Biology Reference
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deep as 268 m in the Bahamas (Littler et al . 1985 , 1986 ). On Cura¸ao sparse algal
turfs reach their lower limit around 65 m, where PAR levels are as low as 1% of that
found at the surface (Van den Hoek et al . 1978 ). Green macroalgae generally are
most common in shallow waters, but have been found forming entire communities
consisting of Udotea, Caulerpa , and Halimeda species at depths of 25 m on Saba
Bank (Lesser Netherlands Antilles) (Littler et al . 2010a ) as well as Johnson-
sealinkia profunda colonies found at the extreme depth of 200 m in the Bahamas
(Littler and Littler 1988 ). In addition, the lack of a conspicuous seasonal cycle in
photoperiod in the tropics compared to mid and high latitudes provides a relatively
constant supply of PAR throughout the year.
Although ultraviolet radiation (UVR) levels are high in the tropics, studies
focused on its impact on macroalgae have for the most part been limited to polar
and temperate seaweeds due to ozone depletion in these regions (Bischof et al .
2006 ; see also Chap. 20 by Bischof and Steinhoff). Recently, Figueroa et al . ( 2009 )
showed that seaweeds from the Red Sea show dynamic photoinhibition as an
efficient mechanism of acclimation to high PAR as well as UV irradiance levels.
This is not unique to tropical seaweeds but has been shown for other seaweeds in
high light exposed environments (Figueroa et al . 1997 ). A recent investigation of
tropical marine macroalgae collected from Belize at depths of 0.3-26 m depths
showed that UVR caused an additional decrease of photosynthetic performance
during high light stress which varied according to species, depth of growth, and UV
penetration at the site of collection (Hanelt and Roleda 2009 ; see also Chap. 1 by
Hanelt and Figueroa). However, this same study also provided evidence that UVB
radiation may not only cause negative effects on cellular processes of seaweeds but
may also support recovery processes in high UVR adapted seaweeds (Hanelt and
Roleda 2009 ).
16.3 Vegetation Structure
16.3.1 Succession
Succession patterns depend on the characteristics of vacant space, bottom-up
availability of nutrients, and top-down grazing characteristics. Many studies have
documented the recovery of coral reef systems after storms and hurricanes and the
succession of algae during this process as well as the experimental succession on
settlement plates. In general, there is first a dominance of simple turf like green and
brown filamentous seaweeds, a midsuccessional stage with thin and finely branched
red filamentous seaweeds, and a late stage dominated by coarsely branched and
thick canopy-forming seaweeds. The 37-year history of the Tiahura Outer Reef
Sector (Moorea) constitutes one of the longest records of coral reef dynamics
(Adjeroud et al . 2009 ). Between 1991 and 1994, the decline in coral cover was
accompanied by colonization by turf algae (16.2
5.5% in 1991 to 48.5
2.5%
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