumb|upright|The [[kelp forest]] exhibit at the Monterey Bay Aquarium: A three-dimensional, multicellular thallus]]

A range of algal [[Morphology (biology)|morphologies]] is exhibited, and [[Convergent evolution|convergence]] of features in unrelated groups is common. The only groups to exhibit three-dimensional multicellular [[Thallus|thalli]] are the [[Red algae|reds]] and [[Brown algae|browns]], and some [[Chlorophyta|chlorophytes]].<ref name="Xiao-2004">{{cite journal |last1=Xiao |first1=S. |last2=Knoll |first2=A. H. |last3=Yuan |first3=X. |last4=Pueschel |first4=C. M. |year=2004 |title=Phosphatized multicellular algae in the Neoproterozoic Doushantuo Formation, China, and the early evolution of florideophyte red algae |journal=American Journal of Botany |volume=91 |issue=2 |pages=214–227 |doi=10.3732/ajb.91.2.214 |pmid=21653378 |doi-access=free }}</ref> Apical growth is constrained to subsets of these groups: the [[Florideophyceae|florideophyte]] reds, various browns, and the charophytes.<ref name="Xiao-2004" /> The form of charophytes is quite different from those of reds and browns, because they have distinct nodes, separated by internode 'stems'; whorls of branches reminiscent of the [[horsetail]]s occur at the nodes.<ref name="Xiao-2004" /> [[Conceptacle]]s are another [[polyphyletic]] trait; they appear in the [[coralline algae]] and the [[Hildenbrandiales]], as well as the browns.<ref name="Xiao-2004" />

Most of the simpler algae are unicellular [[flagellate]]s or [[amoeboid]]s, but colonial and nonmotile forms have developed independently among several of the groups. Some of the more common organizational levels, more than one of which may occur in the [[biological life cycle|lifecycle]] of a species, are
* [[Colony (biology)|Colonial]]: small, regular groups of motile cells
* Capsoid: individual non-motile cells embedded in [[mucilage]]
* Coccoid: individual non-motile cells with cell walls
* Palmelloid: nonmotile cells embedded in mucilage
* Filamentous: a string of connected nonmotile cells, sometimes branching
* Parenchymatous: cells forming a thallus with partial differentiation of tissues

In three lines, even higher levels of organization have been reached, with full tissue differentiation. These are the brown algae,<ref>{{cite web |url= http://www.ucmp.berkeley.edu/chromista/phaeophyta.html |title=Introduction to the Phaeophyta: Kelps and brown "Algae" |first=Ben |last=Waggoner |publisher=University of California Museum of Palaeontology (UCMP) |date=1994–2008 |access-date=19 December 2008 |archive-url= https://web.archive.org/web/20081221171218/http://www.ucmp.berkeley.edu/chromista/phaeophyta.html |archive-date=21 December 2008 |url-status=dead}}</ref>—some of which may reach 50&nbsp;m in length ([[kelp]]s)<ref>{{cite book |last=Thomas |first=D. N. |title=Seaweeds |date=2002 |publisher=The Natural History Museum |location=London |isbn=978-0-565-09175-0}}</ref>—the red algae,<ref>{{cite web |url= http://www.ucmp.berkeley.edu/protista/rhodophyta.html |title=Introduction to the Rhodophyta, the red 'algae' |first=Ben |last=Waggoner |publisher=University of California Museum of Palaeontology (UCMP) |date=1994–2008 |access-date=19 December 2008 |archive-url= https://web.archive.org/web/20081218211021/http://www.ucmp.berkeley.edu/protista/rhodophyta.html |archive-date=18 December 2008 |url-status=dead}}</ref> and the green algae.<ref>{{cite web |url= http://www.ucmp.berkeley.edu/greenalgae/greenalgae.html |title=Introduction to the Green Algae |work=berkeley.edu |url-status=dead |archive-url= https://web.archive.org/web/20070213103838/http://www.ucmp.berkeley.edu/greenalgae/greenalgae.html |archive-date=13 February 2007 |access-date=15 February 2007}}</ref> The most complex forms are found among the charophyte algae (see [[Charales]] and [[Charophyta]]), in a lineage that eventually led to the higher land plants. The innovation that defines these nonalgal plants is the presence of female reproductive organs with protective cell layers that protect the zygote and developing embryo. Hence, the land plants are referred to as the [[Embryophyte]]s.

====Turfs====
The term algal turf is commonly used but poorly defined. Algal turfs are thick, carpet-like beds of seaweed that retain [[sediment]] and compete with foundation species like [[coral reef|corals]] and [[kelp forest#Kelp|kelps]], and they are usually less than 15&nbsp;cm tall. Such a turf may consist of one or more species, and will generally cover an area in the order of a square metre or more. Some common characteristics are listed:<ref name="Connell-2014" >{{cite journal|url=https://www.researchgate.net/publication/285992380 |last1=Connell |first1=Sean |last2=Foster |first2=M.S. |last3=Airoldi |first3=Laura |date=9 January 2014 |title= What are algal turfs? Towards a better description of turfs |journal=Marine Ecology Progress Series |volume=495 |pages=299–307 |doi=10.3354/meps10513 |bibcode=2014MEPS..495..299C |doi-access=free }}</ref>
* Algae that form aggregations that have been described as turfs include diatoms, cyanobacteria, chlorophytes, phaeophytes and rhodophytes. Turfs are often composed of numerous species at a wide range of spatial scales, but monospecific turfs are frequently reported.<ref name="Connell-2014" />
* Turfs can be morphologically highly variable over geographic scales and even within species on local scales and can be difficult to identify in terms of the constituent species.<ref name="Connell-2014" />
* Turfs have been defined as short algae, but this has been used to describe height ranges from less than 0.5&nbsp;cm to more than 10&nbsp;cm. In some regions, the descriptions approached heights which might be described as canopies (20 to 30&nbsp;cm).<ref name="Connell-2014" />