Difference between revisions of "Portal:Marine Biodiversity/Selected Article"

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==Effects of fisheries on European marine biodiversity==
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==Diversity and classification of marine benthic algae==
  
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[[Image:food web competion.jpg|thumb|250px|right|Food-web competition: top predators (such as marine mammals) and fisheries may not directly compete (because they consume different species) but could indirectly affected by fisheries, because of limits on the primary productivity available to support the two groups. SOURCE: Reprinted from: Trites A.W., Christensen V. & Pauly D. (1997). Competition between fisheries and marine mammals for prey and primary production in the Pacific Ocean. ''Journal of Northwestern Atlantic Fishery Science'' 22: 173–187.]]
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[[image:See weed on a rocky outcrop.JPG|thumb|right|350px|caption|Algal canopy at low tide on the west coast of Irish Sea. Photo © EcoServe]]
  
 
 
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Fishing is the most widespread human exploitative activity in the marine environment. Pauly and Christenen (1995) estimated that over 20 % of the [[primary production]] is required to sustain fisheries in many intensively fished coastal ecosystems.<ref name="Pauly1995">Pauly, D. & Christensen, V.(1995). Primary production required to sustain global fisheries. ''Nature'' 374: 255-257.</ref>
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Chlorophyllian photosynthesis is responible of almost all primary production at global
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level and represents the most fundamental process for the support and maintenance
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of life on our planet. Organisms performing photosynthesis occur in every habitat in
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which sunlight is available. Whereas vascular plants are largely responsible of
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photosynthesis on land, in aquatic habitats this process is mainly perfomed by the
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wide and heterogeneous complex of organisms called algae.
  
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In the widest sense, algae are defined as oxygenic photosynthesizers other than
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Fishing has a number of direct effects on marine ecosystems because it is responsible for increasing mortality of target and [[by-catch]] species; an important physical impact on the habitat of benthic organisms is caused by [http://en.wikipedia.org/wiki/Bottom_trawling bottom trawling]. The direct effects of fishing have indirect implications for other species as well. Fisheries remove prey that [[piscivorous]] fishes, birds and mammals would otherwise consume, or may remove predators that would otherwise control prey populations. Reductions in the density of some species may affect competitive interactions and result in the proliferation of non-target species. The activities of fisheries also favor scavengers, they obtain more food by the discarded by-catch and because a range of species are killed, but not retained by towed gears.<ref name="Jennings1998">Jennings, S.& Kaiser, M. (1998). The effects of fishing on marine ecosystems. ''Adv. Mar. Biol.'' 34: 201-352.</ref>. [[Effects of fisheries on European marine biodiversity|'''More...''']]
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embryophyte land plants (Cavalier-Smith, 2007<ref name = Cavalier> Cavalier-Smith, T. (2007). Evolution and relationships of algae: major branches of the tree of life. In Unravelling the algae: the past, present and future of algal systematics, eds J. Brodie and J. Lewis, pp 21-55. CRC Press, Boca Raton, London and New York. </ref>). In recent years our knowledge of these organisms has greatly advanced, thanks to new types of data (mainly electron microscopy observations and DNA sequence data). Based on these data, we know now that algae represent an artificial and unnatural agglomeration of very different
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organisms, sharing the only common characteristic of living in aquatic habitats. Algae
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living in the sea are typically subdivided in plankton (the complex of microscopic
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algae not visible with unaided eye, which live floating in the water) and benthos (the
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collectivity of the algae that live attached to the sea bottom). [[Diversity and classification of marine benthic algae|'''More...''']]

Revision as of 11:44, 31 July 2009

Diversity and classification of marine benthic algae

Algal canopy at low tide on the west coast of Irish Sea. Photo © EcoServe


Chlorophyllian photosynthesis is responible of almost all primary production at global level and represents the most fundamental process for the support and maintenance of life on our planet. Organisms performing photosynthesis occur in every habitat in which sunlight is available. Whereas vascular plants are largely responsible of photosynthesis on land, in aquatic habitats this process is mainly perfomed by the wide and heterogeneous complex of organisms called algae.

In the widest sense, algae are defined as oxygenic photosynthesizers other than embryophyte land plants (Cavalier-Smith, 2007[1]). In recent years our knowledge of these organisms has greatly advanced, thanks to new types of data (mainly electron microscopy observations and DNA sequence data). Based on these data, we know now that algae represent an artificial and unnatural agglomeration of very different organisms, sharing the only common characteristic of living in aquatic habitats. Algae living in the sea are typically subdivided in plankton (the complex of microscopic algae not visible with unaided eye, which live floating in the water) and benthos (the

collectivity of the algae that live attached to the sea bottom). More...
  1. ↑ Cavalier-Smith, T. (2007). Evolution and relationships of algae: major branches of the tree of life. In Unravelling the algae: the past, present and future of algal systematics, eds J. Brodie and J. Lewis, pp 21-55. CRC Press, Boca Raton, London and New York.
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